f?N: * ^ M ` ^

INTERNATIONAL SEMINAR ON DISINFECTION
WITH MIXED OXIDANTS GENERATED ONSITE
PAHO
LIMA, PERU
DECEMBER
5 - 1 2 1987
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THE JOHNS HOPKINS
v.f
UNIVERSITY
SCHOOL OF MEDICINE
rlcasc mldicss reply tare of
Dt:rA R 7 MEN T OF PI.OIA IRICS
Division of Infectious
Till: JOHNS HOrKINS 1IOSPITA L
RAUIMORE.
MARYIAND21205
Phrases
Baltimore, June 29 , 1987
Doctor
•
DONALD S. SHARP
Associate Director
Water Supply and Sanitation
Health Sciences Division
International Development Research Center (IDRC)
P.O. Box 8500
Ottawa, Canada
KIG - 3H9
Dear Doctor Sharp:
Thank you f o r sending me the g u i d e l i n e s and a p p l i c a t i o n forms for
r e s e a r c h s u p p o r t and general i n f o r m a t i o n about IDRC. We appreciate
your encouragement and support in our research e f f o r t s .
As I t o l d you on the phone, P r o f e s s o r M a r i a Yolanda Ramirez and
I , have d e c i d e d t o c o n t i n u e w i t h t h e r e s e a r c h a c t i v i t i e s and the
m u l t i d i s c i p l i n a r y group that we established a few years ago in C a l i ,
Colombia, w h i c h i s based at t h e U n i v e r s i t y o f V a l l e . Under our
leadership, the group involves research workers from the School of
E n g i n e e r i n g and t h e School o f M e d i c i n e and H e a l t h Sciences at the
U n i v e r s i t y , as w e l l as from the Cali Regional Health U n i t , which is
t h e branch o f t h e M i n i s t r y of H e a l t h i n C a l i . We are i n t h e process
of f o r m a l i z i n g a j o i n t program between the U n i v e r s i t y of Valle and
the Johns Hopkins U n i v e r s i t y , f o l l o w i n g our research experience f o r
the l a s t two years at Johns Hopkins.
We are proposing a whole package of i n v e s t i g a t i o n s in the area of
d i a r r h e a l d i s e a s e s and e n v i r o n m e n t a l h e a l t h , to be accomplished in
the next f i v e years. Our plan consists o f the f o l l o w i n g s t u d i e s :
1. The f i r s t study w i l l evaluate an oxidant generator which the
Pan American H e a l t h O r g a n i z a t i o n (PAHO) i s w i l l i n g t o i n t r o d u c e i n
s m a l l c o m m u n i t i e s o f d e v e l o p i n g c o u n t r i e s . The PAHO d e v i c e , which
d i s i n f e c t s b a c t e r i a , v i r u s e s and p a r a s i t e s , should improve the
q u a l i t y of the water supplies of such populations, which do not have
access to a r e a l aqueduct.
net. \\This study w i l l be submitted f o r funding
t o PAHO and w i l l be conducted in C a l i , Colombia.
2.
The second study w i l l e v a l u a t e two s i m p l e methods f o r
i m p r o v i n g w a t e r q u a l i t y , and t h e r e b y i m p r o v i n g c h i l d h e a l t h , i n
periurban communities i n C a l i , Colombia.
We w i l l evaluate the d i s i n f e c t i o n potential of a simple slow sand
f i l t r a t i o n system and the on s i t e o x i d a n t g e n e r a t o r d e v i c e by
themselves and both t o g e t h e r a g a i n s t a n a t u r a l n o n - t r e a t e d v/ater
supply. Water s u p p l i e s w i l l be examined f o r m i c r o b i o l o g i c a l and
p a r a s i t o l o g i c a l q u a l i t y . P a r a l l e l to the water i n t e r v e n t i o n s , we w i l l
measure the health impact of these water treatments, among c h i l d r e n
from 6 t o 18 months o f age. Fecal c o n t a m i n a t i o n i n d i c a t o r s and
s p e c i f i c pathogens w i l l be q u a n t i f i e d at the stages o f i n g e s t i o n ,
i n f e c t i o n and e x c r e t i o n . D i a r r h e a l disease r a t e s w i l l a l s o be
measured. This is the study t o be submitted to IDRC f o r funding.
Besides our m u l t i d i s c i p l i n a r y group, which i n v o l v e s , s a n i t a r y
engineers,
microbiologists,
virologists,
immunologists,
epidemiologists and p e d i a t r i c i a n s , we w i l l have two consultants : Dr.
V i n c e n t P. O l i v i e r i , from t h e Environmental H e a l t h E n g i n e e r i n g
D i v i s i o n , and Dr. S t e v e n A. E s r e y , f r o m t h e D e p a r t m e n t o f
I n t e r n a t i o n a l Health, The Johns Hopkins University School of Hygiene
and Public Health.
In about two weeks I w i l l send you a pre-proposal describing the
two- year s t u d y , which we p l a n t o s t a r t by June 1988. The f i r s t s i x
months w i l l be d e d i c a t e d t o p r e l i m i n a r y s t u d i e s , then another s i x
months f o r e s t a b l i s h i n g t h e i n t e r v e n t i o n s , p l u s s i x months o f
e v a l u a t i o n and s i x months f o r data a n a l y s i s and p u b l i c a t i o n . The
p r o j e c t w i l l be performed i n periurban communities t h a t do not have
access t o t h e C a l i ' s main w a t e r supply or aqueduct. Our r e s e a r c h
group has been working i n four o f these communities and a summary of
the s t u d i e s , i n f i n a l form, w i l l be submitted f o r p u b l i c a t i o n in the
PAHO B u l l e t i n ,
3. A t h i r d study w i l l focus on behavioral changes as preventive
measures o f the Acute D i a r r h e a l Diseases Syndrome. This p a r t i c u l a r
p r o j e c t w i l l deal w i t h i n t e r v e n t i o n s r e l a t e d t o e x c r e t a d i s p o s a l ,
personal hygiene and food hygiene. We are considering several sources
of funding f o r t h i s study.
4. This w i l l be a v i r o l o g i c a l , b a c t e r i o l o g i c a l and immunological
study which w i l l include epidemiologic s u r v e i l l a n c e , d i s t r i b u t i o n ,
a t t a c k r a t e s , f l u c t u a t i o n s e t c , o f the l e a d i n g pathogens o f the
e n t e r i c t r a c t i n some s p e c i f i c areas of C a l i , w i t h emphasis on
Rotavirus. Immunological studies of the community from the point of
view of the respdnse to Rotavirus i n f e c t i o n plus the i n t r o d u c t i o n and
development o f r'apid d i a g n o s t i c l a b o r a t o r y t e c h n i q u e s and some
p r e l i m i n a r y studies on the molecular biology of these v i r u s e s , w i l l
also be considered. \ This p r o j e c t w i l l be submitted to "Colciencias",
the main Colombian governmental i n s t i t u t i o n for research funding.
5. Based i n the p r e v i o u s study we w i l l p e r f o r m a R o t a v i r u s
vaccine t r i a l i n C a l i . For such a study we may go t o NIH
for
funding or possibly to WHO.
As you can see, we want to have all research pieces together, in
order to evaluate these different interventions as preventive
measures of the Acute Diarrheal Disease Syndrome, under the
ecological parameters of our developing country.
Finally, I plan to contact your representative in Bogota, before
sending you the pre-proposal, in order to follow the appropriate
channels. Thank you in advance for your patience and reviewing this
outline. I would appreciate any suggestions or comments you may have
at this time.
Sincerely yours,
/c.c.
c.c.
c.c.
c.c.
Prof.
Dr.
Dr.
Dr.
\
Maria Yolanda Ramirez
Vincent P. Olivieri
Steven A. Esrey
Silvio Gomez J.
WORKING
«'
DRAFT
DISINFECTION WITH MIXED OXIDANT GASES
G E N E R A T E D ON SITE ( M O G G O D )
A Progress Report
of
the P A H O D e m o n s t r a t i o n - D e v e l o p m e n t
December
1987
Project
v
()
/7p JfrLc<4^
SYNOPSIS
9
m
In 1982 T h e P a n A m e r i c a n H e a l t h O r g a n i z a t i o n ( P A H O ) h e g a n
p r o m o t i n g the d e v e l o p m e n t of t e c h n o l o g y for o n - s i t e g e n e r a t i o n of
mixed o x i d a n t s for the d i s i n f e c t i o n of d r i n k i n g w a t e r s u p p l i e s for
smell a n d / o r r e m o t e c o m m u n i t i e s in L a t i n A m e r i c a and the C a r i b b e a n .
For b r e v i t y t h i s t e c h n o l o g y w a s g i v e n the a c r o n y m of M O G G O D , the term
w h i c h will b e u s e d t h r o u g h o u t t h e r e m a i n d e r o f t h e a r t i c l e The
f u n d a m e n t a l r e a s o n for P A H O ' s i n t e r e s t in d e v e l o p m e n t of a n e w
d i s i n f e c t i o n t e c h n o l o g y w h e n so m a n y c o n v e n t i o n a l m e t h o d s and
" a p p r o p r i a t e t e c h n o l o g i e s " a l r e a d y e x i s t e d w a s for the s i m p l e
statistical
f a c t that m o r e t h a n 757. of all d i s i n f e c t i o n f a c i l i t i e s
in L a t i n A m e r i c a and t h e C a r i b b e a n h a v e f a i l e d to p r o v i d e c o n t i n u o u s
and a d e q u a t e d i s i n f e c t i o n in s p i t e of m o r e t h a n 2 0 y e a r s of e f f o r t s
to d e v e l o p h u m a n r e s o u r c e s , i n s t i t u t i o n s and s u p p o r t i n g
infrastructure.
T h e b a s i c c o n c e p t b e h i n d t h i s i n i t i a t i v e is to u s e
high level t e c h n o l o g y to d e v e l o p s i m p l e , p r a c t i c a l but e f f e c t i v e
d i s i n f e c t i o n m e t h o d s w h i c h a r e t a r g e t e d at r e m o v i n g the r e s t r i c t i o n s
and p r o b l e m s p e c u l i a r to L a t i n A m e r i c a t h a t h a v e p r e v e n t e d
conventional disinfection from being carried o u t .
In D e c e m b e r 1986 P A H O w i t h a 20'/. c o n t r i b u t i o n from U N D P i n i t i a t e d
the first p h a s e of a d e m o n s t r a t i o n p r o j e c t to i n t r o d u c e a g e n c i e s and
i n s t i t u t i o n s of P A H O m e m b e r c o u n t r i e s to the M O G G O D c o n c e p t and to
e n l i s t their s u p p o r t in t h e d e v e l o p m e n t o f M O G G O D t e c h n o l o g y .
It
included the p u r c h a s e of M O G G O D p r o t o t y p e s a l o n g w i t h their s h i p m e n t
to p a r t i c i p a t i n g c o u n t r i e s in L a t i n A m e r i c a and t h e C a r i b b e a n for
l a b o r a t o r y as well as f i e l d t e s t i n g u n d e r the a c t u a l c o n d i t i o n s w h i c h
h a v e led to t h e f a i l u r e o f e x i s t i n g c o n v e n t i o n a l m e t h o d s of
disinfection.
It is a n t i c i p a t e d that the o p e r a t i o n a l e x p e r i e n c e
which is u n d e r w a y will n o t o n l y f a m i l i a r i z e t h e w a t e r supply s e c t o r
with M O G G O D t e c h n o l o g y b u t also will lead to a c c e l e r a t e d i m p r o v e m e n t s
and a p p l i c a t i o n of the d e v i c e s .
The a m b i t i o u s o b j e c t i v e of d e v e l o p i n g i n n o v a t i v e d i s i n f e c t i o n
t e c h n o l o g y in the c o n t e x t of L a t i n A m e r i c a a p p e a r s p o s s i b l e in light
of the i n c r e a s e d s c i e n t i f i c k n o w l e d g e and m a n y t e c h n i c a l a d v a n c e m e n t s
m a d e in r e l a t e d a r e a s o v e r the p r e v i o u s d e c a d e .
The project's rapid
f e e d b a c k of o p e r a t i o n a l e x p e r i e n c e f r o m t h e u s e r s to the d e v e l o p e r s
h a s a l r e a d y r e s u l t e d in a c o n s i d e r a b l e n u m b e r o f s i g n i f i c a n t
i m p r o v e m e n t s in d e s i g n , m e t h o d o l o g y and t e c h n o l o g i c a l u n d e r s t a n d i n g .
M O G G O D d i s i n f e c t i o n to d a t e h a s b e e n a\t least a s e f f e c t i v e a s
c h l o r i n e in b o t h the f i e l d and the l a b o r a t o r y .
At this e a r l y s t a g e
of the p r o j e c t the r e s u l t s h a v e b e e n "very e n c o u r a g i n g and d e f i n i t e l y
- 8 -
merit
continuation
BACKGROUND
of
AND P R O J E C T
the
effort.
JUSTIFICATION:
A l t h o u g h m a n y of t h e small towms and c o m m u n i t i e s of L a t i n A m e r i c a
a n d t h e C a r i b b e a n h a v e b e e n served with c o m m u n i t y w a t e r s y s t e m s and
m o s t n a t i o n a l p l a n s a i m at increasing t h e w a t e r s u p p l y c o v e r a g e in
s m a l l and rural c o m m u n i t i e s , the d i s i n f e c t i o n of t h a t w a t e r h a s b e e n
n e i t h e r a d e q u a t e nor r e l i a b l e ; more o f t e n t h a n not it is not e v e n
carried out.
In P A H O ' S w o r k s h o p in May 1 9 8 ^ for the i n t r o d u c t i o n of
the n e w W H O G u i d e l i n e s for Drinking W a t e r Q u a l i t y a p a r t i c i p a n t
s u r v e y i n d i c a t e d t h a t m o r e than 75*/. o f the w a t e r s y s t e m s in L a t i n
A m e r i c a and the C a r i b b e a n w e r e either i n a d e q u a t e l y d i s i n f e c t e d or not
d i s i n f e c t e d at a l l .
S u b s e q u e n t s t u d i e s and i n v e s t i g a t i o n s i n d i c a t e a
s o m e w h a t h i g h e r p e r c e n t a g e of f a i l u r e .
T h i s is o n e of the m o s t s e r i o u s p r o b l e m s a f f e c t i n g the h e a l t h of
the r e s i d e n t s of s m a l l t o w n s , rural a r e a s and m a r g i n a l u r b a n a r e a s .
T h e i m p o r t a n c e of w a t e r d i s i n f e c t i o n
h a s b e e n p r o v e n in b o t h theory
and p r a c t i c e .
It is a f u n d a m e n t a l p u b l i c h e a l t h m e a s u r e and w h e r e v e r
it h a s b e e n c a r r i e d o u t r e l i a b l y and a d e q u a t e l y h a s a s s u r e d h e a l t h
b e n e f i t s for the u s e r s of the water s u p p l y .
T h e r e are
m o r e that 2 0
d i s e a s e s r e l a t e d to d r i n k i n g water s u p p l y . All of t h e m a r e
d e b i l i t a t i n g and s o m e a r e d e a d l y , p l a c i n g a t e r r i b l e h a n d i c a p and
e c o n o m i c b u r d e n o n e v e r y o n e but p a r t i c u l a r l y u p o n t h e p o o r p e o p l e who
least c a n a f f o r d i t .
T h e most s e r i o u s a n d n u m e r o u s of t h e s e d i s e a s e s
c a n to a very l a r g e e x t e n t be p r e v e n t e d t h r o u g h a d e q u a t e
di si n f e c t i o n .
T h e r e h a v e b e e n n u m e r o u s s t u d i e s o v e r t h e p a s t 5 0 y e a r s o n the
b e n e f i t s of d i s i n f e c t i o n but two of the m o s t r e c e n t are
of p a r t i c u l a r
s i g n i f i c a n c e to t h i s p r o p o s a l . In their " S t u d i e s o f D i a r r h e a in
G u i n d i o C o l o m b i a : P r o b l e m s Related to W a t e r T r e a t m e n t " D o c t o r s David
B e r s c h and M a r g a r i t a O s o r i o disclosed an i n v e r s e r e l a t i o n s h i p b e t w e e n
the level of r e s i d u a l c h l o r i n e and the r a t e s o f d i a r r h e a a m o n g
c h i l d r e n u n d e r 5 y e a r s of a g e .
In a p i l o t p r o j e c t in 1981 f i n a n c e d
by U N I C E F and c o n d u c t e d by the I n s t i t u t e o f C h i l d H e a l t h i^n C a l c u t t a
India in W e s t B e n g a l India 3 0 0 f a m i l i e s r e c e i v e d d i s i n f e c t i o n of
drinking water and another 300 families did n o t .
All o t h e r f a c t o r s
w e r e d e t e r m i n e d to b e e s s e n t i a l l y the s a m e .
Over a nine month period
t h e r e w a s an 807. r e d u c t i o n in the i n c i d e n c e of d i a r r h e a l d i s e a s e
a m o n g the c h i l d r e n r e c e i v i n g the d i s i n f e c t e d w a t e r and o n l y a 5'/.
r e d u c t i o n in t h e c h i l d r e n which did n o t r e c e i v e d i s i n f e c t e d w a t e r .
In s i t u a t i o n s w h e r e w a t e r is the p r e d o m i n a n t v e h i c l e for the
t r a n s m i s s i o n of T y p h o i d , P a r a t y p h o i d , C h o l e r a , C a m p y l o b a c t e r ,
R o t o v i r u s , H e p a t i t u s , D r a c o n t i a s i s or G i a r d i a s i s , a d e q u a t e l e v e l s of
d i s i n f e c t a n t and a d e q u a t e c o n t a c t t i m e w i l l r e s u l t in r e d u c e d
i n c i d e n c e of d i s e a s e .
The h e a l t h b e n e f i t s o f m o r e r e l i a b l e , simpler
and lower c o s t d i s i n f e c t i o n are p a t e n t l y o b v i o u s .
C A U S E S OF D I S I N F E C T I O N
FAILURE
To r e s o l v e t h e p r o b l e m of w i d e s p r e a d f a i l u r e o f d i s i n f e c t i o n in
L a t i n A m e r i c a and t h e C a r i b b e a n it is f i r s t n e c e s s a r y to i d e n t i f y and
u n d e r s t a n d the n a t u r e of the c a u s e s b e h i n d t h e f a i l u r e .
S t u d i e s and
- 3 -
investigations*
have disclosed a number
for f a i l u r e to d i s i n f e c t w h i c h a r e ;
of c o m m o n l y
cited
reasons
1. U n d e p e n d a b l e or u n a v a i l a b l e s u p p l y of c h e m i c a l s .
2. Unavailable spare parts.
3. O p e r a t i o n a l r e q u i r e m e n t s too c o m p l e x for
local o p e r a t o r s to
carry o u t .
A. R e p a i r of e q u i p m e n t too c o m p l e x for local o p e r a t o r s to m a k e .
5. I n a d e q u a t e i n f r a s t r u c t u r e to s u p p o r t the p u r c h a s e * t r a n s p o r t s
and s t o r a g e of c h e m i c a l s , s p a r e p a r t s and s u p p l i e s .
6. User d i s s a t i s f a c t i o n w i t h w i d e l y v a r y i n g c h l o r i n e l e v e l s .
7 . D i f f i c u l t y i n v o l v e d in local s t o r a g e , h a n d l i n g , m i x i n g and
d o s i n g of c h e m i c a l s .
8. Insufficient equipment d u r a b i l i t y .
9. I n s u f f i c i e n t o p e r a t o r t r a i n i n g and e x p e r i e n c e as well as
inadequate basic education.
10. Inadequate safety c o n s i d e r a t i o n s .
11. F o r e i g n e x c h a n g e r e s t r i c t i o n s .
In a l m o s t all s p e c i f i c i n s t a n c e s t h e r e are m u l t i p l e u n d e r l y i n g
c a u s e s for the f a i l u r e to d i s i n f e c t ; s o m e of t h e c a u s e s o p e r a t e in
s e r i e s and o t h e r s o p e r a t e in p a r a l l e l and they m u s t b e r e s o l v e d
a c c o r d i n g l y to o b t a i n a lasting s o l u t i o n .
A v a r i e t y of a p p r o a c h e s
h a v e b e e n t a k e n in the p a s t to s o l v e t h i s d i l e m m a i n c l u d i n g
i n s t i t u t i o n a l and h u m a n r e s o u r c e d e v e l o p m e n t .
The results have been
less than s a t i s f a c t o r y w i t h an i n c r e a s e of o n l y a f e w p e r c e n t in t h e
water s y s t e m s a d e q u a t e l y d i s i n f e c t e d o v e r the last 2 0 y e a r s .
A
number of a l t e r n a t i v e t e c h n o l o g i e s s u c h as o z o n a t i o n , u l t r a v i o l e t
light, halogenated r e s i n s , radiation, iodination, chlorine dioxide,
c h l o r a m i n e s , and a p p r o p r i a t e t e c h n o l o g i e s for h y p o c h 1 o r i n a t i o n h a v e
b e e n i n t r o d u c e d to o v e r c o m e the p r o b l e m but they h a v e n ' t r e a l l y
c i r c u m v e n t e d the m a j o r c a u s e s of t h e p r o b l e m .
Some have even added
to them.
U n f o r t u n a t e l y the g r e a t m a j o r i t y of w o r k and a d v a n c e m e n t s
in d i s i n f e c t i o n t e c h n o l o g y h a v e b e e n aimed p r i m a r i l y at s o l v i n g
p r o b l e m s e n c o u n t e r e d in the h i g h l y d e v e l o p e d and i n d u s t r i a l i z e d
countries.
T h e y h a v e n o t b e e n d i r e c t e d t o w a r d s s o l u t i o n of t h e
s p e c i f i c p r o b l e m s and c o n s i d e r a b l y d i f f e r e n t p r o b l e m s of d e v e l o p i n g
countr i e s .
F O R M U L A T I O N OF T H E M 0 G G 0 D
CONCEPT:
B e c a u s e no s i n g l e c o n v e n t i o n a l m e t h o d of d i s i n f e c t i o n s e e m e d to
o v e r c o m e a s u f f i c i e n t n u m b e r of t h e s e c a u s e s , v a r i o u s c o m b i n a t i o n s of
them w e r e e x p l o r e d .
T h e s i m p l e c o m b i n a t i o n of m e t h o d s u s u a l l y
r e s u l t e d in m u c h m o r e c o m p l e x o p e r a t i o n a l p r o b l e m s w h i c h o v e r s h a d o w e d
any a d v a n t a g e s g a i n e d .
A n o t h e r f a c t o r to be c o n s i d e r e d w h e n
s e l e c t i n g a s u i t a b l e d i s i n f e c t a n t is t h e m i c r o b i o l o g i c a l s t a b i l i t y in
water d i s t r i b u t i o n systems.X
A l a r g e n u m b e r of b a c t e r i o l o g i c a l
s t r a i n s as well a s m o l d s and p r o t o z o a a r e c a p a b l e of a f t e r g r o w t h e v e n
though the w a t e r m a y h a v e b e e n a p p r o p r i a t e l y t r e a t e d .
The
p r o b a b i l i t y of t h i s p h e n o m e n a o c c u r r i n g is p a r t i c u l a r l y likely w h e r e
the water c o n t a i n s s i g n i f i c a n t q u a n t i t i e s of o r g a n i c c o u m p o u n d s and
in a r e a s of w a r m e r w a t e r and g r o u n d t e m p e r a t u r e s . * T h e s e
m i c r o o r g a n i s m s n o t o n l y r e s u l t in d e c r e a s e d o r g a n o l e p t i c q u a l i t y b u t
may also p o s e a h e a l t h r i s k .
S i n c e b o t h the w a r m e r t e m p e r a t u r e s and
- A -
o r g a n i c levels a r e the p r e d o m i n a t e c o n d i t i o n s in L a t i n A m e r i c a and
t h e C a r i b b e a n it is i m p o r t a n t that a d i s i n f e c t a n t m e t h o d o l o g y b e
e f f e c t i v e , e f f i c i e n t , broad s p e c t r u m and that it a l s o p r o v i d e an
adequate residual.
For all of t h e s e r e a s o n s P A H O b e g a n e x p l o r i n g the f e a s i b i l i t y of
i n n o v a t i v e t e c h n o l o g y w h i c h might avoid or e l i m i n a t e a s u f f i c i e n t
n u m b e r of the a f o r e m e n t i o n e d p r o b l e m s and c a u s e s of f a i l u r e in order
to i n c r e a s e t h e p r o b a b i l i t y of a c h i e v i n g s u c c e s s f u l s u s t a i n e d
d i s i n f e c t i o n of s m a l l c o m m u n i t y w a t e r s y s t e m s .
C r i t e r i a o f d e s i r a b l e c h a r a c t e r i s t i c s for a d i s i n f e c t i o n d e v i c e
s u i t a b l e for s m a l l t o w n s and rural a r e a s in L a t i n A m e r i c a w e r e
p r e p a r e d by P A H O to u s e in d i s c u s s i o n s w i t h p o t e n t i a l d e v e l o p e r s and
researchers.
T h i s included A ) , s i m p l i c i t y of o p e r a t i o n and
m a i n t e n a n c e a n d if p o s s i b l e a v o i d a n c e of the n e c e s s i t y for c h e m i c a l
and m a t h e m a t i c a l c a l c u l a t i o n s ; B ) r o b u s t and d u r a b l e e q u i p m e n t w h i c h
is also e a s y to r e p a i r ; C> u s e of l o c a l l y or r e a d i l y a v a i l a b l e
p r i m a r y c h e m i c a l s ; D ) r e l i a b l e , e f f e c t i v e and s a f e d i s i n f e c t a n t w h i c h
would function over a wide range of typical physica1-chemica1
c o n d i t i o n s and w h i c h leaves an a d e q u a t e r e s i d u a l .
This criteria
f i r s t led to c o n s i d e r a t i o n of e x i s t i n g d e v i c e s for o n - s i t e g e m e r a t i o n
of s o d i u m h y p o c h l o r i t e , but actual e x p e r i e n c e had s h o w n t h e s e d e v i c e s
to b e too c o m p l e x for the t a r g e t e d c o m m u n i t i e s .
D u r i n g t h e l i t e r a t u r e r e s e a r c h and f o l l o w - u p w i t h a g e n c i e s ,
i n s t i t u t i o n s , s c i e n t i s t s and d e v e l o p e r s it b e c a m e e v i d e n t that it w a s
u s u a l l y s i m p l e r a n d less c o s t l y to g e n e r a t e a m i x t u r e of d i s i n f e c t i n g
oxidants than a single pure o x i d a n t .
T h e r e are
several additional
p o t e n t i a l a d v a n t a g e s to the u s e of a m i x t u r e of o x i d a n t s . :
1. D i f f e r e n t o x i d a n t d i s i n f e c t a n t s h a v e s o m e w h a t d i f f e r e n t r a n g e s
in w h i c h t h e y e f f e c t i v e l y o p e r a t e .
C o m b i n i n g t h e m may i n c r e a s e
the
p o s s i b i l i t y of b r o a d e n i n g that r a n g e .
2 . C o m b i n a t i o n o f o x i d a n t s c a n act s y n e r g i s t i c a 1 1 y as
d i s infectants.
3. D i f f e r e n t o x i d a n t s leave r e s i d u a l s of d i f f e r i n g h a l f - l i v e s
4. D i f f e r e n t o x i d a n t s h a v e g r e a t e r a f f i n i t y for r e a c t i o n w i t h
v a r i o u s r e d u c i n g a g e n t s and by c o m b i n i n g them it may be' p o s s i b l e
to m i n i m i z e t h e u n d e s i r a b l e s u b p r o d u c t s p r o d u c e d .
It w a s t h i s r e a l i z a t i o n w h i c h i n d u c e d P A H O to p u r s u e t h e
d e v e l o p m e n t of m i x e d o x i d a n t s g e n e r a t e d o n - s i t e for d i s i n f e c t i o n
(MOGGOD).
EFFECTIVENESS
OF
MIXf£D O X I D A N T S :
Table
A
d e p i c t s Y t h e r e l a t i v e o x i d a t i o n p o t e n t i a l of s o m e of t h e
strongest known oxidants.
The h y d r o x y l r a d i c a l , a t o m i c o x y g e n ,
o z o n e , h y d r o g e n p e r o x i d e , the p e r h y d r o x y l r a d i c a l , h y p o c h l o r o u s acid
and c h l o r i n e a r e a m o n g t W
o x i d a n t s p r o d u c e d by M O G G O D d e v i c e s .
P e r m a n g a n a t e is n o t .
A l t h o u g h h y d r o g e n p e r o x i d e and the p e r h y d r o x y l
r a d i c a l a r e n o t e f f e c t i v e d i s i n f e c t a n t s in w a t e r t h e y do s a t i s f y t h e
r e d u c i n g a g e n t s in w a t e r w h i c h w o u l d o t h e r w i s e u s e up the m o r e
effective disinfecting oxidants.
- 5
TABLE A
RELATIVE OXIDATION POTENTIAL OF STRONG OXIDANT SPECIES
BASED ON REFERENCE OF CHLORINE = 1.OO
Oxidant
Species
FLUORINE
HYDROXYL RADICAL
ATOMIC OXYGEN
OZONE
HYDROGEN PEROXIDE
PERHYDROXYL RADICAL
PERMANGANATE
HYPOCHLOROUS ACID
CHLORINE
Ox idation
Po tent i a 1
(volts)
2.87
2.80
2.42
2.07
1 .77
1 .70
1 .68
1 ,<+9
1 .36
Relat ive
Ox i dat ion
Power *
2.25
2.05
1 .78
1 .52
1 .30
1 .25
1 .23
1 . 10
1 .00
Duguet, Brodard, Dussert and Mallevialle found that the addition
of hydrogen peroxide to water during ozonation increased the rate of
ozone transfer and the oxidation of organic compounds. They also
found that the addition of hydrogen peroxide in the ozonation process
resulted in significant reduction of precursors of triha1omethanes.
Charles P. Hibler, determined that in water with a turbidity of
0.53 to 0.73 NTU containing 10,000 to 40,000 giardia cysts per
gallon,the combination of photozone (0.3 to 0.6 mg/1 ) and chlorine
(0.2 to 0.58 mg/1) for a period of 30 minutes of exposure were
sufficient to kill or inactivate all of the Giardia cysts while
neither photozone nor chlorine alone was able to achieve
inactivation.
The biochemical mechanisms involved in the
inactivation of the cysts is not yet well understood.
It has been
observed that long duration contact time resulted in destruction of
the cyst.
Disinfection with MOGGOD appears to be at least as effective and
very probably more effective than with straight chlorine.
Additional
closely controlled laboratory testing will be required to precisely
determine this Velation.
THE DEVELOPMENT OF M(
MOGGOD DEVICES:
(ue to tt
Largely due
the normal.course of scientific and commercial
development, and.in a small part due to PAHO'S encouragement and
promotion, several advanced
fully functional prototypes of devices
for on-site generation of mixed oxidant disinfectants (MOGGOD) have
been developed and improved. Two distinct groups of devices which
produce mixed oxidants for disinfection have evolved; one relies upon
- 6 electrolysis and the other upon photolysis to generate the mixed
oxidants. Both show considerable promise of overcoming or
circumventing many of the major problems and impediments to
d i s i nfec t ion.
The photolysis process utilizes short wave (>185nm> length
ultraviolet light
to dissociate oxygen molecules into activated
species. A schematic of this process is shown in Figure 1.
In the
PHOTOZONE process ambient air is passed along such a lamp and the
generated plasma is diffused into an aqueous solution which is
further irradiated by the ultraviolet light further boosting the
oxidizing potential as well <as contributing to the disinfection.
The
resultant oxidants in the water stream include ozone, hydroxyl
radical, hydrogen dioxide, hydrogen p e r o x i d e , and atomic oxygen.
This mixture of oxidants has been determined to have a greater
oxidizing power than chlorine g a s .
It h a s also been shown to be ^n
excellent disinfectant. The PHOTOZONE process uses typically about 7
to 11 kilowatt hours of energy to produce one kilo of the PHOTOZONE
gas.
WATER OUTLET
WATER TREATMENT CELL
/s^T^y-i----•••,.-...-..-_-..- _ ~ ^ - ^ ,
^TJr
•—V-«— .-— -y.-^-—-v.-— —>—^
UV LAMP
VENTURI
L,„„
QUARTZ
TUBE
• AIR INLET
T.
^
AIF[R TREATMENT CELL
CHECK VALVE
Figure 1.
Schematic of the PHOTOZONE principle.
Unfortunately PHOTOZONE does not include a durable residual among
its mixedx oxidants. Since an effective and durable residual is
necessary\in Latin American water systems because they are subject to
recontamin\ation this device has not yet been installed in the
demonstration project but is mentioned here because it is a generator
of mixed oxidants.
Electrolysis of a saturated salt solution also is capable of
generating mixed oxidants and a large portion of them provide and
effective residual disinfectant.
The generation of a oxidants
through electrolysis has been carrr'ed out on a commercial scale since
the turn of the century and steady advancements and improvements have
7 been made particularly in the chlor-alkalai industry.
The
introduction of the dimensionally stable anode and the perfluorinated
membranes in 196.9 and their steady improvement has radically improved
the efficiency? lowered the cost of production} and greatly reduced
power requirements of the electrolysis p r o c e s s e s .
Today 90'/. of the
chlorine capacity of North America is produced utilizing these
devices and the resultant methodology.
These advancements have made the on-site generation of mixed
oxidant gas disinfectants a feasible alternative.
The same basic
technology, but adapted to insure operational simplicity, durability
and compatiblity with conditions in remote, small and poor
communities has been used to develop the MOGGOD units. To do this
some of the efficiency of the electrolysis process has been
sacrificed but it is more than compensated for by a gain of overall
efficiency which takes into consideration the community capability,
storage, transportation, national supporting infrastructure, local
conditions and the prevalent human element.
A number of prototypes
have been produced by different entities and they are considerably
beyond the laboratory bench model stage with several units being
produced commercially and one particular model having functioned
quite well in 10 different actual field installations.
The first
installation has now been in operation for over 3 years and continues
to function exceptionally well, equalling or exceeding the efficiency
of conventional methods of chlorination which had previously been
used but failed to perform satisfactorily.
CHLORINE AND
OXYGEN SPECIES
t
WATER AND
SALT
J
HYDROGEN
t
2 - 10 VL
DC
»
t
ANODE
CELL
UJ
irt
tu
Q
O
<
ii £
tu I
CATHODE
CELL
i
SODIUM
<;
HYDROXIDE
< •
Figure
a.
Schematic
of
MOGGOD
e l e c t r o l y t i c
c e l l .
-a -
i
Figure 2 is a schematic drawing of the MOGGOD unit indicating the
relation of the electrolytic cell component* and the input and output
of chemicals. The cell is divided into the anode and cathode
compartments by a semipermeable membrane ( Nafion ) which is a high
performance reinforced composite of perfluorinated cation exchange
copolymer. The unit also
incorporates a TIR-2000 DSA anode (ELTECH)
and
a cathode of <^0 stainless steel.
In addition auxilliary
electrodes which are operated at a lower EMF than the primary anode
are located between the anode and the m e m b r a n e .
A saturated
solution of sodium chloride is maintained in the anode compartment by
the addition of water and excess sodium chloride and a 107. solution
of sodium hydroxide is maintained in the cathode compartment by the
addition of sufficient water and drawoff of excess liquid. Chlorine
and activated oxygen species (the mixed oxidant gases) are generated
at the anodes while hydrogen gas and sodium hydroxide are formed at
the cathode.
In the MOGGOD process the mixed oxidant gases are
injected into the water to be disinfected, the hydrogen gas is vented
to the atmosphere and the excess sodium hydroxide is collected to be
utilized for other purposes or to be disposed of.
A somewhat similar
cell was described by Michalek and Leitz <*>
in 1972, but no mention was made of oxygen species being generated at
the anode.
This could have been due to both the absence of an
auxilliary electrode and the use of a DSA anode developed
specifically for the generation of chlori ne rather than one for the
generation of oxygen.
Figure 3 is a graph which portrays the useful life of the TIR
2000 anode as a function of current density in amperes per square
inch of anode surface in a solution of about 15V. sulfuric acid.
Increased thickness of the iridium oxide based coating yields an
iKaa-r
Heavy
150 gpl H2S04
• 50 d e g . , C
Extended
1033
Lifetime
(days)
ira-
te
a.i
Figure
3.
-<—I I t M l
-«—•—<-M-t+-
i
is
Current D e n s i t y ( I n as I)
TIR-2000
Lifetime
vs.
Current
-4
1- I I
I I H
lea
Density
- 9
-
increased u s e f u l life e x p e c t a n c y for the a n o a e .
S i n c e the
o p e r a t i o n a l c u r r e n t d e n s i t y of t h e M O G G O D u n i t r a n g e s b e t w e e n around
0.6 and 1.0 a m p s p e r ' s q u a r e inch the life of the a n o d e will range
b e t w e e n about 3 and 8 y e a r s for the e x t e n d e d life c o a t i n g and from 7
to 12 y e a r s for t h e h e a v y c o a t i n g if the e l e c t r o d e s are
in o p e r a t i o n
c?^ h o u r s a d a y .
Another m e t h o d w h i c h is being d e v e l o p e d for the g e n e r a t i o n of a
s o l u t i o n of mixe-d o x i d a n t d i s i n f e c t a n t s u s e s an iridium coated
t i t a n i u m cell w i t h laminar f l o w .
T h i s d e v i c e w h i c h h a s functioned
well in the l a b o r a t o r y h a s yet to b e f i e l d t e s t e d in L a t i n A m e r i c a .
The d i s i n f e c t a n t s o l u t i o n h a s b e e n t e s t e d for e f f e c t i v e n e s s and
e q u a l s of e x c e e d s t h a t of c h l o r i n e .
PAHO'S PROJECT FOR
DEVELOPMENT
OF M 0 G G 0 D
TECHNOLOGY:
The initial p h a s e the M O G G O D d e v e l o p m e n t p r o j e c t w a s d e v o t e d to
p r o m o t i o n , e n c o u r a g e m e n t and f o s t e r i n g the M O G G O D c o n c e p t and w a s
p l a n n e d to o b t a i n c o n t r i b u t i o n s f r o m g o v e r n m e n t a g e n c i e s ,
u n i v e r s i t i e s and a c a d e m i c i n s t i t u t i o n s , p r o f e s s i o n a l o r g a n i z a t i o n s
and p r i v a t e i n d u s t r y .
T h i s w a s c a r r i e d out p r i m a r i l y through
p e r s o n a l c o n t a c t and d i s s e m i n a t i o n and s h a r i n g of i n f o r m a t i o n .
It
w a s also i n c o r p o r a t e d into P A H O ' s p r o g r a m for i m p r o v e m e n t of d r i n k i n g
water q u a l i t y and the M O G G O D c o n c e p t w a s b r o u g h t f o r t h at P A H O
w o r k s h o p s , c o n f e r e n c e s , s e m i n a r s and m e e t i n g s w h i c h in any way w e r e
r e l a t e d to d r i n k i n g w a t e r , water q u a l i t y , w a t e r t r e a t m e n t ,
distribution systems.
A d v a n c m e n t s in all r e l a t e d a r e a s of t e c h n o l o g y
were closely monitored.
S i t e s w h e r e i n s t a l l a t i o n of M O G G O D type
d e v i c e s had b e e n m a d e by the p r i v a t e s e c t o r w e r e v i s i t e d .
S o m e of
the m o r e p r o m i s i n g p r o t o t y p e s and s e c o n d g e n e r a t i o n M O G G O D d e v i c e s
w e r e p u r c h a s e d and limited t e s t i n g w a s c a r r i e d o u t by P A H O s t a f f .
Many p r o j e c t p r o p o s a l s for M O G G O D d e v e l o p m e n t w e r e p r e p a r e d and
s u b m i t t e d to f u n d i n g a g e n c i e s .
A total of four M O G G O D d e v i c e s w e r e p u r c h a s e d by P A H O for u s e in
s i t u a t i o n s of e m e r g e n c i e s b r o u g h t a b o u t by n a t u r a l d i s a s t e r s for
t e m p o r a r y d i s i n f e c t i o n of water s u p p l i e s .
This was done because
s h i p m e n t of c h l o r i n e p r o d u c t s by a i r f r e i g h t w a s p r o h i b i t e d and the
p a r t i c u l a r d e v i c e s u t i l i z e d salt a s t h e p r i m a r y m a t e r i a l .
They
f u n c t i o n e d well b u t t h e length o f o p e r a t i o n w a s too s h o r t to d r a w
many c o n c l u s i o n s a b o u t d u r a b i l i t y , c o n t i n u i t y o f ' o p e r a t i o n , r e p a i r s
or m a i n t e n a n c e p r o b l e m s .
In July 1986 P A H O a w a r d e d a r e s e a r c h g r a n t for i n v e s t i g a t i n g t h e
e f f e c t i v e n e s s and e f f i c i e n c y of a M O G G O D d e v i c e r e l a t i v e to c h l o r i n e
and in D e c e m b e r 1986 a d v a n c e f u n d s w e r e r e c e i v e d from U N D P under t h e
PAHO/UNDP Critical Poverty Program.
Matching funds were obtained
f r o m c o u n t r y o f f i c e s and m o r e t h a n f o r t y M 0 G G O D d e v i c e s h a v e b e e n
p u r c h a s e d and s e n t to L a t i n A m e r i c a and t h e C a r i b b e a n for
d e m o n s t r a t i o n p r o j e c t s , field t e s t i n g , l a b o r a t o r y a n a l y s i s .
Countries which have received these d e v i c e s are Argentina, Bolivia,
Brasil, Columbia, Costa Rica, E c u a d o r , Guatemala, Honduras, Jamaica,
Mexico, Peru and S t . L u c i a .
M o s t o f t h e c o u n t r i e s h a v e a g r e e d to
c o l l a b o r a t e in the d e m o n s t r a t i o n / d e v e l o p m e n t p r o j e c t and h a v e
10 commenced various activities but two of the countries have declined.
Collaboration is under consideration in Cuba, Barbados? Chile,
Paraguay and Venezuela.
Research has been carried out in Argentina, Mexico, and the USA
and more is in the formative stages in Argentina, Brasil, Colombia,
Cuba, Guatemala, Ecuador and Peru.
PURPOSE OF THE DEVELOPMENT PROJECT:
The overall objective of the development project is to foster and
accelerate the development of MOGGOD technology in a manner which
will serve the needs of small towns, communities and rural villages
of Latin America and the Caribbean.
The specific objectives are to:
1. Test various MOGGOD devices under as wide a range of actual
but typical field conditions as possible to determine advantages
and disadvantages, strengths and weaknesses and to make
recommendations for improvement of the devices.
2. Obtain a better understanding of the technologies involved
the production and utilization of mixed oxidants
in
3. Disseminate knowledge and information regarding MOGGOD among
the institutions and agencies of Latin America.
*•. Encourage international
this technology.
collaboration in the development of
5. Provide data on which to base installation criteria,
operation and maintenance instructions, to obtain further
refinements and improvements in design and manufacturing.
6. Determine the feasibility of manufacturing
locally.
the equipment
7. Develop parametric relationships for equivalent mixed oxidant
residual and free chlorine residual.
8. Determine the minimum mixed oxidant residual
pathogen free water.
to guarantee
9. Feed back field performance characteristics to manufacturers
to facilitate improvement of equipment performance and
reliability and to improve manufacturer support services and
reduce c o s t s .
10. Determine and understand
MOGGOD.
11. Develop a data base for
maintenance costs.
the complex chemical reactions of
installation and operation and
12. Define commercial quality standards for manufacturing
MOGGOD
-
devices and improve technical
13. Determine the practical
capac i ty .
1*1
-
specifications.
upper
limits of MOGGOD device
14. Determine the effectiveness of MOGGOD against specific
waterborne pathogens under varying conditions of turbidity* pH,
and temperature.
15. Investigate the potential of MOGGOD for removal of
undesirable substances from drinking water such as iron, heavy
metals, phenols, cyanides etc.
SUMMARY OF ACTIVITIES CARRIED OUT TO DATE:
1.
Lecture-demonstrations of MOGGOD Technology were carried out in
twelve countries> involving 48 agencies or institutions.
2.
A total of 47 units of MOGGOD and assesories were purchased
Argentina, Bolivia, Brasil, Colombia, Ecuador, Guatemala,
Honduras, Jamaica, Mexico, Panama, Peru and St. Lucia.
3.
Models for easy to understand manuals for: a) installation of
MOGGOD, and
b) operation and maintenance of MOGGOD were prepar
under contract in both Spanish and English.
4.
Technical information on MOGGOD was provided to all of the
pertinent agencies of the countries participating in the
PAHO/UNDP Program and to ar\ additional seven countries and thei
appropriate agencies.
5.
Draft proposals for national MOGGOD demonstration projects were
prepared and provided to Argentina, Colombia, Mexico, and Peru
for submittal to the national offices of UNDP for funding.
6.
Draft terms of reference for participation in a regiona,l MOGGOD
demonstration project were developed and provided to eight
countr ies.
7-
Three MOGGOD research projects were implemented and five
additional research proposals and protocols and are in the stag
of soliciting funds.
8.
As a direct result of this project, manufacturing of MOGGOD
devices has been initiated by private industry (FENAR) in
Argentina and is being explored in Mexico by CEDAT. CEDAT has
developed a number of prototypes, which are being field tested.
It is under consideration in Colombia
9.
MOGGOD devices have been installed in seven of the participant
countries and field testing is underway .
to
10. Field visits were made to a total of 20 potential field
demonstration sites and instructions for site preparation and
MOGGOD
installations
were
provided.
