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G R 8 0 I

H I G H R T E G R V I T Y S N DF IL T R T IO N O F W T E RT O R E M O V E F IS H E G G S

N D L R V E

e~ . . . ~ J ra l a n d A r c h i t e c t u r a l B r a n c hD i v i s i o n o D e s i g n

a n dH y d r a u l i c s B r a n c h

D i v is io n o f G e n e r a l R e s e a rc h~ e e r i n g a n d R e s e a r c h C e n t e r

B u r e a u o f R e c l a m a t io nN o v e m b e r 1 9 7 9

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M 8 - 2 3 0 1 - 7 6 )B u r e a u o f R e c l a m a t i o n

L ~ J L ~ U ~ J J L4, TITL E AND SUBTI TLE

H i g h R a t e G r a v i t y S a n d F i l t r a t io n o f W a t e r t oR e m o v e F i s h E g g s a n d L a r v a e

7. AUTHOR(S)W a y n e F . L o r e n z

9. PERFORMING ORGAN IZAT ION NAME AND ADDRESSB u r e a u o f R e c l a m a t i o nE n g i n e e r i n g a n d R e s e a r c h C e n t e rD e n v e r , C o l o r a d o 8 0 2 2 5

12. SPONSORING AGENCY NAME AND ADDRESS

T E C H N I C L R E P O R T S T N D R D T I T L E P G E3. RECIP IENT S CATALO G NO,

5. REPORT DATEN o v e m b e r 1 9 7 96, PE RFORMING ORGAN IZAT ION CODE

8. PERFORMING ORGANIZATIONREPORT NO.G R - 8 0 - I

10. WORK UNI T NO.

1 1. CON TRA CT OR GRANT NO.

13. T YPE OF REPORT AND PERIODCOVERED

14. SPONSORING AGENC Y CODE

15. SUPPLEMENTARY NOTES

16. ABSTRACTA m e t h o d f o r p r e v e n t i n g i n t e r r i v e r d r a i n a g e b a s i n t r a n s f e r o f f i s h , f i s h e g g s , a n df i s h l a r v a e is r e q u i r e d a t t h e p r o p o s e d L o n e t r e e R e s e r v o i r o u t l e t w o r k s . A l im i t e ds t u d y o f h i g h r a t e g r a v i t y s a n d f i l t r a t io n w a s c o n d u c t e d i n a l a b o r a t o r y m o d e l t o i n -v e s t i g a te t h e r e q u i r e d p a r a m e t e r s f o r re m o v i n g f i s h e gg s a n d l a r v a e f r o m a f lo w o fw a t e r . L i v e f i s h e g g s a n d l a r v a e o f t h e c o m m o n c a r p a n d r a i n b o w s m e l t w e r eapp l i ed t o t wo s epa r a t e f i l t e r s , one con t a i n i ng an e f f ec t i ve s i z e s and o f 0 . 425 t o0 . 500 mm 0 . 017 to 0 .020 i n ) an d t he o t he r ha v i n g an e ff ec t i ve s i ze s an d o f 1 . 20 t o1 . 70 m m 0 . 047 t o 0 . 067 i n ) . Th e f i l t r a t i on r a t e was he l d con s t an t a t 6 . 79 x 10 -3 m / s1 0 g a l / m i n ) / f t ~) t h r o u g h b o t h f i l te r s . F i s h e g g s p r e s e r v e d i n f o r m a l d e h y d e w e r eus ed a f t e r t he s pawn i ng s ea s on o f t he f i s h . The f i l t e r w i t h e f f ec t i ve s and s i z e o f0 . 4 25 t o 0 . 5 0 0 m m w a s s u c c e s s f u l i n p r e v e n t i n g t h e p a s s a g e o f t h e e g g s a n d l a r v a ei n t h e f il t r a t io n m o d e . L a r v a e w e r e s u f f i c ie n t l y m o t i l e to p a s s t h r o u g h t h e v o i d s int h e f i lt e r w i t h t h e l a r g e r s iz e s a n d . H e a d l o ss e s a n d b a c k w a s h r a t e s f o r th e f i l te r swe r e a l s o i nves t i ga t ed .

17. KEY WORDS AND DOCUMENT A NAL YSISo. D E S C R I P T O R S - - / * f i l t r a t i o n / h e a d l o s s e s/ s a n d f i l t e r s / f i s h h a n dl in gf a c i l i t i es / f i s h e g g s / s p a w n i n g / m o d e l s t u d ie s / f i s h m i g r a t i o n / b a c k w a s h

b I D E N T I F I E R S - - / L o n e t r e e D a m , N . D a k . / L o n e t r e e R e s er vo ir o u t l et w o rk sc. COSATIField~Croup I 3 M COWRR: 1313.118. DISTRIBUTIONSTATEMENT 119. SECUR_I_TY_CLASS21. NO. OF PAGE:(THIS REPORT) I ~ ~UNCLA SSIFIED20. SECURITY CLASS 22. PRICE(THIS PAGE)

UNCL SSIFIED

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SI METRI

G R - 8 0 - 1

H I G H R A TE G R A V I T Y S A N DF I LT R A T I O N O F W A T E RT O R E M O V E F I S H E G G S

A N D L A R V A E

byWayne F. Lorenz

Structural and Arch itectu ral BranchDivision of Design

and H ydrau lics BranchDivision of Research

Engineering and R esearch CenterDenver, Colorado

Revised R eprint March1980

UNITED ST TES DEP RTMENT OF THE INTERIOR BURE U OF RECL M TION

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ACKNOWLEDGMENTS

This investigation was conducted under the generalsupervision of W. R. Anderson, Chief, Structural andArchitectural Branch and D. L. King, Chief,Hydraulics Branch. The support of the EnvironmentalSciences Section in providing the live fish eggs and lar-vae is gratefully acknowledged. Special thanks are dueto R. A. Roline for his constant attention to the spawn-ing fish; to T. J. Isbester and R. W. Schiller for theirassistance in building the models; to K. W. Frizell forhis assistance in data recording; and to W. R. Anderson,C. F.~Hunt UM region), P. L. Johnson, H. T. Jong,and D. L. King for their review and comments.

On Novembe r 6 1979 the Bureau of Reclamat ion wasrenamed the Water and Power Resources Service in theU.S. Department of the Interior. The new name moreclosely identifies the agency with its principalfunctions-- supplying water and power.The text of this publication was prepared prior toadopt ion of the new name; all references to the Bureau ofReclamation or any derivative thereof are to be con-s~dered synonymous with the Water and PowerResoLJrces Ser~ice.

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C O N T E N T SPage

P u r p o s e ............................................................. 1i n t r o d u c t i o n .........................................................I n v e s t ig a t i o n s ........................................................... 2E x p e r i m e n t a l a p p a r a tu s . . .. . .. .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . 7E x p e r i m e n t a l p r o c e d u r e .. .. . .. .. . .. . .. .. . .. . .. .. . .. .. . .. . .. .. . .. . .. .. . 11E x p e r i m e n t a l re su lt s . .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. .. . .. . .. .. . . 14C on c l us io ns . . . . . . . . . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 18B i b l i o g r a p h y ......................................................... 21

T a b l eT A B L E S

1 F i l t er I ( 0 .4 2 5 t o 0 . 5 00 n u n ( 0 .0 1 7 t o 0 . 0 2 0 i n ) s a n d ) . . . . . . . . . . . . . . . . . . . 1 52 F i l t er 2 { 1.2 0 t o 1 .7 0 m m { 0.0 47 t o 0 . 0 67 i n ) s a n d ) . . . . . . . . . . . . . . . . . . . . . 1 6

F i g u r eF I G U R E S

1 E x p e ri m e n ta l a p p ar a tu s . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 82 F i l te r s op e r a t in g in th e f i l t ra t io n m o d e . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 103 F i l te r b e d e x p a n s i o n v e r s us b a c k w a s h f lo w r a t e f o r

fi lt e r 1 ........................................................ 124 F i l t e r b e d e x p a n s i o n v e r s us b a c k w a s h f lo w r a t e f o r

f i l te r 2 . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . ~ . . . . . . . . . . . . . . . . . 135 H e a d l o ss v e r s u s t i m e f o r f i l te r 1 ,

J u n e 21 , 22 , 19 78 .............................................. 176 H e a d l o ss v e r s u s t i m e f o r f i l te r 1 ,

A u g u s t 8, 9, 10 , 19 78 ........................................... 19

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P U R P O S E

L a b o r a t o r y s t u d i e s w e r e m a d e t o i n v e s t ig a t e t h e r e q u i r e d p a r a m e t e r s o f a h i g h r a t e g r a v -i t y s a n d f i l t e r f o r r e m o v i n g f i s h e g g s a n d f i s h l a r v a e f r o m a f l o w o f w a t e r a n d t od e m o n s t r a t e t h a t a s a n d f i l te r c a n b e u s e d a t th e L o n e t r e e R e s e r v o i r o u t l e t w o r k s t o p r e -v e n t t h e p a s s a g e o f f i s h , f i s h e g g s , a n d f i s h l a r v a e i n t o t h e S h e y e n n e R i v e r .

