Environmental Letters
ISSN: 0013-9300 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/lesa17
Prevention of Sewage Pollution by Stabilization Ponds Sewage Pollution & Stabilization Ponds J. S. S. Lakshminarayana To cite this article: J. S. S. Lakshminarayana (1975) Prevention of Sewage Pollution by Stabilization Ponds Sewage Pollution & Stabilization Ponds, Environmental Letters, 8:2, 121-134, DOI: 10.1080/00139307509437426 To link to this article: http://dx.doi.org/10.1080/00139307509437426
Published online: 02 Sep 2009.
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Date: 06 November 2015, At: 23:21
ENVIRONMENTAL LETTERS, 8(2), 121-134 (1975)
PREVENTION O F SEWAGE POLLUTION BY
STABILIZATION PONDS SEWAGE POLLUTION & STABILIZATION PONDS
J.S.S.
Lakshminarayana
Department o f b i o l o g y U n i v e r s i t y o f Moncton Moncton, N.B.
Downloaded by [Universite Laval] at 23:21 06 November 2015
Abstract Water i s p o l l u t e d when it c o n s t i t u t e s a h e a l t h h a z a r d or.when i t s u s e f u l n e s s i s impaired. The major s o u r c e s o f w a t e r p o l l u t i o n are m u n i c i p a l , m a n u f a c t u r i n g , mining, steam, e l e c t r i c power, c o o l i n g and a g r i c u l t u r a l . . M u n i c i p a l o r sewage p o l l u t i o n forms a g r e a t e r p a r t o f t h e man's a c t i v i t y and it i s t h e immediate need o f even s m a l l e r communities o f t o d a y t o combat sewage p o l l u t i o n . I t i s n e e d l e s s t o stress t h a t i f a n economic b a l a n c e o f t h e many v a r i e d serv i c e s which a stream o r a body o f water i s c a l l e d upon t o r e n d e r i s b a l a n c e d and t a k e n i n t o c o n s i d e r a t i o n o n e c o u l d t h i n k of e n d i n g up i n a w i s e management programme. In o r d e r t o e l i m i n a t e t h e e x i s t i n g water p o l l u t i o n a l l e v e l s o f t h e n a t u r a l water o n e h a s t o t h i n k o f p r e v e n t i v e and t r e a t m e n t methods. Of the v a r i o u s c o n v e n t i o n a l and non-conventional methods o f sewage t r e a t m e n t known t o d a y , i n I n d i a , where t h e economic problems are complex, the w a s t e s t a b i l i z a t i o n ponds have become p o p u l a r o v e r t h e l a s t t w o d e c a d e s t o l e t P u b l i c . H e a l t h E n g i n e e r s u s e them w i t h c o n f i d e n c e as a s i m p l e and r e l i a b l e means o f t r e a t m e n t o f sewage and c e r t a i n i n d u s t r i a l wastes, a t a f r a c t i o n of t h e c o s t of conventional waste t r e a t m e n t p l a n t s used h i t h e r t o . A waste s t a b i l i z a t i o n pond makes u s e o f n a t u r a l p u r i f i c a t i o n p r o c e s s e s i n v o l v e d i n a n ecosystem t h r o u g h t h e r e g u l a t i n g o f s u c h p r o c e s s e s . The term "waste s t a b i l i z a t i o n pond" i n i t s s i m p l e s t form i s a p p l i e d t o a body of w a t e r , a r t i f i c i a l o r n a t u r a l , employed w i t h t h e i n t e n t i o n o f ret a i n i n g sewage o r o r g a n i c w a s t e w a t e r s u n t i l t h e w a s t e s are r e n d e r e d s t a b l e and i n o f f e n s i v e f o r d i s c h a r g e i n t o r e c e i v i n g waters o r o n l a n d , t h r o u g h p h y s i c a l , c h e m i c a l
121 Copyright 0 1975 by hlarcel Dekker. Inc. All Rights Reserved. Neither this work nor any part may be reproduced or transmittd in any form or by any means, electronic or mechanical. including photocopying, microfilming. and recording, or by any infcrmation storage and retrieval system, without permission in writing from the publisher.
