Chiang 1986 Aquacultural-Engineering

7/28/2019 Chiang 1986 Aquacultural-Engineering

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Aquacultural Engineering 5 ( 1 9 8 6 i 3 0 1 - 3 1 2

S t u d y o f T r e a t m e n t a n d R e u s e o f A q u a c u i t u ra lW a s t e w a t e r in T a iw a n

H. C. ChiangDivision o f L and R eclamation. Agricultural Engineering Research Center. Taoyu an.Taiwan, ROC

andJ.C. Le e

Fisheries Depa rtment, Cou ncil of A griculture, Executive Yu an. 3 7 Nan hai Road.Taipei. Taiwan, RO C

A B S T R A C TLim i t ed f r e s h w a te r r e s o u rces h a ve b een t h e m a jo r co n s t ra in t o n a q u a -cu l tura l dev e lop m ent in Ta iwan , as farm ing prac t ices have gradua l lybec om e in tens i fi ed in recen t years'. Re use o f w as tewater f ro m aqua-cu l tura l sys tems i s there fore an in tpor tan t i s sue in aquacu l ture eng i -twering.

A pi lo t wa ter recirculat ion sys tem was con structe d at W ttshat ttot tFreshwater F ish Cul ture Dem ons tr a t ion Cen ter by the Ta iwat tF isher ies Bureau . I t s e f f ec t iveness was eva lua ted and compared wi thlabora to O' treatmen t . Tire resul ts indica ted that m os t o f the part iclesi t t pond water co t t /d t in t be removed by the se t t l ing procedure aslaboratory s tudie s h ad sho wn . Ttre gravel f i l ter uni t was not suff ic iett t toimprov e water qua li~" to the s tan dard o f b io log ica l trea tmen t . B io log i-ca l ca r b o n o x id a t io n a n d n i tr if ica ti o n s h o u M b e imp r o ved a n d f i tr t h e r#zcorp orated in th is sys tem.

I N T R O D U C T I O NT h e r a p id d e v e l o p m e n t o f a q u a c u l tu r e in T a i w a n d u r i n g th e la std e c a d e h a s b e e n m a i n l y d u e t o t h e i n te n s i f ic a t i o n o f fa r m i n g p ra c t ic e s ,

3 0 1


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3 0 2 H . C . C h i a n g . J . C L e ee s p e c i a l l y i n e e l a n d s h r i m p c u l t u r e . T h e c a r r y i n g c a p a c i t y o f a n e e lp o n d c a n b e g r e a t l y i n c r e a s e d i f w a t e r r u n n i n g t h r o u g h is p r o v i d e d .H o w e v e r , t h i s p r a c t i c e h a s c a u s e d s e r i o u s p r o b l e m s i n s o m e a r e a s i nT a i w a n . A c c o r d i n g t o a s u r v e y m a d e b y t h e T a i w a n P r o v i n c i a l Wa t e rC o n s e r v a n c y B u r e a u , t h e s u b s i d e n c e o f g r o u n d l e v e l a t P i n g t u n gc o a s t a l a r e a d u r i n g t h e 1 9 7 0 - 8 3 p e r i o d w a s 0 - 3 - 2 .0 m ( A n o n . , 1 9 8 3 ) .A n o t h e r i n v e s t i g a t i o n s u g g e s t e d t h a t m o s t o f t h e g r o u n d w a t e r i n t h i sa r e a h a s b e e n p u m p e d i n t o e e l a n d s h r i m p p o n d s ( H . C . C h i a n g ,u n p u b l i s h e d w o r k ) .T o a v o i d f u r t h e r s u b s i d e n c e , d i g g in g o f w e ll s f o r g r o u n d w a t e r i ss t r i c tly p roh ib i t ed . T h is re s t r i c t ion fo rces the f i sh fa rm ers e i the r tor e d u c e s t o c k i n g d e n s i t y o r t o r e u s e d i s c h a r g e d p o n d w a t e r . T r e a t m e n ta n d r e u s e o f a q u a c u l t u r a l w a s t e w a t e r h a v e b e e n e x t e n s i v e l y s t u d i e da n d t h e i r a d v a n t a g e s i n s a v i n g w a t e r r e s o u r c e s h a v e b e e n j u s t i f i e d( B o h l , 1 9 7 7 ; L o m a x a n d Wh e a t o n , 1 9 7 8 ; C h i b a , 1 9 8 0 ; S a t o m i , 1 9 8 0 ) .L o w c o n c e n t r a t i o n s o f d i s s o l v e d o x y g e n , a c c u m u l a t i o n o f o r g a n i cd e b r i s a n d t o x i c n i t r o g e n c o m p o u n d s s u c h a s n i t r i t e a n d u n - i o n i z e da m m o n i a a r e w i d e l y r e c o g n i z e d a s th e m a i n l i m i t in g f a c to r s i n th epond cu l tu re o f f i sh (Busch e t a l . , 1 9 7 4 ; Wi c k i n s , 1 9 7 6 ; B o y d e t a l . ,1 9 7 9 ; W i c k i n s , 1 9 8 3 ) . H o w e v e r , t h e r e h a v e b e e n r e l a ti v e l y f ew s tu d i e so n t h e r e c i r c u l a ti o n o f w a t e r i n e e l a n d s h r i m p c u l t u re s i n T a iw a n . T h ep r e s e n t s t u d y e x a m i n e s s o m e w a t e r q u a l i t y p a r a m e t e r s i n e e l p o n d sa n d c h e c k s t h e e f fe c t iv e n e s s o f s o m e s i m p l e m e t h o d s f o r i m p r o v e m e n to f w a t e r q u a li ty . A p i l o t w a t e r r e c i r c u l a ti o n s y s t e m i n t h e W u s h a n t o uF r e s h w a t e r F i s h C u l t u r e D e m o n s t r a t i o n C e n t e r o f t h e T a i w a n F i s h -e r ie s Bu reau (F ig . 1) was a l so eva lua ted .

