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Role of saturated and unsaturated zones in soil disposal of septic tank effluent Johnson, Kenneth Robert 1986

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ROLE OF SATURATED AND UNSATURATED ZONES IN SOIL DISPOSAL OF SEPTIC TANK EFFLUENT by KENNETH ROBERT JOHNSON B . A . S c , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n FACULTY OF GRADUATE STUDIES Department of C i v i l E n g i n e e r i n g We a c c e p t t h i s t h e s i s as con f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA October, 1986 © Ken Johnson, 1986 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l l m e n t of the requirements f o r an advanced degree a t the UNIVERSITY OF BRITISH COLUMBIA, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be gr a n t e d by the Head of my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of C i v i l E n g i n e e r i n g THE UNIVERSITY OF BRITISH COLUMBIA 2075 Wesbrook P l a c e Vancouver, B r i t i s h Columbia Canada V6T 1W5 Date:October.1986 ABSTRACT The g u i d e l i n e s i n B r i t i s h Columbia f o r the use of the s e p t i c t a n k - s o i l a b s o r p t i o n system (ST-SAS) a r e v e r y s p e c i f i c i n r e g a r d to the s e p a r a t i o n d i s t a n c e s between the ground s u r f a c e and the groundwater t a b l e (minimum 1.2 m e t r e s ) , and between the t i l e f i e l d and p e r i m e t e r d r a i n s or d i t c h e s (minimum 3.0 m e t r e s ) . A p i l o t s c a l e experiment u t i l i z i n g s i m u l a t e d s e c t i o n s of a s e p t i c t i l e f i e l d , w i t h zones of s a t u r a t e d and u n s a t u r a t e d s o i l , was used t o e v a l u a t e the s c i e n t i f i c b a s i s f o r t h e s e g u i d e l i n e s . S e p t i c tank e f f l u e n t was a p p l i e d t o depths of u n s a t u r a t e d s o i l , which v a r i e d from 0.91 metres (3 f e e t ) t o 0.00 metres, a t the i n l e t end of a s a t u r a t e d zone. Samples were t a k e n a t d i s t a n c e s of 0.61 metres (2 f e e t ) , 1.67 metres (5.5 f e e t ) , and 2.74 metres (9 f e e t ) i n the s a t u r a t e d zone. Measurements were made of t o t a l and f e c a l c o n f o r m s , c h e m i c a l oxygen demand, ammonia, n i t r a t e and orthophosphate. Continuous o p e r a t i o n of the s e c t i o n s produced e f f l u e n t w i t h t o t a l c o l i f o r m s g e n e r a l l y l e s s than 400 c o l i f o r m s / 1 0 0 mL, and f e c a l c o l i f o r m s g e n e r a l l y l e s s t h a n 200 c o l i f o r m s / 1 0 0 mL. V a r y i n g degrees of n i t r i f i c a t i o n o c c u r r e d i n the u n s a t u r a t e d zones r e s u l t i n g i n r e l a t i v e l y h i g h c o n c e n t r a t i o n s of n i t r a t e i n some of the s e c t i o n s . The removal of o r t h o p h o s p h a t e was g r e a t e r than 90 p e r c e n t i n a l l of the s e c t i o n s , a n d the removal of n i t r o g e n v a r i e d from 25 t o 90 p e r c e n t . i i Reductions i n measured i n f l u e n t parameters were s u b s t a n t i a l i n a l l of the s e c t i o n s . T h i s s u p p o r t s the 1.2 metre s e p a r a t i o n d i s t a n c e i n the g u i d e l i n e s , and s u g g e s t s t h a t 3.0 metre h o r i z o n t a l s e p a r a t i o n may be c o n s e r v a t i v e i n some c a s e s . Of conc e r n were the h i g h n i t r a t e v a l u e s observed i n some of the s e c t i o n s , which may r e q u i r e c o n s i d e r a t i o n of n i t r i f i c a t i o n p o t e n t i a l i n some s o i l s . i i i TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGEMENT ix 1. INTRODUCTION 1 1.1 On-site Waste Treatment 1 1.2 Rationale for Experiment 2 1.3 Literature Review 5 1.3.1 On-site Waste Treatment Problems 5 1.3.2 Changes In Technology 7 1.3.3 Importance of Unsaturated Zone 9 1.3.4 Recognition of Saturated Zone 10 1.3.5 Reduction of Coliforms 11 1.3.6 Reduction of Biodegradeable Material 11 1.3.7 Changes in Nitrogen 12 1.3.8 Reactions of Phosphorus 13 1.4 Method of Experimental Investigation 13 1.4.1 Objectives 13 1.4.2 Experimental Setup 16 1.4.3 Experimental Procedures 19 2. MATERIALS AND METHODS 21 2.1 Unit Construction 21 2.2 S o i l and S o i l Placement 22 2.3 Groundwater and Septic Tank Feed 24 iv 2.4 Sample C o l l e c t i o n , Storage and A n a l y s i s 29 3. RESULTS 32 3.1 O v e r a l l E x p e r i m e n t a l Summary 32 3.2 C o l i f o r m s 33 3.3 Chemical Oxygen Demand 41 3.4 N u t r i e n t s 41 3.4.1 Ammonia 42 3.4.2 N i t r a t e 47 3.4.3 Orthophosphate 50 4. DISCUSSION 54 4.1 C o l i f o r m Removal 54 4.2 R e d u c t i o n of Chemical Oxygen Demand 57 4.3 Changes i n Ammonia 57 4.4 N i t r i f i c a t i o n 59 4.5 I n o r g a n i c N i t r o g e n Removal 62 4.6 Orthophosphate Removal 64 5. CONCLUSIONS 66 6 . RECOMMENDATIONS 68 7. BIBLIOGRAPHY 69 APPENDIX 75 v LIST OF TABLES 1. P e r c o l a t i o n Rates and Bulk D e n s i t i e s 23 2. Raw Sewage and septic Tank Effluent Characteristics 26 3. Loa d i n g Rates and Channel Flow .........2d 4. I n f l u e n c e of U n s a t u r a t e d Flow on C o l i f o r m s 38 5. I n f l u e n c e of S a t u r a t e d Flow on C o l i f o r m s 40 6. E f f l u e n t COD 41 7. R e l a t i v e Adjustment F a c t o r s f o r D i l u t i o n 42 8. I n f l u e n c e of U n s a t u r a t e d Flow on Ammonia 43 9. I n f l u e n c e of S a t u r a t e d Flow on Ammonia 44 10. I n f l u e n c e of U n s a t u r a t e d Flow on N i t r a t e 47 11. I n f l u e n c e of S a t u r a t e d Flow on N i t r a t e 48 12. I n f l u e n c e of U n s a t u r a t e d Flow on Orthophosphate 51 13. I n f l u e n c e of S a t u r a t e d Flow on Orthophosphate 51 14. P e r c e n t of I n f l u e n t Ammonia N i t r i f i e d and P e r c e n t of I n f l u e n t I n o r g a n i c N i t r o g e n Removed 61 15. P e r c e n t i n I n f l u e n t Orthophosphate Removed 64 v i LIST OF FIGURES 1. S e p t i c Tank - S o i l A b s o r p t i o n F i e l d 3 2. G r a i n S i z e A n a l y s i s of S o i l s 16 3. P r o f i l e of E x p e r i m e n t a l Channel ...18 4. U n i t C o n f i g u r a t i o n 20 5. Feed C o n f i g u r a t i o n s 25 6. Dosing Siphon 27 7. T o t a l C o l i f o r m s f o r 0.46 metres of U n s a t u r a t e d S o i l 34 8. T o t a l C o l i f o r m s f o r 0.91 metres of U n s a t u r a t e d S o i l 34 9. F e c a l C o l i f o r m s f o r 0.46 metres of U n s a t u r a t e d S o i l 35 10. F e c a l C o l i f o r m s f o r 0.91 metres of U n s a t u r a t e d S o i l 35 11. T o t a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 0.61 metres From I n l e t 36 12. T o t a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 1.67 metres From I n l e t . . 36 13. T o t a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 2.74 metres From I n l e t 36 14. F e c a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 0.61 metres From I n l e t 37 15. F e c a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 1.67 metres From I n l e t 37 16. F e c a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 2.74 metres From I n l e t 37 17. Ammonia f o r Loamy-Sand F i l l e d Channel 0.0 metres U n s a t u r a t e d S o i l . . . . . . . . . . 45 v i i 18. Ammonia f o r Sand F i l l e d Channel 0.0 metres U n s a t u r a t e d S o i l 45 19. Ammonia f o r Loamy-Sand F i l l e d Channels 46 20. Ammonia f o r Sand F i l l e d Channels 46 21. N i t r a t e f o r Loamy-Sand F i l l e d Channels 49 22. N i t r a t e f o r Sand F i l l e d Channels 49 23. N i t r a t e f o r Loamy-Sand F i l l e d Channel 0.45 metres U n s a t u r a t e d S o i l 50 24. Orthophosphate f o r Loamy-Sand F i l l e d Channels 52 24. Orthophosphate f o r Sand F i l l e d Channels 52 26. I n f l u e n t Orthophosphate and Mean Channel Orthophosphate.... 53 v i i i ACKNOWLEDGEMENT The au t h o r s i n c e r e l y thanks h i s s u p e r v i s o r , P r o f e s s o r J.W. Atwa t e r , f o r h i s s u p p o r t and guidance d u r i n g t h i s s t u d y . The a u t h o r a l s o wishes t o thank the Richmond, B.C. P u b l i c H e a l t h U n i t f o r t h e i r f i n a n c i a l s u p p o r t i n t h i s s t u d y , Goodbrand C o n s t r u c t i o n of A l d e r g r o v e , B.C. f o r s u p p l y i n g s o i l m a t e r i a l , and Mr. G.S. McKinney, P.Eng. and Dr. J . de V r i e s f o r t h e i r s u g g e s t i o n s . A s s i s t a n c e was a l s o r e c e i v e d from Sue J a s p e r , Susan L i p t a k , and P a u l a P a r k i n s o n of the E n v i r o n m e n t a l E n g i n e e r i n g L a b o r a t o r y . T h i s s t u d y was su p p o r t e d by a N a t i o n a l S c i e n c e and E n g i n e e r i n g Research C o u n c i l of Canada g r a n t . i x 1. INTRODUCTION 1.1 O n - s i t e Waste Treatment The a p p l i c a t i o n of o n - s i t e d o m e s t i c waste t r e a t m e n t , and domestic waste t r e a t m e n t i n g e n e r a l , remains an i m p o r t a n t i s s u e due t o the u n a c c e p t a b i l i t y of raw waste d i s c h a r g e s , of any s i z e , i n t o the environment. Such d i s c h a r g e s a r e u n a c c e p t a b l e because of h e a l t h , e n v i r o n m e n t a l and a e s t h e t i c a s p e c t s . The danger t o p u b l i c h e a l t h from raw waste d i s c h a r g e s , due t o the c o n t a m i n a t i o n of p o t a b l e water s u p p l i e s and b a t h i n g w a t e r , i s q u i t e c l e a r . Less o b v i o u s a r e the p o t e n t i a l e n v i r o n m e n t a l hazards such as oxygen d e p l e t i o n and t h e r e s u l t i n g a q u a t i c damage. Algae growth and odour a r e problems of an a e s t h e t i c n a t u r e which can be caused by raw waste d i s c h a r g e s . The i d e a l o n - s i t e waste, t r e a t m e n t s y s t e m can be d e s c r i b e d as a p r o c e s s i n which d o m e s t i c wastewater g e n e r a t e d on the s i t e r e c e i v e s waste t r e a t m e n t on the same s i t e , t o reduce the s o l i d s and b i o d e g r a d e a b l e m a t e r i a l , w i t h t h e r e m a i n i n g l i q u i d d i s c h a r g e d t o the ground f o r subsequent t r e a t m e n t and e n t r y i n t o the groundwater system. The use of o n - s i t e waste t r e a t m e n t may be by c h o i c e , or as an economic a l t e r n a t i v e t o s m a l l communities where c o s t p r o h i b i t s the i n s t a l l a t i o n and maintenance of the c o n v e n t i o n a l sewage c o l l e c t i o n system and e n d - o f - p i p e t r e a t m e n t . In a r u r a l s e t t i n g o n - s i t e waste t r e a t m e n t i s o f t e n the o n l y v i a b l e a l t e r n a t i v e f o r a c c e p t a b l e d o m e s t i c waste d i s p o s a l . A number of o p t i o n s e x i s t f o r the a p p l i c a t i o n of o n - s i t e d o m e s t i c waste t r e a t m e n t t e c h n o l o g y . The s i m p l e s t system i s the 1 s e p t i c tank - s o i l a b s o r p t i o n f i e l d or p i t , which u t i l i z e s an I n d i v i d u a l s e p t i c tank f o r the removal of s o l i d s and some b l o d e g r a d a t i o n , f o l l o w e d by an a b s o r p t i o n f i e l d or p i t t o d i s p o s e of the l i q u i d (See f i g u r e 1 ) . An a l t e r n a t e system t o t h i s u t i l i z e s a s m a l l a c t i v a t e d s l u d g e system, i n s t e a d of the s e p t i c tank f o r i n i t i a l t r e a t m e n t , f o l l o w e d by the same a b s o r p t i o n f i e l d or p i t . V a r i a t i o n s can a l s o be made on the a b s o r p t i o n f i e l d i t s e l f u t i l i z i n g a mounded f i e l d or an e v a p o t r a n s p i r a t i o n bed when the i n s i t u s o i l m a t e r i a l i s u n a c c e p t a b l e f o r d i r e c t d i s p o s a l of the l i q u i d . C o l l e c t i v e d i s p o s a l u t i l i z i n g t he same systems, but on a l a r g e r s c a l e t o s a t i s f y two or more u s e r s , i s another v a r i a t i o n which i s i n use. In s p i t e of a l l t h e s e v a r i a t i o n s , the s e p t i c tank - s o i l a b s o r p t i o n f i e l d s t i l l remains the most commonly used system. The s e p t i c t a n k , because of i t s s i m p l e c o n s t r u c t i o n and i n s t a l l a t i o n , low maintenance, and r e l a t i v e l y low c o s t , remains e s s e n t i a l l y out of s i g h t and mind of the u s e r . The s o i l a b s o r p t i o n f i e l d , w i t h no maintenance, a s i m p l e i n s t a l l a t i o n , and a r e l a t i v e l y l o n g l i f e , remains c o m p l e t e l y out of s i g h t and mind of the u s e r . The c o m b i n a t i o n of the two p r o v i d e s what c o u l d be d e s c r i b e d as a p e r f e c t o n - s i t e d i s p o s a l s ystem under i d e a l c o n d i t i o n s . 