BIOLOGICAL TREATMENT OF CONCENTRATED SUGAR BEET WASTES
By
J a m e s H. F i s c h e r
P r o j e c t 12060 FAK P r o g r a m Element 1 BB037
Roap/Task 21 BAB 82 P r o j e c t Officer
Ralph H. Scott
P a c i f i c Northwest E n v i r o n m e n t a l R e s e a r c h L a b o r a t o r y National E n v i r o n m e n t a l R e s e a r c h C e n t e r
C o r v a l l i s , Oregon 97330
P r e p a r e d for
O F F I C E OF RESEARCH AND DEVELOPMENT U . S . ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D . C . 20460 Gardens Point
A22450084B
Biological treatment of concentrated sugar beet wastes
E P A - 6 6 0 / 2 - 7 4 - 0 2 8 June 1974
ABSTRACT
A study of the variables influencing a closed loop r e c i r c u l a t i n g flume water s y s t e m for conveying sugarbeets for p r o c e s s i n g was conducted at Longmont, Colorado. The r e s u l t s show that high volume, high total solids t r a n s p o r t (flume) w a t e r s can be r e c i r c u l a t e d with little or no discharge to receiving w a t e r s . Rapid removal of suspended solids was accomplished by screening, followed by continuous addition of lime p r i o r to sedimentation. The build-up of total dissolved solids was no major problem during the operation p e r i o d s , provided the pH was 10 or g r e a t e r and that water t e m p e r a t u r e did not exceed 20°C.
The s y s t e m was designed for p r i m a r y settling in two a l t e r n a t e l y used ponds. Settled mud was removed from one pond by c l a m s h e l l while the other one was in s e r v i c e . The first settling pond effluent was s u b - jected to secondary settling before returning to the fluming and washing o p e r a t i o n s . These segments of t r e a t m e n t e s s e n t i a l l y operated without odor.
A deep anaerobic pond designed to degrade r e m a i n i n g solids in the s u r - plus water was effectively used to t r e a t the total s y s t e m w a t e r s at the end of each operating campaign. Floating surface a e r a t o r s were used with s u c c e s s the first y e a r to reduce odor but failed to be consistently effective the second y e a r . The a e r a t o r s were effective in helping final polishing to meet discharge s t a n d a r d s .
Biological and nutritional data were collected to evaluate operational quality, water quality and bio-activity. While the r e s u l t s indicate that the end product water m e e t s discharge s t a n d a r d s , such t r e a t e d wastes w e r e retained for r e - u s e in the s y s t e m . F u r t h e r work is needed on mud handling and odor abatement.
This r e p o r t was submitted in fulfillment of P r o j e c t Number 12060 FAK by the Beet Sugar Development Foundation under p a r t i a l s p o n s o r s h i p by the Environmental Protection Agency. "Work was completed as of October 1970.
CONTENTS
P a g e
A b s t r a c t ii L i s t of F i g u r e s iv
L i s t of T a b l e s v Section
I Conclusions 1 II R e c o m m e n d a t i o n s 3
III Introduction 5 VI Design and Construction 9
V E x p e r i m e n t a l
G e n e r a l 15 S a m p l e Collection 16
A n a l y t i c a l P r o c e d u r e s 17 VI D i s c u s s i o n
L i m e Addition and pH 19
Solids R e m o v a l 24 D i s s o l v e d Solids, COD, BOD in R e c i r c u l a t e d
W a t e r 28 A n a e r o b i c Pond 32
VII Bibliography 47 VIII A p p e n d i c e s , A n a l y s i s of data 51
SECTION I CONCLUSIONS
T h e p r i n c i p l e of t o t a l r e c i r c u l a t i o n of s u g a r b e e t factory flume a n d w a s h w a t e r s h a s been p r o v e n t o b e s u c c e s s f u l . Best r e s u l t s a r e o b - t a i n e d when a d e q u a t e q u a n t i t i e s of l i m e , as CaO, a r e c o n t i n u o u s l y i n - j e c t e d into t h e s y s t e m at a r a t e sufficiently high to p r o d u c e a pH g r e a t e r than 10. To m a i n t a i n a high pH w i t h m i n i m u m l i m e a d d i t i o n ,
t h e s y s t e m w a t e r s should be kept under 2 0 ° C . I Under the above conditions, s e t t l e a b l e s o l i d s can be r a p i d l y c o n c e n -
t r a t e d into a m u d that can be r e m o v e d in ponds or in a t y p i c a l c l a r i - f i e r . The s u p e r n a t a n t can b e r e t u r n e d w i t h m i n i m u m r e t e n t i o n o r n o r e t e n t i o n t o r e p e a t the f l u m i n g - w a s h i n g c y c l e . The continuous b u i l d - up of d i s s o l v e d s o l i d s does not i n t e r f e r e w i t h the h y d r a u l i c s but d o e s a g g r a v a t e the foaming p r o b l e m . O d o r s a r e not a p r o b l e m u n d e r high p H c o n d i t i o n s .
The l o s s of s y s t e m w a t e r with the s e t t l e d m u d s e e m s to equal an i n h e r e n t m a k e - u p . N o w a t e r n e e d s t o b e d i s c h a r g e d during a n o p e r a t i n g c a m p a i g n , t h e r e f o r e , t h e r e n e e d b e n o c o n c e r n o v e r w a t e r quality f r o m t h i s s o u r c e .
R e m o v a l and handling of s e t t l e d mud, h o w e v e r , is a continuous p r o b l e m . After a n o p e r a t i n g campaign the s y s t e m w a t e r s a r e b i o - d e g r a d a b l e a n d c a n be ponded for r e - u s e as has been done at Longmont for 3 y e a r s c o n - s e c u t i v e l y . None of the m e t h o d s u s e d to d a t e has a c c o m p l i s h e d t h e d e g r a d a t i o n p r o c e s s without p e r i o d s of h i g h o d o r s . A t r u e a n a e r o b i c or a e r o b i c condition w a s n e v e r a t t a i n e d w i t h o r without m e c h a n i c a l s u r f a c e a e r a t i o n ; a facultative condition e x i s t e d . However, t h e r e s i d u e w a t e r r e c e i v e d sufficient t r e a t m e n t t o m e e t d i s c h a r g e quality s t a n d a r d s even though the t i m e r e q u i r e d e x c e e d e d e x p e c t a t i o n s .
SECTION II RECOMMENDATIONS
The Longmont w a s t e w a t e r t r e a t m e n t s y s t e m , with m o d i f i c a t i o n s , i s r e c o m m e n d e d for u s e i n g e o g r a p h i c a l a r e a s w h e r e the s y s t e m w a t e r s d o not e x c e e d 2 0 ° C . Higher t e m p e r a t u r e s i n c r e a s e f e r m e n t a t i o n r a t e s and l i m e r e q u i r e m e n t s . Even then, the l i m i n g p r i n c i p l e does have a p p l i c a t i o n as an e c o n o m i c a i d to h a s t e n settling of s o l i d s .
Two m a i n p r o b l e m s r e m a i n t o b e solved. I t i s r e c o m m e n d e d that
f u r t h e r r e s e a r c h be conducted on the d e w a t e r i n g and t r a n s p o r t of s e t t l e d m u d . Odor p r o d u c t i o n f r o m s e t t l e d m u d in ponds continues for p r o l o n g e d p e r i o d s of t i m e . S t a n d a r d m e t h o d s of d e w a t e r i n g a r e e i t h e r too c o s t l y or do not p e r f o r m to s a t i s f a c t i o n u n d e r n o r m a l c o n d i t i o n s .
F u r t h e r r e s e a r c h is r e c o m m e n d e d on the t r e a t m e n t of end of c a m p a i g n r e s i d u e w a t e r . The a n a e r o b i c o r facultative m e t h o d s o f t r e a t m e n t p r o - duce u n p l e a s a n t o d o r s . S e v e r a l t y p e s of a e r o b i c s y s t e m s should be t r i e d on s u g a r b e e t w a s t e s . B e c a u s e of l i m i t e d land a v a i l a b i l i t y at m a n y factory s i t e s , the a e r o b i c a p p r o a c h would not b e a p p l i c a b l e t o a l l f a c t o - r i e s . I t i s r e c o m m e n d e d t h a t f u r t h e r studies b e conducted o n a n a e r o b i c - facultative ponds using c o v e r i n g s or c o n t r o l l e d d i g e s t i o n with specific o r g a n i s m s .
SECTION III INTRODUCTION
The p r o c e s s of refining s u g a r f r o m s u g a r b e e t s o r i g i n a t e d in E u r o p e following the f i r s t a c t u a l proof by A n d r e a s Marggraf, a G e r m a n c h e m i s t , in 1747 (2) that b e e t r o o t s contained s u g a r . No u s e w a s m a d e of t h i s d i s c o v e r y until 1799 when one of his p u p i l s , F r a n z K a r l A c h a r d , r e - c o v e r e d s u g a r f r o m a s m a l l planting of s u g a r b e e t s . Napoleon h i m s e l f o r d e r e d the f i r s t l a r g e - s c a l e planting o f s u g a r b e e t s and t h e e x t r a c t i o n of s u g a r f r o m the r o o t s in 1811. Although s o m e evidence e x i s t s t h a t the C a l i f o r n i a Indians e x t r a c t e d s u g a r f r o m b e e t s p r i o r t o the E u r o p e - an d e v e l o p m e n t , the E u r o p e a n continent is c r e d i t e d as the b i r t h p l a c e of t h e beet s u g a r i n d u s t r y .