11. An i n t e r n a t i o n a l s e m i n a r on d i s i n f e c t i o n of small c o m m u n i t y
s u p p l i e s w i t h M O G G O D w a s held almost e x a c t l y o n e year after
demonstration - development project was initiated..
water
the
FINDINGS TO D A T E :
T h e r e are s e v e r a l p o t e n t i a l e c o n o m i c b e n e f i t s of improved
disinfection through MOGGOD.
T h e r e is b o t h the d i r e c t cost r e d u c t i o n
of the d i s i n f e c t a n t i t s e l f and that w h i c h is d u e to s i m p l i f i e d
o p e r a t i o n and m a i n t e n a n c e r e q u i r e m e n t s of the a p p a r a t u s .
Another
e c o n o m i c b e n e f i t w o u l d a f f e c t t h o s e c o u n t r i e s w h i c h import c h l o r i n e
and c h l o r i n e p r o d u c t s by r e d u c t i o n in f o r e i g n e x c h a n g e of c u r r e n c y .
F i n a l l y , t h e r e is t h e i n t u i t i v e l y o b v i o u s b u t less d e f i n i t i v e
economic benefit of a healthier people.
A l t h o u g h m o r e t i m e is needed to s u f f i c i e n t l y s t r e s s the
c o m p o n e n t s of t h e M O G G O D d e v i c e s it p r e s e n t l y a p p e a r s that the
of M O G G O D d i s i n f e c t a n t r a n g e s f r o m U S * 0.E5 to 0.60 per kilo
produced.
cost
T h e r e a r e a n u m b e r of a d v a n t a g e s of M O G G O D w h i c h should h e l p
avoid a number o f t h e p r o b l e m s e n c o u n t e r e d in s u s t a i n i n g c o n v e n t i o n a l
ch1 o r i n a t i o n , p a r t i c u l a r l y in small and r e m o t e t o w n s and c o m m u n i t i e s .
They a r e :
The o n l y m a k e up c h e m i c a l s ^re
salt ( s o d i u m c h l o r i d e ) and w a t e r .
S o d i u m c h l o r i d e is a v a i l a b l e a l m o s t e v e r y w h e r e for other u s e s .
T h i s c h e m i c a l is e a s i l y t r a n s p o r t e d , s t o r e d , h a n d l e d w i t h m i n i m a l
hazard to t h e e n v i r o n m e n t and n o n e to the w o r k e r .
It is a l s o o n e
of the least e x p e n s i v e c h e m i c a l s a v a i l a b l e .
Power r e q u i r e m e n t s Bre e x t r e m e l y low.
T h e v o l t a g e r e q u i r e m e n t is
b e t w e e n 5 and 10 v o l t s at the e l e c t r o d e s and t h e c u r r e n t d r a w n is
about 12 a m p s per k i l o g r a m of d i s i n f e c t a n t g e n e r a t e d over a 2 ^
hour p e r i o d .
If c o n v e n t i o n a l e l e c t r i c i t y is n o t a v a i l a b l e it is
f e a s i b l e to u t i l i z e p h o t o v o 1 t a i c s or m i n i - g e n e r a t o r s a n the w a t e r
t r a n s m i s s i o n line for a power s o u r c e .
Operational r e q u i r e m e n t s are visually o r i e n t e d .
M a t h e m a t i c a l and
c h e m i c a l s k i l l s a r e n o t e s s e n t i a l for the c o r r e c t o p e r a t i o n .
It
c a n b e v i s u a l l y d e t e r m i n e d w h e n it is n e c e s s a r y to add s o d i u m
chloride.
T h e o p e r a t o r m e r e l y l o o k s to s e e if the salt c r y s t a l s
or the w a t e r level a r e g e t t i n g low and a d d s s o m e m o r e if
necessary.
T h e a m o u n t of d i s i n f e c t a n t a p p l i e d is d e t e r m i n e d by
the a d j u s t m e n t of a dial ( r h e o s t a t ) to o b t a i n a p r e d e t e r m i n e d
c u r r e n t i n d i c a t e d by a n e e d l e .
All of t h i s s i m p l i f i e s o p e r a t i o n
for the t y p i c a l p o o r l y e d u c a t e d o p e r a t o r .
The o x y g e n s p e c i e s
of the m i x e d g a s d i s i n f e c t a n t are the
d o m i n a n t s p e c i e s a n d tend to r e a c t w i t h o r g a n i c s and o t h e r
s u b s t a n c e s b e f o r e t h e c h l o r i n e s p e c i e s . T h i s r e s u l t s in the
chlorine species acting primarily as a r e s i d u a l .
This generally
r e s u l t s in i m p r o v e d t a s t e and o d o r of the w a t e r and e n h a n c e s user
t
I
- 13 -
support for continuous and re-liable disinfection.
The electrode to electrode power consumption in the MOGGOD units
to date fall in the range of ^ kilowatt hours per kilog>~am °f
oxidant produced.
The MOGGOD device produces only the amount of oxidant needed
instantaneously thereby decreasing the problems of storing large
quantities of highly reactive substances.
To date it has been determined that MOGGQD disinfection is at
least equivalent to disinfection with chlorine in both the laboratory
and actual field installations. Additional experiments are necessary
to check the effectiveness against various pathogens.
The weakest component of the MOGGOD devices is the membranes.
Care must be taken to not puncture them. Even though training has
been given and warnings of the fragility of the membrane, it has been
punctured when the operator tries to clean off deposits with
something other than water, such as a brush or screwdriver. Some of
the techniques and methods used for installing and replacing
membranes do not lend themselves well to easy repairs.
The use of impure salt (sodium chloride) has caused more problems
than any other factor through clogging of the membrane.
Apparently
there is a great temptation to use impure salt and the unit will
function for quite some time using impure salt but the decrease in
useful membrane life is directly proportional to the increase in
impurities.
It is possible to clean the membrane with an acid
solution
but the inconvenience
and labor costs ^re higher than the
difference in cost between pure and unpure salt.
Even though instructions have been given and installation drawing
provided a number of installation have been poorly designed and
constructed.
A technical expert should be present for the first
installations in a country or region of a country. A concerted
collaborative effort should be made to develop a good selection of
standard drawings for typical installation conditions in Latin
America and the Caribbean.
MOGGOD devices do not constitute a panacea but a good
for disinfection in small community systems.
alternative
Even though the operation and maintenance of the MOGGOD devices
are extremely simple, training is nonetheless required for new users \
of this technology.
They require attention at least once a week and
preferably twice a week.
EXTENDED ABSTRACT
COMPARATIVE BACTERICIDAL
AND VIRICIDAL ACTIVITY OF
GENERATED OXIDANTS USED FOR THE DISINFECTION OF WATER
ON-SITE
PAN AMERICAN HEALTH ORGANIZATION WORKSHOF
LIMA, PERU
DECEMBER 7-11. 1987
VINOEN'J P OLIVIER I
DEPARTMENT OF GEOGRAPHY AND ENVIRONMENTAL ENGINEERING
THE JOHNS HOPKINS UNIVERSITY
BALTIMORE, MARYLAND
A small pilot scale study was conducted in the laboiatory to
determine the efficacy of
the mixed oxidants <?e:.i_ 1 a':eo froi.v ."r::-..;3 1 electrolytic cell.
The specific objectives were:
1. to compare the bactericidal and viricidal activity
of the
mixed oxidants
generated by the on-site
generated disinfectant device to that of an equivalent
concentration of free chlorine.
2. to determine the presence or absence of short-lived
biocidal species in the mixed oxidants produced by the
on-site generated disinfectant device.
EXPERIMENTAL PROTOCOL
Comparative Disinfection
,
The disinfection trials were conducted in three plug flow
reactors, run in parallel.
Baltimore City tap water was
dechlorinated by filtering through granular activated carbon
column and was used for this series of experiments.
The
dechlorinated tap water was not tempered or buffered. The
temperature over the course of the experiments was 18-23 C and
the pH ranged from 7.0 to 9.0.
A microbial test mixture
containing washed and purified suspensions of E. coli, P.
aeruginosa, and or B_. subtil is. and F2 virus at level of 10 7 to
10L' of each of the test raicroorganissvts/ml was aspirated into
dechlorinated, unteiapered and unbuffered Baltimore city tap water
and allowed to mix through a short coil of 1/2 inch tubing prior
to the addition of disinfectant.
The total flow for the three
parallel reactor system was slightly taove than 2 gal/min.
The
mi -•?-o! i al mixture was metered in such that the microbial tost
;i:. ::t. •„:*.;•• was diluted about 1000 fold. The final microbial density
at timir sero was about 10000/ml for each microorganism. Control
samples were collected for determination of chlorine residual and
microbial density after the granular activated carbon over the
course of the experimental trial.
The flow containing the test
microbial mixture was split in three continuous plug flow
reactors. The reactor conditions are listed in table 1. Reactor
A, B, and C contained the following disinfectants, the gas form
the on-site oxidant generator, the solution prepared from the
gas from the oxidant generator and a chlorine solution prepared
from chlorine gas, respectively.
The presence of short-lived
oxidants produced was evaluated by preparing a solution from the
oxidant gas about 1 hour prior to the
beginning of th«:
disinfection trial and allowing the gas to prereaot to dissipateany short-lived intermediates.
Table
reactors.
REACTOR
A
B
C
Reactor
FLOW
GAL/MIN
1'. 0
0. b
0.5
0 '
0.5 _
conditions
for
.
DISINFECTANT
the three parallel plug flow
INITIAL
MICROBIAL
DENSITY
tt/ML
pri
TEMP
C
oxi gas
10000
7.0-9.0
oxi solution
10000
6.8-9.0
10000
6.8-9.0
. .chlorine
18-2c C
18-23 0
18-23 0
Reactors A, B and C received the same test water at the same
microbial, chemical and physical conditions. The oxidant gas or
solution was aspirated into each reactor and the oxidant flow war:
monitored by a rotameter and controlled with a metering valve.
The disinfectant flow was adjusted such that the total residua!
oxidant was the same at the first sample port immediately
following the disinfectant aspirator and mixing loop. The test
system was allowed to equilibrate and was monitored residual
disinfectant for
1 sample course prior to beginning each
experimental trial.
Sampling protocol
Each reactor had provisions for 4 sampling ports after thu
addition of disinfectant.
The contact time for each port and
each reactor was determined with fluorescein dye tracer added at
the disinfectant aspirator under the conditions of flow used for
the experimental trials. The contact times for the sample ports
in each reactor are given in table 2.
3
Table 2. Contact time determined by fluorescein dye tracer
studies. Fluorescein was added at the disinfectant aspirator and
continuously monitored at each sample port. The flow rates for
reactors A, B, and
C were
1.0, 0.5
and 0.5, gal/rain,
respectively.
Each number represents the average of AT LEAST 6
trials for each port.
TIME. SECONDS
A
b
7 •
21
21
17
PORT 2
40
77
76
P'-"'RT '•'-
58
115
123
POkT -S
80
150
148
PSACTOR
PORT 1
•
After equilibration and monitoring, the three plug flow reactors
were run simultaneously with three sample cycles for each trial.
Samples collected for chemical and biological analysis.
Each
sample cycle consisted of an initial 200 ml sample to rinse th>-.
port and collection beaker, a 200 ml sample for chemical analysis
and an approximate 75 ml sample for microbiological analysis.
Th-? chemical samples from the first and third cycles were
immediately assayed for free oxidant and total oxidant by
aruperometric titration while the second cycle chemical sample was
used for the determination of pH.
The grab biological samples
were collected and combined in a 250 ml sterile polyethylenebottle containing 0.2 ml of a 1 % thiosulfate solution to stop
the action of the oxidants. Chemical and biological samples were
also collected after the carbon filter and before disinfectant
addition (This was the zero time sample. No.) for each cycle.
Tota] oxidant in the latter samples was determined by the DP.v
method and was always negative after the carbon column.
The
biological assays were conducted as soon as possible after each
trial.
METHODS
Chemical
Preparation and Assay of Disinfectants
" Chlorine --"'•--..--.-> v.
rH
amp*
-f
described in Standard
Methods for the Analysis nl
-Hater and
Haste water. (APHA, 1 9 8 5 ) .
The oxidant gas was generated
in an electrolytic cell
supplied and manufactured by Oxidizers Inc. located in Virginia
Beach, Va. , USA.
The oxidant g a s generator was set up and
operated according to
the
instructions
supplied
by the
manufacturer with minor modifications
Total oxidant will be
measured by the amperometrie and colorimetric tuethoth?
used for
chlorine given in St.aiidard^JleiuJids (A.PHA 1985'
MICROBIOLOGICAL
{''reparation and Assay of Bacteria
Esj2he_r_Lc!iia cc-UL strain B war; grown overnight under aerated
conditions at 37 C on tryptone yeast extract (TYE> broth. The
bacteria was washed three times in phosphate buffered saline and
added to the water to be disinfected
at a density of 10,000
colony forming units/ml
(cfu/ml).
Survival of E.. c.qLi was
determined by spread plates on Maoonkey's agar.
Red colonies
'/•ore counted after incubation at ?1 0 for •!<: hours.
?.0'o_uji.'iIL,iLUai a.t_;:U£l;JiL'£a was «'rown overnight undor aer^t'-d
•" •"nd.it ions at 37 C on tryptone
yeast extract
-'TYE; brorh. The
bacteria was washed three times in phosphate buffered sa'iit.e ytid
added to the water t o be disinfected at a density of 10.000
cfu/ml. Survival of £. aeja;£j_nj2aa was determined by spread
plates on Maconkey's agar. Colorless colonies were counted after
incubation at 37 C for 48 hours.
Bacillus subtil is spores were prepared were added to the
water to be disinfected at a level of about 10000 cfu/ml.
Survival of B_, silbtJJJjl spores was determined by spread plates on
tryptioase soy agar after treatment of samples at 80 C for 10
.',ni mites.
Orange colonies were- enumerated after 48-72
hcurs
:
•• .'•!•.• .!" -:t- on at room temperature.
:
':••:i'ar:--.ion ;3nd Assay at V2 Bacterial Virus
The bacterial
virus was grown and purified and adde'd to the
test system at about 10000 plaque forming units /ml, pfu/ml.
The
survival of F2 will be determined by the agar overlay technique
on tryptone, yeast extract agar using E.. coli K13 as host.
Plaques were counted after 18-24 hours incubation at 35 C.
RESULTS \
The total oxidant residual reported as available chlorine is
shown in figure 1 for the three parallel plug flow reactors for
oxi gas, oxl solution and chlorine for the time course of the
d i rinf ectio_n\ The d a t a is for experiments conducted at a setting
of 5 0 -8.2 amps for the oxi generator and represents the average
•f o-.e. trials. The total
residual oxidant
was similar
for the
• > .••'•••'•• d i r, i n f e e t a n t s .
•ri £•"•"•:•••
;';' si.riv:?
the
S ' U ^'i v;.• i
of
J\.
!.•••) i + :,i"''i;; 1: '!;•
1 f :' t
.<•• /: * ' m wi'nout any oxidant.
The level:.; of E. coil
-..re nrporre,!
<-is the survival
fraction, N/No and remained constant over the
time course of the experimental trials.
Little difference was
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observed for the three different reactors. Similar results were
obtained for P_. aeruginosa,, fi^ .subtil is and f2 virus.
The comparative disinfection of E. ccJLi, P_. aeruginosa, and
f2 virus is shown in figures 3a, 3b, and 3c, respectively. The
survival of each microorganism is reported as the log of the
survival fraction over the time course of disinfection
Each of
the test microorganisms was rapidly inactivated with each of the
test disinfectants.
Little difference was observed for the
microbial survival for the oxi gn-.;, the oxi solution or the
chlorine solution.
Figure 4 shows the .tot*] oxi-iant residual for com pa rat i v.;
trials where the current to the oxi gas generator was varied fro;.:
2-8 amps. The total oxidant wes about 0.5 mg/1 for the 2 and thA amp trial, while the total oxidant was about 2.5 for the 6 and
8 amp trials.
The oxidant residual was constant over the time
course of disinfection.
The comparative microbial inactivation
is shown in figure 5a thru 5c. When the difference in oxidant
residual is taken into account, little
difference in the
disinfectant efficacy for the oxi gas wa.'- found.
SUMMARY
The gas produced by the on-site disinfectant generator
rapidly inactivates £. coli, ' E. aeruginosa, and f2 virus in
water.
The disinfectant activity the gas appears to be
equivalent chlorine solutions at an equal total oxidant residual
under the same chemical and physical conditions. No evidence for
the presence of biocidal short-lived products was observed.
ACKNOWLEDGEMENT
This study was supported by the
Pan American Hc-.-ilth
Organization.
The on-sit oxidant generator was supplied by
Oxidizers Inc. located in Virginia Beach, Va., USA.
The author
gratefully acknowledges the assistance of Maria Yolanda Ramirez
and Silvio Arango-Jaramillo and the technical assistance of Ed
Rhode, Paula Larson, Lynne Cox and Glorestine Toles.
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Presented 'at the International Seminar on
Disinfection with Mixed Oxidants Generated
Health' Organization,
0nsite)
Pan
American
Lima, Peru, December 5-12, 1987
WATER DISINFECTION WITH A MIXED-OXIDANT SOLUTION
Ann M. Pendergrass, Helen F. Gram, Deborah K. Steele, and Marke W. Talley
Los Alamos Technical Associates, Inc.
Los Alamos, NM
Abstract
An innovative water t r e a t m e n t system produces a solution of mixed
oxidants, including free chlorine, hydrogen peroxide, hypochlorite, ozone, and
free radicals from dilute brine. The small, rugged, portable unit operates
unattended and at a low power requirement. Each volume of the mixedoxidant solution, which is fed directly into water to be disinfected, can t r e a t
up to 1,000 volumes of contaminated water. The t r e a t m e n t method has
proved effective against several human pathogens, including cysts and spores.
Treated water meets all U.S. drinking water standards and recommendations.
1.
Introduction
Safe drinking water is a goal but not a reality in many parts of the w o r l d -
developed as well as developing countries. One answer to this need is a small, portable
water t r e a t m e n t unit that can be safely operated a t low cost by people who are not
highly technically trained and that can serve a range of community sizes.
Los Alamos Technical Associates, Inc. (LATA), located in New Mexico, has
developed a simple, low-voltage electrolytic method of sterilizing potable water that can
be used in r e m o t e locations, developing countries, and natural disaster areas.
The
method requires only electrical power and salt or seawater and produces a mixture of
oxidants directly in solution. One volume of the oxidant stream mixed with 50*0 to 1,000
volumes of contaminated water will quickly kill common microorganisms, including
human pathogens such as Giardia, Legionella, and Pseudomonas t h a t are resistant to
chlorine. The t r e a t e d water meets U.S. drinking water standards and is safe for human
consumption.
Power requirements are 12 V dc t o 24 V dc, 14 A for a unit capable of
producing up to 30,000 £ (8,000 gal) of potable water per hour of operation or 700,000 I
(180,000 gal) of potable water in a 24-hr day. The unit operates unattended and can be
^maintained by serni-skilled persons.
In addition, no hazardous products are required or
produced.
The water t r e a t m e n t system developed by LATA is small in size, rugged, and
portable. The pilot unit shown is about the size of a television set. The only moving part
-4
.OS-Alamos Technical Associates, Inc.
of the system is a small pump that moves salt solution through the system. The mixedoxidant solution, which is electrolytically produced, contains free chlorine, hydrogen
peroxide, hypochlorite, free radicals, and ozone. This solution mixes directly and easily
with the water to be disinfected, offering some advantages over gas-phase systems,
which will be discussed later. A U.S. patent application is pending.
2.
General Description of the Electrolytic Water Treatment System
The water treatment system is designed to be very flexible and simple in both
construction and operation. Required parts are
a salt solution supply, such as 550 J, (150 gal) tanks;
a power source, which can be 220 V ac or 110 V ac;
a transformer to produce 12 V dc to 24 V dc, 14 A current;
an electrolytic cell to produce the oxidant solution, 10 cm (4 in. x 6 in.);
two rotometers to adjust the flow rates of the oxidant and discarded streams;
a vacuum breaker seal pot to keep the flow rate of the oxidant solution
constant when the supply line is connected to a jet cductor;
an oxidant outflow line; and
a discard outflow line.
The unit is contained in an all-weather fiberglass case.
Because salt water is
corrosive, all wetted parts are stainless steel or polyvinyl chloride.
A diagram of the water treatment system shows its schematic design (Figure 1).
External connections supply electrical power and dilute salt solution to the unit. Both
power and salt can be supplied in several ways, making the unit highly adaptable,to local
conditions. The power supply can be 220 V ac or 110 V ac. According to a study made by
one of LATA's engineers, power could also be supplied from solar panels.
With some
modifications, a 12 V diesel generator could also be used.
The dilute salt solution can be provided by seawater or by crystalline NaCl added
to water\drawn from the supply line before treatment, as shown in the schematic.
Preparation of the dilute salt solution can be simplified for nontechnically trained
personnel (Figure 2). A saturated solution of salt is prepared; then a known volume of
the saturated solution is diluted to a predetermined volume in the feed tank.
2
The
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saturated concentration of NaCl is not very sensitive to temperature; there is only about
a 10% increase (35.7 g to 39.1g/100 ml) between 0°C and 100°C.
This variation in
salinity can be compensated for by a transformer that supplies a constant current.
From the supply tank, salt solution is pumped through the electrolytic cell.
Oxidants produced in the cell emerge in the anolyte stream, and the catholyte stream is
discarded. The rotometers control the rate of flow through the system. A jet eductor,
which has no moving parts, operates on the pressure drop caused by flowing liquid—that
is, the oxidant solution is aspirated into the water stream (i.e., venturi effect).
The
partial vacuum on the feedline of the jet eductor introduces the oxidant solution into the
water to be treated.
3.
Operating Parameters of the Water Treatment System
Sizing Flexibility
The water treatment system is designed to be flexible to meet the requirements of
the specific location. The oxidant production unit is modular; two or more could be
installed in a series if the demand for treated water exceeds the capacity of a single unit
uid to provide backup capability if a unit should require maintenance or fail.
Alternatively, a unit could be operated for only part of a day. The flow can thus be
matched to local demands.
Production Capacity
One modular unit with the cell operating at 14 A uses dilute brine at the rate of
60 8/hr (16 gal/hr) as feedstock.
seawater.
The brine is 0.75 M NaCl, which is equivalent to
The unit produces 30 8/hr (8 gal/hr) of mixed-oxidant solution and the same
volume of discard (Table 1).
Based on effectiveness tests, this volume of oxidant
solution can treat 30,000 8/hr (8,000 gal/hr) of potable water.
Maintenance
\
Continuous, unattended operation has been demonstrated with the pilot water
treatment system. A unit can be sized so that it is only necessary to replenish the brine
5
)S Alamos Technical Associates, Inc.
TABLE 1
WATER TREATMENT SYSTEM OPERATING PARAMETERS
Power Use
Cell
Pump
12 V to 24 V, 14 A
110 V, 1 A
Salt Use
1.8 kg/hr (4 Ib/hr)
43 kg/24 hr (95 lb/24 hr)
Brine Flow R a t e
Oxidant Production
Discard Stream
60 Sl/hr (16 gal/hr)
30 8,/hr (8 gal/hr)
30 l/hr (8 gal/hr)
Water Treatment Rate
at 1: 1000 oxidant solution
to contaminated water
30,0(H) d/hr (8,000 gal/hr)
700,000 £/24 hr (180,000 gal/24 hr)
supply once each day. Operators need not be highly trained.
Their requirements are to
fill the brine tanks, turn the unit on, verify flow rates and ampere reading, and test for
chlorine in the treated water by using a standard color test kit.
Power Sources
The pilot water t r e a t m e n t unit was developed for a 220 V, 50 Hz power supply. A
constant current transformer supplies 110 V to the pump and variable voltage at 14 A to
the cell. The unit can readily be adapted to other power sources. The voltage supplied
to the cell to c r e a t e a 14 A current flow may depend on p a r a m e t e r s of the local water
used to prepare the brine feedstock.
Salt Supply
The water t r e a t m e n t system has been developed for dilute brine feedstock such as
seawater or 0.75 M (30 g/J or 0.25 lb/gal) of NaCl solution.
Alternatively, a s a t u r a t e d -
bed feedstock can be diluted to achieve this same concentration.
seawater are widely available.
\
6
Both dry NaCl and
Los Alamos Technical Associates, Inc.
Cost of Operation
The economics of operation depend upon local costs for salt and electrical power.
The support equipment requirements are modest, including tanks for brine feedstock,
assorted piping, a jet eductor to mix the oxidant solution with water to be treated, and
a time clock if the unit is to operate on less than a continuous basis. The installation is
relatively simple compared with installing a conventional chlorination system.
No
hazardous materials need to be procured or stored.
Potential Applications
This small, rugged, simple water treatment unit could be utilized in many locations
because it is independent of a developed power grid, of trained maintenance personnel,
of hazardous or imported chemical supply, and of adjacent industrial support.
Some
potential applications include
remote permanent locations,
mobile exploration teams,
natural disaster relief operations,
military units, and
shipboard installations.
A major industrial application is its use in cooling water systems as a replacement
for toxic algicides such as chromates.
4.
Advantages of a Liquid Mixed-Oxidant System
LATA's water treatment system differs from several other systems in that mixed
oxidants are produced and used in a dissolved form.
This offers several advantages,
including the fact that liquids are more readily contained and monitored than gases. Gas
leaks constitute a real hazard in commercial installations that use gaseous chlorine or
ozone.
When gas-phase oxidants are introduced into water, the oxidants must be
transferred from gas bubbles into the liquid phase before becoming effective.
The
velocity of the transfer is proportional to the surface area of the bubbles. In industry,
the transfer of materials from gas to liquid is facilitated by creating tiny bubbles and by
increasing the turbulence of the liquid phase with a stirrer or static mixer.
methods require additional input of energy.
7
These
In contrast, a solution of mixed oxidants
p&Alamos Technical Associates, Inc.
'mixes rapidly and completely with water to be treated. Here, additional energy is not
required for mixing. The oxidant solution Is easy to contain and easy to measure. Any
liquid leaks are readily detected and, with this system, can be readily repaired as
previously proven during operational testing.
The mixed-oxidant solution is introduced into water to be treated immediately
after it is produced. This allows even the short-lived oxidants that are electrolytically
produced to contribute to the effectiveness of the method in achieving rapid kills of
microorganisms.
Systems that incorporate some time lag between production and
utilization of the oxidants may lose the synergistic effect of any short-lived oxidants.
Another advantage to this flow-through system is that the discard stream is not
highly caustic, the pH is around 9. The discard stream can be treated as wastewater.
Some systems that produce gas-phase oxidants generate a large amount of hydrogen gas
along with the chlorine or hypochlorite, leaving a very caustic NaOH residue that cannot
be discarded without special precautions.
5.
Electrolytic Production of Mixed Oxidants
Our studies have shown that mixture of oxidants may be more effective against a
mixed population of microorganisms than a single oxidant and thus may offer significant
advantages in treating potable water.
Different types of microorganisms show the greatest sensitivity to different
disinfectants, as shown in Table 2. Although ozone is the overall most effective of the
disinfectants shown, chlorine as hypochlorous acid is more effective against viruses
(Grayson, 1981). Spores and cysts are difficult to kill by any means. As a bactericidal
agent, ozone acts rapidly by lysing the cell wall; whereas, chlorine kills more slowly by
diffusing into cells and inactivating the enzyme systems (EPA, 1979). The simultaneous
production of several oxidant species, then, could be a real advantage in a water
treatment system.
\
\
The electrolytic process by which oxidants are generated in LATA's water
treatment system depends upon Group VIII metal electrodes (the platinum group) that act
as catalytic surfaces to produce free chlorine, hydrogen peroxide, hypochlorite, and
strong but short-lived oxidants tentatively identified as ozone and free radicals from
NaCl solutions. A typical composition of the mixed-oxidant solution is shown in Table 3.
8
, Los Alamos Technical Associates, Inc.
TABLE 2
COMPARISON OF OXIDANT DISINFECTION EFFICIENCY AT 5°C
.
Disinfectant
Virus
Spores
Amoebic
Cysts
03
500
0.5
2
0.5
C l 2 (asHOCl)
20
1.0
0.05
0.05
0.2
<0.02
0.0005
0.005
0.1
0.005
0.002
0.02
Cl 2
(asOCD
Cl 2 ( a s H 0 2 C l )
#
Oirganism
Entril
Bacteria 1
•Source: Grayson, M. "Ozone," iin Kirk-Othmer Encyclopedia of CChemical
Technology, Volume 16, 3rd ed., John Wiley & Sons, NY, 1981.
Under a Small Business Innovative Research (SBIR) grant from the U.S. Navy,
investigations were made using electrodes made of platinum, iridium oxide, and
ruthenium oxide. Under identical conditions, the iridium oxide electrodes produced the
greatest concentrations of chlorine and short-lived oxidants.
TABLE 3
COMPONENTS OF MIXED-OXIDANT SOLUTION*
Component
Concentration
(mg/8)
Analysis
Method
Cl 2
385
Phenylarsine t i t r a t i o n
H202
200
UV absorbance (290 nm)
r
HOC1
trace
Short-Lived Oxidants
(O3, Free Radicals)
30
Phenylarsine t i t r a t i o n
Indigo trisulfonate dye
decolorization (600 nm)
•Conditions: 0.75 M NaCl solution; flow rate, 30 8/hr; IrOo electrodes, 12 V
dc, 14 A
\
The concentration of oxidant species produced is related to thexcurrent flow across
the electrolytic cell, as shown in Figure 3. The data shown were generated using the
prototype unit shown earlier, except that a variable power source "was used.
9
)s'Alamos Technical Associates, Inc.
PROTOTYPE WATER TREATMENT UNIT
ELECTROLYTE 0.7SM NaCl (30 g/f) IN DISTILLED WATER
ELECTRODES Ir0 2
PRODUCTION RATE 30 t/hr
HYDROGEN
PEROXIDE
(mg/;)
r-«00
FREE
CHLORINE
(mg//)
700 - i
GOO -
-300
SHORT-LIVED
OXIDANTS
(mg/f0 3 )
FREE CI
r-50
soo
- ?.00
0)0 -
- 40
- 30
200
SHORT-LIVED
OXIDANTS
•
- 100
200 -
20
•••*
10
100
~n
7
(5)
i
11
(7.5)
i
15
(10)
L_ 0
n
18
(12)
22
(13)
25
(14)
AMPS
(VOLTS)
M
Figure 3. Influence of Electrical Current on Oxidant Stream Composition
10
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los Alamos Technical Associates, Inc.
The catalytic reactions taking place on the electrode surfaces are not completely
characterized. Possible reactions, derived from the electrochemistry literature, are
shown in Table 4.
The generation of short-lived oxidants is supported by dye decolorization studies.
Bleaching of indigo trisulfonate dye has been proposed as a test for ozone (Bader and
Hoigne, 1981). Although this reaction is not specific for ozone, the reaction rate of the
dye with the
mixed-oxidant
solution suggests that
strong oxidant
components
are produced in addition to chlorine and shows why immediate mixing of the oxidant
solution with water to be treated is of the utmost importance (Figure 4). Very rapid dye
oxidation occurs within the initial minutes after the mixed-oxidant solution is produced.
TABLE 4
POSSIBLE OVERALL ELECTROLYTIC REACTIONS
Cell Location
Reactions
Feed Solution
NaCl - Na + + CI"
Anode
2 CI" • Cl£ + 2e
40H" * 0 2 + 2H 2 0 + 4e
O2 + O* - O3
H 2 0 + O* * H 2 0 2
Cathode
2H 2 0 + 2e • 20H" + H 2
0 2 + 2e - 20*
Between the Electrodes
This oxidation is produced even faster
hypochlorite alone.
Cl 2 + 20H" - H 2 0 + OCl~ + CI",
than that seen with either chlorine or
This empirical evidence supports the possible reactions of the
electrolytic cell shown in Table 4. Ozone is known to be very short-lived; the half-life
is less than one hour at pH 8 (Glaze, 1987) and is shorter in more alkaline conditions.
The shorter the time lag between generating the mixed-oxidant solution and contacting
it with contaminated water, the greater the capacity to oxidize the contaminants.
LATA's water treatment system is designed to utilize the short-lived oxidants; whereas,
11
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systems that provide storage tanks for the oxidants, which are to be mixed with water at
some later time, probably lose these components if generated.
The mixture of cogenerated oxidants provides a powerful tool for treating potable
water.
Ozone is known to be particularly effective in killing many types of microorga-
nisms. Hydrogen peroxide has been observed to increase the effectiveness of ozone in
removing organic substances during water treatment (Glaze, 1987). However, ozone has
a short lifetime and provides no long-term protection in treated water.
Chlorine
provides long-term protection against recontamination, and the presence of chlorine
shows
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measured colorimetrically.
6.
Effectiveness of Mixed-Oxidant Solution Against Microorganisms
The real test of a water treatment system is its effectiveness against microorganisms, particularly, waterborne human pathogens. The mixed-oxidant
solution
produced by LATA's water treatment system has been tested against a range of
microorganisms, including cysts and spores that are difficult to kill at usual levels of
municipal chlorination. To test the effectiveness of the freshly generated oxidant
solution, known volumes were added to suspensions of known microorganisms. The
treatment ratio, or ratio of oxidant solution to contaminated water, was chosen to
initially provide a low level of free chlorine at the lower end of the recommended range,
which is 0.2- to 4~rng/«, (USPHS, 1984) to test for effectiveness of the non-chlorine
species. With the prototype water treatment unit, the mixed-oxidant solution contained
sufficient chlorine; as little as one volume of oxidant solution was mixed with 1,000
volumes of contaminated water. All tests were carried out using standard methods of
analysis (Greenberg et al., 1980).
A series of six tests were performed. The first three tests were carried out using
electrolytic cells which were of different dimension and design and were equipped with
platinum electrodes. Also, the mixed oxidants were measured using nonspecific t e s t s first titration with sodium thiosulfate and later by total decolorization of indigo
trisulfonate dye.
The last three tests were made using the prototype unit shown in
Section 1, which was equipped with iridium oxide electrodes. Short-lived oxidants were
measured as the difference in the quantity of dye decolorized by a freshly generated
solution of mixed oxidants and by the same solution s.ged 24 hr in a filled, tightly closed
container.
13
:os Alamos Technical Associates, Inc.
A comparison was made of the effectiveness of the mixed-oxidant solution and
calcium hypochlorite against Escherichia coli (Table 5).
showed a more complete kill after
The mixed-oxidant solution
1 min; after 5 min, kill was complete in both
treatments.
Legionella pneumophila, the agent that causes Legionnaires' Disease, can survive
acceptable levels of chlorination for potable water systems and is quite difficult to kill
in evaporative cooling systems. The mixed-oxidant solution was more effective against
this organism than were similar concentrations of chlorine dioxide and hypochlorous acid
(Table 6).
TABLE 5
COMPARISON OF ESCHERICHIA COLI KILL BY MIXED-OXIDANT
AND HYPOCHLORITE SOLUTIONS
Initial
Oxidant*
(rng/g)
Cl£
(mg/G)
T0
Mixed Oxidant
(0.75 M NaCl; 9.5 A)
0.10
1.1
10 6
1.5 x 10 4
<1
Ca (0C1 2 ) 2
0.03
1.2
10 6
1.7 x 10 5
<1
Solution
E_^ eoli CFU/ml
T l min
T 5 min
* Oxidant measured by Na2S203 titration
TABLE 6
COMPARISON OF OXIDANTS' EFFECTIVENESS AGAINST
LEGIONELLA PNEUMOPHILA
Total
Oxidant
(mg/ml)
CI2
Concentration
(mg/g)
T0
Mixed Oxidant
(0.075 M NaCl,
20 V, 7 A)
0.75
0.49
1 x 10 7
1.9 x 10 6 1.5 x 10 4
3.0 x 10 2
C10 2
0.75
0.20
lxlO7
2.0 x l O 6
1.0 x 10 3
1.0 x 10 3
HOC1
0.67
0.23
1 x 10 7
8.0 x 10 6 6.0 x 10 6
1.0 x 10 6
Solution
14
L. pneumophila CFU/ml
T2 m j n
T5 m ! n
T15
min
, Los Alamos Technical Associates, Inc.
Giardia, a cyst-forming trophozoite that is parasitic in the mammalian gut, has
become a serious human health concern in the U.S. in recent years. The cysts can be
spread through fecal contamination of fresh water and enter municipal water treatment
systems where they have proved extremely resistant to conventional chlorination
treatment, especially at low temperatures. Several outbreaks of debilitating human
diarrhea in urban areas have been traced to Giardia contamination of municipal water
supplies. Newly proposed standards for U.S. drinking water specify less than one Giardia
cyst/100 ml.
To test the effectiveness of the mixed-oxidant solution against cysts, an experiment was carried out using Giardia muris, the mouse infective species. This species
is slightly more difficult to kill than the human pathogen, Giardia lamblia, and is easier
to maintain in culture as the mice are asymptomatic. Viability and infective potential in
Giardia is shown by the live trophozoites excysting under standard incubation conditions
that simulate passage through the mammalian gut. This test compared the number of
organisms able to excyst when contaminated water was treated with the mixed-oxidant
solution. The water conditions investigated were cold, clear water (3°C); warm, clear
water (20.5°C); and cold, turbid water (3°C). In order to assess the effects of other
oxidants, the free chlorine levels were kept very low. A minimum of 500 cysts were
inspected for each treatment. In the cases where kill was thought to be complete, all of
the approximately 4,500 cysts per treatment were scanned, for certainty.
The mixed-oxidant solution was able to kill all Giardia cysts in cold and warm clear
water, although the free chlorine concentrations were at the lower end of the municipal
treatment range (Table 7). The total kill in cold water at 0.40 mg/5 chlorine content is
especially significant as it suggests the effectiveness of short-lived oxidants.
The
concentration of cysts used in these tests was very high—about 4,500 cells r in 50 ml of
water. Under field conditions where contamination is less severe, complete kill even in
cold, turbid water seems feasible.
The final three tests discussed were performed with the pilot water treatment unit
shown earlier.
Based on the foregoing successes in killing even very resistant
microorganisms, these tests were designed to show whether a very small proportion of
the mixed-oxidant solution mixed with contaminated water could kill all microorganisms
and produce treated water that meets U.S. standards for drinking water for residual
chlorine and maximum recommended levels for sodium and chloride content. The EPA
standard for chlorine residual is 0.2- to 4-mg/B (EPA, 1986). The U.S. Public Health
15
,.os Alamos Technical Associates, Inc.
TABLE 7
EFFECT OF MIXED-OXIDANT SOLUTION ON GIARDIA EXCYSTATION
Tested Water
Condition
Temp. °C
Total
Oxidant
(mg/8)
Cl2
Concentration
(mg/8)
% Giardia Viability
/Excysted cells
inn\
X x
\ Total cells
J
T
T
T
0
10 min
30 min
Clear
3
0.40
0.20
0.44
0.22
40
44
24
41
0*
19
Clear
20.5
0.44
0.22
14
57
58
60
4
12
0*
3
Turbid
3
0.35
0.18
0.74
0.37
48
42
10
49
6
44
* All "4500 cysts of this treatment were examined to verify 100% kill.
Service recommends a maximum for chloride of 250 mg/8 (USPHS, 1984); the average
tnste threshold is 400 mg/6 (McKee and Wolf, 1978). The National Academy of Sciences
recommends a maximum sodium content in water of 200 mg/fi for persons on sodiumrestricted diets (NAS-NRC, 1973).
E^ coli were successfully killed within 10 min when one volume of mixed-oxidant
solution was added to 1,000 volumes of contaminated water (Table 8). The mixedoxidant solution was proded at 30 8/hr in 0.75 M NaCl using 13.4 A, 12 V dc. The
calculated concentrations of interest were chlorine, 0.3 mg/8; sodium, 17 mg/8; and
chloride, 12 mg/8, easily meeting the drinking water parameters.
Pseudomonas aeruginosa causes eye infections in humans. American Type Culture
Collection (ATCC) Strain #15442 was selected as a test organism because this strain has
been identified as having broad resistance to commercial germicides and is specified for
disinfectant testing by the American Organization of Agricultural Chemists (AOAC).
Cell suspensions of J\ aeruginosa were successfully killed within 10 min when one
volume of mixed-oxidant solution was added to 1,000 volumes of contaminated water
(Table 9). The oxidant production and final parameters of water quality were the same
as the preceding test, indicating successful treatment.
16
Los Alamos Technical Associates, Inc.
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Although not a human pathogen, Bacillus subtilis is a well-known spore forming
organism.
Spores, like cysts, are extremely difficult to kill by normal methods of
disinfection; spores can survive in boiling water and in levels of chlorine common in
municipal drinking water.
R subtilis ATCC Strain #19659 was selected as a test
organism because this strain is specified for use in the AOAC standard sporicide test.
The cells were grown on standard nutrient agar slants for 96 hr at 30°C.
Permanent
slide mounts were prepared, stained, and examined to verify the extent of sporulation,
which was estimated at 90% to 95% at 96 hr.
Because of the known resistance of the spores, suspensions of B. subtilis spores
were mixed with oxidant solutions over a wide treatment range. After 20 min, spore
populations were significantly reduced, but kill was not complete (Table 10). However,
one volume of mixed-oxidant solution in 500 volumes of contaminated water was
sufficient to kill all spores after 20 hr. As in the two tests above, the treated water met
drinking water parameters. This test will be repeated to determine the minimum,
required contact time, especially by the mixture of one volume of oxidant to
1,000 volumes of contaminated water. This interval must be taken into consideration
when designing a municipal water treatment system. Sufficient residence time must be
allowed for total disinfection before the water is used.
To summarize the effectiveness of LATA's unique water treatment system, the
mixed-oxidant solution is very effective against a spectrum of microorganisms, including
cysts and spores. Test organisms were selected to provide worst-case challenges. Virus
tests have yet to be conducted because of the need for special facilities. Although all
major human pathogens have not been tested, the results thus far indicate that potable
water can be produced using a mixed-oxidant solution and that the water will meet U.S.
drinking water standards and recommendations and aesthetic guidelines for residual
chlorine, coliform bacteria, chloride, and sodium content.
19
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REFERENCES
Bader, H. and J. Hoigne, "Determination of Ozone in Water by the Indigo Method," Water
Research, Vol. 15, pp. 449-456, 1981.
EPA (U.S. Environmental Protection Agency), "The Disinfection of Drinking Water,"
Prepared for Environmental Protection Agency, PB80-112964, 1979.
EPA (U.S. Environmental Protection Agency), "National Interim Primary Drinking Water
Regulations," Code of Federal Regulations, 40 CFR 141, July 1986.
Evans, F. L., Ill, "Ozone Technology: Current Status," In Ozone in Water and Wastewater
Treatment, F. L. Evans III, Ed., Ann Arbor Science, Publishers, Ann Arbor, MI, 1972.
Glaze, W. H., "Drinking-Water T r e a t m e n t with Ozone," Environ. Sci. Technol.,
Vol. 21 (3): 224 - 230, 1987.
Grayson, M. Ed., "Ozone," In Kirk-Othmer Encyclopedia of Chemical Technology,
Vol. 16, 3rd ed., John Wiley & Sons, New York, N.Y. 1981.
Greenberg, A. G., ed., "Standard Methods for the Examination of Water and
Wastewater," 15th ed., American Fublic Health Association, 1980.
McKee, J. E. and H. F . Wolf, "Water Quality Criteria," 2nd ed., California S t a t e Water
Resources Control Board, Publication 3A:160, Reprinted July, 1978.
NAS-NRC (National Academy of Sciences - National Research Council), Environmental
Studies Board, "Water Quality Criteria," EPA Report EPA-R3-73-033. Washington, D.C.,
1973.
Pendergrass, A. M., H. F. Gram, M. E. Muller, P. A. Rink, and M. W. Talley, "Electrolytic
Sterilization of Potable Water on Shipboard," Final Technical Report, C o n t r a c t No.
N00167-85-C-0001, SBIR, 1985.
USPHS (U.S. Public Health Services), "Drinking Water Standards," Code of Federal
Regulations 42 CFR 72, July 1984.
21
The Chemistry of Water Treatment Processes Involving
Ozone, Hydrogen Peroxide and Ultraviolet Radiation
William H. Glaze, Joon-Wun Kang and Douglas H. Chapin
Environmental Science and Engineering Program
School of Public Health, University of California
Los Angeles, CA 90024
Abstract
Advanced oxidation processes are defined as those which
involve the generation of hydroxyl radicals in sufficient
quantity to affect water purification. The theoretical and
practical yield of OH from O3 at high pH, O3/H2O2, O3/UV and
H2O2/UV systems is reviewed.
New data is presented which
illustrates the importance of direct photolysis in the O3/UV
process, the effect of the ^02:03 ratio in the O3/H2O2
process, and the impact of the low extinction coefficient of
H202 in the H2O2/UV process.
Introduction
This paper will summarize the chemistry of several water
treatment processes involving combinations of ozone, hydrogen
peroxide and ultraviolet radiation. The purpose is to show
that these processes have much in common mechanistically, but
there are significant enough differences to make one or the
other more practical depending on water quality and water
treatment goals.
Advanced Oxidation Processes
Ozone has been used as a chemical reagent, an industrial
chemical, and an oxidant for water treatment for over eight
decades (1) . Ozone is known to be a powerful oxidant and
disinfectant, with a thermodynamic oxidation potenti'al that
is the highest of the common oxidants. In principle, ozone
should be able to oxidize most inorganic substances to their
highest stable oxidation states and organic compounds to
carbon dioxide and water. In actual practice, however, ozone
is quite selective in its oxidation reactions. In organic
chemistry it is most useful for cleavage of multiple bonds
and aromatic systems, but even in these cases the rates of
oxidation may be quite slow for water treatment applications.