LAKSHMINARAYANA
and b i o l o g i c a l p r o c e s s e s commonly r e f e r r e d t o as "self-pur i f i c a t i o n " and i n v o l v i n g t h e s y m b i o t i c a c t i o n of a l g a e and b a c t e r i a under t h e i n f l u e n c e o f s u n l i g h t and a i r . Organic m a t t e r c o n t a i n e d i n t h e w a s t e i s s t a b i l i z e d and c o n v e r t e d i n t h e pond i n t o more s t a b l e matter i n t h e form o f a l g a l c e l l s which f i n d t h e i r way i n t o t h e e f f l u e n t and hence t h e term " s t a b i l i z a t i o n - pond''. T h i s p a p e r p r e s e n t s t h e d e s i g n , c o n s t r u c t i o n , o p e r a t i o n and maintenance c o n s i d e r a t i o n s f o r s t a b i l i z a t i o n ponds under I n d i a n c o n d i t i o n s . The s t a b i l i z a t i o n ponds w e r e found t o b e t h e c h e a p e s t method o u t of a l l o t h e r t r e a t m e n t methods as long a s cost o f l a n d i s n o t more t h a n R s 55,000 p e r acre. The c a p i t a l c o s t , i n c l u d i n g l a n d , works o u t t o b e v a r y i n g from R s 8 . 8 t o 15.7 p e r p e r s o n o r $1.05 t o 2 . 0 p e r person.
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Introduction Today man and h i s environment i s f a c e d w i t h a n e c o l o g i c a l c r i s i s which i s a r e s u l t o f human a c t i v i t i e s o n man's environment, o n man h i m s e l f and on human s o c i e t y . The g r e a t e s t havoc wrought by t h e p r e s s u r e s of p o p u l a t i o n h a s been t h e damage t o humanity and as a r e s u l t of which t h e slums o f t h e immediate f u t u r e may d e s t r o y e v e r y t h i n g beaut i f u l o r p o t e n t i a l l y b e a u t i f u l i n t h e i r p a t h by r e p l a c i n g housing t o m i l l i o n s who w i l l r e q u i r e sewers, t h e g a s o l i n e s t a t i o n s , shopping c e n t r e s , h o t dog f t a n d s , d r i v e - i n s , and o t h e r desecrations of t h e landscape. I f development and ecology b e r e c o n c i l e d i t i s p o s s i b l e f o r t h e e c o l o g i s t s and e n g i n e e r s t o d e m o n s t r a t e environmental f e a s i b i l i t y as w e l l as s t r u c t u r a l and economic f e a s i b i l i t y . The combined e f f o r t s o f e c o l o g i s t s and e n g i n e e r s w i l l u l t i m a t e l y l e a d t o new technology which c a n h e l p t h e s o c i e t y and t h e r e b y s a v i n g o u r world from p o l l u t i o n , o v e r p o p u l a t i o n , s t a r v a t i o n , r e s o u r c e development a n d . o t h e r c h a l l e n g e s . ' Man's impact o n environment h a s r e s u l t e d i n i t s d e t e r i o r a t i o n . The environment comprises of a i r , w a t e r and s o i l . D e t e r i o r a t i o n o f t h e environment i s n o t h i n g b u t p o l l u t i o n which i s a n end-product o f a r t i f i c i a l l y induced deteriorat i o n by man's a c t i v i t i e s o r a b u s e of t h e environment. T h i s paper is a n attempt t o p r e s e n t a s o l u t i o n f o r t h e prevention of sewage, p o l l u t i o n by s t a b i l i z a t i o n ponds whose knowledge i s a p r o d u c t o f t h e combined e f f o r t s o f t h e e c o l o g i s t s and engineers.