Following n u m e r o u s u n s u c c e s s f u l efforts, the f i r s t g e n e r a l l y a c c e p t e d c o m m e r c i a l s u c c e s s t o p r o d u c e s u g a r from s u g a r b e e t s i n the United S t a t e s is acknowledged to have been a c c o m p l i s h e d by E. H. Dyer at A l v a r a d o , C a l i f o r n i a in 1879 (20).
The f a c t o r y at A l v a r a d o continued in o p e r a t i o n t h r o u g h 1967 at which t i m e the Holly Sugar C o r p o r a t i o n e l e c t e d t o t e r m i n a t e i t s o p e r a t i o n and d i s m a n t l e the e q u i p m e n t . One of the significant influences on the d e - cision by Holly to t e r m i n a t e a n e a r - c e n t u r y o p e r a t i o n was t h e p r o b l e m and c o s t of w a s t e d i s p o s a l . The e n c r o a c h m e n t of the Bay a r e a p o p u l a - tion a r o u n d t h e f a c t o r y s i t e c r e a t e d n u m e r o u s p r o b l e m s i n c o m m u n i t y - i n d u s t r y r e l a t i o n s . T h i s h i s t o r i c b e e t s u g a r f a c t o r y t h u s has y i e l d e d t o u r b a n i z a t i o n . T h i s is a t y p i c a l e x a m p l e of s i m i l a r conditions e x i s t i n g a t o t h e r b e e t s u g a r f a c t o r y s i t e s a n d with o t h e r p r o c e s s i n g i n d u s t r i e s . The technology of A m e r i c a n i n d u s t r y has not yet a d v a n c e d to the point w h e r e f a c t o r i e s a r e w e l c o m e t o o p e r a t e adjacent t o r e s i d e n t i a l and b u s i n e s s a r e a s . P e r h a p s the day will come a s p r o c e s s i n g t e c h n i q u e s b e c o m e m o r e s o p h i s t i c a t e d . E a c h p r e s e n t - d a y d e v e l o p m e n t i n e n v i r o n - m e n t a l c o n t r o l is a building b l o c k in t h i s d i r e c t i o n .
The b e e t s u g a r i n d u s t r y i s a t y p i c a l A m e r i c a n b u s i n e s s e n t e r p r i s e . I t h a s i t s p r o b l e m s of a i r and w a t e r pollution. With t h e advent of i n c r e a s - ing p u b l i c s e n t i m e n t t o c l e a n o u r a i r and w a t e r , i t b e h o o v e s t h e s u g a r i n d u s t r y t o r e d u c e its contribution t o pollution a s r a p i d l y a s technology and e c o n o m i c s p e r m i t .
The w o r k h e r e r e p o r t e d is e s s e n t i a l l y devoted to the p r o b l e m s of t r e a t - i n g and d i s p o s i n g o f w a s t e s e n c o u n t e r e d i n t h e w a t e r u s e d t o t r a n s p o r t
t h e b e e t s in the factory and to wash the b e e t s . O t h e r s o u r c e s of
w a s t e such as p r o c e s s w a t e r , lime cake d r a i n a g e , Steffen p r o c e s s w a s t e , c o n d e n s e r waste, e t c . will be mentioned from t i m e to t i m e only to place the e n t i r e discharge of w a s t e s from a beet s u g a r f a c t o r y into p e r s p e c t i v e . S e v e r a l sources have r e p o r t e d (20) that the t o t a l w a s t e load f r o m a
factory capable of p r o c e s s i n g 2, 000 tons of b e e t s p e r day is roughly equivalent to that from a city of 252, 000 people. E l d r i d g e (8) r e p o r t s that 17. 6 percent of the 5-day Biochemical Oxygen Demand (BOD5) d i s -
c h a r g e from a factory will be in the flume w a t e r . However, t h i s d i s - c h a r g e accounts for 72. 1 percent of the hydraulic v o l u m e . E x c e p t e d f r o m t h e s e figures is condenser w a t e r , a high volume, low BOD5 w a s t e .
Recent r e p o r t s by v i s i t o r s returning from E u r o p e have s t a t e d that c o n - s i d e r a b l e success has been experienced in both w a t e r c o n s e r v a t i o n and w a s t e t r e a t m e n t by applying recirculation or c l o s e d - l o o p s y s t e m s to t h e high volume water r e q u i r e m e n t s of a factory. P a r t i c u l a r l y t h e s e r e p o r t s apply to the fluming and condenser w a t e r s . In the c a s e of fluming w a t e r , l i m e as CaO has been m e t e r e d into the w a t e r to h a s t e n p r e c i p i t a t i o n of s e t t l e a b l e solids and to r e t a r d b a c t e r i a l r e p r o d u c t i o n .
S e v e r a l significant differences exist between E u r o p e a n and N o r t h
A m e r i c a n beet sugar p r o c e s s i n g c a m p a i g n s . I n the f i r s t p l a c e , E u r o p e a n c a m p a i g n s a r e s h o r t e r than the a v e r a g e U . S . c a m p a i g n s and a r e l i m i t e d to late fall and e a r l y w i n t e r . Secondly, n e a r l y half of the U . S . beet s u g a r production comes from sugarbeet r o o t s that have been s t o r e d in l a r g e open p i l e s , w h e r e a s , only a s m a l l p e r c e n t a g e of the European b e e t s h a s been subjected to short s t o r a g e p e r i o d s in s m a l l o n - t h e - f a r m p i l e s . T h i r d l y , the climate in w e s t e r n E u r o p e is quite uniform t h r o u g h the e n t i r e p r o c e s s i n g season with s m a l l t e m p e r a t u r e c h a n g e s . I n c o n t r a s t , t h e N o r t h A m e r i c a n sugarbeet p r o c e s s i n g c a m p a i g n s a r e i n p r o g r e s s , a t one location or another, 12 months ot the y e a r .
E u r o p e a n sugarbeet production and p r o c e s s i n g p r a c t i c e s cannot be t r a n s - lated to North A m e r i c a without modification to c o r r e c t for e n v i r o n m e n t a l influences. The s a m e is t r u e within the North A m e r i c a n continent.
Operational p r o c e d u r e s in the southern p a r t of California and s o u t h e r n A r i z o n a a r e quite different from those in North Dakota and Montana, and t h e p r o v i n c e s of Canada.
P r i o r to initiating this study the influence of g e o g r a p h i c a l location w a s recognized. The proposed plan of operation included an a n a l y t i c a l p r o g r a m to guide the s y s t e m operation and to p r e d i c t the a d a p t a b i l i t y of l i m e d , recirculating (or closed loop) flume water s y s t e m s to different f a c t o r y s i t e s . It was a g r e e d that a modified a p p r o a c h to s e v e r a l s u c c e s s .
ful E u r o p e a n s y s t e m s of t h i s type showed c o n s i d e r a b l e p r o m i s e for a d a p t a t i o n in the N o r t h A m e r i c a n continent. At t h e t i m e of p r o j e c t p l a n - n i n g s o m e l i m i t e d t r i a l s with l i m e d , r e c i r c u l a t i n g flume w a t e r w e r e a l s o b e i n g p l a n n e d b y s e v e r a l U . S . and Canadian beet s u g a r c o m p a n i e s .
F o l l o w i n g s e v e r a l i n d u s t r y - w i d e c o n f e r e n c e s on the subject of f l u m e w a s t e w a t e r t r e a t m e n t , the i n d u s t r y a g r e e d to begin a study of t h e p r o b - l e m t h r o u g h t h e Beet Sugar Development Foundation. A n a p p l i c a t i o n for
s u p p o r t i n g funds was s u b m i t t e d to t h e E n v i r o n m e n t a l P r o t e c t i o n A g e n c y ( f o r m e r l y t h e F e d e r a l Water Quality A d m i n i s t r a t i o n ) . The p r o p o s a l s u g g e s t e d t h e c o n s t r u c t i o n of a f u l l - s c a l e r e c i r c u l a t i n g s y s t e m at T h e G r e a t W e s t e r n Sugar Company a t Longmont, C o l o r a d o . Longmont i s w i t h i n a g e o g r a p h i c a l a r e a which h a s c l i m a t i c conditions r e l a t i v e l y m e a n t o t h o s e e x i s t i n g within t h e s t a t e s w h e r e p r o c e s s i n g p l a n t s a r e l o c a t e d .
T h e o b j e c t i v e s w e r e to develop a s y s t e m for e c o n o m i c t r e a t m e n t of s u g a r b e e t f a c t o r y f l u m e (conveying and washing) water p e r m i t t i n g its r e - u s e in a r e c i r c u l a t i n g fluming s y s t e m . The s y s t e m should o p e r a t e w i t h o u t o d o r d u r i n g a n d following the c a m p a i g n . Any w a t e r s u r p l u s f r o m t h e s y s t e m d u r i n g o p e r a t i o n , a s w e l l a s the r e s i d u a l w a t e r after c a m p a i g n , w a s t o b e t r e a t e d i n a m a n n e r t o m e e t d i s c h a r g e quality s t a n d a r d s .
T h e plan of o p e r a t i o n c a l l e d for the addition of l i m e , c a u s t i c s or o t h e r c h e m i c a l s to d e t e r m i n e t h e i r effectiveness on c o n t r o l of pH, r e m o v a l of s e t t l e a b l e s o l i d s and r e t e n t i o n t i m e . The p r e c i s e t r e a t m e n t for t h e s u r p l u s and r e s i d u a l w a t e r w a s not d e s c r i b e d s i n c e r e s u l t s o f r e s e a r c h i n p r o g r e s s w e r e being a w a i t e d . U l t i m a t e l y , the a n a e r o b i c a p p r o a c h w a s s e l e c t e d by employing t h e p r i n c i p l e of deep ponding and s u r f a c e a e r a t i o n .