For example, ozone reacts slowly with many types of water
contaminants such as alicylie taste and odor compounds as
geosmin and MIB (2), aliphatic halides such as the THMs
(3,4), and unactivated aromatics such as chlorinated benzenes
(4) . In water treatment, ozone has been most successful for
enhancing the pleasant taste of water, for aiding coagulation
and filtration processes, and as a first barrier to microor1
ganisms.
There is, however, a new dimension emerging in the use of
ozone in water treatment. In several laboratory and pilot
scale studies ozone is now being combined with hydrogen
peroxide and ultraviolet radiation to produce results which
have not been possible with ozone alone. The literature is
replete with examples of 03/UV and 0 3 /H 2 0 2 studies in which
inorganic and organic substances have been oxidized much more
effectively than one can accomplish with ozone or any other
common oxidant. We now understand, based on the accumulation
of new information on the basic chemistry of ozone, that the
success of these new processes is due to the intermediacy of
the hydroxyl radical which is common to each system.
We
shall refer to systems such as O3/UV and 0 3 /H 2 0 2 as "Advanced
Oxidation Processes" and include in this category other
processes which generate the hydroxyl radical, namely ozone
at high pH values, hydrogen peroxide with UV radiation, and
ozone or hydrogen peroxide with other hydroxyl radical
initiators such as metals and metal oxides.
Historical Background
Prengle and coworkers at Houston Research Inc. (HRI) were the
first to see the commercial potential of the O3/UV system.
HRI showed that O3/UV enhances the oxidation of complexed
cyanides, chlorinated solvents, pesticides, and miscellaneous
group parameters such COD and BOD (5-8) . Subsequently, the
process was also commercialized by Westgate Research of Los
Angeles (now ULTROX) where Zeff and coworkers further
extended the applications of the process (9,10). Glaze and
coworkers, especially Peyton, have examined the O3/UV process
for oxidation of a number of halogenated micropollutants
(3,11) and THM precursors (12) and have carried out basic
studies to elucidate the mechanisms of the process (13) .
Several other groups have used the O3/UV process for oxidation of a variety of organic pollutants (14-17) and the
process has been taken to pilot scale for a number of
applications (5,18, 19).
The 03/H202 system was investigated early by Nakayama et al.
(20) and Hango e_t al. (21) for wastewater treatment, and more
recently by Bollyky (22), Brunet et al.(23) and Duguet et al.
(24) for drinking water treatment. Duguet et al. showed that
addition of peroxide enhanced the efficiency of oxidation of
several organic substances, THM precursors, and also increased the rate of ozone transfer. Studies are proceeding
currently in several laboratories including our own (25), and
the process is being taken to pilot scale by the city of Los
Angeles for removal of tri- and tetrachloroethylene in
groundwater.
2
Hydrogen peroxide with ultraviolet radiation was studied by
Berglind et aJL. (26) for the oxidation of humic substances,
methyl isoborneol, 3,4-benzopyrene
(sic), chloroform and
bromodichloromethane.
The process is the subject of a U.S.
patent (27) but little further work has been reported.
Mechanisms of Advanced Oxidation Processes
Not all of the advanced oxidation systems have been well
studied and their mechanisms are not fully elucidated.
It
appears, however, that all involve the generation of the
hydroxyl radical.
The present view is that the oxidizing
capability of these systems is differentiated from other
common oxidants such as chlorine, chlorine dioxide, etc.
because of the very high reactivity of this radical.
OZONATION AT HIGH pH VALUES
Hydroxyl radicals were postulated by Weiss (28) as intermediates in the base catalyzed decomposition of ozone.
Indirect evidence for OH radicals was presented by Hoigne and
Bader (29) who showed that the mechanism of ozonation seemed
to change at high pH values. The relative rate constants for
high pH ozonation of pairs of organic compounds were found to
be the same as those for reaction of the same compounds with
hydroxyl
radicals generated from radiolysis of water.
Hoigne's group (30-32) and independently, Hart et al.(33-34)
used advanced spectro-kinetic methods to elucidate the
mechanism by which ozone decomposes in water.
A complex
chain mechanism was revealed that involves a series of
single-electron and atom transfer processes (Figure 1) and
the intermediacy of OH radicals. Staehelin and Hoigne showed
that a variety of substances can initiate the chain including
hydroxide, hydroperoxide, formate and ferrous ions,, and even
humic substances
(35).
Although direct spectroscopic
evidence for the OH radical in aqueous ozone systems has not
been found, the indirect evidence is overwhelming that OH is
the key reactive intermediate when ozone decomposes in water.
In very pure water OH reacts with ozone so that the chain
propagating steps shown in the circle in Figure 1 can repeat
again and again.
Hundreds of ozone molecules may be decomposed by a single initiation step. The result is that ozone
can have a very short half-life in distilled water at pH 7
(36).
In the presence of common water contaminants, for
example bicarbonate, carbonate and the organic constituents
of humic substances, the cycle can be broken by trapping of
the hydroxyl radical, and of course, the chain may also be
broken by radical-radical coupling processes.
3
Rate constants for reaction of OH with most substances are
extremely large indicating that the reactions are very fast;
some occur almost every time an OH radical collides with a
molecule of the substance.
One of the major water contaminants, bicarbonate will trap hydroxyl radicals with such
efficiency that the half-life of ozone in distilled water at
pH -7 increases from about 10 3 seconds in distilled water to
104 seconds in 2 iH HC0 3 ~ (36).
If organic micropollutants are present when ozone decomposes
they too will react with hydroxyl radicals, but they must
compete with all of the other OH traps present.
If the
concentration of the micropollutant organics is in the
micromolar range or below, they may be at a distinct disadvantage compared to matrix contaminants such as bicarbonate
or humic materials, which may be present at concentrations
several orders of magnitude higher (35).1
As Hoigne and coworkers have observed, the mechanism of the
reaction of ozone with another substance M may involve both
direct reactions of M with ozone and reaction of M with OH
radicals, even if the pH of the system is near neutral (35).
This is because OH-promoters such as hydrogen peroxide and
superoxide ion 0 2 ~ are formed in the course of direct
ozonation processes. Also, there may be contaminants in the
water which act as promoters. Thus, when ozone reacts with
substances in natural waters it is almost surely reacting by
a combination of direct O3 and OH pathways, the relative
proportions of which will depend on the various contaminants
present or added. The mechanism may even become more radical
in character as the reaction proceeds.2
At higher pH values there is an important factor that works
against the effectiveness of ozonation processes. Hoigne has
pointed out that increasing the pH will not necessarily
increase the rate of OH radical destruction of a substrate
because of enhanced trapping effects (29) .
At p'H values
1
In the O3/H2O2 oxidation of TCE in the presence of 300
mg/L (as CaC03) of bicarbonate, we calculate that only about 4%
of the transferred ozone is utilized for the destruction of 90%
of 600 ug/L of TCE (25).
2
This may explain apparent discrepancies in the literature
\on such questions as the destruction of THM formation potential
\by ozonation, where some workers see an enhancement of THMFP by
ozone and others do not (37). Under some conditions OH radicals
apparently are produced by initiators present in the water and
these radicals may hydroxylate benzenoid species to form THM
precursors. Under other conditions the radicals are either not
formed in such abundance or are quenched by other species (38).
4
greater than 10.3 carbonate is a more prevalent species than
bicarbonate and the rate constant of OH with carbonate is
over twenty times greater than with bicarbonate.
On the
other hand, ozonation is not commonly carried out at pH
values above 10.3, so the role of carbonate may not be very
severe as these considerations indicate.
Further studies are needed to carefully document the advantages and disadvantages of using high pH conditions to
enhance ozonations in waters with different alkalinity
values. Figure 2 shows data from a study being carried out
in our laboratory where the rate constant for ozonation of
trichloroethylene is measured in a CSTR treating a high
alkalinity ground water from a well in North Hollywood
(alkalinity 200 mg/L as CaC03; pH 7.3; DOC 1.1 mg/L; Fe, Mn
less than 0.1 ppm). As figure 2 shows, adjusting the pH from
4 to 10 has little effect on the destruction of TCE. We
suspect that this behavior may be due to a cancellation of
the promoting effect of hydoxide ion and the scavenging
effect of carbonate vs. bicarbonate, and therefore may not be
typical behavior for a water of lower alkalinity. However,
the results illustrate that rate enhancements from pH changes
below 10 or 11 may be minimal.
OZONE WITH HYDROGEN PEROXIDE
Hart and coworkers (33) and Staehelin and Hoigne (30) showed
that the conjugate base of H2O2 can initiate the ozone
decomposition cycle by a single electron transfer process
involving the conjugate base of hydrogen peroxide H02~:
H0 2 "
+
03
>
H0 2
+
O3"
(1)
This initiates the decomposition of ozone resulting, in the
formation of hydroxyl radical.
Exploiting this effect,
Duguet et al. (24) showed that the efficiency of color
removal by ozone is accelerated by hydrogen peroxide. The
dependence on the concentration of peroxide suggests that
H2O2 is acting as a scavenger at high concentrations. In
recent studies in our laboratory we are exploring the O3/H2O2
system with several substrates including chloroethenes and
several taste and odor compounds. Figure 3 shows rate data
for the destruction of tetrachloroethylene in a ground water
from the same area in Los Angeles from which the sample was
taken referred to earlier. The alkalinity of this water is
somewhat\ higher than the other (300 mg/L at CaC03) but other
water quality parameters are similar. In these experiments,
to be reported in more detail later, the peroxide and ozone
were simultaneously fed into the reactor, ozone and peroxide
residuals were generally below 0.1 ppm, and ozone utilization
5
greater than 90%). The pseudo first-order rate constants
show a hyperbolic dependence on peroxide with a maximum at a
ratio of about one mole of peroxide per mole of ozone. This
is the function expected if peroxide acts as a promoter as
well as an OH scavenger.
Indeed, it is know that peroxide
will act as an OH radical trap as well as an initiator. The
rate constant for reactions 2 and 3 are 2.7 x 10 7 M" 1 s"*1 and
7.5 x 10 9 M" 1 s" 1 respectively (39):
H202
+
OH
H02
+
OH
*2
>
02~
+
H20
+
H+
(2)
>
OH"
+
02~
+
H+
(3)
It should be noted, however, that superoxide ion 0 2 ~ is also
formed in equations 2 and 3, and since superoxide also
promotes the decomposition of ozone it is not clear why
peroxide inhibits the decompositon of TCE at high H 2 0 2
levels.
If one assumes that superoxide reacts primarily by
some other pathway than with ozone, then one may derive
equation 4:
-d(ln[M]/[M0])/dt
=
k0
(4)
where
ko
=
*M k l K per[ H 202n°3]/[ H + 3
k M [M] + (k2 + k 3 Kp e r /[H + ])[H 2 0 2 ] +
kitSj.]
K p e r is the dissociation constant of hydrogen peroxide (1.6 x
lo
) i * M ^ s t n e r a t e constant for reaction of OH with
substrate, in this case TCE or PCE, and
S^ symbolizes other
matrix components that trap OH with rate constants k^, the
most important of which are dissolved organic carbon (humic
substances),bicarbonate or carbonate ion (36).
Alternatively, the shape of Figure 3 may be related to the
fact that the reaction is being carried out in a CSTR. That
is, at high peroxide doses the rate constant is mass transfer
limited. >
In any case,\ the results of the laboratory scale tests on the
oxidation of\TCE and PCE are so encouraging that the city of
Los Angeles Ys currently sponsoring pilot scale tests to
evaluate the large scale potential of the 0 3 / H 2 0 2 system for
remediation of contaminated ground water in the San Fernando
Valley (40).
OZONE WITH ULTRAVIOLET RADIATION
6
The photolysis of ozone in wet air produces hydroxyl radicals
by a two step process (41):
03
+ h y (A< 310 nm)
O (XD) +
H20
>
>
OH
02 +
+
OH
0 ^D)
(5)
(6)
Some workers assumed (8) that photolysis of ozone in water
would proceed by a similar pathway? however Taube (42)
showed, and more recently Peyton and Glaze (13,18) confirmed
that this is not the case. Rather, hydrogen peroxide is
formed in a process where OH radicals, if formed at all, do
not escape from the solvent cage. The overall reaction is
03
+
h-y
+
H20
> H202
(7)
Equation (7) would appear to say that the O3/UV and 0 3 /H 2 0 2
processes are one and the saine: in the former one is merely
forming hydrogen peroxide in situ, rather than adding it from
an external source. Indeed, for some substrates that is the
case as will be discussed below. For other substrates which
absorb ultraviolet radiation the O3/UV process can be much
more. This is illustrated by the O3/UV oxidation of tetrachloroethylene, first reported by Peyton et a_l. (3) and more
recently explored in a ground water matrix by our group in
Los Angeles.
Tetrachloroethylene (PCE) absorbs ultraviolet radiation at
254 nm only weakly, but sufficiently so that direct photolysis is a significant contributor to the overall decay of
PCE when the compound is exposed to ozone and 254 nm radiation in a CSTR reactor. Figure 4 is a plot of pseudo firstorder rate constants for a series of runs where the ozone
dose was varied while keeping the UV dose constant. For a
given UV dose the data approximately fit a simple relationship
k0 = kp
+
koxDn
=
kp
+
k'
(8)
where kp is the direct photolysis constant, k o x is related to
the constant for OH radical reaction with PCE, D is the ozone
dose rate, and n is a coefficient with a value near unity
(3). The value of k p obtained from an experiment in which D
was zero (only oxygen was used) is in good agreement with the
extrapolated value from Figure 4.
Similar experiments^ were carried out with trichloroethylene
(TCE) with markedly\different and revealing results. Figure
5 shows that the 03/UV oxidation of TCE is only weakly
dependent on the UV flux.
The extrapolated value at zero
ozone dose is in good agreement with the rate constant
7
obtained in the "UV only" experiments.
The TCE and PCE data from these experiments demonstrate what
Prengle and coworkers claimed years ago(8): that the 03/UV
process is, at the same time, an oxidation process and a
photolysis process.
Figure 6 illustrates the various
elements of the process including direct ozonation, decomposition of ozone (OH radical chemistry) and photolysis of M
and hydrogen peroxide.
The relative importance of these
processes will depend on an extraordinary number of factors
including: the intensity and wavelength of the UV radiation,
the ratio of 03:UV doses, the concentration of M, promoters
and radial traps, and others.
When a substance absorbs strongly in the UV region large
fluxes of UV radiation will accelerate the destruction of the
substance. This is the case for PCE and presumably for other
UV absorbing substances such as aromatic halides. For some
photolytically labile substances such as some pesticides, kp
is so large that little is to be gained from using ozone.
On the other hand, when the substance of concern is not
photolyzed directly with much efficiency, the use of UV
radiation to generate hydrogen peroxide makes little sense.3
In such cases it is preferable to add hydrogen peroxide from
an external source. Metering of peroxide into a water stream
is a trivial task compared to the use of UV lamps with their
attendant problems of clouding and flux decay especially for
large water treatment plants. Our view is that both processes should be considered in a feasibility study, but except
when direct photolysis is a major factor, the O3/H2O2 process
is heavily favored.
HYDROGEN PEROXIDE WITH ULTRAVIOLET RADIATION
In principle, the most direct method for the generation of
hydroxyl radicals is through cleavage of hydrogen peroxide, a
relatively inexpensive and readily available chemical
intermediate.
Photolysis of hydrogen peroxide is known to
yield hydroxyl radicals by a direct process, i.e. with a
quantum yield of two OH formed per quantum of radiation
absorbed (43):
3
Many applications of the ozone/UV process, including some
current commercial realtors, use UV intensities which are
extremely high and costly^ There is an optimum ratio of UV flux
(in Einsteins/min):ozone dose (in moles/min) for each system, but
in the absence of much direct photolysis the ratio is probably
less than 0.5.
In a study of the O3/UV oxidation of THM
precursors the optimum ratio was 0.3 (18).
8
H202 +
hV
>
OH
+
OH
(9)
Unfortunately, the molar extinction coefficient
of hydrogen
peroxide at 254 nm is only 19.6 M _ 1 s"1 (43), which is exceptionally low for a primary absorber in a photochemical
process. By comparison, the
value for ozone is 3300 M - 1
-1
cm .
This means that in order to generate a sufficient
level of OH radicals one must have a rather high concentrtion
of hydrogen peroxide in the medium.
Figure 7 shows data from a kinetic study where hydrogen
peroxide is being metered into a CSTR at a rate of 10 mg/min
while photolyzing the solution with three 13 watt low
pressure mercury arc lamps (greater than 90% UV energy at 254
nm) . Trichloroethylene, which was spiked into the original
solution at approximately 500 ppb, and residual hydrogen
peroxide were monitored as the reaction proceeded. Figure 7
shows that TCE is decomposed at a reasonable rate compared to
the 03/H202 data in Figure 3, but hydrogen peroxide accumulates to unacceptable levels. We conclude that the H202/UV
is unlikely to be a practical process for drinking water
treatment until this problem is solved; however, for wastewater treatment or other purposes it might be useful.
SUMMARY OF HYDROXYL RADICAL GENERATING PROCESSES
Table 1 is a summary of the chemistry involved in the
generation of hydroxyl radicals from the four processes
considered in this review. As noted above, the stoichiometric yield of hydroxyl radicals is greatest from the
photolysis of hydrogen peroxide. As Table 2 shows, however,
ozone photolysis yields more radicals in practice because of
the higher molar extinction coefficient of ozone compared to
hydrogen peroxide.
Of the four processes, the 0 3 /H 2 0 2 process should have a high
yield of OH radicals, is most amenable to adaptation in
existing water treatment plant designs, and should be
relatively cost effective.
The use of ozone at high pH
values may be comparable in cost/effectiveness but there is
little field data on this process. The O3/UV process will be
difficult to adopt on a large scale but may be useful for
small water and waste water treatment plants, particularly
when the substrates of concern are strong UV absorbers.
Acknowledgement
The author is grateful to the City of Los Angeles Department
of Water and Power for support of this work, partially with
funds supplied by the U.S. Environmental Protection Agency
through Cooperative Agreement CR-813188, and to E. Marco
Aieta, Rhodes Trussell and Carol Tate of James M. Montgomery
9
Consulting Engineers for useful discussions.
The original
work was performed by Joon-Wun Kang and Douglas Chapin. This
article has not been subjected to review by EPA. Therefore,
it does not necessarily reflect the views of the agency, and
no official endorsement should be inferred.
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\
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*
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13
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14
I
LEGEND OF FIGURES
FIGURE 1.
Scheme showing the principal species in the decomposition of ozone in pure water initiated by hydroxide ions
(after Staehelin et al., reference 32) .
FIGURE 2.
Effect of pH on the ozonation of trichloroethylene
(TCE) in North Hollywood Well No. 26 water. Bicarbonate alkalinity: 200 mg/L; TOC 1.1 mg/L; pH adjusted upwards with sodium
hydroxide, downward with hydrochloric acid; 70 liter CSTR with
ozone from pure oxygen.
FIGURE 3. Effect of hydrogen peroxide on the pseudo first-order
rate constants of oxidation of TCE in North Hollywood Well No. 14
water. Alkalinity: 300 mg/L; 70 liter CSTR with ozone from pure
oxygen, 03 scale is dose rate, utilization > 90%.
FIGURE 4.
Effect of ozone and UV dose rates on the photolytic
ozonation of perchloroethylene (PCE) in North Hollywood Well No.
14 water.
Rate constants (s _1 ) multiplied by 10^; UV dose in
watts/L at 254 ran calibrated by chemical actinometry.
FIGURE 5.
Effect of ozone and UV dose rates on the photolytic
ozonation of trichloroethylene (TCE) in North Hollywood Well No.
14 water.
Rate constants (s _1 ) multiplied by 10^; UV dose in
watts/L calibrated by chemical actinometry.
FIGURE 6.
Schematic diagram of the elements of mass and photon
transfer, and chemical processes involved in the O3/UV process.
FIGURE 7.
Pseudo first-order plot for destruction of TCE by
H 2 0 2 /UV process in North Hollywood Well No. 14 water. Reaction
carried out in 70 liter CSTR with feed rate of 10 mg H 2 0 2 per
minute. Residual peroxide by horseradish peroxidase fluorimetry
(44).
15
TABLE 1
THEORETICAL AMOUNTS OF OXIDANTS AND UV
REQUIRED FOR FORMATION OF HYDROXYL
RADICAL IN OZONE-PEROXIDE-UV SYSTEMS
Moles of Oxidant Consumed
per Mole of OH Formed
SYSTEM
03
UV X
H202
(0.5) 2
OZONE-HYDROXIDE ION 3
1.5
OZONE-UV
1.5
0.5
OZONE-HYDROGEN PEROXIDE3
1.0
—
0.5
•'-Moles of photons (Einsteins) required for each mole of OH
formed; 2 Hydrogen peroxide formed in situ (13,42); 3 Assumes that
superoxide formed in primary step yields one OH radical per 0 2 ~
which may not be the case in certain waters.
16
TABLE 2
THEORETICAL FORMATION OF HYDROXYL RADICALS FROM
PHOTOLYSIS OF OZONE AND HYDROGEN PEROXIDE
MOLAR ABSORBTIVITY
254 (M-1 cm" 1 )
STOICHIOMETRY
OH RADICALS FORMED 1
PER INCIDENT PHOTON
H202
20
H202
> 20H
0.09
03
3300
30 3
> 20H
2.00
1
Assumes 10 cm pathlength; quantum yield as predicted from
stoichioiaetry; [0 3 ] and [H 2 0 2 ] at 1 x 10~ 4 M.
17
9.5
-8.5
I n (TCE/TCEo)
-1 -
o
PH 18
>K
PH
a
PH 4
-1.5
-2.5
18
15
Tiwe ( n i n )
25
2
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C
ADVANCED OXIDATION PROCESSES FOR TREATMENT OF GROUNDWATER
CONTAMINATED WITH TRICHLOROETHYLENE AND TETRACHLOROETHYLENE:
LABORATORY STUDIES
William H. Glaze and Joon-Wun Kang, Environmental Science &
Engineering Program, School of Public Health, UCLA, Los
Angeles, California 90024
ABSTRACT
The
oxidation
ethylene
(or
of
trichloroethylene
perchloroethylene
(TCE)
-
PCE)
and
was
tetrachlorostudied
in
a
stirred sparged reactor with various dose rates of ozone and
hydrogen peroxide.
The results show that hydrogen peroxide
accelerates the oxidation of TCE and PCE spiked into a ground
water taken near Los Angeles, California.
dose rates above 0.7
transfer limited.
At peroxide:ozone
(w/w) the process appears to be mass
The presence of high levels of bicarbonate
ion in the groundwater is shown to significantly lower the
efficiency
of TCE
and
PCE removal
by the 0 3 /H 2 02 process
suggesting that softening prior to oxidation may improve the
process even further.
INTRODUCTION
Groundwater
contamination
tetrachloroethylene
by
trichloroethylene
(TCE) ,
(PCE), and other industrial and agricul-
tural chemicals is now a matter of international concern. The
U.S.E.P.A. recently proposed Maximum Contaminant levels for
TCE and
seven
other
contaminants
in drinking water and a
standard for PCE may be\forthcoming (1).
the
Safe
Drinking
Water^ mandate,
EPA
In accordance with
also
specified
two
technologies as Best Available Technology (BAT) for treatment
1
of water containing these substances:
granular activated carbon filtration.
air stripping and
Some have objected to
these technologies on the basis that they merely transfer the
problem from one medium (water) to another (air or GAC).
Oxidation processes offer the option, at least in principle,
of
completely
destroying
organic
contaminants.
Of
the
't
oxidants currently available, ozone is attracting the most
attention.
This is due to its high thermodynamic oxidation
potential (2.07 volts) and the apparent lack of hazardous byproducts (2) .
However, neither ozone nor any other oxidant
has proven itself as a BAT process for removing synthetic
organic compounds from ground water.
iency and
to enhance
To overcome this defic-
its effectiveness
for oxidation of
organics, modifications of traditional ozonation have been
investigated in our bench-scale laboratory tests.
Each of the processes studied, which we refer to as advanced
oxidation processes
hydroxyl
radical
(3,4),
involve the generation' of the
(OH), a very
active
intermediate which
generally has far greater oxidizing power than ozone.
constants
for
reaction
of
OH
with
organic
species
Rate
are
commonly in the range of 10?-1010 M _ 1 s _ 1 (5).
Four types of advanced oxidation processes are being studied.
These include: ozone at various pH values (03/pH), ozone with
2
hydrogen peroxide (03/H202)/
ozone with ultraviolet radia-
tion (O3/UV), and hydrogen peroxide with ultraviolet radiation (H202/UV\.
This paper describes an evaluation of the
first two processes (03/pH and C>3/H202) for the oxidation of
TCE and PCE in a contaminated groundwater obtained from two
City of Los Angeles Department of Water and Power (LADWP)
North Hollywood wells.
The results, combined with pilot-
scale studies described in the following paper (6), show that
the ozone:hydrogen peroxide processs should be considered as
a candidate for Best Available Technology for TCE/PCE treatment.
EXPERIMENTAL
Reaction apparatus.
Figure 1 shows the schematic diagram of
the 03/H202/UV experimental system.
Ozone was generated from
oxygen with a single tube OREC generator (corona discharge
type), typically at a flow rate of 1.0 L/min and at a tube
current setting so as to give a desired dose rate.
panel valves (needle, 3-way,
Control
and 5~way valve) allowed one to
r
divert the ozone stream through two tandem bubblers for ozone
analysis or alternately divert the ozone off-gas from the
reactor through the same bubblers.
When the analysis system
is not in use, ozone off-gas is thermally decomposed before
\
\
exit into a vented hood.
All fittings, valves, and tubing
\
were limited to stainless steel,\ glass, and teflon.
The
reactor used in these studies is \a cylindrical 70 liter
(liquid volume) CSTR designed according to the principles
3
described by Yocum (7).
The reactor is a 36 inch high by 13
inch O.D. stainless steel vessel with a built-in sparger for
ozone
introduction,
a
variable
speed
stirrer
(usually
operated at 500 rpm), internal baffles at the quadrants to
facilitate mixing, and four 2-inch diameter symmetrically
located circular ports into each of which can be fitted a
quartz tube for a UV lamp.
The UV ports were sealed off with
stainless steel plates in this study.
Test Samples.
Groundwater used for all of the 03/H 2 0 2 runs,
except to study the effect of bicarbonate alkalinity, was
collected from the City of Los Angeles Department of Water
and Power North Hollywood Well No. 14 or Well No. 26.
The
water was transported to UCLA in a 55-gallon polyethylene
drum.
Typical analysis of the groundwater, for Well No. 14
or 26 respectively, was:
alkalinity, 300 mg/L and 200 mg/L
(as CaC0 3 ), respectively; pH 7.2-7.4; TCE and PCE, 50 and 5
ug/L, respectively; and TOC 1.1 mg/L.
Analytical methods.
Ozone is analyzed in the gas phase by
trapping in an borate-buffered potassium iodide solution (8).
The
concentration
of
resulting
iodine
is
determined
colorimetrically at 352 ran on a Spectronic 710 spectrophotometer (Bausch & Lomb, Rochester, N.Y), \which is previously
calibrated by standard iodine solution. - Ozone in the liquid
phase is determined by the indigo method (9) .
4
Each ozone
sample was added to a 40 ml vial which contained an appropriate
stock
concentration
reagent
expected.
of
depending
potassium
on
the
indigo
trisulfonate
concentration
of
ozone
The absorbance difference between sample and blank
was measured at 600 nm.
An extinction coefficient of 2 0,000
L Mol"1 cm"1 (9) was used for calculation of the concentration of residual ozone.
Concentration of residual hydrogen
peroxide
either
was
Masschelein
fluorescence
determined
(10)
or
method
the
the cobalt method
horseradish
described
feeding
by
by
solution
of
peroxidase-catalyzed
Lazrus,
(usually
et
al. (11).
Hydrogen
peroxide
0.12
N) was
prepared
from a reagent grade 30% stock solution
(Fisher
Scientific) and v/as analyzed by the AOAC Method
(12).
A
method for analysis of TCE and PCE modified from EPA Method
501.2 consisted of microscale liquid-liquid extraction using
pentane or hexane (American Burdic & Jackson brand for THM
analysis) with a water to extractant volume ratio of 2:1.
Two different gas chromatograph
TCE/PCE analysis.
(GC) models were used for
Most of the analytical work was performed
on a Varian 3700 GC with Ni 6 3
electron capture detector
(ECD), a glass column (12' x 1/4" O.D., 10% squalane), and a
5% methane and 90% argon gas mixture as carrier gas.
A
Schimadzu Chromatopac C-R3A electronic/printer integrator was
connected to the Varian GC to collect data and compute sample
concentrations.
Later sample analyses were carried out on a
Perkin-Elmer Model 8500 GC using splitless injection and a
Ni 6 3 ECD.
A fused silica wall coated open tubular column
(DB-5, 30 m x 0.32 mm I.D.) supplied by J&W Scientific was
used.
Oven temperature was programmed from 40°C to 220°C at
10°C/min.
Helium gas (99.995%) and 5% methane/95% argon gas
mixture were used for carrier and make-up gas, respectively.
Hexane was used as extractant for this splitless injection
mode to optimize the solvent effect.
used
for
all
GC
analyses
was
The internal standard
1,2-dibroraopropane
(DBP) .
Quality control features of EPA Method 501.2 were used for
preparation
of
calibration
standards
for
the
extraction
method.
Procedures.
For each run, groundwater was pumped into the
CSTR and filled up to a guide level of 70 L.
Saturated
solutions of TCE and PCE were prepared separately by stirring
pure
compounds
in
contact
with
distilled
water.
After
analysis, these stock solutions were used to prepare aqueous
solutions of known concentrations of TCE and PCE that were
r
spiked into the reactor so as to give target initial TCE and
PCE concentrations of approximately 500 and 50 ug/L, respectively.
After a few minutes of mixing, oxygen gas was
introduced into the CSTR at a desired flow rate.^
To detect
any system leaks, another rotameter was installed\at the gas
stream exit.
Flow rate of the exit stream was then\ compared
to the inlet flow rate.
At time zero, ozone generation was
started using pre-set conditions for the ozone generator.
6
If
hydrogen peroxide was included
in the run, it was added
simultaneously with the ozone using a calibrated feed pump
supplied by Mec-O-Matic Company.
For some runs, the pH of
the groundwater sample was adjusted prior to oxidation using
either a NaOH solution or H 2 S0 4 solution.
Duplicate samples of the CSTR contents were taken for TCE and
PCE analysis at five-minute intervals, beginning at time zero
and ending 25 minutes later.
Two drops of 1% sodium thiosul-
fate were present in each 4 0 ml vial before the groundwater
samples were added.
The vials were filled head-space free
and sealed with screw caps with PTFE-coated liners.
Samples
were stored in a refrigerator (organic free) at 4°C prior to
extraction.
measure
Samples were taken at the same time intervals to
concentrations
of
peroxide as described above.
residual
ozone
and
hydrogen
Ozone off-gas was trapped in
the BKI-contained bubbler and the amount of ozone consumed in
the reactor was calculated from the concentration of ozone in
r
the feed gas and the concentration of ozone in off-gas.
Measurement of Ozone Kass Transfer for CSTR.
The reactor was
filled with water taken from North Hollywood well No. 14 and
ozone flow started at the same flow rate as before (1.0 \
L-min -1 ).
Samples were withdrawn
sequentially
from the
reactor and quenched with a solution of indigo trisulfonate\
then the absorbance of the solution was measured as usual."
7
RESULTS & DISCUSSION
Ozone system.
Hoigne and Bader have reported that the rate constants for
direct reaction of ozone with TCE and PCE are 17 ± 4 M _ 1 s-1
"and <0.1 M" 1 s"1 respectively (13). This means that a steady
state concentration of 5 mg/L (1 x 10~ 4 M) of ozone would be
required for 95% oxidation of TCE within a thirty minute
contact time, assuming pseudo first order kinetics.
For PCE
the rate is expected to be at least an order of magnitude
slower.
It might
be concluded, therefore, that direct
reaction of ozone will not be sufficiently rapid to be a
practical decontamination method for PCE but for TCE it may
be worth exploring.
It is now recognized, however, that calculations based on
such basic rate data are of little value in determining the
prospects of using ozone for water treatment objectives (14).
Few ozonation processes occurring in a natural water occur
only by
interest.
direct
reaction of ozone with the substrate of
In natural waters ozone reacts by two mechanisms:
direct reaction of the O3 molecule, for example, by addition
of O3 to the carbon-carbon double bond of TCE or PCE, and
reaction with the hydroxyl radical, formed by the decomposition of ozone (14). Both types of reactions are expected to
occur in natural waters where there are naturally occurring
8
electron transfer agents present
tions)
that
initiate
ozone
(or formed during ozona-
decomposition,
such
as 0H~,
transition metal ions, hydrogen peroxide, superoxide, etc.
(Figure 2) .
Also, most common water impurities such as
bicarbonate, carbonate, and organic material react with OH
radicals and act as scavengers, and some react with molecular
ozone.
Thus, the relative importance of direct vs. radical
reactions must be determined experimentally for each source
water.
Table 1 is a summary of pseudo first order rate constants for
the ozone runs performed on groundwater samples from the
North Hollywood Well No. 26 spiked with 500 and 50 ug L"1 of
TCE and PCE respectively.
The initial alkalinity of the
source water is 200 wg/L (as CaC03) and the TOC value is 1.1
lag/L.
Figure 3 is a plot of typical runs for TCE, showing
the pseudo first order nature of the process.
It is interesting to note that increasing pH from 4 to 10 has
little effect on the destruction of TCE as shown by the data
in Table 1.
This may be due to the important role played by
the bicarbonate
positive
and
oxidation.
ion
in
negative
the water, which
effects
on the
can have both
rate
of
substrate
Bicarbonate and carbonate ions react with OH by
electron transfer reactions (10) and (11) shown in Table 2.
9
Since the rate constant of OH radicals reacting with carbonate ions is far greater than that with bicarbonate ions,
increasing the pH of the medium will be expected to decrease
the efficiency of OH trapping by TCE or PCE.
On the other
hand, increasing pH values will accelerate the decomposition
process which produces more hydroxyl radicals (Figure 2 and
equation 6).
Apparently, the competing effects noted above essentially
cancel each other and their is no practical advantage to
increasing the pH when TCE destruction is the desired result.
It should be noted, however, that this conclusion may not
apply to all substrates and test waters, especially those
which are low in alkalinity and higher in natural promoting
agents.
0zone/H2Q2 System.
According to the works of Hoigne et al (15-17)
and'Hart et
al (18-19), hydrogen peroxide can initiate the decomposition
of ozone by a single electron transfer process wherein the
initiating species is the hydroperoxide ion H0 2 ~ (reaction 1,
Table 2). The products of this reaction are the ozonide ion
0 3 ~ and the hydroperoxide radical HO2, each of which can form
OH radicals by the pathways shown in Table 2.
constants for equations (1) and
10
From the rate
(6) it can be shown that
initiation by peroxide is much faster than by hydroxide ion
when the former is present in the millimolar range (15).
Using a steady state approximation for the various intermediates shown in Table 2 the following equation for the
steady state concentration of OH may be derived:
[OH] =
2k
lKPER [H2023r033/rH+]
+
*MM
k
(13)
s
% it i3
where the constants are defined in Table 2, M is the substrate (TCE or PCE), and S^ refers to the various substances
in the water which act as scavengers of OH radicals.
The "2"
in equation (13) symbolizes the fact that two OH radicals are
formed from each initiation step (equation 1) , one from the
0 3 ~ ion and one from the H0 2 radical.
The rate of TCE or PCE oxidation is given by the expression
-d(ln M)/dt
where k M
0H
=
k0
=
k M/OH [OH] +
k M f 0 3 [0 3 ] f
(14)
and kjj Q 3 refer to rate constants for reaction of
the substrate with OH radicals and ozone respectively, and k 0
is the observed pseudo first order rate constant for overall
oxidation of M.
Under conditions where the direct reaction
of M with 0 3 is negligible, the last equation may be combined
with equation (13) to yield equation (15):
11
=
ko
k
M,OH2klKpER [H2Q23[033/[H+3
k
MtM]
(15)
+^ki[Si]
As
In hard ground water the principal scavengers S^ will be
bicarbonate ions that are present in relatively high concentration
compared
to
the
pollutant
substrate
M;
then
equation (15) will reduce to equation (16):
k0
Equation
(16)
=
k
states
Mf0H2*lKpER [H202 3CO3 3/[H+]
k
HC03tHC03~3
that
the
psuedo
first-order
(16)
rate
constant for the OH radical oxidation of a substrate in the
O3/H2O2 process should be proportional to the liquid phase
concentrations of ozone and peroxide, and inversely proportional to bicarbonate and hydrogen ion concentrations.
In a CSTR, the level of ozone present in solution [03] is
determined by the rate of transfer from the gas to the liquid
phase minus the ozone lost to decomposition and reaction:
{d[03]/dt)t
= k1*a{P/H - [03]) - £> kj[Sj][03]
(17)
\
where -£ Sj refers to all of the species that consume ozone,
k^*a
is the overall mass transfer coefficient, P is the
partial pressure of ozone in the gas phase and H is the1
Henry's Law constant for ozone in water (82 atm-L-inole-1) .
12
If we assume that the major reactions consuming ozone are
equations 1 and 2 (Table 2),
then equation (17) reduces to
equation (18) :
= k!*a{P/H - [03]> - 2k 1 Kp ER [H 2 0 2 ][0 3 ]/[H + ] (18)
(d[03]/dt}t
When the rate of transfer has reached a steady state, the
ozone concentration in the liquid phase is given by equation
(19), obtained by setting equation (18) to zero:
[03]
-
*l*a(P/H)
+ 2k 1 K PER [H 2 0 2 ]/fH T ]
*l*a
(19)
This expression for residual ozone can then be plugged into
equation (16) to give equation (20):
= kMyOH2kiKpER[H202]/[H->-] ^
k!*a(P/H)
(20)
*-o
^HC03[HC03-]
kx*a + 2k 1 K pER [H 2 0 2 ]/[H + ]
k
When
the
reaction
2kiKPER[H202]/[H+]
conditions
is
iauch
are
such
that
greater
than
ki*a,
peroxide levels are high, then equation
the
term
as
when
(20) reduces to
equation (21):
k0
=
^M>0H)(ki*a)(P/H)
k
(21)
HC03[HC03~3
that is, the value of k 0 will be proportonal to the mass
transfer coefficient, the partial pressure of\ozone in the
gas phase and the rate constant for reaction of\OH radicals
with the substrate M.
When peroxide levels are low, equation
13
(20) reduces to equation (22) :
k0
=
*MfOH2*lKpER[H2023/[H+3 (P/H)
k
HC03tHC03-]
(22)
which states that k 0 should be a linear function of peroxide
dose.
In both cases, k 0 will be inversely proportional to
bicarbonate levels, the assumed principal scavenger.
The experimental data in Figures 4 and 5 show that hydrogen
peroxide has a significant accelerating effect on the rate of
oxidation of TCE and PCE.
for the oxidation
of TCE
Pseudo-first order rate constants
and
PCE at various ozone and
peroxide dose rates are shown in Table 3.
In Figure 6 the
values of the rate constants at an ozone dose of 15 lag/min
are plotted versus the ratio of peroxide to ozone dose.
The
shape of the curve is precisely that which is predicted by
equation (20) as discussed above.1
The data
in Table
3 show that the addition of hydrogen
peroxide causes a maximum rate enhancement for TCE 'oxidation
by a factor of about 1.8 to 2.8, depending on the ozone dose
rate.
PCE rates are enhanced much more dramatically, from
1
There is another possible explanation of the shape of
Figure 6, namely, that superoxide^ 0 2 ~ does not enter into
subsequent OH formation by equation (5), i.e. in excess
concentration hydrogen peroxide quenches OH radicals by
equations 7 and 8 without contributing to the pool of OH
precursors (4). There is little reason to suspect that this
is the case but it is a possibility that cannot be discarded.
14
2.0 to 6.5 fold.
This is apparently due to the fact PCE
reacts primarily by a radical mechanism whereas TCE reacts
both
by
direct
mechanism.2
reaction
with
03
and
by
the
radical
When OH radical chemistry is dominant, the ratio
of the rate constants for TCE and PCE oxidation should be
equal to the ratio of their rate constants with OH radicals:
k
o,TCE/ko,PCE
=
k
5a/ k 5b
=
1
'7
<23)
Inspection of Table 3 will show that the ratio of psuedo
first order rate constants is close to this value when the
ratio of H202 to O3 is near unity and when the ozone dose
rate is relatively low (4.5 mg/min).
Effects of Bicarbonate on O3 end O3/H2O2 oxidal'.ions.
There is a significant amount of bicarbonate in the ground
water tested, which should trap OH radicals and interfere
2
The ratio of the pseudo first order rates constants
o TCE/ko PCE wner> n o peroxide was added are not constant
(Table 3)'. This is probably due to the fact that pure 0 3
chemistry is never observed in a natural water, and especially at low ozone doses there is a mixture of direct O3 and OH
radical chemistry.
Only when there are no natural
promoters \can the ratio approach the value for the direct
reaction, which according to Hoigne and Bader should be
greater than 170 (13) . Since the ratio for reaction with OH
radicals is\ only 1.7 the observed values with no added
peroxide are (evidence of mixed chemistry.
k
15
with the destruction of target compounds such as TCE and PCE.
The OH radical is far more reactive with TCE than with the
bicarbonate ion, as shown in Table 2; however, the molarity
of the bicarbonate ion (6.0 x 10~ 3 M at 300 mg/L as CaC03) is
much greater than that of the organic halides (TCE = 0.76 x
10" 6 M at 100 ppb).
The rate constants for reaction of TCE, PCE and bicarbonate
with OH radicals can be used as a basis to predict the
efficiency Q of radical quenching by TCE and PCE, defined as
the percentage of OH radicals that are quenched by TCE or PCE
respectively.
Assuming
bicarbonate
is
the
principal
quenching agent, Q may be approximated by equation (24):
Q =
k 5a[ TCE]
x
k5a[TCE] + k10[HC03-]
10Q
_
* 5a [TCE] x
k10[HCO3-]
100
(24)
Batch scale runs to test the effect of bicarbonate softening
of Los Angeles ground water were not conducted in this study
(however, see the following paper).
bonate is well illustrated,
The effect of bicar-
however, in the experimental
data shown in Figure 7 and Table 4.
Arrowhead distilled
water, ( [HC03~] < 0.1 mM) was used as the source of water
for this set of runs.
Sodium bicarbonate was used to adjust
the bicarbonate level and pH was adjusted by addition of
sodium phosphate buffer solution.
constants
from
alkalinity.
these
runs
as a
Table 4 summarizes rate
function
of bicarbonate
Several features of this data are interesting.
16
I
First, as ;shown in Figure 7, the rate of TCE oxidation is so
fast in this water at low bicarbonate levels that TCE is
degraded from 500 ppb to 3 ppb within 10 minutes.
Under
these conditions it is difficult to obtain good rate data
with our experimental system.
^o TCE/^O PCE
are
Second, values of
* n t-ne range predicted from equation (23)
for OH radical reactions.
Third,
the rate constants at low
alkalinity values are a factor of two to three greater than
those observed at similar ozone:peroxide doses in the natural
groundwater.
This is apparently due to the fact that there
are other radical scavengers in natural waters that decrease
the efficiency of the oxidation of the olefins.
Fourth,
the
value of the product of k 0 times the molar bicarbonate level
is a constant at a given ozone dose rate, as predicted by
equation (21).
Finally, the values of the efficiency factor
Q show that at the high alkalinity values of North Hollywood
ground water, TCE and PCE are not using more than a few
percent of the available OH radicals.
the expected
effect of bicarbonate
These results verify
ion and
suggest that
softening prior to oxidation may be a cost effective addition
to the 03/H202 process under some conditions.
Oxidant Doses for 95% Rercoval of Substrates
The rate constants in Tables 1
and
3 may be used to
calculate the dose of ozone required for 95% destruction of
17
the two olefins (Table 5).
A detailed analysis of this data
will not be given here;
however, it is clear that the
results suggest that the process is quite promising.
Further
details of cost/effectiveness of the process are given in the
following paper.
Evidence for Enhancement of Ozone Ilass Transfer
When liquid phase reaction rates are high, the mass
transfer
coefficient
k^*a
may
without rapid reaction k^a.
be
larger than
the value
The enchancement factor E is
defined as the ratio k^*a/k^a.
Direct measurements of k^a in the CSTR used in this work
give a value of k^a of 4.6 (±0.4)x 10~ 4 s - 1 .
These runs were
made in water from North Hollywood Well No. 14 at three
different ozone doses with no peroxide added (Figure 8 ) .
When peroxide levels are high there is essentially no
residual ozone found in the liquid phase or in the ozone offgas.
For example, in a run with ozone dose at 14.9 mg-min"-1-
and peroxide dose at 10 mg-min-1, the residual ozone levels
\
were near our detection limit for the indigo method (0.1 mgL-1V.
That is, all of the ozone added is consumed (>98%).
Hence\ we may may assume that
[03] <<
practical purposes, d[03]/dt is zero.
18
P/H
and
for all
Equation (25) may then
be used to calculate a lower limit value for k^ a:
. *
Ozone doseCmole-L-1-^"1)• Ozone utilization (0.98)
P (atm)/ H (atm-L-raole"1)
(25)
The value calculated from equation (25) is k^*a = 7.8 x 10~ 4
s_1.
Thus, the mass transfer enhancement factor for these
conditions is at least a factor 1.7.
CONCLUSION
Direct ozonation of TCE and PCE in a high alkalinity ground
water is a relatively slow process and little effect is seen
when the pH is increased from 4 to 10.
hydrogen peroxide up to a H202/03
The addition of
ratio of about 0.5-0.7
(w/w) accelerates the oxidation of TCE by a factor of two to
three tiroes and PCE from two to six times, depending on the
ozone dose.