1.2 R a t i o n a l e f o r Experiment The c o n t r o l of the i n s t a l l a t i o n of o n - s i t e d i s p o s a l systems i n the P r o v i n c e of B r i t i s h Columbia comes from two departments w i t h i n the p r o v i n c i a l government. D i s c h a r g e s g r e a t e r than 22,730 l i t r e s (5000 i m p e r i a l g a l l o n s ) per day ,and combined d i s c h a r g e s from two or more d w e l l i n g s a r e c o n t r o l l e d by the M i n i s t r y of t h e 2 F i g u r e 1 . S e p t i c T a n k - S o i l A b s o r p t i o n F i e l d E n v i r o n m e n t t h r o u g h t h e P o l l u t i o n C o n t r o l O b j e c t i v e s f o r M u n i c i p a l T y p e W a s t e D i s c h a r g e s i n B r i t i s h C o l u m b i a . S i n g l e d i s c h a r g e s l e s s t h a n 2 2 , 7 3 0 l i t r e s p e r d a y a r e c o n t r o l l e d b y t h e M i n i s t r y o f H e a l t h t h r o u g h t h e P r o v i n c i a l H e a l t h A c t . T h e s e p t i c t a n k - s o i l a b s o r p t i o n c o m b i n a t i o n g e n e r a l l y f a l l s u n d e r t h e g u i d e l i n e s o f t h e B r i t i s h C o l u m b i a H e a l t h A c t , w h i c h o u t l i n e s a n u m b e r o f c r i t e r i a t h a t m u s t b e m e t b e f o r e a p p r o v a l f o r a d i s p o s a l f i e l d c a n b e o b t a i n e d . T h e s e c r i t e r i a i n c l u d e a v e r t i c a l s e p a r a t i o n d i s t a n c e b e t w e e n t h e g r o u n d s u r f a c e a n d t h e g r o u n d w a t e r t a b l e , a n d s e v e r a l h o r i z o n t a l s e p a r a t i o n d i s t a n c e s , i n a d d i t i o n t o t h e p e r c o l a t i o n t e s t . A l l o f t h e c r i t e r i a a r e i n t e n d e d t o a t t a i n t h e b e s t p o s s i b l e e f f l u e n t r e n o v a t i o n t h u s m i n i m i z i n g t h e t h r e a t t o h u m a n h e a l t h . S e c t i o n 6 . 1 6 o f t h e B . C . H e a l t h A c t o u t l i n e s t h e r e q u i r e m e n t o f a m i n i m u m o f 1 . 2 m e t r e s (4 f e e t ) s e p a r a t i o n b e t w e e n t h e g r o u n d s u r f a c e a n d t h e g r o u n d w a t e r t a b l e b e f o r e t h e i n s t a l l a t i o n o f a t i l e f i e l d c a n b e a p p r o v e d ( S e e f i g u r e 1 ) . S e c t i o n 6 . 1 9 d e a l s w i t h s e v e r a l h o r i z o n t a l s e p a r a t i o n d i s t a n c e s b e t w e e n t h e a b s o r p t i o n f i e l d a n d v a r i o u s f e a t u r e s w i t h i n t h e p r o p e r t y , i n c l u d i n g a 3 . 0 m e t r e ( 1 0 f o o t ) h o r i z o n t a l s e p a r a t i o n b e t w e e n t h e t i l e f i e l d a n d p e r i m e t e r d r a i n s , a n d t h e t i l e f i e l d a n d t h e p r o p e r t y l i n e . T h e s e g u i d e l i n e s d o n o t c o n s i d e r p e r o l a t i o n r a t e , s o i l t y p e , o r g r o u n d w a t e r c o n d i t i o n , a l l o f w h i c h m a y i n f l u e n c e t h e e f f i c i e n c y o f t h e s o i l a b s o r p t i o n f i e l d . A s a r e s u l t t h e s e g u i d e l i n e s m a y o v e r s i m p l i f y s i t u a t i o n s w h i c h r e q u i r e a m o r e c o m p r e h e n s i v e l y d e s i g n e d o n - s i t e s e w a g e d i s p o s a l s y s t e m . 4 L a n d d e v e l o p m e n t i s p u t t i n g more p r e s s u r e on l a n d w h i c h i s l e s s t h a n i d e a l f o r o n - s i t e w a s t e w a t e r d i s p o s a l . H i g h g r o u n d w a t e r t a b l e s , and d e c r e a s e d h o r i z o n t a l s e p a r a t i o n d i s t a n c e s , a s a r e s u l t o f s m a l l e r l o t s i z e s , may p r o h i b i t l a n d d e v e l o p m e n t i n may c a s e s i n t h e f u t u r e . T h e r e a p p e a r s t o be a need f o r t h e r e - e v a l u a t i o n o f t h e s e s p e c i f i c g u i d e l i n e s . R e s e a r c h i n t o t h e s e g u i d e l i n e s s h o u l d be s p e c i f i c t o l o c a l needs u t i l i z i n g l o c a l c o n d i t i o n s and s o i l s . The s p e c i f i c o r i g i n o f t h e s e g u i d e l i n e s i s n o t known, t h e r e f o r e t h e r e i s a need t o e n s u r e t he g u i d e l i n e s b e l o n g t o B r i t i s h C o l u m b i a n c o n d i t i o n s a n d n o t c o n d i t i o n s i n o t h e r p a r t s o f N o r t h A m e r i c a . I t was t h e o b j e c t i v e o f t h i s s t u d y t o r e v i e w and r e e s t a b l i s h t h e s c i e n t i f i c b a s i s f o r t h e 1.2 m e t r e d e p t h t o t h e g r o u n d w a t e r t a b l e , and t h e 3.0 met re h o r i z o n t a l s e p a r a t i o n d i s t a n c e . T h i s r e v i e w and s t u d y may p o i n t t o a d d i t i o n a l c o n s i d e r a t i o n s f o r t h e s e e x i s t i n g r e g u l a t i o n s u n d e r t h e l i m i t i n g c o n d i t i o n s o f a h i g h g r o u n d w a t e r t a b l e , o r a r e d u c e d s e p a r a t i o n d i s t a n c e , p e r t a i n i n g t o s e v e r a l d i f f e r e n t t y p e s o f s o i l . 1.3 L i t e r a t u r e R e v i e w 1.3.1 O n - s i t e Waste T r e a t m e n t P r o b l e m s A l t h o u g h t h e s e p t i c t a n k - s o i l a b s o r p t i o n s y s t e m ( S T - S A S ) may be c o n s i d e r e d an i d e a l was te d i s p o s a l s y s t e m f o r i t s s i m p l i c i t y and o v e r a l l r e l i a b i l i t y , i t i s c e r t a i n l y n o t w i t h o u t s e r i o u s p r o b l e m s . The c o n t a m i n a t i o n o f g r o u n d w a t e r and t h e s u b s e q u e n t c o n t a m i n a t i o n o f p o t a b l e w a t e r s u p p l i e s i s a v e r y s e r i o u s c o n s i d e r a t i o n . H a g e d o r n e t a l (1981) d i s c u s s e s t h e m i g r a t i o n o f c o l i f o r m b a c t e r i a u n d e r c o n d i t i o n s o f s a t u r a t e d f l o w ; t h e 5 d i s t a n c e of t r a v e l ranges from 3 t o 30 metres i n a sand t o 450 t o 820 metres i n a c o a r s e g r a v e l . Hagedorn e t a l (1978) a l s o r e p o r t s on the r e l a t i v e l y f a s t t r a v e l time f o r f e c a l b a c t e r i a under a f l o w g r a d i e n t of 2 p e r c e n t . F e c a l c o l i f o r m c o n t a m i n a t i o n and the a s s o c i a t e d p a t h o g e n i c b a c t e r i a and v i r u s c o n t a m i n a t i o n a r e not the o n l y c o n c e r n s w i t h r e g a r d t o p o t a b l e water. Peavy e t a l (1977), and T y l e r e t a l (1977) note t h e a s s o c i a t i o n between h i g h l e v e l s of n i t r a t e i n groundwater and the occurance of methamoglobanemia i n s m a l l c h i l d r e n . The s o u r c e of t h i s n i t r a t e can be the n i t r i f i c a t i o n of ammonia from s e p t i c tank e f f l u e n t d i s p o s a l i n s o i l . E n v i r o n m e n t a l concerns have a l s o been r a i s e d r e g a r d i n g the ST-SAS. V i r a r a g h a v a n and Warnock (1976) examined the q u e s t i o n of n u t r i e n t c o n t a m i n a t i o n of s u r f a c e water b o d i e s and the subsequent l a k e e u t r o f i c a t i o n . The use of s o i l d i s p o s a l o f s e p t i c tank e f f l u e n t a l o n g a s h o r e l i n e i s q u e s t i o n e d as a s o u r c e of n i t r o g e n and phosphorus f o r the groundwater, and u l t i m a t e l y the s u r f a c e water. Jones and Lee (1979) a l s o comment on t h e l i k e l i h o o d of ST-SAS b e i n g a s o u r c e of phosphorus f o r s u r f a c e w a t e r s , p a r t i c u l a r l y i n r e c r e a t i o n a l developments near l a k e s . Oldham and Kennedy (1972) examined the n u t r i e n t l o a d i n g from s e p t i c tank e f f l u e n t f i e l d s on s u r f a c e waters w i t h i n t h e Okanagan V a l l e y of B r i t i s h Columbia, and suggested t h a t s e p t i c tank e f f l u e n t may be r e s p o n s i b l e f o r l o c a l i z e d s u r f a c e water q u a l i t y problems. Another p o t e n t i a l problem a r e a f o r the ST-SAS i s a system f a i l u r e due t o a l o s s of i n f i l t r a t i o n c a p a c i t y of the s o i l . O l l v i e r i e t a l (1981) d i s c u s s e s the e x p e c t e d 50 p e r c e n t f a i l u r e r a t e of a l l s o i l a b s o r p t i o n f i e l d s w i t h i n 25 y e a r s of o p e r a t i o n , and t h e a s s o c i a t e d c o n t a m i n a t i o n o f s u r f a c e w a t e r by b a c t e r i a . The mechan i sms f o r l o s s o f i n f i l t r a t i o n c a p a c i t y due t o p o r e c l o g g i n g a r e d i s c u s s e d by de V r i e s (1972) i n t e r m s o f t h e h y d r a u l i c l o a d i n g o f a s o i l . 1 .3 .2 Changes i n T e c h n o l o g y In o r d e r t o a v o i d t h e p r o b l e m s m e n t i o n e d , and i n o r d e r t o o b t a i n t h e maximum e f f i c i e n c y and l i f e o f e v e r y e f f l u e n t d i s p o s a l f i e l d , t h e methods f o r a p p l i c a t i o n o f t h i s t e c h n o l o g y a r e b e c o m i n g i n c r e a s i n g l y s o p h i s t i c a t e d . The f u n d a m e n t a l c h a n g e s have o c c u r r e d w i t h t h e r e e v a l u a t i o n o f t h e o r i g i n a l p e r c o l a t i o n t e s t . W i n n e g e r g e r (1974) d e s c r i b e s a n e r r o r made i n t h e o r i g i n a l d e v e l o p m e n t o f t h e p e r c o l a t i o n t e s t b y H e n r y Ryon i n 1 9 2 8 , r e g a r d i n g t h e use o f b o t t o m a r e a s o n l y a s t h e a c t i v e a b s o r p t i o n s u r f a c e . W i n n e b u r g e r ( 1 9 7 4 ) , and O l i v i e r i e t a l (1981) s u g g e s t a m o d i f i c a t i o n t o R y o n ' s o r i g i n a l c u r v e t o c o n s i d e r a c t i v e s i d e w a l l a b s o r p t i o n . H e a l y and Laak (1973) o u t l i n e t h e f a c t o r s a f f e c t i n g t h e p e r c o l a t i o n t e s t , i n c l u d i n g s i z e a n d s h a p e o f t h e h o l e , p e r m e a b i l i t y and p o s i t i o n o f t h e g r o u n d w a t e r t a b l e , and c o n c l u d e t h e p e r c t e s t s h o u l d n o t be u s e d a s a means f o r d e t e r m i n i n g h y d r a u l i c l o a d s on s e e p a g e b e d s . The d i s s a t i s f a c t i o n w i t h t h e p e r c o l a t i o n t e s t p r o m p t e d Bouma e t a l (1972) t o i n v e s t i g a t e methods t o r e p l a c e o r comp lement t h e p e r c t e s t , c o n c l u d i n g t h e p e r c t e s t i t s e l f i s a n o v e r s i m p l i e d a p p r o a c h t o a p r o b l e m w h i c h I n v o l v e s t h e d i s p o s a l o f n u t r i e n t s and h a r m f u l m i c r o o r g a n i s m s , a s w e l l a s a l i q u i d . As a b u r e a u c r a t i c method o f m a i n t a i n i n g p e r f o r m a n c e o f t h e S T - S A S , O l i v i e r i e t a l (1981) s u g g e s t s a 7 program of f i e l d i n s p e c t i o n by l o c a l h e a l t h a u t h o r i t i e s t o ensure t h a t a c t i v i t i e s such as tank c l e a n i n g and f i e l d r e s t i n g a r e c a r r i e d o u t . To complement the cha n g i n g i n v e s t i g a t i o