anderson 1982 aquacultural-engineering

7/28/2019 Anderson 1982 Aquacultural-Engineering

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Aquacultural Engineering 1 (1982) 205-214

C O N T I N U O U S P R O D U C T I O N O F M I C R O A L G A E U S IN GA SCOURING FILM REACT OR

T. H. ANDERSONBlack & Veateh Consulting Engineers, Walnut Creek, California, USA

andD. E. BRUNE

Department o f Agricultural Engineering, Pennsylvania State University, University Park,Pennsylvania 16802, USA

ABSTRA CTA new system for the continuous production ofmicroalgae is described and data froma series o f trial runs are presented. This system, termed the Scouring Film Reactor(SFR) is simple and inexpensive to construct and is operated by compressed air alone.This device utilizes a continuously scouring f ilm of glass particles to prevent wallgrowth and algal settling. Tests o f continuous algae production were conducted with a40 fitre SFR and a non-scoured reactor of similar size, using the marine alga Phaeo-dactylum tricornutum. Over a five-week period, production o f algae from the SFR wasreliable and required no maintenance. Production from the non-scoured reactor wassubject to crashes and required a high degree of maintenance.

INTRODUCTIONThe uncertain reliability of algal cell production systems continues to pose a problemfor many aquaculture operations in which single cell algae is the primary feed sourcefor filter feeding aquatic organisms. Many other areas of research and developmentrequiring continuous algal cell production also experience difficulty in meeting needs.

Droop (1975) compares the use of batch and continuous systems for the produc-tion of microalgae. Continuous systems are shown to be advantageous over batchbecause: (1) the product is of constant composition and physiological state; (2) rates

205Aquacultural Engineering 0144-8609[82/0001-0205/S02.75 Appfied Science Publishers Ltd,England, 1982Printed in Great Britain


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206 T . H . A N D E R S O N , D . E . B R U N Eof production per volume are higher; and (3) less labour is required. Despite theseadvantages, however, batch culture is by far the more common method used in algaeculture today.

One of the main reasons for the prevalence of batch culture is that, even on alaboratory scale, non-sterile, continuous cultures have seldom been operated at asteady state for long periods of time. Often, the concentration of algae in the outf lowof the reactor drops with time, a phenomenon known as a 'crash'. Algal crashes areattributed to autoflocculation and settling (Ryther, 1976), wall growth (Brune e t a l . ,1978), and in situations in which the influent water is not filtered or sterilized, or thereactor not enclosed, predation may be a factor (Ansell e t a l . , 1963).

A variety of reactors have been used for the continuous production of algae, manyof which have some provision for solving the settling or wall growth problenrs. Solu-tion of the settling problem is usually accomplished by energy input to the media inthe form of mechanical agitation (Brewer and Goldman, 1976) or compressed air(Mock and Murphy, 1970). Solution of the wall growth problem is accomplished bymanual scraping (Dunstan and Menzel, 1971) or the more usual periodic draining,cleaning and refilling the reactor (Canzonier and Brunetti, 1975). Taub and Dollar(1968) used modified Erlenmeyer flasks containing glass beads in the continuousproduction of algae for periods of up to four months. Continuous shaking of tilereactor and subsequent scraping by the beads prevented settling and wall growth onthe bottom surface. Occasional vigorous swirling prevented wall growth on the sidewalls.

In the work presented here, settling and wall growth are prevented by using areactor in which the walls are continuously and automatically scoured by a flowingfilm of glass beads. Experiments were conducted to compare the cell productioncharacteristics of the Scouring Film Reactor (SFR) with a non-scoured continuousstirred tank reactor (NCSTR).

D E S I G N M E T H O D S A N D M A T E R I A L S

Figures 1, 2 and 3 give a detailed view of the construction of the Scouring FilmReactor unit (SFR). The SFR consists of three basic components; a tapered trans-lucent fibre-glass cone, an air lift recircutation loop and a rotary distribution arm.