Because of an apparent mass transfer effect,
increasing the hydrogen peroxide dose rate beyond a certain
level does not increase the oxidation rate of TCE and PCE.,
however, at higher ozone dose rates further rate enhancemnts
can be expected.
Relative rate data for TCE vs. PCE oxida-
tion suggests that the principal species involved in the
oxidation is the OH radical.
Processes that utilize hydroxyl
radicals\to remove water contaminants are less efficient in
high alkalinity water because of the presence of radical
scavengers cuch as HC03~ end C03~2.
19
In the present case, the
data suggest that TCE and PCE oxidation is still a promising
process
even
though
only
a
small
percentage
radicals are used for TCE/PCE oxidation.
of
the OH
Water softening may
therefore be used to further increase the effectiveness of
the process.
Acknovledqements
This work was supported by the city of Los Angeles
Department of Water and Power and the USEPA through CR813188, R. Miltner Project Officer.
been subjected to review by EPA.
This article has not
Therefore, it does not
necessarily reflect the views of the agency, and no official
endorsement should be inferred.
The authors are grateful to
Marco Aieta, Rhodes Trussell and Carol Tate of James M.
Montgomery, Consulting Engineers and to Larry KcReynolds of
LADV7P for helpful discussions.
\
20
REFERENCES
1. Federal R e g i s t e r .
(1987).
2. Glaze, W.H., "Drinking-Water Treatment With Ozone,"
Environmental Science & Technology, Volume 21, No. 3, pp.
224-230, 1987.
3. Glaze, W.H., J.W. Kang, and E.M. Aieta, "Ozone-Hydrogen
Peroxide Systems for Control of Organics in Municipal Water
Supplies," in The Role of Ozone In Water and Wastewater
Treatment, Proceedings of- the Second International Conference, Edmonton, Alberta, p. 233 (28-29 April 1987).
4. Glaze, W.H., J.W. Kang, and D.H. Chapin, "The Chemistry of
Water Treatment Processes Involving Ozone, Hydrogen Peroxide
and Ultraviolet Radiation", Ozone: Science & Engineering,
1987 (in press).
5. Farhataziz and A.B. Ross., "Selective Specific Rates of
Reactions of Transients in Water and Aqueous Solutions. P
III. Hydroxyl Radical and Perhydroxyl Radical and Their
Radical Ions", Natl.
Stand. Ref. Data Ser.(U.S. Natl.
Bur. Stand.) No 59 (1977).
6.
(following paper)
7. Yocum, E.H.,"Ozone Mass Transfer in Stirred Vessels,"
Proceedings, 86th National Meeting,
American Institute of
Chemical Engineers, April 1-5 (1979).
8.
Flamm, D.L., "Analysis of Ozone at Low Concentrations
With Boric Acid Buffered KI,"
Environ. Sci. & 'Technol.,
11:10:978 (October 1977).
9.
Bader, H., and J. Hoigne, "Determination of Ozone in
Water by the Indigo Method: A Submitted Standard Method,"
Ozone Sci. & Engng., 4:169 (1982).
10. Masschelein, W., M. Denis and R. Ledent, "Spectrophotometric determination of Residual Hydrogen Peroxide," Water &
Sewage Works, pp. 69-72, August 1977.
11. Lazrus, A.L. , G.L. Kok, S.N. Gitlin, J.A. Lind, and
S.E. Mclaren, "Automated Fluorometric Method for Hydrogen
Peroxide in Atmospheric Precipitation", Anal. Chem. 57:917922 (1985).
21
12.
Association of Official Analytical Chemists, Official
Methods of Analysis, W. Horwitz, editor, p. 545 (1980).
13. Hoignd, J. and H. Bader, "Rate Constants of Reactions of
Ozone With Organic and Inorganic Compounds in Water, I - NonDissociating Organic Compounds," Water Research, 17:173
(1983).
14. Staehelin, J., and J. Hoigne, "Decomposition of Ozone in
the Presence of Organic Solutes Acting as Promoters and
Inhibiters of Radical Chain Reactions," Environ. Sci. &
Technol., 19:1206 (1985).
15. Staehelin, J., and J. Hoigne, "Decomposition of Ozone in
Water: Rate of Initiation by Hydroxide Ion and Hydrogen
Peroxide," Environ. Sci. & Technol., 16:676 (1982).
16. Buhler, R.E., J. Staehelin, and J. Hoigne, "Ozone
Decomposition in Water Studied by Pulse Radiolysis. 1. H0 2
/ 0 2 and HO3/O3 as Intermediates," J. Phys. Chem., 88:2560
(1984) .
17. Staehelin, J., R.E. Buhler, and J. Hoigne, "Ozone
Decomposition in Water Studied by Pulse Radiolysis. 2. OH and
HO 4 as Chain Intermediates," J. Phys. Chem., 88:5999 (1984).
18. Forni, L., D. Bahnemann, and E.J. Hart, "Mechanism of
the Hydroxide Ion Initiated Decomposition of Ozone in Aqueous
Solution," J. Phys. Chem., 86:255 (1982).
19. Sehested, K., J. Holoman, E. Bjergbakke, and E.J. Hart,
"Ultraviolet Spectrum and Decay of the Ozonide Ion Radical,
0 3 , in Strong Alkaline Solution," J. Phys. Chem., 86:2066
(1982) .
20.
Christensen, H.S., K. Sehested and H. Corfitzan,
"Reaction of Hydroxyl Radicals with Hydrogen Peroxide at
Ambient and Elevated Temperatures", J. Phys. Chem.', 86:1588
(1982) .
\
22
LEGEND OF FIGURES
Figure 1.
System.
Schematic Diagram of 03/H202/UV Experimental
Figure 2.
Scheme showing the principle species in the
decomposition of ozone initiated by hydroxide ions and OH
radical quenching by scavengers.
Figure 3.
Effect of pH on the ozonation of TCE in North
Hollywood well water.
Ozone dose: 15 mg/min;
Bicarbonate alkalinity: 200 mg/L as CaC03.
Figure 4. Pseudo first-order plot for destruction of TCE by
°3/H2°2 Process in North Hollywood well water. Ozone dose:
14.9 mg/min; Bicarbonate alkalinity: 300 mg/L as CaC0 3 ; pH:
7.2-7.4.
Figure 5. Pseudo first-order plot for destruction of PCE by
°3/H2°2 process in North Hollywood well water. Ozone dose:
14.9 mg/min; Bicarbonate alkalinity: 300 mg/L as CaC0 3 ; pH:
7.2-7.4.
Figure 6. Effect of hydrogen peroxide on the pseudo firstorder rate constants of oxidation of TCE in North Hollywood
well v:ater.
Figure 7. Effect of bicarbonate on the 03/H202 process for
destruction of TCE in Arrowhead distilled water. Ozone dose:
4.5 mg/min, H2O2 dose: 2.0 mg/min.
Figure 8. Transfer of ozone into the CSTR with 'water from
North Hollywood well No. 14. No added peroxide.
23
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Electron
Transfer
Agents
(EH)
( E n*1)
Radical
Quenchings
(HCO3-, CO3-2,...)
Substrate
Oxidation
(TCE.PCE)
P^
4.
-2.0
10
15
Time (min)
, :
>
-
In
Time (mfn)
+•&
InfESLJ
LPCEj
-1.0
ma HjO^mg o3
o 0.00
© 0.48
A 0.66
A 1.00
10
Time (min)
15
20
y
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B
O|OUJ
vo
8*1
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O'O
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3
o
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a
o
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,n
3
Bl]- -°--5.0
-6.0
10
Time
15
(min)
#31
kOG
k L a DETERMINATION
2.000
O3 Dose ( m g / m i n )
o : 15
a : 8.5
A : 4.5
I
X
\
DL
-1.000
0
5
10
15
20
Time (min)
25
30
35
40
TABLE 1
Pseudo-First Order Rate Constants for
the 03/pH System
NORTH HOLLYWOOD WELL NO. 26
Rate Constants x 10 4 (s_1)
pH
pH = 8
O3 Dose
pH = 4
mg/min
4.5
8.4
15.1
TCE
PCE
TCE
5.0
7.8
11.0
2.8
3.0
2.3
5.0
8.4
12.1
24
pH = 10
PCE
2.4
3.1
3.0
TCE
6.1
9.2
11.4
PCE
3.4
4.6
4.5
TABLE 2
PRINCIPAL REACTIONS IN THE 0 3 / H 2 0 2 PROCESS
REACTION
CONSTANT
REFERENCE
H 2 ° 2 ^ H°2" + H*
K P E R =1.6X10~ 1 2 M
H 0 2 ~ + 03-»»03~ + H 0 2
k 1 =2.8xl0 6 M" 1 S~ 1
(15)
H 0 2 ^ H+ + 0 2 "
K HO2 =1.6xl0~ 5 M
(15)
2.
0 2 ~ + 0 3 —»-03~ + 0 2
k 2 »1.6xl0 9 M" 1 S~ 1
(16)
3.
0 3 ~ + H"t-»-H03
K 3 =6.3xlO" 9 M
(16)
4.
H0 3 -*OH + 0 2
k 4 =l.lxl0 5 S" 1
(16)
5a. OH + TCE—9-Products (?)
ksa^.OxlO^"^"1
(5)
5b. OH + PCE — >
k5b=2 - 3xio9n~1s'~1
(5)
(18)
1.
••
6.
OH" + 0 3 - K ) 2 ~ + H 0 2
k 6 =70M~ 1 S" 1
7.
OH + H0 2 ~—->0H" + H 0 2
lHy-7
.SxlO^'^-S"1
(20)
8.
OH + H 2 0 2 ~~>H 2 0 + H 0 2
k 8 =2.7xl0 7 M" 1 S~ 1
(20)
9.
OH +
10. OH + HC03=-»-OH" + HC0 3
k 1 0 =l. Sxio^'^-S" 1
(5)
11. OH + C 0 3 ~ > O H ~ + C 0 3 =
k 2 1 =4.2xl0 8 M~ 1 S~ 1
(5)
12. HC0 3 ~—> H+ + C 0 3 =
K
Sj^—>Products (?)
HCO3=5.0xl0"l 1 M
^Cs^ is the S U M of the various matrix substrates that quench
hydroxy1 radicals.
25
TABLE 3
Pseudo-First Order Rate Constants
for the O3/H2O2 System
NORTH HOLLYWOOD WELL NO. 14
Rate Constants x 1 0 4 (s
O3 Dose: 4.6 mg/min
mg H 2 02/mg O3
0.00
0.11
0.33
0.54
1.00
k0
TCE
PCE
TCE/PCE
4.1
5.0
8.8
8.1
7.0
1.9
2.2
4.4
4.1
4.0
2.2
2.3
2.0
2.0
1.8
TCE
PCE
TCE/PCE
7.2
10
16
18
20
2 4
4, 1
7, 1
8, 7
7.3
TCE
PCE
11
14
20
27
29
30
27
1.
2.
7,
7.
8.
7.
9.0
O3 Dose: 8.4 rag/rain
mg H20 2 /mg 0 3
0.00
0.12
0.36
0.60
1.00
3.0
2.4
2.7
2.1
2.7
O3 Dose: 14.9 mg/min
mg H20 2 /mg O3
0.00
0.07
0.14
0.48
0.67
1.00
1.34
26
TCE/PCE
7.9
5.4
2.8
3.6
3.2
3.9
3.0
TABLE 4
Effect of Bicarbonate on the Rate of Oxidation
of TCE and PCE with the 0 3 /H 2 0 2 System1
H
[HC03""]
(mM)
2°2 : 1 0 mg/mi-n
0 3 : 15 mg/min
H2O2: 2 mg/min
O3: 4.5 mg/min
3
1
*o X 10 S""
TCE
PCE
ko X 10 3 S-l
TCE/PCE
TCE
PCE
TCE/PCE
>11.1
——
>8.4
>6.8
—
5.9
1.8
3.5
2.0
1.9
QTCE 1
0.0
>16.3
2.0
11.4
3.6
6.5
3.7
1.8
2.0
1.1
1.8
6
5.2
5.2
2.7
1.9
1.5
0.8
1.4
4
1
10
Q: Efficiency of TCE of OH radicals based on equation (24);
calculated at a concentration of TCE of 100 ppb and at lower
of two dose rates shown above.
27
1
TABLE 5
Dose Required for 95 % Removal of TCE and PCE
North Hollywood Well No. 26
Process
«
0 3 (mg/L)
H 2 0 2 (mg/L)
TCE
PCE
TCE
O3 1
9
33
-
0 3 /H 2 0 2 2
4
12
2
PCE
8
1
Conditions:
: 0 3 Dose: 15 ug/min, pH: 8.0;
2
: O3 Dose: 15 mg/inin, H 2 0 2 Dose: 10 mg/mi
1-2
: Initial TCE and PCE concentrations:
and 50 ppb; Alkalinity: 200 iag/L as CaC03.
28
IHACTIVAIIOH ALD/OR DESTRUCTION!cy ...
OF THK CYSTS OF GIARDIA WITH PROTOZOHK
mmi-mCharles P. Hibler, Department of Pathology,
College of Veterinary Medicine and Biomedical Sciences,
Colorado State University,
Fort Collins, Colorado
80523
December 19, 1984
IHXR0DUCTION:
At the request of Dr. Robert McGregor, Water Management, Inc., 1660 South
Albion Street, Suite 513, Denver, Colorado
80222, we performed seven static
tests to determine if photozone was effective in the inactivation and/or destruction of the cysts of Giardia duodenalis of human origin.
Water Management, Inc., is investigating the potential effectiveness of
photozone equipment at an established water treatment plant at Aspen, Colorado,
as an additional safeguard against Giardia.
The existing plant is a rapid sand
filtration with chemical flocculation and coagulation followed by chlorination in
sufficient quantity to provide the required amount of free chlorine throughout
the distribution system.
Photozone will be introduced as an added safeguard and
as an application that possibly will be more effective in inactivation and/or
destruction of Giardia cysts.
Therefore, Water Management, Inc., wanted to
determine if photozone together with a small amount of free chlorine was effective.
1
The time of year when this system possibly would be at risk for Giardia
would be in the fall and winter months when temperatures are between 0-5°C and
turbidity readings are in the range of 0.5-0.8 NTU. The static test was designed
to approximate these conditions 4s near as possible in Trials I - III on
October 24,; 1984yy Based, "on .ft-he /results* ;ofj these 'tests, :^additio*nal|J
conducted on November 7-8, 1984, to confirm the results of the first tests and to ,|tT^;: :,
determine if there would be any reductions in the effectiveness of the photozone
at higher levels of turbidity.
TRIALS I - III
Materials and Methods:
Location:
The Poudre River at Fort Collins Water Treatment Plant tl
was chosen as the
site for this test because water temperatures this time of year range between
0-4°C, turbidity is between 0.5-0.7 NTU and the laboratory at the Water Treatment
Plant has sufficient equipment for measuring the temperature, turbidity, and free
chlorine; moreover, the plant is a source of power for the equipment necessary.
Methods;
For the purpose of this series of static tests, a 55-gallon nalgene tank was
positioned near the Poudre River and filled with raw Poudre River water. Temperature, turbidity, free chlorine, and photozone levels were established by representatives of Water Management, Inc.
Source of Photozone:
\
The\ photozone was generated by a ultraviolet tube through which ambient air
concentrated with oxygen was passed. The oxygen concentration of the concentrated
air supply was estimated to be 28 percent by weight compared to 23 percent by
w.iight for_ normal air. The purpose of the oxygen concentrator in the tests
was to enhance the overall production of photozone to reduce the setup time for
each test.
The photozone was then passed into the nalgene drum and circulated by
means of a perforated PVC tube coiled at the bottom of the drum.
Free photozone
was monitored by the oxidation/reduction potential (ORP) expressed in millivolts.
For all the tests, the level of photozone was maintained between 0.3 and 0.6 mg/1.
• - -•••-.::?.' Source of Giardia duodenal is ' C Y S ^ S S X ^ : ^ : , , :..j-;!:.;;];;.;..;'lj? \
'X"-.;-;/
Cysts were obtained in a human stool specimen through the courtesy of a
local hospital.
Cysts were diluted in distilled water, strained through several
layers of gauze to remove the larger material and maintained at 5°C in distilled
water.
Counting of the cysts was performed by direct microscopic examination of
50 microliter subsamples (four replicate counts) and then extrapolated to determine
cysts/mililiter and subsequently cysts/sample.
This technique provides a reason-
able level of accuracy but is not an absolute figure.
This source wa6 determined
to have a total of 6.5 X 1 0 6 cysts/ml.
Although
the morphologic quality of these
cysts was
superb, morphologic
quality does not necessarily mean that the cysts were alive/or infectious.
This
can only be determined by a laboratory excystation procedure or the introduction
of these cysts into a suitable biologic model.
Our laboratory uses the Mongolian
gerbil (Meriones unguiculatus) to determine infectivity.
The standard procedure
is to introduce 5,000 cysts per animal into each of five Mongolian g e r b i l s aged
7-8 weeks.
If these cysts are highly infectious, the gerbils will begin producing
cysts as a result of the
infection on day four post
inoculation.
They will
continue to produce cysts for the next 4-5 days reaching a peak cyst productivity
on Day 6 to 7 post inoculation.
If the sample is highly
infectious, the total
\ fecal output of five Mongolian gerbils over a peiiod of 24 hours should produce
between 20 and
30 million
cysts.
Infection
3
of five Mongolian
gerbils
with
the cysts from this human source resulted in a cyst production 7 days later of
27.3 x 10" Giardia cysts.
The cysts from these gerbils were thoroughly cleaned
as given above, diluted in distilled water, counted as closely as possible, and
maintained in distilled water until the time of the trial (two days later).
PROTOCOL:
'r*^&;Jneprotocol established was to run a .series of threestati'c tests 'maintaining^-?.^'-:
a temperature of 0-4°C, a turbidity of 0.5-0.8 NTU, a constant amount of photozone, .; ••,
and a varying amount of free chlorine at each trial. During each trial, 6ubsamples
containing Giardia cysts were to be withdrawn and the chlorine and photozone
denatured with the addition of IX sodium thiosulfate.
30-minute
treatment subsample and a 120-minute treatment subsample. The Giardia
cysts contained in
and
Each trial called for a
these subsamples were to be examined for morphologic quality
then introduced orally
into susceptable Mongolian gerbils to determine
if they were inactivated and/or destroyed.
For each trial, once the free photozone and the free chlorine and other
parameters had been established, a total of 5.13 x 10-*
Giardia cysts were
introduced into the nalgene drum (10,000 per gallon). At 30 minutes post exposure
a 15-gallon sample was withdrawn from the drum with the aid of a small centrifugal
^ P pump and the suspended material trapped on a one micron (nominal rating) polypropylene filter.
As the subsample was being extracted, sodium thiosulfate was
trickle-dosed into the line. This same procedure was repeated for the 120-minute
trial.
Filters containing Giardia cysts and other material present in the raw
water were refrigerated, taken to the laboratory, and processed in distilled
\
water.
Processing a polypropylene filter calls for cutting the fibers away from
\ the core and hand washing in distilled water.
Once all the filters had been
processed, they were refrigerated at 5°C until the following morning when they
were processed for animal inoculation.
Distilled vater in gallon jars containing
Giardia cysts and other material were concentrated by centrifugation until the
contents of the filter had been concentrated
into a 10 milliliter volume.
SubsampleB of this material were then examined for Giardia cysts to determine
morphologic quality and to calculate the total numbers for animal inoculation.
•?;;•£ .The protocol called for the inoculation of 7-10 Mongolian gerbils with;! •'
Giardia cysts from each trial.
A group of 7-10 Mongolian gerbils were to be
inoculated with cysts from the source material to determine infectivity.
comparable number of negative controls was also included.
A
In addition, a group
of 7-10 gerbils were to be orally inoculated with cysts that had been maintained
in river water during the trial and exposed to 1% sodium thiosulfate.
RESULTS:
Five days post-exposure the Mongolian gerbils infected with the source
material (positive controls) passed 35 x 10& Giardia cy6ts in a 24-hour period.
The Mongolian gerbils infected with the river water control passed a total of
32 x 10° Giardia cysts in a 24-hour period.
The Giardia source material and the
Giardia cysts exposed to river water were rated morphologically superb (microscopic examination) the day following the trials and for one week thereafter
(following which they were not further examined).
However, in each photozone
trial only a few Giardia cysts could be found following 30 minutes- exposure to
the combination of ozone and free chlorine; at 120 minutes exposure to free
chlorine no Giardia cysts could be found.
Therefore, no Mongolian gerbils were
inoculated with any of the material.
DISCUSSION:
The discovery that only a few Giardia cysts vere present in the 30 ninute
post-exposure subsamples was surprising.
Even more surprising was the obviouB fact
5
that these cysts were dead.
The internal structures were shrunken and shriveled
to the degree that they were unrecognizable as cystB.
Re-examination of the
protocol used indicates that the combination of photozone and free chlorine
killed the cysts before the 30-minute contact time.
Even though the photozone
and free chlorine were denatured immediately with the addition of 1Z sodium
thiosulfate, apparently.' the deterioration process continued while the.jcysts werec
refrigerated in distilled vater overnight, thus destroying or rendering unrecognizable the cysts that were present.
It has been established, and it is our
experience, that the amount of free chlorine alone in this system (0.21 to
0.58 mg/1) is inadequate to kill the cysts in 30 minutes at 0-4°C, much less to
effect cyst destruction.
Moreover, the examination of Giardia cysts exposed to
this amount of free chlorine reveals that the morphologic quality of cysts can be
maintained at 5°C for at least three and usually four days before the internal
structures become distorted and the cysts become unrecognizable.
In addition to
an almost complete destruction of all Giardia cysts present in this raw water,
the crustaceans, free-living nematodes, nematode eggs, and crustacean eggs found
normally in this raw water (and present in the river water control) were not
present in these trial samples.
RECOKHKL'MTIOHS:
The combination of photozone and free chlorine, together with the'holding
time post treatment obviously effected total destruction of the Giardia cysts. It
was recommended that a subsequent series of trials be initiated and subsamples
withdrawn for morphologic analysis and animal inoculation at 5, 10, 20, and
30-minute intervals.
It was further recommended that these samples be processed
as soon as possible after the photozone and the chlorine had been denatured.
Cyst
deterioration to the point of complete destruction obviously
even
6
continued
though the photozone and chlorine have been denatured.
It was further recommended
that the subsequent trials be performed using only photozone and not a combination
of photozone and chlorine to determine the
effect of ozone alone on cyst inacti-
vation and/or destruction. It was also recommended that further tests be conducted
at higher turbidity levels to determine any interferences with photozone.
'f-'^r-l/. These^ jrecommendations vere^carried out in.Trials IV - VII on November .7-8,..'••,.' 1984. ':;-;•••i--..0-::-. .- ./'[-•
:•.:•'. • " ' ; -•
•'
• •
TRIALS IV - VII
Introduction;
The results of Trials I through III indicated that 0.21 - 0.58 mg/l free
chlorine in combination with 0.3 - 0.6 mg/l of photozone not only inactivated
and/or killed Giardia cysts but also completely destroyed the great majority.
However, the procedure used in Trials I through III necessitated holding the
cysts overnight in a refrigerator at 5°C before animal inoculation. The following
morning very few cysts could be found in the 30-minute contact time trials while
none could be found in the 120-minute contact time trials.
Even though the
activity of the chlorine and the photozone was stopped by the addition of 1% sodium
thiosulphate, we felt that cyst deterioration continued despite the inactivation
of the photozone and the free chlorine.
Therefore, at the request of this
investigator a second series of trials was initiated.
In general, the subsequent
trials called for contact times with photozone and free chlorine of 5 minutes, 10
minutes, 20 minutes, 30 minutes, and one hour.
These were done, in part, to
determine if there wa6 any physical deterioration of the cysts as a result of
exposure to photozone and chlorine, and also to determine if the activity of
photozone and chlorine in combination would inactivate and/or kill the cysts at
an earlier time than 30 minutes. Previous investigators have shown that photozone
7
'
alone will inactivate and/or kill Giardia cysts as early as 5 minutes at 1
mg/1.
However, these investigators were using distilled water, Giardia muris.
and laboratory excystation of cysts as the indicator of inactivation or death.
Tests were also conducted to determine the effectiveness of photozone without
chlorine and at turbidity levels in the range of 2.6 - 4.6 NTU.
A= series of four trials were planned.
Trial IV would examine cysts for-
morphology and animal inoculation at 5, 10, .20, 30, and 60 minutes using Poudre
River water with a turbidity of 0.74 NTU, a temperature of 4.1°C, 0.3 - 0.6 mg/1
photozone and 0.21 mg/1 free chlorine.
Trial V was designed to examine cysts for
morphology and animal inoculation at 30 and 60 minutes using raw Poudre River
water with the same level of photozone and no chlorine. Trial VI was designed to
examine cysts morphologically and by animal inoculation using
raw Poudre River
water with the same level of photozone, no chlorine, and increasing the turbidity
to 2.6 NTU with Bentonite.
Trial VII was designed to examine the cysts morpho-
logically and by animal inoculation after 30 and 60 minutes exposure to raw
Poudre River water with the same level of photozone, no chlorine, and 4.6 NTU
turbidity.
A concerted effort was made to keep the lag time at a minimum (the
period between inactivation of the photozone and the morphologic examination or
inoculation of animals).
Materials and Methods;
,
Location;
The location of these tests and the conditions for these tests were the same
as in Trials I through III.
Methods :
The methods of tais series of tests were the same as in Trials I through III.
8
Source of Photozone:
The source of the photozone for these trials was the same as the source for
the Trials I through III.
Source of Giardia doudenalis cysts:
The source of the cysts was the same as for Trials I "through III, and wa«*;;':.';,';;
determined to have a total of 37.0 X 10 6 cysts/ml.
These cysts were likewise
•
introduced into the Mongolian gerbil with essentially the same results as in
Trials I through III.
PROTOCOL;
General: For trials IV, V, and VI the 55-gallon Nalgene drum was seeded with
2 million Giardia cysts (40,000 per gallon); for Trial VII an additional 2
million Giardia cysts were added, making a total of 4 million (80,000 per gallon)
for that particular trial.
Trial IV:
For this trial, raw Poudre River water at a temperature of 4.1°C,
turbidity 0.73, photozone 0.3 - 0.6 mg/1, and 0.21 mg/1 chlorine was used.
Five
minutes after introduction of the cysts a 1 gallon grab-sample was removed and
sufficient sodium thiosulfate was added to provide a 1% solution.
The same
procedure was used at 10 minutes, 20 minutes, 30 minutes, and one hour.
These
one gallon grab-samples were siphoned through a 5 micron nucleopore membrane, the
membrane washed with distilled water, and the resulting filtrate centrifuged for
5 minutes at 1500 rpm.
Cysts were examined for morphologic quality and then
\
introduced into five Mongolian gerbils at an estimated 5,000 cysts/animal.
Trial V:
Photozone was generated to maintain 0.3 - 0.6 mg/1. Raw Poudre
River water at a temperature of 4.0°C and a turbidity of 0.75 NTU was used.
At
30 minutes and 60 minutes post-exposure time 5 gallons of the suspension was
9
J
pumped through a 1 micron polypropylene filter. This filter was cut to the core,
processed in distilled water, and filtered through a 5 micron Nucleopore membrane.
The filtrate washed off the nucleopore membrane was centrifuged for 5 minutes at
1500 rpm and the cysts were examined for morphologic quality and then inoculated
into five Mongolian gerbils at an estimated 5,000 cysts/animal.
Trial VI;
Bentonite was added to . the Poudre River water to praise the
turbidity to 2.6 NTU.
Water temperature was 4.5°C and photozone was maintained
at 0.3 - 0.6 mg/1. At 30 minutes and 60 minutes five gallon samples were pumped
through a one micron polypropylene filter and the samples processed as above.
Trial VII: For Trial VII, an additional 2 million Giardia
cysts were added
to the existing quantity of water, and an additional amount of Bentonite was
added to raise the turbidity to 4.6 NTU. Water temperature was 4.6°C.
Sufficient
photozone was added to maintain a level of 0.3 to 0.6 mg/1. At 30 minutes and 60
minutes 5 gallon samples were pumped through a 1 micron polypropylene filter and
the samples processed as given above.
River Hater Control;
Subsequent to the trials, a one gallon grab-sample of
Poudre River water was inoculated with sufficient sodium thiosulfate to make a 1%
solution and 25,000 Giardia cysts from the source material was added.
The following morning the cysts exposed to sodium thiosulfate and the raw
Poudre River water were inoculated into 5 Mongolian gerbils at a level of approximately 5,000 cysts per gerbil. An additional 5 Mongolian gerbils were inoculated
with the source material used for the trial at about 5,000 cysts per gerbil.
An
additional 5 gerbils were maintained as uninoculated controls.
RESULTS;
The results are presented in Tables 1 and 2.
The lag tine between inactiv-
ation of the photozone and/or chlorine was 20-25 minutes for the 5 and 10 minute
10
samples in Trial IV; thereafter, lag time was cut to 15 minutes in the 20 minute,
30 minute, and 60 minute samples from Trial IV and all samples in Trials V, VI, and
VII.
The morphologic quality of cysts in Trial IV were judged excellent at
10, 15, and 20 minutes.
5,
At 30 minutes post-exposure, fewer Giardia cysts could
be found and these were of poor '.morphologic quality, indicating that they were
dead.
The same results were obtained at 60 minutes exposure; however, fewer-
cysts could be found.
In Trial V a considerable number of the Giardia cysts
were judged morphologically excellent at 30 minutes exposure, but fewer cysts were
present in this sample. At 60 minutes exposure, few cysts could be found and all
of these were judged to be of poor morphologic quality.
In Trials VI and VII all
Giardia cysts found at both the 30 and 60 minute sampling periods were judged to
be of excellent morphologic quality.
DISCPSSIOH;
The results of Trial IV indicate that the amount of photozone in combination
with chlorine was effective in killing and/or rendering the cysts of Giardia
inactive between 20 and 30 minutes postexposure.
In Trial V, the chlorine was
eliminated and, as a consequence, three of the five gerbils became infected
with Giardia at 30 minutes post-exposure; however, one of these animals had a very
light infection. This indicated that photozone alone killed the cysts at sometime
between 30 and 60 minutes exposure.
The use of photozone at tfyese levels,
together with turbidities of 2.6 and 4.6 NTU did not kill many of the Giardia cysts
in the absence of chlorine.
The test results are reformatted in Table 3 to assist in an evaluation of
alternative Giardia control design concepts.
For a photozone concentration of
0.J - 0.6 mg/1, a free chlorine of 0.21 - 0.58 n.g/1, and a turbidity of 0.53\0.73 NTU, 30 minutes of treatment time are adequate for the deactivation of
11
\
Giardia cysts.
If there i6 no free chlorine, and a turbidity of less than 0.70
NTU, a treatment time of 30 - 60 minutes is required.
If shorter treatment times
and no free chlorine .are desirable, additional photozone is required.
If the
turbidity exceeds 2.30 NTU, treatment times in excess of 60 minutes of additional
photozone are required to control Giardia cysts.
12
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1
Reprinted from ENVIRONMENTAL SCIENCE b TECHNOLOGY, Vol. 21. Page 224, Mtrch 1987
Copyright © 1987 by the American Chemical Society and reprinted by permission of the copyright owner.
Drinking-water treatment with ozone
Ozone is a powerful disinfectant and oxidant,
but its chemical byproducts need to be better understood
3
William H. Glaze
University of California, Los Angeles
Los Angeles, Calif. 90024
Ozone came into use as a drinking-water disinfectant as early as 1906 at the
Bon Voyage plant in Nice, France;
since then, more than 1000 facilities
throughout Europe have adopted the
practice (/). Some use ozone as the primary or sole disinfectant; others use it
as an oxidant for the control of flora,
odor, and color and to reduce the manganese and iron content of drinking water. Lately, engineers at European
plants are finding that preozonation enhances the flocculation of suspended
particles in surface waters, and its use
for this purpose is expanding.
The use of ozone in North America,
however, has only recently begun to
gain acceptance. According to Rice,
the number of ozonation plants in the
United States has increased from five in
1977 to 20 in 1984 (1). During the
same period, the number of plants in
Canada increased from 23 to nearly 50.
Large plants arc beginning operations
this year in Los Angeles and in Hackensack, N.J.; one plant is scheduled to
open in Myrtle Beach, S.C., in 1988
(Table 1). The Los Angeles plant contains one of the largest ozone production facilities in the world.
One major factor in the increased interest in ozone is the need to decrease
the use of free chlorine in water treatment in keeping with legislated maximum contaminant levels (MCLs) for
trihalomcthaoes (THM.s). For many
years, free chlorine has been the disinfectant of choice in North America
Chlorine is not only a disinfectant, it is
a powerful oxidant Unfortunately,
chlorine also produces byproducts,
such as THMs, that can be harmful to
human health. The need for THM control has forced water utilities to search
for appropriate substitutes.
Water treatment by chloramination
(the combination of free chlorine and
ammonia) has emerged as the most
popular alternative disinfection process
because chloramines do not form
THMs. Chloramines are weak oxidants, however, so stronger oxidants,
particularly ozone and chlorine dioxide, are being considered as substitutes
for chlorine at the beginning and middle of the treatment process.
Ozone is gaining in popularity for
other reasons as well. In tests in which
ozone has been compared with chlorine, ozone has been shnwt; to be superior to chlorine as a coagulant 1.2). It
also appears to foim much smaller
amounts of mutagens than cither chlorine or chlorine dioxide do (/f) In addi-
tion, when ozone decomposes it generates radical intermediates that have
much greater oxidizing power than
ozone itself docs. The use of chemical
oxidants to disinfect water is shown
schematically in Figure 1
Ozone generation
Because ozone is an unstable gas, it
must be generated where it will be
used. The most common technique for
generating ozone is the cold plasma discharge method, in which ozone is
formed by decomposition of diatomic
oxygen:
O. (corona discharge)
O + O
O. -
o
jiSil
().
Ill
<-')
Figure 2 is a double tube n/one.gcn
crating unit commonly found in largescale applications. Large-scale generators can contain as many as 400 double
rubes, and they can generate 600 kg'
day of ozone when dry oxygen is the
feed gas. With air, the yield of ozone is
about 50% of that generated with oxygen. In both cases the feed gas must be
oil free and have a low. dew point
( - 5 2 °C to - 5 8 °C) Recent advances
in ozone generation by the cold plasma
FIGURE 1
Chanted oxidants In water treatment
Sow oxidation
by microorganisms,
diatomic oxygen, and sunlight
•-•:. c-tt*- •»-.-,
Mid-point .'.-;£••'';".'."'•'•':.'.1''
oxidation: \ ' - " : : > ":-'
Fostdisinfecttoo
— Disinfection
__ Protection of
distribution system
'— Control of btofouting
Color removal, taste and odor
: control, prevention of growth
h basins, enhancement of
cosguisdon snd
tsdtrnenteliort, oxfctetfon of
msngsnese, reduction of
T H M formation potential
Microbiotocfca) and
photochsmical oxidation of
natural organic materials,
iron, and manganese
- Nitrification of N H ,
^m&-
Stow ox&fclbn of menoareoe
end n&iurcl organic mntsrtal
• Typical points of application of
oxidants in surface water
treatment
Environ. Sci Technol. Vol 21, No 3. 1987 225
method, which have been reviewed by
Costc and Fiessinger (4), include the
development of generators that operate
in the medium frequency range (600
Hz); modifications in the design of the
tubes, particularly the use of ceramic
rather than glass dielectrics; and improved electronic systems for controlling current.
Ozone also can be generated b>
moans of ultraviolet (UV) light (less
than 200 mm generated b> arc discharge lamps, in much the same manner as ozone is formed in the upper
atmosphere (Equations 1 and 2). Although photochemical units cannot generate ozone at concentrations as high as
those produced by cold plasma generators. UV generators may be competitive for small-scale systems because
they require little capital investment
and arc relatively easy to maintain.
Transfer of ozone into water
O/one produced by the cold plasma
discharge method is present in air or
oxygen at concentrations of 1-35? and
3-7 ft, respectively. These values correspond to 11-90 g ozone per standard
cubic meter of air or oxygen. A number
of devices have been used to transfer
ozone into water; the most popular is
the counter-current sparged column
(Figure 3). Other systems include the
stirrcd-tank reactor with diffuscr, methods that increase mass transfer through
a combination of small bubble size and
hydrostatic pressure, and the in-line
static mixer.
In the absence of chemical reactions,
mass transfer from the gas phase to the
aqueous phase can be described by
Equation 3:
tIC/Jt ••= k, a(C* - C) =
k.afP/H - O
(3)
i/i which C is the concentration of
• >/i'iii- in the liquid phase. ('* is the liquid-phase concentration in equilibrium
226
Environ Sci Technol. Vol 21. No 3.1907
with the concentration of ozone in the
gas phase, P is the partial pressure of
ozone in the gas phase, H is the Henry's
law constant for ozone (0.082 aim m3
g-mol"1 at 25 °C), and kLa is the overall transfer coefficient. The upper
curve in Figure 4 is a plot of ozone
concentration in the aqueous phase in a
static reactor as ozone containing gas is
introduced. The initial slope of the line
is related to k, a. which is assumed to be
0.36 g-mol m ' min ' in this case.
Under actual conditions in a treatment plant, chemical reactions in the
liquid phase consume ozone. Thus,
Equation 3 must be modified to account
for the loss of ozone by the following
chemical pathways:
dC/dt = k L a(/7H - C) M O ( H O - ) - ki(S,)(C)
(4)
Here, ko is the rate constant for the decomposition of ozone and the term on
the extreme right is the sum of all the
rate terms for chemical reactions that
involve substrates (S,) in the water that
consume ozone.
The lower curve in Figure 4 is a plot
of the mass transfer of ozone into the
reactor. It takes into account only the
middle term in Equation 4 (autodecomposition of ozone). A rate constant of
70 M ' s"' is assumed (5). Rapid reactions in the liquid phase will drive
ozone dissolution; that is, the faster
ozone is consumed in the liquid phase,
the faster it will cross the gas-water
boundary. This is likely to be significant to the design of reactors that arc
based on the rapid decomposition of
ozone into radicals.
Drinking-water treatment
Ozone as a disinfectant. Ozone suffers from two major limitations as an
alternative to chlorine. First, it is unstable in water; it decomposes to oxygen
at a rate proportional to the pH of the
water. For example, at pH K. which is
typical of many drinking-water sup
plies, its haJf-lifc is less than one hour,
too short to ensure that a residual disinfectant capacity will remain at the far
reaches of a large distribution system.
Despite its short lifetime, however,
ozone is particularly effective against
recalcitrant microorganisms. It is more
effective than is chlorine for removal ol
Giardia (an organism that causes a gastrointestinal disease), viruses, and certain forms of algae (6).
Second, ozone reacts with natural organic substances to produce low-molecular-wcight oxygenated byproducts
that generally are more biodegradable
than their precursors are. These substances will promote biological growth
in a distribution system ("regrowth").
further limiting the disinfection efficacy of ozone. For these reasons,
ozone should be used in combination
with other disinfectants that maintain an
active residual for longer periods, and
it should be combined with some
method of filtration for removing biodegradable material.
Ozone as an oxidant. Ozone can oxidize many nuisance compounds or potential toxicants in water supplies.
These include natural color bodies,
some compounds that produce unpleasant tastes or odors, manganese(ll) and
iron(ll), and phenolic materials. Ozone
also coagulates natural water constituents. For these reasons, ozone has been
adopted as the preoxidant in the new
Los\Angeles treatment facility, where
pilot studies have shown that prcozonation substantially improves the filtration of.the raw water, thereby reducing
the need"for other chemical coagulants
and allowing shorter basin and filter
contact times (2, 7). Comparison tests
have shown that ozone is suhstantialh
superior to chlorine for these purposes
Although the mechanism of coagulation by ozone is not clear, several possibilities have been suggested. One possi-
bility is. the oxidation of mcta] ions to
yield insoluble forms such as Fe(III).
Another is oxidation of humic material
to form more polar or chelating groups,
which induce coagulation. Finally, oxidative dissociation of natural organic
material from colloidal clay particles,
which destabilizes the colloids, has
been suggested. Further research is under way, and more information should
be forthcoming (8).
Chemistry of ozone
In referring to ozone as an oxidant,
chemists often cite the very high negative value of the thermodynamic free
energy of reactions, as set forth 'in
liquation 5:
Oj f 2H 1 -i 2c — HjO +
0 2 (AG" - -400 kJ/mol)
(5i
in which AG" is the free energy. Although this very large negative value
defines the potential for ozone to act as
an oxidant, the usefulness of ozone in
water treatment is limited by the kinetics of its reactions.
In some cases the kinetics arc favorable enough to make ozone a practical
oxidant, but this is not generally the
case. When ozone reacts with typical
water contaminants, rate constants can
vary by more than eight orders of magnitude ranging from 107 M ' s"' for the
phenolate anion to 10'' M ' s"' for tctrachlorocthylcne (9, 10).
Ozone reacts best when it can act as
an electron transfer acceptor (for the
oxidation of metal ions), as an electrophile (for the oxidation of phenol
and other activated aromatics), and as a
dipole addition reagent (by addition to
carbon-carbon multiple bonds). The
rates of oxidation of organic compounds bv ozone arc sevcrelv de
pressed, however, by electron-withdrawing suhstituents. For example,
ozone reacts poorly with most aliphatic
organic halides, such as chloroform.
Ozone also docs not react with
aliphatic compounds other than those
that have easily oxidized groups, such
as aldehydes and ketones. Moreover,
ozone is not a good oxidant for most
specific organic materials in water
treatment. Rice has, however, pointed
out several exceptions: Ozone has been
used to oxidize sulfides, nitrites (to nitrate), cyanides (to cyanate), and some
detergents and pesticides ( / / ) .
The radical chemistry of ozone.
Recent studies from several laboratories support the application of ozone as
a chemical oxidant for water and wastewater treatment. Basic research has
shown mat ozone decomposes by a
complex mechanism that involves the
generation of hydroxy! radicals, which
.lie among the most reactive oxidizing
species (Table 2). Other studies have
Rate constanti (!»->«-')
Compound
Ozon«
•;iV,*i*.
Benzene
involved ozone and some other agent or
process, such as UV radiation, hydrogen peroxide, or ultrasound, to develop
water treatment processes that arc substantially more powerful than ozone is
alone. These new processes arc related
chemically to me decomposition mechanisms so elegantly elucidated by
Hoigne et a!. (5, 12-14) and Forni ct
al. (15) and anticipated much earlier by
Taubc and Bray (16).
The decomposition of ozone in pure
water is shown in Figure 5 as a cyclic
chain mechanism; the overall stoiebiometry is shown by Fquation 6:
20, — 30:
(6)
Decomposition can be initiated by hydroxide ions, formate ions, or a variety
of other species, and in pure water the
chains arcwery long (17) A single initiation stcp\can cause the decomposition of hundreds of molecules of ozone
before the chajn ends. Ozone is unstable at high pHv values because the dc
compositionjirocess is initiated by hvdroxidc ions.
In the presence of the usual water
contaminants, such as bicartionate ions
and natural organic matter, the evelie
chain shown in Figure 5 cim be broken
In the case of bicarbonate, the reaction
(liquation 7) is a simple election nans
fer process with the hydroxy! radical:
Environ So Technol . Vol 21. ^lo 3, 1987
227
superoxide ion (17, 19). But they are
also promoted by other water contaminants, such as metal ions.
Under practical conditions, the dose
of ozone is never enough to satisfy the
ultimate demand, and the reactions discussed above generally will stop when
the supply is depleted. Typically, this
will be long before the organic substances have become mineralized to
carbon dioxide
Catalytic ozonation processes
Ozone can be combined with other
processes or agents for more effective
water and wastewater treatment than is
possible b\ ozonation alone:
•
•
•
•
HCO., + OH — OH • + HCO., (7)
The net effect is to retard the decomposition of ozone. Hoigne and co-workers
have shown that increasing the carbonate ion concentration from 10g/m 3 to
100 g/m3 in phosphate-buffered water
will approximately double the half-life
of ozone at pH 8 (5).
Ozone and natural organic matter.
When natural organic materials are
present, ozone decomposition is accelerated, and the chemistry becomes
more complex. There are several reactions that can occur when ozone is
added to natural waters:
• Free or complexes! metal ions can be
oxidized, possibly by one-electron
transfer processes, to yield the
ozonidc radical anion, which can
then initiate the chain decomposition
of ozone (17).
• The hydroxyl radical can react with
aromatic groups in the humic molecules, yielding hydroxylatcd forms,
which are then more susceptible to
further attack by ozone (18).
• The hydroxyl radical can react with
aliphatic side chains or fatty acids,
usually by hydrogen atom abstraction reactions. The organic radicals
formed will generally add dioxygen
to form organic peroxides, which
decompose by eliminating the superoxide ion. The superoxide ion can
then reenter the chain to cause more
decomposition of ozone and in228
Environ Sci. Technol.. Vol. 2 1 . No 3. 198Z
creased formation of hydroxyl radicals (77, 19).
• Ozone can react with carbon-carbon
double bonds in the humic molecule
(by the usual pathway [20]), first to
yield peroxidic intermediates and
then to give hydrogen peroxide and
carbonyl products.
Ozone and synthetic organic substances. If anthropogenic organic materials arc present in water, the same
reactions can result in the destruction of
these species by ozone, hydroxyl radicals, or both. In general, the hydroxyl
radical reacts with organic compounds
at rates that essentially arc controlled
by diffusion; rate constants typically
are between l O ' M ' s ' and 10' M"1 s'"1
(Table 2).
Thus, it is possible in principle to induce ozone to act according to an entirely different kind of chemistry than it
usually shows in nonaqueous solvents.