n and maintenance a s p e c t s of s o i l a b s o r p t i o n f i e l d s , d i f f e r e n t c o n s t r u c t i o n t e c h n i q u e s a re b e i n g i n v e s t i g a t e d and used. The placement of a t h i c k l a y e r of s o i l , not n a t i v e t o a s i t e , over the i n s i t u s o i l i s a t e c h n i q u e which a l l o w s o n - s i t e waste t r e a t m e n t on l a n d which would not n o r m a l l y be s u i t a b l e . T h i s mounded s o i l a b s o r p t i o n f i e l d p r o v i d e s the n e c e s s a r y u n s a t u r a t e d zone i n ca s e s of h i g h groundwater t a b l e , and a l s o p r o v i d e s d i s p e r s i o n of l i q u i d i n cases of low i n f i l t r a t i o n r a t e . Simons and Magdoff (1979) performed a l a b o r a t o r y e v a l u a t i o n of the d e s i g n parameters f o r mound d i s p o s a l systems c o n s t r u c t e d of sand f i l l . They c o n c l u d e d t h a t a maximum l o a d i n g r a t e of 2 c e n t i m e t r e s per day over the e n t i r e mound would a v o i d s o i l c l o g g i n g on the mound. Magdoff e t a l (1974) c o n s t r u c t e d columns r e p r e s e n t i n g mound type d i s p o s a l systems, and a c h i e v e d complete removal of f e c a l c o l i f o r m s and s i g n i f i c a n t r e d u c t i o n s i n n i t r o g e n and phosphorus. A f i e l d s t u d y by Bouma (1975) on mound systems c o n c l u d e d t h a t t h e y can be v e r y e f f e c t i v e f o r e f f l u e n t d i s p o s a l due m a i n l y t o the d e s i g n c o n t r o l s which can be a p p l i e d t o each s p e c i f i c f i e l d . Mixed media f i l t e r s may be c o n s i d e r e d a v a r i a t i o n on the mounded system, where m i x t u r e s of d i f f e r e n t s o i l m a t e r i a l s can be used f o r the mound. Stewart e t a l (1979) found t h a t a top s o i l -sand m i x t u r e c o u l d s t i l l t a k e advantage of the s u p e r i o r h y d r a u l i c 8 and a e r a t i o n p r o p e r t i e s of sand. Chowdry (1979) i n v e s t i g a t e d m i x t u r e s of sand and red mud, and sand and l i m e s t o n e , and found improved phosphorus r e m o v a l . Another c o n s t r u c t i o n t e c h n i q u e t o improve t i l e f i e l d performance i s the use of d r a i n a g e t i l e t o lower the groundwater t a b l e around a t i l e f i e l d . W i l s o n e t a l (1982) found t h a t a d r a i n a g e t i l e a t a depth of 1.8 metres and a s e t b a c k of 3 metres from the t i l e f i e l d lowered the water t a b l e an average of one metre, and r e s u l t e d i n no s i t u a t i o n s of u n a c c e p t a b l e water q u a l i t y . 1.3.3 Importance of U n s a t u r a t e d Zone The l i t e r a t u r e p r e s e n t s an u n d i s p u t e d r e c o g n i t i o n of the importance, and g e n e r a l agreement on t h e depth of u n s a t u r a t e d s o i l r e q u i r e d f o r s u c c e s s f u l d i s p o s a l of s e p t i c tank e f f l u e n t , p a r t i c u l a r l y w i t h r e s p e c t t o c o l i f o r m b a c t e r i a removal. H a n s e l and Machmeler (1980) s t a t e t h a t i t i s a b s o l u t e l y n e c e s s a r y t o have a t l e a s t 0.9 metres of u n s a t u r a t e d s o i l f o r p r o p e r t r e a t m e n t . Brown e t a l (1977) observed t h a t 1.0 metres of u n s a t u r a t e d s o i l removed a l l c o l i f o r m s and Peavy e t a l (1977) observed t h a t 1.2 metres of u n s a t u r a t e d s o i l a d e q u a t e l y reduced c o l i f o r m s , phosphorus, and b i o d e g r a d e a b l e m a t e r i a l . Bouma (1977) agrees t h a t 0.9 metres of s o i l w i l l a d e q u a t e l y remove pa t h o g e n i c b a c t e r i a and v i r u s e s , but he q u a l i f i e s t h i s on the b a s i s t h a t the s o i l not be h y d r a u l i c a l l y o v e r l o a d e d . S e v e r a l r e s e a r c h e r s note r e d u c t i o n of c o l i f o r m s i n c o n s i d e r a b l y l e s s t h a n 1.0 metres of u n s a t u r a t e d s o i l . T y l e r e t a l (1977) observed a 3 l o g r e d u c t i o n of c o l i f o r m s i n the f i r s t 30 c e n t i m e t r e s of 9 u n s a t u r a t e d s o i l and observed a l m o s t complete removal i n the second 30 c e n t i m e t r e s . Stewart e t a l (1979) observed no p e n e t r a t i o n of f e c a l c o l i f o r m s below 30 c e n t i m e t r e s i n e i t h e r sand or loamy sand. W i l s o n e t a l (1982) a l s o note t h a t an u n s a t u r a t e d d i s t a n c e of as l i t t l e as 23 c e n t i m e t r e s i n c o n j u n c t i o n w i t h a 3 metre h o r i z o n t a l s e t b a c k was s u f f i c i e n t t o ensure a c c e p t a b l e water q u a l i t y . 1.3.4 R e c o g n i t i o n of S a t u r a t e d Zone The u n s a t u r a t e d zone can s u c c e s s f u l l y d e c r e a s e c o l i f o r m b a c t e r i a , b i o d e g r a d a b l e m a t e r i a l , n i t r o g e n and phosphorus i n a s e p t i c t i l e f i e l d . On the o t h e r hand, the s a t u r a t e d zone i s known to c r e a t e problems of c o l i f o r m m i g r a t i o n , c o n t a m i n a t i o n o f p o t a b l e water s u p p l i e s , and s u r f a c e water p o l l u t i o n l e a d i n g t o e u t r o p h i c a t i o n . F o r t u n a t e l y a number of b e n e f i t s can be a s s o c i a t e d w i t h the s a t u r a t e d zone. Reneau (1977) r e p o r t e d d e n i t r i f i c a t i o n i n the s a t u r a t e d zone due t o a n a e r o b i c c o n d i t i o n s , a l t h o u g h dependent upon an a v a i l a b l e o r g a n i c c a r b o n s o u r c e . S t e w a r t and Reneau (1981) note r e d u c t i o n of c o l i f o r m s i n the d i r e c t i o n of groundwater f l o w , p r o m o t i n g th e i d e a of c o l i f o r m r e d u c t i o n under c o n d i t i o n s of a h y d r a u l i c g r a d i e n t . Under c o n d i t i o n s of no d i s c e r n i b l e h y d r a u l i c g r a d i e n t t h e y observed downward m i g r a t i o n of c o l i f o r m s r e s u l t i n g i n the c o n t a m i n a t i o n of a s h a l l o w a q u i f e r . Hagedorn (1984) s u g g e s t s s e d i m e n t a t i o n of b a c t e r i a l c l u s t e r s can o c c u r under c o n d i t i o n s of s a t u r a t e d f l o w . 10 1.3.5 R e d u c t i o n of C o l i f o r m s A number of mechanisms a r e r e s p o n s i b l e f o r the removal of c o l i f o r m b a c t e r i a i n a s e p t i c tank s o i l a b s o r p t i o n f i e l d . Hagedorn (1984) r e p o r t s b a c t e r i a l t r a v e l i s l i m i t e d by p h y s i c a l s t r a i n i n g or f i l t r a t i o n , w i t h the degree of r e t e n t i o n i n v e r s e l y p r o p o r t i o n a l t o the p a r t i c l e s i z e s of the s o i l . B u t l e r e t a l (1954) a l s o agree t h a t b a c t e r i a l removal d e c r e a s e s w i t h l a r g e p a r t i c l e s i z e s . T y l e r e t a l (1977) r e p o r t b a c t e r i a l d i e o f f by a t t r i t i o n of n u t r i e n t s . R e t e n t i o n time i s a l s o an i m p o r t a n t f a c t o r i n r e d u c i n g c o l i f o r m s . R e t e n t i o n time i n the u n s a t u r a t e d zone i s a f u n c t i o n of the u n s a t u r a t e d f l o w c o n d i t i o n , which i n t u r n i s a f u n c t i o n of the c l o g g e d l a y e r or biomat a t the s o i l - t i l e f i e l d i n t e r f a c e . Simons and Magdoff (1979), and T y l e r e t a l (1977) d e s c r i b e the c l o g g i n g mat as an a n a e r o b i c l a y e r of s l i m e c o v e r e d b a c t e r i a . T y l e r goes on t o r e p o r t t h a t u n s a t u r a t e d f l o w o c c u r s due t o the c r u s t i n g l a y e r a t the s o i l - t i l e f i e l d i n t e r f a c e , and t h a t u n d e s i r e d s a t u r a t e d f l o w c o u l d p r e v a i l w i t h o u t i t . A d s o r p t i o n of b a c t e r i a onto s o i l p a r t i c l e s i s a l s o e f f e c t i v e i n r e t a i n i n g b a c t e r i a , a c c o r d i n g t o Hagedorn (1984), p a r t i c u l a r l y i n s o i l s w i t h h i g h e r c l a y c o n t e n t s . The a c t i o n of t o x i c c h e m i c a l s , p a r t i c u l a r l y a n t i b i o t i c s produced i n the f i r s t 0.6 metres of s o i l i s a nother f a c t o r i n r e d u c i n g c o l i f o r m numbers r e p o r t e d by T y l e r e t a l (1977). 1.3.6 R e d u c t i o n of B i o d e g r a d e a b l e M a t e r i a l B i o d e g r a d e a b l e m a t e r i a l , measured i n the form of b i o c h e m i c a l oxygen demand (BOD), or c h e m i c a l oxygen demand (COD) 11 can be almost c o m p l e t e l y removed by the u n s a t u r a t e d zone a c c o r d i n g to Magdoff e t a l (1974). B a c t e r i a l m e t a bolism w i t h i n the ' l i v i n g f i l t e r ' of the u n s a t u r a t e d s o i l zone i s r e s p o n s i b l e f o r the r e d u c t i o n . 1.3.7 Changes i n N i t r o g e n N i t r o g e n compounds undergo a s e r i e s of r e a c t i o n s w i t h i n a s o i l p r o f i l e r e s u l t i n g i n the t r a n s f o r m a t i o n and the subsequent removal of n i t r o g e n from the s o i l system, or the s t o r a g e of n i t r o g e n i n the s o i l . Lance (1975) d e s c r i b e s n i t r o g e n removal i n terms of d e n i t r i f i c a t i o n , v o l a t i z a t i o n or c h e m o d e n i t r i f i c a t i o n . Storage of n i t r o g e n i s c r e d i t e d t o ammonium a d s o r p t i o n by s o i l c a t i o n exchange, f i x a t i o n by expanding c l a y m i n e r a l s , a d s o r p t i o n onto o r g a n i c m a t t e r , or i n c o r p o r a t o n i n t o m i c r o b i a l t i s s u e . Lance (1972) observed t h a t ammonium i o n c a t i o n exchange i s g e n e r a l l y not permanent because the ammonium i o n can be r e p l a c e d by o t h e r c a t i o n s or be removed by n i t r i f y i n g b a c t e r i a ; o n l y ammonium ions adsorbed i n a zone t h a t remains a n a e r o b i c a r e immobile. P r e u l and S c h r o e p f e r (1968) c o n c l u d e d t h a t a d s o r p t i o n and b i o l o g i c a l a c t i o n a r e the main f a c t o r s which c o n t r o l n i t r o g e n i n t he s o i l a b s o r p t i o n f i e l d , a d d i n g t h a t e i t h e r f a c t o r may dominate depending on the s o i l e nvironment. A d s o r p t i o n i s the im p o r t a n t mechanism when n i t r o g e n i s i n t h e form of the ammonium i o n (NH4+), and a d s o r p t i o n i s g r e a t e s t i n f i n e g r a i n e d m a t e r i a l . S i k o r a and Corey (1975) c l a s s i f y the endforms f o r n i t r o g e n i n a s o i l a b s o r p t i o n f i e l d i n terms of the s o i l m a t e r i a l p r e s e n t . N i t r a t e was c o n s i d e r e d the endform i n sands, sand loams, loamy 12 sands and loams; both n i t r a t e and ammonia were c o n s i d e r e d endforms i n s i l t loams and s i l t y c l a y loams; and ammonia was the endform i n c l a y loams and c l a y . The most s i g n i f i c a n t n i t r o g e n t r a n s f o r m a t i o n i n a w e l l a e r a t e d u n s a t u r a t e d zone i s the n i t r i f i c a t i o n of ammonia. A n d r e o l i e t a l (1979) r e p o r t e d t h a t a t a d e p t h of 0.6 metres, 80 p e r c e n t of the t o t a l n i t r o g e n was i n the form of n i t r a t e . Reneau (1977) r e p o r t e d removal of n i t r a t e as the r e s u l t of d e n i t r l f i c a t i o n , and he documented t h i s r e a c t i o n i n terms of a redox p o t e n t i a l . 