J

F i g . 1. G e n e r a l l a y o u t o f t h e p o n d s a n d a s s o c i a t e d r e c i r c u l a t i o n s y s t e m at W u s h a n -t ou F r e s h w a te r F i s h C u l t u r e D e m o n s t r a t i o n C e n t e r ( W F C D C ) , T a i w a n F i s h e r ie sB u r e a u . , W a t e r s u p p l y ; . . . . . . . .. . , w a t e r d r a i n a g e .


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T r e a t m e n t a n d r e u s e o f a q u a c u ln ~ r a l w a s t e w a t e r i n T a i w a n 303M A T E R IA L S A N D M E T H O D S

W a s t e w a t e r c h a r a c t e r i s t i c sFour com m erc ia l ee l po nd s wi th su r face a reas o f 5 00 m 2, 990 m 2,1010 m 2 and 390 m 2, r e spec t ive ly , were inves t iga ted . T he averaged e p t h s o f t h e s e p o n d s w e r e 0 - 9 - 1 .2 m . T h e y w e r e a l l s u p p l i e d w i t hg r o u n d w a t er , w h i c h w a s k e p t f l o w i n g th r o u g h c o n s t a n t ly . T h e f lo wr a t e w a s m o n i t o r e d w h e n sa m p l i n g .SEx w ate r sam ples were co l lec ted f rom the e f f luen t o f each pon d a t4 h i n t e r v a l s . Wa t e r q u a l i t y p a r a m e t e r s i n c l u d e d D O ( e l e c t r o d e ) a n dp H ( g l a s s e l e c t r o d e ) . T o t a l a m m o n i a n i t r o g e n ( p h e n a t e m e t h o d ) ,n i t r i t e n i t rogen (d iazo t iza t ion method) , n i t r a te n i t rogen (b ruc inem e t h o d ) , C O D ( d i c h r o m a t e m e t h o d ) , e l e c t r i c a l c o n d u c t i v i t y , t o t a lso l ids , e tc . , were checked . Al l ana lyses were ca r r i ed ou t fo l lowing theS t a n d a rd M e t h o d ( A P H A , 1 97 6).

S o l i d r e m o v a lW ater sam ples f rom ee l pon ds w i th in i ti a l susp end ed so l ids o f 161 m gl i te r - J a n d p H 8"3 w e r e u s e d f o r s o li d r e m o v a l s t u d y . T h e l a b o r a t o r ys e t t l i n g s t u d y w a s c o n d u c t e d i n a P V C c o l u m n ( F i g . 2 ) . S u s p e n d e ds o l i d s w e r e d e t e r m i n e d o n s u b s a m p l e s d r a w n a t 0 , 3 0 , 6 0 , 9 0 , 1 2 0 ,1 8 0 , 2 4 0 a n d 3 0 0 r ai n. A s e tt li n g r a t e - t i m e r e l a t io n s h i p w a s d e r iv e df r o m s u b s a m p l e s t a k e n f r o m t a p s a t 6 1 ,1 2 2 a n d 1 8 3 c m d e p t h s .