Indeed, in actual water treatment applications ozone probably never acts according to the classical chemistry that
one finds in textbooks that describe
nonaqueous systems (20, 21). Classical
reactions can occur, but there also will
be a parallel set of reactions, often interacting with the first, involving the
radical intermediates (especially the
very reactive hydroxy! radical), as
shown in Figure 5. As Stachelin and
Hoigne have noted, these radical processes arc promoted by the products ol
the classical reactions, especially the
radiation {22 25)
ultrasound I26K
hydrogen per.xidc <27. 2X). or
metallic catalv-ts. such as reduced
iron (29).
Each of thoc processes probably involves chemistr) similar to that discussed by Hoigne et al. for the basecatalyzed decomposition of ozone (5.
13. 14). Hoigne has identified the hydrogen peroxide anion HO:" a s °nc of
the species that can initiate the cyclic
chain process shown in Figure 5. This
apparently accounts for observations
that hydrogen peroxide increases the
effectiveness of ozone for removal of
organic substances during water treatment (27. 28. 30).
Peyton and Glaze (25. 31) have verified the earlier work of Taube (32).
who showed that the UV photolysis of
ozone in water yields hydrogen peroxide rather than two hydroxyl radicals,
as occurs in wet air. Thus, the ozoneUV process resembles the ozone-peroxide process but offers the additional
advantage that direct photolysis and
photosMithesized processes also ivcw
to decompose organic substrates.
These ozonation processes are attracting increasing attention because ol
their ability to destroy organic substances in water. Figure 6 illustrates the
destruction of several chlorinated organic contaminants by ozone with and
without UV radiation. (The loss of
chloroform |CHCK] and dichlorobromomcthane |CHCI : Br] is caused hv
sparging, not by direct reaction with
ozone.) In general. UV exposure accelerates the decomposition oAthcsc substances, although the dccay\of he.vachlorobiphenyl (HCB) is retarded.
Trials of these processes now m progress or in planning stages aim-at applying them to the renovation of groundwater contaminated with synthetic organic compounds. The advantage is
that these processes destroy the con
taminants instead of transferring them
to another phase, as do air stripping,
granular activated carbon ((jACi adsorption, and reverse osmosis The
commercial feasibility of these processes is still uncertain.
Health effects studies
Several studies have attempted to determine the compounds formed by
ozonation alone and in combination
with other processes in natural waters.
Most of these studies have yielded no
surprises. Aldehydes, carboxylic acids,
and other aliphatic, aromatic, and
mixed oxidized forms have been observed. None appear to cause significant toxic effects at the concentrations
expected in ozonated waters (3.?)
Most bioassuy screening studies have
shown that ozonatcd water induces substantially less mutagenic activity than
chlorinated water docs One studs
showed that ozonation decreased inula
genie activity in Rhine River water,
whereas the activity increased after the
water was treated with chlorine and
chlorine dioxide (3). These studies do
not necessarily remove all concern
about the safety of ozonation for drinking-water treatment. There may very
well be byproducts formed that harm
human health: they simply have not yet
Ivcn Ituind. Il is instructive to recall
that chlorine was used for decades betore THMs were discovered in drinking water. The situation with ozone byproducts may be analogous.
All of the hcaldi effects studies carried out so far have used preconcentration techniques that may cause some
byproducts to decompose during workup. These byproducts include peroxides, epoxides, and conjugated unsaturated aldehydes. Further research is
needed if ozonation is to be adopted on
a large scale in the United States.
Ozone and biological treatment
The bypioducis lormed bv oxidation
with oz.nne and catalytic ozonation
processes arc generally more amenable
than are those formed by chlorination
processes to removal by biological
treatment processes—that is, diey are
more biodegradable than dieir precursors are. This is a disadvantage if ozone
is to be used as a terminal disinfectant.
If applied before filtration, however,
ozone can promote biological activity
in the filter that will remove organic
matter and THM precursors; in the final step, the water can be treated with
chlorine or another disinfectant.
Ozonation in advance of filtration
with GAC has been called the biological activated carbon process This combination of processes has been studied
in Western Europe {34-36), where it
was pioneered, and in North America
i37-3X) DiGiano recently reviewed
the subject and concluded that the com
bi:!.:i-":i "I pic></iin.iiii<u and OA( !il
tr.itii'ii l o i i m o "iL'anic substances but
ToSruction of chtorftwiKJ . a ^ ^ ^ ^ ^ ^ # f ^ f ^ 5 S S ^ 3 p
1.0
T^»»_^
Hoxachlorobiphenyt
OS
... Bromodichlofomethane
*te
I \ O
TricWo/omethane
0.6
d
o
0.4
""^ /
Hexachlorobiphenyl (UV)
i
'v
0.2
t Tnchloroethylene (UV)
Trichlo-ome.hane (UV)
'
\&J,'cr,loroethylene
Bromodichloromethane (UV)
10
20
30
40
Tirro (mln)
50
60
70
»A1 pH S-7. o a w o Awe nH« • 1.0-1.« mgrt mil; UV frequency I* 254 ran from «low-pressure marcury l«<np,
wi* « f l u x d 0 « J W/L
that the effect is not as dramatic as
some of its proponents claim {39).
Nonetheless, there arc several treatment plants in Europe that arc using the
ozone-GAC process, and active removal well beyond the period of GAC
exhaustion is reported (36). It is possible that the use of catalytic oxidation
processes will increase biodegradability
even more than ozone can alone.
Ozone system costs
Although ozone systems are capital
intensive, they offer significant economies of scale. Costs of generating and
^contacting systems vary from one site
to another, but about $240()/kg of
ozone/day is a plausible figure for a
plant producing 900 kg/day of ozone.
This would be enough to treat 100 million gal/day of water (4.4 m'/s) with an
ozone dose of 2 g/m' (2 ppm) and
would require a capital investment of
approximately $2 million. Capital costs
for systems gencialing 0-5 ku-'h ol
i!.-n:"cc aie .ib.ml tliicc times muse ih.tt
uenci.iic more than 5(lkiiih.
Operating costs of ozone plants also
vary, but a range of S0.001-S0.002 ; ni !
seems to IK- typical ol most plants in the
United Stales. Ozone production is energy intensive and requires 16kWh/kg
and 24 kWh/kg of ozone for oxygenand air-fed systems, respectively. Total
treatment costs for ozonation arc in the
range of S0.04/m:< to S0.06/m 3 of water
for plants that process 10 million-gal.'
day and 100 million-gal/day (0.44 mVs
and 4.4 nvVs). respectively, assuming
an ozone dose of 1 ppm.
\
For the future
It is likely that the use of ozone in
water treatment will increase substantially in North America. In the near future, its principal application is likely to
be similar to the new Los Angeles
plant, where ozone is used a coagulant
aid. Ozonation also will find new applications as a substitute for prechlorination for control of biofouling. taste and
cxlor control, and manganese removal.
pamculaiK it the m.ivimum contami"
nam levels (or THMs are lowered
Environ So Techno) Vol 21. No 3. 1987
229
The control of THM precursors,
groundwater chloroorganics, and other
synthetic organic materials by ozonation is not likely to be successful. Advanced catalytic ozonation processes,
however, are showing promise for such
applications and will be studied more
thoroughly.
As the use of ozone for drinking-water treatment increases, particular attention will have to be paid to the use of
appropriate analytical methods and separation procedures that will give an ac
curate representation of the substances
present after oxidation—not just those
that survive the work-up procedures
Of the byproducts of particular interest,
unsaturated aldehydes, epoxides, and
peroxides are the most likely to cause
harm.
As advanced oxidation processes are
evaluated further, it is possible that new
ozone contacting systems will emerge
to take advantage of the inherent rapid
mass transfer and chemical reaction
rates of radical processes. New designs
that combine ozom gcneraiio. with
ozone. UV. and peroxide injection may
emerge as the best commercial prospects for advanced oxidation processes
in water and wastewater treatment.
«•
I
References
(1) Rice. k . G . In Safe Drinking Water: The
Impact of Chemicals <m a Umited Resource:
Rice, R. G. Ed.; Lewis Publishers: 1985:
pp. 123-59.
(2) Prcndiville. P. W. Ozone Sci. Eng 1986, 8.
77-93
(3) Zocleman. B C. el ai. Environ. Health
Perspect. 1982, 46. 197-205.
(4) Coste. C : Fiessinger. F. In AWWA Proceedings, Ozonation: Recent Advances and
Research Needs; American Water Works Association' Denver, in press
(5) Staehclin, J ; Hoigne. J Environ Sci
Technol 1982, 16 676-81
Ifil Sprou!. O.J
(n AWWA
Proceedings.
(i;onutiin\
Recent Advances tinti Research
Needs. American Water Works Association
Denver. ;n press
(7) Monk. R D G ct al. J Am. Water WorkAssoc. 1985. 77. 49-54
(8) Reckon. D. A In AWWA Proceedings
Ozonation: Recent Advances and Research
Needs: American Water Works Association:
Denver, in press.
(9) Hoigne. J.; Bader. H Water Res 1983. / 7.
173-83
(10) Hoigne, J.. Badcr. H Water Res. 1983,
17. 185-94
(11) Rice. R. G In AWWA Proceedings. Ozonation: Recent Advances and Research Needs:
American Water Works Association: Denver,
in press.
(12) Staehclin, J.; Hoigne, J. Environ. Sci
Technol. 1982, 16. 17-22
(13) Buhler. R E . ; Staehelin. J ; Hoigne. J
J. Phys. Chem. 1984, 88. 2560-64.
(14) Staehelin. J.; Buhler, R E . ; Hoigne. J.
J. Phys. Chem 1984, 88. 5999-6004.
(15) Forni, L.: Bahnemann. D.; Hart, E.J
J Phvs. Chem. 1982, 86. 255-59.
(16) Taube. H : Bray. W,C, J Am. Chem
So, 1940, 62. 3357-73.
(17) Staehclin, J ; Hoigne. J. Vom Wasser
1983, 61. 337-48
(IK) Gurol. M D ; Singer. P C Watei Res
1983, 17. 1173-81
(19) Staehelin. J.. Hoigne. J. Environ Set
Techno} 198S, 19. 1206-13
230
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(20) Bliley, P. S. In Ozonation in Organic
Chemistry, Vol. I, OUfinic Compounds; Academic Press: New York, 1978, pp. 15-37.
(21) Bailey, P S . In Ozonation in Organic
Chemistry, Vol. II. Nonolefnic
Compounds;
Academic Press: New York, 1982; pp. 1842;371-422.
(22) Garrison, R. L., Mauk, C. E; Prcngle,
H. W , Jr. In First International
Symposium
on Ozone for Water and Wasle*Kiter Treatment; R i « , G. G.; Browning, M. E.. Eds.;
International Ozone Association: Vienna,
Va., 1975; pp. 551-77
(23) Peyton. G. R el al Environ. Set. Technol 1982, !6. 448-53
• 24) Glaze. W H. et al. Environ Sci Technol.
1982, 16. 454 58
:.'.5) Peyton. G R Glaze W H. In PhoirchemislD of Environmental
Aauatn Svs
terns; Zika. R G.: Cooper. W. J Eds.. ACS
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88
i.'61-Sicrka. K A Ann H I
'.-•••), v .
Eng. 198S, T. 47 rO
i27) Nakayaniii. S. el al (».."i. Si i rny
1979, /. 119-31
l28) Duguet. J. R et al Ozone Sci Eng. 1985.
7.241-58.
(29) Chen J W el al AlChE Svmp Ser
1977, 73. 206.
(30) Brunei. R.; Bourbigot. M M ; Dore. M
Ozone Sci. Eng. 1984,6. 163-83
(M) Ohze. W H e> al "Pilot Scale Evalua
imp. of Pb'M'.Oyt.'C Ozonation tor Inhaio
methane Precursor Removal." Report of Co
operative Agreement CR-80M25: EPA-MXV
52-84-136. NT1S PB84234517: Municipal
Environmental Research Laboratory. FPA
Cincinnati. 1984.
(32) Taube. H Trans. Earad,i\ So, 1957. 5.«.
656.
(33) Glaze. W. H. Environ. Health Perspect.
1986,69. 151-57
(34) Sontheimcr, H Translations of Reports
on Special Problems of Water Treatment —
Vol. 9. Adsorption. EPA-600/9-76-030. Municipal Environmental Research Laboratory.
EPA: Cincinnati, 1975.
(35) Eberhardt, M. N.; Madsen. S.: Soni
heimer, H. "Untersuchungcn zur Vcrwendung Biologisch Arbeilender Aklivkohlcfilter bei der Trinkwasscraufbereitcnder." Report 7; Englcr-Bunle-Inslitut, Karlsruhe
University: Karlsruhe. West Germany. 1974
(36) Rice, R. G. el al "Biological Processed
in the Treatment ol Municipal Water Sup
plies." EPA-6(X)/2-X0-l98n: Municipal Kr.
vironmental Research Laboratory. LPA
Cincinnati, 1980.
(37) Glaze. W. H.; Wallace. J. L. J. Am Water Works Assoc. 1984, 76. 68-75.
(38) Maloney. S. W. et al. J Am. Water Works
Assoc. 1985, 77. 66-73.
(39) DiGiano, F. In AWWA
Proceedings.
Ozonation: Recent Advances and Research
Needs; American Water Works Association:
Denver, in press.
William li. daze
is professor
of publit
health and director of the
Environmental
Science
and Engineering
Program
ai
UCl-A. He is a /iriniiptil
investigator
for
projects
cumerninf!
nilulytit
ozonation
water treatment
proi esses, among
other
areas.
'?' 1/
ORGANIZACION PANAMERICANA DE LA SALUD
-OPSUN I DAD EJECUTORA DEL PROGRAM DE ACUEDUCTOS RURALES
-UNEPAR-
DESINFECCION CON GASES OXIDANTES
PROYECTO MOGGOD
REGION ORIENTAL UNEPAR, GUATEMALA
ING. JOSE GILBERTO GONZALEZ DE LEON
I
1. ANTECEDENTES.
El presente estudio se desarrolló bajo loa lincamientos
del "PROYECTO DE COOPERACIÓN TÉCNICA PARA LA EJECUCIÓN DE UN
PROYECTO DE DEMOSTRACIÓN DE MEJORAMIENTO DE LA DESINFECCIÓN
DE SISTEMAS DE AGUA POTABLE DE PEQUERAS COMUNIDADES Y PUEBLOS
A TRAVÉS DEL MOGGOD".
Dicha acción ae debe a la promoción que la Organización
Panamericana de la Salud, OPS, ha venido desarrollando parael uso de tecnología apropiada para la desinfección del agua
en comunidades pequeñas.
Dentro de esta política, OPS y CEPIS, han patrocinado
diversas investigaciones en el campo de la desinfección del
agua. Una de ellas in<Uca al momento que los gases oxidan—
tes In situ (MOGGOD), parece ser una de las tecnologías con
más perspectivas de ser empleada.
Diversas experiencias se han realizado con la desinfección MOGGOD y en diversos países, hasta que en septiembre de
19^7 se realizó un convenio entre el Gobierno de Guatemala,
representado por el Instituto de Fomento Municipal INFOM y
la Unidad Ejecutora del Programa de Acueductos Rurales UNEPAR, la Organización Panamericana de la Salud a través del
Programa de Salud Ambiental y el Programa de las Naciones Unidad para el Desarrollo, celebraron el convenio del proyecto mencionado al inicio, con los siguientes aspectos:
1.1 CONSIDERANDOS:
- Que el PNUD ha aprobado la propuesta de Proyecto de D_e
mostración de Mejoramiento de la Desinfección de Sistl?
mas de^Agua Potable de Pequeñas Comunidades y Pueblos""
a través del MOGGOD y ha proporcionado fondos inicia—
les para acciones preparativas de la OPS/HPE en los
países colaborantes.
- Que la inadecuada desinfección de agua potable es un
problema de salud pública muy serio.
- Que el MOGGOD tiene buen potencial para evitar o dismi
nuir restricciones existentes contra desinfección deX
agua potable.
» Que el Gobierno y OPS/HPE tienen interés en la explora
clon de"posibilidades de la fabricación del MOGGOD en
el país.
•1
m
Que el Gobierno y OPS/HPE ti enen interés en el desarro
lio de la tecnología del MOGGOD en el contexto del país
- Que elpaís tiene la capacidad tecnológica parainstalar,
operar, monitorear, analizar, evaluar el MOGGOD, tecnolo
gía y dispositivos y hacer recomendaciones para mejorar
el MOGGOD.
Derivados de los Considerandos, se determinaron claramente
las responsabilidades de la OPS,y del INFOM-UNEPAR, las
cuales ae detallan a continuación;
1.2 RESPONSABILIDADES DE LA OPS:
- Comprar 2 unidades del dispositivo MOGGOD y repues—
tos esenciales y entregar dos unidades al Instituto
de Fomento Municipal (INFOM) y una unidad a la Uni—
dad Ejecutora del Programa de Acueductos Rurales
(UNEPAR).
- Proporcionar a la agencia colaborante las instrucci£
nes para la instalación del MOGGOD.
*~
- Preparar y entregar manuales de operación y mantenimiento del MOGGOD en español.
- Colaborar técnicamente con las agencias/instituciones apropiadas en los asuntos técnicos del MOGGOD re
lativos a su instalación, operación, mantenimiento,""
vigilancia, demostración y desarrollo.
- Proporcionar material para educación de los ingenieros y operadores.
- Establecer con las agencias colaborantes el protocolo para monitorear la eficiencia, efectividad, durabilidad, costos, consumo de sal y electricidad.
- Establecer con la agencia colaborante los protocolos
para monitorear el nivel de desinfectante'y determinar la duración del desinfectante residual.
- Recolectar y analizar la información y datos generados por todas la3 agencias y países e intercambiarlas
con todos los participantes.
\- Proporcionar criterios de selección de comunidades
\ para participar en este proyecto de demostración.
- Proporcionar ayuda técnica sobre la fabricación
dal del dispositivo de MOGGOD.
lo-
2
- Diseminar nueva información técnica en relación de
las investigaciones actuales y avances científicos
de MOGGOD.
- Proporcionar sal común (cloruro de sodio) de pureza
adecuada para los dos primeros años de operación de
los equipos.
1,3 RESPONSABILIDADES DEL INFOM Y DE UNEPAR:
- Seleccionar comunidades apropiadas para participar
en este proyecto de demostración bajo los criterios
para la selección.
- Obtener compromisos y negociar acuerdos con las comunidades para su participación.
- Instalar los dispositivos MOGGOD de acuerdo con la3
guías proporcionadas por OPS.
- Recolección y análisis de información y los datos £
perativos necesarios para determinar los costos y "~
el consumo:
a) de la sal,
b) de la electricidad,
c) del agua para electrólisis, por metro cúbico del
agua tratada.
- Determinar la mínima residual práctica para asegu—
rar agua libre de patógenos.
- Determinar las horas requeridas por mes para operación y mantenimiento,
- Determinar en cada sistema la disminución, del residual en la red de distribución.
- Monitorear la operación y mantenimiento del M6GGOD.
- Identificar las fuentes de sal y su pureza.
- Formular recomendaciones^para mejorar el dispositivo MOGGOD y su instalación así como la operación.
- Hacer\ recomendaciones sobre la factibilidad de
bricación del MOGGOD en el país.
fa-
- Preparar informes trimestrales sobre el progreso
del proyecto de demostración.
2. OBJETIVOS,
El objetivo principal de este informe es presentar las
experiencias, en relación a la desinfección utilizando la
"MEZCLA DE GASES OXIDANTES GENERADOS TU S I W .
Ello implicará la relación cuasi cronológica y detalla
da de I03 diferentes pasos que hubo que dar, desde la cele"
bración del convenio hasta el inicio de operación del equipo seleccionado y el seguimiento a que se sometió para controlar las diferentes'variables que intervienen en el con—
junto de experiencias.
'
De igual manera previo a la relación, se incluirá 'una
información general que permita ubicar al amable lector, en
el contexto en que se desarrolló la investigación preliminar.
3. MARCO GEOGRÁFICO Y POBLACIÓN AL.
La República de Guatemala tiene un área de 108,689 Km2 y se
encuentra localizada al norte de la América Central entre
13° 44 y 17° 50' latitud norte y 88° 33* y 92° 13' longitud
oeste. La densidad media* de población es de 70 habitantes
por Km^.
En 1986 l a R e p ú b l i c a de Guatemala a l c a n z ó una p o b l a c i ó n de
¿.1951.117 h a b i t a n t e s , con una t a s a de c r e c i m i e n t o a n u a l de
Z.7$ %.
,
La d i s t r i b u c i ó n t o t a l de p o b l a c i ó n p o r sexo se p r e s e n t a en
la gráfica siguiente:
GRÁFICA 1
POBLACIÓN YHJCrRÜEÍs(TlJE POR SEXO
¿&0 1966
SEXO
\
POBLACIÓN
No.
TOTAL
5,195,117
MASCULINO
4.143,071
FEMENINO
4.052,046
\
i
100.
50.6
49.4
i —
FUENTE: Guatemala en C i r r a s de S a l u d , MSP y AS.
La población total se encuentra dispersa en unos
1# 640 nu'"leos d Q población, de los cuales 9&% tiene menos
de'2,000 habitantes.
E303 núcleos poblacionales comprenden aproximadamente
el 64$ de I a población total.
La población está dividida en sector urbano y rural,
por definición, se entiende por población urbana, la que
habita en lftS 326 cabeceras municipales y la ciudad capi—
tal.
4. MARCO INSTITUCIONAL.
UNEPAR, e s la Unidad Ejecutora del Programa de Acue—
ductos Rurales. Es una dependencia del Ministerio de S a —
lud Publica y Asistencia Social.
Fue creada e*1 1975, sustituyendo al Departamento de Inge—
niería Sagitaria de la División de Saneamiento Ambiental.
Opera a ni-VQl de Dirección, dependiendo directamente del
Ministerio de Salud Pública y Asistencia Social.
Como objetivo fundamental UNEPAR tiene'el proveer agua potable al#sector de ],a población rural; trabajando
con los "Comités Oficiales de Agua Potable", quienes se con
vierten eA el enlace dinámico entre la institución y las co
munidades*
UNEPAR,atiende t o d o s l o s departamentos de l a R e p ú b l i c a
con excepción de El P e t e n , e j e r c i e n d o su acción a t r a v é s
de!
- Dit*ecclón y Administración con sede en la ciudad capital.
- Re/íi°n Central, con sede en la ciudad de Guatemala.
- Región Oriental, con sede en la ciudad de Chiquimula
- Región Norte, con sede en la ciudad de Cobán.
- Región Occidental, con sede en la ciudad de' Quetzalten ango.
$* REGIÓN ORXjNIAIj.
En el presente infórmele hará una ampliación sobre es
Región, dndo que la Dirección de UNEPAR delegó la responsabilidad do la experiencia del MOGGOD en ella.
5.1
COBEKTURA. ^
\ •
La Región Oriental, desarrolla-su acción én 4 departamentos de la Zona\Nor-Orieñtal, cubriendo una superficie estimada de 12\,530 Km2.
La gráfica No. 2 muestra el mapa de la República
de Guatemala, con el área de acción de la Región.
5
QRAFICA ffo. 2
REPUBLICA DE GUATEMALA
•
Un detalle de esa área se presenta en la gráfica No.- 3
La cobertura de servicios en cada uno de los departamentos se muestra respectivamente así:
- Gráfica No, 4:
El Progreso.
- Gráfica No. 5:
Zacapa.
- Gráfica No, 6:
Chiquimula.
- Gráfica No. 7: Izabal.
La gráfica No. 8 presenta un resumen cuantitativo de a
tención,
"~
GRÁFICA No. 8
COBERTURA REGIÓN ORIENTAL
DEPARTAMENTOS - MUNICIPIOS - COMUNIDADES
DEPARTAMENTO
MUNICIPIOS
ATENDIDOS
SISTEMAS
CONSTRUIDOS
COMUNIDADES
BENEFICIADAS
CHIQUIMULA
11
17
31
ZACAPA
10
14
33
IZABAL
4
25
4o
EL PROGRESO
5
6
10
r
TOTALES:
30
62
114
FUENTE: Región Oriental de UNEPAR
6.
DESARROLLO DE LA INVESTIGACIÓN.
De acuerdo con lo s términos del convenio firmado en
Septiembre del 87, se' tuvo conocimiento que el CEPIS orga—
nizaría en Lima.,Perú, el "Primer Seminario Internacional
sobre Desinfección por Oxidantes Mezclados". La participación en dicho seminar!o llevaba implíci\to el presentar algu
ñas experiencias, por lo que la Dirección de UNEPAR, désig~
nó al suscrito#para re alizar la investigación de campo,
Se recibió a fina les de Octubre el equipo y se comenzó
a elaborar las estrategias de trabajo, las cuales se descri
birán a continuación:
7
QEAFICA Ho, 3
0CB?:an:-RA R S J I ; iT C R U ^ A L
MUNICH MC3
3A
SlTi'^/iS
• ' 2 - \
'JC i-:L:"; i DA J:J3
;OJL.W^:;
ii^^.vicj.-.j..
114-
7L3,33('
CfRAPICA F o . 4
i-n-'iiioirios
•" 1 ^
'V, •• . .
c
COMlFii),* IXiS
rci'L^cio'i :i-;:."j.;,iCj'-;D:'i
5
6
10
9,933
9
QRAJICA Ho. 5
J J i A;ti'A,-; J" .11' DU ^AC.li'A
r.u::ic;irJ.C5
1C
SIL'TJ-:A:3
H
CO;:U-'1UA)^
33
iCiJiAJU;:: - • ^ ^ . . V . I A D A
1V*7
10
QRAFICA Ho. 6
D E P ^ i f ^ r ' P O 13 C'.il.t'JJi.iULA
MUiiiciPicg
11
SIGO-IAS
17
CC»'.U'TJ DA D.23
31
F0 3LAGIC'n DTCFiCUDA
18,1^5
11
ORJLPICA. N o . 7
)J1 A.'i'i'Ai .Z.. i'C JZ
l^AJ-Jj
1". : : ..r;ir*fi i i l
5
I-iUniCli'lOS
23
cv.:u':'i.")/,jj.i
IT:-L". C i C: ^ ' " ' i n T L ^ A
*; v-
-'••
-
>
-
-
•
-
".TV
6.1 EQUIPO
La unidad "0X1" producido por Oxidizers Inc, 4990
Euclid Road, Virginia Beach, VA 23^62 entregado a
UNEPAR, es una unidad que consta de una celda electrolítica.
La gráfica No. 9 muestra una reproducción de la celda
con sus componentes. En esta celda se produce una mejz
cía de oxidantes consistentes en cloro, oxígeno y perjo
xido de hidrógeno en el compratimiento del ánodo.
~"
^En el compartimiento del cátodo la celda produce
hidrógeno én forma gaseosa e hidróxido de sodio en for
ma líquida.
""
El ánodo y el cátodo están separados por una membrana semipermeable.
La otra parte de la unidad es un autotransformador de corriente que utiliza 110 - 120 VAC a 60 Hz. La
gráfica No. 10 muestra el autotransformador en vista
anterior y posterior.
6.2 OPERACIÓN DEL EQUIPO.
La unidad MOGGOD utiliza cristales'de hidróxido
de^sodio en el compartimiento del ánodo, ambos en solji
ción con agua destilada.
'
""
La sal debe ser de alta calidad, es decir cumplir
con las normas^Sterling TNA5 u otro equivalente con ba
ja concentración de calcio.
"~
La electrólisis de estas dos soluciones a un gasto
energético de 3 a 10 voltios produce compuestos oxidan
tes mencionados anteriormente.
"~
Los elementos oxígeno y cloro oon absorvidos fuera del ánodo por un tubo de Polipropileno conectado a
un venturi.
Para la investigación se utilizó un inyector
MAZZEL, el cual se instaló cerca del punto de restricción creado por una válvula de compuerta, con lo cual
se crea una presión diferencial la cual no debe ser me
ñor del ZU% para que se produzca el vacío que succione
los oxidantes producidos.
La instalación la muestra la gráfica No. 11
El exceso de hidróxido de sodio líquido producido
en el proceso es drenado tal y como muestra la gráfica
No. 11.
El gas hidrogeno proveniente del cátodo es más 1JL
viano que el aire y es eliminado a la atmósfera por un
sistema de ventilación ubicado en el techo de la insta
lación.
"
f
La generación de gasees controlada por por la
electrólisis de la solución. La velocidad de la electrólisis se controla variando la corriente eléctrica 13
ORIFICA Ho. 9
CELDA ELECTROLÍTICA
1. Compartimiento del ánodo
2. Compartimiento del cátodo
3. Orificio/agua soda caustica
4. Tapón plástico orificio 3
5. Orificio/agua sal
6. Tapón plástico orificio 5
7. Visor del nirel de sal
8. Drenaje de soluoión de sal
9. Membrana semipermeable
10. SrJida de mesóla de gases
11. Drenaje de coda caustica
12. Ventilación del hidrogeno
QRAFICA N o .
10
AUTOTEANSroEMADOR
[
4MP5
-(LO)*y^y^
VOIT5
0 3
VISTA ANTERIOR
VISTA POSTERIOR
1. Boton do oontrol v o l t a j e
2. Kedidor de c o r r i e n t e (cjaporios)
3 . F u s i b l e ( 3 amporios)
4» Cordon de Corriemte
5 . Conootoroa de e a l i d a o o i r i e n t e D.C.
ORAFICA N o . 1 1
m
INST1LACI0H KiUIPO
i
16
que fluye por los electrodos y a su vez la corriente eléctrica se controla cambiando el voltaje usando un f
reóstato o botón de control como se muestra en la grafi
ca No. 10.
~"
Con lo dicho anteriormente se concluye que el d e —
sinfcctsjite residual que se d©sce, se obtiene ajustando
únicamente el botón de control del autotransformador.
Este residual se lee con un comparador en el sistema de
distribución
6.3 SELECCIÓN DE LA COMUNIDAD,
Dentro de la responsabilidad de UNEPAR, quedó la
selección de la comunidad para desarrollar la investiga
ción.
El criterio de selección quedaba determinado por
los siguientes parámetros.
- Ubicación:
Lo suficientemente cerca de un laboratorio con capacJL
dad para hacer análisis bactriológicos y próxima a la
Oficina Regional para facilitar el seguimiento.
- Tamaño de la población *
W£r'9~5üü y lZOTThabitantes.
- Servicios existentes:
Energía eléctrica y un sistema de agua con redes de
distribución para un servicio continuo.
- Calidad bacteriológica y físico-química del agua:
Agua con necesidad de desinfección y bajo nivel de tur
biedad.
"*
"* Organización de la comunidad:
L"a comunidad debe contar con una junta administradora
o Comité de Agua Potable y proporcionar un operador
de la unidad de desinfección.
En base en los aspectos anteriores y revisando el
inventario de comunidades abastecidad con sistemas de
agua potable oe seleccionó la aldea PUEBLO NUEVO, en el
municipio de Usumatlán, del departamento de Zacapa.
Las características que la población reunía se des
criben a continuación:
~
- UBICACIÓN:
La comunidad se encuentra a la altura del kilómetro
114 de la carretera CA-9 Norte y a 56^kilómetros de la
ciudad do Chiquimula. sede da la Región Oriental de
UNEPAR.
17
En la ciudad se contó con la colaboración del laboratorio de la Jefatura de Área de Salud y'del laboratorio
del Centro,Unlvesitario del Nor-Oriente, CUNORI.
La población se encuentra en la cuenca del Río Motagua,
el río más grande de Guatemala y en sus orillas corre
el Río La Palmilla que aguas arriba permite la obra de
captación que surte el sistema de agua. Dista de la
cabecera Municipal, Usumatlán, 8 kilómetros y de la c¿
becera departamental. Zacapa, hO kilómetros.
La situación puede observarse en la gráfica No. 12.
TAMAfiO DE LA POBLACIÓN;
Estudios hechos para el mejoramiento del actual acue—
ducto, indican que cuenta con 90 viviendas con una estimación, de 5^0 habitantes en la zona de mayor concentración,
SERVICIOS EXISTENTES!
Carretera de terracería con una longitud de 2 kilómetros que interconecta con la carretera CA-9 Norte.
Escuela y edificios religiosos (dos).
Energía Eléctrica a nivel domiciliar. Se carece de alumbrado público. '
Servicios de Salud, prestados por el puesto de Salud
de la Cabecera Municipal.
Sistema de Agua potable, construido en 1976, con capta
ción de fuente superficial sin tratamiento. El servia
ció cuenta actualmente con 60 conexiones domiciliares,
un tanque de almacenamiento de 30 M3¿ con un caudal de
entrada de 1.4 L/S equivalente a 120,960 litros dia
rios y una longitud total de 4506.00 metros de tubería
instalada.
CALIDAD BACTERIOLÓGICA;
Siendo una fuente superficial era de esperarse que existiera algún rango de contaminación, sobremodo porque en los alrededores de la obra de captación hay 6
viviendas que utilizan el agua del río La Palmilla para resolver todas sus necesidades.
Efectuado el análisis se comprobó la hipótesis y la
gráfica No. 13, muestra el resultado del análisis previo a la investigación.
No fue posible analizar y comparar la turbiedad y color con los patrones usuales, pero a simple vista el
agua presenta un aspecto libre de turbiedad e incolora,
ORGANIZACIÓN COMUNAL;
Ta comunidad cuenta con un Comité Pro-Mejoramiento, cu
yos miembros sobre todo el Presidente y Vico-Presiden^
te, prestaron una colaboración y un entusiasmo encomLa
ble al desarrollo de la experiencia. El Vicepresidente fue el operador auxiliar en el control y manteni
miento del equipo.
18
GRAFICA N o .
12
MUNIC1PI0 J)E USUMATUN
\
PUEBLO HUEVD
\
\
CORSTRUCCION 3I3TEMA
C0HEXI0HE3 DO!JICILIJ?.RES
TUBERIA IHSTALADA
CAUDAL DISPONIBLE
1,976
60
4,506 Mta
1.4 L/S
GRAFICA No. 13
RESUMEN DE RESULTADOS
ANALISIS BACTERIOLOGICOS
^\FECHAS
CONDICIONES\^
27-10-87
N o . MEMBRANAS
FILTRANTES
2
MEDIO
SELECTIVO
EN DO
VOLUMEN
MUESTRA
25
N o . COLONIAS
COLIFORMES
COLIFORMES
p / 1 0 0 Ml
TIEMPO
INC.
\
.._. ......
216
12-11-87 19-11-87
2
. ENDO
25
25-11-87
2
2
ENDO
ENDO
25
25
68
0
1,700
0
24 Hrs.
24 H r s .
*
5,400
24 Hra.
r
24 H r s .
6.4
INSTALACIÓN DEL EQUIPO:
P a r a r e a l i z a r e l m o n t a j e , se e s c o g i ó un punto de
l a l í n e a de conducción s i t u a d o a 15.00 m. d e l t a n q u e
de almacenamiento. Se d i s e ñ ó l a c a s e t a de p r o t e c c i ó n
del equipo, siguiendo l a s instrucciones del f a b r i c a n t e
en cuanto a l a v e n t i l a c i ó n i n f e r i o r y s u p e r i o r p a r a evacuación de l o s g a s e s t a n t o l o s l i v i a n o s y pesados en
relación al a i r e .
Las d i m e n s i o n e s de l a c a s e t a f u e r o n :
- Largo: 1.20 m.
- Ancho: 1.20 m;
- Alto: 2.00 ra.
Fué construida con blocks de concreto de 0.20x0.20
x0.40 m. y una cubierta de lámina galvanizada.
Se proveyó de una caja de registro, utilizada como fesumidero del rebalse del hldróxido de sodio líquido.
Las do3 unidades del equipo fueron colocadas en planchas de concreto a 1.40 m. del nivel del suelo.
La colocación del venturi ya se ilustró anteriormente
en la gráfica No. 11.
6.5
GASTOS DE INSTALACIÓN Y MONTAJE:
4
La instalación y montaje del equipo, exigió diver
sas actividades e inversiones las cuales se enumeran 'a
continuación:
6.5.1 MATERIALES CONSTRUCCIÓN CASETA:
Arena de río
Blóck cemento 0.20x0.20
xO.40
Bolsas de cemento
Bolsas de cal
Varillas de hierro 3/8
Alambre amarre calibre 18
Clavo de 3»
Clavo de lámina
Lámina 6»
Bisagras 3"
Puerta
Candado
Mv
0,5
U
100
qq
6
qq
1
U "
6
Lb;
5
Lb.
5
Lb.
1
U
3
U
2
U
1
U
1
TOTAL:
Q. 9.00
» 45.00
" 44.30
"
4.50
", 2 3 ; 54
»' 4 . 0 0
"
4.00
» 0.6*0
« 10.80
» 2.00
" 50.00
" 15.00
Q212.9^
21
6.5.2 MATERIALES Y ACCESORIOS INSTALACION EQUIPO:
Llaves de paso de 1/2"
Valvula de compuerta de
2"
Adaptadores Macho PVC
de 2"
Adaptadores Macho PVC
de 1 1/2"
Tees Reductora3 PVC de
2" x 1/2"
Codoa PVC de 1/2" x 90°
Tubo PVC de 2" 160 PSI
Tubo PVC de 1/2"
S o l v e n t e p a r a PVC r f g i d o
Alambre c a l i b r e 10
C l n t a de a i s l a r
Cinta teflon
Toma c o r r i e n t e
A i s l a d o r e s de 1 1/2"
F l i p - u n 15 Amp.
u
u
2
Q.
1
tf
104.00
u
2
it
5.44
u
4
it
5.73
u
u
TUEO
2
2
1
1
tt
9.65
1.14
30;12
TUBO
•
_
«
.
.
.
.
m.
U
U
U
U
U
.
i/a
140
1
1
1
14
1
TOTAL:
ii
it
it
ti
n
it
6.50
7;oo
8:45
9i;oo
2;50
2:50
tf
2;95
n
10.50
».
14.50
Q. 302.03
it
6.5.3 HERRAMIENTA Y EQUIPO;
-
Prensa de banco de 2"
Llaves Stilson No. 24
Cubetas para concreto
Nivel
Plomada
Cuchara de albafiil
Piochas
Palas punta redonda
Escuadrilongo
NOTAJ
1/2"
1
2
4
1
2
3
3
3
1
Eate equipo fue p r o p o r c i o n a d o ' p o r l a Region
O r i e n t a l de UNEPAR, s i n c o a t o .
6 . 5 . 4 EQUIPO ESPECIFICO Y REACTIVO:
- Comparfmetro
- Yodur.o de potasio
- Almidon
«- ForrnolX
- Soda caustica
- Hipoclorito de calcio
65*
-\
- Agua deatilada
- Cristalerfa
u
gr.
ti
3
*"
6.42
2
14
ti
-
it
13;00
26.21
5.00
87.43
—
gi*:
ml.
Lb,
Lb.
Lts.
-
1
40
TOTAL:
Q.
»t
it
it
Q.
20.00
10.00
0.20
l;6o
22
6.5.5
MANODEOBRA:
Instalacion
5 o p e r a r i o s / 5 df as
Seguimiento c o n t r o l tnueatrass
1 p e r s o n a / 3 d£as
Operacion Equlpo
1 persona /15 dfas
TOTAL:
6.5.6
Q. 200.00
it
30.00
it
169.95
Q. 399.95
TRANSPORTE:
- Viajes de 140 Kms.
- Viajes de 140 Km3.
7
2
TOTAL:
Q. 203.00
17*4o
Q. 220.40
if.
6.6 OPERACION Y SEGUIMIENTO:
•
—
—
—
—
—
—
—
—
•
«
.
-
—
•
—
—
_
_
_
_
_
_
_
—
.
t
La puesta en accion del equlpo de deslnfeccion, se
realizo slguiendo la3 instrucclones proporcionadas por
el fabricante. Hubo .dudas e incertidumbres, las cuales
fueron 3ubsanadas durante la operacion, la'cual confirmo o indico la3/modificaclones pertinentes.
La operacion y seguimiento se realizo en diferen—
tes^etapas y con mecanismos de'control adecuados al #al
parametro que se deseaba medir, los cuales se trataran
de describir en las slguientes lfneas.
6 . 6 . 1 ANALISIS BACTERI0L00IC03:
Para determinar la bondad y/o en su caso ine^
ficacia del equipo se practicaron analisis bacteriologicos antes y durante la investigacion.
En la grafica No. 13 se muestra la tendencia de
los analisis^practicados, los cuales se practicaron con el metodo de las Mombranas Filtrantes.
6 . 6 . 2 DETERMBJACION DE DEMANDA DE CLORO:
Se utilizo un metodo de carapo con lo cual se
obtiene una dete rminacion ^aproximada.
El^proc edimi en to consistio en preparaf una solu—
cion que conttivi era 1 gr/lit de cloro. Esta solu
cion se prepare en laboratorio con hipoclorito de
calcio al 65/6 y\ se agrego al agua que se iba a s£
meter al tratamx*ento, para determinar por* comparla
cion la cantidad de cloro necesaria para el trata
miento.
23
GRAFICA N o . 1 4
RESUMES GENERAL OASTOS DIBECTOS
RSNQLOir
MOHTO
MATERIALES CASETA
212.94
HATERIALE3 IRSTALACION
302.03
BQUIPO T REACTIVCS
87.43
HAHO OBRA
399.95
TRAN3P0RTE
220.40
SUBTOTAL
IMPKEVISTOS 1C^t
TOTAL
1222.75
122.2b
1345.03
6.6.3 OPERAGION DEL EQUIPO:
Se inicio de acuerdo con las especificaciones del fabricante y paralelamente se iniciaron
los controles de los diferentes parametros involucrados en la experiencia, los cuales se mues—
tran en los siguientes graficos:
- Lectura de gravedad especffica del Na OH, grafico No. 15.' Las lecturas fueron hechas tres
veces al dfa.
- Lectura de gravedad especifica del Na U, grafi^
co No. 16. Las lecturas fueron hechas tres v_e
ces al dfa.
s
*
- Control^de cloro residual, grafico No. 17. Se
practico una lectura por dfa en diferentes pun
toa de la red de distribucion,
"~
- Control del Ph, grafico No. 17. Se practico
una lectura *por dfa, juntamente con lectura del
cloro residual.
- Demanda de Na OH en gr, grafico No.*13.
ca el consume del hidroxido por dfa.
• >
Indi•
- Demanda de Na C/ en Lb. , grafico No. 13. Indi
ca el con sumo de sal por dfa.
"~
4
- Demanda de Energfa Electrica, grafico No. 19.
Este dato globaliza el con3umo total diario de
energfa electrica en kilowatios. El consumo
diario incluye la utilizacion de la energfa ga
ra el alumbrado de la vivienda y aparatps elec[
tricos (radio-grabadora).
"~
RESULTADOS!
' Es prematuro emitir opinion sobre resaltados fina
les, los cuales se consideren concluyentes, sobre todo
por el'poco tiempo que hubo disponible para la invest^
gacion.
\
Los resultados obtenidos ppr
otra parte seran vis_
tos un tanto subjetivamente porxel autor de e3te infor
me, dado que fue el conductor de\la experiencia. Sin
embargo se tratara en lo posible lograr el mayor grado
de objetividad.
-\
Teniendo en cuanta lo positivo que sera el llegar
a conclusiones imparciales que beneficien al area r u —
ral de nuestros pafses.
25
T^-
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27
QRAPICA No. 17
CONTROL CLORO RESIDUAL Y Ph
DIA
AMPERAJE
UN I DAD
LECTURA COMPARIMETRO
CLORO RESIDUAL
Ph
1
7
2
6
0.3
7.6
3
5
0.3
3.2
4
6
0>
7.6
5
6
6
<
0.4
*
0.4
3.2
6
0.4
7.3
7
6
0.3
3.2
3
6
0.4
3.2
9
6
<
0.4
7.6
10
6
<. 0.4
8.2
11
6
0.4
8.2
12
-
-
-
13
—
-
—
14
6
0.4
v.
15
6
0.4
77.8
^N _
\
<
?.<•'
HP. A FTC A !Ir>.
1.3
"COKSUMO REACTIVDS"
DIA
SODA
SAL
1
42.9
grs.
8 Oz.
2
85.8
Qrs.
8 Oz.
3
42.9
gra.
8 Oz.
4
42.9
ffra.
8 Oz.
5
75.0
grs.'
6 Oz.
6
64.3
£TS.
6 Oz.
7
64O
grs.
6 Oz.
8
42.9 ffTS.
8 Oz.
9
42.9
ffrs.
8 Oz.
-
8 Oz.
10
*
11
_. — —
12
-
-
-
13
-
-
-.
H
.-
-
-
15
8 Oz.
_ _ _
12 Oz.
\
8 Oz.
\
-
29
GRAFIGA No. 19
CONSUMO EtfEHQIA ELECTBICA
LECTUBA
IFICIAL
LECTUBA
PINAL
COHSUMO
1
404
406
2 KT.
2
406
403
2 KT.
3
408
409
1 KT.
4
409
411
2 KT.
5
411
413
2 KT.
6
413
415
2 KT.
7
415
417
2 KT.
a
417
419
2 Kv.
9
419
422
3 Kv.
10
422
424
2 KT.
11
424
426
2 KT.
DIA
:
.
12
-
-
-
13
-
-
-
14
426
431
5 KT.
«
431
434 -
3 Kr,
I
6.7.1 A3PECT0S CUALITATIVOS:
•• Partiendo de cero, la experiencia fue sumamente^valioaa ya que fue posible poner en opera—
cion un equipo desconocido, teniendo situaciones adversas derivadas de lo inflexible de un
aparato gubernamental administrative
- Una tecnologfa nueva en el pafs, fue puesta a
prueba, en las condicicnes reale3 del area rural. Nada se invento y la experiencia fue reji
lizada y controlada con los recursos escasos
con'que cuentan las instituciones gubernamenta
les.
- La experiencia fue rutinaria y rigurosamente
controlada con los elementoa que fue posible
disponer.