The tapered cone was fabricated from 0-025 in thick 'sun-lite' fibre-glass solarglazing material obtained from the Kalwall Corporation. The cone was equipped withtwo ~ in marine plywood supports and a plywood flange for attachment to a mouldedfibre-glass outlet. The recirculation loop consists of a }in clear plastic pipe ('Excelon')with a ~in PVC valve and drain tube. Approximately 3 in above the outlet level, theloop is equipped with an air injection port to supply the air lift action. The outlet ofthe loop is centred over the cone and supported by 'Plexiglas' struts. The rotarydistribution arm consists of in PVC pipe, counter balanced and suspended from a


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S C O U R I N G F I L M R E A C T O R F O R M I C R O A L G A E P R O D U C T I O N 207

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F i g. 3 . T o p v i ew o f S c o u r i n g F i l m R e a c t o r d i s t r i b u t i o n a r m .


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SCOURING FILM REACTOR FOR MICROALGAE PRODUCTION 2 0 9s t a i n le s s s t e el s w i vel c o nn e c t e d t o t h e i n l e t p i pe . D e t a i ls o f t h e a r m a r e g i ve n i n F i g s2 a nd 3 .Trial runs with SFR and NCSTR

F i g u r e 4 s h o w s a s c h e m a t i c d i a g r a m c o m p a r i n g t h e o p e r a t i o n o f t h e s c o u r i n g f il mr e a c t o r a n d t h e n o n - s c o u r e d r e a c t o r .

T h e o p e r a t i o n o f t h e S F R u n i t c o n s i st e d o f a d d in g 1 2 5 m l o f 1 0 0 / ~ m g la ss b e a d s ,o b t a i n e d f r o m t h e F e r r o C o m p a n y , a n d i n j e c ti n g c o m p r e s s e d a i r a t a s u f f i c i e n t r a t e t om a i n t a i n a w a t e r f l o w r a t e o f a p p r o x i m a t e l y 4 l i t re s / m i n t o t h e d i s t r ib u t i o n a r m . As l u r r y o f g la ss b e a d s a n d a lg a e f l o w i n t o t h e e x t e r n a l a i r l i f t p u m p a n d a r e t r a n s p o r t e dt o t h e d i s t r i b u t i o n a r m . D i s c h ar g e a t a 4 5 a n g l e f r o m t h e e n d o f t h e d i s t r i b u t i o n a r mc a us e s it t o r o t a t e . T h e be a d s a nd a l ga e a re t h e n d i s t r i b u t e d a l ong t h e w a ll w h e r e t h eb e a d s s e t tl e r a p i d l y , c r e a t i n g s c o u r i n g a c ti o n a l o n g a ll w e t t e d s u r fa c e s . T h e b e a d s r e a c ht h e b o t t o m o f t he r e a c to r a n d r e c y cl e . I n c o n t r a s t , t h e N C S T R c o n s i st e d s i m p l y o f ac y l i n d r i c a l ' P l e x ig l a s ' c o l u m n 122 } n in d i a m e t e r . M i x in g w a s a c h i e v e d b y a e r a t i o n w i t ha n a i r s t one .

B o t h t h e S F R a n d N C S T R w e r e o p e r a t e d a s c o n t i n u o u s c u l t u r e s f o r a p e r i o d o f f iv ew e e k s . A l l p u m p i n g w a s d o n e u s i n g a p e r i s ta l t ic p u m p ( C o l e P a r m e r M a s t e rf l e x ). I n

- ~ - ~ _ - _ - - ,

=o o

- - 2 - - - _ _ _. I

N E S T R

' ~ A i r i n p u tO i s t r i b u

a r m

L i g h tS 0 u f c e

.o

~ D i f f u s e r

,

0

S F R

E x t e r n Q l o i r[ i f t p u m p

Fig. 4. Schematic diagram of Scouring Film Reactor (SFR) and Non-scoured Cont inuo us StirredTank Reactor (NCSTR).