1.3.8 R e a c t i o n s of Phosphorus The r e t e n t i o n of phosphorus by s o i l was c l a s s e d by Chowdry (1977) as e i t h e r a c h e m i c a l r e a c t i o n or an a d s o r p t i o n r e a c t i o n . Sawhney and S t a r r (1977) r e p o r t e d phosphorus a d s o r p t i o n and t h e r e g e n e r a t i o n of s o r p t i o n s i t e s upon w e t t i n g and d r y i n g . E n f i e l d and Bledsoe (1975) c o n c l u d e d t h a t phosphorus removal was p r i m a r i l y a p r e c i p i t a t i o n r e a c t i o n f o r m i n g i n s o l u b l e phosphate compounds of aluminum, i r o n and c a l c i u m . Jones and Lee (1979) agreed t h a t m i n e r a l o g y , as opposed t o p a r t i c l e s i z e , c o n t r o l l e d phosphate r e m o v a l ; t h e y observed phosphate s o r p t i o n i n c l a y , i r o n and aluminum based s o i l s , and p r e c i p i t a t i o n i n c a l c a r e o u s s o i l s . 1.4 Method of E x p e r i m e n t a l I n v e s t i g a t i o n 1 .4.1 O b j e c t i v e s The minimum v e r t i c a l s e p a r a t i o n d i s t a n c e between the ground water t a b l e and the s e p t i c t i l e f i e l d i s a d d r e s s e d v e r y c l e a r l y i n the l i t e r a t u r e , w i t h g e n e r a l agreement on a minimum of 1.0 metres (3.2 f e e t ) of u n s a t u r a t e d s o i l . The B r i t i s h Columbia H e a l t h Act s t a t e s a minimum requ i r e m e n t of 1.2 metres (4 f e e t ) between the ground water t a b l e and the n a t u r a l ground s u r f a c e , which reduces t o a minimum of 41 c e n t i m e t r e s (16 i n c h e s ) of u n s a t u r a t e d s o i l when c o n s i d e r i n g a maximum a l l o w a b l e t r e n c h depth of 81 c e n t i m e t r e s (32 i n c h e s ) . The B r i t i s h Columbia g u i d e l i n e s r e q u i r e l e s s than h a l f the u n s a t u r a t e d zone s u g g e s t e d i n the l i t e r a t u r e . The h o r i z o n t a l s e p a r a t i o n d i s t a n c e between t h e s e p t i c t i l e f i e l d and any d r a i n a g e or s u r f a c e f e a t u r e s which may produce a h e a l t h or e n v i r o n m e n t a l hazard i s not c l e a r l y a d d r e s s e d i n the l i t e r a t u r e . The B r i t i s h Columbia H e a l t h A c t s t a t e s a minimum 3.0 metres (10 f e e t ) h o r i z o n t a l s e p a r a t i o n between the s e p t i c t i l e f i e l d and a b u i l d i n g , p a r c e l boundary, or c u r t a i n d r a i n . T h i s d i s t a n c e i n c r e a s e s t o 30.5 metres (100 f e e t ) between the t i l e f i e l d and a sou r c e of d r i n k i n g water, a l a k e , or a stream. The B r i t i s h Columbia g u i d e l i n e s have l i t t l e f o r comparison of t h e i r e f f e c t i v e n e s s . The o b j e c t i v e of the i n v e s t i g a t i o n was t o c o l l e c t e v i d e n c e to s u b s t a n t i a t e the 1.2 metre (4 f e e t ) v e r t i c a l s e p a r a t i o n d i s t a n c e and the 3.0 metre (10 f o o t ) h o r i z o n t a l s e p a r a t i o n d i s t a n c e s t a t e d i n the B r i t i s h Columbia H e a l t h A c t . The s u b s t a n t i a t i o n of the g u i d e l i n e s was done i n terms of the h e a l t h and e n v i r o n m e n t a l a s p e c t s r e l a t e d t o a ST-SAS, and r e p r e s e n t a t i v e s o i l m a t e r i a l s . The h e a l t h a s p e c t was examined by a n a l y z i n g f o r t o t a l and f e c a l c o l i f o r m s , and n i t r a t e . The p o t e n t i a l presence of 14 pathogenic organisms c o u l d be d e t e r m i n e d through the enumeration of f e c a l and t o t a l c o l i f o r m s . The p o t e n t i a l h e a l t h problem of methamoglobanlmea c o u l d be i d e n t i f i e d by d e t e r m i n i n g the n i t r a t e c o n c e n t r a t i o n s i n the e x p e r i m e n t s . The e n v i r o n m e n t a l impacts of a ST-SAS a r e p r i m a r i l y r e l a t e d t o n u t r i e n t enrichment and the presence of b i o d e g r a d e a b l e m a t e r i a l . N u t r i e n t enrichment i s g e n e r a l l y d e termined through the a n a l y s i s f o r n i t r o g e n and phosphorus. In a d d i t i o n t o t h e n i t r a t e - n i t r i t e a n a l y s i s f o r the h e a l t h a s p e c t s , ammonia c o n c e n t r a t i o n s were measured. T h i s p r o v i d e d a complete d e t e r m i n a t i o n of the i n o r g a n i c n i t r o g e n i n the system, which was used f o r an i n o r g a n i c n i t r o g e n b a l a n c e , and an e x a m i n a t i o n of the changes i n n i t r o g e n which c o u l d occur i n the s o i l p r o f i l e , assuming l i t t l e or no o r g a n i c n i t r o g e n c o n v e r s i o n . The o t h e r n u t r i e n t , phosphorus, was measured i n terms of orthophosphate. The measurement of t o t a l n i t r o g e n and t o t a l phosphorus was c o n s i d e r e d , but the dominance of i n o r g a n i c n i t r o g e n and orthophosphate ( S i k o r a and Corey (1976)) w i t h i n t h e s e p t i c tank system i n d i c a t e d t h e s e measurements were un n e c e s s a r y f o r the scope of t h i s i n v e s t i g a t i o n . I n c o n s i d e r a t i o n of the number and f r e q u e n c y of samples t o be t a k e n , the presence of b i o d e g r a d e a b l e m a t e r i a l was d e t e r m i n e d u s i n g c h e m i c a l oxygen demand. The s o i l m a t e r i a l s chosen f o r the i n v e s t i g a t i o n r e p r e s e n t e d a range of m a t e r i a l s which c o u l d be e n c o u n t e r e d i n a s e p t i c t i l e f i e l d . The s o i l t y p e s were a sand and a loamy-sand. The sand was permeable and v e r y w e l l graded; and, based on p e r c o l a t i o n r a t e , would be c o n s i d e r e d a v e r y d e s i r a b l e m a t e r i a l i n which t o d i s p o s e o f s e p t i c t a n k e f f l u e n t . T h e l o a m y - s a n d w a s a l e s s p e r m e a b l e , p o o r l y g r a d e d s o i l w i t h s i g n i f i c a n t f r a c t i o n s o f s i l t a n d g r a v e l s i z e d m a t e r i a l ( S e e f i g u r e 2 ) . 120 PARTICLE DIAMETER m m . F i g u r e 2 . G r a i n S i z e A n a l y s i s o f S o i l s 1 . 4 . 2 E x p e r i m e n t a l S e t - u p T h e e x p e r i m e n t c o u l d h a v e b e e n s e t - u p o n a n y o n e o f t h r e e d i f f e r e n t s c a l e s . A f u l l s c a l e e x p e r i m e n t w o u l d h a v e u s e d a n e x i s t i n g S T - S A S a n d w o u l d h a v e i n v o l v e d d e v i s i n g m e t h o d s t o s a m p l e a n o p e r a t i n g s y s t e m . T h e s e c o n d o p t i o n w a s a p i l o t s c a l e e x p e r i m e n t . T h i s s y s t e m w o u l d h a v e b e e n c o n s t r u c t e d t o s i m u l a t e a f u l l s c a l e e x p e r i m e n t , b u t r e d u c e d i n s i z e . T h e f i n a l o p t i o n 16 was a l a b s c a l e e x p e r i m e n t . T h i s system would have a g a i n been a s i m u l a t i o n of a f u l l s c a l e e x p e r i m e n t , but reduced i n s i z e t o f i t on a bench t o p . The f u l l s c a l e experiment would have r e q u i r e d no c o n s t r u c t i o n of the system I t s e l f , but the a v a i l a b i l i t y of such a system w i t h the d e s i r e d c o n d i t i o n s t o t e s t the u n s a t u r a t e d and s a t u r a t e d zones p r e s e n t e d a problem. C a r e f u l c o n s i d e r a t i o n would have been r e q u i r e d f o r the m o n i t o r i n g of a system o p e r a t i n g under the f l u c t u a t i o n s of day t o day use. The c o n s t r u c t i o n of a system on a p i l o t s c a l e would have a l l o w e d the use of a c l o s e d system, where a l l of the i n p u t s i n t o the s a t u r a t e d and u n s a t u r a t e d zones would have been c o n t r o l l e d . U n f o r t u n a t e l y the c o n s t r u c t i o n of the system would have i n c l u d e d the placement of the s o i l , which would have never i d e n t i c a l l y matched the i n s i t u s o i l c o n d i t i o n s . The l a b s c a l e experiment would have o f f e r e d the economy of s i z e , and t h e r e f o r e would have been e a s i e r t o c o n s t r u c t and m a i n t a i n . The i n s i t u s o i l r e p r e s e n t a t i o n would have a g a i n been a problem, i n a d d i t i o n t o i n t e r f e r e n c e s from the e n c l o s u r e s of the s a t u r a t e d and u n s a t u r a t e d zones. The p i l o t s c a l e experiment was chosen as the b e s t a l t e r n a t i v e f o r the o b j e c t i v e s of t h i s e xperiment because of the u n a v a i l a b i l i t y of a f u l l s c a l e s ystem w i t h the d e s i r e d c o n d i t i o n s . In a d d i t i o n , the a v a i l a b i l i t y of time and space f o r the c o n s t r u c t i o n of the p i l o t s c a l e e xperiment e l i m i n a t e d the use of a l a b s c a l e e x p e r i m e n t . The s a t u r a t e d and u n s a t u r a t e d zones w i t h i n the ST-SAS were i n v e s t i g a t e d s l m u l t a n l o u s l y i n a c l o s e d p i l o t s c a l e experiment 17 ( S e e f i g u r e 3 ) . A s i m u l a t e d s e c t i o n o f a s e p t i c t i l e f i e l d w a s c o n s t r u c t e d w i t h a v e r t i c a l u n s a t u r a t e d s e c t i o n a n d a h o r i z o n t a l s a t u r a t e d s e c t i o n . A s i m u l a t e d s e p t i c t a n k e f f l u e n t was d o s e d a t t h e i n l e t t o t h e v e r t i c a l u n s a t u r a t e d s e c t i o n , a s o c c u r s w h e n s e p t i c t a n k e f f l u e n t f l o w s i n t o a t i l e f i e l d . T h e e f f l u e n t p e r c o l a t e s d o w n w a r d t h r o u g h t h e u n s a t u r a t e d s o i l u n t i l i t m e e t s t h e s a t u r a t e d s o i l a t t h e g r o u n d w a t e r t a b l e . I n t h e e x p e r i m e n t , t h e s e p t i c t a n k e f f l u e n t m e t t h e g r o u n d w a t e r t a b l e a t t h e h o r i z o n t a l s a t u r a t e d s o i l z o n e . T h e s a t u r a t e d z o n e w a s f e d c o n t i n u o u s l y w i t h t a p w a t e r t o s i m u l a t e a h o r i z o n t a l g r o u n d w a t e r f l o w . D O S E D S E P T I C T A N K E F F L U E N T O V E R F L O W 8 S A M P L E S A M P L E 1 S A M P L E ^ 4 I , S A T U R A T E D | S S O I L | .7.—_, T«4 . D E P T H O F ^ U N S A T U R A T E D S O I L 0 - 0 0 m , 0 - 4 6 m , 0 - 9 l m C O N T I N U O U S ' T A P W A T E R F E E D 2 - 7 4 m e t r e s • 6 7 0 - 6 1 0 - 0 0 m e t r e s F i g u r e 3 . P r o f i l e o f E x p e r i m e n t a l U n i t T h e d e p t h o f t h e u n s a t u r a t e d s o i l i n t h e v e r t i c a l s e c t i o n w a s v a r i e d t o s u b s t a n t i a t e t h e 1 . 0 m e t r e ( 3 . 2 f e e t ) u n s a t u r a t e d 18 zone expressed i n the l i t e r a t u r e , and the 0.41 metre (16 i n c h ) u n s a t u r a t e d zone o b t a i n e d from the B r i t i s h Columbia H e a l t h A c t . I n d i v i d u a l s e c t i o n s were c o n s t r u c t e d and m a i n t a i n e d w i t h u n s a t u r a t e d zones of 0.91 metres (3 f e e t ) , 0.46 metres (1.5 f e e t ) , and 0.0 metres. The s e c t i o n w i t h o u t any zone of u n s a t u r a t e d s o i l was m a i n t a i n e d t o observe s e p t i c tank e f f l u e n t i n s a t u r a t e d s o i l o n l y . The zone of s a t u r a t e d s o i l was c o n s t r u c t e d a nominal 3 metres (10 f e e t ) i n l e n g t h t o s u b s t a n t i a t e the minimum 3 metre d i s t a n c e s t a t e d i n the B r i t i s h Columbia H e a l t h A c t . S e v e r a l sample p o i n t s were i n s t a l l e d a l o n g the nominal 3 metre (10 f e e t ) zone of s a t u r a t e d s o i l t o observe the e f f e c t of d i s t a n c e under s a t u r a t e d s l o w c o n d i t i o n s . Two s o i l m a t e r i a l s , a sand and a loamy-sand, were used i n c o n j u c t i o n w i t h the t h r e e v a r i a t i o n s i n the depth of the u n s a t u r a t e d s o i l (0.91 metres, 0.46 metres and 0.00 metres) t o produce s i x i n d i v i d u a l u n i t s f o r the experiment (See f i g u r e 4 ) . Each u n i t was f e d w i t h a s i m u l a t e d s e p t i c tank e f f l u e n t i n an u n s a t u r a t e d v e r t i c a l s e c t i o n , and tap water i n a s a t u r a t e d h o r i z o n t a l s e c t i o n . 