- El equipo es funcional y, a juicio del que su.3
cribe este informe, produce buenos resultados
con una operacion sumamente sencilla en contra
posicion corf otros sistemas de desinfeccion re
coinendado3 para el area rural.
6.7.2 ASPECTOS CUANTITATIVOS:
Solamente se analizaran algunos de los a s —
pectos mas significativos, ya que se insiste en
que es necesario desarrollar la experiencia con:
- Mayor tiempo de investigacion.
- Equipo adecuado para analisis,bacteriologicos
y examenes f£sico-quimicos.
*
t
- Resurso humano altamente c a l i f i c a d o , en contr£
l e s de calideddel agua.
"
Entre los aspectos a sefialar caben p r i n c i p a l
roente l o s s i g u i e n t e s :
~"
El MOGGOD, produjo l a cantidad de gases oxi
dantea, n e c e s a r i a en e s t e c a s o , para disminuirW
terminar con los i n d i c a d o r e s b a c t e r i o l o g i c o s que
se^encontraron en e l agua antes de l a realiza—-\
cion de l a e x p e r i e n c i a .
'
,
\
Debe hacerse n o t a r que, como lo muestra el
grafico"No. 13, despues de l a primera toma de
muestra, ya efectuandose el t r a t a m i e n t o e l anally
s i s b a c t e r i o l o g i c o aun indicaba p r e s e n c i a de co~
liformes.
Queda la incognita de saber si se debio a haber
sacado la muestra dos dfas despues de haberse
iniciado el proceso de desinfeccion, se decidio
desinfectar el tanque de almacenamiento y luego
se tomo nuevamente larauostra,la cual indico
ausencia de coliformes.
En eate caso... ? influirfa el hecho de
haberse desinfectado el tanque o serfa que para
hacer el analisis se utilizo reactivos y mate—
riales nuevos ?
La grafica No, 13 indica el^resultado de los di^
ferentes analisis'bacteriologicos practicados.""
La grafica No. 13, debe interpretarse con
la siguiente informacion:
27-10-6*7?
Agua sin ninguna clase de tratamiento, antes de iniciarse la experiencia
12-11-0*7?
Agua analizada despues de dos dias
de iniciado el tratamiento.
19-11-6*7?
Ag\ia analizada despues de nueve dfas
de tratamiento y luego de haberse djj
sinfectado el tanque de almacenamien
to.
""
25-11-6*7?
Agua analizada despues de quince
dias de tratamiento.
OBSSRVACIONSS FINALES
5] suscrito quiore H^jar con.jt"icia de :;a roc'ncci:'iionto a las autoridndes de la CPS y do UIH2PAR quo or'-ivioron atontos a prestar el apoyo necesario par? /?1 ''osarro
llo de la exporiencia.
Reconocimiento especial a las autoridades de la Jofnt'jrn
de Area de Salud de Chiquimula y a la Direccion del Centro Universitario del Nbr-Oriente en cuyos laboratories
y con su personal calificado se reali-o el control de la
calidad del agua.
Finalmente al personal de la Region Oriental que dodico
lo mejor de su esfuerzo para apoyar el desarrollo del proyecto en sus diversas fases y sobre todo en la prepare:on
del presente informe y el documental audiovisual correspnn
diente.
Ing. Jose Ollbortc ^cn-aler.
Jefe Region Oriental
UHEPAR
JASCH
DIV1:JIL.
.L* .*3.L...U.:-r.L'.'TC JUL i-JJlO
i:..--\::"j i: J..L -i:... ^-I : AO:J ::naca::uc
ion ^L i^Tcx J.J i:..i-_;.._^..';.j J^ :-.-iLr.i:-.jic;;
•i-'O.
CO/07.
A^^i ^uj/imiOLcaioo
Muostra dc.
FUEPLO IJUEVC UZUN:-TI».)T {ZCM'.
27-10-27.
Fecha en que fue captada la inuestra:.
15*20
Hora en que fue ce.ptada la muestra:_
Sitio:
Fuente:
J.
Urn r-!-.'.
S e r v i c i o , Do o i c i l j f r i p , ._
S e r y i c j o Doinici 1 j p r j o .
P e r s o n a que c a p t o l a m u e s t r a :
c g c R CHACTITI !Vt;cs ( 'vrai'.M'JL
F e c h a en que d i o p r i n c i p i o e l examen:, , ,
27-ipr87.
CAJIACTEHES GENERALES:
Colors
,
Incoloro
S u s t a n c i a en s u s p e n s i o n :
I n v e s t i g a c i o n d e l Grupo
_Aspecto:
£1- IP.
_____
Coliforme
Incubacion a 35 C
No. Membrana
Medio
Filtrantes Selectivo
2
KtTDO
Volumen
Colonia
Coliformes
Tiempo
Muestra
Coliforme
p/100 ml
Inob.
25
216
5, 400
?.\ nr..
O b s e r v a c i o n e s v F o r F R o s o n t - r Munisro <.lQ.Co1.oni s J e l . '. ; r" <o ^ - . t f r r H . e
C o n c l u s i o n e s : " - - - ^ » ° E > " i ' " £ * " - ^ CO?T.T.VC HIT : . - O .
Fecha:
^c
ifJJZc
-••>i3 3
C.
JASCH
DIVLliJjLC..". :),J .V^.'JLi-I.T.'iX. '.)Jij LIDIG
J.C.A J_;L
i.-j'^C-'X J.j i"..J-"-i---.Ao Di-I ..•'J.LJ.'-L.JXCJ.
n
A^i=-=iLi
£
o..85/az^.
LiAj'i^lIGLOCrlCO:
Huestrn. do^fejBgLQJIIIBg-O'UZPMATifllf ZACAPA«
Fecha en que 'fue c a p t a d a l a m u e s t r a : 11,9^.11 -Q7*
Hora en cue fue c a n t a d a l a m u e s t r a : , , t l t ^ Hrs BMf
Sitio s
Pueblo Nuevo ..
___
Fuente:
Coneccfon D o m i c l l i a r i a : fcuSEBIO JAOINIO)
Persona cue c a p t o l a muestra:. .OSCAR CjiAGllfN .RAMOS. TOBPAR*
Fecha en cue dio p r i n c i p i o e l examen?, 119-11TQ?» , —
CARACTERES GENERALES:
Color:
Incoloro
Aspecto:_
S u s t a n c i a en s u s p e n s i o n : _ ^ _
_
I n v e s t i g a c i o n d e l Grupo Coliforme
Incubacion a 35 C
No. Membrana
Medio
Filtrantes Selectivo
%0
Claro
Volumen
Muestra
Colonia
Coliforme
Coliformes
p/100 ml
25
0
0
Tiempo
Inob.
2^ Hr:
V /
Observacionesf/ Ppr Np P r e s e n t a r Mi»g«»Jg& t oge--d«-co3on1afl d e l Grupo
C o n n i u s i o n L : ^ 0 ^ f o r e m TptQal «»EL AGtf£ S i FS: APTA PARA EL COHSlMO HUMAN0Fecha:'_ >
,/' : Nombre:, • v /fl?aAw
m
Ill
/fdjJ*
l/oJ'^h^
, MARIA ADELA VALDES C .
C •
JASCH
Dl-/"_.'JiL". .X.j O,L!..U .M.'l'.'Tt
C .1 •„•£• ; ..j'j.'C'X- .-'•-< 1...J-..;
I..AJIC
J.JL
».J D J .•.'lLa.-L-.'Jj.C;
82/87.
*'Q«, , 7 7 ;,, " --
Muostra dc: PU£BLQ MUEVO, (UZUMATLAN) ZACAPA.
Fecha en que fue captada la muestra: . 12-11-37?
Hora en cue fue captada la muestra?
iQfP^H? 5 *
w
Pueblo uevo
Sitio:
„
Fuente:
,
3 e r v l c i o DomicJ-llario CflUJJSVIO JACINTO),
P e r s o n a oue capto l a muestra? , OgCAfl,CHAgJVN. HAMQS UNKPARj..
Fecha en que d i o p r i n c l p i o e l examen? r . 12-11787»
., ,
CAHACTERES GENERALES:
Cairo
Incoloro
_Aspecto!
ColorJ_„_
Sustancla en suspension: _ _ _ Pequefia.3 P a r t i c u l a s .
Investigacion del Grupo Coliforme
Incubacion a 35 C
No, Membrana
Medio
Filtrantes Selectlvo
ENDO
2
Volumen
Muestra
Colonia
Coliforme
25
68
Coliformes
p/100 ml
Tiempo
I nob.
24- Hrs,
1,700
0b se r v a c i o r i e s : Por Presentar "umero de Colonlas d e l Grupo.Coliforme Total
Pn»,o,i<Ck**' 2J2D.AGUA NO ES APTA PARA,_JL CONSUMO HUMANO.
^onCjJJ.bxpnes;^.—„
J^%/L_
yfifi^y' • •
13-11-82,
_
~
y
..^mhTetS^^^^rJ^.^vJ^J
JEFATURA j-fcHIA ADBLA VALDEa C .
suramsc-R K
JEFATUU AI
a-JIQUIA'.U?-A, Gr
f*~j~7~
DE
- ' •
T
CS
.1
I.'.
Mr
"
-• C y
:.•<*$
A,'
f l N S / W O
SOBRBl
D E G R A D A C E O N
OHITEROKNTES
PO.R
K M P L E O
J3JE
L,A
AIM I O N I
D1S
O-OS
O Z O N O C L O R AG E ON
Dr Omar J .
Simoni
BUENOS AIRES, ARGENTINA, Noviembre 1987
V
E N S A Y Q
3 Q 3 R E
P E O R A D A O X OIM
DKTKROENTECS
AIM T O N I C O S
POR
E M P L E O
DE
LA
D E
O Z O N O O L O R A O I O N
Dr. OMAR J. SiMOIMI
D i r e c t o r del Fstudio Consultor en Contarninaeion Ambiental - EFJCA - Maturin 2887,
Buenos A i r e s , A r g e n t i n a
Asesor Tecnico de la Federacion A r g e n t i n a de Aguas Cjaseosas y Bebidas sin Alcohol
D i r e c t o r Tecnico de CIMES - C o n t r o l I n t e g r a l Metodologico de Sodas
lNTRODUCCION
Se verifico la propiedad del ozonoclorador marca GIDOX en la elimina
cion de detergentes anionicos, evaluados cuantitativamente como
sustanoias reactivas ai azul de ortotoluidina.
TECNICA DE EVALUACION
Se prepararon soluciones de detergentes tipo en concentraciones
crecientes, de acuerdo a las normas IRAN - Instituto Racionalizador
Argentino de Materiales -.
Se procedio al llenado con agua ozonoclorada con una concentracion
de 10.2 mg/1 de oxidante.
Se realizaron luego los ensayos quimicos para verificar los valores
residuales en.las soluciones tipo al cabo de 24 y 48 horas. Tabla
C0NCLUS10NES
Se constato l\a alta eficacia destructiva de la ozonocloracion sobre
las cadenas hidrocarbonadas de un tensioactivo anionico lineal.
Los estudios fueuros deberan encaminarse a evaluar tiempos de accion
concentraciones menores, dispositivos de aplicacion continua, etc.
TABLA I - Concentraciones de detergentes anionicos
en aguas crudas y tratadas con GIDQX
Cone. en detergentes (mg/L)
fluestra N Q
1
2
600
300
A las 24 horas
8
4
1
A las 48 horas
8
3.2
1
Tnicial (cruda)
3
30
j mmv+ ii. - » ^ % n — — — — — w x *
Ozonocloracion
coit produce ion
in-siiu
UNANUEVATECNICA
DE INTERESANTES
POSIBILIDADES
La provisi6n de agua potable
y mas espeefficamente la entrega
al usuario de agua segura desde
el punto de vista microbi6logico
es tin problema que, lejos de estar solucionado, preocupa tanto
a los organismos de provisi6n de
agua como a las autoridades de la
•salud publica.
Segun la Organizaci6n Mundial
de la Salud, 4 de cada 5 camas en
todos los hospitales del mundo
estan ocupadas por enfermos relacionados directa o indirectamente con la mala calidad del
agua de bebida y/o inadecuada
disposici6n de excretas, tornandose este problema mucho mis
y numerosas agencies de ayuda
internacional han volcado no poaflictivo en las areas rurales y en
cos esfuerzos en conseguir tin sisla periferia de las grandes ciudatema lo suficientemente confiades del Tercer Mundo.
ble y que hiciera (rente a los inLa causa, estudiada y reconoconvenientes anotados.
cida, yace en la falta de equipos
En America, la OPS, a travel
y m^todos de desin(ecci6n que
de un programa de Tecnologfa
sean sencillos, durables, confiaApropiadaorientada desde su Ofibles, de facil operaci6n y bajo
cina Central en Washington y conmantenimiento, que sean econ6tando con el apoyo del Programa
micos y que se indepjendicen del
de Naciones Unidas para el Desaproblema de compra\en lugares
rrollo (PNUD) ha investigado un
alejados (incluida eh casos la imgran numero de alternativas tecportaci6n), transporte y almacen6logicas aplicables a la desinfecnamiento de sustaricias qufmicas
cl6n
tales como hipocloraci6n,
utilizadas en la desinfecci6n.
ozoni;aci6n,
yoduraci6n, radiaTornado a nivel mundial, la
cion
UV,
asf
como la cloraci6n
OMS, UNICEF, el CEPIS, el IRC
20 A G U A
por gases, elbraminas, resinas.ha,logenadas, di6xido de cloro, etc.
Hoy y gracias a este apoyo e
iniciativa, parece haberse encon*
trado un sistema con las mejores,
posibilldades yque responde a las
mayores expectativas: la ozonot
cloraci6n con producci6n de gases in-situ.
Sabido es que la ozonlzac(6rt
es una tScnica de excelentes prdpiedades desinfectantes y que el
uso del cloro aporta el residual
indispensable para hacer (rente a
eventuales contamlnaciones ocurridas entre el momento del tratamiento y el del uso del agua.
GIDOX, un exponente da esta
desinfeccion
t^cnica, es un sistema que, en base a agua, aire, electricidad y sal
comun (sustancia disponible en
cualquier lugar por alejado que
est£), produce una mezcla de gases oxidsnles cuyos principales
componentes son ozono, per6xido de hidr6geno, cloro y di*6xido
de cloro.
M£s en detalle, GIDOX es una
celda de tipo electrolftico, dividida en dos semiceldas, que descompone !a sal y el agua por el
pasaje de electricidad de bajo voltaje comandada por un m6dulo
de control electr6nico que acompana al equipo.
El proceso electroh'tico produ-
Reproducido
de
ANOXIII-EDICION5Q
MAYO DE 1987
ISSN 0325 - 6235
Es una publicacion de:
Producciones S.R.L.
Emilio Mitre 130
1424 Buenos Aires
Tel.: 432-5273
Republics Argentina
Registro Nacional
de la Propiedad
Intelectual
N ° 35844
Directoi: ,
Horacio J. Bacot
ce en una semicelda dos subproductos que se descartan: hidr6xido de sodio e hidrogeno; mientras
que en la segunda semicelda se
genera la mezcla oxidante la cual,
conducida a traves de una apropiada conexi6n, es introducida
en el circuito del agua a tratar.
La instalaci6n es sencilla: junto con el equipo se proveo un venturi que absorbe los gases producidos en la celda y los inyecta en
el torrente de agua. Este venturi
debe colocarse en la canen'a "principal o en una derivaci6n. La operaci6n s6lo requiere del agregado
de sal y agua a la celda cuando
sea necesario y la diluci6n del hidr6xido de sodio que se va produciendo a medida que transcurre
el proceso.
La tasa de generaci6n de gas es
comandada por la electrolisis, la
que a su vez es controlada variando la corriente el^ctrica que circula mediante el manejo de un
dial en el m6dulo de control.
(Este m6dulo permite tambten la
incorporaci6n de un buzzer para
avisar a distancia si la celda carece de agua y, mediante conexi6n
a un caudalfmetro, la producci6n
da gas segiin demanda de caudal.)
La desinfecci6n 6ptima y por
lo tanto la dosis ideal se consigue
variando la producci6n de gases
de forma de obtener en el lugar
en que se desee el residual de cloro pretendido, lo que se verifies
con el sencillo analisis de la ortoTolidina.
Debido a que los gases oxidantes producidos en una unidad
N
GIDOX se componen aproximadamente de un 7G% de especies
deloxi'genoy un 30% de especies
del\cloro, se puede esperar obtener los mismos subproductos da
desinfecci6n que se obtienen
cuando estos desinfectantes se
utilizan por separado. Adem^s, el
ozono y los radicales libres del
oxi'geno reaccionarian con mayor
focllldad ante sustancias org^nicas
qua el cloro, dando corno resultarfo un nlvel slgniflcativamente
monor de trlhalometanos que el
que te obtendrfa usando r6lo el
cloro. De manera similar, el oxfg«no puede reaccionar con mayor
fccllldad que el cloro ante los fenoles y las algas debido a su afinlded por la materia orgaViica, reduclendo con ello los problemas
d * $abor y de olor, asf como la
formaci6ndecompuestos organoclorados no deseados. Segun la
Organizaci6n Panamericana de la
S«lud(1) "Desde el punto de vista desalud publica, GIDOX deberfa resultar, por lo menos, tan berwflcloso y seguro como el cloro".
Por afiadidura a la soluc!6n de
problemas de contaminaci6n microblana, GIDOX tamblSn presenta la poslbilldad de destruir susUnclss oxidables tanto organlcas
como Inorg^nicaspresentes en dewgGes cloacales e industriales,
con un ventajoso comportamiento frente al cloro, tal como se desprende de experiencias verificadaj en tratarnientos paralelos
GIDOX-cloro gasy que se presenIan condensadas en los gr^flcos
odjuntos.
El rango de apllcaci6n varfa
detde el ufo familiar al tratamiento de agua de plantas potabilizadoras de hasta 10.000 habitantes
por unidad, a lo que habrS que
eumar afluentes y efluentes Industriales, cloacales y piscinas de natacl6n. El equipo GIDOX es producldo en Argentina por FENAR
S.A.
(1): Mo|ns de Divulgacl6n Te"cnica OPS/CEPIS - N ° 32 - 1986
H O T A : Flguras de este artfeulo en la
p^glna slgulente.
Trrijsjo preparado por:
Injj. Sanit. Felipe Solsona
FENAR S.A.
Pcywndu 2361
Ducno* Aires
Por su gran rendimiento y bajo costo, este equipo es ideal para la
desinfecci6n de aguas de uso dom6stico tales como las de viviendas
familiares, edificios de departamentos, countries, hospitales,
escuelas, piscinas, etc.
Debido a que este sistema produce ozono y cloro simultaneamente,
se reducen los inconvenientes detectados cuando el cloro es el unico
desinfectante, ya que el ozono, con su mayor poder, destruye la
materia organica y los amoniacales presentes en el agua cruda, evitando la formacion de cioraminas que otorgan sabor desagradable
al agua y de trihalometanos, de probada acci6n cancerigena; permitiendo sin embargo la permanencia del cloro en el agua como prevencion a futuras contaminaciones.
La producci6n de este equipo, estimada en 100 gramos de oxidante
por dia permite la desinfeccidn de hasta 100 m3 diarios (100 000
litros/dia), lo que da posibilidad de desinfectar TODA el agua de
consumo, que incluye la de preparaci6n de alimentos, higiene personal, lavado de ropa, limpieza de ambientes, etc.
Este equipo se presenta en dos versiones:
GID0X -2A
consiste en un generador de gases con su correspondiente inyector y modulo de comando.
G1U0X -2B
idem al anterior pero con una bomba de recircula\
\cion incorporada.
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Para \a seleccifin c o r r e c t a de un equipo GIDDX -2 se deben c o n o c e r
Ires datos f u n d a m e n t a l s :
1. Dosis de gases d e s i n f e c t a n t e s a a g r e g a r
2. Volumen de agua a t r a t a r
3. riempo que debe o p e r a r el equipo
5i bien h n b r i a que e f e c t u a r un analisis qulmico p a r a c o n o c e r c o n exacfcitud cual es
la c a r y a de cnntaminacion de un agua ( c a r g a o r g a n i c a o demanda), se puede suponer
que para un agua c l a r a prov/eniente de una p e r f o r a t i o n o de un d e p 6 s i t o limpio, la
DOSIS de d e s i n f e c t a n t e a a g r e g a r a un agua c r u d a es del o r d e n de 1 mg de o x i d a n t e /
l i t r o de agua ( e q u i v a l s a 1 gramo de d e s i n f e c t a n t e / m 3 de agua).
G i r o d a t o irnportante a c o n o c e r es el volumen de agua a t r a t a r por dia. Esto es el
volumen de TODA el agua que se usara en el e d i f i c i o , e s t a b j e c i m i e n t o , e t c .
Con estos dos d a t o s se puede o b t e n e r la c a n t i d a d de d e s i n f e c t a n t e n e c e s a r i o ya
que:
D031S x VOLUMEN DE AGUA DiARIU = GRAMOS DE DESINFEC. NECESARIO POR DIA
Conociendo la c a p a c i d a d de p r o d u c c i o n del G1DOX -2 en gramos de o x i d a n t e / d i a que es
igual a 100 gramos/dia 6 100 g/24 Moras, se puede c a l c u l a r el tiempo mecesario que
el equipo debera f u n c i o n a r para p r o d u c i r t a l c a n t i d a d :
GRAMOS DESINF. POR DIA x 0,?A h/g - MORAS DE FUNCIONAMiENTO DEL EQUIPO
Si el agua a t r a t a r c i r c u l a por el i n y e c t o r un tiempo IGUAL o MAYOR que el tiempo
establecido en el c a l c u l o a n t e r i o r , se debera usar el GIDOX -2A.
En caso de que el agua c i r c u l e un tiempo MENOR que e l e s t a b l e c i d o por el c a l c u l o , se
debera usar el GIDOX -2B.
Este ultimo equipo viene p r o v i s t o de una pequena bomba i n d e p e n d i e n t e que p e r m i t e el
funcionamiento de aquel aun cuando se haya d e t e n i d o la bomba p r i n c i p a l que impulsa e l
agua al tanque o a l sistema de d i s t r i b u c i 6 n .
El tiempo e x t r a que d e b e r a f u n c i o n a r el equipo se r e g u l a f a c i l m e n t e por medio de
un temporizador i n c o r p o r a d o en el modulo de cornando. Al termino de ese tiempo e x t r a ,
el modulo d e t i e n e a u t o m a t i c a m e n t e t a n t o el f u n c i o n a m i e n t o de la bomba a u x i l i a r como
el del equipo.
EJEMPLO:
Supongamos que se deba t r a t a r un tanque de agua de un e d i f i c i o de d e p a r t a m e n t o s de
10 m \ el cual t i e n e una bomba que lo llena en 2 h o r a s . El t a n q u e es llenado 2 veces
por dia.
VOLUMEN DE AGUA D1ARIO A TRATAR= 10 m3 x 2 = 20 m3
DOSIS
\
= 1 g desinfectante/m3
GRAMOS DESINFEC. NECESARUDS POR DIA = 20 m3 x 1 g/m 3 - 20 gramos
HORAS FUNCIONAMIENTO BOMBA PRINCIPAL = 2 h o r a s x 2 v e c e s / d i a = 4 h o r a s / d i a
HORAS FUNCIONAMIENTO DEL EQUIPO = 20 g x G,?U h s / g = *.,8 h o r a s
Dado que el v a l o r n e c e s a r i o de tiempo de f u n c i o n a m i e n t o del GIDOX-2 supera al tiempo
de funcionamiento de la bomba^se debe usar e n t o n c e s e l GIDOX - 2B.
F E N A R
S. A.
_
-
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**TNP^
C R I T E R I O
R/XR/X
S E L E C C I O N A R
E Q U I P O S
G 1 D O X
1F>/\Fi/\
N A T A T O R I O S
Para la seleccion de los equipos G1DDX a ser usados en n a t a t o r i o s se deben t e n e r en c u e n t a
f a c t o r e s tales como: 1) volurnen de ia piscina, 2) t i p o de agua, carga de bafiistas, exposici6n
a rayos del sol y polvo o t i e r r a y 3) horas de r e c i r c u l a c i o n del equipo f i l t r a n t e .
En el punto 2) se toman t r e s tipos de n a t a t o r i o s , cada uno con una c a n t i d a d de o x i d a n t e a
dosificar segun e l s i g u i e n t e c r i t e r i o .
Dosis = 1 g/m 3 de o x i d a n t e :
Dosis = 2 g/m 3 de o x i d a n t e :
Dosis = 5 g/m 3 de o x i d a n t e :
N a t a r i o s con agua en buen estado y buen sistema de f i l t r a c i 6 n .
Con poca c a r g a de baftistas, poca exposici6n a polvo o t i e r r a
y con p a r t e del dia b a j o sombra.
N a t a t o r i o s con c a r a c t e r i s t i c a s intermedias
N a t a t o r i o s con a l t a c a r g a de bafiistas, exposici6n a polvo o
t i e r r a y t o d o el dia b a j o s o l .
Volurnen n a t a t o r i o = 25 m3
HORAS DE RECIRCULACION
U
1
en
tn
o
Q
8
12
2U
G-5
G-2
G-2
G-2
2
G-10
G-5
G-2
G-2
5
G-30
G-10
G-10
G-5
8
12
2U
1
G-10
G-5
G-2
G-2
2
G-15
G-10
G-5
5
2xG-30
G-30
G-15
5
G-5
G-2
G-30
G-10
R-S
G-30
G-15
2
ZxG-30
G-10
5
4xG-30 2xG-30
Volurnen = 500 m3
X
«
2xG-30
G-30
G-10
2
G-30
5
FENAR
G-10'
G-2
G-10
4xG-30 2xG-30
2*.
G-30
G-30
ftxG-30
12
1
A
2
D
C?
8
12
2xG-30
Q.
U
Volurnen = 200 m3
1
O
Volurnen = 100 m3
U
8
Ct
CD
Volurnen = 50 m 3
U
X
a'
\
S. A .
ESTOMBA 1949
Admlnlstracidn y Veritas: PAYSANDU 2361
U
1
T e c n o l o g i a
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8
AxG-30 2xG-30
12
24
G-30
G-15
AxG-30 2xG-30
G-30
3xG-30
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GIDOX
EIM
I_,/\
I N D U S T R I A
Uno de los graves problemas que enfrenta la Humanidad en la actualidad es la contaminaci6n del medio ambiente.
En particular, la contaminaci6n de las aguas es un hecho que preocupa
a las autoridades de los paises por su magnitud y el origen de sus
causas. Entre estas ultimas pueden citarse:
= Falta de legislaci6n apropiada y dificultad en la aplicaci6n
de la misma.
= Desconocimiento y/o desinteres en aportar medidas de solucion por parte de los industriales.
= Falta de equipos o sistemas econ6micos, de bajo costo de
operacidn y mantenimiento y sencillez de funcionamiento compatibles con los costos industriales.
Sin pretender ser la soluci6n total de cualquier problema de efluentes, el sistema GIDOX aporta una notable sencillez de uso a la vez
que una excelente capacidad de tratamiento en todo desague industrial
que requiera una oxidaci6n energica y que este compuesto por cianuros, fenoles, amoniacales, organicos en general, detergentes, herbicidas, plaguicidas, inorganicos oxidables, materiales pat6genos,
etc.
Por sus bondades y costos tanto de adquisici6n como de operaci6n,
GIDOX es el mas adecuado para su uso en toda industria con efluentes
liquidos de alto riesgo.
\
F E N A R
S. A .
-
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G 1 D D X
A
V
E1L
/ \ G U / \
P O T A B l .
e7^
Segun la Grgani/aci6n Mundial de la Salud, en la actualidad 0 de cada 10 camns on
tndos Ios bospitales del inundo estan ocupadas por enfermos relacionados directa a
indirectamonte con el agua que consumers
IMuestro pais no es una excepcion, y en la moyoria de Jas areas rurales, la principal
causa do mnrbi-mortalidad infantil es la diarrea y las infecciones gastrointestinales
de oriyen hidrico.
I7xist.cn leyus y normas que precisan la necesidad de la desinfecci6n de las aguas que
se enlregan a la poblacion, pero ellas no se cumplen debido principalmente a una serie
de faclores entre los que figuran:
= Falta de conocimiento de los niveles de decision pulitica de la magnitud
totalidad y complejidad del problema.
- Falla en reconocer el riesgo sanitario por parte de la poblacitin.
= Falta de equipos de desinfeccion en plantas potabilizadoras que cumplan con:
Costo reducido de inversion
Dosto reducido de operacion
Sencillez de operacion y mantenimiento
Independencia de la compra, traslado y almacenamiento de peligrosas
sustancias quimicas
FFMAR 5A. una empresa argentina cuyos profesionales, consul tores de organizaciones
de salud internacionales que conocen el problema y In han estudiado tanto en sus causas
coino en sus soluciones, presenta la linea G1D0.X, equipos de ozono-cloracion con produccion de gases in-situ, que cumple con la totalidad de los requisitos de un equipo de
desinfeccion ideal y que son los anotados precedentemente.
Porque G1DOX es algo mas que un equipo de desinfeccion.
Fs un sistema que garantiza la caliriad del agua que se entreya a la poblacion no solo
por las sust.ancios alt.amente desinfectantes que genera, sino pur la suma de virtudes
que hacen a la operacion y manejo del equipo v en forma especial al heeho de no requerir del auxilio de compuestos quimicos costosos y peligrosos de manejar. Tan solo electri
cidad, aqua y sal comun.
Es por ello que la Organizaeion Panamericana de la Salud ba expresado publicamente
su apoyo a este sistema, y es su esperanza que aquellos que tienen poder de decision
en la adquisicion y/o uso de estos equipos oigan el llamado y coadyuven para solucionar
uno de los grandes problemas de la Humanidad. que no por antiguo deja de ser menos
angustiante y grave.
F E N A R
S.
A.
T e c n o l o g i a
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M O D U L Q S
*££**
DIE
C D N A N D O
Los modules de comando de los equipos GIDOX para ozonocloraclon
de aguas, tienen por obJGto controlar la c o r r i e n t e que circula
por las celdas e l e c t r o l i t i c a s , gobernando asl la producci6n de
las mismas.
Los distintos tipos de modelos disponibles, permiten tambien
el acceso a una serie de funciones auxiliares.
Los equipos standard van alimentados con tensi6n de red, corrlen
te alterna, de 220 V 6 110 V segun pedido, pudiendo suminlstrarse
mOdulos especiales que funcionen con o t r o tipo de alimentaci6n.
El MODULO C-1 es una fuente de alimentaci6n con
dos valores fijos de corriente (100 % y 50 %), que
corresponden a la producci6n maxima nominal del
equipo v a su mitad.
Estos modulos son aptos para instalaciones donde
no se requiera un ajuste exacto de la producci6n,
pudiendo regularse la dosificacion ya sea controlando
el tiempo de funcionamiento del equipo, o bien el
caudal de agua. Tambien sirve para el caso en que
esten operando en paralelo mas de un equipo, donde
algunos son de valor f i j o (usan el modulo C-1) y
otros son de ajuste (usan modulo C-2 6 C-3).
C-1
GIDOX
•
•
o*
•
9
it *(*?-•-«, -*-_
El MODULO C-2 permite el control continuo
de la corriente, pudiendo de esa forma
ajustarse la dosificacion desde cero
hasta el valor maximo nominal.
Debido al tipo de sistema de control,
este es muy apto para instalaoiones en
las que las variaciones de tensi6n de
linea sean muy amplias.
C 2
GIDOX
9
El MODULO C-3, que tambien controla desde el cero al
100 %, es un acabado sisterna de control electrfinico,
ID que le confiere una gran solidez mecanica y larga
vida util. Tiene un display a leds, lo que permite
una rapiria \/isualizaci6n del estado del equipo.
Con el objeto de acelerar la entrada en regimen
inicial, cuenta con un subsistema de sobrealimentaci6n
electrica. Informa la f a l t a de nivel de agua en la
celda tanto visual (luz) como con alarma sunica buzzer- (opcional). Asimismo posee un sistema realimentado que estabiliza la corriente al valor deseado
f r e n t e a variaciones de parametros externos. Admite
variaciones de tensifin de linea de liasta el 20 %
y cuenta con la posibilidad de dosificar segun demanda de caudal (opcional).
FENAR
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S3
en
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*£sr**
:ELECCION
SEGUN
IPARA
PE
EQUIPQS
CAUDAL,
AGUA
A
TRAT7AR
POTABLE
HAST A
CAUDAL,
3
C m /Y\ ^
FENAR
GLDOK
MODEJL.O
4
G- 2
8
G - S
i e>
G- 1O
23
G- 1.5
4 5
G - 3 0
S. A .
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Il\J5T/M_/\c:iOf\)
^ " N P ^
H I D R A U L I C A
INYECTOR
FLUJD PRINCIPAL _
D E L
D I 5 E N O
t
G I D O X
NYECTOR
B A S I C O
Es la i n s t a l a c i o n basica y es ideal
para t u b e r i a s de bajo diametro y
donde no c i r c u l e demasiado c a u d a l .
V/A'LVULA DE REGULAC1GIM
INYECTOR
MODULO DE CONTROL
£
FLUJG PRINCIPAL
W&2 VALVULA REDUCrORA
Este esquema es ideal cuando no
se der.ee una p e r d i d a de c a r g a muy
grande y cuando la t u b e r i a p r i n c i p a l
sea de diametro pequeno
Esta c o n f i g u r a c i 6 n puede usarse
cuando la t u b e r i a p r i n c i p a l es de
diametro g r a n d e . La deriv/aci6n se
debe armar a l r e d e d o r de una v o l v u l a
e x i s t e n t e y en caso de que no la
hubiere, se debera i n t e r c a l a r una.
BOMBA AUXIL1AR
BOMBA
El uso de una bomba a u x i l i a r p e r m i t e
independizarse del sistema evn donde
se i n y e c t a , y t i e n e la v e n t a j a de
p o s i b i l i t a r t a n t o la r e i n y e c c i o n de
agua con los gases en la misma\tuberia
como en un tanque o c a n a l . _ \
F E N A R
S.
A.
Esta configuracion es excelente cuando
se tiene facil acceso a una bomba
impulsora instalada en el sistema.
T e c n o l o g i a
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AIRES
ARGENTINA
.deeinfeccion.
MODIFICACION POR ACCION DEL GIDOX
APUCADO A UN EFLUENTE INDUSTRIAL CONTAMINADO
8000
1.0
a@
0.6
400
0.0
A
300
Q
160
4
A
300
200
100
o—__
(poi)
>
0.1
\D
\ZJ
I .
A
B
0
V
-
/
o
•
600
A
—X
B
A
40
30
20
o
0
•
1
8
O
760
\
260
A =
:°v
(=)
\\ ^
\
10
0.0
B
400
-o
A
0.2
(Na)
0
2
A
400
-
B
A
800
3
o
o
B
0
B =
b
i
, l..
B
Aaua
Crud«
Agu»
tratad*
corj
GIDOX
(V*tor«s «n «ng/|, •xc«pto par* pH)
ANALISIS COMPARATIVO DEL TRATAMIENTO
CON CLORO GAS Y CON "GIDOX"
A UN MISMO EFLUENTE CLOACAL
KG DE
OXIOANT6
POR DIA
28*
MEMOS
ilii»i»'i<f"l.
1
1.16
CLOPO
LIBHE
HESIDUAU
COLI
FECALES
EN 100 ml
«•> s ^ W - i
t°3
20
E
7
^ — 1"F-T?T3
6.1
OXIGENO
DISUELTO
-^T
6.1
I
33%
MENOS
6%
MAS
PH
I
1
87%
MENOS
6%
MEJOH
CLORO GAS
*
24 AGUA
lA~
1
P L A N T A S
C O N P A C T A S
R C R - 1
P O T A B I L I ^ A D O R A S
P C P - 5
La PCP es una linea de equipos maduiares, con capacidades de procfucci6n de hasta
5 mJ de agua potabilizada/hora.
El tratamiento del llquido se produce segun la secuencla tradiciooal de ingreso-dosificaci6n de coagulante-floculaci6n-decantaci6n-filtraci6n-desinfecci6n.
Sin embargo, la modificaci6n de algunos parametros y la adopci6n de nuevos equipos
permiten en las PCP las mejores calidades fisico-qulmicas y bacterlol6gicas en el agua
efluente a la v/ez que un reducido espacio ocupado.
Si se parte de aguas superficiales con elevados tenores de turbieried 1 slstema de
ranoci6n de la misma a p a r t i r del uso de coagulantes comunes y da un decantador
de f l u j o horizontal ascendente con ssdiplacas incorporada3, SB o f e c t u a con altfstma
gficiencia obteniundose un producto limpio y cristalino.
Si el agua en cambio es dura o salina, el equlpo permite la incorporaci6n, siempre
dentro del esquema general, de un ablandador o de un desmineralizador, los que actuando bajo la tecnica del intercambio ionico eliminan la carga salina. El ablandador o
el desmineralizador son optativos.
La f i l t r a c i 6 n , o t r a importante etapa del tratamiento, se realiza en un f i l t r o de grava
y arenas sillceas, pero si el caso lp requiriera, se puede incorporar al mismo una capa
de carbon activado lo que eliminaria tambien cualquier problema de gusto u olor.
La etapa final del tratamiento, la desinfecci6n, se realiza con el euxilio de un equipo
GIDOX, celda productora de ozono y cloro a p a r t i r de agua y sal comun de mesa. Tal
mezcla oxidante garantiza no solo un sabor agradable en el agua, sino y muy especlalmen
te la completa y segura ausencia de germenes patogenos.
Pueden resumirse las caracteristicas de las PCP asegurando qua se t r a t a de los mas
compactos, seguros, simples de operar y mantener, econ6micos y de a l t a performance
sistemas productores de agua potable, ideales para el medio r u r a l , o para grupo de
viviendas, pequeftas poblaciones, escuelas, puestos sanitarios, hospitales, obradores,
clubes, countries, fabricas, y aun como plantas mdviles para casos de c a t a s t r o f e , inunda
ci6n, etc.
FEfMAR
S. A.
-
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* • $ * * *
C A R A C T E R 1 S
T I C A S
D E
C O I M S T I T U I l V a S
L O S
D E
E L E M E I M I
L/^XS
O S
P C P
DOSIPICADOR UE CUAGULANIE !li! train tlnm depftnfto da poitettleiKi, con r e g u l a t i o n
jmr volvula I n f e r i o r y rior.irii-_->ciOn n notoipnr Inycnciftrt en la roplreclftn da la Uombe,
lo que f f l c i l l t a l a homoo/jima y p e c f n e t a dwer3l6n del coagulants empleado.
FLOCUI.ADUU. Va occiorv.tmiraif.o lildi-.'mtlcoi i» rmrmlto vnlocidadns docr<?clenl;nD, lo
quo fovorr.Mrn Jo ConiiaciOn 1J1? co'iqii/im Uifl •iioAirj nnrorlndas pots la decantaclon.
El floculndar RSt5 inketjiado ol sintpitvi tta iladnr/docontodur.
DECANIALXIH. Ponoc m m rainara coiiipnurxidbra para distribuciou lominor del Tlujn do
lurjryyo. Cuonfca c n n placas nspr'cialns iiicUKJ.m en un 'mijulo picCljodo porn obteiiRr
por una p a r t e Id mayor to->o du inloi catnlfcn ptir cnnslguiente dc srtfinientocIGn ds
las particular, do ttirhiedad, y por ohra, u a w r i c i o n t o arclOn da eutolltnpiaza, lo qua
f o c l l l t n ;IIJ titlll/nclOn.
F l l l i n i . Do I'tinr/o t'n rltm grout iluini?tr1nn tlfcrnMl.ni: r o n coltint.or p|/mUcrt rfo nltp
inipaclu; esroros riltroittnn roiuir.ida:) do tXmw do posaje, con munftinetro Incoiporodo
y ptii'un do a i m .
AHIANPAPIJN/DESMINEHALMAOUH. Ai:l.i'/,i IjajM'l r r i n e i p i u dnl intc»ir.nmtilo I6I>ICO. con
I esin.-ir; i>:;('i?i:Joi7-n"r;h"rf.<>i.k:.-r: • itit! ptirmltmiB pliinlnaclftn do In col H U sollno. Ento oqulpo
es o p l a t l v o , si nl caso lo ri'qiiirioia.
OEUINrtiCCIUN. l o (losinr»;t:i;lfin i.'sl.i'j prci/i-Jk, pin- lo occiori cle un equlpo 15IDUX: :;l!itnma
unico en r,u ij&nom v aconnnjailo por In Uigrtl/arAOn Mundial de lo fialud. r i u d u c e
oiunu y e l m o a p . i r t i r do .njuo v '.'»"»l comi'mli? «M;-;;I. l o mezclo tie gasoa oxldanfcps
genurada pur pi r?qi;ipn ir.-.ugvrn lo t o t a l <>Vm\wMn\ du bacterleg potOgenns en ol
ogua eTIuente ds la p l a n l a .
IJUMIJA. Dp tipo conlriftujo. horizontal t'n iwul'lock. Segun r«queriinionto SB proves
en'Ye, ?m 0 3(10 Voltr., 50 llz.
EUAOHU 01: VAIVUlAr, V SISIEMA Of INICHtHEXIUN. IudjiS Inn r.nHmlog. nccnnnrloD y
valvular; r.nii do I ' V C G dp Pulipnipiiono y s a r c s e n t a n en cuadios ds nianlobra do
facil vir.uoli/oeion y accionamimitu.
CAiiA(;n:m'.iiii:An CUN:;imH:iIV/AS UPL riufJiAOU'VDEL'ANiAoon. FILIIU) V AHLA^DADOR/
O E S M I N ' I - H A U Z A U U H . LOIS eliMiirntcia iminciiHin* pr.t.'m todos conrBCClo:iado3 en cliopa
tie ticeru ill c.irlnifiti 1D1II/10?!), con c.'ilH'/otattnrlpr.ffnicos con Urldnn elmlottodns
,
y Irotndno con rpnliiiit: upoxi p i e v i o a i - n n o * v ronliitlj.ndo; lo qu» 3r,G<juro una muy
l.ircj.-: v/dn n lnr. plnnUw a lo voz quo una i * / a d n rohuslaz y roalstencln a foa onnntng
internns v i»xl:srnus.
Todo i?l conjunliri ^t» pio:;i;nta inont.aiki r n tirfiinrjo lo quo pomilte su f6cll ublcnclftn
d e f i n l t i u a 6 cl tror.l.ido Din npcesldod i)o dowirnl ft pordlda da tlempo.
CAUDAL
nooccq
PCP-1
PCP-5
1
5
I):M'.:NUIIINI:'.; at
Lajruu A u d i o Allan
1.50
1.UU
0.'.5
11.110
Voclo
1*
IX.
r^corpa
En t r a l i o j o
55
110
Z50
U5
230
950
* c o n cblandodor incluldu
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Aguas
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ARGENTINA
*fer*efr
<
»-
u
<
D.
1
0
j
u<
c
< Ui
c z
•
0 UJ
0 0
<
N
<
M
J
M
I
«
(D Q:
< ID
1- <
0 0
a
<
h
z
<
_i
a
FENAR
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ARGENTINA
^sKT^
P L A N T A
D E P U R A D O R A
MSCKIPCION
Planta depuradora que a traves de un tratamiento integral del liquido
cJoacal. permite obtener un efluente cuyas caracteristicas de alta
limpieza, baja DBO y ausencia de germenes pat6genos, es facilmente
disponible en cualquier curso o terreno.
La planta cuenta con secciones que aunque individuates estan integral s en un todo, haciendo a la misrna facil de operar y mantener a traves de una total automatizaci6n..
ELEHENtOS CONSTJTUYENTES
La planta cuenta con los siguientes elementos de acuerdo al camino
que recorre el liquido a tratar:
- Camara de entrada del liquido cloacal
- Concentrador de s61idos por reja manual o automatics
- Camara de bombeo
- Difusor presurizado
- Sedimentador primario
- Turboeyector
- Primera camara de barros activados
- Canaleta de eliminacidn de espumas y recirculacion
- Segunda camara de barros activados
- Dispersor de coagulante
- Floculador
- Sedimentador secundario
- Filtro
- Desinfecci6n por ozono-cloracion
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VyEEPsiT/^JAS
S Q B R E
EfM
EEL
P E L
L O S
S I S T E M A
FEEiM/O^R
OOF\J\/tE[\]C:iOt\J/^\L.EES
T R A T A M I E N T O
DEE
C L O A C A L E S
"feN**
SISTEMA COIWEIMCIONAL
SISTEMA FENAR
ESPAC10 REQUERIDO
l a s p l a n t a s de t r a t a m i e n t o de e f l u e n t e s convencionales f u e r o n diseft3das t r a t a n d o de l o g r a r
capacidades y espejos de agua i m p o r t a n t e s
para o b t e n e r mejores o x i g e n a c i o n e s y tiempos
de permanencia h a s t a Uegar a la d e g r a d a c i 6 n
bioJ6gica por medio de f l o r a a e r 6 b i c a . Esto
demanda obras c i v i l e s de e n v e r g a d u r a c o n el
c o n s i g u i e n l e gasto de e s p a c i o .
Las obras c i v i l e s r e q u e r i d a s p o r n u e s t r o
sistema de d e p u r a c i 6 n se r e d u c e n a una
p l a t a f o r m a de apoyo p o r los estanques
m e t a l i c o s mas dos camaras de r e c e p c i 6 n
de Ifquidos.
Corno ejemplo: p a r a una p o b l a c i 6 n que c o n
un sistema c o n v e n c i o n a l r e q u i e r a 400 m*.
el sistema FEIMAR solo n e c e s i t a 160 m 2 .