I N T R O D U C T I O N

T h e G a r r i s o n D i v e r s i o n U n i t o f t h e P i c k - S l o a n M i s s o u r i B a s i n P r o g r a m c o n s i s t s o f a ne x t e n s iv e , m u l t i b a s i n i r r i g a t io n s y s t e m . A b o u t 1 0 0 0 0 0 h e c t a r e s 2 5 0 0 0 0 a cr e s) i n e a s t-c e n t r a l N o r t h D a k o t a w i ll b e s e rv e d b y th e s y s t e m . T h e w a t e r w i ll b e w i t h d r a w n f r o mt h e M i s s o u r i R i v e r a n d d e l iv e r e d to t h e f a r m l a n d t h r o u g h a s e ri es of p u m p i n g p l a n t s ,r e s e r v o ir s , a n d c a n a l s . T h e l a n d t o b e s e r v e d li e s i n t h e S o u r i s , S h e y e n n e , J a m e s , a n dW i l d R i c e R i v e r d r a i n a g e s . T h e J a m e s R i v e r i s a t r ib u t a r y o f t h e M i s s o u r i; t h e S h e y e n n ea n d W i l d R i c e R i v e r s a r e t r i b u t a r i e s o f t h e R e d R i v e r o f t h e N o r t h . T h e S o u r i s R i v e ra n d t h e R e d R i v e r o f t h e N o r t h b o t h f lo w in t o C a n a d a .

T h e L o n e t r e e R e s e r v o i r w i l l b e a n i n t e g r a l p a r t o f t h e s y s t e m . T h i s r e s e r v o i r w i l l r e c e iv ew a t e r f r o m t h e M i s s o u r i R i v e r v i a t h e M c C l u s k y C a n a l . A n o u t l e t w o r k s w i l l b e r e q u i re da t t h e r e s e r v o i r f o r m u n i c i p a l a n d i n d u s t r i a l r . e l e a s e s a n d s t r e a m f l o w a u g m e n t a t i o n i n t ot h e S h e y e n n e R i v e r . T h e f lo w t h r o u g h t h e o u t l e t w o r k s w i ll b e 0 . 5 7 m 3 / s 20 f t 3 / s ) w i t hf u t u r e e n l a r g e d d i s c h a r g e s o f u p t o 2 . 3 m a / s 80 f t 3 / s) b e i n g c o n s i d e r e d .

T h e M i s s o u r i R i v e r c o n t a i n s s p e c i es o f f i s h t h a t a r e c o n s i d e r e d u n d e s i r a b l e . I t a p p e a r s ,h o w e v e r , t h a t t h e S o u r i s a n d R e d R i v e r of t h e N o r t h m a y n o t c o n t a i n a l l o f t h e s e s p ec i e s.T h e p r e s e n c e o f th e u n d e s i r a b l e f i s h m i g h t r e d u c e t h e v a l u e o f a f f e c t e d w a t e r s f o r w a t e r -f o w l a n d a s a c o m m e r c i a l a n d s p o r t s f i s h e r y [ 1 ]. l

1 N u m b e r s i n b r a c k e t s r e f e r t o l i te r a t u r e c i t e d in t h e b i b l i o g r a p h y .

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F o r t h e s e r e a s o n s , i t h a s b e e n a s s u m e d t h a t n o f i s h , f i s h e g g s , o r f i s h l a r v a e m i g r a t i o nt h r o u g h t h e L o n e t r e e R e s e r v o i r o u t l e t w o r k s i n t o t h e S h e y e n n e R i v e r w i ll b e t o l e r a te d .

I N V E S T I G A T I O N S

M e t h o d s f o r r e s t r i c t i n g t h e d o w n s t r e a m d i s t r i b u t i o n o f f i s h i n a w a t e r c o u r s e w e r e i n -v e s t i g a t e d f o r t h i s s t u d y . T h e s e m e t h o d s w e r e g r o u p e d i n t o t w o g e n e r a l c a t e g o r i e s :

1 . P h y s i c a l r e m o v a l p r o c e s s e s

2 . P r o c e s s e s p r o v i n g l e t h a l t o t h e f i s h a n d e g g s

A p r o c e s s of p h y s i c a l l y r e m o v i n g t h e f i s h a n d e g g s f r o m a s t r e a m w a s c h o s e n o v e r a n yp r o c e s s t h a t w o u l d b e l e t h a l t o t h e f i s h a n d e g g s b e c a u s e o f t h e c o m p a r a t i v e l y h i g h e rr e l i a b i l i t y , l o w e r o p e r a t i n g c o s t s , a n d s i m p l e r o p e r a t i o n .

T h e s p e c ie s o f f i s h w h i c h w i l l b e o f c o n c e r n a t t h e L o n e t r e e R e s e r v o i r o u t l e t w o r k s h a v ee g g s w h i c h a p p e a r t o r a n g e f r o m a p p r o x i m a t e l y 1 t o 2 m m 0 .0 4 0 to 00 . 0 8 0 i n) i nd i a m e t e r [ 2 ] . T h e l a r v a e o f s o m e o f t h e s e s p e c i e s m a y h a v e a m i n i m u m c r o s s - s e c t i o n f i ld i a m e t e r o f 0 . 3 5 m m t 0 .0 1 4 i n ) [3 ]. N o n e o f t h e p h y s i c a l r e m o v a l p r o c e s s e s in v e s t i g a t e da l lo w e d s e l ec t iv e r e m o v a l o f f i s h a n d e g g s of t h i s si ze f r o m o t h e r o r g a n i c a n d i n o r g a n i cm a t t e r i n a s t r e a m f l o w . T h e r e f o r e , t h e f i s h a n d e g g r e m o v a l h a s b e e n v i e w e d a s as u s p e n d e d s o l id s r e m o v a l p r o c e s s in t h i s s t u d y . I n a d d i t i o n , t h e m o t i l i ty o f t h e f i s h la r v a ei s a v e r y i m p o r t a n t c o n s i d e r a t i o n .

T h e p h y s i c a l r e m o v a l p r o c e s s c h o s e n m u s t m e e t t h e s t r i n g e n t r e q u i r e m e n t o f r e m o v i n g1 0 0 p e r c e n t o f th e s u s p e n d e d s o li d m a t e r i a l o f 0 . 3 5 m m 0 . 0 14 i n ) i n d i a m e t e r . I t i s f e l tt h a t t h i s c a n b e o b t a i n e d o n l y w i t h v e r y s t ri c t o p e r a t i o n a l c o n t r o l , n o m a t t e r w h a t t r e a t -m e n t i s u s e d . T h i s m a t t e r i s f u r t h e r d i s c u s s e d i n th e c o n c l u s i o n s s e c t io n .