C a l c i u m h y d r o x i d e , f e r r i c c h l o r i d e , a l u m i n u m h y d r o x i d e a n d f i l t e ra lum were used fo r coagu la t ion s tudy in the l abora to ry . The e f fec t ive -ness o f these reagen ts was judged by the i r ab i l i ty to p roduce a v i s ib lef lo c w h e n a d d e d t o t h e p o n d w a t e r i n a 1 0 0 0 m l s et tl in g c y l in d e r . T h et u r b i d i ty w h i c h i n d i c a te s t h e t r e a t m e n t e f f ic i e n c y w a s m e a s u r e d b yu s i ng a T u r b i d i m e t e r . T h e o p t i m u m a m o u n t s o f c o a g u l a n t s w e r e a ls od e t e r m i n e d b y a si m i l a r j a r - te s t p r o c e d u r e ( E c k e n f e l d e r , 1 96 6).

A m m o n i a s t r i p p i n gPond wate r f rom a f reshwate r po lycu l tu re pond was used fo r th i s t e s t .3 0 0 0 m l o f p o n d w a t e r e a c h w a s p l a c e d i n f i v e b e a k e r s a n d t h e p H


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3 0 4 H. C. Chiang, J. C Lee

F i g . 2 .

] L - - L . .

! 6 5 c m ~i! . 1 5 2 c m ~

, 5

E

L uj_~I7 3 2 cm

L a b o r a t o r y s e tt li n g c o l u m n f o r t h e e v a l u a t io n o f f l o c c u le n t s e t tl in g o f e e lp o n d w a t e r.

a d j u s t e d i n t h r e e o f t h e m t o 9 -0 , 1 0" 0 a n d 10-5 w i t h s o d i u m h y d r o x i d es o l u ti o n . A n a ir c o m p r e s s o r w i th 1 2 0 0 c m 3 m i n - ~ f lo w r at e w a s u s e df or ae r a t io n . T o ta l a m m o n i a n i t r o g e n , N H 4 - N , w a s d e t e r m i n e d o ns a m p l e s t a k e n a t 0 , 0 . 5 , 1 , 2 , 3 a n d 5 h a f t e r a e r a t i o n .E v a l u a t i o n o f t h e p i l o t r e c i r c u l a t io n s y s t e mT h e p o n d w a t e r t r e a t m e n t a n d r e cy c l i ng s y s t e m a t W F C D C is s h o w ni n F ig . 3 . T h i s s y s t e m c o n s i s t s o f t h r e e s e t t l in g b a s i n s , a fi lt e r u n i t a n da n a e r a t i o n r a c e w a y . E a c h b a s i n h a s a s u N a c e a r e a o f 5 3- 6 m 2 a n d a na v e r a g e d e p t h o f 1.2 m p r o v i d i n g a v o l u m e o f 6 4 -3 m 3. W a t e r fl o w b yg r a v i t y i s s h o w n i n F i g . 3 . T h e a v e r a g e f l o w r a t e i s 2 8 . 3 m m i n - L a n dt h e r e t e n t i o n t i m e i n t h e s e t t li n g b a s in s w a s 6 8 m i n . T h e g r a ve l fi lt e ru n i t h a s a t o t a l e f f e c t i v e v o l u m e o f 9 "4 m -~. W a t e r f l o w s t h r o u g h t h eg r av e l f r o m b o t t o m t o t o p f o r m i n g a s u b m e r g e d , u p f l o w f il te r. T h ea e r a t i o n r a c e w a y m e a s u r e d 2 6 .6 m x 1.2 m , p r o v i d i n g a v o l u m e o f3 2 -9 m 3 a t a d e p t h o f 1 m . T h e a v e r a g e f lo w r a t e o f 4 0 7 0 m 3 d a y -g i ve s a n a p p r o x i m a t e r e t e n t i o n t i m e o f 8 7 m i n f o r t h e e n t i r e s y st e m .