Water P o l l u t i o n S i t u a t i o n i n I n d i a
The s u r f a c e water r e s o u r c e s of I n d i a have been estimated a t a b o u t 1, 356 m i l l i o n acre f e e t and t h e e n t i r e q u a n t i t y i s d e r i v e d from p r e c i p i t a t i o n . There i s a c o n s i d e r a b l e v a r i a t i o n i n t h e a v a i l a b l e s u r f a c e water r e s o u r c e s i n d i f f e r e n t p a r t s of t h e c o u n t r y depending o n t h e v a r y i n g p r e c i p i t a t i o n from p l a c e t o p l a c e . Out o f t h i s p r e c i p i t a t i o n o n l y 450 m i l l i o n acre f e e t o f s u r f a c e water c a n be a v a i l a b l e f o r b e n e f i c i a l
122
S N G E POLLUTION AND STABILIZATION PONDS
purposes w h i l e t h e rest i s n o t a v a i l a b l e due t o v a r i o u s p h y s i o g r a p h i c , g e o l o g i c a l and c l i m a t i c f a c t o r s .
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Ground water r e s o u r c e s form a n o t h e r major s o u r c e o f w a t e r b u t t h e p o t e n t i a l i t i e s o f I n d i a n ground w a t e r r e s o u r ces are y e t t o b e e x p l o r e d . However, t h e ground w a t e r r e s o u r c e s a l s o g e t p o l l u t e d due t o environmental p o l l u t i o n , as a r e s u l t o f which t h e community water s u p p l i e s w i l l no l o n g e r remain s a f e from p o l l u t i o n . A f t e r independence and t h e o n s e t o f u r b a n i z a t i o n and i n d u s t r i a l i z a t i o n a n i n c r e a s i n g number o f water s u p p l y and sewerage systems and water t r e a t m e n t p l a n t s a r e under implementation. But t h e p r o v i s i o n f o r sewage t r e a t m e n t p l a n t s had n o t k e p t pace w i t h t h e development o f water s u p p l i e s . A s a r e s u l t of which a n i n c r e a s i n g amount o f s u l l a g e and i n d u s t r i a l wastes are e n t e r i n g t h e n a t u r a l w a t e r s and p o l l u t i n g t h e n . The r a p i d growth o f p o p u l a t i o n of I n d i a added a n o t h e r dimension t o t h e p o l l u t i o n problem and p r e v e n t i o n o f p o l l u t i o n of n a t u r a l waters has become an immediate n e c e s s i t y . Table 1 and 2 r e v e a l c h a r a c t e r i z a t i o n o f c e r t a i n I n d i a n i n d u s t r i a l wastes which f u r t h e r s t r e s s e d t h e need o f adopt i n g measures t o r e d u c e p o l l u t i o n l o a d s . S t a b i l i z a t i o n Ponds During t h e l a s t decade s e v e r a l p a p e r s were p u b l i s h e d on t h e u s e o f o x i d a t i o n ponds o r h o l d i n g lagoons o r s t a b i l i z a t i o n l a g o o n s o r s t a b i l i z a t i o n ponds. A w a s t e s t a b i l i z a t i o n pond i n i t s s i m p l e s t form i s a p p l i e d t o a body of w a t e r , a r t i f i c i a l o r n a t u r a l , employed w i t h t h e i n t e n t i o n o f ret a i n i n g sewage o r o r g a n i c waste w a t e r s u n t i l t h e w a s t e s are r e n d e r e d s t a b l e and i n o f f e