Miller 1984 Aquacultural-Engineering

7/28/2019 Miller 1984 Aquacultural-Engineering

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Aquaculrura l E ngineer ing 3 (1984) 39-57

E v a l u a t i o n o f a T r i c k l i n g B i o f il te r i n a R e c i r c u l a t in gA q u a c u l t u r e S y s t e m C o n t a i n i n g C h a n n e l C a t f i s h *Ga ry E. M iller and George S. Libey

Department of Forestry and Natural Resources, Purdue University,West Lafayet te , Indiana 47 907 , U SA

A B S T R A C TSix 106 0 l i te r rec i rcu la ting cu l ture sys tem s were te s ted , d i f f e r ing on ly int h e q u a n t i t y o f f i l t e r me d i u m a n d t h e r e c ir c ul a ti n g f l o w r a te . A f t e r a p re -l iminary loa ding trial to d eter m ine ap pro xim ate ca rrying capacit ies, 45 .4 kgo f c h a n n e l c a t f i s h Ictalurus punctatus averaging 35 .6 cm were s tocked ineach sys tem. A f te r 15 w eeks , f ina l loadings ranged f ro m 67 to 85 g l i te r 1sys tem capac i ti e s (8 5 -1 0 9 g l i t e r l cu l ture ta nk densi tie s] . Water qual i t yw a s g o o d t o e x c e l le n t w h e n t h e p a c k e d t o w e r s c o n t a i n e d t h e me d i u m .Di s so l ve d o x y g e n w a s p r o b a b l y t h e mo s t l i m i ti n g f a c t o r o f t o t a l p r o d u c -t io n . Ho w e v e r , t h e r a te o f p r o d u c t i o n w a s i n f lu e n c e d b y t h e c o mb i n e de f f e c t o f c o n c e n t r a ti o n s o f d is s o lv e d o x y g e n , N H 3 - N a n d / o r N O g . - N o t h er -wise con sidered sale .

N O M E N C L A T U R EC D i s so lv e d o x y g e n c o n c e n t r a t i o n ( m g l it er - t ) i n t h e s y s t e m u n d e r

f i e l d c o n d i t i o n sR D a i l y f e e d i n g r a t i o n ( as a f r a c t i o n o f T w t )T w t T o t a l w e i g h t o f f is h in t h e c u l t u r e s y s t e m ( k g )X A v e r a g e w e i g h t o f t h e f is h ( g)

D i r t y w a t e r m a s s t r a n s f e r c o e f f i c i e n tc~ ' C le a n ' w a t e r m a s s t ra n s f e r c o e f f i c i e n t

* Purdue University Agricultural Experiment Station jou rnal paper num ber 960 4.39

Aquacul tura l Engineer ing O144- 8609 /84 /S 03 .00 - Else v ie r App l i e d S c i e nc ePublishers Ltd, England, 1984. Printed in Great Britain


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40 G. E . M i l le r , G . S . L ibe y

I N T R O D U C T I O NT h e l i k e l ih o o d o f w a t e r r e u s e i n a q u a c u l t u r e a p p e a r s c e r t a i n as t h ea v a i la b i li ty o f h i g h q u a l i t y w a t e r d e c r e a s e s a n d t h e d e m a n d f o r fi sh a n ds e a f o o d c o n t i n u e s t o i n c r e a se ( S t e l l m a c h e r , 1 9 81 ). W i th r eu s e c o m e st h e n e e d to r e c o n d i t i o n t h e w a t e r , b u t o n c e th e r e c o n d i t i o n i n g p r o c es sh a s b e e n d e v e l o p e d s u f f i c i e n t l y t h e n u m b e r o f r e u s e c y c l e s a v a il ab le tot h e c u l t u r i s t b e c o m e s v e r y la r ge a n d t h e e f f i c ie n c i e s o f p r o d u c t i o ni m p r o v e e x p o n e n t i a l l y ( M u i r , 1 9 8 1) . F i sh c u l t u ri s ts h a v e b e e n c o n -s t r u c t i n g r e u s e s y s t e m s f o r o v e r 2 0 y e a r s , b u t t h e d e g r e e o f s u c ce s s h a sb e e n l i m i te d ; p o s si b ly d u e t o a la c k o f e n ~ n e e r i n g b a c k g r o u n d t oc o m p l e m e n t t h e i r b i o lo g ic a l e x p e r ti s e.

T h e m o s t i m p o r t a n t c o m p o n e n t o f a r e c i r c u la t e d fis h c u l t u r e s y s t e mis t h e f il te r , u s e d t o r e m o v e o r d e t o x i f y m e t a b o l i c w a s te s . O f th e s ew a s t e s , a n a m o n i a a n d i ts o x i d i z e d f o r m ( n i t r i t e ) a re t h e m o s t t o x i c .A m m o n i a c a n b e r e m o v e d b y c h e m i c a l f i l tr a t i o n o r o x i d i z e d t o le sst o x i c n i t r a t e b y b i o lo g i c a l f i l t r a t io n . T y p e s o f b i o lo g i c a l fi lt e r s a r eu p w e l l f i l t e r s , s u b m e r g e d d o w n f l o w f i l t e r s , p a c k e d t o w e r s ( t r i c k l i n gf i lt e rs ) a n d r o t a t i n g b i o l o g ic a l c o n t a c t o r s ( R B C ) o r r o t a t i n g d i sc f il te r s .C h e m i c a l f il te r s , u p w e l l f i lt e r s a n d s u b m e r g e d d o w n f l o w f il te r s a ll h a v et h e d i s a d v a n t a g e o f r e q u i r i n g p e r i o d ic r e c o n d i t io n i n g , e i t h e r a s i o n ice x c h a n g e ( r e c h a r g e ) i n c h e m i c a l f i l t e r s o r b a c k f l u s h i n g t o r e m o v ee x c e s s i v e b u i ld u p o f p a r t i c u l a t e s a n d f l o c c u l e n t s f r o m t h e b io f i lt e r s .P a c k e d t o w e r s a n d R B C s t e n d t o b e s e l f- c l e a n in g .

A l i t e r a t u r e r e v ie w o f p a c k e d t o w e r a n d R B C a p p l i c a ti o n s in a q u a -c u l t u r e r e ve a ls l it tl e w h i c h w i ll a ll o w t e c h n i c a l c o m p a r i s o n s o f s y s t e mp e r f o r m a n c e s . P h y s ic a l d e s c ri p t io n s a b o u n d , b u t i n f o r m a t i o n a b o u th y d r a u l i c l o a d i n g o f t h e f i lt e r , m e d i a s u r f a c e ar e a s, v o i d t r a c t i o n ,c h a n g e s in a m m o n i a c o n c e n t r a t i o n a c r os s t h e f il te r a n d t h e d y n a m i c so f a m m o n i a , n i t r i t e a n d n i t r a t e w i t h i n t h e s y s t e m , b o t h r e s o l v ed a n du n r e s o l v e d , t y p i c a l l y a r e n o t a v a i l a b l e .