C o n v e n t i o n a l m e t h o d s u s e d t o r e m o v e s u s p e n d e d s o li d s f r o m w a t e r i n c lu d e m e c h a n i c a ls c r ee n s ; c h e m i c a l a d d i t i o n , c o a g u l a t i o n , a n d s e t t li n g ; c a r t r i d g e f i lt e rs ; u l t r a f i l t r a t i o n ;

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a n d s a n d o r m u l t i m e d i a f i l tr a t i o n . A l l o f th e s e m e t h o d s w e r e c a r e f u l l y c o n s i d e r e d i n -d e p e n d e n t l y a n d i n c o m b i n a t i o n w i t h e a c h o t h e r w i t h r e sp e c t t o c a p i t a l c os ts , o p e r a -t i o n a l co s ts , s p a c e r e q u i r e m e n t s , f lo w r e q u i r e m e n t s , a n d t h e l O 0 - p e r c e n t f is h a n d e g gr e m o v a l r e q u i r e m e n t .

A l so c o n s id e r e d w a s t h e r e c o m m e n d a t i o n b y t h e I n t e r n a t i o n a l G a r r i s o n D i v e r s io n S t u d yB o a r d w h o s e p u r p o s e w a s t o in v e s t i g a te a n d a d v i s e o n e n v i r o n m e n t a l m a t t e r s o f t h eG a r r i s o n D i v e r s i o n U n i t ) t o th e I n t e r n a t i o n a l J o i n t C o m m i s s i o n t h a t a s u i ta b l e s a n df i lt e r b e u s e d a t t h e L o n e t r e e R e s e r v o i r o u t l e t w o r k s t o e l i m i n a t e t h e t r a n s f e r o f f is h , f is he g g s , a n d f i s h l a r v a e t o t h e S h e y e n n e R i v e r [ 12 ].

B a s e d o n t h e s e c o n s i d e r a t i o n s , m e c h a n i c a l s c r e e n in g p l u s h i g h r a t e g r a v i t y s a n d f i lt r a -t i o n w a s c o n s i d e r e d t h e b e s t p o s s ib l e tr e a t m e n t . T h e m e c h a n i c a l s c re e n i n g w i ll r e m o v et h e l a r g e s u s p e n d e d s o l i d m a t e r i a l i n c l u d i n g s m a l l f i s h , a lg a e , l e a v e s , e tc . ), a n d t h e h i g hr a t e s a n d f i lt e rs w i ll r e m o v e t h e s m a l l s u s p e n d e d s o li d s i n c l u d i n g t h e f i s h e gg s a n dl a r v a e .

T h e l i t e ra t u r e h a s b e e n i n v e s t i g a t e d t o d e t e r m i n e w h e t h e r s a n d f i l te r s h a v e p r e v i o u s l yb e e n u s e d t o r e m o v e s m a l l li v i n g o r g a n i s m s w h i c h c o u l d b e c o m p a r e d t o t h e f is h e gg sa n d l a r v a e . T h e l i t e r a tu r e s e a r c h r e s u l t e d i n v e r y f ew p u b l i s h e d s t u d i e s o n t h e s u b j ec t .O n e s t u d y h a s i n v e s t i g a te d t h e e f f e c t iv e n e s s o f r a p i d s a n d f i l tr a t i o n f o r r e m o v a l o fn e m a t o d e s [4 ]. N e m a t o d e s a r e v e r y t h i n , t h r e a d - l i k e , w o r m - l i k e o r g a n i s m s w i t h a l e n g t ho f 0 . 1 6 t o 2 . 0 m m 0 . 0 0 6 t o 0 . 0 7 9 i n ) w h i c h a r e s o m e t i m e s f o u n d i n p u b l i c w a t e r s u p -p li es . T h e s t u d y c o n c l u d e d t h a t d e a d n e m a t o d e s u s u a l ly c h l o r i n a t e d ) w e r e t o t a l lyr e m o v e d b y g r a v i t y f il t r a ti o n t h r o u g h a s a n d b e d w i t h a n e f fe c t iv e s a n d s iz e o f 0 . 5 m m0 . 02 0 i n ) a n d a d e p t h o f 6 0 0 m m 2 4 i n ), b u t o n l y a p p r o x i m a t e l y 25 p e r c e n t o f t h e li ve ,m o t i l e n e m a t o d e s w e r e r e m o v e d . M o t i l e n e m a t o d e r e m o v a l w a s i n d e p e n d e n t o f t h e

f i l t r a t i o n r a t e .

I n t h e p a c i f i c N o r t h w e s t , s a l m o n l a r v a e h a v e b e e n r e p o r t e d i n w a t e r w e l l s w h i c h a r el o c a t e d n e a r r i v e r b e d s . T h e s e l a r v a e h a v e m i g r a t e d f r o m t h e r i v e r t h r o u g h t h e g r a v e l

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a q u i f e r a n d i n t o t h e w e ll s. T h u s , t h e m o t i l it y o f f i sh l a r v a e m u s t b e c a r e f u l ly c o n s i d e r e dw h e n t r y i n g t o p r e v e n t t h e i r m i g r a t i o n . 2

B e c a u s e o f t h e l a c k o f p r e v i o u s s t u d i e s u s i n g h i g h r a t e f i l te r s f o r t h e r e m o v a l o f f i s h e g g sa n d l a r v a e , a h i g h r a t e g r a v i t y s a n d f i lt e r m o d e l w a s c o n s t r u c t e d a n d t e s te d . T h e p u r p o s eo f t h e m o d e l i n t h i s s tu d y w a s t o d e t e r m i n e w h e t h e r a s a n d f i lt e r c o u l d b e u s e d t o r e m o v ef i s h e g g s a n d l a r v a e f r o m a f l o w o f w a t e r .

A d i s c u s s i o n o f t h e d e s i g n o f c o n v e n t i o n a l h i g h r a t e f i l te r s is a p p l i c a b l e h e r e . T h i s i n f o r -m a t i o n w a s u s e d a s a b a s i s f o r d e s i g n i n g th e s t u d y m o d e l .

T h e m a j o r f a c t o r s a f f e c ti n g t h e d e s i g n o f h i g h r a t e f i l te r s i n c l u d e 1 ) t y p e o f f i lt e r m e d i a ,2 ) t y p e o f f i l t e r m e d i a b a c k w a s h , 3 ) d e p t h a n d s i ze o f f i l t e r m e d i a , a n d 4 ) f l o w r a t e

t h r o u g h t h e f i l te r .

1 ) T y p e o f f i lt e r m e d i a . - S a n d i s t h e m o s t e c o n o m i c a l f i lt e r m e d i a , a l t h o u g h a fi n es a n d w i l l n o t p r o v i d e l o n g f i lt e r r u n s b e t w e e n b a c k w a s h i n g s . T h i s i s b e c a u s e t h e h e a dl os s t h r o u g h a f i n e s a n d i n c r e a s e s in a s h o r t t i m e d u e t o t h e d e p o s i t i o n o f s u s p e n d e dm a t t e r w i t h i n t h e t o p 5 0 m m 2 i n) o f t h e m e d i a . D u a l m e d i a c o a l a n d s a n d ) a n dm i x e d m e d i a u s u a l l y c o a l, s a n d a n d g a r n e t s a n d ) f i lt e r s a l lo w d e e p e r p e n e t r a t i o n o fs u s p e n d e d m a t t e r i n t o t h e f i lt e r b e d a n d t h u s t h e b u i l d u p o f h e a d l os s i s s l o w e r t h a n as a n d f i l te r . T h i s r e s u lt s i n fe w e r b a c k w a s h i n g s o f th e f i l t e r a n d a s a v i n g s o f p o w e r a n dwater [5] .