n s i v e f o r d i s c h a r g e i n t o r e c e i v i n g waters o r on l a n d , t h r o u g h p h y s i c a l , chemical and b i o l o g i c a l p r o c e s s e s commonly r e f e r r e d t o as " s e l f - p u r i f i c a t i o n " and i n v o l v i n g t h e s y m b i o t i c a c t i o n o f a l g a e and b a c t e r i a under t h e i n f l u e n c e o f s u n l i g h t and a i r . Organic m a t t e r c o n t a i n e d i n t h e waste i s s t a b i l i z e d and c o n v e r t e d i n t h e pond i n t o more s t a b l e matter i n t h e form of a l g a e c e l l s which f i n d t h e i r way i n t o t h e e f f l u e n t and hence t h e term ' S t a b i l i z a t i o n Pond' The C.P.H.E.R.I., C e n t r a l P u b l i c H e a l t h Engineering Research I n s t i t u t e , I n d i a , developed t h e know-how o f s t a b i l i z a t i o n ponds under I n d i a n c o n d i t i o n s . A t p r e s e n t , f o u r d i f f e r e n t methods o f sewage t r e a t m e n t are p o p u l a r i n I n d i a . They are m e c h a n i c a l l y o p e r a t e d l a g o o n s , Pasveer-type o x i d a t i o n d i t c h c o n v e n t i o n a l t r e a t m e n t and w a s t e s t a b i l i z a t i o n ponds. Each method i s c a p a b l e o f g i v i n g a w e l l t r e a t e d f i n a l e f f l u e n t and each method h a s i t s p r o s and cons. S t a b i l i z a t i o n ponds need more l a n d , o x i d a t i o n d i t c h e s need more power, w h i l e c o n v e n t i o n a l t r e a t m e n t methods l i k e t r i c k l i n g f i l t e r or a c t i v a t e d s l u d g e are h i g h i n c a p i t a l c o s t . I n d i a n s t u d i e s ? have shown t h a t from a s c r u t i n y of 7 2 p l a n t s t h a t a s many as 4 3 p e r c e n t of t h e m were o f 0.5 mgd c a p a c i t y o r less: F o r t h e s e small s i z e p l a n t s , it w a s f u r t h e r n o t e d , the c o n v e n t i o n a l method o f t r e a t m e n t i s most uneconomic to a d o p t ( c f . T a b l e 3.).
.
123
TABLE 1. C h a r a c t e r i s t i c s o f D i f f e r e n t I n d u s t r i a l Wastes
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ISSN: 0013-9300 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/lesa17
Prevention of Sewage Pollution by Stabilization Ponds Sewage Pollution & Stabilization Ponds J. S. S. Lakshminarayana To cite this article: J. S. S. Lakshminarayana (1975) Prevention of Sewage Pollution by Stabilization Ponds Sewage Pollution & Stabilization Ponds, Environmental Letters, 8:2, 121-134, DOI: 10.1080/00139307509437426 To link to this article: http://dx.doi.org/10.1080/00139307509437426
Published online: 02 Sep 2009.
Submit your article to this journal
Article views: 3
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=2esa20 Download by: [Universite Laval]
Date: 06 November 2015, At: 23:21
ENVIRONMENTAL LETTERS, 8(2), 121-134 (1975)
PREVENTION O F SEWAGE POLLUTION BY
STABILIZATION PONDS SEWAGE POLLUTION & STABILIZATION PONDS
J.S.S.
Lakshminarayana
Department o f b i o l o g y U n i v e r s i t y o f Moncton Moncton, N.B.