1.4.3 E x p e r i m e n t a l P r o c e d u r e s Each of the s i x i n d i v i d u a l u n i t s was o p e r a t e d c o n t i n u o u s l y over a 5 month p e r i o d . Samples from each u n i t were t a k e n a t 3 sample p o i n t s w i t h i n the h o r i z o n t a l s a t u r a t e d s e c t i o n (0.67 metres, 1.67 metres and 2.74 metres from where the u n s a t u r a t e d zone met the s a t u r a t e d z o n e ) , i n a d d i t i o n t o samples of t h e s e p t i c tank e f f l u e n t and the raw sewage s o u r c e . 19 0 0 0 m 0 - 0 0 m Q Z < 1 1 > 2 Q < Z O < -I to / UNSATURATED ZONE 0 9 1 m > _ l ' z o 1-cc o CL a. CO 11 < CC w AND < _ l f 0 - 4 6 m 0 - 4 6 m O z < co 1 > O 2 z < < o cn _J 0 - 9 l m > _) z o 1-NO POR <t a. CO 1 in > _i < < cc o UJ ._J 1-< _ l "SATURATED ZONE PLAN LATERAL SUPPORT'FOR CHANNELS PROFILE F i g u r e 4. U n i t C o n f i g u r a t i o n T w i c e w e e k l y b a c t e r i a l o g i c a l t e s t i n g w a s m a i n t a i n e d t h r o u g h o u t t h e e n t i r e 5 m o n t h p e r i o d . T e s t i n g f o r b i o d e g r a d a b l e m a t e r i a l ( C O D ) w a s m a i n t a i n e d f o r h a l f o f t h e p e r i o d a n d d i s c o n t i n u e d t o a l l o w t e s t i n g o f n u t r i e n t s . 20 2. MATERIALS AND METHODS 2.1 U n i t C o n s t r u c t i o n The i n d i v i d u a l u n i t s used i n the e xperiment were c o n s t r u c t e d to s i m u l a t e a s e c t i o n of a s e p t i c tank a b s o r p t i o n f i e l d . The u n i t s were c o n s t r u c t e d i n L-shaped c h a n n e l s , w i t h the u n s a t u r a t e d zone of s o i l i n the v e r t i c a l s e c t i o n and the s a t u r a t e d zone of s o i l i n the h o r i z o n t a l s e c t i o n (See f i g u r e 3 ) . I n c o n s t r u c t i n g the channels 1.2 metre by 2 .4 metre (4 f o o t by 8 f o o t ) s h e e t s of plywood were u t i l i z e d . The i n t e r n a l d i m e n s i o n of the c h a n n e l was chosen to be a nominal 0.61 metres (2 f e e t ) based on l a b s c a l e s o i l column s t u d i e s (de V r i e s ( 1 9 8 3 ) ) . The 0.61 metre i n t e r n a l d imension a l l o w e d the use of a s i n g l e s h e e t of plywood as a base f o r two c h a n n e l s , t a k i n g advantage of t h e l a t e r a l s u p p o r t one channel would o f f e r the o t h e r a l o n g the common w a l l . Two s h e e t s of plywood were used as a r i g i d base f o r each of the two c h a n n e l u n i t s , which gave ample s u p p o r t f o r the b l o c k i n g and l e v e l l i n g of each u n i t . The h o r i z o n t a l and v e r t i c a l s e c t i o n s of the channels were c o n s t r u c t e d i n d e p e n d e n t l y , and l a t e r j o i n e d . The w a l l s of the h o r i z o n t a l s e c t i o n s were c o n s t r u c t e d u s i n g 1 c e n t i m e t r e plywood w i t h 2.5 c e n t i m e t r e by 5 c e n t i m e t r e s u p p o r t s a t the c o r n e r s and base. L a t e r a l s u p p o r t f o r the two c h a n n e l h o r i z o n t a l s e c t i o n s was a c c o m p l i s h e d u s i n g waste s o i l p i l e d between the u n i t s (See f i g u r e 4 ) . 21 The v e r t i c a l c h a n n e l s e c t i o n s were c o n s t r u c t e d i n a s i m i l a r manner u s i n g 1 c e n t i m e t r e p l y w o o d , w i t h t he c o r n e r s u p p o r t s . L a t e r a l s u p p o r t f o r t h e v e r t i c a l s e c t i o n s was n o t r e q u i r e d . The n o m i n a l 3 m e t r e h o r i z o n t a l c h a n n e l l e n g t h was a c h i e v e d by a t t a c h i n g t h e two c o n s t r u c t e d s e c t i o n s . The 2.4 m e t r e l o n g h o r i z o n t a l s e c t i o n was s e c u r e l y f a s t e n e d t o t h e 0.6 m e t r e w ide v e r t i c a l s e c t i o n c r e a t i n g t h e i n t e g r a t e d s e c t i o n u s e d i n t h e e x p e r i m e n t . S i n c e t h e i n f l o w and o u t f l o w o f sewage was m e a s u r e d o r c o n t r o l l e d i n e a c h c h a n n e l , t h e c h a n n e l s were l i n e d u s i n g a 6 m i l p l a s t i c t o c r e a t e a w a t e r t i g h t s y s t e m . The h o r i z o n t a l s e c t i o n s were f i t t e d w i t h p l a s t i c s u c h t h a t no seams were p r o d u c e d , r e d u c i n g t h e p o s s i b i l i t y o f l e a k a g e . The v e r t i c a l s e c t i o n was a l s o l i n e d u s i n g p l a s t i c w h i c h o v e r l a p p e d w i t h t h e h o r i z o n t a l s e c t i o n . 2.2 S o i l and S o i l P l a c e m e n t Two s o i l t y p e s were c h o s e n f o r t h e e x p e r i m e n t . S o i l s w i t h two v e r y d i f f e r e n t p e r c o l a t i o n r a t e s , and g r a i n s i z e d i s t r i b u t i o n s were d e s i r e d t o a l l o w a c o m p a r i s o n o f t r e a t m e n t c a p a b i l i t y b a s e d on t h e s e p a r a m e t e r s . A w e l l g r a d e d c o n c r e t e s and was o b t a i n e d a s t h e f a s t p e r c o l a t i n g m a t e r i a l , a c h i e v i n g an a v e r a g e p e r c o l a t i o n r a t e o f 0 .3 m i n u t e s p e r c e n t i m e t r e (1 1/6 m i n u t e s p e r i n c h ) . A l o a m y - s a n d was o b t a i n e d a s t h e s l o w e r p e r c o l a t i n g , p o o r l y g r a d e d m a t e r i a l , a c h i e v i n g an a v e r a g e p e r c o l a t i n g r a t e o f 4 .2 m i n u t e s p e r c e n t i m e t r e 15 1/2 m i n u t e s p e r i n c h ) (See t a b l e 1 ) . 22 Table 1. P e r c o l a t i o n Rates and Bulk D e n s i t i e s S o i l Type Ave. P e r c o l a t i o n Rate min/cm Bulk D e n s i t y grams/cm3 E s t i m a t e d P o r o s i t y loamy-sand sand 4.2 0.3 1.22 1.55 0.54 0. 42 A g r a i n s i z e a n a l y s i s was performed on both s o i l t y p e s u s i n g the S i e v e Test f o r the sand f r a c t i o n of the s o i l s and the Hydrometer a n a l y s i s f o r the s i l t and c l a y f r a c t i o n of the s o i l s (Lambe ( 1 9 5 1 ) ) . The c o n c r e t e sand produced the s h o r t s t e e p d i s t r i b u t i o n c urve expected f o r a w e l l graded m a t e r i a l , w h i l e the loamy-sand produced the l o n g e r c u r v e t y p i c a l of a p o o r l y graded m a t e r i a l (See f i g u r e 2 ) . The s o i l s were p l a c e d i n the c h a n n e l s i n l i f t s . Each l i f t was compacted b e f o r e placement of t h e n e x t l a y e r . From e x p e r i e n c e i n l a b o r a t o r y s o i l column s t u d i e s (de V r i e s (1983)) an 8 c e n t i m e t r e l i f t d e p t h was chosen f o r t h e s o i l s ; r a k i n g between l i f t s ensured t h a t no h o r i z o n t a l c h a n n e l l i n g of water would occur because of a smeared i n t e r f a c e . Bulk d e n s i t i e s of a p p r o x i m a t e l y 1.5 grams/cubic c e n t i m e t r e f o r the sand, and 1.2 grams/cubic c e n t i m e t r e f o r the loamy-sand were chosen based on some t y p i c a l l i t e r a t u r e v a l u e s ( F r e e z e and C h e r r y (1979), and F r e n c h ( 1 9 7 2 ) ) . Four t r i a l compactions were c a r r i e d out u s i n g f o u r boxes 30 c e n t i m e t r e s square by 20 c e n t i m e t r e s deep. The compaction of t h e s o i l i n p l a c e was done w i t h a compacting t o o l , c o n s i s t i n g of a wooden rod f i t t e d w i t h a 15 c e n t i m e t r e square wood b l o c k . The b u l k d e n s i t i e s a c t u a l l y a c h i e v e d were 1.55 grams per c u b i c c e n t i m e t r e f o r the sand, and 1.22 grams per c u b i c c e n t i m e t r e f o r t h e loamy sand (See t a b l e 1 ) . 23 The sand r e c e i v e d a r e p e t i t i v e 2 blows, and the loamy-sand r e c e i v e d a r e p e t i t i v e 5 blows t o a c h e i v e the r e q u i r e d d e n s i t i e s . Placement of the s o i l s r e q u i r e d c o n s i d e r a t i o n f o r the i n l e t and o u t l e t f i e l d s of the s i m u l a t e d groundwater f e e d ; t h i s c o n s i s t e d of a w a l l of g r a v e l a t each end of the s a t u r a t e d h o r i z o n t a l c h a n n e l . These g r a v e l f i e l d s were p l a c e d i n l i f t s a l o n g w i t h the s o i l . Two v e r t i c a l sample columns were p o s i t i o n e d a l o n g the h o r i z o n t a l s a t u r a t e d s e c t i o n s b e g i n n i n g w i t h the placement of the f i r s t l i f t of s o i l . These two v e r t i c a l sample columns were l o c a t e d a t 0.61 metres (2.0 f e e t ) and 1.67 metres (5.5 f e e t ) from the c e n t r e of the v e r t i c a l u n s a t u r a t e d zone (See f i g u r e 3 ) . Placement of s o i l i n the v e r t i c a l s e c t i o n s of the c h a n n e l s i n v o l v e d the same procedure as a p p l i e d t o the h o r i z o n t a l c h a n n e l s e c t i o n . E i g h t c e n t i m e t r e l i f t s of s o i l were compacted and r a k e d u n t i l the r e q u i r e d depths of u n s a t u r a t e d s o i l were r e a c h e d . A h o r i z o n t a l s a m p l i n g p o i n t a t the i n t e r f a c e between t h e s a t u r a t e d and u n s a t u r a t e d zones was p o s i t i o n e d , but t h i s s a m p l i n g p o i n t f a i l e d t o o p e r a t e . 2.3 Groundwater and S e p t i c Tank Feed To c r e a t e the s a t u r a t e d f l o w c o n d i t i o n , a s i m u l a t e d groundwater f l o w was needed i n each of the c h a n n e l s . C o n t r o l and measurement of the groundwater f l o w was n e c e s s a r y t o a l l o w f o r i t s e f f e c t i n the d a t a a n a l y s i s . Each c h a n n e l i n the s i x c h a n n e l e x p e r i m e n t a l c o n f i g u r a t i o n was i n s t a l l e d w i t h an i n d i v i d u a l 1.5 l i t r e c o n s t a n t head r e s e r v o i r , and f l o w c o n t r o l v a l v e . These v a l v e s , a t the i n l e t t o the 1.5 l i t r e r e s e r v o i r s , a l l o w e d some c o n t r o l o f f l o w , b u t t w i c e w e e k l y m e a s u r e m e n t s w e r e n e c e s s a r y t o o b t a i n a n a c c u r a t e r e c o r d o f c h a n n e l f l o w s . E a c h o f t h e i n d i v i d u a l r e s e r v o i r s w a s , i n t u r n , f e d f r o m o n e l a r g e 2 0 0 l i t r e f e e d r e s e r v o i r , w h i c h was a l s o m a i n t a i n e d a t a c o n s t a n t h e a d . A c o n s t a n t f l o w o f t a p w a t e r t o t h e f e e d r e s e r v o i r m a i n t a i n e d t h e s y s t e m ( S e e f i g u r e 5 ) . P o s s i b l e i n t e r f e r e n c e b y r e s i d u a l c h l o r i n e i n t h e t a p w a t e r was c o n s i d e r e d , b u t v a l u e s w e r e k n o w n t o b e n e g l i g i b l e , t h e r e f o r e d e c h l o r i n a t i o n w a s n o t n e c e s s a r y . A d a n g e r o f b a c k f l o w w a s p r e v e n t e d b y a n a i r g a p i n b o t h t h e i n d i v i d u a l a n d f e e d r e s e r v o i r s . F i g u r e 5 . F e e d C o n f i g u r a t i o n s S e p t i c t a n k e f f l u e n t f e e d f o r e a c h o f t h e c h a n n e l s w a s p r o d u c e d u s i n g a s i m u l a t e d s e p t i c t a n k c o n s t r u c t e d f r o m a 2 0 0 l i t r e b a r r e l . Raw s e w a g e f r o m a n e a r b y s a n i t a r y s e w e r was f e d t o t h e b a r r e l o n c e a d a y . T h e c h a r a c t e r i s t i c s o f t h e s e p t i c t a n k e f f l u e n t a n d t h e r a w s e w a g e c a n b e s e e n I n T a b l e 2 . S E P T I C T A N K I N D I V I D U A L - k i - D O ? I N G ^ S I P H O N S ^ \ R E S E R V O I R "^f" - T - _ f ^ — -^ G R O U N D W A T E R C O N T R O L R A W S E W A G E G R O U N D W A T E R T A N K G R O U N D W A T E R F E E D 25 Table 2. Raw Sewage and S e p t i c Tank E f f l u e n t C h a r a c t e r i s t i c s Raw Sewage S e p t i c Tank E f f l u e n t High Mean Low No. High Mean Low No. Obs. Obs. TSS mg/L 508 381 275 10 340 286 240 10 COD mg/L 474 262 159 16 205 150 90 17 