2 ) T y p e o f f i lt e r m e d i a b a c k w a s h . G r a v i t y f i lt e rs a r e u s u a l l y c l e a n e d b yb a c k w a s h i n g t h e m e d i a w h i c h r e m o v e s t h e s u s p e n d e d s o l i d s t h a t a r e t r a p p e d i n t h em e d i a . A b a c k w a s h w a t e r f l o w r a t e c a p a b l e o f e x p a n d i n g t h e f i l t er b e d 2 0 to 5 0 p e r c e n tis u s u a l ly a d e q u a t e t o o b t a i n c o m p l e t e c l e a n i n g o f t h e m e d i a [ 6] . A t th e s a m e t i m e , t h e

2 D r . M i l o B e ll , U n i v e r s i t y of W a s h i n g t o n , S e a t tl e , p e r s o n a l c o m m u n i c a t i o n

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b a c k w a s h r a t e s h o u l d b e h i g h e r t h a n t h e t e r m i n a l s e t tl i n g v e l o ci ty of th e s u s p e n d e dm a t t e r l o d g e d i n th e f i lt e r m e d i a . T h e r a t e a t w h i c h t h e b a c k w a s h m u s t b e a p p l i e d t ot h e fi l te r m e d i a t o f l u id i z e a n d e x p a n d t h e f i lt e r b e d d e p e n d s o n t h e t e m p e r a t u r e o f t h ew a t e r , t h e d e n s i t y o f t h e f i l te r m e d i a , a n d t h e s i ze of e a c h p a r t i c le c o m p o s i n g t h e f i l t e rm e d i a . T h e s iz e o f e a c h p a r t i c le i n t h e m e d i a i s t h e m o s t i n f l u e n c i n g f a c t o r d e t e r m i n -i n g t h e b a c k w a s h r a t e. I t h a s b e e n s h o w n t h a t t h e r e q u i r e d b a c k w a s h r a t e t o fl u id i z e af i lt e r b e d i n c r e a s e s b y a p p r o x i m a t e l y t h e s q u a r e o f th e p a r t i c l e s i ze u s e d [7 , 8 ] .T h e r e f o r e , l i m i t a t i o n s o n b a c k w a s h r a t e s w i l l a f f e c t t h e s i z e o f f i l te r m e d i a p a r t i c le s .S a n d m e d i a o f a p a r t i c l e s i z e 1 . 3 m m i 0 . 0 5 1 i n ) o r l a r g e r c a n n o t b e e f f e c t i v e l yb a c k w a s h e d u s i n g m e d i a f l u i d i z a t i o n t e c h n i q u e s [ 9 ] .

3 ) D e p t h a n d s iz e o f f i lt e r m e d i a . - C u r r e n t l y , t h e r e a r e t w o p o s s ib l e b a s i c w a y s t od e t e r m i n e t h e d e p t h a n d s iz e o f f i l te r m e d i a , a n d t h e y a re a ) a p il o t p l a n t s t u d y , a n db ) a n e d u c a t e d g u e s s fr o m a v a i l a b l e d a t e [ 5] .

C o n v e n t i o n a l s a n d f i l te r s f o r tr e a t i n g w a t e r f o r d o m e s t i c u s e r a n g e i n d e p t h f r o m 6 0 0t o 900 m m 24 t o 36 in ) .

T h e s iz e o f f i lt e r m e d i a r e q u i r e d c a n b e o b t a i n e d b y c o n s i d e r i n g t h a t g e n e r a l l y t h el a r ge s t po r e open i ng i n a f i l te r me d i a i s on l y abo u t 15 pe r cen t o f t he med i a s i z e . I n p r ac -t ic e , a f i lt e r s hou l d be ab l e t o r emove by s t r a i n i n g any p a r t i c l e who s e d i am e t e r i s g r ea t e rt ha n app r ox i m a t e l y 5 pe r cen t o f t he m ed i a s i ze [9 ]. Of cou r s e, t he l i m i t a t i ons o f f i l te rm e d i a s iz e b y t h e b a c k w a s h , a s p r e v io u s l y m e n t i o n e d , m u s t b e r e a li z e d . F o r s i z in g t h ef i l t e r med i a t o r emove t he f i s h eggs and l a r vae a t t he Lone t r ee Res e r vo i r ou t l e t wor ksus i ng t he above i n f o r ma t i on , i t i s kn ow n t h a t t he s ma l l e s t pa r t i c l e t o be rem oved l a r-vae ) is 0 . 35 mm 0 . 014 i nk Th us , 0 . 35 mm d i v i ded by 5 pe r cen t o r a fi l t e r med i a s i ze o f7 . 0 mm ~ 0.28 i n t cou l d be u s ed . No t e t ha t t h i s is f a r g r ea t e r t h an t he l a r ge s t r e a l i s t ic s i zeme d i a o f 1. 3 m m 0 .051 i n l t ha t cou l d be u s ed w i t h a f l u i d i zed bac kw as h .

C o n v e n t i o n a l s iz e s o f s a n d f i l t e r m e d i a f o r t r e a t i n g w a t e r f o r d o m e s t i c p u r p o s e s r a n g ef r om 0 . 35 t o 1 . 30 m m 0 . 014 t o 0 . 051 i n ).

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4) F l o w r a t e t h r o u g h t h e f il t e r. - T h e f l o w r a t e a n d t e r m i n a l h e a d l o ss f o r a f i l te r a r eu s u a l l y s e l e c t e d b y m a k i n g e c o n o m i c t r a d e o f f s b e t w e e n f i l t e r s i z e , o p e r a t i n g h e a d r e -q u i r e m e n t s , a n d r u n l e n g t h , a l l w i t h i n t h e l i m i t s d i c t a t e d b y e f f l u e n t q u a l i t y re q u i r e -m e n t s . A d e q u a t e i n f o r m a t i o n f o r m a k i n g e c o n o m i c t r a d e o f f s c a n b e o b t a i n e d o n l yf r om p i l o t s t ud i e s o f t he s pec i f i c me d i a app l i c a t i o n [ 10] .

F l o w r a t e s t h r o u g h g r a n u l a r m e d i a f i l t e rs h a v e r a n g e d f r o m 1 . 36 1 0 -3 t o 2 0 .4 x1 0 -a m / s {2 t o 3 0 g a l / m i n ) / f t : ) d e p e n d i n g o n t h e d e g r e e o f fi l t r a t i o n r e q u i r e d .G e n e r a l l y , t h e h i g h e r t h e f l o w r a t e t h r o u g h t h e f i lt e r , th e g r e a t e r t h e h e a d l o s s b u i l d u pp e r u n i t v o l u m e o f w a t e r f i l te r e d .

B a s e d o n t h i s d i s c u s s i o n , t h e f o l l o w i n g p a r a m e t e r s w e r e u s e d i n t h e f i l t e r m o d e l s t u d ya n d w e r e k e p t c o n s t a n t t h r o u g h o u t t h e s t u d y .

1 . S i l i c a s and was u s ed a s t he f i l t e r me d i a .

2 . A w a t e r b a c k w a s h w i t h a r a t e s u f fi c i e n t t o e x p a n d t h e s a n d b e d w a s u s e d . T h e a c-t u a l b e d e x p a n s i o n u s e d f o r e a c h e f f e c t iv e s iz e s a n d b e d i s d i s c u s s e d i n t h e e x p e r i -m e n t a l p r o c e d u r e .3 . Tw o s i ze s o f s an d we r e u s ed . S i nce t wo f i l t e r c e l ls we r e ava i l ab l e , t he t wo s ize s o fs a n d w e r e t e s t e d s i m u l t a n e o u s l y . T h e s m a l l e r s a n d s i z e w a s u s e d i n f i l t e r 1 . T h e s a n dhad a un i f o r mi t y coe f f i c i en t o f 1 . 20 t o 1 . 60 and an e f f ec t i ve s i z e o f 0 . 425 t o 0 . 500 mmt 0 . 017 t o 0 . 020 i n ) . I n f i l t e r 2 , a l a r ge r s and s i z e was u s ed . The un i f o r mi t y coe f f i c i en to f t h e s a n d w a s n o t d e t e r m i n e d . T h e e f f e c t iv e si ze w a s e s t i m a t e d a t 1 . 20 t o 1 .7 0 m m0 .0 5 t o 0 . 0 7 i n ). T h e d e p t h o f e a c h s a n d b e d u s e d w a s 3 8 0 m m I 15 in ) .