SECTION IV
DESIGN AND CONSTRUCTION
T h e t y p i c a l s u g a r b e e t p r o c e s s i n g f a c t o r y i s designed t o p r o c e s s e i t h e r f r e s h l y - h a r v e s t e d s u g a r b e e t s d i r e c t l y f r o m f a r m e r s ' fields d e l i v e r e d b y r a i l o r t r u c k o r f r o m l a r g e s t o r a g e p i l e s located a t o r n e a r a f a c t o - r y . A l l s u g a r b e e t s a r e m e c h a n i c a l l y h a r v e s t e d b y t h e f a r m e r (or a c o n - t r a c t o r ) and d e l i v e r e d t o r e c e i v i n g stations located o n t h e f a c t o r y p r e - m i s e s a n d a t convenient outlying s i t e s . The r e c e i v i n g s t a t i o n s a r e e q u i p p e d with d r y m e c h a n i c a l c l e a n i n g devices t o s e p a r a t e the m o s t e a s i l y - r e m o v e d d i r t , c l o d s , r o c k s , weeds and g r e e n leaf m a t e r i a l f r o m t h e f r e s h r o o t s . I n s o m e s t a t e s the t a r e ( r e m o v e d m a t e r i a l ) i s r e t u r n e d to t h e individual f a r m e r ' s field; in other s t a t e s it m u s t be r e t a i n e d at a
s i n g l e l o c a t i o n by t h e s u g a r c o m p a n y . Most of t h e additional a d h e r i n g d i r t and e x t r a e n e o u s m a t e r i a l i s r e m o v e d from the b e e t s a t the f a c t o r y b y t h e fluming and washing o p e r a t i o n s .
E a c h b e e t s u g a r f a c t o r y has an individual design for fluming and w a s h i n g o p e r a t i o n s . With few e x c e p t i o n s , e a c h one will have a r e c e i v i n g h o p p e r o r h o p p e r s w i t h flume w a t e r underflow. Some i n s t a l l a t i o n s , p a r t i c u l a r l y f o r r a i l d e l i v e r i e s , will have high p r e s s u r e o v e r h e a d h o s e s that a s s i s t i n e v a c u a t i n g the c a r s . I n cold c l i m a t e s , the w a t e r s o u r c e t o the o v e r h e a d s o u r c e s is h e a t e d to thaw t h e frozen c o n g l o m e r a t e of s u g a r b e e t s , mud, d i r t , r o c k s , e t c .
F r o m t h e r e c e i v i n g h o p p e r s , t h e flume w a t e r t r a n s p o r t s b e e t s t h r o u g h a s e r i e s of cleaning d e v i c e s to r e m o v e sand, r o c k s , clods, o r g a n i c m a t t e r , m e t a l , e t c . A final h i g h - p r e s s u r e s p r a y above the s p r a y r o l l e r s is t h e l a s t c l e a n i n g o p e r a t i o n p r i o r to the slicing of the s u g a r b e e t s into c o s s e t t e s .
H i s t o r i c a l l y , t h e flow design for fluming and washing p r o v i d e d for f r e s h w a t e r input t o the s y s t e m and the d i s c h a r g e t o holding ponds o r t o r e - c e i v i n g w a t e r b o d i e s . The d e s i g n r e p o r t e d i n t h i s study p r o v i d e s for t h e c o m p l e t e c o n t a i n m e n t and r e c i r c u l a t i o n of a l l fluming and w a s h w a t e r .
T h e s c h e m a t i c flow d i a g r a m , F i g u r e 1, will show an e a r l y and i m p o r t t a n t d e c i s i o n m a d e i n d e s i g n i n g t h e flow p a t t e r n . The t o t a l f l u m e a n d w a s h w a t e r flow i s not l i m e d . A p p r o x i m a t e l y one half i s r e t u r n e d t o t h e f l u m e s f r o m t h e s c r e e n s without being l i m e d . T h e r e m a i n d e r o f t h e flow is l i m e d , c l a r i f i e d a n d r e t u r n e d to the flume w h e r e it is m i x e d
w i t h t h e u n t r e a t e d flow. T h e p r o p o r t i o n of t r e a t e d to u n t r e a t e d flow b e - c o m e s a p a r t of the study.
I n d i s c u s s i n g t h e design and c o n s t r u c t i o n , only t h o s e s y s t e m components w h i c h a r e unique to the p r o j e c t will be given c o n s i d e r a t i o n . A d i s c u s - s i o n of t y p i c a l h y d r a u l i c c o m p o n e n t s will be i n c l u d e d only if they have h a d p a r t i c u l a r influence o n the o p e r a t i o n and r e s u l t s .
F I G U R E 1. SCHEMATIC FLOW DIAGRAM OF LONGMONT F L U M E SYSTEM.
T h e e x i s t i n g fluming s y s t e m at the Longmont f a c t o r y of The G r e a t W e s t e r n S u g a r Company between the r e c e i v i n g h o p p e r s and the s p r a y r o l l e r s w a s only slightly modified. One m a j o r change was m a d e at t h e c o n f l u e n c e o f s e v e r a l w a s t e s t r e a m s before t h e i r d i s c h a r g e t o the old s e t t l i n g p o n d s . The design provided for the collection of the flume w a t e r i n t o a s u m p at which point it is pumped up into a manifold
s u p p l y i n g w a s t e w a t e r t o the elevated s c r e e n s . V a l v e s c o n t r o l the flow t o e a c h s c r e e n ( F i g u r e 2).
FIGURE 2. E L E V A T E D DSM SCREENS SHOWING MANIFOLD AND VALVE SYSTEM.
FIGURE 3. PARSHALL F L U M E AND HOSE ARRANGEMENT F O R ADDITION OF MILK OF L I M E .
The final screen design included five stationary s c r e e n s o p e r a t i n g in parallel. Four of the s c r e e n s w e r e D o r r - O l i v e r DSM s c r e e n s . T h r e e had 3 mm openings and one screen had 6 mm openings between the s t a i n - l e s s steel b a r s . The fifth s c r e e n was of s i m i l a r d e s i g n . However, it had a longer and wider contact a r e a with 6 mm openings. The r e j e c t s from the screens drop to a t r a s h platform and t h e underflow is collected in a receiving manifold. The manifold divides the flow, about half of which r e t u r n s to the flumes. This flow is m e t e r e d . The r e m a i n d e r of the flow (that which is treated) is m e a s u r e d through a P a r s h a l l F l u m e (at which point milk of lime is added, see F i g u r e 3), p a s s e s through a mixing box and is piped to the first settling ponds, only one of which is used at a given t i m e .
Considerable discussion p r e c e d e d the decision to u s e the two-pond design, r a t h e r than install a typical c l a r i f i e r . Both plans would r e - quire a s y s t e m for handling settled mud. The s e l e c t e d design r e q u i r e s c l a m s h e l l removal of settled mud from the a l t e r n a t e l y - u s e d f i r s t ponds during campaign. The selected design does not r e p r e s e n t a p r e f e r e n c e , but a means to reduce initial capital investment.
F i g u r e s 1 and 4 show the two s e m i c i r c u l a r f i r s t ponds lying outside t h e p e r i m e t e r of the c e n t r a l second settling pond. The flow can be d i r e c t e d to either of the first ponds, the duration of flow to each being dictated by the r a t e the settled mud accumulates and the p e r c e n t a g e of s e t t l e - a b l e solids remaining in the f i r s t pond effluent. Since evacuation of m u d from the ponds is accomplished by c l a m s h e l l , wide dikes w e r e planned to p e r m i t e a s e of a c c e s s .
Flow to the second settling pond from either of the first ponds is by g r a v i t y . In addition to the second pond serving as a second settling pond, it s e r v e s as a s u r g e b a s i n . F r o m the second pond, water is pumped back to the flumes thus completing the c y c l e .
The anaerobic pond located to the side of the first and second ponds s e r v e s as a r e s e r v o i r . Water can be introduced into this pond t h r o u g h a gravity syphon flowing from the second pond or can be pumped d i r e c t l y to the pond from the recirculating s y s t e m . T r a n s p o r t water is p u m p e d from the flumes and the first and second ponds at the end of c a m p a i g n . Conversely, anaerobic pond water can be pumped back to the r e c i r c u l a t - ing system as make-up w a t e r .
FIGURE 4. AERIAL PHOTO OF P R O J E C T SITE AND T R E A T M E N T PONDS.
The h y d r a u l i c design included p r o v i s i o n s for e m e r g e n c y d i s c h a r g e . Should t h e a n a e r o b i c pond be unable to contain the s u r p l u s w a t e r s , w a t e r is w a s t e d t h r o u g h a standpipe to a slough, and t h e n c e to t h e r i v e r . S i m i l a r l y , w a t e r can be w a s t e d to the l i m e holding ponds w h e r e the o t h e r m i s c e l l a n e o u s f a c t o r y w a s t e s a r e r e t a i n e d .
SECTION V E X P E R I M E N T A L
G e n e r a l
It is i m p o r t a n t to m e n t i o n that the e x p e r i m e n t a l work d e s c r i b e d in t h i s r e p o r t was s u p e r i m p o s e d upon the c o m m e r c i a l p r o c e s s i n g schedule of the Longmont f a c t o r y of T h e G r e a t W e s t e r n Sugar Company. Ideal conditions for e x p e r i m e n t a l c o n t r o l w e r e not always p r e s e n t . In recognition of the t y p i c a l events that t r a n s p i r e during a p r o c e s s i n g campaign, the design was developed t o m i n i m i z e i n t e r f e r e n c e with the n o r m a l o p e r a t i o n . Under e x i s t i n g c o n d i t i o n s , the v a r i a b l e quantity of s u g a r b e e t s d e l i v e r e d to the f l u m e s , the changing w a t e r flow r a t e s , changes in w a t e r t e m p e r a - t u r e s and o t h e r v a r i a b l e s w e r e n o r m a l o p e r a t i o n a l fluctuations. The c o n t r o l and a n a l y t i c a l s c h e d u l e s w e r e designed t o meet t h e s e v a r i a b l e conditions as they developed. A fully-equipped mobile l a b o r a t o r y was moved to a l o c a t i o n on the factory p r e m i s e s conveniently n e a r t h e s a m p - ling p o i n t s . The existing factory p r o c e s s c o n t r o l l a b o r a t o r y was i n a d e - quate t o p r o v i d e i n c r e a s e d a n a l y t i c a l a c t i v i t y .