Downloaded by [Universite Laval] at 23:21 06 November 2015
Abstract Water i s p o l l u t e d when it c o n s t i t u t e s a h e a l t h h a z a r d or.when i t s u s e f u l n e s s i s impaired. The major s o u r c e s o f w a t e r p o l l u t i o n are m u n i c i p a l , m a n u f a c t u r i n g , mining, steam, e l e c t r i c power, c o o l i n g and a g r i c u l t u r a l . . M u n i c i p a l o r sewage p o l l u t i o n forms a g r e a t e r p a r t o f t h e man's a c t i v i t y and it i s t h e immediate need o f even s m a l l e r communities o f t o d a y t o combat sewage p o l l u t i o n . I t i s n e e d l e s s t o stress t h a t i f a n economic b a l a n c e o f t h e many v a r i e d serv i c e s which a stream o r a body o f water i s c a l l e d upon t o r e n d e r i s b a l a n c e d and t a k e n i n t o c o n s i d e r a t i o n o n e c o u l d t h i n k of e n d i n g up i n a w i s e management programme. In o r d e r t o e l i m i n a t e t h e e x i s t i n g water p o l l u t i o n a l l e v e l s o f t h e n a t u r a l water o n e h a s t o t h i n k o f p r e v e n t i v e and t r e a t m e n t methods. Of the v a r i o u s c o n v e n t i o n a l and non-conventional methods o f sewage t r e a t m e n t known t o d a y , i n I n d i a , where t h e economic problems are complex, the w a s t e s t a b i l i z a t i o n ponds have become p o p u l a r o v e r t h e l a s t t w o d e c a d e s t o l e t P u b l i c . H e a l t h E n g i n e e r s u s e them w i t h c o n f i d e n c e as a s i m p l e and r e l i a b l e means o f t r e a t m e n t o f sewage and c e r t a i n i n d u s t r i a l wastes, a t a f r a c t i o n of t h e c o s t of conventional waste t r e a t m e n t p l a n t s used h i t h e r t o . A waste s t a b i l i z a t i o n pond makes u s e o f n a t u r a l p u r i f i c a t i o n p r o c e s s e s i n v o l v e d i n a n ecosystem t h r o u g h t h e r e g u l a t i n g o f s u c h p r o c e s s e s . The term "waste s t a b i l i z a t i o n pond" i n i t s s i m p l e s t form i s a p p l i e d t o a body of w a t e r , a r t i f i c i a l o r n a t u r a l , employed w i t h t h e i n t e n t i o n o f ret a i n i n g sewage o r o r g a n i c w a s t e w a t e r s u n t i l t h e w a s t e s are r e n d e r e d s t a b l e and i n o f f e n s i v e f o r d i s c h a r g e i n t o r e c e i v i n g waters o r o n l a n d , t h r o u g h p h y s i c a l , c h e m i c a l
121 Copyright 0 1975 by hlarcel Dekker. Inc. All Rights Reserved. Neither this work nor any part may be reproduced or transmittd in any form or by any means, electronic or mechanical. including photocopying, microfilming. and recording, or by any infcrmation storage and retrieval system, without permission in writing from the publisher.
LAKSHMINARAYANA
and b i o l o g i c a l p r o c e s s e s commonly r e f e r r e d t o as "self-pur i f i c a t i o n " and i n v o l v i n g t h e s y m b i o t i c a c t i o n of a l g a e and b a c t e r i a under t h e i n f l u e n c e o f s u n l i g h t and a i r . Organic m a t t e r c o n t a i n e d i n t h e w a s t e i s s t a b i l i z e d and c o n v e r t e d i n t h e pond i n t o more s t a b l e matter i n t h e form o f a l g a l c e l l s which f i n d t h e i r way i n t o t h e e f f l u e n t and hence t h e term " s t a b i l i z a t i o n - pond''. T h i s p a p e r p r e s e n t s t h e d e s i g n , c o n s t r u c t i o n , o p e r a t i o n and maintenance c o n s i d e r a t i o n s f o r s t a b i l i z a t i o n ponds under I n d i a n c o n d i t i o n s . The s t a b i l i z a t i o n ponds w e r e found t o b e t h e c h e a p e s t method o u t of a l l o t h e r t r e a t m e n t methods as long a s cost o f l a n d i s n o t more t h a n R s 55,000 p e r acre. The c a p i t a l c o s t , i n c l u d i n g l a n d , works o u t t o b e v a r y i n g from R s 8 . 8 t o 15.7 p e r p e r s o n o r $1.05 t o 2 . 0 p e r person.