4 . T h e fl o w r a t e t h r o u g h e a c h f i l te r w a s 6 . 7 9 1 0 -3 m / s 1 0 g a l / m i n ) / f t 2 ) .

T h e f i l t e r m o d e l w a s c o n s t r u c t e d a n d t e s t e d i n t h e h y d r a u l i c l a b o r a t o r y a t t h e E n g i n e e r -i n g a n d R e s e a r c h C e n t e r . T h e l a b o r a t o r y h a s a l ar g e w a t e r s u m p i n w h i c h w a t e r i s s t or e d

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f o r us e in th e h y d r a u l i c m o d e l s . T h i s w a t e r w a s u s e d f o r b o t h t h e f i lt r a t io n a n d b a c k w a s hf i lt e r m o d e s i n t h i s s t u d y . T h e w a t e r h a d s o m e t u r b i d i t y , 8 t o 1 0 J T U , a n d q u i t e a b i t o fi r o n i n s o l u t i o n , p r e s u m a b l y f r o m c o r r o s i o n o f e q u i p m e n t i n t h e l a b o r a t o r y .

T h e f i l t r a t i o n t e s t s w e r e c o n d u c t e d i n t h e s u m m e r o f 1 97 8 d u r i n g t h e s p a w n i n g s e a s o n o ft w o s p e c i e s o f f i s h f o u n d i n t h e w a t e r s n e a r t h e L o n e t r e e d a m s i t e . I n t h i s w a y , l i v e f i s he g g s a n d l a r v a e c o u ld b e u s e d in th e e x p e r i m e n t . T h e c o m m o n c a r p Cyp rinus carpio)a n d t h e r a i n b o w s m e l t Osmerus mordax) w e r e c o n s i d e r e d t o h a v e e g g s a n d l a r v a e o f t h em i n i m u m s iz e t o b e e n c o u n t e r e d a t t h e L o n e t r e e D a m o u t l e t w o r k s . T h u s , t h e se tw os p ec ie s w e re u s e d i n t h i s s t u d y . T h e E n v i r o n m e n t a l S c i en c e s S e c ti o n o b t a i n e d s p a w n i n gs p e c i m e n s o f t h e s e fi s h a n d t h e s p e c i m e n s w e r e s u s t a i n e d i n t h e l a b o r a t o r y u n t i l l iv e e g g sw e r e o b t a i n e d . T h e l i v e e g g s w e r e s u s t a i n e d u n t i l t h e y h a t c h e d i n t o l a r v a e .

E g g s p r e s e r v e d i n f o r m a l d e h y d e w e r e u s e d i n t h e e x p e r i m e n t a f t e r t h e s u p p l y o f l iv e e g g sw a s d e p l e t e d .

E X P E R I M E N T A L A P P A R A T U S

Tw o r ec t angu l ~ i r f i l t e r c e l l s we r e c ons t r uc t ed f ig . 1 ) s o t ha t t wo s i ze s o f f i l t e r s an d cou l db e t e s t e d s i m u l t a n e o u s l y . T h e c e l ls w e r e c o n s t r u c t e d u s i n g 1 2 - m m 1 / 2 - i n ) c l e a r p l ex -i g l a s s s o t h a t t h e o p e r a t i o n o f e a c h f i l t e r c o u l d b e o b s e r v e d . E a c h f i l te r h a d a f i lt e r a r e a o f0 . 1 9 m s 2 ft~ ). T h e f i l te r m e d i a d e p t h i n e a c h f i l te r w a s 3 8 0 m m 1 5 i n ) a n d t h e m e d i aw a s s u p p o r t e d b y g r a v e l la y e r s. T h e g r a v e l l a y e r w a s c o m p o s e d o f g r a d e d g r a v e l 1 5 0 m m6 i n ) i n d e p t h . T h e g r a v e l l a y e r a n d t h e f i l t e r m e d i a w e r e s u p p o r t e d b y a p o r o u s p l a t e -

t y p e u n d e r d r a i n .

F o r t h e f i l tr a t io n m o d e a f il t er i n f l u e n t p u m p f o r e a c h f il te r w a s u s e d t o p u m p w a t e r f r o mt h e l a b o r a t o r y s u m p t o t h e fi lt er s. T h e w a t e r w o u l d p a s s t h r o u g h t h e i n f l u e n t p u m p i n tot h e i n f l u e n t a n d d r a i n a g e c o m p a r t m e n t a n d i n t o a d i s t r ib u t i o n a n d b a c k w a s h w a t e r co l-l e c t io n t r o u g h . T h e w a t e r w o u l d t h e n o v e r f l o w t h e tr o u g h a n d b e a p p l i e d t o t h e s a n d . I t

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w o u l d t h e n f i l te r t h r o u g h t h e s a n d , g r a v e l , a n d p o r o u s p l a t e i n to t h e u n d e r d r a i n a n d e x i tt h e f i l t e r t h r o u g h t h e f i l t e r e f f l u e n t p ip e . A f t e r l e a v i n g t h e f i l te r e f f lu e n t p i p e , t h e w a t e rw a s f i l t e r e d t h r o u g h a 1 0 2 - / a m m e s h p l a n k t o n n e t a n d t h e n r e t u r n e d i n t o t h e s u m p . T h ep l a n k t o n n e t w a s u s e d t o r e t a in a n y e g g s o r l a rv a e w h i c h m a y h a v e b y p a s s e d t h e f il te r . I nt h i s w a y t h e f i l te r e f fi c i e n c y w a s d e t e r m i n e d . C o n t r o l o f t h e f i lt e r r a t e t o e a c h f i lt e r w a so b t a i n e d b y a v a l v e l o c a t e d o n t h e d i s c h a r g e o f e a c h f i l t e r i n f l u e n t p u m p .

F o r t h e f il te r b a c k w a s h m o d e a c o m m o n b a c k w a s h p u m p w a s u s e d f or e ac h f il te r .B a c k w a s h i n g o f t h e f i l t e r s w a s d o n e m a n u a l l y b y f i r s t s w i t c h i n g o f f t h e f i l t e r i n f l u e n tp u m p , t h e n c l o s i n g t h e f il t e r e f f l u e n t v a l v e , a n d o p e n i n g t h e b a c k w a s h d r a i n v a l v e a n db a c k w a s h p u m p v a lv e . T h e b a c k w a s h p u m p w o u l d th e n b e tu r n e d o n a n d t h e b a c k w a s hw a t e r w o u l d b e p u m p e d f r o m t h e s u m p i n to th e f il te r u n d e r d r a i n , t h r o u g h t h e g ra v e l a n ds a n d , a n d u p t o t h e c o ll e ct io n t r o u g h . T h e w a t e r w o u l d t h e n d r a i n f r o m t h e t ro u g ht h r o u g h t h e i n f l u e n t a n d d r a i n a g e c o m p a r t m e n t , i n t o t h e b a c k w a s h d r a i n p i p e , a n d i n t ot h e s u m p . T h e r a t e o f b a c k w a s h w a t e r f l o w w a s c o n t r o l l e d t o e a c h f i l t e r b y v a l v e s o n t h ed i s c h a r g e o f t h e b a c k w a s h p u m p .

F i l t r a t io n a n d b a c k w a s h f l o w r a t e s w e r e m e a s u r e d b y s t o p w a t c h t i m i n g t h e r e q u i re dt i me f o r t he f l ow t o f i l l a c e r t a i n vo l ume .

H e a d l o ss w a s m e a s u r e d b y u s i n g a fl e x ib l e t u b e w h i c h w a s c o n n e c t e d i n t o th e f i lt e ru n d e r d r a i n a n d a t t a c h e d t o t h e s i d e o f t h e f i l t e r c e l l . T h e h e i g h t d i f f e r e n c e b e t w e e n t h ew a t e r s u r f a c e i n t h e f il t e r a n d t h e w a t e r s u r f a c e i n th e t u b e w a s r e c o r d e d a s t h e h e a d l o sst h r o u g h t h e f i l t e r .