The s a m p l i n g and a n a l y t i c a l schedule allowed for the m e a s u r e m e n t of a l l flows w a s t e d f r o m the factory excluding d o m e s t i c w a s t e s . Although t h i s study was p r i m a r i l y conducted o n the flume w a t e r , s a m p l e s w e r e r o u t i n e - ly collected f r o m t h e c o n d e n s e r w a t e r s e w e r and on i r r e g u l a r schedule f r o m other w a s t e s t r e a m s . A s unusual situations developed, supporting b e n c h and s y s t e m s t u d i e s w e r e conducted. R e p o r t s of t h e s e a r e appended a s p a r t o f t h i s r e p o r t .
The e x p e r i m e n t a l r e s u l t s r e p o r t e d c o v e r the two operating campaigns of 1967-68 and 1968-69. The p r i n c i p a l e m p h a s i s has been p l a c e d on the 1968-69 data s i n c e s o m e i r r e g u l a r i t i e s i n the s y s t e m ' s p h y s i c a l p e r - f o r m a n c e d u r i n g the f i r s t y e a r influenced the validity of s o m e of the r e - s u l t s . D e s i g n modifications p r i o r t o t h e second campaign c o r r e c t e d n e a r - ly a l l of the h y d r a u l i c p r o b l e m s which had confounded t h e 1967-68 r e s u l t s .
In m o s t i n s t a n c e s the s a m p l e s for c h e m i c a l a n a l y s i s w e r e t a k e n at the s a m e location and a t the s a m e t i m e a s t h o s e for biological a n a l y s i s . T h e c h e m i c a l s a m p l e s and p h y s i c a l data w e r e a c q u i r e d and p r o c e s s e d a t Longmont. The biological s a m p l e s w e r e shipped i m m e d i a t e l y after c o l l e c t i o n to the D e p a r t m e n t of Microbiology at C o l o r a d o State U n i v e r s i - ty in F o r t Collins for p r o c e s s i n g . The d a t a w e r e evaluated by c o m p u t e r a t the S t a t i s t i c a l L a b o r a t o r y , C o l o r a d o State U n i v e r s i t y .
In o r d e r to a s c e r t a i n the fate of the c h e m i c a l and b i o l o g i c a l c o n s t i t u e n t s in the s y s t e m , five s i t e s w e r e s e l e c t e d as s a m p l i n g s t a t i o n s ( F i g u r e 1).
T h e f i r s t pond influent (FPI) was d e s i g n a t e d as the i n i t i a l s a m p l i n g point.
T h e a c t u a l sampling point was located 6 feet d i s t a n t from the d i s c h a r g e of t h e pipe c a r r y i n g w a t e r from the P a r s h a l l flume and l i m e mixing box i n t o the ponding a r e a . S a m p l e s collected at t h i s point contained the m i x e d s c r e e n e d underflow and s l u r r i e d l i m e .
T h e second point of sampling was l o c a t e d 6 feet distant f r o m t h e d i s - c h a r g e of the overflow between the f i r s t and second ponds and w a s d e s i g - n a t e d a s the second pond influent (SPI). T h i s s i t e w a s s e l e c t e d t o d e - t e r m i n e the r a t e of which suspended s o l i d s would s e t t l e in the p r i m a r y p o n d and to d e t e r m i n e the r a t i o of p e r c e n t s e t t l e a b l e solids r e m o v e d to d e t e n t i o n t i m e .
T h e t h i r d sampling point was at t h e outlet of t h e second pond at which p o i n t the w a t e r was r e t u r n e d , by pumping, to the f l u m e s . This site was s e l e c t e d as the o p e r a t i o n s c o n t r o l point. At this location t h e t o t a l
c h a n g e o c c u r r i n g a c r o s s the ponds would b e m a x i m u m . T h e differences b e t w e e n the F P I and S P E reflected the r e m o v a l efficiency of the pond
s y s t e m and the SPE values e s t a b l i s h e d t h e amount of l i m e addition for e a c h s e l e c t e d p H p a r a m e t e r .
T h e fourth sampling points w e r e located in t h e a n a e r o b i c pond. Two r e p r e s e n t a t i v e locations w e r e e s t a b l i s h e d on the pond c e n t e r l i n e that w e r e equal distance f r o m each other and the opposite two s h o r e l i n e s . T h e s e points w e r e each s a m p l e d a t 3-foot v e r t i c a l i n t e r v a l s . Initially, an a t t e m p t was m a d e to d e t e r m i n e depth and location d i f f e r e n c e s . Since d i f f e r e n c e s between depth i n t e r v a l s and location for both p h y s i c a l and b i o l o g i c a l data w e r e m i n i m a l , individual a n a l y s e s w e r e abandoned.
H o w e v e r , the sampling p r o c e d u r e was m a i n t a i n e d to produce an a n a e r o b i c p o n d depth c o m p o s i t e (APDC).
Sample Colletion
The fifth s a m p l i n g point was at the a n a e r o b i c pond effluent (APE).
During the 1967-68 c a m p a i g n t h e r e was a planned and continual dis- c h a r g e f r o m t h i s point which r e q u i r e d m a k e - u p w a t e r . During the 1968-69 c a m p a i g n t h e r e was no d i s c h a r g e from the a n a e r o b i c pond, thus n o s a m p l e s w e r e t a k e n ; infrequent m a k e - u p water was r e - q u i r e d .
Automatic s a m p l e r s w e r e u s e d at the f i r s t pond influent, second pond influent and s e c o n d pond effluent. The automatic s a m p l e r s w e r e u s e d to collect s a m p l e s for c h e m i c a l a n a l y s i s only and w e r e t i m e - p r o g r a m m e d to collect a t o t a l of 2. 5 gallons d u r i n g a 24-hour p e r i o d at a r a t e of 12
s u b - s a m p l e s p e r h o u r . The s a m p l i n g t u b e s w e r e p r o t e c t e d from
freezing with heat t a p e s . S t a n d a r d g r a b methods w e r e used for s u r f a c e and depth s a m p l e s for d i s s o l v e d oxygen, BOD5, and biological a n a l - y s i s (1).
The a n a l y t i c a l s c h e d u l e , a n a l y t i c a l p r o c e d u r e s and a d e s c r i p t i o n of s a m p l i n g m e t h o d s u s e d a r e shown in T a b l e s 20 through 32 and in the appendix.
A n a l y t i c a l P r o c e d u r e s
The n u m e r o u s q u e s t i o n s r e l a t i n g to t h e efficiency and operation of the s y s t e m w e r e of h y d r a u l i c , m e c h a n i c a l , c h e m i c a l and biological n a t u r e . It b e c a m e a p p a r e n t that e a c h of the s t r e a m flows a s s o c i a t e d withthe
s y s t e m r e q u i r e d quantitative e v a l u a t i o n . E a c h of the flows was m e a s - u r e d with an a p p r o p r i a t e m e t e r i n g d e v i c e . Although the p e r f o r m a n c e of s t a n d a r d p u m p s , s c r e e n s , v a l v e s , e t c . w e r e known, s o m e questions con- c e r n i n g d u r a b i l i t y u n d e r the d e s i g n conditions w e r e not a n s w e r e d until p l a c e d u n d e r t e s t .
The bulk of t h e a n a l y t i c a l p r o g r a m involved the completion of the c h e m - i c a l and b i o l o g i c a l a n a l y s e s . T a b l e 22 in the appendix gives a d e t a i l of the routine schedule for the p r i m a r y constituents believed to have an influence on t h e s y s t e m p e r f o r m a n c e . E a c h of the a n a l y s e s was r a t h e r routine excepting that for t o t a l c a r b o n . It had been r e p o r t e d that a m e a s u r e of the o r g a n i c c a r b o n in w a s t e w a t e r might prove to be an a c c u r a t e s u b s t i t u t e for m e a s u r i n g B O D5 loads in waste water (37).
A t o t a l o r g a n i c c a r b o n a n a l y z e r was used to obtain a value which was then r e l a t e d to both B O D5 and COD m e a s u r e m e n t s . Table 24 in the appendix outlines the a n a l y t i c a l s c h e d u l e for biological a n a l y s e s . Since
t h e b i o - s a m p l e s w e r e a c q u i r e d differently than t h e c h e m i c a l s a m p l e s , c h e m i c a l a n a l y s e s w e r e a l s o p e r f o r m e d on a c o m p o s i t e of weekly b i o - s a m p l e s . T a b l e 25 in the appendix gives the a n a l y t i c a l s c h e d u l e s for t h e weekly mud s a m p l e s c o m p o s i t e d from 24-hour daily s a m p l e s t a k e n f r o m the f i r s t pond influent. The hydraulic and p h y s i c a l data
s c h e d u l e is given in appendix Table 26.