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T r e a t m e n t a n d r e u s e o f a q u a c u l t u r a l ~ a s r e w a t e r i n ~ z i w a n 3 0 5F U S~ S P

/

f ' L _ _

5 ~

/ ' I i

. i %oui

o u t

F i g . 3 . T h e w a s t e w a t e r t r e a t m e n t u m t o f t h e r e c ir c u l a t io n s y s t e m a t W F C D C . S P,se t tl i ng po nd ; F U , f i l te r un i t ; A R , ae ra t i on r acew ay : * , s am p l i ng l oca t i on .

The filter material was gravel at the first sampling period, replacedwith oyster shell toward the end of this survey. Since there was littledifference between these two materials, the results were pooled.Measurements of water quality parameters were also carried out asmentioned above.

RESULTS AND DISCUSSIONW a s t e w a t e r c h a r a c t e r i s t i c s

The summary of water quality parameters, maximum flow of effluentsand fish:water ratios are presented in Table 1.Maximum flows of the four surveyed eel ponds were monitored atnight time, and suggested that fish farmers use changes of water toreduce the risk of oxygen depletion at night. However, data are notavailable to evaluate the efficiency.Dissolved oxygen concentration is usually low at dawn. Nomura(1980) reported that the growth of eels was reduced by DO concen-tration less than 3 mg liter-~. DS/TS ratios between 0.74 and 0.93indicated a high content of organic compounds in total solids. Chemi-cal oxygen demand (COD) values (15.7-76.2 mg liter-~)in this studywere higher than that (ND-43 mg liter-~) reported by Chiba (1980).Total ammonia nitrogen (TAN) sometimes may exceed 1 mg liter-iThe percentage of TAN existing as un-ionized ammonia at differentpH and temperature levels can be estimated from tables presented by


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~a

O,

TABLE1

SmmayoWaeQuyPameeoWacwaeomeCuueP

Iem

1

2

3

4

Ra

Iae

4242

8282

9191

1111

1111

MaowCMI

25

36

12

2

42

1242

Waeempaue

1820

2026

2738

202

2020

1838

(WTC

pH

7

82

7

81

779

78

78

7

95

Disovo

5962

5081

2912

488

313

2912

(DO)mge

Epmhcm-~

34

33

11

78

67

3

1

TasodT

44

22

88

-

-

28

mge

Isovsod

33

22

77

-

27

(DSn

e

Sp

sod

51

13

81

-

-

11

(S

mg

CD,mge~

172

1136

5272

1018

1120

1772

NHaN,n

e

-

01"

00

009

05111

01

N

Nmge

-

0102

0000

0000

0103

0003

NO~N,n

e

_

_

-

091

0914

0914

IST

0708

{

{9

08{9

-

-

1709

Ishwacao

11

17

I5

I9

13

13

10

E=EecC

vyDST=aooDisovSdoTaSd

B 2I r


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T r e a t m e n t a n d r e us e o f a q u a c u l t u r a l w a s t e w a te r in T a i w a n 3 0 7T r us se ll ( 1 9 7 2 ) a n d B o y d ( 19 79 ~. A c c o r d i n g t o N o m u r a ( 1 98 0 ), th et ox ic l e v el o f N H 3 c o n c e n t r a t i o n i n e e l p o n d s w a s 0 ' 0 5 6 m g l i t e r-( p H 6 '7 , 2 5 C , 2 0 p p m T A N ) . T h e s e d a t a s u g g e s t e d th a t l o w D Oc o n c e n t r a t i o n s a n d h i g h l e v e l s o f t o x i c n i t r o g e n m a y b e k e y l i m i t i n gf a c t o rs o f e e l c u l t u r e i n T a iw a n .R e m o v a l o f s o l id s