P r i o r t o t h e s t a r t o f t h e f i l tr a t i o n e x p e r i m e n t s , e a c h f i l t e r w a s b a c k w a s h e d a n d a p p r o x -i m a t e l y 2 5 m m 1 in ) of t h e t o p of b o t h s a n d b e d s w a s r e m o v e d . T h i s w a s d o n e t o r e m o v em o s t o f t h e f i n e s f r o m t h e b e d s .

F i g u r e 2 is a ~ p h o to g r a p h o f t h e f il te r s a n d t h e r e l a te d e q u i p m e n t . T h e p h o t o g r a p h w a st a k e n w h i l e t h e f i l t e r s w e r e i n t h e f i l t r a t i o n m o d e .

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F igu re 2 . F i l t e r s op e ra t ing in the f i l tr a t ion m ode .

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E X P E R I M E N T A L P R O C E D U R E

T h e f i l te r s we r e ope r a t e d a t a c on s t a n t f i l t r a t i on r a t e o f 6 . 79 10 -3 m / s i l 0 ga l / m i n ) / f t ~ lo r 1 . 26 10 -3 m3 / s 20 ga l / m i n ) / f t 2) t o e a c h f i l t e r . T h e t i me a l l o t t e d f o r t h i s s t udy d i dn o t a l l o w i n v e s t i g a t i o n a t a d d i t i o n a l f i l t r a t i o n r a t e s .

T h e f i lt e rs w e r e n o r m a l l y o p e r a t e d f o r 24 h o u r s p e r d a y , 5 d a y s p e r w e e k . T h u s , t h ef i l te r s w e r e o b s e r v e d u n d e r l o n g - t e r m c o n t i n u o u s o p e r a t i o n .

T h e i n i t i a l h e a d l o s s t h r o u g h e a c h f i l te r w a s r e c o r d e d . T h e h e a d l o s s t h r o u g h t h e c l e a ns a n d i n f il t e r 1 0 . 4 25 t o 0 . 5 0 0 m m 0 . 01 7 t o 0 . 0 1 0 in ) s a n d s iz e} w a s a p p r o x i m a t e l y6 6 0 m m 2 6 i n ) w h i l e t h e i n i t ia l h e a d l o ss t h r o u g h f i l t e r 2 1 . 20 to 1 .7 0 m m 0 . 04 7 to0 . 0 6 7 in ) s a n d s iz e} w a s a p p r o x i m a t e l y 2 8 0 m m l l i n ) . T h r o u g h o u t t h e t e s t i n g , n o p r o -g r e s s iv e b u i l d u p o f t h e h e a d l o ss e s t h r o u g h t h e f il t e r s w a s n o t e d a f t e r b a c k w a s h i n g . T h i si m p l i e d t h a t t h e b a c k w a s h i n g w a s d o i n g a n a d e q u a t e j o b o f c l e a n i n g t h e m e d i a . T h e t er -m i n a l h e a d l o s s f o r e a c h f i l te r w a s s e t a t a p p r o x i m a t e l y 1 1 5 0 m m 4 5 i n} . W h e n t h e h e a dl o s s o f e i t h e r f i l t e r r e a c h e d t h i s p o i n t t h e f i l t e r w a s b a c k w a s h e d . T h i s a l l o w e d a t o t a lh e a d l o ss b u i l d u p o f 4 8 5 m m 1 9 i n ) i n f i l te r 1 a n d 8 6 5 m m 3 4 i n ) i n f i l te r 2 .

I n d e t e r m i n i n g t h e r e q u i r e d b a c k w a s h r a t e s t o b e u s e d i n e a c h f i l t e r t w o f a c t o r s w e r ec o n s i d e r e d . F i r s t , t h e s e t t l i n g v e l o c it i es of t h e f i s h e g g s w e r e d e t e r m i n e d . A n a v e r a g e s e t-t l in g v e lo c i ty fo r a n i n d i v i d u a l e g g w a s f o u n d t o b e 7 3 2 m m / m i n 1 2.40 f t / m i n ) a t at e m p e r a t u r e o f 2 2 C 7 2 F ) . T h i s w o u l d re q u i r e a m i n i m u m b a c k w a s h r a t e of 1 2 .2 10 -3 t o 12 . 9 10 -3 m / s 18 to 19 g a l / m i n ) / h ~) t o c a r r y t he e gg ou t o f t he f i l t e r c e l l.N e x t , t h e e x p a n s i o n h e i g h t o f e a c h s a n d b e d v e r s u s b a c k w a s h f lo w r a te w a s c o n s i d e r e d .F i g u r e s 3 a n d 4 s h o w t h e p e r c e n t a g e o f b e d e x p a n s i o n v e r s u s b a c k w a s h f lo w r a te o b -t a i n e d f o r f i l t e r s 1 a n d 2 , r e s p e c t i v e l y . A s a r e s u l t , t h e b a c k w a s h r a t e u s e d t h r o u g h o u tt h e s t u d y f o r f i l te r 1 w a s 1 3 . 6 x 1 0 -3 m / s 2 0 g a l / m i n ) / f t 2) r e s u l t i n g i n a b e d e x p a n s i o no f 3 0 p e r c e n t a n d t h e r a t e u s e d f o r fi l te r 2 w a s 3 8 . 7 x 1 0 -3 m / s 5 7 g a l / m i n ) / f t ~)r e s u l t i n g i n a b e d e x p a n s i o n o f o n l y 1 0 p e r c e n t .

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Z0ZnX

h i

W._JLL

I 0 0

8 0

6

4 0

2 0

/

fJf dofer Temp= 8 C

I 1 5 2 2 5X 1 0 - 3 m / s )

i i l

3 0

0 I 2 3

B A C K W A S H F LO W R A T E F g o l / m i n ) / f l Z - IL2. _JF i g u r e 3 . F i l t e r b e d e x p a n s i o n v e r s u s b a c k w a s h f l o w r a t e f o r f i l te r 1.

2

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2 0

z~=

. =

jo J

2 0 2 5

Wofer Temp = 2 C

5 0 3 5( x 1 0 - 3 m / s )

4 0 4 5 5 0

I t I I I5 0 4 5 6B A C K W A S H F L O W R A T E I ~ g o l / m i n ) / f t 2- ]I_ ,_1

F i g u r e 4 . F i l t e r b e d e x p a n s i o n v e r s u s b a c k w a s h f l o w r a t e f o r f i lt e r 2 .

3

7 0

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T h e f i s h e g g s a n d l a r v a e w e r e i n t r o d u c e d i n t o t h e f i lt e r s b y a d d i n g a s m a l l s c o o p a p -p r o x i m a t e l y 7 0 e g g s ) e v e r y f e w h o u r s i n t h e d i s t r i b u t i o n a n d b a c k w a s h w a t e r c o l l e c t i o nt r o u g h .

T h e p l a n k t o n n e t t h r o u g h w h i c h t h e f il te r e f f lu e n t p as s e d w a s e x a m i n e d f o r e g g s a n d l ar -v a e e v e r y 1 5 m i n u t e s f o r 2 h o u r s a f t e r b a c k w a s h i n g t h e f i l t e r a n d e v e r y 2 h o u r st h e r e a ft e r . B a c k w a s h i n g w a s p e r fo r m e d d u r i n g w o r k i n g h o u r s .

T h e h e a d l o s s t h r o u g h e a c h f i l te r w a s r e c o r d e d e v e r y 2 h o u r s d u r i n g w o r k i n g h o u r s .

E X P E R I M E N T A L R E S U L T S

T h e o p e r a t i o n o f t h e f il t e rs b e g a n o n J u n e 1 6, 1 9 7 8 . A to t a l o f a p p r o x i m a t e l y 6 8 0 h o u r so f ope r a t i on was l ogged on eac h o f t he f i lt e r s . ,

L i v e e gg s a n d l a r v a e a s w e l l a s e gg s p r e s e rv e d i n f o r m a l d e h y d e w e r e a d d e d t o e a c h f il t e rt h r o u g h o u t t h e e x p e r i m e n t . T h e e g g s a n d l a r v a e w e r e a d d e d i n id e n t i ca l q u a n t i ti e s a n ds i m u l t a n e o u s l y t o e a c h f il t er . E g g s w e r e a l s o a d d e d t o t h a t t h e y a c t u a l l y h a t c h e d i n e a c hf i l t e r c e l l on t op o f t he s and bed .