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2 1 0 T . H . A N D E R S O N , D . E . B R U N E

both reactors the inflow and outflow rates were held constant so that the volumeremained constant at any given time. The dilution rate of the NCSTR was started at0.33/ day for the first few days and then adjus ted to 0.5/day by changing the volumefrom 52 litres to 34.5 litres. Flow rate was consta nt at 17-28 litre s/day. The initialdilu tion rate of the SFR was 0.67/day. Aft er a few days, this was changed to 0.44/ dayby changing the flow rate from 26.3 litres/day to 17-28 litres/day. The volume washeld constant at 39.5 litres.T h e a l ga l m e d i a a n d c u l t u r e c o n d it i o n s

The algal culture media is presented in Table 1. The media was formulated toclosely resemble the ionic c omposi tion of seawater. The salinity, however, was28 parts per thous and. Carbon, nitro gen, and phosphorus levels were as given, excepton Day 7 of the SFR run, in which they were doubled. The media was filtered to3- 5/ l m before use. Light levels were consta nt at 27-2 9 W/rn z (40 0-5 00 ft-c) at theliquid surface. The light source was a bank of 40 W 'daylight' fluorescent lamps. Thetemperature was mainta ined constant at 23C.

The cultures were inocula ted with a seed culture using the marine diatom P h a e o -d a c t y l u r n t r i c o r n u t u m (University of Texas Culture Collection #2089). It should benoted that both the SFR and NCSTR cultures were completely open to the environ-ment. This was done in an attempt to study the behaviour of the cultures under whatwere, basically, field conditions. Tire NCSTR reactor was subject to frequent 'crashes'

TABLE 1Composition of artificial seawater mediaSal t Concentra t ion {g/l itre)

NaCI 20.91MgSO4 7H~O 5.70MgCI2 6t{20 4-17CaC12 0.94KCI 0.61NaHCO3 0.63K~HPO4 0-08Na2SiO3 9H20 0-01NaBr 0.071H3BO3 0.019FeC13 . 6H20 0.001 5NH4C1 0.03Na2EDTA 0.05MnC12 4H20 0-001 86ZnSO4 7H20 0-000 20(NH4)6 Mo70~4 0-000 20CuSO4 0-000 05Co(NO3)2 6H20 0.000 49Salinity 28 ppt


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S C O U R I N G F I L M R E A C T O R F O R M I C R O A L G A E P R O D U C T I O N 211s o t h a t i t b e c a m e n e c e s s a r y t o m a i n t a i n b a c k - u p b a t c h c u l t u r e s o f al g ae . W h e n a c r a s ho c c u r r e d , t h e r e a c t o r w a s d r a i n e d , c l e a n e d , a n d r e - s t a r t e d b y f i ll in g i t w i t h a l g a e f r o mt h e b a t c h c u l t u r e s .

R E S U L T S A N D D I S C U S S I O N

T h e r e s u lt s o f 4 0 d a y s o f c o n t i n u o u s a l ga e c u lt u r e i n b o t h t h e S F R a n d N C S T R a reg i ve n in F i g . 5 . It c a n b e s e e n t h a t t h e p r o d u c t i o n o f a l ga e i n t h e S F R i s m u c h m o r er e l ia b l e t h a n t h a t i n t h e N C S T R . I n a d d i t i o n , th e S F R r e q u i r e d n o m a i n t e n a n c et h r o u g h o u t t h e t h e t e s t in g p e r i o d , w h i l e t h e N C S T R n e e d e d f r e q u e n t c l e a n i n g , a s w e l la s m a i n t e n a n c e o f b a t c h a l ga e c u l tu r e s t o r e s t a r t t h e r e a c t o r a f t e r a cr a s h.