O u r s tu d y w a s u n d e r t a k e n t o c o n f i r m t h a t a c c e p t a b l e w a t e r q u a l i tyc o u l d b e m a i n t a i n e d a n d t o i d e n t i f y a n d q u a n t i f y d y n a m i c a c t iv i ti esr e l e v a n t t o t r i c k l i n g f il t e r d e s i g n c o n s i d e r a t i o n s . T h e f i rs t p h a s e o f o u rs t u d y w a s a s y s t e m l o a d in g t ri al t o a p p r o x i m a t e t h e b i o m a s s t h a t t h es y s t e m c o u l d s u p p o r t a n d sti l l m a i n t a i n a c c e p t a b l e w a t e r q u a l i t y c o n d i -t io n s . T h i s w a s f o l l o w e d b y a g r o w t h t ri a l to d e t e r m i n e i f t h e s e r e s u l t sw e r e a f f e c t e d b y t h e r a t e a t w h i c h f is h w e r e a d d e d t o t h e s y s t e m .


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Trickling b iofilter in a recirculating system for channel catfish 41Channel catfish Ictalurus punctatus were chosen as the study speciesdue to their commercial importance and the limited informat ion abouttheir use in this type of system (in comparison to salmonids).

MATERIAL S AND METHODSSix culture systems were tested, differing only in the quantity of filtermedium used and the recirculation flow rate. The basic system (Fig. 1)consist ed o f a 1.22 m diamet er 830 liter circular tan k and two 115 litersumps. The tank was the culture unit and the sumps provided settling

Fig. 1. Culture system as tested with packed tower (FT) in place. System consistsof an 830 liter culture tank and two 115 liter sumps (one for tube clarification; oneas reservoir with pumping).


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42 G. E. Miller, G. S. Libeyo f p a r t i c u l a te s ; o n e c o n t a i n e d a t u b e c l a ri fi e r, t h e o t h e r a s u b m e r g e dp u m p f o r r e c ir c u la t io n . E a c h c u l t u re u n i t re c e iv e d c o n t i n u o u s s u p p le -m e n t a l a e r a t i o n f r o m a 0 . 0 3 7 k W s u r f a c e a g i ta t o r . T h e w a t e r l ev e l w a sc o n t r o l l e d b y an a d j u s t a b l e s t a n d p i p e i n t h e c l a ri f y in g p u m p .

T h e f il te r t e s te d w a s a p a c k e d t o w e r c o n s i s ti n g o f a n a l u m i n u mf ra m e 2 . 4 4 m X 4 2 . 5 5 c m X 4 2 - 5 5 c m . I t w a s p a r t i t io n e d i n to t w ob a s k e t s m a d e o f 0 . 6 4 c m p l a s t ic m e s h , e a c h 0 . 7 6 m d e e p , s e p a r a t e d b ya 0 - 4 6 m d r o p s p a c e . T h e r e m a i n i n g 0 . 4 6 m w a s a t th e t o p o f t h e t o w e rt o a c c o m m o d a t e p l u m b i n g a n d m o u n t i n g o f a p e r f o r a te d s p la sh p la tef o r w a t e r d i s t r i b u t i o n . T h e f i lt e r w a s s t u d i e d i n t h r e e c o n d i t i o n s : f ul lt o w e r (F T ) , h a l f f u ll ( b o t t o m b a s k e t f u ll o f m e d i u m ) ( H T ) a n d e m p t y( E T ) . T h e t o w e r w a s a t t a c h e d t o a fr a m e a n d s e t o n t o p o f t h e c u l t u r et a n k s o t h a t w a t e r p a s s e d f r o m t h e f i lt e r d i r e c t l y i n to t h e c u l t u r e t a n k .W a t e r w a s p u m p e d t o t h e t o p o f t h e t o w e r f o r t h e F T ( ag a in s t a 3 - 05 mh e a d ) , t o t il e t o p o f t h e d r o p s p a c e f o r t h e H T a n d E T ( a 1-83 m h e a d ) .

T h e m e d i u m c h o s e n w a s s t y r o f o a m ' p e a n u t s ' p a c k i n g m a t e ri a l. T h i sm e d i u m w a s s e l e c t e d f o r it s l ig h t w e i g h t , a v a i l a b i l it y a n d l o w c o s t .B r o u s s a r d a n d S i m c o ( 1 9 7 6 ) f o u n d t h a t t h is m a t e r ia l w o r k e d s at is -f a c t o r i l y i n t h e ir s t u d i e s. G r a p h i c a n a l y s is s h o w e d t h a t a p p r o x i m a t e l y2 2 5 m 2 m - 3 w a s p r o v i d e d f o r m i c r o b i a l h a b i t a t i o n . A f u ll b a s k e t o fm e d i u m h a d a 5 5 % v o id f r ac t io n .

E a c h f il te r c o n d i t i o n w a s t es t e d w i t h f l o w r a t e s o f 2 2 -7 a n d 4 5 . 4l i t e rs r a in -~ ( a h y d r a u l i c l o a d o f 7 . 5 a n d 1 5 - I m 3 m - 2 h -~ , r e s p e c t i v e l y ) .A s s u g g e st e d b y B u r r o w s a n d C o m b s ( 1 9 6 8 ) , m a k e u p w a t e r w a s a d d e da t 5 % o f t h e f l o w ra t e ( a 9 5 % r e c i r c u l a t i o n r a t e ) t o m a i n t a i n w a t e rt e m p e r a t u r e s . M a k e u p w a t e r ( T a b l e 1) w a s a m i x o f h o t a n d c o l d d e-c h l o r in a t e d t ap w a t e r , a d j u s t e d t o m a i n ta i n s y s t e m t e m p e r a t u r e s o fa p p r o x i m a t e l y 3 0 C . T h e t ri al s w e r e c o n d u c t e d i n d o o r s , w e ll a w a yf r o m d i re c t s u n li g ht , a n d t h e p h o t o p e r i o d w a s n o t m a n i p u l a t e d .T o h a s t e n d e v e l o p m e n t o f t h e n e ce s s a ry b i ol o g ic a l c o m m u n i t y in t h ef il te rs , t h e s y s t e m s w e r e ' s e e d e d ' f r o m a c t iv e s y s t e m s . A p p r o x i m a t e l y1 8 k g o f ch a n n e l c a t fi s h w e r e s t o c k e d in e a ch s y s t e m a n d g r o w n f o ro v e r t w o m o n t h s t o a l l o w t h e f il te r s t o s t ab i li z e. A f t e r t h is b r e a k inp e r i o d t h e f is h w e r e r e m o v e d a n d t h e t a n k a n d s u m p s w e r e f lu s h e d . F o rt h e l o a d i n g t ri al s, t i . 2 8 k g ( + 0 . 0 5 7 k g ) o f c h a n n e l c a t fi s h , av e r ag i n g3 2 c m in l e n g th , w e r e s t o c k e d o n 2 6 O c t o b e r 1 9 8 0. A f t e r a l lo w i n g f o u rw e e k s t o a s s u r e s y s t e m s t ab i li ty , a p p r o x i m a t e l y 11 k g c h a n n e l c a t fi s hw e r e a d d e d w e e k l y t o e a c h s y s t e m . T h e f i s h w e r e w e i g h e d a n d s o r t e d t oa s s u r e e a c h s y s t e m r e c e i v e d t h e s a m e si ze a n d w e i g h t . T h e f is h w e r e f e d