SECTION VI DISCUSSION
During Campaign Studies L i m e Addition and pH
The m a i n o p e r a t i n g p a r a m e t e r of the ponding s y s t e m w a s pH. The s y s t e m w a s o p e r a t e d in such a m a n n e r as to d e t e r m i n e t h e effects of s e l e c t e d pH l e v e l s on the s y s t e m and the effects of other influences such as w a t e r t e m p e r a t u r e on pH c o n t r o l . Calcined l i m e r o c k (CaO) was s l u r r i e d with hot w a t e r and differential amounts w e r e added to the influent to the f i r s t pond in o r d e r to a c h i e v e and m a i n t a i n v a r i o u s pH l e v e l s in the s y s t e m ( 5 ) .
Such pH c o n t r o l w a s d e s i g n e d to n e u t r a l i z e o r g a n i c a c i d s and inhibit b i o l o g i c a l a c t i v i t y . The s y s t e m w a s o p e r a t e d for the f i r s t 6 weeks at v a r i o u s pH l e v e l s . L i m e addition was the only v a r i a b l e d u r i n g t h i s i n t e r v a l . A f t e r t h i s p e r i o d , h e a t e d w a t e r was added t o t h e s y s t e m t o thaw frozen s u g a r b e e t s a s a n o p e r a t i o n a l n e c e s s i t y .
Other i n v e s t i g a t o r s have r e p o r t e d a c o r r e l a t i o n between pH c o n t r o l of a flume w a t e r s y s t e m and the amount of d i s s o l v e d oxygen in flume w a t e r (3 8). F r o m F i g u r e 5 it can be s e e n that pH and d i s s o l v e d oxygen did c o r r e l a t e well, and that high l e v e l s of d i s s o l v e d oxygen c o r r e s p o n d - ed to high (or r i s i n g ) pH l e v e l s . A l s o note that g r e a t e r pH l o s s e s w e r e e n c o u n t e r e d d u r i n g p e r i o d s when d i s s o l v e d oxygen did not c a r r y
t h r o u g h to the second pond.
At f i r s t glance it would a p p e a r that the amount of d i s s o l v e d oxygen in t h e s y s t e m w a s a function of the pH. That i s , high pH l e v e l s inhibited b i o l o g i c a l a c t i v i t y and r e d u c e d the consumption of oxygen. T h e r e f o r e , d i s s o l v e d oxygen c a r r i e d through the s y s t e m .
C o m p a r i s o n of F i g u r e 5 with F i g u r e 6 shows a negative c o r r e l a t i o n between t e m p e r a t u r e and d i s s o l v e d oxygen and a p o s i t i v e c o r r e l a t i o n b e t w e e n r e t u r n flow r a t e and d i s s o l v e d oxygen. I t i s , t h e r e f o r e , i m - p o s s i b l e to s e p a r a t e the individual effects (on pH control) of e a c h of t h e s e v a r i a b l e s .
During t h e p e r i o d s in which t h e amount of l i m e addition w a s t h e only influencing f a c t o r on pH, it was found that the c o n t r o l pH (SPE pH)
F I G U R E 5 . R E L A T I O N O F DISSOLVED OXYGEN T O p H A T T H R E E S A M P L I N G P O I N T S .
could be r a i s e d f r o m 7 to above 10 by the addition of f r o m 14, 000 to 16,000 pounds of l i m e p e r day ( F i g u r e 6). The pH could be m a i n - t a i n e d above 10 by the addition of f r o m 7, 200 to 9, 600 pounds of l i m e p e r day. E a r l y in campaign, t h e c o n t r o l pH was m a i n t a i n e d above 10 by the addition of as little as 6, 000 pounds of l i m e p e r day, but as t i m e p r o g r e s s e d m o r e l i m e was r e q u i r e d t o a c c o m p l i s h this feat p o s s i b l y i n - dicating the influence of i n c r e a s i n g o r g a n i c sludge a c c u m u l a t i o n s .
F r o m the l i m e addition study, i t would a p p e a r that l e s s t i m e i s r e - q u i r e d to m a i n t a i n pH l e v e l s above 10. 0 than to m a i n t a i n pH l e v e l s b e - low 1 0 . 0 . This conclusion c a m e f r o m the fact that the s y s t e m was n e v e r c o n s i d e r e d to be u n d e r pH c o n t r o l when the pH was below 10. T h i s is p r o b a b l y due to i n c r e a s e d b i o - a c t i v i t y when the pH was below 1 0 . 0 .
To further u n d e r s t a n d this phenomenon, an additional study was u n d e r - t a k e n . G r a b s a m p l e s w e r e taken f r o m the f i r s t pond influent, a n a l y z e d for alkalinity and pH and p l a c e d in the incubator @ 20°C + 1°C for a p e r i o d of 4 h o u r s . After t h i s 4 - h o u r p e r i o d the s a m p l e s w e r e once again a n a l y z e d for alkalinity and pH.
A t o t a l of 17 s a m p l e s w e r e e x a m i n e d in t h i s study w h e r e t h e o r i g i n a l pH r a n g e d f r o m 9.0 to 12. 0. T h e study c o v e r e d 30 days of f a c t o r y o p e r a - t i o n and one s a m p l e p e r day was analyzed f r o m 3 to 5 t i m e s a week. T h e r e s u l t s of t h i s study a r e s u m m a r i z e d in T a b l e 1. F o r p u r p o s e s of t a b u l a - tion, Table 1 s a m p l e s w e r e c a t e g o r i z e d a c c o r d i n g to o r i g i n a l pH r a n g e . T h e r e s u l t s of t h i s study show that m i n i m a l reductions in a l k a l i n i t y o c c u r r e d when o r i g i n a l pH was above 1 0 . 0 .
TABLE 1. -- pH AND ALKALINITY STUDY F P I GRAB S A M P L E S , 1968-69 CAMPAIGN. *
* s a m p l e s a n a l y z e d , held at 20°C for 4 h o u r s , s a m p l e s r e - a n a l y z e d .
T o f u r t h e r s u b s t a n t i a t e t h e s e data Table 2 was developed. Grab s a m p l e s f r o m t h e f i r s t pond influent, second pond influent and second pond efflu- e n t w e r e a n a l y z e d for pH t h r e e t i m e s a day for the e n t i r e 1968-69
c a m p a i g n . T h e weekly or median pH from the 15 s a m p l e s per week f r o m t h e t h r e e s a m p l i n g points w e r e c a t e g o r i z e d b y F P I p H r a n g e .
F I G U R E 6. THE RELATION OF LIME ADDITION TO pH AT THE
SECOND POND E F F L U E N T . THE P E R C E N T UNTREATED RETURN FLOW IS SHOWN.
T h e p H d r o p a c r o s s the ponds i n c r e a s e d a s the F P I p H d e c r e a s e d f r o m pH 12.0 to 1 0 . 0 . T h e l a r g e s t pH r e d u c t i o n s w e r e e x p e r i e n c e d when the F P I pH r a n g e d f r o m 8.0 to 10. 0. When the F P I pH was f r o m 7. 0 to 8.0, it d r o p p e d at a s l o w e r r a t e and s t a b i l i z e d at the 6 . 5 - 7 . 0 l e v e l .
T A B L E 2. - - M E D I A N pH, F P I , S P E WEEKLY AVERAGE OF GRAB S A M P L E S T H R E E TIMES P E R DAY.
A s n o t e d e a r l i e r , p H l o s s e s i n the s y s t e m w e r e much g r e a t e r i n m a g - n i t u d e a n d o c c u r r e d f a s t e r when h e a t e d flume w a t e r was being u s e d , r e -
sulting i n h i g h e r pond t e m p e r a t u r e s . I n m o s t c a s e s , r i s i n g pond t e m p e r - a t u r e s r e s u l t e d i n d e c r e a s i n g p H l e v e l s .
H i g h e r l i m e addition ( F i g u r e 6, week 15) did not c o m p e n s a t e for the i n - fluence of h e a t e d w a t e r on the r a t e of pH reduction.
R e f e r e n c e w a s m a d e to a design d e c i s i o n providing for a p o r t i o n of the w a t e r t o r e t u r n f r o m t h e s c r e e n s t o t h e flumes without t r e a t m e n t . T h e p e r c e n t a g e of t h e t o t a l flow r e t u r n e d to the flumes without l i m e addition a l s o c o r r e l a t e s with pond pH ( F i g u r e 6). When the pond pH was below
1 0 . 0 , t h e p e r c e n t a g e of u n t r e a t e d r e t u r n was l e s s than 40 p e r c e n t . When t h e pond pH w a s above 10. 0, the r e t u r n p e r c e n t a g e was g r e a t e r t h a n 40 p e r c e n t . T h e r a t i o o f l i m e addition t o w a t e r was l a r g e r u n d e r t h e s e c o n - ditions .
Although a t t e m p t e d , it was not p o s s i b l e from this study to s e p a r a t e the effects of t e m p e r a t u r e and r e t u r n flow p e r c e n t a g e on pond pH. In gen- e r a l , high t e m p e r a t u r e s and low r e t u r n flow r a t e s s e e m t o b e a n t a g o - n i s t i c to high pH c o n t r o l . L i m e addition is m o s t effective when r e t u r n flow is above t h e 40 p e r c e n t level and the flume w a t e r is not being h e a t e d .