T h e r e su l ts o f l a b o r a t o r y s o l id s r e m o v a l i n e e l c u l t u re w a s t e w a t e r a reN v e n i n T a b l e 2 . T h e p e r c e n t a g e s o f r e m o v a l p l o t t e d a g a i n s t t h e i rr e s p e c t i v e d e p t h s a n d t i m e s a r e s h o w n i n F i g . 4 . R e f e r r i n g t o t h i sf i gu r e , i t i s c l ea r t ha t a t a pe r i od o f 60 man and an ove r f l ow r a t e o f4 3 .9 m 3 d a y - * m - 2 , 3 0 - 5 % r e m o v a l o f t o ta l s u s p e n d e d s o li d s c a n b ee x p e c t e d . T h e p o o r e r e f f i c ie n c y o f a se t tl in g b a s in c a n b e e x p e c t e dw h e n i ni ti al c o n c e n t r a t i o n o f s u s p e n d e d s o l id s is b e l o w 1 6 1 m gl i t e r - ~ . S e d i m e n t a t i o n i s o n e o f t h e m o s t e c o n o m i c a l p r o c e s s e s f o rs o l i d - l i q u i d s e p a r a t i o n t h a t h a s b e e n u s e d i n w a t e r t r e a tm e n t . H o w -eve r , s e t t l i ng expe r i men t s i n t h i s s t udy s ugges t ed t ha t u s i ng a s e t t l i ngb a s i n o n l y t o t r e a t fi sh p o n d w a t e r c o u l d n o t a c h i e v e a s a t is f a c to r yr es u lt , b e c a u s e o f t h e h i g h c o n t e n t o f o r g a n i c c o m p o u n d s i n t h e s o lid s .W h e n t h e p o n d w a t e r w as tr e a te d w i th t he s a m e a m o u n t o f s e ve ra lc o a g u l a n t s , f il te r a l u m w a s t h e m o s t e f f e c t iv e c o a g u l a n t c o m p a r e d t ot h e o t h e r s t e s t e d . T h e r e f o r e , t h e o p t i m u m d o s a g e o f f i l t e r a l u m w a sd e t e r m i n e d b y t h e s a m e p r o c e d u r e . T h e r e su l ts a r e s h o w n i n F ig . 5 . A t

T A B L E 2S e t t li n g D a t a o f E e l C u l t u r e W a s t e w a t e r

R e t e n t i o n t i m e(mi t t )

P e r c e n t r e m o v a l ( i n it ia l so l i d s = 1 6 1 m g l it e r - I )6 1 c m 1 2 2 c m 1 8 3 c m

3(/ 22 0 06 0 2 9 2 0 2 29 0 3 5 3 9 3 2

1 2 0 5 5 4 2 3 61 8 0 6 1 4 7 3 92 4 0 6 1 5 2 4 83 OO 6 6 6 0 5 3


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308 H. C. Chiang, J . C. L ee

Fig. 4 .

O l \ ~ x ~ k a C O , ! 61 m g htr e "~

I I 1 I I I6 0 1 20 1 8 0 2 4 0 3 0 0 3 6 0T i m e , m m

S e t t l in g p a t h s o f t h e e e l p o n d w a t e r a s m e a s u r e d b y c y l i n d e r t es t.

Fig . 5 .

7oFiI

6 ~o~-~ ~cc.~ 3cL

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I~ ~ C ) 5 00 2 ~ 0 3 0A l u m c o n c e n t r a t i o n ( r a g h t r e "~ )

E f f e c t i v e n e s s o f a l u m ( a l u m i n u m s u l f a t e ) i n r e m o v i n g t u r b i d i t y f r o m ee lp o n d w a t e r.

p H 8 " 3, 3 0 p p m o f f il te r a l u m w a s s u f f i c ie n t . H o w e v e r , t h e to x i c it y o fa l u m t o e e l s s h o u l d b e f u r t h e r d e t e r m i n e d b e f o r e t h e f e a si b il it y c a n b ea s s e s se d . C o a g u l a t i o n is e m p l o y e d f o r r e m o v a l o f w a s te m a t e ri a ls ins u s p e n d e d o r c o l lo i d a l f o r m . O r g a n i c c o m p o u n d s , s u c h a s p r o te in s ,p r e s e n t i n a q u a c u l t u r a l w a s t e w a t e r , c a n m a i n l y b e h y d r o p h i l i c c o l l o i d sw h i c h e : d , , i b i t a m a r k e d a f f i n i t y t o w a t e r . T h e a b s o r b e d w a t e r r e t a r d s