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Tr i c k l i n g b i o f i l t e r i n a r e c i r c u f a t i n g s y s t e m f o r c h a n n e l c a t f i s hT A B L E 1

Analysis of Dechlorinated Tap Water Used as Makeup Water(26 October 1980 to 26 May 1981)

43

C o n c e n t r a t i o n ( m g l it e r - 1) R a n g eAmmonia-N 0.05 0.00-0-13NO~-N 0.00 0.00--0.02NO~-N 0.27 0-03-0-63pH 7.4 7-38-7.48Alkalinity at a pH 4.5 as CaCO3 247 241-256Hardness (EDTA)as CaCO3 349 321-370Conductivity/arnho cm-~ 660 640-690

to satiation every 12 h (0800 and 2000 hours) a 35% protein float ingcatfish ration. This regime was used to reduce the influence of fluctua-tions in water quality induced by a once a day feeding schedule (Brettand Zala, 1975; Ruane e t a l . , 1977; Carlson e t a l . , 1980). Settleablesolids were siphoned from the sumps weekly.

The water was routinely monitored for temperature, dissolvedoxygen (DO), total ammonia nitrogen (ammonia-N = NH3-N + NH~-N),nitrite nitrogen (NO~-N), nitrate nitrogen (NO~-N), pH, free CO2, hard-ness (EDTA) and conductivity. Samples were tested for ammonia-N,NO~-N, NO3-N using Bausch and Lomb Spectro kits. Un-ionizedammonia (NH3-N) concentrat ions were calculated according to Emersone t a l . (1975). Dissolved oxygen was mon itored by both a YellowSprings Instrument (YSI) Co. dissolved oxygen meter and by theWinkler titrimetric procedure (azide modification; American PublicHealth Association e t a l . , 1980). Free CO2 and hardness (EDTA) weredetermined titrimetrically (American Public Health Association e t a l . ,1980), and conductiv ity was measured with a Hack Mini conductiv itymeter. Simultaneous 24 h composite samples were collected from eachof the systems using a six channel peristaltic pump.

At the completion of the loading trials all fish were removed, countedand weighed. The filters were flushed and the systems thoroughlycleaned. All flow rates were reversed (22-7 liters rain -~ changed to 45.4liters min-~ and vice versa) and temperatures stabilized at approximately30C. The systems were kept full of water and functioning in order to


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4 4 G. E. Mil ler , G. S . Libeykeep the biological community as active as possible. Based on theresults of the loading trial, each system was restocked with 45.43 kg(+0.19 kg) channel catfish 35.6 cm (+ 1.8 cm) in length. This markedthe beginning of the growth trial (7 February 1981 to 26 May 1981).The fish were fed and the water chemistry monitored as before. Weightgains and feed conversions were calculated at the end of the trial. Alka-linity analysis (American Public Health Association e t a l . , 1980) wasadded to the study, but free CO2 was no longer monitored since hazard-ous concentrations did not develop. A modified Kjeldahl (TKN)procedure (Nelson and Sommers, 1972) was used to monitor totalnitrogen in the settleabte solids. Observations were made of the changein ammonia -N concentra tions over time (i.e. hourly grab sample analysis)and across the clarifier. Hourly changes in DO were observed in con-junction with the ammonia-N grab sample analysis.

The Winkler procedure was also used in determining the respirationof microbes in suspension. A sample was collected from each systemand 'recharged' with DO by vigorous agitation. A portion was 'fixed'to determine the starting concentration and a portion incubated in adark bottle for 24 h in the system. The difference between the rechargedsample and the incubated sample was the daily respiration rate. Anadditional portion of the recharged sample was tested for respiration byN i t r o s o m o n a s sp. bacteria with the use of Hack Formula 2 5 3 3 (0.05 gper sample). Its use in water analysis is suggested by the AmericanPublic Health Association e t a l . (1980) to reduce error in BOD analysisdue to nitrification.

RESULTSIn the loading trials total accumulated weights were 83.9-95-7 kg, withgains from growth of 4.7-17-0 kg (Table 2). Average loadings andweight gains were 9 2 . 5 and 13.5 kg respectively. Growth provided a17% weight gain, consistent with observations by Lewis and Buynak(1976) under similar conditions. Mortality rates ranged from 0 to 7.5%.

The water quality constituents of primary concern were the nitro-genous compounds. During the loading trials detrimental concentrationsof NH3-N (0.12 mg liter-X; Robinette, 1976) and NO2-N (1-3 mg liter-X;Colt e t a l . , 1981) were observed in the ET systems and the HT systemwith the lower flow rate (Table 3). The FT systems provided very good


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TABLE2

RusoLnaGowhTasnSxInevCueSes

"

FeNm

WgTaNm

WegWgCo

sodsodfedhvedhvedgn

(kg(kg

(kg

(kg

May (%

Lgra

27eaini

44eain-

Gowhra

'27en1

44eain

E

2

79

33

2

95

16

271

tT

2

70

43

2

92

12

30I

F

2

77

48

2

98

11

29I

E

2

77

45

2

97

10

261

H

2

72

35

2

89

47a79Ia

F

2

72

42

2

98

16

271

E

1

46

53

1

78

22

221

H

1

45

62

1

77

32

211

F

1

42

74

1

85

33

191

E

I1

45

62

1

70

35

20I

H

1

45

65

1

83

38

191

F

1

44

86

1

93

49

19I

"

14

?

00

,~

14 18

~

75 i.9

,~

oo

2.

00

t~

o.o

0.o

~.

00

~

,aVureunfnaCedscuspneao

4


8/19

TABLE3

MenCnrao(RnoNronCmp

DnhLdnanGowhTasoSxInenvCue

Sem

4~

FeAmmoaN

NHsN

NO~N

NO~N

(rae1

(mge

(mge1

[mge)

L

gra

27esran-~

44esmn-1

Growhra

27esran-

44esran-

E

280458010003

0590015

872110

H

340083000002

05nd--7

790813

FT04nd-0

00(nd-00

030008

122916

E

100127000001

030006

490874

H

19(nd-4600(nd-01

040009

390811

FT040008000000

03(nd-09

68(nd-18

E

420295020104

080120

H

140424000000

050209

FT060213000000

030204

E

150157

0100%02

040110

H

060211000000

020105

FT030006000000

010002

191919

139016

17(8719

692618

72(5616

126915

SuTKN(g

36(1143)

361640

381545

381433

31(5246

266242

t~

ndNdeabe


9/19

T r i c k l i n g b i o f i lt e r i n a r e c i r c u l a t in g s y s t e m ] 'o r c h a n n e l c a t f i s h 47c o n t r o l o f N H 3 - N a n d N OV -N ( 0 - 0 9 4 a n d 0 .9 2 m g l i te r " ' m a x i m u mr e s p ec t iv e c o n c e n t r a t i o n s , 0 - 0 1 8 a n d 0 - 39 m g l i te r - ' r e s p ec t iv e m e a n s ) .