Ammonia 22.8 19 .9 15.0 11 26 .0 21.7 17.8 11 mg/L as N N i t r a t e + N i t r i t e 0.48 0.13 0.01 11 0.38 0.11 0.00 11 mg/L as N Orthophosphate 5.4 4.1 2.7 5 7.4 4.0 2.3 10 mg/L as P T o t a l C o l i f o r m s 110.0 27.5 6.7 26 36.0 16.2 6.0 26 Col/100 mL x 10 6 F e c a l C o l i f o r m s 6.2 3.3 1.7 27 4.5 2.1 0.1 26 Col/100 mL x 10 6 C o n v e n t i o n a l s e p t i c t a n k s a r e c o n s t r u c t e d t o m a i n t a i n a 2 t o 3 day h y d r a u l i c r e t e n t i o n t i m e , t h e r e f o r e a s i m i l a r r e t e n t i o n time was m a i n t a i n e d i n the s i m u l a t e d s e p t i c t a n k . T h i s was a c h i e v e d by d r a i n i n g a p p r o x i m a t e l y one t h i r d of the b a r r e l per day t o feed the c h a n n e l s . Each c h a n n e l was f e d from t h e s e p t i c tank v i a a s m a l l d o s i n g s i p h o n , and a g r a v e l i n l e t bed. I n d i v i d u a l d o s i n g s i p h o n s were used on the c h a n n e l s w i t h s a t u r a t e d f l o w o n l y , w h i l e one d o s i n g s i p h o n per 2 c h a n n e l s was used f o r the c h a n n e l s w i t h u n s a t u r a t e d v e r t i c a l s e c t i o n s . The d o s i n g s i p h o n s were m i n i t u r i z e d v e r s i o n s of c o n v e n t i o n a l d o s i n g s i p h o n s used i n s t a n d a r d s e p t i c tank a p p l i c a t i o n s . The s m a l l d o s i n g s i p h o n s were c o n s t r u c t e d u s i n g 1.5 l i t r e p l a s t i c c o n t a i n e r s t o s t o r e the c o n s t a n t f l o w from the s e p t i c b a r r e l between d i s c h a r g e s . A b e l l and s i p h o n c o n f i g u r a t i o n w i t h i n each c o n t a i n e r was c o n s t r u c t e d from a p l a s t i c cup and 13 m i l l i m e t r e copper p i p e (See f i g u r e 6 ) . The 26 c o n s t a n t f l o w i n t o e a c h s i p h o n w a s r e g u l a t e d w i t h a p l a s t i c n o z z l e , w h i c h a l l o w e d p a s s a g e o f t h e s o l i d s i n t h e s e p t i c t a n k e f f l u e n t . D I S C H A R G E L E V E L D I S C H A R G E V O L U M E = T N 0 V E R F L 0 W B E L L ^ 7 fx : D I S C H A R G E F i g u r e 6 . D o s i n g S i p h o n T h e s e p t i c t a n k e f f l u e n t w a s a l l o w e d t o e n t e r t h e s o i l s e c t i o n s t h r o u g h g r a v e l f i l l e d b o x e s a t t h e i n l e t e n d o f e a c h c h a n n e l . T h e g r a v e l b o x e s w e r e 30 c e n t i m e t r e s s q u a r e , f i l l e d t o a d e p t h o f 15 c e n t i m e t r e s . T h i s g r a v e l a l l o w e d a n e v e n d i s t r i b u t i o n o f t h e s e p t i c t a n k e f f l u e n t o v e r a 90 s q u a r e c e n t i m e t r e a r e a (1 s q u a r e f o o t ) o n d i s c h a r g e o f t h e d o s i n g s i p h o n . T h e l o a d i n g r a t e s o f t h e s e p t i c t a n k e f f l u e n t i n t h e c h a n n e l s w i t h s e c t i o n s o f u n s a t u r a t e d s o i l w e r e h i g h e r t h a n t h e r e c o m m e n d e d l o a d i n g b a s e d o n t h e p e r c o l a t i o n r a t e ( S e e t a b l e 3 ) . S i n c e t h e r o l e o f t h e u n s a t u r a t e d a n d s a t u r a t e d z o n e s w e r e t h e p o i n t s i n q u e s t i o n , t h e h i g h e r l o a d i n g r a t e s c o u l d a m p l i f y t h e i r r o l e s i n t h e d i s p o s a l o f s e p t i c t a n k e f f l u e n t . I n d e a l i n g w i t h t h e t w o - z o n e s y s t e m s i n p a r t i c u l a r ( u n s a t u r a t e d f l o w f o l l o w e d b y s a t u r a t e d f l o w ) , t h e a d d i t i o n a l l o a d i n g c o u l d p r o v i d e i n f o r m a t i o n n o t d i s c e r n i b l e a t l o w e r l o a d i n g r a t e s . T h e l o a d i n g r a t e s i n t h e 27 g u i d e l i n e s t h e m s e l v e s a r e n o t a r b i t r a r y , b u t t h e y do o n l y c o n s i d e r t h e d i s p o s a l o f a l i q u i d and n o t t h e t r e a t m e n t o f t h e e f f l u e n t by t h e s o i l . The g u i d e l i n e l o a d i n g r a t e s a r e , t h e r e f o r e , no t an o v e r r i d i n g i s s u e when i n v e s t i g a t i n g t h e r o l e s o f t h e s a t u r a t e d and u n s a t u r a t e d z o n e s w i t h r e s p e c t t o e f f l u e n t q u a l i t y . The h i g h e r l o a d i n g r a t e s w o u l d a l l o w t h e c o n c l u s i o n s t o be c o n s e r v a t i v e when r e l a t i n g back t o t h e g u i d e l i n e s . The c h a n n e l s e c t i o n s w h i c h had no u n s a t u r a t e d f l o w and c o n s e q u e n t l y d i d n o t have t h e t w o - z o n e s y s t e m s were l o a d e d a t l o w e r r a t e s . The r e d u c e d l o a d i n g r a t e s were deemed n e c e s s a r y t o p r o p e r l y o b s e r v e t h e r o l e o f t h e s a t u r a t e d z o n e by i t s e l f . The h i g h e r l o a d i n g r a t e s may have masked t h e t r e a t m e n t c a p a b i l i t e s o f t h e s a t u r a t e d z o n e . A l l f l o w s y s t e m s w i t h i n t h e e x p e r i m e n t s were g r a v i t y f e d , w h i c h f r e e d t h e e x p e r i m e n t s f r o m pump m a i n t e n a n c e p r o b l e m s . A t t h e same t i m e , p r o b l e m s i n f l o w c o n t r o l and b a l a n c i n g were i n t r o d u c e d by n o t u s i n g pumps, a n d t h e r e f o r e f r e q u e n t f l o w measu rement s were n e c e s s a r y t o r e c o r d t h e s y s t e m o p e r a t i o n . T h i s l a c k o f u n i f o r m i t y c a n be s e e n i n T a b l e 3 w i t h r e g a r d t o t h e h o r i z o n t a l i n p u t f l o w i n t o t h e c h a n n e l s . A c o n s i s t e n t f l o w became i m p o s s i b l e t o m a i n t a i n , t h e r e f o r e a c o n s i s t e n t f l o w m o n i t o r i n g s y s t e m was t h e a l t e r n a t i v e . T h e s e d i f f e r e n c e s i n f l o w r e q u i r e d t h e c o n s i d e r a t i o n o f d i f f e r e n c e s i n d i l u t i o n i n t h e d i s c u s s i o n o f t h e r e s u l t s . 28 Table 3. Loading Rates and Channel Flow S o i l Type Unsaturated Septic Tank Allowable Hz. Zone Loading Loading Based Input on Percolation Flow Rate cm/day(L/day) cm/day L/day loamy-sand 0.91 14.2 (13.2) 5.0 66.2 loamy-sand 0.46 18.1 (16.8) 5.0 57.6 loamy-sand 0.00 12.9 (12.0) 5.0 83.5 sand 0.91 39.4 (36.6) 13.5 85.0 sand 0.46 25.2 (23.4) 13.5 112.3 sand 0.00 10.8 (11.5) 13.5 116.6 2.4 Sample Coll e c t i o n ,Storage, and Analysis Samples were collected from 3 sample points located in the saturated s o i l sections of the channels. The samples were analysed for t o t a l and fecal coliforms, chemical oxygen demand, ammonia nitrogen, n i t r a t e and n i t r i t e nitrogen and orthophosphate. Chemical oxygen demand (COD) samples were i n i t i a l l y collected on a twice weekly basis, but this was completely discontinued halfway through the study to accommodate the nutrient analysis. Coliform samples were coll e c t e d on a twice weekly basis, while nutrient samples were coll e c t e d on a weekly basis. The sampling procedure was worked into a 7 day schedule which allowed sampling, analysis, and cleanup. The sample schedule for coliforms and chemical oxygen demand was as follows: Day 1. Sample 100 mL for coliform and COD analysis 2. Run coliform tests 3. Run COD test and count coliforms 4. Sample 100 mL for coliform and COD analysis 5. Run coliform tests 6. Run COD test and count coliforms 7. Cleanup 29 The sample schedule f o r c o l i f o r m s and n u t r i e n t s was as f o l l o w s : Day 1. Sample 100 mL f o r c o l i f o r m and n i t r o g e n a n a l y s i s 2. Run c o l i f o r m t e s t s and ammonia a n a l y s i s 3. Count c o l i f o r m and run n i t r a t e - n i t r i t e a n a l y s i s 4. Sample 100 mL f o r c o l i f o r m and orthophosphate a n a l y s i s 5. Run c o l i f o r m t e s t s and orthophosphate 6. Count c o l i f o r m s and cleanup 7. Rest Fresh samples were c o l l e c t e d from the sample columns u t i l i z i n g a b i l g e pump to d r a i n the column and a l l o w a f r e s h sample to enter. A s t e r i l e sample tube was then i n s e r t e d i n t o the sample column and 100 mL of sample was drawn out with two s t e r i l i z e d 50 mL s y r i n g e s . Between samples the b i l g e pump was r i n s e d with f r e s h tap water. The samples were analysed f o r t o t a l and f e c a l c o l i f o r m s using the membrane f i l t r a t i o n technique. The t o t a l c o l i f o r m t e s t used an M-Endo medium with i n c u b a t i o n f o r 24 hours a t 35 degrees c e n t i g r a d e . F e c a l c o l i f o r m s were t e s t e d u s i n g a M-FC broth and i n c u b a t i o n f o r 24 hours a t 44.5 degrees c e n t i g r a d e (See Standard Methods f o r Examination of Water and Wastewater (1980)). Samples taken f o r ammonia a n a l y s i s were preserved with concentrated s u l p h u r i c a c i d and l a t e r a nalysed by the automated phenate method (See Standard Methods f o r Examination of Water and Wastewater (1980)). Samples f o r n i t r a t e plus n i t r i t e a n a l y s i s were preserved u s i n g a s o l u t i o n of phenyl mercuric a c e t a t e and acetone, and l a t e r analysed by the automated cadmium r e d u c t i o n method (See Standard Methods f o r Examination of Water and Wastewater (1980)). Orthophosphate samples were analysed 30 immediately a f t e r sampling using the stannous c h l o r i d e method (See Standard Methods f o r Examination of Water and Wastewater (1980)). The d e t e r m i n a t i o n of chemical oxygen demand was c a r r i e d out using the dichrornate method (See Standard Methods f o r Examination of Water and Wastewater (1980)). 31 3. RESULTS 3.1 O v e r a l l E x p e r i m e n t a l Summary Through the use of a p i l o t s c a l e experiment s i x d i f f e r e n t c o n d i t i o n s of u n s a t u r a t e d and s a t u r a t e d f l o w of s e p t i c tank e f f l u e n t were i n v e s t i g a t e d . Three v a r i a t i o n s i n d e pth of u n s a t u r a t e d f l o w , a l o n g w i t h 2 v a r i a t i o n s i n s o i l type produced the 6 d i f f e r e n t c o n d i t i o n s (See f i g u r e 4 ) . D u r i n g the e x p e r i m e n t a n a l y s e s were conducted f o r t o t a l and f e c a l c o l i f o r m s , ammonia, n i t r a t e , n i t r i t e , orthophosphate and COD. A d d i t i o n a l d a t a c o l l e c t e d b e f o r e and d u r i n g the o p e r a t i o n of the p i l o t s c a l e experiment i n c l u d e d p e r c o l a t i o n v a l u e s f o r the two s o i l s , h y d r a u l i c l o a d i n g of s e p t i c tank e f f l u e n t on s o i l s , and water f l o w s w i t h i n s a t u r a t e d s e c t i o n s of the e x p e r i m e n t a l c o n f i g u r a t i o n s . The common l i n k between each of the 6 d i f f e r e n t e x p e r i m e n t a l c o n d i t i o n s was the s e c t i o n of s a t u r a t e d s o i l . The a n a l y s i s of samples t a k e n a t s p e c i f i c p o i n t s a l o n g t h e s e s a t u r a t e d s e c t i o n s was the main s o u r c e of d a t a f o r the r e s u l t s . The v a r i a t i o n i n depth of u n s a t u r a t e d s o i l (0.00 metres, 0.46 metres, and 0.91 metres) a t the i n l e t of the s e c t i o n of s a t u r a t e d s o i l , i n a d d i t i o n t o t h e two s o i l t y p e s , were the two main v a r i a b l e s i n the s t u d y . 