T a b l e s 1 a n d 2 a r e a s u m m a r y o f t h e e g g s a n d l a r v a e d e t e c t e d i n t h e e f f l u e n t o f e a c h f i l te rt h r o u g h o u t t h e e x p e r i m e n t .

T h e s e r e s u l t s c a n b e e x p l a i n e d a s f o l l o w s . I t l i s s u r m i s e d t h a t t h e l a r v a e w e r e s m a l l a n dm o t i l e e n o u g h t o m a k e t h e i r w a y t h r o u g h t h e v o i d s p a c e o f t h e 1 . 2 0 - t o 1 . 7 0 - m m0 . 04 7 - to 0 . 0 6 7 - in ) s i z e s a n d e v e n w h i l e n o t b a c k w a s h i n g t h e s a n d b e d . T h e l a r v a e w e r e

no t de t ec t ed i n t he e f f l uen t o f f i l t e r 1 s o t ha t t he vo i d s pace o f t he 0 . 425 - t o 0 . 500omm0 . 0 1 7 - t o 0 . 0 2 0 - i n ) s i z e s a n d w a s s m a l l e n o u g h t o p r e v e n t t h e l a r v a e m o v e m e n t t h r o u g h

t h e b e d e v e n w h i l e b a c k w a s h i n g .

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T a b l e 1.-Fi lter I 0.425 to 0.500 mm 0.017 to 0.020 in) sand)

N u m b e r o fD a t e T i m e e g gs T y p e o f C o m m e n t sd e t e c t e d e g g s

7 - 11 -7 8 1 4 : 50 3 P r e s e r v e d E g g s d e t e c t e ds m e l t * b a c k w a s h7 - 12 - 78 7 : 30 1 P r e s e r v e d A f t e r b a c k w a s hs m e l t7 - 27 - 78 1 4 :2 0 2 P r e s e r v e d A f t e r b a c k w a s hs m e l t8 -1 1 - 7 8 8 : 0 0 1 P r e s e r v e d A f t e r b a c k w a s hs m e l t

5 m i n u t e s a f t e r

* R a i n b o w s m e l t e g g s p r e s e r v e d i n f o r m a l d e h y d e .

T h e p r e s e r v e d r a i n b o w s m e l t e g g s t h a t w e r e d e t e c t e d i n th e e f f l u e n t o f f i l te r 1 p r o v e d t oh a v e a h i g h e r s p e c i f ic g r a v i t y a n d , t h e r e f o r e , a g r e a t e r s e t t l in g v e l o c it y t h a n t h e l i v e e g g s .A n a v e r a g e s e t tl i n g v e l oc i ty o f 9 1 4 m m / m i n i 3 .0 0 f t / m i n ) w a s o b t a i n e d f o r th e p r e s e r v e de g g s w h i c h c o n v e r t s t o a b a c k w a s h r a t e o f 15 . 2 x 1 0 -3 m / s 2 2 .4 g a l / m i n ) / f t ~ ) . S i n c e ab a c k w a s h r a t e o f 1 3. 6 x 1 0 -3 m / s 2 0 g a l / m i n ) / f t ~) w a s u s e d f o r f i l te r 1, t h e r a t e w a s n o ts u f f i c i e n t e n o u g h t o w a s h o u t t h e s e p r e s e r v e d e g g s . S o m e o f t h e s e p r e s e r v e d e g g s w e r es m a l l e n o u g h a n d d e n s e e n o u g h t o m a k e t h e i r w a y t h r o u g h t h e s a n d b e d v o i d s d u r i n gb a c k w a s h . T h e p r e s e r v e d r a i n b o w s m e l t e g g s w e r e n o t d e t e c t e d i n th e f i lt e r 2 e f f l u e n ts i m p l y b e c a u s e t h e b a c k w a s h w a s s u f f i c i e n t , 3 8 .7 x 1 0 -3 m / s 57 g a l / m i n ) / f t ~ ) , t o w a s ht h e m o u t .

N o t e t h a t d u r i n g t h e c o u r s e o f t h i s e x p e r i m e n t n o l i v e l a r v a e o r e g g s w e r e d e t e c t e d i ne i t he r f i l t e r e f f l uen t .

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Table 2.-Filt er 2 1.20 to 1.70 m m 0.047 to 0.067 in) sand)

Number ofDate Time larvae Type of Commen tsdetected larvae

6-23-78 17:15 1 Carp Larva detected while eggs hatch -ing in filterLarva was de ad6-24-78 10:00 2 Carp Larvae were dead6-28-78 15:10 1 Carp Larva detect ed 5 minute s afterbackwashLarva was dead6-28-78 15:15 1 Carp Larva was dead

Note t hat only preserved rainbow smelt eggs were detec ted in the filter 1 effluent whileonly carp larvae were detected in the filter 2 effluent.

IThe live carp eggs used in the experiment were clumped or stuck together in groups ofapproxima tely 50 eggs or more. These clumps were observed to stay on top of the sandbeds since the backwash rate was not sufficient to wash the m out. They merely stayed atthe top of the sand beds until they broke up and were washed out or until they hatched.

Head loss data were monitored for each filter thro ughout the experiment . The b uildu p ofhead loss through filter 1 was at a rate which requ ired the bed to be backwa shed approx-imately every 24 hours. Figure 5 shows a typical head loss buildup curve versus time forfilter 1. The head loss was allowed to increase until the maximum, 1150 mm 45 in}, wasobtained at which point backwashing was initiated.

The hea d loss bui ldup in filter 2 was very slow com pared to filter 1. This is a result of thelarger void space in filter 2.

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1 2 0 0

2i I 0 0 0

~oo8 0 0

3 0

7 0 0

2 4 6 0 0

f i l t r r u n

5 I0 1.5T I M E h o u r s ) 2 0 2 5 3 0

Figure 5 . - H ea d loss versus t ime fo r f i lt e r 1 Jun e 21 22 1978 .

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The head losses obtained in both filters can be attributed mostly to the amount ofsolubilized ferrous iron in the laboratory s ump water. It is surmised that the ferrous ironin the water was contacted with oxygen as the water cascaded from the distribution andbackwa sh water collection trough onto the wate r surface above the sand bed see fig. 2).This contact with oxygen oxidized the ferrous iron to solid ferric hydroxide which wasremove d in the filters. In the case of filter 2, the void space in the bed was large enoughto let most of the ferric hydroxide pass. The ferric hydroxide solid was very eviden t at thebeginning of each filter backwash as large amounts of the reddish brown material werereleased from the sand.

Near the end of the expe riment the laboratory sump was drained an d fresh city waterwas used to fill it. Since none of the soluble ferrous iron was pres ent in this water, thehead loss buildup was much slower in the filters. Figure 6 shows the head loss versustime for filter 1 after the water change. Using this water, filter 1 was backw ashe d every50 hours. These results stress that t he required ti me between backwashings for a filter isvery depend ent on the influent water quality. The time can really be dete rmined only bya pilot plant test on the actual water to be filtered.

CONCLUSIONS

1. The motility of fish larvae is the most import ant consider ation when designing agravity sand be d to pre vent the passage of fish eggs and fish larvae. The sand used m ustbe sized and uniformly graded to that the void spaces in the bed will not allow thepassage of motile larvae.

2. A sufficient filter backwa sh rate must be used to wash out large fish eggs and to ex-pand the sand bed enough to allow other suspended solids trapped in the bed to bewashed out. But the void space of the exp ande d bed mus t not be so great as to allow fishlarvae to pass.