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Treatment and reuse of aquacultural wastewater in Taiwan 309f loccu la t ion which requ i res spec ia l t r ea tment to ach ieve e f fec t ivec o a g u l a t i o n ( E c k e n f e l d e r , 1 9 6 6 ) . F u r t h e r m o r e . a l u m a p p l i c a t i o n w i l lc h a n g e t h e p H v a l u e a n d a l k a l in i t y o f p o n d w a t e r s ( B o y d , 1 9 7 9 ) .The f indh~gs o f th i s s tudy sugges t tha t so l ids remova l f rom aqua-c u l t u r a l w a s t e w a t e r b y c o n v e n t i o n a l p h y s i c a l a n d c h e m i c a l t r e a t m e n tprocesses is no t v e ry e f fec tive and i ts econ om ica l f eas ib i li ty s ti ll need sto be jus t i f ied .A m m o n i a s t r i p p i n gC o n c e n t r a t i o n o f t o t a l a m m o n i a n i t r o g e n s h o w e d n o s i g n i f i c a n tc h a n g e d u e t o a e r a t i o n t r e a t m e n t u n d e r l a b o r a t o r y c o n d i t i o n s ( T a b l e3 ) . T A N c o n s i s t s o f a m m o n i u m i o n ( N H ~ ) a n d u n - i o n i z e d a m m o n i a( N H ~) w h i c h s h i f t s a c c o r d i n g t o t h e f o l l o w i n g p H - d e p e n d e n t e q u i -l ibr ium:

N H ~ e-- NH ~ + H T h e r e f o r e , t h e u n - i o n i z e d a m m o n i a i n c r e a s e d w h e n t h e p H v a l u e o fthe w a te r ad jus ted to a h ighe r l eve l. S ince on ly the N H 3 can be a i r -s t r ipped , the e f f i c iency o f NH 3 s t r ipp ing a t pH 10-5 is s l igh t ly h ighe rthan a t pH 7"6.S t u d i e s o n a m m o n i a s t r i p p i n g w e r e f e w a n d p r i m a r i l y l i m i t e d t oh i g h a m m o n i a c o n c e n t r a t i o n c o n d i t i o n s . I n c r e a s i n g o f a ir fl ow , p H a n dt e m p e r a t u r e m a y h a v e b e t t e r e f fi c ie n c y , b u t a l l t h e s e m e t h o d s a r ec o s t ly f o r a q u a c u l t u r a l w a s t e w a t e r t r e a t m e n t a n d t h e r e f o r e n o tp rac t i ca l. For h igh ly so lub le gases such as am m onia , a i r - s t r ipp ing a tlow co nce n t ra t io n wi l l be ve ry d i f fi cu lt , i f no t imposs ib le .

TABLE 3Ammonia Stripped by Aeration at Various pH Values and Periods

Treatment Stripping periods (h)pH Aeration 0 0"5 I 0 2"0 30 4{)7.6 - 2.258 2.301 2-345 2.035 2-570 2.4907-6 + 2.258 2-709 2.037 2.164 2.127 2-5279.0 + 2.403 2.164 2.220 2.037 1.983 2.218

10-0 + 2.491 2.810 2.580 2.052 2.745 2-38210.5 + 2'309 2.491 2-200 1-855 1-964 1.946


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Treatment and reuse of aquaculmral wastewater in Tai~an 311E v a l u a ti o n o f r ec y c l in g s y s t e m a t W F C D CT h e d i f f e r e n t t r e a t m e n t p r o c e s s e s t e s t e d i n a re c y c l in g s y s t e m r e s u l t e di n n o s i gm i f ic a n t d i f f e r e n c e s i n th e w a t e r q u a l i t y a c c o r d i n g t o t h e p a r a -m e t e r s m e a s u r e d ( T a bl e 4).

M o s t o f t h e p a r t ic l e s w e r e n o t r e m o v e d b y t h e s et tl i ng t re a t m e n t .T h i s c o i n c i d e s w i th t h e r e s u lt s o f l a b o r a t o r y t es ts . C h a n g e s i n C O Da n d n i t r o g e n c o n c e n t r a t i o n a c r o s s t h e g r a v e l o r o y s t e r f i l t e r w e r e n o td e t e c t e d f o r t w o r e a s o n s . F i r s t , t h e fl o w r a te t h r o u g h t h e f il te r w a sr a p i d ( 1 7 0 m 3 h -~ ) c a u s i n g o n l y s m a l l c h a n g e i n c o n c e n t r a t i o n .S e c o n d , t h e c o n c e n t r a t i o n o f t h e i n fl u e n t s w a s t o o l o w t o b e t r e a te d .T h e r e w a s o n e p a r a m e t e r w h i c h w a s s ig n if ic a n t f o r a e r a t i o n t r e a tm e n t .D O c o n c e n t r a t i o n w a s s i g n if ic a n tl y i n c r e a s e d a f te r p a s s in g t h r o u g h a na e r a t i o n r a c e w a y .