D u r i n g t h e 1 5 w e e k g r o w t h t r ia l s w e i g h t g a i n s r a n g e d f r o m 25.2 to4 4 - 9 k g ( T a b l e 2 ) , r e s u l t i n g i n fi n a l l o a d i n g s o f 7 0 . 8 - 9 0 - 2 k g ( 6 6 - 8 -8 5 . 2 g l i t e r ~ s y s t e m c a p a c i t i e s: 8 4 . 7 - 1 0 8 . 8 g l i te r ~ c u l t u r e t a n k c a p a c i -t ie s) . T h e F T s y s t e m s av e ra g e d 3 5 % g r e a te r p r o d u c t i o n t h a n t h e E Ts y s te m s , 2 8% g r e a t e r th a n t h e H T s y s t e m s . F e e d c o n v e r s i o n s r a n g e df r o m 1 .9 1 t o 2 . 2 7 : 1. M o r t a l i t i e s w e r e o b s e r v e d o n l y i n t h e E T s y s t e mw i t h t h e l o w e r f l o w r a te ( 9 . 2 % ) .

C o n c e n t r a t i o n s o f n i tr o g e n o u st h e g r o w t h t r i a l a g a i n r e f l e c t e dD e t r i m e n t a l l e v e l s o f N H a - N a n d

c o m p o u n d s in t h e F T s y s te m s d u r i n ge x c e p t i o n a l w a t e r q u a l i t y ( T a b l e 3 ) .N O T - N w e r e o b s e r v e d o n l y i n t h e E Ts y st em s . T h e H T s y s t e m s s h o w e d s u b s t an t ia l i m p r o v e m e n t in c o n t r o l o f

n i t r o g e n o u s c o m p o u n d s o v e r le ve ls o b s e r v e d d u r i n g t h e l o a d i n g t r ia l.C h a n n e l i z a t i o n w a s n o t o b s e r v e d i n t h e H T f i lt e rs d u r i n g th e g r o w t h

t r ia l s a s i t h a d b e e n d u r i n g t h e l o a d i n g t ri a ls . T h e e x c e s s i v e b i o g r o w t hi n t h e f i lt e r s d u r i n g t h e l o a d i n g tr ia l s s u g g e s t e d t h a t l o a d i n g h a d b e e nt o o r a p id f o r t h e f i lt er s to a d e q u a t e l y r e s p o n d . F e e d a p p l i c a t i o n s d u r i n gt h e g r o w t h t ri a ls 1 -5 -2 t i m e s g r e a t e r t h a n t h o s e d u r i n g t h e l o a d i n g t ri a lsw e r e f u r t h e r e v id e n c e o f t h e i m p r o v e d p e r f o r m a n c e .

F i l t e r v o l u m e h a d a s i g n i f i c a n t i m p a c t o n w a t e r q u a l i t y a n d p r o d u c -t i o n ( T a b le 4 ). A t t h e lo w e r f lo w r at e , a m m o n i a - N d e c r e a s e d b y 60 %p e r a d d i t i o n a l b a s k e t , N H 3 -N b y 6 3 % a n d N O 2 -N b y 4 0% . C o n c e n t r a -t i o n s o f N O 3 - N i n c re a s e d 4 % in r e s p o n s e t o i m p r o v e d n i t r i fi c a t i o n a n dh i g h e r f e e d i n g le v el s. F e e d c o n s u m p t i o n a n d w e i g h t g a in s in c r e a s e d b y1 3 a n d 2 3 % r e s p e c t i v e l y . S l u d g e T K N l ev e ls i n c r e a s e d b y 1 0% f o r t h ef ir s t b a s k e t , b u t d e c r e a s e d b y 8 % f o r t h e s e c o n d . A t t h e h i g h e r f l o wr a te , a m m o n i a - N , N H 3 -N a n d N O g - N c o n c e n t r a t io n s w e re re d u c e d b y5 6 , 6 6 a n d 4 8 % , r e s p e c ti v e l y , b y e a c h a d d i t i o n a l b a s k e t. A n i n c r e a se inN O ~ - N s i m i l a r t o t h a t a t t h e l o w f l o w r a t e w a s al so o b s e r v e d w i t h t h ef i r s t b a s k e t . A 4 2 % i n c r e a s e i n N O ~ - N w a s a s s o c i a t e d w i t h t h e s e c o n db a s k e t o f m e d i u m , re f l e c ti n g th e l a rg e in c re a se i n f e ed c o n s u m p t i o n a n di m p r o v e d n i t ri f i c a ti o n . I n c re a s ed f e e d c o n s u m p t i o n a s s o c ia t e d w i t h t h ef i rs t b a s k e t ( 5 % ) w a s le s s t h a n t h e s e c o n d ( 2 7 % ) . S i m i l a r ly , w e i g h t g a in si m p r o v e d 7 a n d 2 9% f o r e a c h b a s k e t o f m e d i u m . D e c l in e in s lu d g e T K Ns u g g e st e d i m p r o v e d f e e d u t i li z a t io n .

T h e h i g h e r f l o w r a te p r o v i d e d b e t t e r w a t e r q u a l i t y in a ll s y s t e m s( T a b l e 5 ) . A v e ra g e le v el s o f a m m o n i a - N , N H 3 - N a n d N O ~ - N a l l d e c l i n e dm o r e t h a n 5 0% . A 2 9 % d e c l i n e w a s a ls o o b s e r v e d i n N O ~ - N . F e e d


10/19

48 G. E. Miller. G. S. LibeyT A B L E 4

E f fe c t o f I n c r e a s e d F i l t e r V o l u m e o n W a t e r Q u a l i t y a n d P ro d u c t i o n ( a s P e rc e n tInc rease ( t ) o r Decrease (+) ) Dur ing the Growth Tr ia l s o f S ix In tens ive Cul tu re

S y s t e m s22. 7 l i ters mi t t - ~ 45. 4 l i ters min -

E T - -, H T H T - * F T A v er ag e E T - ~ H T H T - " F T A ve ra geA m m on ia-N 66~, 53+ 60+ 60~, 53/ ' 56/ 'NH 3-N 76+ 50+ 63/ ' 75~ 57~ 66~,NO~-N 34/ , 45~, 40 / ' 3 9 ; 57/ ' 48/ 'N O ~ -N 4 t 3 t 41" 4 t 4 2 t 2 3 tSludge TK N 1 0t 8J, 1 5J, 2/ ' 4/ 'F e ed a d d e d l i t 1 5 t 1 3 t 5 t 2 7 t 1 6 tW e ig ht g ain 2 0 t 2 7 t 2 3 t 7 t 2 9 t 1 8 t