32 3.2 C o l i f o r m s The c o l i f o r m b a c t e r i a t e s t i n g r e s u l t s a r e e x p r e s s e d w i t h 2 d i f f e r e n t g r a p h i c p r e s e n t a t i o n s . The f i r s t p r e s e n t a t i o n i s the comparison of c o l i f o r m r e d u c t i o n based on the d i f f e r e n t u n s a t u r a t e d depths of s o i l , and the d i f f e r e n t types of s o i l . T h i s r e s u l t uses a l l the the c o l i f o r m d a t a c o l l e c t e d a l o n g the s a t u r a t e d f l o w s e c t i o n ; f i g u r e s 7 t h r o u g h 10 show the s e r e s u l t s . The second p r e s e n t a t i o n i s the comparison of c o l i f o r m r e d u c t i o n i n the s a t u r a t e d s o i l s e c t i o n , as a f u n c t i o n of d i s t a n c e from i n l e t of the s a t u r a t e d s e c t i o n . T h i s r e s u l t uses the d a t a c o l l e c t e d a t the s p e c i f i c s a m p l i n g p o i n t s i n the c h a n n e l s w i t h no zone of u n s a t u r a t e d s o i l . F i g u r e s 11 t h r o u g h 13 p r e s e n t t o t a l c o l i f o r m s f o r the two s o i l t y p e s as a f u n c t i o n of d i s t a n c e from the i n l e t . F i g u r e s 14 t h r o u g h 16 e x p r e s s the same r e s u l t f o r f e c a l c o l i f o r m s . The. graphs a r e e x p r e s s e d i n c o l i f o r m s per 100 mL v e r s u s p e r c e n t of t o t a l samples l e s s than or e q u a l t o . T h i s p r e s e n t a t i o n not o n l y g i v e s a p e r c e n t of c o l i f o r m s removed w i t h i n each c h a n n e l , but a l s o the range o f c o l i f o r m v a l u e s w i t h i n each c h a n n e l . I n f l u e n t c o l i f o r m c o u n t s were i n the range of 10 to 20 m i l l i o n c o l i f o r m s per 100 mL f o r t o t a l c o l i f o r m s and 2 t o 4 m i l l i o n c o l i f o r m s per 100 mL f o r f e c a l c o l i f o r m s . F i g u r e s 7 through 10 show the r e l a t i v e performance of the depths of u n s a t u r a t e d s o i l ; t he c l o s e r a l i n e i s t o the t o p of the p l o t , the b e t t e r i t s c o l i f o r m removal e f f i c i e n c y . N i n e t y - o n e c e n t i m e t r e s of u n s a t u r a t e d s o i l a ppears t o be s u p e r i o r t o 46 c e n t i m e t r e s of u n s a t u r a t e d s o i l w i t h i n the i n d i v i d u a l s o i l t y p e s ( t o t a l c o l i f o r m s and f e c a l c o l i f o r m s ) . 33 100 80 < Z D O UJ CC o < X 60 f— CO CO UJ 40 U CC UI 20 i i i i i i i i Legend • LOAMY-SAND I SAND i i r—i—I I I i 10 100 TOTAL COLIFORMS / 100 mL 1000 F i g u r e 7 . T o t a l C o l i f o r m s f o r 0 . 4 6 m e t r e s o f U n s a t u r a t e d S o i l O < = > O UJ cc o 100 80 < X 60 CO CO O CC 4 0 -U l 20 -10 Legend • LOAMY-SAND n SAND i i i i i i 100 I I I 1000 TOTAL COLIFORMS / 100 mL F i g u r e 8 . T o t a l C o l i f o r m s f o r 0 . 9 1 m e t r e s o f U n s a t u r a t e d S o i l 34 < Z> O Ld LY. O CO CO Ld O 100 80 -< X 60 40 -UJ 20 CL Legend • LOAMY-SAND • SAND i i i i i 10 100 FECAL COLIFORMS / 100 m L i i i i i i i 1000 F i g u r e 9 . F e c a l C o l i f o r m s f o r 0 . 4 6 m e t r e s o f U n s a t u r a t e d S o i l 100 80 < O Ld OH o < X 60 I— CO CO Ld 40 O Ld 20 H o-t i i i i i i i Legend • LOAMY-SAND SAND 10 100 FECAL COLIFORMS / 100 m L i i i 11 1000 F i g u r e 1 0 . F e c a l C o l i f o r m s f o r 0 . 9 1 m e t r e s o f U n s a t u r a t e d S o i l 35 < o U J cc O z < X I— V I UI z UI o 10000 100 1000 TOTAL COLIFORMS / 100 mL. F i g u r e 1 1 . T o t a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 0 . 6 1 m e t r e s F r o m I n l e t F i g u r e 1 2 , F i g u r e 1 3 < o UJ cn O z < X t— (/I IO z U I o CC 1 10 100 1000 TOTAL COLIFORMS / 100 mL. . T o t a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 1 . 6 7 m e t r e s F r o m I n l e t < s O z < X I— </l ui o CC 10 100 TOTAL COLIFORMS / 100 mL. 1000 T o t a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 2 . 7 4 m e t r e s F r o m I n l e t 36 F i g u r e 14 F i g u r e 1 5 , F i g u r e 16 < Z3 O U l cc o z < X I— to 1/1 o QC U l a. 1 10 100 1000 10000 FECAL COLIFORMS / 100 mL. F e c a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 0 . 6 1 m e t r e s F r o m I n l e t < ZD s cc o z < I I— to V ) U l o 10 100 1000-FECAL COLIFORMS / 100 mL. F e c a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 1 . 6 7 m e t r e s F r o m I n l e t < ZZ) 2 o z < X 1— to to u 1000 10 100 FECAL COLIFORMS / 100 m L F e c a l C o l i f o r m s f o r C o m p l e t e l y S a t u r a t e d S o i l , 2 . 7 4 m e t r e s F r o m I n l e t 37 The h o r i z o n t a l i n p u t f l o w s i n the s a t u r a t e d zone v a r y by s i g n i f i c a n t amounts (See t a b l e 3 ) . A c o n s i s t e n t f l o w became i m p o s s i b l e t o m a i n t a i n , t h e r e f o r e a c o n s i s t e n t f l o w m o n i t o r i n g system was the a l t e r n a t i v e . F i g u r e s 7 through 16 were not a d j u s t e d f o r d i f f e r e n c e s i n d i l u t i o n caused by the f l o w v a r i a t i o n s . The v a r i a t i o n s i n f l o w f o r f i g u r e s 7 through 16 would s h i f t s e v e r a l of the c u r v e s t o the r i g h t , but t h i s would have no e f f e c t on the rank of the c u r v e s . An e x a m i n a t i o n of the mean t o t a l and f e c a l c o l i f o r m c o u n t s s u g g e s t s l i t t l e d i f f e r e n c e between 0.91 metres and 0.46 metres of u n s a t u r a t e d s o i l (See t a b l e 4 ) . Table 4. I n f l u e n c e of U n s a t u r a t e d Flow on C o l i f o r m s S o i l Type U n s a t u r a t e d Mean S t d . Mean S t d . Zone T o t a l Dev. F e c a l Dev. metres C o l . C o l . /lOOmL /lOOmL loamy-sand 0.91 15 36 <1 5 loamy-sand 0.46 27 46 10 44 sand 0.91 31 54 1 9 sand 0.46 35 77 3 22 A s t a t i s t i c a l comparison of t h e means (See appendix, p a r t 1) a l s o s u g g e s t s t h a t t h e r e i s no d i f f e r e n c e between these two depths of u n s a t u r a t e d s o i l . The s t a t i s t i c a l c omparison i s v a l i d , but may be m i s l e a d i n g i n c o n s i d e r a t i o n of the wide range of c o l i f o r m v a l u e s , as i n d i c a t e d by the s t a n d a r d d e v i a t i o n s of t h e v a l u e s i n t a b l e 4. F i g u r e s 7 t h r o u g h 10 a l s o show the d i f f e r e n c e i n s o i l performance. The l i n e showing t h e p e r c e n t l e s s than or e q u a l t o f o r sand l i e s above the l i n e f o r the loamy-sand i n 3 of the 4 38 graphs ( F i g u r e s 7, 8, and 9 ) . Only i n f i g u r e 10 does the loamy-sand l i e s l i g h t l y above the sand. A comparison of the mean v a l u e s s u g g e s t s t h a t loamy-sand may be s u p e r i o r , but a s t a t i s t i c a l c omparison of the means s u g g e s t s no d i f f e r e n c e between the s o i l t y p e s . T h i s may a g a i n be m i s l e a d i n g because of the l a r g e range of v a l u e s . I f the degree of r e t e n t i o n of b a c t e r i a i s i n v e r s e l y p r o p o r t i o n a l t o p a r t i c l e s i z e , as suggested by Hagedorn (1984), some o t h e r f a c t o r may be r e s p o n s i b l e f o r the s i m i l a r i t y i n c o l i f o r m r e d u c t i o n between the sand and t h e loamy-sand (See t a b l e 4 ) . An e x a m i n a t i o n of the g r a i n s i z e a n a l y s i s c l e a r l y shows a t l e a s t 15 p e r c e n t of the loamy-sand t o be f i n e r t han th e sand, a l t h o u g h 30 p e r c e n t of the loamy-sand i s l a r g e r than the sand. The l a r g e r s i z e d m a t e r i a l may l e s s e n t h e removal e f f i c i e n c y of the s m a l l e r s i z e d m a t e r i a l . F i g u r e s 11 t h r o u g h 16 show the e f f e c t of d i s t a n c e on r e d u c t i o n of c o l i f o r m s under c o n d i t i o n s of s a t u r a t e d f l o w . F i g u r e s 11 and 13 show p e r c e n t removal of t o t a l c o l i f o r m s f o r two of the s a m p l i n g p o i n t s w i t h i n the c h a n n e l s . F i g u r e 11 shows the p e r c e n t removal of t o t a l c o l i f o r m s a t a d i s t a n c e of 0.61 metres from the i n l e t s e c t i o n , w h i l e f i g u r e 13 shows the p e r c e n t removal of t o t a l c o l i f o r m s a t a d i s t a n c e o f 2.74 metres from the i n l e t s e c t i o n . At a d i s t a n c e of 0.61 metres from the i n l e t i n the sand,100 p e r c e n t of the t o t a l c o l i f o r m s l i e below 10,000 per 100 mL. In c o n t r a s t , a t a d i s t a n c e of 2.74 metres from the i n l e t i n the sand, 100 p e r c e n t of the t o t a l c o l i f o r m s l i e below 1000 per 100 mL., i n d i c a t i n g a s u b s t a n t i a l r e d u c t i o n In c o l i f o r m 39 numbers a l o n g the s a t u r a t e d f l o w c h a n n e l s . The c u r v e s f o r f e c a l c o l i f o r m s ( F i g u r e s 14 and 16) show the same r e l a t i v e r e s u l t s . An e x a m i n a t i o n of the mean t o t a l and f e c a l c o l i f o r m c o u n t s s u g g e s t s a s i m i l a r c o n c l u s i o n (See t a b l e 5 ) . Table 5. I n f l u e n c e of S a t u r a t e d Flow on C o l i f o r m s S o i l Type D i s t a n c e From Mean S t d . Mean S t d . I n l e t T o t a l Dev. F e c a l Dev. metres C o l . C o l . VlOOmL /lOOmL loamy-sand 0.61 125 150 113 175 loamy-sand 1.67 29 49 40 50 loamy-sand 2.74 160 209 89 90 sand 0.61 2089 3007 1822 2773 sand 1.67 2 4 2 6 sand 2.74 72 190 35 108 A comparison of the s o i l m a t e r i a l s shows t h a t a t a d i s t a n c e of 0.61 metres from the i n l e t , the p e r c e n t removal of t o t a l c o l i f o r m s w i t h i n the loamy-sand l i e s above t h e p e r c e n t removal of t o t a l c o l i f o r m s f o r the sand, i n d i c a t i n g g r e a t e r c o l i f o r m s numbers i n the sand. T h i s s u g g e s t s t h a t the loamy-sand has g r e a t l y reduced c o l i f o r m s numbers w i t h i n the f i r s t 0.61 metres of t r a v e l . The mean v a l u e s of t o t a l and f e c a l c o l i f o r m s a t 0.61 metres i n the sand are a l s o much g r e a t e r than the c o l i f o r m numbers i n the loamy-sand. A c o n f u s i n g p o i n t i s the dr o p i n c o l i f o r m numbers a t 1.67 metres and the r i s e a g a i n a t 2.74 metres. T h i s may be the r e s u l t of reg r o w t h a t the o u t l e t of the c h a n n e l s . 40 3.3 Chemical Oxygen Demand A l l but 4 of the 210 COD samples t a k e n from the c h a n n e l s were l e s s than 60 mg/L and s e v e n t y - f i v e p e r c e n t of these v a l u e s were l e s s than 25 mg/L (See t a b l e 6 ) . Table 6. E f f l u e n t COD S o i l Type U n s a t u r a t e d COD (mg/L) S t d . No. of Zone Mean Dev. Obs. loamy-sand 0.91 loamy-sand 0.46 loamy-sand 0.00 sand 0.91 sand 0.46 sand 0.00 24 29 52 36 32 50 39 27 22 12 10 44 11 9 46 15 13 22 I n f l u e n t COD ranged from 90 t o 205 mg/L, w i t h an average v a l u e of 150 mg/L . COD samples c o l l e c t e d from the c h a n n e l s w i t h the loamy-sand c o n t a i n e d s u b s t a n t i a l amounts of suspended m a t e r i a l i n s p i t e of the use of s c r e e n s i n the sample columns. In o r d e r t o m i n i m i z e the e f f e c t of o r g a n i c s w i t h i n t h i s suspended m a t e r i a l , the p a r t i c l e s were a l l o w e d t o s e t t l e out b e f o r e p e r f o r m i n g the COD a n a l y s i s . 