T h e s p e c ie s c o m p o s i t i o n i n th e N C S T R w a s m a i n l y P . t r i c o r n u t u m . A n o c c a s i o n a lg r e e n f l a g e ll a te w a s a l s o o b s e r v e d . I n a d d i t i o n , a m o e b a e w e r e u s u a l l y p r e s e n t i n th eN C S T R , s o m e t i m e s i n n u m b e r s a s g r e a t a s 3 0 0 0 0 / m l . T h e a m o e b a e w e r e o f t e nc o a t e d w i t h P . t r i c o r n u t u m . A l g a e w h i c h a d h e r e d t o t h e a m o e b a e a p p e a r e d tod e c o m p o s e , a n d a s in g le a m o e b a p r o b a b l y h a d a s m a n y a s 5 0 c e ll s a t t a c h e d t o it a ta n y o n e t im e . S p e c i e s c o m p o s i t i o n i n th e S F R w a s a l m o s t u n i f o r m l y P . t r i e o r n u t u m ,a l t h o u g h t h e s a m e g r e e n f l a g e ll a te w a s o c c a s i o n a l l y o b s e r v e d . W h e n p r e s e n t , i n b o t ht h e S F R a n d t h e N C S T R , t h i s fl a g e ll a t e a c c o u n t e d f o r l es s t h a n 0 . 5% o f t h e b i o m a s s .N o a m o e b a e w e r e e ve r o b s e r v e d in t h e S F R .

I n t h e N C S T R , w a l l g r o w t h a n d s e d i m e n t a t i o n w e r e u s u a l ly a p p a r e n t w i t h i n a d a ya f t e r e a c h s t a r t - u p . B o t h w o u l d b e c o m e e x t e n s i v e w i t h i n t h r e e d a y s o f s t a r t - u p . I n t h eS F R , n o s e d i m e n t a t i o n e v e r o c c u r r e d . A f t e r a p e r i o d o f s ev e r al d a y s a c a l c iu mc a r b o n a t e s c a le o c c u r r e d o n t h e w a l ls o f b o t h r e a c t o r s . O n t h e N C S T R t h i s d e p o s i t w a sr i n s e d o f f w i t h d i l u t e a c id e a c h ti m e t h e r e a c t o r w a s c l ea n e d . O n t h e S F R , h o w e v e r ,

oz SFR - - Ju.J~- ! i ! ~ NCST# /

O O0 5 IO 115 2 ; 25 30 315T i M E, DAYS

I4O

Fig . 5 . Alga l co n cen t ra t i o n f ro m b o th SFR an d NCS TR fo r 40 d ay p e r i o d .


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2 1 2 T . H . A N D E R S O N , D . E . B R U N Et h e s ca le b u i lt u p t h r o u g h o u t t h e r u n . O n D a y 3 0 a f i l a m e n t o u s b l u e- g r ee n b a c t e r i u mb e g a n t o g r o w o n t h e w a ll s o f t h e S F R . B y D a y 3 5 , t h e g r o w t h o f th e b l u e - g re e nm a t t e r h a d b e c o m e e x t e n s iv e , b l o c k i n g m u c h o f t h e i n c o m i n g li g h t a n d r e s u l ti n g in t h eg r a dua l de c l i ne i n Phaeodactylum c el l c o u n t s e en a t t h e e n d o f th e r u n . I r r e g u l a r i ty o ft h e s u r f a c e o f t h e s ca le is p r o b a b l y t h e r e a so n f o r e s t a b l is h m e n t o f t h e b l u e - g re e nb a c t e r i u m , s in c e t h e b e a d s w e r e n o t a b l e t o re m o v e t h e s c al e f r o m t h e r e a c t o r s u r f a ce .O n D a y 3 3 o f t h e S F R r u n , s o m e o f t h e s ca le w a s sc r a p e d o f f t h e w a ll a n d , s u b s e q u e n tt o t h i s , th e b l u e - g r e e n b a c t e r i u m w a s n o t a b l e t o g r o w i n t h a t a r e a .