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- 3 6 - - ~~ . ~ o o

80

7 O 0

I 1 0 0

I 0 0 0

6 0 0 0 I 0 2 0 : 30T I M E h o u r s )2 4 - -

4 0

F i g u r e 6 . - H e a d L o s s v e r s u s t i m e f o r f il te r 1 A u g u s t 8 9 1 0 1 9 7 8 .

5 0

9

6 0

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3 . I t is k n o w n t h a t t h e r a t e o f h e a d l o s s b u i l d u p t h r o u g h a g r a v i t y s a n d f il t e r i s a d i re c tf u n c t i o n o f w a t e r q u a l i t y a n d f i l t r a t i o n r a t e . B a s e d o n t h e p r o j e c t e d w a t e r q u a l i t y t o b ee x p e c t e d t h r o u g h t h e L o n e t r e e R e s e r v o i r o u t l e t w o r k s , a f i l tr a t i o n r a t e o f 6 .7 9 1 0 -am / s 1 0 g a l / m i n ) / f t 2) i s e x p e c t e d t o g i v e p r o p e r f is h e g g a n d f i s h l a r v a e r e m o v a l . T h et i m e b e t w e e n f i l t e r b a c k w a s h i n g s w o u l d b e e x p e c t e d t o b e b e t w e e n 2 4 a n d 7 2 h o u r s .

4 . A s a nd be d u s i ng a 380 - m m I 15 -i n ) de p t h o f 0 . 425 t o 0 . 500 m m s i li c a s a nd w i l l r e mov et h e e g g s a n d l a r v a e o f t h e c o m m o n c a r p Cyprinus carpio) a n d t h e r a i n b o w s m e l tOsm erus mordax). I t i s e x p e c t ed t h a t t h i s s a n d b e d c o u l d r e m o v e t h e e g g s a n d l a r v a e o f

a l l o f t he f i s h spe c i e s e xpe c t e d i n the f l ow t h r o ug h t h e L o ne t r e e R e s e r vo i r ou t l e t wor ks . Af i l te r ba c kw a s h r a t e s u f f i c i e n t t o e xpa nd t he s a n d be d 30 pe r c e n t i s c ons i de r e d s a t i s f a c t o r y .

T h e v o i d s p a c e in a s a n d b e d o f p a r t i c l e s si z e d i n t h e r a n g e o f 1 . 20 t o 1 . 70 m m 0 . 0 47 t o0 . 067 i n ) i s l a r ge e nough t o a l l ow f i s h l a r va e t o pa s s . T he r e f o r e , t h i s s i z e s a nd i s c on -s i d e r e d u n s a t i s f a c t o r y f o r t h e p u r p o s e s o f t h i s s t u d y .

5 . F i s h e g g s p r e s e r v e d i n f o r m a l d e h y d e w e r e s h o w n to h a v e a g r e a t e r s p e c if i c g r a v i t yt ha n l i ve e ggs .

6 . T h e l i m i t e d te s t s c o n d u c t e d i n d i c a t e t h a t h i g h r a t e g r a v i t y s a n d f i l te r s w i l l b e t o t a ll ye f fe c t iv e fo r r e m o v i n g f i s h e g g s a n d f i s h l a rv a e f r o m t h e L o n e t r e e R e s e r v o i r o u t l e t w o r k sr e l ea s e s if t h e f o l l o w i n g p r o c e d u r e s a r e i m p l e m e n t e d :

a . A f i l t e r r i n s e mod e w ou l d be r e q u i r e d t o r i n s e t he s a n d be d a t 6 . 79 10 -3 m / s ~ 10g a l / m i n ) / f t 2) f o r 1 0 t o 1 5 m i n u t e s a f t e r e a c h b a c k w a s h i n g . T h e r i n s e w a t e r a n d t h e

b a c k w a s h w a t e r w o u l d b e r e c y cl e d t o L o n e t r e e R e s e r v o i r v i a a h o l d i n g t a n k .

b . O n l y e x p e r i e n c e d a n d c e r t if i e d w a t e r t r e a t m e n t p l a n t o p e r a t o r s w o u l d b e a ll o w e dt o o p e r a t e t h e f i l t r a t i o n p l a n t .

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The re w i l l a lways be the r emo te po ss ib i li ty o f an upse t in f i l t e r opera t ion d ue to h um aner ror occur r ing a t a t im e whe n f i sh eggs o r l a rvae a r e p r esen t . T he ques t ions o f how f i sheggs and la rvae would be de tec ted downs t r eam of the f i l t e r s and wha t the pena l t i e s o fs u c h a n u p s e t w o u l d b e m u s t b e f u l l y i n v e s ti g a te d b e f o re i m p l e m e n t i n g th e f u ll -s c a ledes ign of the f i l ter s .

B I B L I O G R A P H Y

[1] John son , P . L . , H yd rau l ic M ode l S tudy of a F i sh Screen S t ruc tur e fo r theM c C l u s k y C a n a l , B u r R e c l a m r e p R E C - E R C - 7 5 - 6 , 1 4 p p . , D e c e m b e r 19 75 .

[2 ] M e m o r a n d u m t o E n v i r o n m e n t a l S p e c i a li s t f r o m C h i ef , A p p l i e d S c ie n c es B r a n c h ,Te am repor t o f l i t e r a tu r e r ev iew of me thod s fo r re s t r i c ting the d i s t r ibu t ion of r ough

f i s h , E & R C e n t e r , B u r R e c l a m , D e n v e r , C o l o ., 1 7 D e c e m b e r 1 97 3.

[3 ] J a c k s o n , T o m , a n d L e e M i l l s , C o m m e n t s a t m e e t i n g , F i s h S c r e e n in g F a c i l i t yT a s k F o r ce , B u r R e c l a m , F e b r u a r y 2 , 1 9 78 .

[4] Pe te r son , R . L . , R . S . Eng e lbrech t , and J . H. Aus t in , F r ee -L iv ing N em atod eR e m o v a l b y R a p i d S a n d F i l t e r s , P r o c . A m . S oc . C i v . E n g . , J . S a n . E n g . D i v . ,vol . 92, No. SA 1, pp. 229-243, F eb rua ry 1966.

[5 ] K a w a m u r a , S u s u m u , D e s i g n a n d O p e r a t i o n o f H i g h - R a t e F i l t er s - P a r t 1 ,J . Am. Water Works Assoc. , vol . 67, pp. 535-544, October 1975.

[6 ] C u l p , G . L . , a n d R . L . C u l p , N e w C o n c e p ts i n W a t e r P u r i f i c a t i o n , V a nN o s t r a n d R e i n h o l d C o . , N e w Y o rk , N . Y . , 3 0 5 p p . , 1 97 4.

[7 ] K a w a m u r a , S u s u m u , D e s i g n a n d O p e r a t i o n o f H i g h - R a t e F i l t e rs - P a r t 2 ,J . Am. Water Works Assoc. , vol . 67, pp. 653-662, November 1975.

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[8] A mirth arajah , A. , and J . L. Cleasby, Pre dict in g Expa nsion of Fi l ters D uringBa ckw ash, J . Am . Water W orks Assoc., vol. 64 , No. 1 , pp . 52-59, Jan ua ry 1972.

[9 ] Sanks , R . L . (ed ) ., W ater Tre a tm en t P la n t Des ign fo r the Prac t ic ing Eng ineer ,Ann A rbor Science Publ ishers , Inc. , Ann A rbor, Mic h. , 845 pp. , 1978.

[10] Hazen and Sawyer , Eng ineers , Process Des ign M anu al fo r Suspended So lidsRe mo val , rev . ed . , Env i ron Pro t Agency , Techno l . Trans . , v .p . , Janua ry 1975 .

[11] Adin , A. , E . R . Bau man n , and J . L . C leasby , Th e Appl ica t ion o f F i l t ra tionTh eor y to Pi lo t-P lant D esign , J . Am . Wate r W orks Assoc., vol. 71 , No. 1 ,pp. 17-27, 1979.

[12] In te rna t iona l Garr ison Divers ion S tudy Board Re por t to the In te rna t iona l Jo in tCommission (U.S. and Canada Boundary Commission), October 1976.