T A B L E 5Effec t o f Inc reased F low Ra te ( f rom 22 .7 to 45 .4 l i t e rs ra in -~) on Water Qu a l i tyand P rod uc t ion (as Pe rce n t Inc rease ( t} o r Decrease ( / ') ) Dur ing the Grow th Tr ial s

of S ix In tens ive Cul tu re Sys temsFi l t e r

E T H T F T A v er a geA m m o n i a - N 6 3 ; 5 5 ~ 5 5 /' 5 8 /'NH 3-N 53/, 525 535 53 / 'NO,~-N 48~ 5 2 ; 63+ 54~,NO S-N 37~, 375 13+ 29+Sludge TK N 31' 10~ 45 4~F e e d a d d e d 1 3 t 7 t 1 7 t 121"Weight gain 2 9 t 15 t 17 t 21 t

c o n s u m p t i o n a n d w e i g h t g a in s i n c r e a s e d b y 1 2 a n d 2 1 % r e sp e c t i v e l y .A l t h o u g h a 3 ~ i n c r e as e in s lu d g e T K N w a s o b s e r v e d in th e E T s y s te m s ,a 4 % d e c r e a s e w a s o b s e r v e d o v e r a ll .

W a t e r q u a l i t y p a r a m e t e r s o t h e r t h a n t h e n i t r o g e n o u s c o m p o u n d sw e r e s i m i l a r d u r i n g b o t h s tu d i e s . M e a n w a t e r t e m p e r a t u r e s r a n g e d f r o m


11/19

T r i c k l i n g b i o f i l r e r i n a r e c i r c u l a t i n g s y s t e m f o r c h a n n e l c a r / i s h 492 8 . 7 t o 3 1 - 5 C . T h e f r e e C O : i n c r e a s e d d u r i n g t h e l o a d i n g t ri al s ( 0 . 6 -1 . 9 r a g l it er -I ), b u t d i d n o t a p p r o a c h d e t r i m e n t a l c o n c e n t r a t i o n s( B r o u s s a r d a n d S i m c o , 1 9 7 6 ). M e a n a l k a l in i t y c o n c e n t r a t i o n s s h o w e d am i n o r d e c r e a s e i n r e s p o n s e t o i n c r e a s e d f i l te r v o l u m e a n d f l o w r a t e( 2 5 3 t o 2 2 8 m g l i te r -1 a s C a C O 3 a t p H 4 . 5 ) . A m i n o r r e d u c t i o n ina v e r ag e p H v a l u e s i n r e s p o n s e t o d e n s i t y i n c r e a se s ( 8 -2 t o 7 . 4 ) w a so b s e r v e d . M e a n c o n d u c t i v i t y l ev el s d e c l i n e d w i t h in c r e a se d f l o w ra t e s( 7 0 4 t o 6 7 8 ; ~ m h o c m - t ) . H a r d n e s s ( E D T A ) a v e r a g ed 3 5 0 m g li te r - [ (a sC a C O 3 ), w i t h o u t r e s p o n s e t o f i lt e r v o l u m e o r f l o w r at e.

D i s s o l v ed o x y g e n c o n c e n t r a t i o n s i n a ll t e s t s fe ll b e l o w 3 . 5 m g l it e r - t ,w i t h m o s t s y s t e m s e n d i n g b e l o w 3 . 0 m g li t er - t ( F ig . 2 ) . A s u b s t a n t i a l

6 . 0

5 . 0

- . . 4 . 0O N 3 . 5c:hE 3.0

5 . 0

< 4. 0edO 3 . 5

E 3 .0

F i g . 2 .

o FT

I I I I I I I I [ I I I I I 1 I I2"C 9 14 19 24 28 6 16 21 26 31 5 10 15 20 25 30 5 10F E B R U A R Y I M A R C H I A P R IL [ M A Y

D A T E , 1 9 8 1

6 o ; T ( b )

2.O I I I I I I 1 I I I I I I I I I I J9 14 19 24 28 6 I I 16 21 26 31 5 I0 15 20 25 30 5 I0F E B R U A R Y I M A R C H I A P R IL I M A Y

D A T E , 1 9 8 1Dissolved oxy gen con centra tions (mg O2 liter - t) in the cu lture units duringgrowth trials. (a) 22.7 liters rain-t; (b) 45.4 liters min-L


12/19

50 G. E . M i l l e r . G . S . L ib e yd r o p i n D O w a s o b s e r v e d a c r o ss t h e c l a ri fi e r, w i t h c o n s u m p t i o n r e l a t e dt o f l o w r a t e b u t n o t f i l te r v o l u m e ( .3 5 - 9 0 g O z p e r d a y a t t h e h i g h fl o wr a t e , 3 5 - 6 5 g O 2 p e r d a y a t t h e l o w e r r a t e ).

O x y g e n c o n s u m p t i o n b y m i c r o o r g a n i s m s in s u s p e n si o n w a s i nv e rs el yr e l a te d t o f l o w r a te a n d f il t er v o l u m e . T h e g r e a t e s t c o n s u m p t i o n ( a b o u t3 g O ~ p e r d a y ) w a s i n t h e l o w f l o w r a t e s y s t e m s a n d t h e h i g h f l o w E Ts y st e m . O x y g e n c o n s u m p t i o n b y s u s p e n d e d m i c r o o r g a n i sm s w a s r e d u c e db y u p t o 2 2 % b y c l a r i f i c a t i o n .

A n i t r o g e n m a s s b a l a n c e ( T a b l e 6 ) o f t h e si x s y s t e m s d u r i n g t h eg r o w t h t ri a l i n d i c a t e d t h a t s t a n d p i p e o v e r f l o w w as t h e l a rg e st so u r c e o fn i t r o g e n r e m o v a l . I n s y s te m s w i t h a f il t er m e d i u m , t h e l os s o f n i t r o g e nt o t h e o v e r f l o w w a s 1 1 - 1 8 % g r e a t e r a t t h e h i g h e r f l o w ra t e . I n c r e a s e df i l t e r e f f i c i e n c y w i t h i n c r e a s e d v o l u m e a n d f l o w r a te w e r e r e f l e c t e d b yt h e r e d u c e d i m p o r t a n c e o f a m m o n i a - N o v e r f l o w lo ss . L a r ge r f ee d i n p u tl ev e ls , l o w e r T K N v a l u e s a n d l a N e r w e i g h t g ai n s i n d i c a t e d i m p r o v e ds y s t e m p r o d u c t i o n e f f i c ie n c i e s w i t h i n c r e a s e s i n b o t h f l o w r a te a n df l t e r v o l u m e . L e s s t h a n 0 - 5 % t o t a l a p p l i e d N ( a s a m m o n i a - N , N O ~ - N ,a n d N O ~ - N ) r e m a i n e d i n s o l u t i o n a t t h e e n d o f th e tri als . U n a c c o u n t e d -f o r n i t r o g e n w a s p r o b a b l y d u e t o a c c u m u l a t i o n o f b i om a s s w i th i n th ef il te r s. M e a s u r e m e n t e r ro r s , d e n i t r i f i c a t i o n a n d v a r i a b il i ty i n c o n c e n -t r a t i o n s d u r i n g p e r i o d s b e t w e e n d a t a p o i n t s w e r e a l so l i k el y s o u rc e s o fd i s c r e p a n c y .