COSTOS
Los c o s t o s de e s t a i n f r a e s t r u c t u r a son realment.e elevados debido a los e s t u d i o s de suelo
p r e v i o s a la c o n s t r u c c i 6 n , e v a c u a c i o n de aguas
s u r g e n t e s donde las h u b i e r e ; basamento p a r a las
misrnas y costos de la o b r a e s t r u c t u r a l .
Los costos de i n f r a e s t r u c t u r a son r e d u c i
dos pues no r e q u i e r e n basamento ni espa
cios i m p o r t a n t e s .
TIEMPO DE EJECUCiGIM DE LA OBRA
Los tiempos de e j e c u c i o n de o b r a son a p r e c i a bles aun para empresas de a l t a c a p a c i d a d
tecnica.
Los tiempos de e j e c u c i f i n de o b r a se
r e d u c e n notablemente pues los estanques
metalicos estan c o n f o n n a d o s p o r paneles
plegados p r e f a b r i c a d o s , los que son de
muy f a c i l montaje en e l l u g a r de la
obra.
COINJSUMO DE EIMERGIA
Elementos e l e c t r o m e c a n i c o s de g r a n peso, c o n s t r u c c i o n e s r u d i m e n t a r i a s c o n g r a n d e s insumos de
energia.
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Los elementos e l e c t r o m e c a n i c o s ( a e r e a d o r e s , c o n c e n t r a d o r e s , motobornbas)
son de reducido tamafto y f a b r i c a d o s c o n
t e c n o l o g i a de p r e c i s i o n , siendo el c o n s u mo de energia e l e c t r i c a r e q u e r i d o ,
un t e r c i o de los sistemas c o n v e n c i o n a l e s
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EQU I IPOS
BOMBAS
De eje vertical o sumergibles segun el caso. De baja presion, alto
caudal y rotores semiabiertos pf.ra evitar obstrucciones.
DIFUSOR PRESURIZADO
De accion descendente que permite una rapida y efectiva mezcla del
liquido ingresante con los barros activados.
TURBOEYECTORES
De diseflo especial, permiten el desmenuzamiento veloz de los s61idos
organicos para facilitar su degradaci6n, a la vez que incorpora grandes masas de oxigeno al liquido cloacal.
DISPERSOR
A motor con eje vertical y 3 vueltas por minuto. Con dosificaci6n del
floculante por medio de un conducto eje-central.
SEDIMENTADQR
De bajo volumen y alta capacidad debido a la disposici6n de sediplacas
oblicuas.
FILTRO
Abierto de grava y arena; con lavado realizado como en los filtros
rapidos convencionales.
OZONOCLORADOR
Celda GIDOX para dosificacion de gases oxidantes compuestos por ozono
y cloro, lo que permite un ajuste fino del proceso oxidante, a la
vez que asegura la eliminacion completa de los germenes pat6genos.
Hasta 30 m 3 /h se presentan plantas confeccionadas en hierrorplegado,
lo que simplifica la instalaci6n y reduce los costos de inversion
inicial.
Para caudales mayores se confeccionan modulos en H Q A Q y mamposteria.
CONSUMO
SINHIRGETX OO
Hasta 30 m /h aproximadamente 1 HP/m3 t r a t a d o .
3
CZ\TP/\C
1 D/\E>ES
3
Desde 5 m /dia en mas.
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P L A N T A
*«£**
f
.
.
3.
t*.
5.
6.
7.
8.
9.
10.
11.
13.
lb.
15.
16.
17.
18.
19.
20.
f
23.
2i*.
75.
26.
27.
DEE
D E P U R A D O R A
L i q u i D O S
C L O A C A L E S
Camara de e n t r a d a del e f l u e n t g
C o n c e n t r a d o r de solidos
Camara de bombeo
Bombas
D i f u s o r presurizado
Sedimentador p r i m a r i o
Turboeyector
Primera e t a p a de o x i d a c i 6 n
Retorno de solidos flotanUas
Conducto r e t o r n o de Pescadores
Segunda etapa de o x i d a c i u n
Turboeyector
Turboeyector
T e r c e r a e t a p a de o x i d a c i 6 n
Conducto al floculador
Floculador
Camara de f l o c u l a d o
Bomba p a r a solidos sedimentados
Sedimentador secundario
F i l t r o de g r a v a y a r e n a
C o l e c t o r de lodos y c o n t r a l a w a d o
Bomba p a r a lavado del f i l t r o
Ozono-clorador
L a b e r i n t o mezcla d e s i n f e c t a n t e
Camara de ludos
Camara de salida y tomamuestras
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'• •
ft
*
E V A L L J A C I D N
B / \ E : T E R I E : I 0 / \
3 0 B R E
P R A C T I C A
O E
U/\
/\G3LJ/\
OfcEL,
R O P E R
G Z O N O C L n R A C I O M
G A S I F I C A D A
Dr. Omar J. Simoni
Buenos Aires, Argentina, octubre de 1987
t£\//\t-U/\C:iLJr\]
B A C T E R I C I D A
S O R R E
P R A C T ' I C A
PEE
L/\
/M3LJ/X
PEEL
P D D E R
O Z O M O C L O R A G I O N
G A S I F I C A D A
Dr. OMAR J. SIMOMI
- D i r e c t o r del ECCA - Estudio Cnnsultor en Contaminacion Ambiental, M a t u r i n 2887,
Buenos Aires, A r g e n t i n a
- Asesor l e c n i c o de la Federacion A r g e n t i n a de Aguas Gaseosas y Rebidas sin Alcohol.
- D i r e c t o r Tecnico de C1MES - C o n t r o l I n t e g r a l Metodologico de Sodas, A r g e n t i n a
SUMMARY
This work is r e l a t e d t o t h e evaluation o f t h e d i s i n f e c t i n g power o f a GIDQX ozonoc h l o r i n a t i o n c e l l , in a series o f gasified w a t e r b u t t l e s c o n t a i n i n g Feacal Coliform
and Pseudomona Aeruginosa b a c t e r i a c u l t u r e s .
From the f i n a l e v a l u a t i o n i t can be concluded t h a t t h e experience p r o v e d t o be
e f f e c t i v e f o r complete immediate removal o f F.C. and complete P.A. elimination a f t e r
?k hours of t r e a t m e n t , when using water highly c o n t a m i n a t e d .
INi'RQDUCCION
El t r a b a j o consiste en la evaluacion b a c t e r i o l o g i e s para o b t e n e r el poder b a c t e r i c i d a
de la ozonocloraci6n, cuando e s t a se aplica i n - s i t u sobre envases con agua gasificada
-sifones- en lineas de t r a b a j o , actuandn sobre la produccion
riirecta,
previamente
cont.aminada con copas de Coliformes Fecales y de Pseudomonas Aeruginosas; con
mediciones de o x i d a n t e .
Para el estudio se c o n t o con un equipo GIDOX-10 producido por la firma FENAR S.A.
de Argentina y la c o l a b o r a c i o n de la Soderia LA MARINA, Andres A r g i b e l Z86G, Buenos
Aires, que brindo sus i n s t a l a c i o n e s .
r-*.
TECINJICA DE EVALUACION
Se dispuso de 17 env/ases limpios y sa procedifin a su desarme manual, inoculandose
en cada uno de ellos 50 ml dG un c u l t i v o r i c o en Coliformes Fecales v 50 ml d e o t r o
cuitiv/o r i c o en Pseudomona Aeruginosa, preparados segun las teenicas b a c t e r i o l o g i c a s
c o r r i e n t e s de aislamiento de cepas, con p o s t e r i o r eniiquecimiento.
Los env/ases, p e r f e c t a m e n t e individualizados del 1 a l 15 se colocaron en la linea de
t r a b a j o usual, r e t i r a n d o s e los numeros 16 v 17 para s e r v i r como t e s t i g o s .
El agua de llenado de los sifones, fue la u t i l i z a d a en la operacitin d i a r i a y que s u f r e
el t r a t a m i e n t o de pasaje a trav/es de un f i l t r o de arena y o t r o de c a r b o n a c t i v a r i o ; con
el agregado en la ocasion de la prueba de los gases oxidantes producidos por e l
equipo GIDOX; los que f u e r c n i n y e c t a d o s en el e f l u e n t e del ultimo de los f i l t r o s ,
antes de un pequefio tanque pulmon, con tiemp6 de permanencia de 5 minutos. Del
tanque por t u b e r i a de 1V' y l o n g i t u d e 7 metros el agua es conducida a las maquinas
carbonatadora y llenadora.
Los sifones f u e r o n llenados segun la operaci6n normal de t r a b a j o , e f e c t u a n d o s e un
dosaje de c l o r n lihre en el c o n d u c t o mencionado, v e r i f i c a n d o s e en mediciuncs c o n s t a n t s el v a l o r de U mg/1.
Una v/ez en el l a b o r a t o r i o del ECCA se llenaron los env/ases 16 y 17 con agua e s t e r i l
y j u n t o con las muestras de la prueba Fueron analizadas bacteriologicamente por
el rnetndo de la membrana f i l t r a n t e , segun la t e c n i c a del Standard Methods f o r
the
Examination o f Water and Wastewater, 16th Ed.
KESUUADas
Los resultados mostraron ausencia t o t a l de Coliformes Fecales en todas las muestras
y solamente uno de los env/ases acuso una c u e n t a para Pseudomona Aeruginosa (v/er
Tabla 1).
Por esta razon y luego de 24 horas de reposo a t e m p e r a t u r a ambiente, se p r o c e d i 6 a
realizar un nuevo dosaje de c l o r o y se r e p i t i 6 el analisis b a c t e r i o l 6 g i c o de la muestra
M° 11, obteniendose en e s t e segundo analisis los siguientes r e s u l t a d o s :
Cloro residual
Pseud. Aeruginosa
menor que 0.? mg/1
0
t:0i\O.USIQI\JES
Los analisis evaluados permiten v e r i f i c a r -para los ensayos reaiizados- la e f i c i e n c i a
b a c t e r i c i d a del ozonoclorador GIDCIX cuando utilizado en aguas de bebida gasificada.
Buenos A i r e s , A r g e n t i n a , o c t u b r c de 1987.
- \
V ¥
TABLA 1. Resultados de los analisis e f c c t u a d o s
MUESTRA N?
COLIFECALES
(b/IOOml)
PSEU. AERUG.
CLORO RESIDUAL
(b/100ml)
(mn/1)
1
0
0
0.5
2
0
0
0.5
3
0
0
0.5
U
0
0
0.5
5
0
0
0.5
6
0
0
0.5
7
0
0
0.5
8
0
0
0.5
9
0
0
0.7
10
0
0
1.2
11
0
IU
0.6
12
0
0
0.5
13
0
0
0.3
U
0
0
0.5
15
0
0
0.5
16
IncontablGS
IncontablGS
-
17
Incontables
Incontables
_
4
,
MANUAL DE OPERACTONES Y MANimiMIENTO PARA. FJ. MOGGOD
Agost.o d e 1987
*
•
INBICE
Seccion
Pagina
INTRODUCTION
1
ANITXEDENTES - FUNCIONAMIH<JTO DE LA UNI DAD
2
GENERATOR DE DESINFECTANIE
3
I.
II.
III.
COSTADO DEL ANODO
4
COSTADO DEL CATODO
5
LA MEMBRANA
6
5EGURIDAD
MATERIALES NECESARIOS
LISTA DE VERIFICACION PARA
OPERACTONES Y MAFITENIMIENTO
'.
7
8
10
COMO LLEVAR A CABO LA PRUEBA
DEL HIDROMETRO
13
LIMPIEZA MENSUAL
15
PUESTA EN FUNCIONAMIENTO
25
REPARACION DEL GENERATOR DE DESINFECTANTE
29
REPAPACION DE DESPERFECTOS
30
GRAFICA DE LA REPARACION DE DESPERFECTOS
32
CAMBIO DE FUSIBLE EN EL
\
REGULATOR DE POTENCIA
34
REEMPLAZO DE LA MEMBRANA
35
REEMPLAZO DE LAS BARRAS DEL ANODO Y CATODO
37
AI^IACENAMIENTO
41
POSIBLES UTILIZACIONES DEL
EXCEDENTE DE HIDROXIDO DE SODIO
42
INTRODUCTION
El proposito de este manual es ayudarle a operar la unidad MOGGOD (Gases
oxidantes mezclados gcnerados insitus) y mantenerla en buen funcionamiento
por medio de actividades de mantentmiento regulares y reparaciones basicas.
El mantenimiento regular le permitira mantener un nivel de desinfectante
apropiado en su sistema hidrico, para poder alcanzar los mayores beneficios
de salubridad.
Este manual esta basado en la unidad 0X1 de dos libras (un kilogramo), que
en la actualidad es el modelo MOGGOD mas comunmente disponible y
ampliamente utilizado. Hay cuatro tamanos diferentes de las unidades
MOGGOD disponibles. Cada unidad puede desinfectar los sistemas hidricos
que benefician hasta 20.000 personas.
\
1
ANTBCECSEN'T'fcS
FUNCIONAMIEWIO DE LA UNIDAD
El sistema desinfectante de MOGGOD tiene tres componentes principales:
1.
Regulador de potencia - controla la cantidad del flujo de electricidad
a traves del generador de desinfectante.
2.
El generador de desinfectante - produce los gases desinfectantes.
3.
El tubo de Venturi - conecta al generador de desinfectante con la
fuente de agua y crea un vacio que absorbe los gases desinfectantes
hacia la fuente de agua.
«fi&**
Regulador
dfoi de
potenciaN
Generador de
des in fectante
Tubo de Venturi
El sis tenia de ICiGGOD simplemente convierte una solucion saturada de
agua salada en una mezcla de gases desinfectantes poderosos mediante el uso
de la electricidad. El regulador de potencia controla la proporcion
(cantidad) de desinfectante producido, para rnedir con exactitud las
necesidades de desinfectante del sistema hidrico. El tubo de Venturi se
utiliza para inyectar la mezcla de gases desinfectantes en el sistema
hidrico.
Antes de intentar la instalacion u operacion, el usuario debe
familiarizarse con cada uno de los conponentes, particularmente con el
generador de desinfectante.
GENERADQR DE DESINFECTANTE
El generador de desinfectante es una caja de plastico dividida en dos
celdillas, el anodo (rojo) y el catcdo (negro).
Vista superior de un
generador de desinfectante abierto
3
I-
El costado anodico produce los gases desinfectantes. Puede
reconocerse por una tapa grande y el cable rojo conectado a la misma.
a.
Tanto la sal como el agua pasan por el agujero cubierto por la
tapa grande.
b.
La ventanilla de observacion muestra los niveles de sal y de
agua.
c.
Las aberturas de rebose permi.ten la salida de cualquier exceso de
agua salada.
d.
Anodos: barras de metal (titanio) , las cuales atraen a los
oxidantes de desinfeccion (los cuales se convierten en gases) de
la solucion de sal.
Vista exterior - con
la tapa grande remov'
M a'
Vista interior
U
11-
El costado catodico produce gas de hidrogeno y canstico (hidroxido de
sodio) , que son los derivados del proceso. Puede reconocerse por la
tapa pequena y el cable negro conectado a la misma.
a.
El agua penetra por el agujero cubierto por la tapa pequena.
b.
Conector bianco en forma de T para la abertura de hidrogeno
y el exceso caustico del catodo.
c.
•
la parte inferior del conector permite que saiga la
solucion de agua/hidroxido de sodio
•
la parte superior del conector permite que escapen los
gases de hidrogeno.
Catodo:
la lamina de metal (acero inoxidable con agujeros)
atrae al sodio y al hidrogeno de la solucion de
sal.
Vista superior sin
la cubierta
Vista exterior tapa pequena removida
5
III. La membrana*
La membrana es una de las partes mas jjnportantes del generador de
desinfectante. la misma separa a los compartimientos del anodo y del
catcdo.
El proceso funciona de la manera siguiente:
a.
El scdio (de la sal) y el hidrogeno (del agua) pasan por el
costado catodico (-).
b.
El gas de hidrogeno se produce en la celdilla del catodo.
Considerando que el misivto es mas liviano que el aire, escapa
hacia arriba. Se instala un tubo de escape para expulsarlo hacia
afuera.
c.
El cloro no puede pasar a traves de la membrana y permanece en la
celdilla del anodo (+) . Esta mezcla de cloro y oxigeno en forma
de gas es dirigida al sistema de abastecimiento de agua, para su
desinfeccion.
U
K&Pk?
*
La membrana es muy delicada y jamas deberia tocarse a menos que se
linpie con un chorro de agua.
\
SBGURIDAD
Maiitenga esta informacion sobre la seguridad en mente cuando trabaje
con la unidad.
1-
Instale la unidad de MOGGOD en un lugar bien ventilado.
2.
Evite respirar las emanaciones provenientes de la unidad.
3.
No ponga sus manos en el liquido que se encuentra en cualquiera de los
compartimientos del generador de desinfectante. Si algun objetx> se
cayese dentro de un cxsnpartimiento de la unidad, trate de rescatarlo
con una varilla o una iranguera de plastico.
4.
ATENCION: Evite que el liquido de la unidad entre en contacto con sus
ojos o su piel.
5.
Evite que el liquido de la unidad entre en contacto con su ropa — _
producira manchas o agujeros.
6.
NUNCA permita a sus nifios jugar cerca de la unidad.
nirios lejos de la unidad cuando linpie la misma.
Mantenga a los
Si us ted sufre un aocidente, siga los procedimientos que se
especifican mas aba jo.
ENTONCES
SI
Su piel entra en contacto
con el liquido del costado
del catodo
Lave INMEDIATAMENTE el area con
agua.
Cualquier liquido de la
unidad entra en- contacto
con sus ojos
lave los ojos inmediataroente con
mucha agua.
i
7
MlKsI AT J-ZS NECESARIOS
Los siguientes articulos doben estar disponibles para poder llevar a
cabo el manten.tmie.nto.
[ ] 1-
Hidrometro
[ ] 2.
Manguera (para lavar y limpiar) conectada a un suministro de
agua.
[ ] 3.
Tubo de 3/8 de pulgada para trasegar con sifon (tres pies de
largo, o un metro).
[ ] 4.
Llaves de tuerca que son parte del equipo.
•>
1
:•.
• •...•>?.<r.
\.~*\
"~^25™SSSJS 4
1
' "" ^
%ai#-
8
[ ] 5'.
[ J 6.
[ J 7.
Tasa de medir, lxjtolla, o !>a.lde.
Balde de plastico para el liquido del catodo.
Sal. (Utilice sal pura. Esto reducira al minimo los problemas
de operacion y mantemmiento, y vale el aumento del costo. No
use sal de mar.) La coiriumdad debera tener disponible una
provision de sal para un ano —aproximadamente 15 bolsas de 50
libras cada una.
•)
I
I.j'sTA UK VaUFJCAClON PARA OPKRACIONES Y MANTENIMTFIN'rO
Utilice esta lista de verificacion para recordarle las tareas que
usted debe llevar a calx) en forma regular.
Diariamente:
[ J Examine el medidor de amperios todos los dias. Compare la posicion de
la aguja con la linea roja indicada en su regulador de potencia.
(Esto indica el nivel de amperios nocesario para mantener el nivel de
desinfecxante que se desea.) Ajiistelo como sea necesario. (Vea los
procedimientos de prueba de ajustes en la pagina del Manual de
Instalacion y Puesta en Funcionamiento.)
Es posible que usted tenga que ajustar los amperios si se desarrollan
cambios en la calidad del agua sin elaborar (tales como una
inundacion) .
10
[ ] Examine la ventanilla de observacion y asegiirese de que el nive] de
sal alcanza la lino.i indicada. Agregue sal cuando SOT necasirir-[ ] Examine la ventan.il.la de observacion y asegurese de que el nivel de
agua en el costado- anodico se mantiene entire las marcas ijndicada.s.
Agregue agua cuando sea necesario. Evite sobrellenar.
11
I
[ ] Agregue agua al costado catodico, utilizando la tasa de medir
proporcionada.
Semanalmente:
[ ] Bvaiue la dejisidad del liquido del compartimiento del catodo con el
hidrometro. (Veanse las instrucciones en la pagina 13.)
[ ] Complete las verificaciones residuales de los desinfectantes en ej.
sisters hidrico, una vez por semana. (Veanse las instruociones
correspondientes al equipo para la evaluacion del cloro.)
Mensualroente:
[ ] Complete la limpieza mensual. Veanse las instruociones en la pagina
15.
(
VERIFICACION FOR MEDIO DEL HIDi^QMErRO
Usted llevara a cabo la verificacion por medio del hidrometro una vez
por semana, para determinar que el liquido (hidroxido de sodio) en el
costado catcdico posee la densidad apropiada (concentracion), para el
funcionamiento eficaz de la unidad.
El hidrometro es igual al utilizado para verificar la bateria de un
automovil.
Si usted no dispone de un hidrometro, siga los pasos indicados en la
pagina siguiente.
Verificacion por medio del hidrometro
1.
Remueva la tapa negra del costado catcdico.
2.
Introduzca el hidrometro hasta el fondo del compartindento del catodo
y apriete la perilla y sueltela hasta que el liquido llene el
hidrometro. La. parte flotante dentro del hidrometro esta diferenciada
por una zona verde, una blanca y una roja.
3.
El nivel del agua deberia permanecer a 1/4 de pulgada por eix^ima o
sobre la seocion roja del medidor flotante.
13
.. r
ENTONCES
SI
El nivel del agua esta por
debajo de la zona roja, el
liquido es demasiado fuerte
o debe diluirse
Agregar un l i t r o de agua de lluvia
o agua destilada y examinar nuevamente. Repita e s t e procediiniento,
s i es necesario, hasta que el n i vel del agua este por encima del
tope de la zona roja..
El nivel del agua se encuentra a 1/4 de pulgada por
encima de la zona roja
Exanunelo nuevamente en uno o dos
d i a s y agregue agua cuando sea
necesario.
El nivel del agua se mantiene
siempre por encima de la zona
roja
Disminuya la cantidad de agua de
l l u v i a que agrega diariamente a l
cortpartimiento del catodo.
Si no se dispone de un hidroinetro
Si usted no dispone de un hidrometro, ajuste el regulador de potencia
para que indique cinco amperios, y agregue agua dentro del costado catodico
hasta que e l indicador baje a cuatro amperios, y despues p a r e . (Este
procedimiento debera tomar e n t r e t r e s y cinco minutes.)
14
UMPIEZA MENSUAL
Usted debe tener mucho cuidado ciiando ] jnipie el MOGGOD. Evite
respirar las emanaciones. Evite que su piel o ropa entren en contacto con
el liquido de los costados del catodo o del anodo. Repase los
procedimientos de seguridad que aparecen en la pagina 7, antes de llevar a
cabo la limpieza.
PRIMERO, interrurnpa la electricidad:
1.
Apague la unidad.
a.
Haga girar al dial hasta que el indicador muestre debajo del
cero.
Desconecte la electricidad
(desenchufelo)
Desconecte los cables rojo y
negro de la unidad de potencia
lueqo, rieutra 1 ice el gas:
2. Llene el hidroinetro hasta
la mi tad con el liquido
(hidroxido de sodio) del
costado catodico, introduciendolo en el costado
catodico a traves de la
tapa negra pequefia.
3.
16
Agregue el liquido del
punto 2 al costado del
anodo, colocando el
hidrometro a traves del
agujero de la tapa roja.
lueqo, desconecte todos los tubas y los canos:
4.
Desconecte la linea del gas (tubo flexible de 3/8 de pulgada)
17
Desconecte el tiibo de
ventilacion de hidrogeno (CPV de 3/4 de
pulgada) de la parte
superior del conector
bianco en forma de T.
6. Desconecte los tubos de
descarga del hidroxido
de sodio de la parte
inferior del conector
bianco en forma de T.
18
Vacie ambos campartiraientos:
7.
Abra las abrazaderas y remueva las tuercas de oreja y las arandelas.
Reniueva la tapa del generador de desinfectante. Coloque las arandelas
y las tuercas de oreja en un lugar seguro.
19
20
8.
Ahora es necesario remover todo el liquido del MOGGOD.
PR'IMKRO saque con sifon el liquido del costado ancdico (tapa roja) .
Atencion: es posible que se emitan gases durante el procedimiento de
trasegado con sifon. JAMAS intente sacar con sifon utilizando su
boca.
Como trasegar con sifon:
a. Llene el tubo de sifon
con agua. No debera
haber burbujas.
Coloque sus pulgares
sobre cada extreno
del tubo, y aguante
el agua en su lugar.
21
c.
d.
Coloque un extremo del tubo dentro del foixlo del costado anodico
de la unidad, y mantejxja el otro extremo cerrado con su dedo.
Cologne un extremo a un nivcl mas bajo que el MOGGOD para vaciar
los contenidos en un balde o botella de plastico.
Retire su dedo del extrerno de desague para poder drenar el
liquido del cxsipartimiento del anodo.
\
e.
9.
Una vez conpletado el desague, cleve el extremo del tubo
correspondiente al anodo para oscurrir el liquido res tan tc.
Enjuague el tubo con agua.
Luego remueva con sifon el liquido del conpartimiento del catodo y
coloquelo en vn receptaculo de plastico separado. Siga las
indicaciones que se especifican en el paso 8, supra. Guarde dos
litres de este liquido (hidroxido de sodio) para utilizarlos mas tarde
en la puesta en funcionamiento de la unidad. (Puesta en
funcionamiento, paso 3b.) \
23
10.
Cuando ambos compartimientos estan vaci.os, recoja la unidad y llevela
al lugar de limpieza. Enjuague AMBQS compart imientos con agua para
rejrover los sedimentos e impurezas que podrian haberse acumulado en
los compart imiontos.
11.
lave la membrana con agua.
EVTTE TOCAR LA MEMBRANA! No intente limpiarle con un cepillo o
cualquier otro objeto. Solamcnte enjuaguela con agua. LA
MEMBRANA ES MUY FRAGIL.
* Si la calidad de la sal que se utiliza es muy baja, o si se
utiliza un chorro de agua fuerte, la mejnbrana eventualmente
acurculara calcio y iragnesio. Esta acumulacion aparecera en forma
de una capa pesada de color blanco/gris. Entonces, sera
necesario:
a.
empaparla en vinagre introduciendo viriagre en el dostado del
anodo del generador
b.
enjuagarla entonces con agua.
No habra necesidad de remover la membrana del generador para su
liiipieza.
12.
El resto de los liquidos que usted ha vaciado de los cxxnpartimientos
del anodo y del catodo pueden descargarse en la alcantarilla. Si no
existiese dicha alcantarilla, los mismos podran descargarse en un hoyo
pequeno en la superficie. (El hidroxido de sodio proveniente del
costado catodico puede utilizarse como un limpiador de plomerias. Ver
pagina 42 para otros usos.)
13.
Ponga en funcionamiento el M0GGOD siguiendo las instrucciones de la •-'
pagina 25.
\
24
PUESTA EN FUNCIONAMIENTO
No enchufe el cable a la unidad de potencia hasta que llegue al paso
10.
Prepare una solucion de aqua salada saturada en un balde o una
botella: empape las piedrillas de sal con agua de lluvia o agua
destilada hasta que no puedan disolverse mas. Coloque el agua a un
lado. No utilice el agua hasta llegar al paso 4.
Prepare el coitpartiitiiento del catodo:
a.
Llene el oostado del catodo con agua de lluvia (o agua
destilada).
25
Agregue todo el hidroxido de sodio (caustico) que usted guardo
durante el proceso de lirrpieza del costado catodico.
(introduzca fotografia)
Prepare el cximpartimiento del anodo:
a.
Llene el conpartimiento del anodo (tapa roja) con sal, hasta el
nivel indicado en la ventanilla de observacion.
Agregue aqua salada saturada lentamente hasta el nivel de las
tuercas superiores de la ventanilla de obsrevacion. Cuando el
agua cxanienza a gotear por las aberturas de rebose en el cx>stado
del generador de desinfectante, significa que usted ha agregado
suficiente agua.
26
Armg_.DUgyamente la unidad y conecte las tuberias
5.
Asegurese de que las juntas que corren por debajo de la tapa no tienen
tierra o sal. Coloque la tapa en la unidad. Examine las abrasaderas
exteriores para asegurarse de que no haya acumulacion de sal, y
limpielas cuando sea necesario.
Junta
•Abrazadera
6.
Conecte nuevamente l a l i n e a de gas (tubo f l e x i b l e de 3/8 d e . p u l g a d a ) .
27
Conecte nuevamente el tubo de ventilacion del hidrogeno a la parte
superior del conector bianco en forma de T.
Conecte nuevamente el tubo de descarga a la parte inferior del
conector bianco en forma de T.
Conecte nuevamente los cables rojo y negro a la unidad de potencia.
Conecte el regulador de potencia a la fuente de potencia, enchufandolo
en una toma de electricidad.
(intrcduzca la fotografia del campo)
Coloque el dial del regulador de potencia en la marca indicadora roja.
t...._.
28
REPARACTON DEL GENERATOR DE DRSIM^CTANTE
La unidad generadora de desinfectante MOGGOD es rnuy durable y sin
desperfectos, y rara vez necesitara reparaciones. No obstante, es posible
que haya instancias en las cuales el mantenimiento por si solo no es
suficiente para asegurar la operacion correcta del sistema. Las secciones
siguientes le proporcionaran ayuda para llevar a cabo las reparaciones
basicas.
29
•REPARACION DE DESPERFECTOS
Sintomas
Medidas
Si el medidor de anperios en
el regulador de potencia no
indica ningun tipo de
corriente
Primero, asegurese de que no
ha habido un corte de luz
a. si hay electricidad,
entonces examine el fusible
en la parte frontal de la
unidad de potencia, y
reemplacelo si es necesario.
(Ver las instruceiones que
aparecen en la pagina 34.)
b. si el medidor aiin no
registra corriente,
asegurese de que la
unidad de bombeo esta
funcionando y examine el
fusible o los interruptores
de circuito en el suministro de potencia principal.
Si hay un fuerte olor a gas
de cloro en la habitacion o
recinto protector.
Si no hay residuos de cloro en
el suministro de agua (despues
de haber pasado por el tubo de
Venturi).
Dirijase a la grafica que
aparece en la pagina 32, para
procedimiento de reparacion
de desperfectos.
asegurese de que no ha
habido un corte de luz
siguiendo los procedimientos indicados mas
arriba.
t
en caso de no haber
sufrido un corte de luz,
dirijase a la grafica que
aparece en la pagina 32,
para procedimientos de
reparacion de desperfectos.
30
Si'.ntomas
Medidas
Si usted tiene un'flujo
continuo pero o un residuo de
cloro, cuando hace el examen
del cloro.
Cambie la membrana
Si el anodo despide un olor
dulce (en lugar de un olor
fuerte de cloro).
Cambie la mcmbrana
Si la membrana esta rota o
perforada.
Cambie la membrana
Las abrazaderas exteriores
de la tapa del generador de
desinfectante no permanecen
cerradas.
Examinelas por acumulacion de
sal y limpielas.
'31
GKAFICA PAHA TA KEPAHACIQN DE IX5PTMT3CiX3S
Si hubiese olor a cloro alrededor del sistema MOGGOD, podria haber varias
explicaciones para alio. Utilice la grafica que se indica mas aba jo para
tratar de detcnninar la causa.
Rcpare el flujo
de agua
Llame su
emprcsa de agua
iene el sistema un
flujo de agua?
Abra o a j u s t e
l a s valvulas
Limpio
Esta el tubo de
Venturi tapado con
tierra?
>
Estan abiertas las
valvulas de Venturi?
Examine el
sistema por
si tiene perdidas
(vea el dibujo en la
pagina siguiente)
Esta aspirando
el tubo?
Enderecelo o
destapelo
Corrijalo
Esta torcido o
tapado el tubo
de gas?
Esta conectado en
ambos extremes el
tubo de gas?
Hay olor a cloro?
OOMIENZO
32
Si el Venturi no tiene aspiracion, e>:amine las conexiones siguientcs
No lograra aspiracion en el tubo de Venturi si:
a.
no hay flujo de agua en las tuber ias principales,
b.
las tuberias'de gas estan desconectadas en el Venturi o en el
generador,
c.
la valvula B esta oonpletaroente abierta,
d.
las valvulas C o D estan cerradas,
e.
el tubo de Venturi esta tapado con tierra,
f.
las tuberias de gas estan tapadas o torcidas,
g.
la bonfca tiene una obstruccion de aire.
33
OOMO CAMI3IAR EL FUSIBLE EN EL REGULATOR DE POTENCIA
Cuando se del^e reemplazar el fusible
a.
Si el medidor de amperios en el regulador de potencia no indica
ni.Jigi.ma corriejite, apague el regulador de potencia.
b.
Examine el fusible en la parte frontal del regulador. Si el
fusible estuviese quemado, reemplacelo. Usted podra reconocer a
un fusible quemado observando unos puntos enncgrecidos y el
filamento roto.
Como reemplazar el fusible
1.
De vuelta la perilla negra pequena 1/4.de pulgada (en la parte frontal
del regulador de potencia) .
2.
Remueva el fusible quemado y tirelo.
Introduzca el fusible nuevo en la perilla negra.
extremos es indiferente.
La posicion de los
Empuje la perilla negra completamente dentro del receptaculo y
enrosquela, con el fusible adentro, nuevamente al regulador de
potencia.
3A
Rem leva la membrana.
Coloque la membrana nueva. La par-te de la junta blanca debe
colocarque contra la pared separadora.
Ajuste las tuercas hasta que la punta de los pemos aparezcan en la
superficie.
Llene la unidad con agua y sal, hidroxido de sodio, etc., siguiendo el
procedimiento de puesta en funcionamiento.
Coloque la tapa en su lugar. Ajuste las abrazaderas y las tuercas de
oreja.
Coloque los tubos flexibles de rebose en su lugar.
J<>
REEMPLAZO DE IAS BNUZhS ANODICAS Y CATODICAS
Coando se debe reemplazar la barra anodica
Es muy raro que se tenga que reemplazar el anodo. Su tiennpo de
duracion esta estimado entre siete y diez anos. Si es necesario
reemplazarlo, refierase a los pasos siguientes:
1.
Remueva la tapa de la unidad y siga los misroos pasos utilizados para
la limpiezaroensual,pasos 1 a 12 (comenzando en la pagina 15).
37
Afloje la(s) tuerca(s) que conecta el anodo a la pared de la unidad.
(Ev.ite remover las tuercas complete mente, solo debe aflojarias.)
Deslice la barra anodica hacia arriba y hacia afuera del perno.
Deslice Pa nueva barra anodica hacia abajo y sobre el perno.
Ajuste las tuercas.
38
Cuando S G debe reemplazar la barra catodica
Si el catodo se halla muy picado en la proximidad de la superficie del
liquido.
Reemplazo del catodo;
1.
Remueva la tapa de la unidad y siga los misrnos pasos que se utilizaron
para la linpieza mensual, pasos 1 a 12. (Coroenzando con la pagina
15.)
39
Afloje la tuerca que conecta el catodo a la pared de la unidad.
(Evite sacar la tuerca conpletamente, solo debe aflojarla.)
Deslice la plancha catodica hacia arriba y hacia afuera del perno.
Deslice la nueva pi
catodica hacia abajo y sobre el perno-
Ajuste el perno.
40
•
El hidroxido de sodio puede descargarse en el suministro de agua.
No causara dafio al agua y ajustara el pH.
•
El hidroxido de sodio puede guardarse y agregarse mas tarde al
suministro de agua.
•
El hidroxido de sodio puede utilizarse para limpiar el sumidero o
el inodoro.
•
El hidroxido de sodio puede aLmacenarse en un recipiente no
corrosivo y utilizarse para hacer jabon.
42
SECRETARIA DE SALUD
SUBSECRETARIA DE REGULACION SANITARIA Y DESARROLLO
DIRECCION GENERAL DE INVESTIGACION Y DESARROLLO TECNOLOGICO
CELDA ELECTROLITICA
MANUAL DE OPERACION Y MANTENIMIENTO
fc.N
i
I
C E D A T
1987.
I N D I C E
INFORMACION GENERAL
-----
ESTRUCTURA DE LA CELDA ELECTROLITICA
INSTRUCCIONES DE OPERACION
MANTENIMIENTO DE LA CELDA ELECTROLITICA - - RECOMENDACIONES
-
ACCESORIOS Y REACTIVOS
mi
-
1NF0RMACI0N GENERAL
Debido a la accion de corriente directa. la Celda Electrolitica ioniza soluciones de cloruro de sodio, produciendo cloro gaseoso.
Al ser dosificado este
al agua para consumo humano, produce la desinfeccion y potabilizacion bacteriologica.
PRINCIPIO DEL METODO
La Celda Electrolitica se basa en el proceso de electrolisis, esta forir.ada por
dos compartimientos;uno de ellos contiene una solucion de cloruro de sodio en
agua y, el otro de hidroxido de sodio tanbien en agua. Al pasar la corriente
electrica a traves de los electrodos y soluciones, y de acuerdo con la intensidad medida en amperes que proporcione una fuente de corriente electrica regulada, la celda producira cloro mediante una reaccion de electrolisis en el compartimiento del cloruro de sodio.
El gas cloro sera introducido a la tuberia
del agua mediante un inyector Venturi logrando con esto 'desinfectar el agua de
consumo humano de poblaciones rurales hasta de 2000 habitantes.
El el compar-
timiento de hidroxido de sodio se producira hidrogeno que se desprendera a la
atmosfera.
ESTRUCTURA DE LA CELDA ELECTROLITICA
(Ver Fig. 1)
La eel da ( A ) contiene una solucifin saturada de cloruro de sodio y un
electrodo de grafito ( 2 ) .
La membrana de Nafion (3) es un polfmero permeable a cationes (iones po^
sitivos) y compuestos polares.
Es impermeable a aniones (iones negativos) y a compuestos no polares.
La celda Qi) contiene una soluci6n de hidr6xido de sodio y un electrodo de acero inoxidable.
Los.electrodos estan conectados a una fuente reguladora de corriente dj[
•recta; el electrodo de grafito esta conectado al polo positivo (5) de
la fuente y el de acero inoxidable esta conectado al polo negativo (6)
de la misma.
El cuerpo de la celda ( A ) contiene un orificio de desahogo ( 7 ) el cual
permite que la presifin atmosferica ayude a la extracciSn del cloro gaseoso que sera extrafdo por un inyector Venturi.
La tapa (8) de la celda tiene en cada uno de sus extremos dos orificios:
r
1. En la celda (A)
- Orificio alimentador para cloruro de sodio (9)
- Orificio para la salida de cloro gaseoso (lo)
i.
En la celdafB
- Orificio alimentador\para hidrfixido de sodio (1
- Orificio para la salida de hidrfigeno gaseoso 02,
INSTRUCCIONES DE OPERACION
Disolver 900 gramos de cloruro de sodio en
3 litros de agua destiiada
y depositaries en la celda Q y .
Disolver 300 grarnos de hidroxido de sodio en 3 litros de agua destiiada
y depositaries en la celda ( B ) .
Colocar la tapa (s)
fito (^
ble (Q
de la celda, de manera tal que el electrodo de gra-
quede sumerfido en el cloruro de sodio y el de acero inoxidaen el hidrdxido de sodio.
Conectar el electrodo de grafito (2) al polo positivo (5) de la fuente
reguladora.
Conectar el electrodo de acero inoxidable Q y al polo negativo ^ ) de
la fuente reguladora.
Conectar la manguera de succion del cloro a la celda (Jty y al eyector
Venturi.
Tapar los orificios de alimentacidn (9) y Q p
de
^ as celdas con sus res^
pectivos tapones.
Dejar libre el orificio (12) de salida de hidrdgeno.
Pennitir el paso del agua a traves del eyector Venturi
Conectar la fuente" reguladora.\
La produccidn de cloro es proporcional a la intensidad de corriente
o amperes que sean pasados a traves de la celda; es decir a mayor
amperaje, mayor produccidn de cloro y viceversa.
- Imciada la operacion de la celda, esperar 10 minutos para detenmnar
cloro.
- Comenzar con la toma mSs cercana a la instalaci6n e ir avanzando a
tomas domiciliarias mSs alejadas para determinar los amperes en la
cual la celda debe trabajar, procurando no exceder los 7 amperes
de alimentacifin.
MANTENIMIENTO DE LA CELDA ELECTROLITICA
Proporcionar mantenimiento cada 100 horas de tuncionamiento de la celda.
Esto depende de la calidad de la sal utilizada, ya que algunas marcas del
mercado presentan mSs impurezas que otras.
Apagar y desconectar la fuente reguladora de voltaje.
Desmontar las conexiones electricas de ambos electrodos (|) y (4).
Desconectar todas las mangueras 0 conexiones que esten sobre la tapa Qi)
de la celda.
Desmontar la tapa de la celda.
Dcsechar las soluciones de las celdas ( A ) y (F) por medio de los tapones
de desague O
.
Enjuagar con chorro de agua ambas celdas ^ ^
Desmontar el portamembrana ( p
y
y (jy y desaguar nuevamente.
a chorro de agua, lavese.
Secar las celdas ( A ) > T B ) y el portamembrana (T)
Volvier a montar el portamembrana ("M respetando la colocacion inicial, ya
que !la membrana Nafion ^3) tiene funciones diferentes en cada uno de sus
ladob.
T
Seller con silicon las uniones del portamembrana (T) a su soporte para no
',-"^rmHtir fugas por las uniones.
•* Asegtirar que el material rojo de empaque este ubicado en su lugar, \en
•' defepto sellarlo con silicon.
Si es necesario, reemplazar 0 reparar las conexiones y cables electricos
que tonectan los electrodos.
su
RECOMENDACIONES
El cloro es un gas (mortal) m5s pesado que el aire; por lo que si se pre
senta una fuga debe desconectar inmediatamente la fuente reguladora de
voltaje, permi'tir una ventilacifin abundante y abandonar el Srea.
El cloruro de sodio se adiciona de acuerdo al control que se tenga de clc)
ro residual en las tomas dimiciliarias, pero es conveniente cambiarlo
cada 8 dias.
El hidroxido de sodio es una solucifin que produce quemaduras graves en la
piel u ojos por lo que se debe lavar inmediatamente con abundante agua la
zona afectada.
En la piel aplicar una soluciSn al 50% de acido acetico y
en y en los ojos una solucion de 30 grs de bicarbonato en un litro de agua
potable.
Cada 10 dias se diluye el hidroxido de sodio con 50 ml. de agua ya que
este
-
aumenta su concentraciSn.
En ciertas proporciones, el hidr<5geno puede ser explosivo, por tal motivo
no debe ser retenido; ni fumar en el Srea de ubicacicm de la celda.
:
\
zJ'Jfoo Itocar ninguna de las soluciones con los dedos cuando este funcionando\
!
la ;celda, ya que existe riesgo de electrocutarse.
Al desechar las soluciones, tenga precaucion de no salpicarse ya que exis
•
te el riesgo de quemaduras.
-
El orificio contenido en el cuerpo de la celda no debe estar obstruido.
-
Al estar la celda fuera de operacifin, se debe retirar uno de los cables
de los electrodos de la fuente reguladora de voltaje.
-
Es recomendable usar sal no yodatada (de grano).
-
Al lavar el portamembrana no utilice cepillos ni otros objetos ya que se
puede romper la membrana.
\
2 l
ACCESORIOS Y REACTIVOS
1.
Fuente reguladora de re:•hi^-^n c c vvi tf *. *£
1.
Manguera de 1/4
3.
Solucifin de c l o r u r o de sodio, to psae&as&wsssa eb &xzte c^.v^^^^s
4.
SoluciSn de hidrfixido de sodio.
de pulgada para l a succifin del gas c l o r o .
p«fcs.
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FIGURA 5
r
1
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CORTE
TRAR-SVERSAL
FIG. 6
r
CELDA
ELECTROLITICA
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M/\I\JT LEfXJIMIEfMTQ
O Z O N O C L d R A O O R E S
o p e r a d o r e s
d e
p l a n t a
Oper-OXI-GIDOX-1
O P E R A C I O N
R e c o r d a r
EL EQUrPO SOLO DEBE ESTAR FUNCIONANDO SI KL AGUA A TRATAR ESTA
CIRCULANDO
I
-c=^=y\
' /
J
rAsx
C/3
O o n t r o l e s
c l .i. a r i o s
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CEL.DA
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:
T'ENOA
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A G U A
V
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Si no t u v i e r a .
se deberan
agregar!
-
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f'
•
S/XL,
» Oper-OXI-GIDOX-2
2 .
L/\
O K N 3 XD A D
D E
L/\
S O I ^ U O T O N
OK
Para ello use el densimetro. Saque la tapa e introduzoa el
densimetro hasta el fondo en el compartimento de la solucion de
soda. Apriete la pera de goma y de.je que el liquido eritre en el tubo
El nivel del liquido debe
estar dentro de la zona
verde en los equipos GIDOX
6 dentro de los valores
10r>0 - 1125 en los equipos
OXT.
m
Cuando la solucion este muy densa ocurrira que el nivel estara
n
1.125
I
A
EQUIPOS GIDOX
EQUIPOS OXI
Cuando esto ocurra, habra que diluir la solucion de soda. Para ello:
\
AGREGUE AGUA HASTA QUE LA DENS 1 DAD ESTE
DENTRO DE LOS VALORES ACON'SE^JADOS
(Vol. de agua a agrogar = i/3 - 1/2 del
volumen de
la camara de
soda)
Mant-OXI-1
M A N T E N I M I E ^ N T Q
F r e c u e n c i
C OX
IE >
a
De acuerdo al tipo de sal usada sera
de mantenimiento:
la frecuencia
SAL PURIFICADA STERLING = CADA 5 MISSES DE OPRRACION CONTINUA
SAL COMERCIAL COMUN = cada 1 MES DE OPERACI.ON CONTINUA
La
f o r m a
ole^
r e a l
x z a r l a
3CD
1. CORTE LA CORRIENTE
2. DESCONECTE LOS CABLES ELECTRICOS AFLOJANDO LAS TUERCAS EN LA
PARTE POSTERIOR DEL COMANDO Y RETIREL09.