Solids Removal
The suspended and settleable solids that w e r e i n t r o d u c e d into the fluming and washing operations consisted of mud, sand, and beet f r a g m e n t s . Some of the heavier solids w e r e r e m o v e d by the r o c k d r a g , which o p e r - ates in the beet flume. The DSM s c r e e n s r e m o v e d an e s t i m a t e d 3 0 to 50 tons/day of wet m a t e r i a l ( F i g u r e 7). T h e r e f o r e , a l a r g e p e r c e n t a g e of the total suspended solids was r e m o v e d b e f o r e l i m i n g and b e f o r e the water entered the f i r s t settling pond. H o w e v e r , the w a t e r e n t e r i n g the first settling pond, during the 1968-69 c a m p a i g n , contained an a v e r a g e 56. 6 tons of suspended solids p e r day and the effluent f r o m t h i s pond c o n - tained an average of 8.7 tons of suspended s o l i d s p e r d a y . T h u s 4 7 . 9 tons of suspended solids s e t t l e d in the f i r s t pond each day for an a v e r a g e 84.6 p e r c e n t r e m o v a l . By s e d i m e n t a t i o n t e s t s it was d e t e r m i n e d t h a t 94.8 p e r c e n t of the s e t t l e a b l e solids w e r e r e m o v e d . The fine s o l i d s which did not settle r e a d i l y continued to i n c r e a s e in t h e r e c y c l e d w a t e r s . Calculations based on s e t t l e a b l e solids a n a l y s e s showed that t h e a v e r a g e mud deposition r a t e in t h e f i r s t pond was about 52, 000 gallons (277 y d3) p e r day. Since the Longmont f a c t o r y s l i c e d an a v e r a g e of 3, 307 t o n s of beets p e r day, 15. 7 gallons of f i r s t pond c a p a c i t y was used for e v e r y t o n of beets s l i c e d . Actual e x p e r i e n c e during the 1968-69 c a m p a i g n , i n - volving the amount of t i m e that was r e q u i r e d to fill a f i r s t s e t t l i n g p o n d , indicated that t h i s figure i s v e r y n e a r l y c o r r e c t .
B a s e d on the absolute density (Table 3) of the mud, the t o t a l weight of the mud deposited and the t o t a l volume of the mud deposited, t h e a v e r a g e p e r c e n t m o i s t u r e of the deposited m a s s was 8 0 . 7 p e r c e n t by w e i g h t . T h i s wet mud p r o v e d difficult to handle d u r i n g c a m p a i g n cleaning o p e r a - tions of the first ponds.
This s e t t l e d mud was r e m o v e d e v e r y t h r e e to four weeks during c a m p a i g n dependent upon the quantity of mud washed f r o m " c l e a n or muddy b e e t s . "
Only about 85 p e r c e n t of the mud could be r e m o v e d from the ponds by c l a m s h e l l due to the high w a t e r content of the m u d . After the end of c a m p a i g n , 100 p e r c e n t mud r e m o v a l could be a c c o m p l i s h e d .
I r r e g a r d l e s s of the t i m e of y e a r when mud was r e m o v e d , it was u s e d as landfill in low a r e a s on the factory p r e m i s e s . This was n e c e s s a r y due to the odors emanating f r o m the mud. A l e s s e r odor p r o b l e m w a s e n c o u n t e r e d from the mud r e m o v e d f r o m ponds after c a m p a i g n .
T h e m o i s t u r e in the mud amounted to a p p r o x i m a t e l y 48, 000 gallons of w a t e r p e r d a y . T h i s w a t e r was lost t o the fluming and ponding s y s t e m and a m o u n t e d to 1.4 p e r c e n t of the t o t a l pond v o l u m e p e r d a y . T h e w a t e r l o s s w a s , a p p a r e n t l y , offset by an inherent i n c r e a s e in s y s t e m w a t e r s .
It was n o t e d that t h e f i r s t pond would m a i n t a i n a good s e t t l i n g efficiency until it was a l m o s t full, at which t i m e s e t t l e a b l e solids would begin to c a r r y o v e r into t h e second pond. T h e m i n i m u m r e t e n t i o n t i m e i n the f i r s t pond t o a c h i e v e r e a s o n a b l e s e t t l i n g was d e t e r m i n e d t o t a k e between 20 to 30 m i n u t e s .
To f u r t h e r c h a r a c t e r i z e the s e t t l e a b l e solids in the first pond, t h e s e t t l e d m u d in one l i t e r of the 2 4 - h o u r c o m p o s i t e s a m p l e f r o m t h e f i r s t pond influent w a s r e m o v e d daily and c o m p o s i t e d into weekly s a m p l e s . T h e s e s a m p l e s w e r e t h e n a n a l y z e d (Table 3 ) . The d r y m u d contained an a v e r a g e of 3. 25 p e r c e n t c a r b o n (the a v e r a g e pH of t h e diluted s a m p l e
FIGURE 7. TRASH AND SOLIDS REMOVED BY SCREENING.
TABLE 3. --WEEKLY MUD COMPOSITES, 1968-69 CAMPAIGN AVERAGE.
*Relative density based on maximum compacted volume.
**The calculated zero m o i s t u r e density.
was 8. 6). The carbon probably served as a s u b s t r a t e for b a c t e r i a and thispH probably did not seriously inhibit bacteriological activity. T h u s it is easy to understand why the wet mud produced foul odors when it w a s being removed from the first ponds.
The a v e r a g e amount of lime addition was 10,440 pounds p e r day. T h e amount of total CaO in the dry settled mud averaged 6, 220 pounds p e r day. This means that as much as 59. 6 percent of the l i m e added to the s y s t e m was lost immediately in the first pond.
The f i r s t pond was designed for p r i m a r y settling of the heavy, m o r e r e a d i l y settled solids. The second pond was designed to allow m o r e settling t i m e and a milder environment to remove the s m a l l e r , m o r e difficult to settle solids. The average amount of solids entering the second pond was 8. 7 tons p e r day. However, the amount of solids leaving the second pond and returning to the fluming o p e r a t i o n s a v e r - aged 9.4 tons p e r day. This indicated that m o r e insoluble solids w e r e
f o r m e d a n d r e m a i n e d s u s p e n d e d , t h a n w e r e s e t t l e d i n t h e second pond.
T h e f o r m a t i o n of insoluble solids could be accounted for in s e v e r a l w a y s : s a m p l i n g a n a l y s i s ; p r e c i p i t a t i o n o f insoluble e l e m e n t s ; f o r m a - t i o n of b i o l o g i c a l sludge; and s t i r r i n g of the s e t t l e d sludge by gas e v o l u t i o n f r o m t h i s s l u d g e . The d a t a would indicate that t h e second s e t t l i n g pond was not p e r f o r m i n g as expected and could have been e x - c l u d e d f r o m the s y s t e m , except for i t s r o l e as a s u r g e b a s i n .
T h e r e w a s e v i d e n c e of a n a e r o b i c b i o l o g i c a l activity in the f i r s t pond as t h e a v e r a g e amount of o r g a n i c a c i d s i n c r e a s e d by m o r e than 3,000 pounds p e r day in the pond. T h i s a c i d p r o d u c t i o n is m e r e l y a change in s u b s t r a t e f o r m a n d m a y not c a u s e a l o s s of oxygen d e m a n d (22), ( T a b l e 4 ) .
T A B L E 4. - - C H A N G E P E R DAY ACROSS FIRST AND SECOND PONDS, 1968-69 CAMPAIGN A V E R A G E .
* M i n u s s i g n i n d i c a t e s l o s s , and p l u s sign i n d i c a t e s gain.
An a v e r a g e of only 40 pounds p e r day of soluble CaO was lost in the f i r s t pond but t h e a v e r a g e amount of t o t a l CaO (soluble and insoluble) w a s r e d u c e d b y m o r e t h a n 3 , 000 pounds p e r d a y . T h i s i n d i c a t e d t h a t the r e d u c t i o n of CaO in the f i r s t pond was due m a i n l y to the s e t t l i n g of i n s o l u b l e C a O .
The second pond, which had a r e t e n t i o n t i m e of a p p r o x i m a t e l y 12 h o u r s , reduced the BOD5 at a rate a v e r a g i n g g r e a t e r than 6, 000 pounds p e r day. The soluble CaO in the s e c o n d pond dropped an a v e r a g e of a l m o s t
1, 100 pounds per day but the t o t a l CaO was reduced by only 160 pounds p e r day. This would indicate t h a t much of the soluble CaO f o r m e d i n - soluble calcium compounds and is probably the s o u r c e for about 65 p e r - cent of the i n c r e a s e in suspended solids upon p a s s a g e through the
second pond.
The formation of insoluble c a l c i u m salts might a l s o indicate that s o m e of the BOD5 reduction in this pond is accomplished by the f o r m a t i o n of insoluble calcium-organic a c i d compounds, as the o r g a n i c acid and t o t a l carbon levels also showed a reduction in this pond. H o w e v e r , bubbling in the pond indicated s o m e complete biodegradation, i . e . c a r - bon s u b s t r a t e organic a c i d s methane + C O2.
Dissolved Solids, COD, BOD in Recirculated Water
The data used in F i g u r e s 8 t h r o u g h 10 come from a n a l y s i s of t h e s e c o n d pond effluent (SPE). This point in the s y s t e m was chosen as the c o n t r o l point.
The concentration of d i s s o l v e d solids (Figure 8) in the S P E s t e a d i l y i n - c r e a s e d as campaign p r o g r e s s e d until it r e a c h e d a peak of about 10, 500 ppm during the 14th week. A n o t h e r investigation (5) of r e c i r c u l a t e d flume water in the sugarbeet i n d u s t r y has r e p o r t e d a tendency for the dissolved solids concentration to plateau or level off with continued r e - circulation. The Longmont s y s t e m showed no positive t r e n d t o w a r d leveling off during the 1968-69 campaign.
As F i g u r e 8 indicates, t h e r e w a s a tendency for suspended solids to i n - c r e a s e in the SPE as campaign p r o g r e s s e s . T h e s e suspended s o l i d s which c a r r y through the s y s t e m a r e very s m a l l . F o r the m o s t p a r t , the quality of the second pond effluent was good f r o m the suspended s o l i d s standpoint as values stayed u n d e r the 500 ppm level for the f i r s t 12 w e e k s .