D I S C U S S I O NN i t r i f i c a t i o n is n o t t h e o n l y a c t i v i t y t a k i n g p l a c e in t h e b i o f i lt e r . H e t e r o -t r o p h i c b a c te r ia ( t h o s e c o n s u m i n g o r g a n ic s u b s t a n c e s ra t h e r t h a n i n-o r g a n i c c o m p o u n d s ) al so i n h a b i t t h e f i lt er s. H e t e r o t r o p h s h a v e a g r o w t hr a t e a n o r d e r o f m a g n i t u d e l a rg e r t h a n n i t r if i e r s (G r a d y a n d L i r a, 1 9 8 0 ).C o n s e q u e n t l y , n it ri fi e rs w i ll b e o u t c o m p e t e d f o r m e d i u m a t t a c h m e n ts i te s i f t h e c o n c e n t r a t i o n s o f o r g a n ic s u b s t a n c e s ar e s u f f i c i e n t l y h i g h .T h e f i lt e r v o l u m e m u s t b e s u ff i c i e n t to s a t is fy b o t h n e e d s .

I n o u r s t u d y , b y d e s i g n , i n c r e a s i n g t h e f i l t e r v o l u m e i n c r e a s e d t h em e d i u m d e p t h . A s w a t e r p a s s e d t h r o u g h t h e f il te r , or ga ia ic s w e r er e m o v e d b y t h e h e t e r o t r o p h s u n ti l t h e c o n c e n t r a t i o n w a s l o w e n o u g hf o r n i t ri fi e rs t o b e c o m e e s t a b li s h ed . T h e g r e a t e r t h e d e p t h r e m a i n i n ga f t e r t h i s p o i n t , t h e m o r e e f f e c t i v e w a s t h e fi lt e r. G r a d y a n d L i m( 1 9 8 0 ) n o t e t h a t t o t a l t o w e r v o l u m e c a n b e m i n i m i z e d b y s e le c t in g at a l l , t h i n t o w e r r a t h e r t h a n a s h o r t , t a t o n e .


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TABLE6

NoMaBanSxCoCueSemDnGowhTas

2. -

FeFdFd

(kgN (kg

O

OvOvOvO

SuSdFsh

fowfowfowfowfowTKTKwgn

toaamaNONNONtoa(g

{%(kg

NoNolo

loNo

m)

(kg

(%(%(%

(%

in)in)in)in)

Fsh N reFsh

N

NOaoed

(%fo

~

in){% in

)3

27em

E

5331

28

H

6235

22

F

7240

20

44eran-~

E

6236

31

H

6538

28

F

8647

33

25

46

53834

17252

89

19

"~

78

26

50644

16342

82

82

30

1240534

1731

3

90

79

~

10

45

61864

16373

87

19

72

26

60784

13393

88

90

24

08

62664

88494

91

85

tl


14/19

52 G. E. Mil ler, G. S. LibeyThe higher flow rate affected filter effic iency in several ways. Since

the rate of addition of ammonia to the systems can be assumed to beabout equal in all systems, a doubling of the flow rate provided twicethe exposure to the filter. The larger flow rate also provided a greatershear force, reducing the thickness of the microbial film. This lessenedthe distance soluble material had to diffuse, provided a higher concen-tration throughout the microbial film and assured film viability (Gradyand Lira, 1980). It also reduced the size of material being sloughed andlessened the chance of void blockage and channelization.

At the higher flow rate, the FT was capable of stripping 6-25 mgNH3-N h -~ if ambient concentrat ions were 0. l mg NH3-N liter ~ (Millerand Libey, 1983). Based on average ammonia-N and pH values, thesystem was capable of removing only about 2 g NH3-N during the entiregrowth trial through stripping. This supports Burrows and Combs(1968) comment that ammonia removal by stripping is insignificant bycomparison with that by nitrification.

The low DO was apparently a limiting factor in these trials. Carlsone t a l . (1980) determined that channel catfish growth was significantlyreduced at DO levels of 3-5 mg liter-~ or less. During the last sevenweeks the DO levels of all the systems fluctuated around 3.5 mg liter ~.This suggests that the systems could have produced greater biomass hadthe oxygen recharge rates been greater. Production variations amongthe systems support the observation of Thurston e t a l . ( 1 9 8 1 ) thatlevels of NH3-N and NO~--N cur rently considered safe become detri-mental in the presence of low DO. Further research on the effects ofsublethal environmental quality will need to be conducted to confirmthis.A nitrifying filter can consume 150% of the nitrification oxygenrequirement (Gigger and Speece, 1970). Nitrification is oxygen depend-ent, being reduced to half its maximum rate at DO levels as high as2 mg liter 1 (Grady and Lim, 1980). Since 4.5 mg 02 are required tooxidize 1-0 mg ammonia-N to NO~-N, the greater the oxygen rechargecapability of a system, the more capable it will be of providing nitri-fication at rates necessary to support high density cultures. Table 7(Miller and Libey, 1983) provides the oxygen recharge capabilities ofthese systems. By providing more filter media and greater oxygenrecharge capabilities, the FT system could predictably provide largercarrying capacities. The equation

g 02 required h -l = T w t (0.28144CX -~2 + 11-25R) (1)


15/19

T r i c k l i n g b i o f i l t e r i n a r e c i r c u la t i n g s y s t e m f o r c h a n n e l c a t fi s h 5 3

T A B L E 7Com parison o f M ean Values of M ass Transfer Rates (g O2 h 1) For Various ClosedCulture Configurations Und er Standard Cond itions (Tap W ater W ith: Tem perature =20C; Volume = t0 60 liters; DO = 0 .0 ppm ). Values are No t Significantly Different(P> 0-05, Student-Newman-Keuls Multiple Range Analysis) . Supplemental Aeration