Mant-OXI-2
•
0_Q
3. DESCONECTE EL TUBO DE LOS GASES EN LA TAPA DE LA CELDA.
4. INCLINE LA CELDA DE FORMA QUE LAS SOLUCIONES EN AMBOS COMPART!MEN
TOS SALGAN POR LOS DESBORDES. COLOQUE UN RECIPIENTS EN LA DESCAR
GA DE LA SODA P'JES ESTA SOLUCION VOLVERA A SER UTILIZADA. LA
OT'RA SOLUCION SE DESCARTARA.
/
n
5. QUITE LAS TUERCAS DE LA TAPA Y RETIRE LA MISNA.
Mant-0?U-3
6. ENJUAGUE EL INTERIOR CON AGUA.
REMUEVA LOS ELECTRODOS QUITANDO LAS TUERCAS QUE LO SUJETAN, PARA
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^*?-y
Directors
B J Lloyd PhD
M Pardon BSc
D Wheeler BSc
Address
PO Box 92
Guildford
GU2 5TQ
England
'*:.Al
water quality for
developing countries
Our
Reference:
Your
Date:
Reference:
VIGILANCIA DE CALIDAD DEL AGUA
Uno de los pilares fundamentales de la cstrategia a fin de
alcanzar las metas propuestas para la Decada del Agua (decenio 1981-1990)
es la vigilancia de calidad de agua de consumo humano que se distribuye a
las poblaciones.
En mayor o menor medida, los Paises en vias de desarrollo se
enfrentan a probleraas que les impiden implementar en forma adecuada programas de esta naturaleza. En algunos casos, es la falta de personal tecnico entrenado adecuadamente; en otros, los costos de equipos e insumos
hacen prohibitiva la implementacion de estos programas de vigilancia.
Del Agua es una organizacion sin fines de lucro basada en
Inglaterra cuyos tres objetivos principales son: apoyar Programas de Vigilancia de Calidad de Agua con cursos cortos de entrenamiento en temas relacionados a vigilancia y tecnicas analiticas de monitoreo; suministro de
equipos de monitoreo al precio de costo de manufactura; y respaldo de insumos para los Programas, suministrandolos a precios de descuento obtenidos
en el Reino Unido. Las especificaciones del equipo asi como las caracterxsticas de los cursos de entrenamiento y del apoyo que se ofrece se detallan en las paginas siguientes.
Informacion adicional se puede solicitar a la direccion postal
arriba senalada o a:
Mauricio Pardon
c/o CEPIS
Casilla Postal 4337
Lima 100, Peru
Telex: 21052 PE CEPIS
Telefono: 35-4135
DelAgua is a non-prof itmakingorganistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
Registered Number 1860842
Registered Offices 1 28 High Street Guildford UK
a
water quality for
developing countries
Directors
B J Lloyd PhD
M Pardon BSc
D Wheeler SSc
Address
PO Box 92
Guildford
GU2 5TQ
England
PORTABLE WATER TESTING KIT
<s~.
/ •<:
S
,:-1
Components:
1:
2:
4:
Faecal colt form bacteriology
Membrane filtration equipment and 44°C integral incubator
and 12 volt Battery + separate charger
Combination chlorine residual and pH comparator.
Turbidimeter tubes: High range
20-2000 T,U.
Low range <10
Combination electronic temperature and conductivity meter
Low range
0 - 200 pS
Medium range
200 - 2,000 yS
High range
2,000 - 20,000 pS
DelAgua is a non-profitmaking organistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
Registered Number 1860842
Registered Offices 128 High Street Guildford UK
DelA<ft£3
water quality for
developing countries
Directors
B J Lloyd PhD
M Pardon BSc
D Wheeler BSc
Address
PO Box 92
Guildford
GU2 5TQ
England
DELAGUA PUBLIC HEALTH TRAINING PROGRAM iKS
Specification
of a n a l y t i c a l e q u i p m e n t f o r w a t e r t e s t i n g
Faecal coliform t e s t
Incubator
Chlorine
-
Performed
technique
filtration
schemes
by
the
membrane
filtration
using
integral,
purpose
made
apparatus.
section
Kits incori :ate incubators which permit
the incubation of up to 17 membranes
within reusable aluminium petri dishes.
residual
Performed by a simple comparator method
using DPD reagents - results in mg/1.
Turbidity
Performed by a tube/extinction method for
the range 5 - 5000 TU.
Filterability
For use in conjunction with turbidity for
process selection - based on a membrane
filtration technique.
Conductivity
Performed using a robust electronic meter
and probe.
,
Temperature
Performed using a robust electronic meter
and probe.
PH
Performed by a simple comparator method
using phenol red reagent.
\
\The water testing kit is supplied with an integral rechargeable
battery, and is capable of independent field operation for a minimum
of five days before recharging is necessary. Charging is performed
fro^m mains electricity (110 or 220 volts AC) using a matched charger
unit which is supplied.
The check list of equipment noraally contained within the DELAGUA
water testing kit is shown overleaf.
DclAgua is a non-profitmsking organic tstion concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
Registered Number 1860842
Registered Offices 1 ?. 8 High Street Guildford UK
Directors
DelAguS
Address
water quality for
developing countries
B J Lloyd PhD
M Pardon BSc
D Wheeler BSc
PO Box 92
Guildford
GU2 5TQ
England
CHECK LIST OF EQUIPMENT
Quantity
-i rem
ll
Carrying case with incubator
2:
Membrane Filters
Consumables
3i
Pads and Dispenser
Consumables
4t
Forceps
5i
Aluminium Petri Dishes
6t
Gas Lighter
7«
Sample Jug and Cable
81
Filtration Tube
9;
Tube Support
at
Upper '0' ring
b»
Lower '0' ring
c»
Membrane support
101
Methanol Dispenser
Hi
Suction Pump
12i
Suction cup
13i
Turbidity tube
14«
Culture Medium
(in small autoclavable bottles)
151
Chlorine
)
)
)
16«
pH
17«
DPD pastilles No. 1
Consumables
181
DPD pastilles No. 4
Consumables
19i
pH pastilles
Phenol Red
Consumables
20i
meter
21.
Conductivity)
)
Temperature )
22.
Conductivity electrode
23i
Temperature Probe
24*
Tissue/Clean Cloth
comparator
Consumables
DelAgua is a non-profitmaking organistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
Registered Number 1860842
Registered Offices 1 28 High Street Guildford UK
DelAgua
water quality for.
developing countries
CHECKLIST FOR THE OPERATION OF THE
Directors
B J Lloyd PhD
M Pardon BSc
D Wheeler BSc
Address
PO Box 92
Guildford
GU2 5TQ
England
'DELAGUA'
WATER TESTING KIT
YES
IS WATER CHLORINATED
"> TAKE SAMPLE WITH
VACUUM FLASK PERFORM CHLORINE
RESIDUAL, pH AND
TURBIDITY TESTS
NO
J$L
TAKE SAMPLE WITH
STERILE SAMPLING
CUP
^
I S FREE CHLORINE
RESIDUAL MORE THAN
0 . 1 rag/1 AND TURBIDITY
LESS THAN 5 TU
NO
YES
_&
PERFORM FAECAL
COLIFORM TEST <T"
I
IS CONFIRMATION
OF BACTERIOLOGICAL
QUALITY REQUIRED
YES.
JL
±.
NO
PLACE MEMBRANE
PLATES IN THE
INCUBATOR
^
COMPLETE PHYSICOCHEMICAL ANALYSIS
^L
TAKE IMMEDIATE
<r
ACTION
INFORM RELEVANT
AUTHORITIES
WATER QUALITY
ACCEPTABLE <r
WATER QUALITY
<r
FAILURE
WATER QUALITY
UNACCEPTABLE
TAKE IMMEDIATE
ACTION
INFORM RELEVANT <r
AUTHORITIES
ML
J05S_.
YES
IS SANITARY INSPECTION
SATISFACTORY AND ARE
PHYSICOCHEMICAL TEST
RESULTS NORMAL AND
ACCEPTABLE*
YES
THE FOLLOWING DAY »
IS FAECAL COLIFORM
COUNT LESS THAN 1
PER lOO ml
NO,&_
IS FAECAL COLIFORM
COUNT LESS THAN 10
PER lOO ml
NO.
YES
IS FAECAL COLIFORM
COUNT MORE THAN 10
PER lOO ml
* ACCEPTABILITY I S JUDGED BY NORMAL WHO C R I T E R I A
DelAgua is a non-profitmaking organistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
P\
_
I
A
~m . . - *
DelAgua
..^
,
Directors
B J Lloyd f
Address
PO Box 92
---
water quality for
developing countries
Guildford
QU2 5TQ
England
DEL AGUA PUBLIC HEALTH TRAINING PROGRAMMES
DelAgua is a non-profitmaking organisation. The following represent
only those charges necessary to cover costs.
Training programmes conducted in-country include provision of up to
two weeks tuition in public health science, sanitary inspection,
water treatment technology, water quality testing, monitoring and
surveillance.
Any aspect can be emphasised according to the
requirements of the commissioning agency.
CHARGES
Travel and subsistence of two instructors
(Latin America)
*
Equipment (per unit)
1000 USD
Air freighting and insurance for equipment
(per unit)
Course fee for materials
(per student)
250 USD
62.5 USD
* based on travel fares plus U.N. subsistence allowance rates
DelAgua is a non-profitmaking organistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
DelAgui
water quality for
developing countries
Directors
8 J Lloyd PhD
M Pardon BSc
D Wheeler BSc
Address
PO Box 92
Guildford
GU2 5TQ
England
DEL AGUA PUBLIC HEALTH TRAINING PROGRAMMES
The following topics and exercises will be incorporated into the two
week training programme!
Introduction! water-borne and water
associated
disease! The
faecal-oral route of infection* Infective dosest Faecal indicators
and pathogens in water> The International Water Decade - goals,
legislation and standards» GEMS.
Water treatment! the multiple barrier principle! Treatment process
selection for rural and sub-provincial water treatment worksj
Treatment process design, operation and maintenance! prefiltration,
slow sand filtration and disinfection! Commissioning and monitoring
(quality control)» Laboratory exercise on disinfection.
Sanitary inspection! Field visit for sanitarian duties and reporting
results! Infrastructural requirements for action on maintenance and
repairs.
Water quality monitoring and surveillance! Definition of roles of
supply agency and health authorities! Water quality testing! World
Health Organisation Guidelines! Volumes I-III.
Water
testing*
Bacteriology!
Field
preparation
of
media!
Sterilisation of media! Packaging, checking, and maintenance of
testing equipment.
Water
testing!
Physico-chemical
parameters!
Field
exercises
involving sampling of raw, treated, and distributed water samples!
Reporting results.
Relevance of standards! Interpretation of water quality results!
Formulation of sampling programmes! Water quality and health.
DelAgua is a non-prof itmaking organistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
develi ping countries.
Registered Number
1860842
Registered Offices 128 High Street Guildford UK
DelAgua
water quality for
developing countries
Directors
B J Lloyd PhD
M Pardon BSc
D Wheeler BSc
Address
PO Box 92
Guildford
GU2 5TQ
England
DELAGUA WATER SURVEILLANCE AND MONITORING SUPPORT SERVICES
It is recognised that the cost of consumables for water testing in
developing countries is often prohibitive. For this reason DelAgua
is resolved to supply all necessary media, membrane filters, pads
and spares at cost to any nominated port in the country of use of
the water testing equipment.
Consumables can be transported by
ocean freight or air freight. Prices will be negotiated on bulk
purchase in the UK and discounts passed on to the user. Typical
current costs for faecal coliform analysis in Latin America by such
transfers are less than 0.2 USD per sample.
Unfortunately, DelAgua is not in a position to arrange clearance
from ports and customs, and does not have the resources to engage
agents. Thus clearance must be arranged by purchasers. However,
all goods will be insured against damage or loss in transit.
It is a condition of transaction that all ' equipment and support
services including training be paid for in advance. DelAgua has no
administrative support for invoicing in arrears.
Whilst every effort has been made to
not in a position to guarantee these
but DelAgua does guarantee that all
supplied at cost and that costs will
minimum.
quote accurate costs DelAgua is
costs for an indefinite period,
equipment and services will be
continue to be kept at absolute
DelAgua is a non-profitmaking organistation concerned with training consultancy in water treatment, water quality surveillance and sanitation in
developing countries.
Registered Number 1860842
Registered Offices 1 28 High Street Guildford UK
f
GRUPO "A"
RECOMENDACIONES DE INVESTIGACIONES PARA EL FUTURO
El grupo reconoce que el equipo de generacion de gases oxidantes
MOGGOD, es una herramienta mas para la desinfeccion del agua y que se puede
elegir de acuerdo con las condlciones locales sin que esto nec.esariamente
constituya la eliralnacl6n de otras alternativas ya en utilizacion.
Por tanto, se plantean las sigulentes recomendaciones:
•.
.
La investigacion en relacion a esp^cies de oxidantes, eantidades en que
se producen, eficacia de su action, formacion de organo dorados y
otros subproductos, que sea /eali^ada por las instituciones cuya
infraestructura es perinitida,/debiendo comunicar a los palses y/o
instituciones interesadas los resultados de esas investigaciones.
Interesar a ACU... . y EPA en trabajos de investigacion en areas
relacionadas con el MOGGOD y tratar de involucrar a los gobiernos de
los difercntes palses para financiamiento de las investigaciones.
La
investigacion
de
la
operacion
(adaptabilidad,
instalacion,
operacion, insumos, eostos, seguimiento) sera ejecutada por los palses
participantes, debiendo establecerse un protocolo para la investigacion
y que los resultados scan compartidos estableciendose un banco de datos
al que los paises participantes tengan acceso.
4.
El protocolo de investigacion debera contemplar, entre otros aspectos,
los sigulentes:
4.1
Analisis de la situacion salud antes, durante y despues del proceso de
desinfeccion con el MOGGOD,
^
4.2
actitud de las comunidades ante las nuevas experiencias,
4.3
acciones de motivacion y educacion sanitaria continuada, las cuales
deberan aplicarse en las comunidades a beneficiar.
U.d
5.-
Desarrollo de tareas de investigacion en materiales a eiftplear en
electrodos, membranas y su disposicion, y de las partes constitutivas a
fin de atimentar su confiabilidad y eficiencia en la operacion, asi como
el estudio de fuentes alternas de energfa.
Se utilizara la retroinformacion de los protocolos de investigacion.
La OPS debera interesar a los gobiernos, a traves de los conductos
correspondientes, para que se lleven a cabo las acciones recomendadas.
- 2 -
Fomentar la inveastigacion local para la produccion y/o readecuacion
del equlpo y sus componentes a fin de mantener en operacion las
unidades.
DF.SARROLLO Y EVALUACION DE PROYECTOS
El desarrollo de la investigacion en su etapa inicial
debera realizarse
en diferentes condiciones ambientales y/o geograficas e ir acompanada
de una informacion epidemiologica consistente antes y despues de la
accion de desinfeccion con el MOGGOD.
Esta informacion epidemiologica servira como base de sustentacion para
la
implementacion de futuros proyectos en areas de sirailares
caracterfsticas las que solo necesitaran analisis microbiologicos y
examenes fisicoquimicos.
Replantear y/o continuar el desarrollo de la experiencia con el MOGGOD
a fin de establecer o coraplementar la informacion tecnica en forma
acumulativa. En otro orden de ideas, ampliar la experiencia con la
utilizacion de diferentes equipos. A *. V,,^^ / 4b
En todos los casos, establecer comparaciones tecnicas y economoraicas
entre MOGGOD y desinfeccion con tecnicas tradicionales.
Las investigaciones deberan desarrollarse en un tiempo prudencial,
dependiendo de las facilidades y condiciones locales.
COLA.BORACION HORIZONTAL E INTERNACIONAL
Toda la informacion que se necesite debera ser canalizada a traves de
las Representaciones de la OPS/OMS en los diferentes paises.
Aprovechar el recurso calificado que exista en las regiones como efecto
multiplicador para la difusion de esta tecnologfa.
S
•*
GRUPO "B"
RECOMENDACIONES Y FUTURAS INVESTIGACIONES
/ 1.
Objetivo del Seminario
a. Presentaclon del equlpo y avarices realizados en cada pais
b. Intercatnblo de experiencias
v. Desarrollo tecnologico
Comentario.
En el presence seminario se pudieron apreciar los
problcmas de instalacion de los equipos en cuanto a operacion y pnrametros
basicos de control (oxidabilidad, analisis bacteriologico, demands de cloro).
/
' j
2.
Recomendaclones
2.1
Especlficas
y 2.1.1
Instalado el equipo, consideramos
determlnaciones basicas sobre;
~ demanda de cloro
- cloro residual
- analisis bacteriologicos:
conveniente
llevar
a
cabo
las
coliformes totales y coliformes fecales
Previa a estas determlnaciones, se requiere llevar a cabo un estudio
epideiniologico antes de la instalacion de estos equipos de mezcla de
gases oxidantes, estudios tales como incidencia de enfermedades
gastrointestinales, desnutricion, etc.
/
(P J
2.1.2
Evaluar comparatlvamente con el equipo de gases oxidantes los otros
equipos de desinfeccion que vienen funcionando.
2.2
Generales
fit. Gi^KS
1 2.2.1 Que a traves del CEPIS t^rrxrr' una red de informacion sobre el
y rfnaaciamionto del equipo de mezcla de gases oxidantes en los paises
participantes en el seminario.
/ 2.2.2
Continuar con la investigacion del equipo y oonitoreo.
.. 2.2.3
Recomendar a la industria para la investigacion nacional sobre el
perfeccionamiento del equipo de acuerdo a las necesidades y las
condiciones propias de cada lugar (unidades de bacteria, sal comun).
\
2.2.4
Vincular a las universldades con el desarrollo de investigacioanes
basicas, tendlentes a evaluar y desarrollar la apllcacl6n de la
tecnologla.
/ 2.2.5
Estimular la creacion de pequefias industrias o de capitales locales
para la produccion de estos equlpos.
' 2.2.6
'
Incluir en la evaluacion un mayor numero de cquipos para utilizarlos en
diferentes comunidades.
/
2.2.7
J
«/2.2.8
Estudio epidemiol5gico para ver el impacto del sistema de desinfeccion
en la comunldad, especialmente en la poblacion infantll.
Recomendar el incentivo de la promocion y educacion sanitaria, con la
finalidad de propiclar la aceptacion del equlpo de mezcla de gases
* ,i
.
i
j j _ j _ _
i
_
i
.. _ i
oxldantes
en las
comunidades
o_ lugares
a
instalarse.
2.2.9
Se propone tener los\resultados de la evaluacion y desarrollo de 1J
investigacion en el periodo de un ano.
•
Fuentes de financiamlento
Para la evaluaci5n y adqulsicion de equipos de gases oxidantes es
necesario contar con la colaboracion de las sigulentes entidades:
>
OPS/OMS
UNDP
BID
AID
GTZ
C}?EPIS ( a s i s t e n c i a t e c n i c a e i n t e r v e n c i o n mas a c t i v a )
- CIf$ (Holanda) M w
U ^ ^ l ^ J
c^L
Axf<^™^- Colaboracion entre las entidades de salud, universldades
En el caso especlfico de cada pais, ver la posibilidad de financiar la
preparacion de tesis sobre la evaluacion del equipo de gases oxldantes por
parte de los estudiantes.
\
GRUPO "C"
RECOMENDACION DE FUTUROS PROYECTOS INMEDIATOS
/l.
Uniformizacion de formatos de captura de datos:
a.
b.
Control de operacion
Control de calidad: bacteriologica y fisicoqufmica
' 2.
Elaboracion de manuales de operacion y mantenimiento practicos
accesibles (a nivel de las personas que manejaran el equipo).
y
(J 3.
Despues de determinar la zona en donde se aplicara el equipo,
desarrollar un estudio de morbilidad de la poblacion (por estatus de
edades) para observar el impacto social-sanltario de utilizar un nuevo
desinfeetante.
f 4.
Hacer un estudio para determinar el nivel de cloro residual necesario
en tanque y/o red de distribucion para obtener agua sanitariamente
segura.
l/5.
Efeactuar un analisis comparativo (tecnico-economico) de la utilizacion
del equipo generador de gases oxidantes versus otros procesos de
desinfeccion.
6.
Desarrollar una tecnologfa praetiea y a bajo costo para la purificacion
de la sal comercial.
7.
Verificar la produccion de gases oxidantes a diferentes condiciones de
presion y temperatura.
RECOMENDACIONES A LARGO PLAZO
1.
Investigacion sobre la produccion de electrolisis a partir de otro tipo
de energla no convencional.
2.
Investigaci5n sobre el uso de diferentes electrodos (y su eficiencia) y
membranas, con miras a reducir costos.
3.
Estudio de la factibilidad de produccion parcial o total del equipo
MOGGOD a nivel nacional.
4.
Continuacion de la invaestigacion concerniente a la caracterizacion de
los gases generados con la finalidad de evaluar sus efectos sobre la
salud.
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Los Alamos Technical Associates, Ing.
WP-87-010
UNIDAD DE PURIFICACION DE AGUA
1.
DESCRIPCION DEL SISTEMA ELECTROLITICO
Los Alamos Technical Associates, Inc. (LATA) ha desarrollado un raetodo
electrolitico simple de bajo voltaje para la esterilizacion del agua potable,
que se puede emplear en localidades remotas, pafses en vfas de desarrollo y
areas de desastres naturales. El metodo solo requiere de una solucion de sal
o agua de mar para producir una mezcla sinergetica de oxidantes directaraente
en soluci6n. Un volumen de la corriente del anodo mezclado con 500 a 1,000
voluraenes de agua contaminada extermina rapidamente los microorganismos y
patogenos humanos resistentes, produciendo agua apta para el consumo humano y
quedando un residual de cloro para irapedir el crecimiento interior de los
microorganismos durante el almacenaje y distribucion.
Los requerimientos
energeticos son 12 V CC, 14A para una unidad capaz de producir 8,000 galones
de agua tratada por hora.
La unidad prototipo de purificacion electrolitica de agua es un modulo
sencillo y resistente. Una unidad modular consta de una bomba, tuberfa,
transformador CC, una celda electrolitica de 3 x 5 x 0.5 pulgadas, controles y
un recipiente sellado para romper el vacfo. Este modulo cabe en un estuche de
fibra de vidrio intemperizado de 24 x 24 x 12 pulgadas. La unidad pesa
aproximadamente 23 kg, principalraente en razon del transformador y el estuche
de fibra de vidrio.
Para operar la unidad se requiere de una fuente de energfa externa,
como por ejemplo una baterla de automovil (baterfa de almacenamiento de 12 V)
o panel solar (14-45 W), y una solucion de alimentacion de salmwera diluida,
0.75 M NaCl. Cuando la salmuera diluida entra en contacto con las superficies
catallticas de metales Grupo VIII de la celda electrolitica, se produce en el
anodo una mezcla de oxidantes que Incluye cloro libre, hipoclorito, radicales
libres de cloro y oxfgeno y ozono. Esta corriente de efluente del anodo se
utiliza para tratar el agua contaminada. La corriente de efluente del catodo
se elimina.
Cuando la corriente del anodo se mezcla con 500 a 1,000 volumenes de
agua contaminada, los oxidantes de corta vida matan a los microorganismos,
destruyen los componentes organicos como fenoles, precipitan metales pesados
corao oxidos y mejoran el color, olor y sabor del agua. El cloro proporciona
un residuo de larga duracion para impedir que vuelvan a crecer las bacterias y
permite verificar el tratamiento de agua mediante pruebas patron de
concentracion de cloro. La Figura 1 presenta un diagrama del proceso.
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2. "
POSIBLES APLICACIONES
Esta unidad simple, pequetfa y resistente de tratamiento de agua puede
utilizarse en muchas localidades ya que no necesita de una red de suministro
electrico desarrollada, personal de mantenlmlento capacitado, surainistros
quimicos pellgrosos o importados, nl tampoco de un apoyo industrial
adyacente. Entre sus posibles aplicaciones podemos mencionar:
-
Localidad perrnanente remota,
grupos de exploraclon m5vil,
operaciones de rescate en desastres naturales,
unldades railltares,
instalaclones de embarcaciones marftiroas, y
corao algicida en sistemas de agua refrlgerante.
El tamaffo de la unidad puede adecuarse a la aplicacion deseada,
pudiendo colocarse varios modulos en serie para aumentar el volumen de agua
tratada. Las unldades pueden sacarse individualmente de la lfnea para su
mantenlmlento, sin afectar la produccion. El raetodo es 100% efectivo contra
—' ££ii> Legionella pneumophilia, Pseudomonas aeruginosa, quistes de Giardia y
esporas de Bacillus subtilis.
3.
PUNTO DE CONTACTO
Para mayor informacion
trataraiento de agua dirigirse a:
relacionada
a
este
metodo
exclusivo
Los Alamos Technical Associates, Inc.
P.O. Box 410
1650 Trinity Drive
Los Alamos, New Mexico 87544
E.U.A.
t
Atencion: H.F. Gram
Telefono; (505) 662-9080
de
PRIMER SEMINARIO INXERNACICNAL SOBRE EffiSINFBOCICN
DEL AGUA POR OXIDANTES ME2CLAD0S
MINISTERIO DE SALUD
REPUBLICA DE PANAMA
Ing. Franciscx) Osorio
DESCRIPCICN DEL PROGRAMA:
El Ministerio de Salud a trav£s de la Direcci6n Nacional de Ingenierfa Sa
nitaria y Conservacioh es el responsable de dotar de agua potable a la po
blaci6n rural de menos de 500 habitantes msdiante sistanas de acueductos
o pozos pufolioos accionados con baifoas roanuales. Las ocrnumidades rurales
de mayor poblacion y el area lirbana, son abastecidas por el Institute de
Acueductos y Alcantarillados Nacionales (IDAAN). '
El programa de acueductos rurales del Ministerio contenpla que una vez
construido el acueducto la oanunidad beneficiada sea la responsable de ad
ministrar, operar y mantener el sistevna, limitandose el Ministerio de Salud a las responsabilidades de supervision y apoyo tecnico requerido por
la ccrnunidad. Este mecanismo de trabajo se ha desarrollado coo. bastante
exito en la Republica de Panam£ y debido a este se han podido construir
ma's de 1000 sistemas de acueductos rurales en todo el pals, abasteciendo
a mas de 340.000 habitantes del area rural cor. conexioh dcraiciliaria.
De los 1000 sistemas construidos aproxoiitadamsnte el 90% utilizan agua sub
terranea ccmo fuente de abasfcecindento, mediante pozos profundos o manantiales captados en su nacijnientp. El 10% restante utiliza agua superficial que en la mayorfa de los casos es tratada a travel de filtracich len
ta antes de ser distribuida.
Menos del 5% de los sistemas en operaci6n son dorados actualmente y
los analisis de agua se hacen en forma puntual sin obedecer a un ve£
dadero programa de control de calidad del agua abastecida.
EXPERIENCIA CON EL BQUIPO MQGGOD
La OPS/CMS ha donado a la Fepublica de Panama1 (8) equipos MOGQOD can
pletos con su correspondiente sal TNAS.
Este equipo fug distribuido
en la siguiente forma:
(4) equipos para ser instalados por el IDAAN
(4) equipos para ser instalados por el Ministe
rio de Salud
El Ministerio de Salud instal6 el 18 de noviembre de 1987 el primer
generador de gases oxidantes con una capacidad de 1/2 libra de oxidan
tes por dla en la ccmunidad de Loma Bonita, Provincia de PanamS. Esta ccmunidad se dedica mSs que nada a la ganaderia y la agricultura y
por
su cercanla a la ciudad de Panama1, parte de su poblaci6n trabaja
en la misma.
1.-
Caracterlsticas Principales del sisteroa de acueducto;
Numero de conexiones
= 65
Poblacion servida
= 330 habitantes
e
Fuente de Abasto
= Pozo profundo con forro de 6"0
Caudal de bombeo
= 45 gal/min. (2.85 1/s)
Capacidad de almacenamiento =4500 galones (17.0 m 3 )
2.-
Equipo instalado
= bomba sumergible de 2 H.P.
Red de distribucion
= 1 km de radio aproximadamente en 2"0 PVC
Instalaci6n, del equipo:
El equipo rue" instalado siguiendo las indicaciones que aparecen en
el manual suministrado, se utiliz6 una valvula de paso para crear una
- 3 -
presion diferencial y regula el vacio producido por el venturi.
Hasta la fecha no se ha podido instalar un medidor de gases que
permita conocer la cantidad de oxidantes prcducidos.
La instalaci6n electrica se hizo de manera que el generador de oxi
dantes sea controlado con la cajilla de la bcntba y sus controles
de niveles.
No hubo probleroas t£cnicos en la instalaci6n de este equipo.
3.- Calidad del agua cruda;
El agua cruda es de buena calidad, ya que los analisis no presentaron bacterias coliformes, con una demanda de cloro de 0.5 mg/1 a una
temperatura de 25°C.
4.-
Funcionamiento del Equipo;
La operaci6n del equipo se inici6 a diferentes amperajes para obtener el que se ajustase ma's a la producei6h diaria de agua, obteniendose un amperaje obtimo de 5 amp. para mantener un claro residual de
salida de 0.8 a 1.0 mg/1. Con esta producci6n de gases se obtuvo en
la red un cloro residual de 0.6 mg/1 en las casas ma's centricas a
0.3 en las viviendas mils alejadas.
5.- Ventajas obseryadas de la desinfeccidn con el equipo fPGGOD:
-
FScil instalacich
-
FScii operaci6n para el personal con poco adiestratramiento encargado de operar los acueductos rurales.
-
Mejor control en la dosificaci6n para obtener un cloro residual de
seado, "cemparado con el clorinador por goteo.
- 4 -
-
El equipo de 1/2 libra diaria se ajusta a las demandas diarias de
agua de las poblaciones y a la calidad del agua abastecida por
el Programa de Acueductos Rurales.
' ~ Dssventajas:
Debido al poco tiempo que tiene el equipo IOGG0D de estar instalado y a la poca informacidn disponible sobre el mismo se desconoce
lo siguiente:
-
Principales problemas de mantenimiento y reparaci6n de los mismos.
-
Dj.sponibilidad y cos to de repuestos, sobre todo la membrana semipermeable y los electrodos.
-
-
Experiencias obtenidas trabajandp con corriente directa.
Asuntos importantes de instalaci6n del fflOGGOD;
Se ha querido resaltar el hecho de que debido a que la producci6n
del pozo disminuye en la estacion seca y la bomba es controlada automSticamente por el control de niveles, se decidi6 que el equipo
MDGGOD fuese controlado igiaalmente en forma autcmStica por este con
trol, para evitar que siguiese produciendo gases en el interv^alo de
parada del equipo que dura aproximadamente 10 minutos. Sin embargo,
esto produce una entrada de corriente instantanea al transformador
que se desconoce el efecto que pueda tener en el mismo a largo plazo.
\
***
DESINFECCION, UTILIZANDO EL MOGGO
***
Esta unidad de desinfecci6n fue instalada primeramente en un pozo
con un gasto de 25 L.p.s., siendo muy elevado para la capacidad '
de la unidad ox i que se instald, e'sto se manifest6 en el residual
de cloro m5x i mo que se alcanz6 e» la red,
el cua I fue de 0.1 ppm.;
aun con e^to, se lograron buenos resultados, ta I y como se m u e s —
tran en el Cuadro
No. 1 I os an^Nsis bacterioI6gicos del agua, an_
tes y despu^s de tratamiento a las 12 hrs. de funcionamiento. Por
otra parte, en este lugar se tuv» problemas de taponami ento de la
membrana y su funcionamiento era de unas 20 hrs., aproximadamente.
El Moggo se cambi6 a otro lugar, donde se t ieneprob lemas de conta_
minaci6n, este pozo tiene un gasto de 12 L.p.s. y 240 Coliformes'
Totales/lOO Ml., en este lugar sc presentaron problemas para la '
des i nf ecc i 6n, \a que la zona es alitnentada por dos pozos, y, el '
agua tratada Mega a una pequena zona, encontrSndose en estos Iugares, res i dua les' de cloro I ibre «le 0.2 p.p.m. y 0 de col'iformes'
Totales/lOO Ml., los resultados st indican en el Cuadro No. 2. En
esta parte el equipo dur6 en funcionamiento nueve dfas, se quit6'
para darIe mantenimiento por presentar fuga.
Actualmente se encuentra instalado en una pequena comunidad, con'
un gasto de 2.7 L.p.s., 632 Coliformes Totales/lOO Ml. y 1 C o l i —
forme JTefcal/lOO Ml.; para 6ptimo funcionamiento del equipo, se
"
instal6 una bomba de ayuda para veneer la presi6n y, como el Venturi es muy fr^gil, £ste fue sustituido por el inyector de un eqyj
po clorador, con Io cual se ha teaido buen funcionamiento.
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DESINFECCION DEL AGUA MED I ANTE EL MOGGO :
La unidad oxi 2 lb. de capacidad es probada en (a salida de un tanque de almacenamiento con un gasto de 17 —
l.p.s., <?sta agua tiene una concentrac i6n bacteriana -de 86 col iforires total es/ 100 Ml y 0 de col iforir.es
fecales/100 Ml.
Este tanque abastece a una poblacidn de 12,000 habitantes.
Se encontro" que el agua con un residual de cloro I ibre'
de 0.2 PPM a la sal ida del tanque I Iega hasta el punto'
ma's alejado de la red de d istr ibuc i6n sin cloro res i
dual, tenie"ndo una el iminaci6n bacteriana del 98 % .
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PROGRAMA DB VIGILANCIA Y MBJORAMIBHTO DB CALIDAD DB
AGUA
FORttULABIO DE IESPECCIOUES EURALES
SISTEMAS DE GBAVEDAD SIN TRATAMIEMTO
Comunidad
Fecha
/
GufaHoja /
/
GUI A PARA EL LLENADO DEL FORMULARIO
1. PLANIFICAR para hacer oor lo menos:
-una visita por ano a ceda comunidad
-y una visita adicional por ano, por cadauna de 18s siguientes condiciones:
-cuenta con un sistema de bombeo
-cuenta con una planta de tratamiento
-tiene un poblacion service de m8s de 500 nab.
2. NOTIFIQUE a la comunidad de su visita con anticipacion
NUNCA hacer mfc que un inspection por dia
3. HAQA su inspeccion y COMPLETE el formulano en presencia de un representante del pueblo
(autoridad deagua). El(los) debe(n) ffrmar abajo.
4. LLENAR el formulario con letra de imprenta
5. CONTESTE todo el formulario.
-para contestar si, marque asi: si ( x ), no ( )
-para contestar no, marque est: si ( ), no ( x )
-cuando haya varias posibilidades, marque la apropiada ( x )
-para numeros, nunca marque ( - ) 6 ( x ), siempre coloque 0 6 el valor correspondiente.
USE los espacios de "Observaciones" y "Esquema Sencillo" para clarificar o poner otra
informacion de importancia
6. Al dia siguiente- complete una couia del formulario para enviar a la BRD-Region Central a fin
demes(amaquina)
- complete dos formularies de informe al pueblo (a maquina) y ENVIELOS (una copia a la BRD*
yunacoplaal pueblo)
(*BRD = Base Regional de DITESA)
Determlnac16n de la Potencta de Cloro en Polvo
1.. Tome una muestra de unos gramos en una bolsa plastica y guardelos en un lugar oscuro, frio y
\ seco hasta el momento del analisis. Siempre haga el analisis antes de las 48 horas.
2. nida 1 g del polvo con la balanza de precision.
3. Disuelvalo en ! litro de agua limpia (destilada si es posible).
3. Tome5mldelasoluci6nenun8pipetayecheloen 1 litro da agua, mezclebien.
4. Chequee la concentracion de cloro total en el agua con el comparador(=x) mg/1
5. Potencia (%) - concentracion (x) x 200
PROGRAMA DE V I G I L A N C I A Y MEJORAMIENTO DE C A L I D A D DE AGUA
, Hoja
Comunidad
Fecha
/
GST-1
/
INSPECCION
Fechade Inspection
Inspeccion hecha por 1
2
DelPVMCA-
/
/
(base)
LUGAR
Comunidad
Distrito
Provlncia
Departamento
aqua ooblacion total No. Usuarios/poblacion servicfe
habs
)
habs
)
habs
)
habs
)
)
habs
habs
habs
If III
Nombre del Barrio del pueblo con servicio de
si( ),no(
si( ).no(
si( ),no(
s i ( ),no(
si ( ).no(
TOTALES
Codlgo
GENERALIDADES
Numero de horas de viaje desde la base del PVMCA a la comunidad=
distancia=
por: carro( ) , t r e n ( ),moto( ).caballo( ),otro=
horas
Km
Ministerio de Salud: Puesto ( ),Centro( ), Botiquin Comunal ( ),otro=
que distanciadel centro del pueblo
Km,
Medico( ),Enfermera( ),Sanit8rio( ),Promotor(
Hay una escuela en 18 comunidad? si ( ), no ( )
Hay luz en la comunidad? si ( ), no ( )
FIRM AS
Firmas de los Inspectores del Equipode Vigilancia:-
1
2
NOMBRE
NOMBRE
CARGO
CARGO...
Firm8s de los representantes del pueblo
1
2
NOMBRE
NOMBRE
CARGO
CARGO
horas de viaje
),otro =
PROGRAMA DE VI6ILANCIA Y MEJORAMIENTO DE CALIDAD DE AGUA
Hoja GST-J
Comunidad
Fecha
/
/
FUENTE DE AGUA
Tipode fu9nte: manantial captado directo ( ), lago/laguna( ),pozo( ), no ( ),riachuelo ( ),
quebrada ( ), canal de regadio ( ), otro =
Nombredelafuente
Contaminacionde lafuentedeagua: mineria( ), letrinas( ), basura( ), ganado( ),
lavanderia( ), animates ( ),humanos( ),otros =
Cantidad de agua existente en la fuente =
litros por segundo (Ver Hoja 2)
es la cantidad usual (todo el dia y todo el ano): si ( ),no( ). (si no, EXPLIQUEen
Observaclones)
avec8s, no hay agua: si ( ),no( )
-cuantos di8S al ano
Cuando
-cuantas horas al dia
Cuando
Se utilize para irrigacion: si ( ),no( )
La fuente esta ubicada en terrenos de
Observnciones
CAPTACION
Manantial captado en directo v proteqido si ( ),no( )
Estasellado? si ( ),no( ),otienet8paremovible: si ( ),no( )
Esta" seguro(bajo Have)? si ( ),no( )
-con aletas: si ( ), no( )
-consello (losa)de protection atras: si ( ),no( )
-con tapa sanitaria: si ( ), no ( )
-la protection esefectiva: si ( ),no( ); (si no.CXPLIQUC en Observaciones)
-con cerco 0 muro: si ( ),no( ) que puede evitar el ingresodeanimales: s i ( ),no( )
-con canaleta de desvio para agues superficiales: si ( ),no( )
-cuantos metros de la captation
metros
-que puede prevenir el ingreso de lss aguas: si ( ), no ( )
Cantidad de aqua que inqresa al sistema =
litros por segundo
Puntodeaforo =
Existe control de flulo: s f ( ),no( )
'
-por vertedero triangular: si ( ) , n o ( )de
°(angulo)
-por vertedero rectangular: si ( ) , n o ( )
-de que materiales
_
Existe un medio para evacuar el exceso de fluio: si ( ), no ( )
-por tuberia de rebose vertical ( ) de
pulgadasde dISmetro
-u horizontal ( )de
pulgadas de diametro
-0 aliviadero ( ) de
centimetros de largo
-se puede evacuar el 10055 del ingreso: si ( ), no ( )
Existe una tuberia removiple para limpieza: si ( ),no( ) 0 valvule de purga: si ( ),no( )
Alasalida: -existe unacanastilla: si ( ), no ( )omalladeprotecci6n: s i ( ),no(
)
-existe un8 valvule de control desalida( )
Observaciones
Acetones Requeridas
PROGRAMA DE VIGILANCIA Y MEJORAMIENTO DE CALIDAD DE AGUA
Hoja 6ST-5
Comunidad
Fecha
/
/
RESERVORIO
Caja de valvules:
Esta sellada: si ( ),no( ) o tiene taps: si ( ),no( );segurobajollavesi ( ),no( )
hay problemas con las valvules: si ( ),no( )(ESPECIFICARLOSenObservaciones)
puedeevacuarse.aguade la cajade valvules: si ( ),no( ). {por unhuecoal fondo( )opor
fondo de grava ( ) o por otro ruta=
}
tiene rebose si ( ),no( ); tiene valvule delimpieza si ( ),no( )
Boca de inspection:
Existe: si ( ), no ( ); protegida por tepa sanitaria: si ( ), no ( )
Esta sell8da con concreto: si ( ),no( ),osegurobajo Have: si ( ),no( )
El Tanoue
Tiene ventilador(es): si ( ),no( ); con boca hacia abajo: si ( ),no( ) y protegido por malla:
s i ( ),no( )
Puede entrar el aqua de lluvla: si ( ),no( ) o de la superficie: si ( ),no( )
Tiene fuoas (el tanque): si ( ), no ( )
Dimensiones Interiores: Largo=
m,ancho=
m, diemetro=
m.alturadepiso
a rebose =
m, Volumen =
m3
Observsciones
Accioncg Requeridas
LINEA DE ADUCCION ( L o n g i t u d del Reservorio al Pueblo)
Longitudaproximada =
Km
Diametro =
pulgadas
Material: PYC ( ), FoOo ( ), Eterni* ( ), otro =
Hay fuqas: si ( ) , n o ( ); cuantas
(ANOTARLAS en el esquema sencillo)
Otros problemas: si ( ), no ( ); cuales
(ANOTARLOS tambien)
Cuent8 con caia(s) rompe presion: si ( ), no ( ); cuantas
(ANOTARLAS)
-cuenta con tapa sanitaria: si ( ), no ( )
-cuenta con rebose: si ( ) no ( ):
-portubo( )oaliviadero( );8decuadopar8evacuartodo el rebose: si ( ),no( )
-protegido (p.e. por malla) contra el ingreso de cuerpos extranos: si ( ),no( )
-se saca agua de la(s) caja(s): si ( ), no ( ):
-paraconsumohumano( )oparaanim8les( ) o para irrigation ( )
Cuenta con valvula de aire: si ( ), no ( )Cuantas
(ANOTARLAS en el esquema)
Cuenta con valvula de purge: si ( ), no ( ), cuantas
(ANOTARLAS en el esquema)
Observsciones (ANOTAR si los componentes no funcionan)
Acciones Requeridas
PROGRAMA DE VIGILANCIA Y MEJORAMIENTO DE CALIDAD DE AGUA
Hoja 6b'-?
MUESTREAR:siempre
-captacion (cada una)
-reservorio(cadauno)
-despues de cada unidad de tratamiento
-antes y despues de clorecion (cuando hay)
-en la red
- Piletas Publicas, 5 6 20X unidades (el mayor)
- Conexiones Domiciliarias: entre 5 y 10X de ellos (tomarlos en V5
cruces prlncipales y fines de la red)
edemas, a su discrecion -fuente usada
-otras fuentes
-caja de reunion
-C8J8S rompe presiones
-mas lugares en la red
VOLUMENES para a n a l i z a r
Seleccionar los volumenes tomando en cuenta la parte del sistema y/o estado de contam inacion.
Tipo de muestra
Canal deRegadio.Rfos
Lagos remotos, riachuelos remotos, quebradas
P020S protegldos, m8nantiales protegldos
Aguas parcialmente tratadas
Aguas tratadas, reservorios, redes de distribucion
Volumen para analizar
Posible
Normalmente
50ml
10ml
100,10ml
50ml
50ml
100ml
0.1 6 1 6 100ml
10 6 50ml
50ml
100ml
Resultados de Analisis:
FUENTE do i a J H o r a J A a p e ^
iSaboridez i l t b r e i t o t a l : fiC
MUESTRA.
: C o l o r : UT : m 9f\ : m 9 / j :'
N;
•iuctiv
jf«?.?A...
!uS/cm" 'i/jPOfn.l
PROGRAMA DE VIGILANCIA Y MEJORAMIENTO DE CALIDAD DE AGUA
INSPECCIONAR -las casas donde se hace analisis
-y la mitad de este numero de ellas sin agua
Inspeccl6n DomJcJIfarla (con Agua) (usar lasmismsscases del analisis de agua)
No
Disposicion de Basura
Proximidad de Animates domesticos
alimento entierro querns boter cerca botar lejos ;n huerlo al lado aparte no tiener
que
animales
a la casa dela casa ?n la casa iela casa
animates animales
1...
2...
3...
A...
5...
6...
7...
8...
9...
10.
11.
12.
(
Inspeccfdn Casera (Sin Agua)
firoxUnlM dt Animates oomlslicos
No Di'sposfcioo C*e Basura
sllmento enllerro !)uema joUr cerct txjlar lejos en huerto si lado iparle no tienen que"
animates animales
snlmales
l l t C I M d«la casa en U CMS* ilia casa
.elrlna
seusa lozade
seve
xncrelo laps limpi
lx\i\e lipo
1
2
3
4..
5..
6..
7
8
q
10
11
12
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: : : :
Hoja GST-9
Letrina
Existe Tipo
S8US8 lozade
con seve
concreto tape limpia
>
•
Recoleccion personal
Cfopsearefowclgwa.
iPilcta \ ozo menentialirloo psmidh buehte
pui6i
buevolumen
recipiente pare Do^xfctoquarda
Public*
chueli cislernjpviajesdiarfdloshace
CapacidadjQuSmaleriej] cootapajcongrifo
porviaje(lilros) recoleccion