T h e c a u se o f t h e g r a d u a l d e c a y o f p r o d u c t i o n f r o m t h e S F R w a s a t t r ib u t e d t o th iss ca le b u i l d - u p . C o n s i d e r i n g t h e h a r d n e s s o f s e a w a t e r a n d t h e e le v a t e d p H a s so c i a t e dw i t h a lg a e c u l t u r e , t h i s m a y b e a n u n a v o i d a b l e p r o b l e n r f o r m a r i n e a l ga e a p p l i c a t i o n s .I t i s a n t i c i p a t e d , h ow e ve r , t h a t l a r ge r s c a le ve r s i ons o f t h e S F R w i ll h a ve m uc h l e sss l o p e , an d t h a t t h e l ig h t w o u l d c o m e t h r o u g h t h e t o p o f t h e r e a c t o r . T h i s m i g h te l i m i n a t e t h e g r a d u a l d e cr e a s e i n p r o d u c t i o n c a u s e d b y t h e d e c r e a s in g p e n e t r a t i o n o fl i g h t t h r o u g h t h e r e a c t o r w a l l s .

W h i le t h e S F R e x p e r i e n c e d a sl o w d e c l in e i n ce ll p r o d u c t i o n , t h e N C S T R w a su n d e r g o i n g d r a s t ic a lg a l ce ll d e c li n e s e v e r y 4 - 5 d a y s , r e q u i r i n g a c o m p l e t e r e s t a rt o ft h e c u l t u r e o f th e s e i n te r v a ls . A c l o s e r e x a m i n a t i o n o f d a t a f r o m o n e N C S T R r u n( F i g . 6 ) s h o w s t h a t t h e c el l c o n c e n t r a t i o n w o u l d r e a c h a p e a k a n d t h e n d e c l i n ee x p o n e n t i a l ly a s i f t h e c o n t i n u o u s c u l t u r e w e r e w a s h i n g -o u t .

z"O13EI - -ZW(..)Z0

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Fig. 6.

5 0 -

k C e= C oe (/z- - D kd ) f_/.~.-D- k =- 0. 24 d I4030 ~ CO =4 6.9 rng/.~

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0 1 I I I I I I I I I I I26 27 28 29 30 31 32 33 34 35 36 37 38T I ME, DAYSDeclining ce ll prod uct ion in Non-scoured C ontinuo us St ir red Tank Reactor .


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S C O U R I N G F I L M R E A C T O R F O R M I C R O A L G A E P R O D U C T I O N 2 1 3

A b e t t e r u n d e r s t a n d i n g o f t h is s i t u a t io n m a y b e d e v e l o p e d b y e x a m i n i n g a m a s sb a l a n c e o n t h e a l g a l c e ll c o n c e n t r a t i o n i n th e r e a c t o r :

R a t e o f = R a t e f R a t e o f + R a t e o f _ R a t e o fa c c u m u l a t io n i n f lo w o u t f l o w g r o w t h d e c a yo r s y m b o l i c a l ly :

d C- - = DCo - - DC + 1 2 a C - - kdCd t (1 )

w h e r e , C = e f f l u e n t a l g a l c e l l c o n c e n t r a t i o n , C o = i n f l u e n t a l g a l c e l l c o n c e n t r a t i o n = 0 ,D = d i l u t i o n r a t e , ~ a = a l g a l s p e c i f i c g r o w t h r a t e , a n d k d = a l g a l c e l l d e c a y r a t e .