Provided b y Surface A gitation ( .0-037 kW)Fi lter HT FT HT ET ET FTFlo w rate (f iters min -x) 22.7 22.7 45-4 22.7 45.4 45.4g O2 h -1 51 .24 56-78 58-16 59.88 63-56 79-13

w a s d e v e l o p e d in p a r t f ro m A n d r e w s a n d M a t su d a ( 1 9 7 5 ) t o p r e d i c t D Or e q u i r e m e n t s in a n a q u a c u l t u r e s y s t e m . T h e e q u a t i o n a c c o u n t s f o r f is hs iz e (a s s u m i n g s i ze u n i f o r m i t y ) , o x y g e n c o n s u m p t i o n b y t h e fi sh a td i f f e re n t D O c o n c e n t r a t i o n s a n d o x y g e n c o n s u m p t i o n b y t h e fi lt er . T h eo x y g e n r e q u i r e m e n t o f t h e f i lt er is b a s e d o n 1 5 0 % o f t h e n i t r if i c a ti o no x y g e n d e m a n d a nd s y s te m a m m o n i a - N p r o d u c t i o n o f 4 0 g k ~ ~ f ee da d d e d ( f r o m n i t ro g e n m a s s b a l a n c e d a t a) . B y e q u a t i n g o x y g e n re c h a rg ec a p a b i l it i es t o t h e o x y g e n r e q u i r e m e n t o f t h e s y s t e m , t h e ca r ry i n gc a p a c i t y c o u l d b e p r e d i c t e d . W a s t e s i n th e w a t e r c a u se a r e d u c t i o n ino x y g e n r e c h a r g e c a p a b i l i t i e s ( A m e r i c a n P u b l i c H e a l t h A s s o c i a t i o n et al.,1 9 8 0 ; C o l t an d T c h o b a n o g l o u s , 1 9 8 1) . W e a v er ( 1 9 8 1 ) f o u n d t h a t fe e dh a d a si g n i f ic a n t e f f e c t o n t h e o x y g e n r e c h a r g e c a p a b i l i t i e s o f v a r i o u sa e r a t i o n t e c h n i q u e s , p r o v i d i n g r e d u c t i o n s b y a s m u c h a s 7 0 % . P a c k e dt o w e r s w e r e m o s t s e n s it iv e . A c o r r e c t i o n f a c t o r ( od o f 0 . 4 4 w a s s u f fi -c i e n t t o p r e d i c t t h e f i n a l l o a d i n g s o f o u r s y s t e m s .

O x y g e n c o n s u m p t i o n b y s u s p e n d e d m i c r o o r g a n is m s w a s r e l at iv e lyi n s ig n i fi c an t . A t h a r v e st t h e 3 . 0 g 0 2 p e r d a y c o n s u m p t i o n m e n t i o n e da b o v e w o u l d a c c o u n t f o r n o m o r e t h an 3 % o f t h e o x y g e n d e m a n d o fa n y o f th e s y s t e m s ( e q n ( 1 ) ; D O = 4 . 0 ; 1 .5 f e e d i n g ra t io ) .

Nitrosomonas s p. a c c o u n t e d f o r 3 0 % o f t h e o x y g e n c o n s u m e d b ys u s p e n d e d m i c r o o r g a n i s m s in t h e c u l t u r e u n i t; 2 0 % a f te r c l ar i fi c at io n .Nitrosomonas s p. u s e 3 . 2 m g 0 2 t o c o n v e r t 1-0 m g a m m o n i a - N t oN O ~ - N ( G r a d y a n d L im , 1 9 8 0) . T h u s , a b o u t 2 8 0 m g a m m o n i a - N p e rd a y w e r e c o n v e r t e d t o N O ~ - - N b y s u s p e n d e d Nitrosomonas sp . i n t hec u l t u re u n it s. O x y g e n c o n s u m p t i o n b y s u s p e n d e d Nitrosomonas sp .a f t e r c l a r i f i c a t io n w a s l es s t h a n 2 0 0 m g p e r c la y w i t h l es s t h a n 6 5 m ga m m o n i a - N p e r d a y c o n v e r t e d t o N O oS-N . T h i s c o r r e s p o n d s t o le ss t h a n4 5 m i n p e r f o r m a n c e b y a n y o f t h e f il te r s.


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54 G. E. Miller, G. S. LibeyAndrews e t a l . (1971) obtained acceptable production with a loading

of 6-6 kg liter 1 min-1 fresh water makeup. Subtracting this, Lewis andBuynak (1976) determined that their RBC systems provided an addi-tional loading of 2 kg m -2 medium surface. Similarly, the FT systemssupported an average of 1.2 kg m -2 and the HT systems 2-2 kg m -2.However, the ET systems supported 70.8 and 78.0 kg without themedium (62-4 and 34.4 kg liter ~ min-~). Biogrowth on othe r surfacesmust also be accounted for to establish the support provided by thefilter medium. Although the ET systems had unacceptable NH3-N andNO~-N levels, the high NO3-N concentrations indicated that consider-able nitrification was occurring within the systems. Using the ETsystems as controls, the average support one basket of medium pro-vided was 3-6 kg (0- 12 kg m-2). The second basket supported an addi-tional 8-9 kg (0-29 kg m-2), 12.5 kg (0-20 kgm -2) being the totalsupport by the FT filters. Even this is a simplistic analysis since it doesnot account for the improved water quality and increased rates ofproduction (1-92, 2.17 and 2-77 kg per week by the ET, HT and FT,respectively).

Raceway culture systems are typically considered high densityoperations (e.g. 160 000 kg m -a s-~; Ray, 1981). However, facil ity wateruse may exceed 265 m 3 min-~. Fresh water makeup in the low flow FTsystem was 1-14 li te rsmin -~ (1-89 X 10 s m 3s -1) supporting a loadgreater than 4.3 million kg m -3 s ~. As the supply of high quality waterdecreases and the demand for it increases, water conservation providedby recirculation systems becomes an attractive alternative to conven-tional culture techniques.

CONCLUSIONSix different recirculating aquaculture systems were tested to determinethe influence of filter volume and recirculation flow rate on waterquality and production capabilities. From the results of this study, weconclude that:

1. channe l catfish densities of 100 g liter ~ (sys tem carrying capacitiesof at least 85 g liter l) with excellent water quality are capable ofbeing produced with recirculating culture systems using packedtowers;


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Trickling biofilter in a recirculating system for channel catfish 552 . p a c k e d t o w e r b i o f ' d t ra t i o n is a f f e c t e d b y fi lt e r v o l u m e , m e d i a d e p t h

a n d f l o w r a t e;3 . a v e r y c l o s e r e l a t io n s h i p e x i s ts b e t w e e n o x y g e n r e c h a rg e c a p ab i li -t ie s , w a t e r q u a l it y , a n d c a r r y i n g c a p a c i t y ;4 . f u r t h e r s t u d i e s a r e n e e d e d o n t h e p h y s i o l o g i c a l c o n c e r t e d e f f e c t s

o f l o w D O . N H 3 - N a n d N O ~ - N l e v el s a n d t h e i n f l u e n c e o f fi shc u l t u r e w a t e r q u a l i t y o n o x y g e n r e c h a r g e c a p a b i l i t i e s .