The biochemical oxygen d e m a n d , chemical oxygen demand and t o t a l o r - ganic carbon (TOC) c o n c e n t r a t i o n s steadily i n c r e a s e d until t h e 13th week of operation (Figure 9). H e r e again the d e c r e a s e in c o n c e n t r a t i o n s during the 12th week of o p e r a t i o n was explained by pond dilution. After the 13th week, the COD, BOD5 and TOC d e c r e a s e d indicating a high l e v e l of biological activity d u r i n g this p e r i o d .
T o t a l s u g a r c o n c e n t r a t i o n in the pond w a t e r was dependent on the pH of the w a t e r ( F i g u r e 10 ). When the c o n t r o l pH was m a i n t a i n e d at a f a i r - ly high l e v e l t h e c o n c e n t r a t i o n of s u g a r i n c r e a s e d , but when the c o n t r o l pH was low the s u g a r n e a r l y d i s a p p e a r e d r e s u l t i n g in an i n c r e a s e in o r g a n i c a c i d s . It is noteworthy t h a t , during the 10th w e e k of o p e r a t i o n when the c o n t r o l pH fell below 8 . 0 , t h e t o t a l s u g a r s l o s s was only 1, 400 ppm, but the o r g a n i c acid c o n c e n t r a t i o n i n c r e a s e d by 3, 800 p p m . O p e r a t i o n d u r i n g t h i s week involved adding h e a t e d flume w a t e r continu- ously, and adding 1, 000 pounds of l i m e p e r hour to the s y s t e m .
The r e l a t i o n s h i p between c o n t r o l pH, t o t a l s u g a r s and o r g a n i c a c i d c o n - c e n t r a t i o n s p r e s e n t s s t r o n g evidence that high pH levels inhibit b i o l o g i c a l FIGURE 8. S P E INCREASE IN CONCENTRATION OF DISSOLVED
AND SUSPENDED SOLIDS DURING CAMPAIGN.
activity and fermentation.
The soluble CaO concentrations i n c r e a s e d from 240 ppm to m o r e than 2, 600 ppm by the 14th week of o p e r a t i o n , and the total acid c o n c e n t r a - tion (calculated as CaO) rose f r o m a b o u t 400 ppm to above 3, 400 p p m by the 14th week of operation. T h i s i n d i c a t e s that the g r e a t e r p e r c e n t ¬ age of the soluble cations in the s y s t e m was c a l c i u m .
1967-68 campaign studies (38) i n d i c a t e d that m o r e than 80 p e r c e n t of the phosphate entering the ponds w a s r e m o v e d . It is t h e o r i z e d that . phosphate is readily fixed by the s o i l p a r t i c l e s and r e m o v e d by
settling. Under high pH and c a l c i u m c o n c e n t r a t i o n s , phosphate b e - comes insoluble and eventually s e t t l e s out.
FIGURE 9. SPE INCREASE IN T O C , B O D5 AND COD DURING CAMPAIGN.
FIGURE 10. S P E RELATIONSHIPS B E T W E E N TOTAL SUGARS, ORGANIC ACIDS AND pH DURING CAMPAIGN.
The a v e r a g e c o n c e n t r a t i o n of t o t a l o r t h o p h o s p h a t e in t h e s e c o n d pond during the 1968-69 c a m p a i g n was 4. 2 p p m . However, as only a t r a c e of phosphate is n e c e s s a r y to s u p p o r t an a c t i v e b i o l o g i c a l population, t h e r e was p r o b a b l y enough a v a i l a b l e p h o s p h a t e i n the s y s t e m t o s u p p o r t biological a c t i v i t y .
Ammonia s e e m e d to be the p r e v a l e n t f o r m of n i t r o g e n as can be s e e n f r o m T a b l e 5. Of the t o t a l n i t r o g e n , 81 p e r c e n t was a m m o n i a n i t r o g e n . A m m o n i a n i t r o g e n i n c r e a s e d until t h e 11th week of c a m p a i g n r e a c h i n g a peak of 49ppm after which it s t e a d i l y d e c r e a s e d . N i t r a t e a n d n i t r i t e nitrogen c o n c e n t r a t i o n s s t a r t e d above 7 . 5 ppm and s t e a d i l y d e c r e a s e d until the 14th week when the c o n c e n t r a t i o n l e v e l s of t h e s e e l e m e n t s w e r e l e s s than 0 . 5 ppm, w h e r e t h e y s t a y e d for t h e r e m a i n d e r of t h e c a m p a i g n .
TABLE 5.--NITROGEN, SULFUR, AND PHOSPHOROUS CONCENTRA- TIONS, 1968-69 CAMPAIGN.*
Sulfate was the p r e d o m i n a n t sulfur compound in the r e c i r c u l a t e d flume w a t e r . However, a n a e r o b i c and faculative b a c t e r i a s y s t e m s can r e d u c e sulfate to the odor producing sulfide s t a t e (22). Note t h a t the sulfide concentration was as high as 2.0 p p m , but the a v e r a g e c o n c e n t r a t i o n of sulfides was only 0. 1 p p m . Odor f r o m the r e c i r c u l a t i n g f l u m e w a t e r was noticeable at t i m e s but was n e v e r a p r o b l e m during the 1968-69 campaign.
Anaerobic Pond
During the 1967-68 c a m p a i g n the a n a e r o b i c pond was scheduled to r e c e i v e a 100 gpm flow from the second settling pond and to d i s c h a r g e a flow equal to the influent m i n u s the amount lost to seepage and e v a p o r a t i o n . The anaerobic pond was empty at the beginning of the 1967-68 c a m p a i g n , and during the early p a r t of the s e a s o n r e c e i v e d the p r e s c r i b e d 100 gpm
*Combined r e s u l t s on b o t h SPI and S P E .
influent. However, the d e c i s i o n w a s r e a c h e d to fill t h e a n a e r o b i c pond rapidly in o r d e r to provide a supply of o x y g e n - d e m a n d i n g w a s t e with which t o i n i t i a t e a n a e r o b i c a c t i v i t y . T h e c o n t r o l b y - p a s s v a l v e was opened to fill the pond r a p i d l y , t h u s e l i m i n a t i n g an o p p o r t u n i t y to a c c u r a t e l y m e a s u r e the influent flow.
Following filling, evidence of expected b i o - d e g r a d a t i o n was a b s e n t . About 2, 000 gallons of d o m e s t i c s e w a g e s e c o n d a r y sludge w e r e a d d e d t o the a n a e r o b i c pond a s i n o c u l u m t o i n c r e a s e t h e d i g e s t i o n r a t e . T h e r e s u l t s w e r e quite n e g a t i v e ; no a c t i v i t y was noted until the end of the c a m p a i g n .
Two five h o r s e p o w e r s u r f a c e a e r a t o r s ( A q u a - L a t o r F L T M - 5 - 4 , Wells P r o d u c t C o r p o r a t i o n ) with c o m p l e t e a n t i - e r o s i o n a s s e m b l i e s w e r e u s e d i n the a n a e r o b i c pond. The p u r p o s e of t h e a e r a t o r s was to s p r e a d a l a y e r of oxygenated w a t e r a c r o s s the s u r f a c e of t h e pond in o r d e r to oxidize evolving sulfides and o t h e r e l e m e n t s of t h e a n a e r o b i c d i g e s t i o n p r o c e s s , thus reducing o d o r s . Any r e d u c t i o n in oxygen d e m a n d a c c o m p l i s h e d by t h e s e a e r a t o r s was expected to be a fringe benefit as the pond was not d e - signed to be an a e r o b i c f a c i l i t y .
During both c a m p a i g n s the a e r a t o r s w o r k e d r e a s o n a b l y w e l l . O d o r s from the pond w e r e not e x c e s s i v e except during a p e r i o d of high sulfide l i b e r a t i o n . T h i s p e r i o d l a s t e d about 3 m o n t h s . N e a r - z e r o w e a t h e r did not h a m p e r a e r a t o r o p e r a t i o n even though m o s t of the pond s u r f a c e was i c e - c o v e r e d .
Some foam a c c u m u l a t e d on t h e a n a e r o b i c pond f r o m t i m e to t i m e , and mounds of frozen foam piled a r o u n d t h e a e r a t o r s d u r i n g t h e p e r i o d s of z e r o and s u b - z e r o t e m p e r a t u r e s . A l a r g e b u i l d - u p of f o a m w a s noted at the P a r s h a l l flume d u r i n g t h e 1967-68 p e r i o d s of d i s c h a r g e .
Table 6 shows the r a n g e and m e a n of the a n a l y s i s of the a n a e r o b i c pond effluent during the 1967-68 c a m p a i g n . T h e r e s u l t s of t h e a n a e r o b i c
pond e x p e r i e n c e s during the 1967-68 c a m p a i g n s u g g e s t e d that the o r i g i n a l concept of an a n a e r o b i c pond as a c a m p a i g n t r e a t m e n t f a c i l i t y would
need r e - e v a l u a t i o n p r i o r to the next p e r i o d of o p e r a t i o n . As a r e s u l t , the following d e c i s i o n s w e r e m a d e :
1. To e l i m i n a t e the a n a e r o b i c pond effluent during c a m p a i g n s so as to hold a l l of the flume w a t e r in the pond s y s t e m u n t i l such a t i m e as t h i s w a t e r was sufficiently d e g r a d e d and a c c e p t a b l e for d i s c h a r g e t o the r i v e r ;
2 . T o u t i l i z e t h e a n a e r o b i c pond a s a holding b a s i n w h i c h w o u l d r e c e i v e a n y e x c e s s w a t e r w h i c h m i g h t b u i l d - u p i n t h e s e t t l i n g pond s y s t e m ;
3 . T o u t i l i z e t h e w a t e r r e s i d i n g i n t h e a n a e r o b i c p o n d a s a s o u r c e o f m a k e - u p t o t h e fluming a n d s e t t l i n g s y s t e m s w h e n e v e r n e e d e d . T h e d a t a w i l l show t h a t t h e 1967-68 p o s t c a m p a i g n w a t e r h a d b e e n s u c c e s s - fully t r e a t e d t o m e e t d i s c h a r g e s t a n d a r d s . P r i o r t o t h e b e g i n n i n g o f t h e
1 9 6 8 - 6 9 c a m p a i g n t h e a n a e r o b i c pond l e v e l w a s l o w e r e d t o a w a t e r d e p t h o f 8 f e e t . A t t h i s l e v e l t h e pond functioned a s a r e s e r v o i r t o r e c e i v e e x - c e s s f l u m e w a t e r with enough c a p a c i t y t o h o l d a l l o f t h e e x p e c t e d e x c e s s w a t e r . A d d i t i o n a l l y , a c a r r y - o v e r o f a c t i v e s e e d a n d s l u d g e w a s d e s i r - a b l e .