I n t h e c a s e w h e r e C o = 0 , e q n ( 1 ) m a y b e w r i t t e n a s :d C- - = [ U a - - D - - kd ] C ( 2 )d t

w h e r e , C = c o n c e n t r a t i o n a t t i m e t , a n d C i = i n i t ia l c o n c e n t r a t i o n .I f I a a , D a n d k d a r e a ss u m e d c o n s t a n t , t h e s o l u t i o n t o e q n ( 2 ) is :

C : C i e [ u a - D - k a t t ( 3 )T h i s e q u a t i o n s h o w s t h a t a s l o n g a s th e m a x i m m n s p e c i f ic g r o w t h r a t e o f t h e a lg a e

i s g r e a t e r t h a n t h e c o m b i n e d a lg a l d e c a y r a t e a n d d i l u t io n r a t e l o s se s , t h e n t h e c u l t u r ec e l l d e n s i t y w i l l r e m a i n s t a b l e . H o w e v e r , s h o u l d t h e s u m o f k d a n d D e x c e e d t l a , t h e nt h e c u l t u r e w i ll b e g i n t o w a s h - o u t . D u r i n g a ll r u n s w i t h t h e N C S T R , t h e d i l u t i o n r a t ew a s w e l l b e l o w t h e g r o w t h r a t e o f th e d i a t o m P h a e o d a c t y l u m . A p p a r e n t l y , th e d e c a yr a t e o f t h e a lg a l c el ls in c r e a s e d a s a r e s u l t o f p r e d a t i o n b y t h e e v e r - p r e s e n t a m o e b a e i nt h e N C S T R . A t t h e p o i n t w h e r e k a > # a - - D , c e ll w a s h - o u t o c c u r s a n d t h e c o n c e n t r a -t i o n o f a l g ae in t h e r e a c t o r i s s e e n t o d e c a y e x p o n e n t i a l l y w i t h t i m e , a s i ll u s t r a t e d i nF i g . 5 .

T h e p r e s e n ce o f th e a m o e b a e i n t he N C S T R a n d n o t i n t h e S F R c a n p r o b a b l y b ee x p l a i n e d b y c o n s i d e r i n g a m a s s b a l a n c e o f t h e a m o e b a e i n b o t h r e a c t o r s . I f t h es p e c i f ic g r o w t h r a t e o f t h e a m o e b a e is l e ss t h a n t h e d i l u t i o n r a t e o f e i t h e r r e a c t o r ,t h e o r e t i c a l l y , t h e a m o e b a e s h o u l d w a s h - o u t . A s e x p e c t e d , i t w a s n o t p r e s e n t i n t h eS F R . H o w e v e r , i n t h e N C S T R , t h e w a l l g r o w t h a n d s e d i m e n t a t i o n p r o v i d e a n e c o -l o g ic a l n i c h e f o r t h e a m o e b a e . T h e e f f e c t iv e d i l u t i o n r a t e o f t h e a m o e b a e is t h e r e f o r ev e r y l o w a n d w a s h - o u t w o u l d n o t o c c u r . T h i s l e d t o in s t a b i l i t y i n t h e a lg a l p o p u l a t i o nin t he N C S T R .

S U M M A R Y

T h e u s e o f a s c o u r in g f i lm o f f i n e - d i a m e t e r g la s s p a r t i c l e s a p p e a r s t o b e a v e r y u s e f u lt e c h n i q u e i n e l i m i n a t i n g w a l l g r o w t h a n d b i o f o u l i n g i n t h e m a r i n e s y s t e m d e s c r i b e d .


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2 1 4 1 :. H . A N D E R S O N , D . E . B R U N ET h i s c o n c e p t h a s b e e n p r e v i o u s l y d e m o n s t r a t e d t o b e q u i te u se f u l i n m a i n t a i n i n gs y s t e m c l e a n l in e s s in a q u a t i c a n i m a l c u l t u r e u n i t s ( B r u n e , i n p r e s s ).

B y e l i m i n a t i n g t h e w a l l g r o w t h w h i c h h a r b o u r e d a lg a l p r e d a t o r s , t hi s t e c h n i q u eh a s a l l o w e d f o r a s t a b le a n d r e l ia b l e m e a n s o f p r o d u c i n g a lg a l c e l l b i o m a s s . T h e u s eo f s c o u r i n g f i lm s i s a r e la t i v e ly s im p l e a n d e c o n o m i c a l m e t h o d o f in h i b i t in g b i o f i h na n d b i o f o u l i n g p r o b l e m s i n a q u a t i c c u l t u r e s y s t e m s .