Downloaded by [Universite Laval] at 23:21 06 November 2015
Introduction Today man and h i s environment i s f a c e d w i t h a n e c o l o g i c a l c r i s i s which i s a r e s u l t o f human a c t i v i t i e s o n man's environment, o n man h i m s e l f and on human s o c i e t y . The g r e a t e s t havoc wrought by t h e p r e s s u r e s of p o p u l a t i o n h a s been t h e damage t o humanity and as a r e s u l t of which t h e slums o f t h e immediate f u t u r e may d e s t r o y e v e r y t h i n g beaut i f u l o r p o t e n t i a l l y b e a u t i f u l i n t h e i r p a t h by r e p l a c i n g housing t o m i l l i o n s who w i l l r e q u i r e sewers, t h e g a s o l i n e s t a t i o n s , shopping c e n t r e s , h o t dog f t a n d s , d r i v e - i n s , and o t h e r desecrations of t h e landscape. I f development and ecology b e r e c o n c i l e d i t i s p o s s i b l e f o r t h e e c o l o g i s t s and e n g i n e e r s t o d e m o n s t r a t e environmental f e a s i b i l i t y as w e l l as s t r u c t u r a l and economic f e a s i b i l i t y . The combined e f f o r t s o f e c o l o g i s t s and e n g i n e e r s w i l l u l t i m a t e l y l e a d t o new technology which c a n h e l p t h e s o c i e t y and t h e r e b y s a v i n g o u r world from p o l l u t i o n , o v e r p o p u l a t i o n , s t a r v a t i o n , r e s o u r c e development a n d . o t h e r c h a l l e n g e s . ' Man's impact o n environment h a s r e s u l t e d i n i t s d e t e r i o r a t i o n . The environment comprises of a i r , w a t e r and s o i l . D e t e r i o r a t i o n o f t h e environment i s n o t h i n g b u t p o l l u t i o n which i s a n end-product o f a r t i f i c i a l l y induced deteriorat i o n by man's a c t i v i t i e s o r a b u s e of t h e environment. T h i s paper is a n attempt t o p r e s e n t a s o l u t i o n f o r t h e prevention of sewage, p o l l u t i o n by s t a b i l i z a t i o n ponds whose knowledge i s a p r o d u c t o f t h e combined e f f o r t s o f t h e e c o l o g i s t s and engineers.
Water P o l l u t i o n S i t u a t i o n i n I n d i a
The s u r f a c e water r e s o u r c e s of I n d i a have been estimated a t a b o u t 1, 356 m i l l i o n acre f e e t and t h e e n t i r e q u a n t i t y i s d e r i v e d from p r e c i p i t a t i o n . There i s a c o n s i d e r a b l e v a r i a t i o n i n t h e a v a i l a b l e s u r f a c e water r e s o u r c e s i n d i f f e r e n t p a r t s of t h e c o u n t r y depending o n t h e v a r y i n g p r e c i p i t a t i o n from p l a c e t o p l a c e . Out o f t h i s p r e c i p i t a t i o n o n l y 450 m i l l i o n acre f e e t o f s u r f a c e water c a n be a v a i l a b l e f o r b e n e f i c i a l
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S N G E POLLUTION AND STABILIZATION PONDS
purposes w h i l e t h e rest i s n o t a v a i l a b l e due t o v a r i o u s p h y s i o g r a p h i c , g e o l o g i c a l and c l i m a t i c f a c t o r s .