T h e r e s u l t s o f t h i s s t u d y s u g g e s t e d t h a t t h e g r a v e l f i l t e r w a s n o ts u f f i c i e n t t o m e e t t h e d e m a n d s o f t h e b i o l o g i c a l t r e a t m e n t . F r o m t e c h -n i c a l a n d e c o n o m i c p o i n t s o f v i e w , b i o l o g i c a l c a r b o n o x i d a t i o n a n dn i t r i f i c a t i o n s h o u l d b e i m p r o v e d a n d f u r t h e r i n c o r p o r a t e d i n t h i ss y s t e m .

R E F E R E N C E SAm er ican Pu b l i c Hea l th Asso c ia t io n (1 9 7 6 ) . S t a n d a r d m e t h o d f o r t h ee x a m i n a t i o n oJ" w a t e r a n d w a s t e w a t e r , 1 4t h e d n , A P H A , W a s h in g to n D C .p. 1193.An o n . ( 1 9 8 3 ) . W a t e r d i v e r s i o n a n d d e l iv e r ), p l a n n i n g j b r P i n g t u n g C o a s t a /area. Ta iwan Pro v in c ia l Wa te r Co n se rv an cy Bu reau , 1 80 p p .Bohl , M. (1977) . S om e ini tial a qua cu l tu re ex per im ents in rec i rcu la t ing watersys tems. A q u a c u l t u r e . , 1 I , . ~ ,. ~ - o .Boyd, C. E . (1979) . W a t er q u a l i O ' i n w a r m w a t e r f is h p o n d s . Au b u rn Un ix .Agr ic . Exp . Stn ., Aub urn , A laba m a, 361 p p .Boy d , C. E ., R om aire , R. P . & Joh nsto n , E . (1979) . W ater qua li ty in channelca t fi sh p ro d u c t io n p o n d s . J . E n v i r o n . Qu a l . , 1 8 , 4 2 3 - 9 .Busch, C. D, , Koon, J . L. & All ison, R. (1974) . Aerat ion, water quali ty , andca t fi sh p ro d u c t io n . T r a n s . A S , 4 E , 1 7 , 4 3 3 - 5 .Chiba, K. (1980) . Effect ive ut i l izat ion of water in var ious f ish culturem e th o d s . I n: F r e s h w a t e r F is h C u l t u r e a n d W a t er S u p p l y , Jap. Sci . Fish. Soc. .T o k y o , p p . 3 0 - 4 6 .Eckenfe lder , W. W. (1966) . l n d t t s t r i a l w a t e r p o l h t t i o n c o n t r o l . McGraw-Hi l l .

New Yo rk , 2 7 5 p p .Lomax, K. M. & Wheaton , E W. (1978) . Pre t rea tment o f f i sh cu l tu re waste -water for ni tr i f icat ion. T r a n s . , 4 S A E , 2 1 , 1 9 7 - 2 0 0 .


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312 H. C Chiang d. C LeeN o m u r a , M . ( 1 9 8 0 ). P r o d u c t i o n a n d e n v i r o n m e n t a l c o n d i t io n s in r u n n in gw a t e r p o n d fo r f i s h cu l t u re . I n : Fre shw ater Fish C, dn~re an d Water Supply,

Jap . Sc i. F i sh . Soc . , To ky o , pp . 64 -8 3 .Sa t o mi , Y. (1 9 8 0 ) . P re s en t s t a te an d p ro b l e m s o n w a t e r s u p p l y i n fi sh cu l tu re .In : Freshw ater F ish Cul ture an d Water Supp ly , Jap. Sci . Fish . Soc. , Tokyo,p p . 2 0 -9 .T r us se U , R . R (1 9 7 2 ) . T h e p e r c e n t u n - io n i z e d a m m o n i a i n a q u e o u s a m m o n i as o l u t i o n s a t d i f f e r en t p H l ev e l s an d t emp era t u re s . J . Fish. Res. BoardC a n a d a , 2 9 , 1 5 0 5 - 7 ,W i ck in s , J . F . ( 1 9 7 6 ) . T h e t o l e r an ce o f w a rm -w a t e r p r aw n s t o r ec i r cu l a t edw a t e r . A q u a c u l t u r e , 9 , 1 9 -3 7 .Wick ins , J . F . (1983) . S tud ies on mar ine b io log ica l f i l t e rs , Water Res. , 17,1 7 6 9 - 8 0 .

Chiang 1986 Aquacultural-Engineering

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