R E F E R E N C E SA n s e l l, A . D . , R aym o n t , J . E . G . , L an d e r , K . F . , Cro w l ey , E . & Shack l ey , P . (1 963 ) . S t u d i e s o n t hem as s cu l t u r e o f P h a e o d a e t y l u m . I I . T he g ro w t h o f P h a e o d a c t y l um an d o t he r s p ec i es in o u t d o o rtanks . L i m n o l . O c e a n o g r . , 8 , 1 8 4 -2 0 6 .Brew er , P . G . & G o l d m an , J . C . (1 976) . A l ka l i n i t y chan g es g en e ra t ed b y p hy t o p l an k t o n g ro w t h .L i m n o l . O c e a n o g r . , 2 1 , 1 0 8 - 1 7 .Bru n e , D . E . D es ig n an d d ev e l o p m e n t o f a f l o w i n g b ed r ea c t o r fo r b r i n e s h r im p cu l t u r e . A q u a -c u l t u r a l E n g i n e e r i n g , 1 , 63 -70 .Bru n e , D . E . , N o v ak , J . T . & M an n eb ach , R . (1 978 ) . Qu an t i fy i n g a lg a l c a rb o n u p t ake k i n e t ic s . Ap a p e r p r e s e n t e d t o t h e F i f t i e t h A n n u a l W a t e r P o l lu t i o n C o n t r o l F e d e r a t i o n C o n f e r e n c e .Can z o n i e r , W . J . & Bru n e t t i, R . (1 975) . L o w co s t co n t i n u o u s a lg a l cu l t u r e s y s tem , l O t h E u r o p e a nS y m p o s i u m o n M a r i n e B i o l o g y , O s t en d , Be l g iu m , 1 7 -2 3 Sep t em b er 1 975 , Vo l 1 0 , 2 7 -3 1 .D ro o p , M . R . (1 975) . T he chem o s t a t i n m ar i cu l t u r e , l O t h E u r o p e a n S y m p o s i u m o n M a r i neB i o l o g y , O s t en d , Be l g i u m , 1 7 -2 3 Sep t em b er 1 975 , Vo l . 1 , 71 -93 .D u n s t an , W . M . & M en z e l , D . W . (1 971 ) . C o n t i n u o u s cu l t u re s o f n a t u ra l p o p u l a t i o n s o f p hy t o -p l an k t o n i n d i l u t e , t rea t ed s ew ag e e f f l u en t . L i m n o l . O c e a n o g r . , 1 6 , 62 3 -3 2 .M o ck , C . R . & M u rp hy , M . A . (1 970 ) . T echn i qu es fo r r a i s i n g p en ae i d s h r i m p f ro m t he eg g t opos t l a rvae . In : P r o ce e d i n g s o f t h e F i r s t A n n u a l W o r k s h o p o f t h e W o r ld M a r i cu l t u re S oe i e O , ,

B a t o n R o u g e , L a ., U S A , 9 - 1 0 F e b r u a r y 1 9 7 0 , p p . 1 4 3 - 5 6 .Ry t he r , J . H . (1 976) . M ar i n e p o l ycu l t u r e b a sed o n n a t u ra l f o o d cha i n s an d r ecyc l ed w as t e s . SeaG ran t T echn i ca l Rep o r t . U n p u b l i s hed m an u s c r i p t .T au b , F . A . & D o l l a r , A . M . (1 968 ) . Im p ro v em en t o f a co n t i n u o u s cu l t u r e ap p a ra t u s fo r l o n g -t e rm u s e . A p p l . M i c r o b i o l . , 1 6 , 2 3 2 -5 .

anderson 1982 aquacultural-engineering

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