T A B L E 6 . - - A N A E R O B I C POND E F F L U E N T , 1 9 6 7 - 6 8 C A M P A I G N
The a n a e r o b i c pond during t h e 1968-69 o p e r a t i n g s e a s o n s u c c e s s i v e l y s e r v e d as a s u r g e r e s e r v o i r for e x c e s s s e c o n d pond w a t e r and as a s o u r c e of m a k e - u p w a t e r to the fluming s y s t e m . No s e r i o u s p r o b l e m s w e r e e n c o u n t e r e d . The flow p a t t e r n p e r m i t t e d an o c c a s i o n a l feeding of organic m a t t e r into the a n a e r o b i c pond. This was a c c o m p l i s h e d by drawing w a t e r f r o m the a n a e r o b i c pond into the f l u m e s , which would eventually c a u s e the second settling pond to d i s c h a r g e into t h e a n a e r o b i c pond. This r e c i r c u l a t i o n p r o c e d u r e was employed s e v e r a l t i m e s i n o r d e r to i n c r e a s e t h e l e v e l of oxygen demanding s u b s t a n c e s in t h e a n a e r o b i c pond for the p u r p o s e of maintaining continuing b i o a c t i v i t y .
A s the 1968-69 campaign p r o g r e s s e d the a n a e r o b i c pond t e m p e r a t u r e steadily d e c r e a s e d . During the ninth week t h i s t e m p e r a t u r e d r o p p e d below 4°C and r e m a i n e d below for t h e r e s t of the c a m p a i g n . T h e low pond t e m p e r a t u r e (mean 6°C) p r o b a b l y inhibited b i o l o g i c a l a c t i v i t y as little r e d u c t i o n in o r g a n i c s was m e a s u r e d during the 1968-69 c a m p a i g n (Table 7).
The pH of the a n a e r o b i c pond v a r i e d only s l i g h t l y . It was h i g h e s t b e f o r e any load had b e e n added. When loaded t h e pH fell to about 7. 0 - 7 . 5 and changed only slightly after that (Table 9).
The t o t a l s u g a r s w e r e m o s t l y d e g r a d a t e d t o o r g a n i c a c i d s b y t h e t i m e the w a t e r r e a c h e d the a n a e r o b i c pond. A s m a l l c o n c e n t r a t i o n of s u g a r p e r s i s t e d , but i t i s believed that t h e s e a r e c a r b o h y d r a t e f o r m s that a r e difficult to d e g r a d e .
Some of the finer suspended solids c a r r i e d t h r o u g h to t h e a n a e r o b i c pond. T h e o r e t i c a l l y , t h i s is good s i n c e t h e fine p a r t i c l e s m a y p r o v i d e an inert nucleus for growth of b i o l o g i c a l flocs (36). Sulfides w e r e p r o - duced in the pond f r o m t i m e to t i m e , but t h e a v e r a g e c o n c e n t r a t i o n was only 0 . 2 p p m . T h e a l m o s t n e g l i g i b l e odor was a l s o evidence of low sulfide p r o d u c t i o n .
TABLE 7. --ORGANIC DEGRADATION IN ANAEROBIC POND, 1968-69 CAMPAIGN.
T A B L E 8.--ANAEROBIC POND DURING CAMPAIGN, 1968-69 CAMPAIGN AVERAGE.
When the fluming o p e r a t i o n s c e a s e d , t h e w a t e r in the f i r s t and s e c o n d ponds was d i s c h a r g e d to the a n a e r o b i c p o n d for b i o d e g r a d a t i o n a f t e r both the 1967-68 and 1968-69 c a m p a i g n s . T h e r e s u l t s f r o m t h e s e two y e a r s have not been combined, but w e r e s i m i l a r . T h e d a t a f r o m 1968- 6 9 a r e r e p o r t e d below i n d e t a i l w i t h o c c a s i o n a l r e f e r e n c e t o 1967-68 t r e a t m e n t .
After the end of beet fluming in J a n u a r y 1969, the f i r s t a n d s e c o n d settling pond w a t e r w a s r e c i r c u l a t e d t h r o u g h a n e v a p o r a t o r - c o n d e n s e r (CSF) for one week p r i o r t o i t s d i s c h a r g e into t h e a n a e r o b i c p o n d . This was done to i n c r e a s e t h e t e m p e r a t u r e of t h e fluming w a t e r b e f o r e its d i s c h a r g e into t h e cold e n v i r o n m e n t of t h e a n a e r o b i c pond so as to i n c r e a s e the b i o a c t i v i t y i n t h e f l u m i n g w a t e r a n d thus a c c e l e r a t e the r a t e of d e g r a d a t i o n . The s e t t l i n g pond t e m p e r a t u r e d u r i n g t h i s p e r i o d of r e c i r c u l a t i o n was m a i n t a i n e d at about 3 0 ° C . After the h e a t i n g and r e c i r c u l a t i o n p e r i o d t h e f i r s t and s e c o n d s e t t l i n g pond w a t e r w a s p u m p e d
c e i v e a l l of the w a t e r f r o m the s e t t l i n g s y s t e m so t h e r e was no r e s u l t i n g d i s c h a r g e .
The w a t e r r e m a i n e d in the a n a e r o b i c pond until m i d - S e p t e m b e r , 1969.
At that t i m e t h e biological s t a b i l i z a t i o n of the o r g a n i c s w a s n e a r l y c o m p l e t e and pond contents w e r e s u b s e q u e n t l y u s e d to fill t h e flumes for the 1969-70 c a m p a i g n .
The two 5-hp a e r a t o r s r a n continuously (except for s h o r t p e r i o d s of m e c h a n i c a l f a i l u r e and planned e x p e r i m e n t a l shut-downs) until t h e l a s t week of July, when a high c o n c e n t r a t i o n of a l g a e was n o t e d . The a e r a t o r s r e m a i n e d off until t h e l a s t week in August, at which t i m e m e c h a n i c a l a e r a t i o n was r e s u m e d .
P h o s p h a t e was added t o t h e pond s i x t i m e s during the p o s t - c a m p a i g n p e r i o d t o a c c e l e r a t e biological a c t i v i t y since t h e p h o s p h a t e a n a l y s i s i n - dicated a deficiency for o p t i m u m a c t i v i t y . The f i r s t two a d d i t i o n s of phosphate w e r e in the f o r m of t r i p l e s u p e r p h o s p h a t e , a g r a n u l a r c o m - m e r c i a l f e r t i l i z e r containing 4 6 p e r c e n t P2O5. However, t h e g r a n u l a r m a t e r i a l d i s s o l v e d slowly and a l l subsequent additions w e r e in the f o r m of a m m o n i u m phosphate, a liquid c o m m e r c i a l f e r t i l i z e r with a 10 p e r - cent a m m o n i a n i t r o g e n and 3 4 p e r c e n t P2O5 a n a l y s i s . T h e liquid addition proved to be s a t i s f a c t o r y ; adequate l e v e l s of soluble o r t h o phosphate w e r e a c h i e v e d .
After the c a m p a i g n of 1968-69, the a n a e r o b i c pond was s a m p l e d in the s a m e m a n n e r a s during the 1967-68 p o s t - c a m p a i g n p e r i o d , except that the s a m p l e s w e r e c o m p o s i t e d b y d e p t h i n a n a t t e m p t t o e x p l o r e t h e p o s - sibility of s t r a t i f i c a t i o n . This s a m p l i n g p r o c e d u r e was continued for the f i r s t 8 weeks of the p o s t - c a m p a i g n p e r i o d . F r o m t h e data it was d e t e r m i n e d t h a t s t r a t i f i c a t i o n did not e x i s t in t h e pond a n d t h a t e x t e n s i v e sampling was not n e c e s s a r y for depth d i f f e r e n c e s . T a b l e 30 in the
appendix shows the a n a l y t i c a l s c h e d u l e which was conducted on the a n a e r o b i c pond s a m p l e s for the f i r s t 8 weeks of t h e p o s t - c a m p a i g n p e r i - od ( F e b r u a r y 3 to M a r c h 28, 1969).
Beginning with t h e 9th week of t h e p o s t - c a m p a i g n p e r i o d , t h e a n a e r o b i c pond was s a m p l e d a s d e s c r i b e d a b o v e . However, a l l s a m p l e s w e r e c o m p o s i t e d . Table 31 in the appendix shows the a n a l y t i c a l s c h e d u l e p e r f o r m e d until July 9, 1969, and T a b l e 32 shows t h e a n a l y t i c a l
schedule continued t h e r e a f t e r .
On F e b r u a r y 5, 1969, the a n a e r o b i c pond was at a depth of 1 1 ' 4" and contained m o r e than 145,000 pounds of BOD5. Under conditions of high