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Ground water r e s o u r c e s form a n o t h e r major s o u r c e o f w a t e r b u t t h e p o t e n t i a l i t i e s o f I n d i a n ground w a t e r r e s o u r ces are y e t t o b e e x p l o r e d . However, t h e ground w a t e r r e s o u r c e s a l s o g e t p o l l u t e d due t o environmental p o l l u t i o n , as a r e s u l t o f which t h e community water s u p p l i e s w i l l no l o n g e r remain s a f e from p o l l u t i o n . A f t e r independence and t h e o n s e t o f u r b a n i z a t i o n and i n d u s t r i a l i z a t i o n a n i n c r e a s i n g number o f water s u p p l y and sewerage systems and water t r e a t m e n t p l a n t s a r e under implementation. But t h e p r o v i s i o n f o r sewage t r e a t m e n t p l a n t s had n o t k e p t pace w i t h t h e development o f water s u p p l i e s . A s a r e s u l t of which a n i n c r e a s i n g amount o f s u l l a g e and i n d u s t r i a l wastes are e n t e r i n g t h e n a t u r a l w a t e r s and p o l l u t i n g t h e n . The r a p i d growth o f p o p u l a t i o n of I n d i a added a n o t h e r dimension t o t h e p o l l u t i o n problem and p r e v e n t i o n o f p o l l u t i o n of n a t u r a l waters has become an immediate n e c e s s i t y . Table 1 and 2 r e v e a l c h a r a c t e r i z a t i o n o f c e r t a i n I n d i a n i n d u s t r i a l wastes which f u r t h e r s t r e s s e d t h e need o f adopt i n g measures t o r e d u c e p o l l u t i o n l o a d s . S t a b i l i z a t i o n Ponds During t h e l a s t decade s e v e r a l p a p e r s were p u b l i s h e d on t h e u s e o f o x i d a t i o n ponds o r h o l d i n g lagoons o r s t a b i l i z a t i o n l a g o o n s o r s t a b i l i z a t i o n ponds. A w a s t e s t a b i l i z a t i o n pond i n i t s s i m p l e s t form i s a p p l i e d t o a body of w a t e r , a r t i f i c i a l o r n a t u r a l , employed w i t h t h e i n t e n t i o n o f ret a i n i n g sewage o r o r g a n i c waste w a t e r s u n t i l t h e w a s t e s are r e n d e r e d s t a b l e and i n o f f e n s i v e f o r d i s c h a r g e i n t o r e c e i v i n g waters o r on l a n d , t h r o u g h p h y s i c a l , chemical and b i o l o g i c a l p r o c e s s e s commonly r e f e r r e d t o as " s e l f - p u r i f i c a t i o n " and i n v o l v i n g t h e s y m b i o t i c a c t i o n o f a l g a e and b a c t e r i a under t h e i n f l u e n c e o f s u n l i g h t and a i r . Organic m a t t e r c o n t a i n e d i n t h e waste i s s t a b i l i z e d and c o n v e r t e d i n t h e pond i n t o more s t a b l e matter i n t h e form of a l g a e c e l l s which f i n d t h e i r way i n t o t h e e f f l u e n t and hence t h e term ' S t a b i l i z a t i o n Pond' The C.P.H.E.R.I., C e n t r a l P u b l i c H e a l t h Engineering Research I n s t i t u t e , I n d i a , developed t h e know-how o f s t a b i l i z a t i o n ponds under I n d i a n c o n d i t i o n s . A t p r e s e n t , f o u r d i f f e r e n t methods o f sewage t r e a t m e n t are p o p u l a r i n I n d i a . They are m e c h a n i c a l l y o p e r a t e d l a g o o n s , Pasveer-type o x i d a t i o n d i t c h c o n v e n t i o n a l t r e a t m e n t and w a s t e s t a b i l i z a t i o n ponds. Each method i s c a p a b l e o f g i v i n g a w e l l t r e a t e d f i n a l e f f l u e n t and each method h a s i t s p r o s and cons. S t a b i l i z a t i o n ponds need more l a n d , o x i d a t i o n d i t c h e s need more power, w h i l e c o n v e n t i o n a l t r e a t m e n t methods l i k e t r i c k l i n g f i l t e r or a c t i v a t e d s l u d g e are h i g h i n c a p i t a l c o s t . I n d i a n s t u d i e s ? have shown t h a t from a s c r u t i n y of 7 2 p l a n t s t h a t a s many as 4 3 p e r c e n t of t h e m were o f 0.5 mgd c a p a c i t y o r less: F o r t h e s e small s i z e p l a n t s , it w a s f u r t h e r n o t e d , the c o n v e n t i o n a l method o f t r e a t m e n t i s most uneconomic to a d o p t ( c f . T a b l e 3.).
.
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TABLE 1. C h a r a c t e r i s t i c s o f D i f f e r e n t I n d u s t r i a l Wastes
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