A C K N O W L E D G M E N T S

T h e a u t h o r s w i s h t o e x p r e s s t h e i r si n c e re a p p r e c i a t i o n t o D r G e o r g e P .M c C a b e o f t h e D e p a r t m e n t o f S ta t i s t ic s , D r J o h n C . N y e o f th e D e p a r t-m e n t o f A g r i c u lt u r al E n g i n ee r i n g , D r A n n e S p a ci e o f th e D e p a r t m e n t o fF o r e s t r y a n d N a t u ra l R e s o u r c e s a n d D r R o n a l d F . W u k a s ch o f t h eS c h o o l o f C i v il E n g i n e e r i n g , P u r d u e U n i v e r s i t y , f o r t h e i r p r e v i e w o f t hi sm a n u s c r i p t a n d v a l u a b l e c r i t i c i s m .

R E F E R E N C E SAm erican Public H ealth Association, Am erican W ater W orks Association & W ater

Pollut ion Control Federat ion (1980) . Standard Methods for the Examination ofWater and Wastewater, 15th edn, American Public Health Association, Washing-ton, DC.

Andrews, J. W. & Matsuda, Y. (1975). The influence of various culture conditionson the ox ygen consu m ption o f channel ca tf ish. Trans. American FisheriesSociety, 1 0 4 , 3 2 2 - 7 .

And rews, J. W ., Knigh t, L. H ., Page, J. W ., M atsuda, Y . & Brown, E. E. (1971).Interact ions o f s tocking densi ty and water turnover on grow th and tbo d con-version o f channel catfish reared in intensively stoc ked tanks. The ProgressiveFish-Culturist, 33 , 197 - 203 .

Brett, J. R. & Zala, C. A. (1975). Daily pattern of nitrogen excretion and oxygenconsumpt ion of sockeye sa lmon (Oncorhynchus nerka) under controlled condi-tions. J. Fisheries Research Board Canada, 32 , 2479- 86 .

Broussard, M. C. Jr & S imco, B. A. (197 6). H igh-density culture o f channel catfishin a recirculating system. The Progressive Fish-Chlturist, 38, 138-41 .Burrows, R . E. & Com bs, B. D. (196 8). Controlled environments for salmon propa-

gation. The Progressive Fish-Culturist, 30, 123-36 .


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56 G. E. Miller, G. S. LibeyCarlson, A. R . , Blocher . J . & Herm an, L. J . (1980 ) . G row th and survival of chan nel

ca t f ish and ye l low perch expo sed to lowered cons tan t and d iurna l ly f luc tua t ingdis so lved o xyg en conc ent ra t ions . The Progressive F ish-Culturist, 42 , 73 - 8 .

Col t , J . & Tchobanoglous , G . (1981) . Des ign of ae ra t ion sys tems for aquacul ture .Proceedings Bio-Engineering Symposium for Fish Culture. eds L. J . A lien an dE. C. Kin ney , Fish C ul ture S ect ion o f the Am erican Fisher ies So cie ty, Washing-t on D C, pp . 138 - 48 .

Col t , J ., Lud wing, R. , T cho bano glous , G . & Cech, J . J. J r (1981) . The effects o fn i t r i te o n the shor t - t e rm grow th an d surv ival o f cha nne l ca t f i sh , lctalurus punc-tatus. Aqua culture , 24, 111-22 .

Emerson, K. , Russo, R. C. , Lund, R. E. & Thurs ton. R. V. (1975) . Aqueousam mo nia equi l ib r ium ca lcu la tions : e f fec t s o f pH and t emp era ture . J . FisheriesResearch Board Canada, 32 , 2379 - 83 .Gigger . R. P . & Speece, R. E. (197 0) . T rea tm ent of f i sh ha tch ery eff lue nt for re-cycle . Engineering E xpe rim ent Stat ion, Technical Rep ort No. 6 7, New MexicoState Universi ty, I .as Cruces.

Grady, C. P. L. Jr & Lira, H. C. (1980). Biological Wastewater Treatment Theoryand Applications, Marcel Dekker , New York.

Lewis , W. M. & Buynak. G. L. (1976) . Evaluat ion of a revolving pla te type bio-f i l ter for use in rec i rcula ted f ish pro du ct io n and hold ing uni ts . Trans. Am ericanFisheries So ciety , 1 0 5 , 7 0 4 - 8 .

Mil ler. G. E. & Libey , G. S . (1983) . Ox ygen recharge and am m on ia s tr ipping capa-bi l i t ies of var ious c losed cul ture configurat ions . Aquacultural Engineering, 2,263- 79 .

Muir , J . F . ( ! 981). M anagem ent an d co s t imp l icat ions in rec i rcula t ing wa ter sys tems.Proceedings Bio-Engineering Symposium for Fish Culture , eds L. J . Allen an dE. C. Kinn ey, Fish C ul ture S ect ion o f the Am erican Fisher ies So cie ty, Washing-ton DC, pp . 116-27 .

Nelson, D. W. & Som mers , L. E. (1972) . A s imple diges t ion proced ure for es t ima-t ion of to t a l n i t rogen in soi ls and sed im ent s . J. Environmental Quality, 1 , 4 2 3 - 5 .

Ray , L . (1981) . Channe l ca t f i sh produc t ion in geo the rmal wa te r . Proceedings Bio-Engineering Symposium for Fish Culture , eds L. J . Allen and E. C. Kinney, FishCul ture Sec t ion of the Am er ican F i she r ie s Soc ie ty , W ashington DC, pp . 192-5 .

Robine t t e , H . R. (1976) . Ef fec t o f s e l ec ted suble tha l l eve l s o f ammonia on thegrowth of channe l ca t f i sh (lctalurus punctatus). The Progressive Fish-Culturist,38 , 26 - 9 .Ru ane, R. J . , Ch u, T. Y. J . & Van dergr i f f , V. E. (1977) . Ch aracter iza t io n and t rea t -m ent o f was te d i scharged f rom h igh-dens i ty ca tf i sh cu ltu res . WaterResearch, 11,789- 800 .

Stellmacher, M. (1981 ). Aquacul ture Ou t look and S i tua t ion , U S D A E c onom i c s a ndStatis t ics Service, National Economics Division, Washington DC.


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Trickl ing biof i l ter in a recircularing sys te m fo r chann el catf ish 57T hu rs to n, R. V., Phillips, G. R., Russ. R . C. & Hin kins, S. M. (1 98 1) . Increasing

t o x i c it y o f a m m o n i a t o r a i n b o w t r o u t (Sa lmo ga irdner i) re su l t ing f rom reducedc 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 . Canadian J . Fisher ies a nd Aqu atic Sciences ,3 8 , 9 8 3 - 8 .

Weaver , D. E . (1981) . The im pac t o f f i sh feed on oxyg en t ranspo r t . World Marl-cu l ture Soc ie ty Technica l Sess ion , Sea t t l e , Washing ton .

Documents

Miller 1984 Aquacultural-Engineering