3.4 N u t r i e n t s The r e s u l t s of the n u t r i e n t s a m p l i n g and t e s t i n g a r e p r e s e n t e d a c c o r d i n g t o the two i n f l u e n c i n g f a c t o r s e x p r e s s e d i n the o b j e c t i v e s : the u n s a t u r a t e d zone and the s a t u r a t e d zone. In s a m p l i n g t o t e s t the i n f l u e n c e of the d e p t h of u n s a t u r a t e d s o i l , the v a l u e s were r e c o r d e d a t the p o i n t i m m e d i a t e l y a d j a c e n t t o the u n s a t u r a t e d s e c t i o n . The v a r i a t i o n of c o n c e n t r a t i o n of n u t r i e n t s w i t h d i s t a n c e under s a t u r a t e d f l o w c o n d i t i o n s were 41 not s t a t i s t i c a l l y d i f f e r e n t i n those c h a n n e l s which had a d j a c e n t s e c t i o n s of u n s a t u r a t e d f l o w . The i n f l u e n c e of s a t u r a t e d f l o w on n u t r i e n t c o n c e n t r a t i o n was t e s t e d by s a m p l i n g a t d i f f e r e n t d i s t a n c e s i n the c h a n n e l s w i t h s a t u r a t e d f l o w o n l y . The d i f f e r e n t d i l u t i o n s r e s u l t i n g from the d i f f e r e n t groundwater f l o w s become c r i t i c a l when c o n s i d e r i n g the n u t r i e n t s . To compare the c o n c e n t r a t i o n s i n the d i f f e r e n t c h a n n e l s , an adjustment f a c t o r u s i n g one p a r t i c u l a r f l o w as a benchmark was used (See t a b l e 7 ) . Tab l e 7. R e l a t i v e Adjustment F a c t o r s f o r D i l u t i o n S o i l Type U n s a t u r a t e d H o r i z o n t a l R e l a t i v e Zone Input Flow D i l u t i o n metres L/day F a c t o r loamy-sand 0.91 66.2 1.1 loamy-sand 0.46 57.6 1.0 loamy-sand 0.00 83.5 1.4 sand 0.91 85.0 1.5 sand 0.46 112.3 1.9 sand 0.00 116.6 2.0 The benchmark f o r the d i l u t i o n f a c t o r was the lo w e s t f l o w of 57.6 l i t r e s / d a y f o r the loamy-sand w i t h 0.46 metres of u n s a t u r a t e d s o i l . 3.4.1 Ammonia P r e s e n t e d i n t a b l e 8 a r e the ammonia r e s u l t s as i n f l u e n c e d by the d e p t h of u n s a t u r a t e d s o i l . A s l i g h t i n c r e a s e i n ammonia c o n c e n t r a t i o n i n the loamy-sand as a f u n c t i o n of decrease i n depth of u n s a t u r a t e d s o i l i s not s t a t i s t i c a l l y s i g n i f i c a n t (See 42 appendix, part 1). The sand, on the other hand, shows a g r e a t r i s e i n ammonia c o n c e n t r a t i o n as the unsaturated zone decreased from 0.46 metres to 0.00 metres, while remaining almost constant between 0.91 and 0.46 metres of unsaturated s o i l . T h i s r i s e from 0.04 mg/L to 3.56 mg/L i s s t a t i s t i c a l l y s i g n i f i c a n t . Table 8. Inf l u e n c e of Unsaturated Flow on Ammonia S o i l Type Unsaturated Ammonia Zone mg/L as N metres Mean loamy-sand 0.91 0.21 loamy-sand 0.46 0.36 loamy-sand 0.00 0.41 sand 0.91 0.04 sand 0.46 0.02 sand 0.00 1.78 Std. No. of Mean Adjusted Dev. Obs. f o r R e l a t i v e D i l u t i o n 0.09 11 0.37 0.10 11 0.36 0.22 11 0.57 0.02 11 0.06 0.01 11 0.04 0.59 11 3.56 Presented i n t a b l e 9 are the ammonia r e s u l t s as i n f l u e n c e d by the d i s t a n c e of flow under s a t u r a t e d flow c o n d i t i o n s . These r e s u l t s can a l s o be seen i n f i g u r e s 17 and 18 which show the time v a r i a t i o n i n a d d i t i o n to channel p o s i t i o n f o r the systems with s a t u r a t e d flow o n l y . The apparent decrease i n c o n c e n t r a t i o n i n the loamy-sand i s not s t a t i s t i c a l l y s i g n i f i c a n t . The decrease i n c o n c e n t r a t i o n of ammonia i n the sand from 1.78 mg/L a t 0.61 metres to 0.21 mg/L a t 1.67 metres i s s t a t i s t i c a l l y s i g n i f i c a n t , while the remaining decrease from 0.21 mg/L a t 1.67 metres t o 0.10 mg/L a t 2.74 metres i s not. 43 T a b l e 9 . I n f l u e n c e o f S a t u r a t e d P l o w on Ammonia S o i l Type D i s t a n c e F rom I n l e t m e t r e s Mean Ammonia S t d . C o n e . Dev . mg/L No. o f Ob s . l o a m y - s a n d l o a m y - s a n d l o a m y - s a n d s and 0.61 1.67 2.74 0.61 1.67 2.74 0 .41 0 .34 0 .32 1.78 0 .21 0 .09 0 . 2 2 0.11 0 .11 0 .59 0 .13 0 .09 11 11 11 11 11 11 s a n d s and The t e m p o r a l v a r i a t i o n o f ammonia a s p r e s e n t e d i n f i g u r e s 17 a n d 1 8 , i s s u m m a r i z e d f o r a l l t h e c h a n n e l s In f i g u r e s 19 and 2 0 . A g e n e r a l i n c r e a s e i n ammonia c o n c e n t r a t i o n w i t h t i m e c a n be n o t e d i n a l l t h e c h a n n e l s e x c e p t t h e s a n d f i l l e d c h a n n e l s w h i c h have d e p t h s o f u n s a t u r a t e d s o i l . 44 • 0.61 m frcm i n l e t U.U "1 1 1 1 1 1 1 1 1 100 110 120 130 140 150 160 170 180 DAY F i g u r e 1 7 . A m m o n i a f o r L o a m y - S a n d F i l l e d C h a n n e l , 0 . 0 0 m e t r e s U n s a t u r a t e d S o i l F i g u r e 1 8 . A m m o n i a f o r S a n d F i l l e d C h a n n e l , 0 . 0 0 m e t r e s U n s a t u r a t e d S o i l 45 E 0.7-1 0.6 H 0.5 < 0.4 O z O O < o 0.3 0.2 H o.H 0.0-Legend A 0.91 m unsaturated X 0 . 4 6 m unsaturated • 0 .03 m unsaturated 100 110 120 130 140 DAY 150 160 170 180 F i g u r e 1 9 . A m m o n i a f o r L o a m y - S a n d F i l l e d C h a n n e l s 0.8 < 0.6 A CJ Z o o < o 0.4 0.2 JB • E T Legend A 0.91 m unsaturated X 0 . 4 6 m unsaturated • 0 .00 m unsaturated, 1 1 1 1 i — — 100 110 120 130 140 150 160 170 180 DAY F i g u r e 2 0 . A m m o n i a f o r S a n d F i l l e d C h a n n e l s 46 3.4.2 N i t r a t e The measurement of n i t r a t e i n a l l of the samples i n c l u d e d both n i t r a t e and n i t r i t e . S e v e r a l t i m e s d u r i n g c o u r s e of the s t u d y measurements of n i t r i t e a l o n e were made on the samples, which r e v e a l e d an average c o n c e n t r a t i o n o f l e s s than 0.02 mg/L. Based on the s e measurements, t h e n i t r i t e c o n c e n t r a t i o n was c o n s i d e r e d n e g l i g i b l e . I n f l u e n t n i t r a t e p l u s n i t r i t e c o n c e n t r a t i o n s were a l s o measured, and averaged 0.11 mg/L, w i t h the n i t r i t e c o n c e n t r a t i o n l e s s than 0.07 mg/L. Table 10. I n f l u e n c e of U n s a t u r a t e d F l o w on N i t r a t e S o i l Type U n s a t u r a t e d N i t r a t e S t d . No. of Mean A d j u s t e d Zone mg/L as N Dev. Obs . f o r R e l a t i v e metres Mean D i l u t i o n loamy-sand 0.91 0.32 0.15 11 0.35 loamy-sand 0.46 1.50 1.28 11 1.50 loamy-sand 0.00 0.23 0.15 11 0.32 sand 0.91 7.23 1.44 11 10.85 sand 0.46 2.96 0.56 11 5.62 sand 0.00 0.51 0.16 11 1.02 The n i t r a t e c o n c e n t r a t i o n i n the loamy-sand, as i n f l u e n c e d by the depth of u n s a t u r a t e d f l o w ( T a b l e 1 0 ) , shows a sudden i n c r e a s e from 0.91 metres t o 0.46 metres of u n s a t u r a t e d s o i l . T h i s i n c r e a s e i s not s t a t i s t i c a l l y s i g n i f i c a n t based on the d a t a c o l l e c t e d , but i t does r a i s e a q u e s t i o n o f some r e a c t i o n t a k i n g p l a c e w i t h i n the 0.91 metre u n s a t u r a t e d s e c t i o n of the loamy-sand. D e n i t r i f i c a t i o n w i t h i n the 0.91 metre s e c t i o n i s p o s s i b l e i f an a n a e r o b i c c o n d i t i o n was m a i n t a i n e d i n t h i s t i g h t s o i l . The sand shows a s t a t i s t i c a l l y s i g n i f i c a n t i n c r e a s e i n n i t r a t e c o n c e n t r a t i o n w i t h d i s t a n c e i n the u n s a t u r a t e d zone. 47 The mean v a l u e s i n t he s a t u r a t e d z o n e show no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e b a s e d on d i s t a n c e o f f l o w o r s o i l m a t e r i a l (See t a b l e 1 1 ) . T a b l e 1 1 . I n f l u e n c e o f S a t u r a t e d F l o w on N i t r a t e S o i l T y p e D i s t a n c e F r o m Mean N i t r a t e S t d . No . o f I n l e t C o n e . Dev . O b s . m e t r e s mg/L l o a m y - s a n d 0.61 0 .23 0 . 1 5 11 l o a m y - s a n d 1.67 0 .19 0 .09 11 l o a m y - s a n d 2.74 0 .16 0 . 0 7 11 s a n d 0.61 0 .51 0 .16 11 s a n d 1.67 0 .58 0 . 1 6 11 s a n d 2.74 0 .59 0 .21 11 The t e m p o r a l v a r i a t i o n o f n i t r a t e i s p r e s e n t e d i n f i g u r e s 21 and 2 2 . The c o n c e n t r a t i o n o f n i t r a t e w i t h t i m e was r e a s o n a b l y c o n s t a n t e x c e p t f o r t h e l o amy s a n d f i l l e d c h a n n e l w i t h 0 .46 m e t r e s o f u n s a t u r a t e d s o i l . F i g u r e 21 shows t h e d r o p i n c o n c e n t r a t i o n n e a r d a y 1 4 0 , b a s e d on a v e r a g e c h a n n e l c o n c e n t r a t i o n s . T h i s d e c r e a s e was i s o l a t e d i n f i g u r e 2 3 , w h i c h shows n i t r a t e c o n c e n t r a t i o n s f o r 0 .46 m e t r e s o f u n s a t u r a t e d l o a m y - s a n d o n l y . The s u d d e n d e c r e a s e a p p e a r s t o be c a u s e d b y t h e u n s a t u r a t e d s o i l a t t h e head o f t h e c h a n n e l and n o t t h e s a t u r a t e d f l o w . T h i s c h a n g e p o i n t s t o e i t h e r a d e c r e a s e i n t h e n i t r i f i c a t i o n i n t h e s o i l o r a n i n c r e a s e i n t h e d e n i t r i f i c a t i o n i n t h e s o i l . In e i t h e r c a s e a d e c r e a s e i n n i t r a t e c o n c e n t r a t i o n w o u l d o c c u r . 48 1.5-, D A Y F i g u r e 21. N i t r a t e f o r L o a m y - S a n d F i l l e d C h a n n e l s 8-1 1 1 1 1 1 1 1— 100 110 120 130 140 150 160 170 D A Y F i g u r e 22. N i t r a t e f o r S a n d F i l l e d C h a n n e l s 49 3.5 cn £ o t— z UJ o z o o UJ 2.5 1.5-0.5 S? Legend A z.74 m frcm inlet X 1.67 m fron inlet O 0.61 in fran inlet "I 1 1 1 1 100 110 120 130 140 150 DAY 180 F i g u r e 2 3 . N i t r a t e f o r L o a m y - S a n d F i l l e d C h a n n e l , 0 . 4 6 m e t r e s o f U n s a t u r a t e d S o i l 3 . 4 . 3 O r t h o p h o s p h a t e P r e s e n t e d i n t a b l e 12 a r e t h e o r t h o p h o s p h a t e r e s u l t s a s i n f l u e n c e d b y t h e d e p t h o f u n s a t u r a t e d s o i l . T h e v a r i a t i o n s i n c o n c e n t r a t i o n s b e t w e e n t h e c h a n n e l s a r e n o t s t a t i s t i c a l l y s i g n i f i c a n t . T h e n o t a b l e i n c r e a s e i n o r t h o p h o s p h a t e i n 0 . 4 6 m e t r e s o f u n s a t u r a t e d s a n d , a l t h o u g h n o t s i g n i f i c a n t b a s e d o n t h e d a t a , s u g g e s t s a n u n u s u a l c h a n g e i n t h e o r t h o p h o s p h a t e c o n c e n t r a t i o n . 50 Table 12. I n f l u e n c e of U n s a t u r a t e d Flow on Orthophosphate S o i l Type U n s a t u r a t e d Orthophosphate S t d . No. of Mean A d j u s t e d Zone mg/L as P Dev. Obs. f o r R e l a t i v e metres Mean D i l u t i o n loamy-sand 0.91 0.017 0.008 9 0.019 loamy-sand 0.46 0.023 0.008 9 0.023 loamy-sand 0.00 0.024 0.012 10 0.034 sand 0.91 0.011 0.005 8 0.017 sand 0.46 0.046 0.037 8 0.087 sand 0.00 0.016 0.008 9 0.032 P r e s e n t e d i n t a b l e 13 a r e the orthophosphate r e s u l t s as i n f l u e n c e d by the d i s t a n c e of f l o w under s a t u r a t e d f l o w c o n d i t i o n s . Table 13. I n f l u e n c e of S a t u r a t e d F l o w on Orthophosphate S o i l Type D i s t a n c e From Mean S t d . No. of Obs. I n l e t Orthophosphate Dev. metres Cone. mg/L loamy-sand 0.61 loamy-sand 1.67, loamy-sand 2.74 sand 0.61 sand 1.67 sand 2.74 0.024 0.012 10 0.017 0.008 10 0.019 0.007 10 0.016 0.008 9 0.013 0.013 9 0.010 0.007 9 The orthophosphate c o n c e n t r a t i o n s under s a t u r a t e d f l o w c o n d i t i o n s show no s t a t i s t i c a l change w i t h d i s t a n c e . The tempo r a l v a r i a t i o n i n o r t h o p h o s p h a t e can be seen i n f i g u r e s 24 and 25. One f e a t u r e of th e s e p l o t s i s the s i m i l a r i t y of c o n c e n t r a t i o n s w i t h i n the c h a n n e l s , p a r t i c l u a r l y the loamy-sand f i l l e d c h a n n e l s . Another f e a t u r e becomes e v i d e n t when comparing the or t h o p h o s p h a t e c o n c e n t r a t i o n i n the s o i l f i l l e d c h a n n e l s t o the i n f l u e n t 51 0.04 E ,^ 0.03 *< CC UJ o z O 0.02 UJ < X 0_ CO o X Q_ o X cc o 0.01-0.00-100 '•Q 110 120 130 — I — 140 DAY 150 Legend .91 m unsaturated X0.46 m msaturated •o.OO m msaturated 160 170 180 F i g u r e 2 4 . O r t h o p h o s p h a t e f o r L o a m y - S a n d F i l l e d C h a n n e l 0.05 0.04 < DC 0.03 t— Z u i u z o O 0.02 u i x 0_ CO o X 0_ 0.01 0.00 Legend A o •91 m unsaturated ^0.46 m urraturattxj • 0 .00 ra unsaturated 1— 100 110 120 130 140 150 160 170 DAY 180 F i g u r e 2 5 . O r t h o p h o s p h a t e f o r S a n d F i l l e d C h a n n e l 52 o r t h o p h o s p h a t e ( F i g u r e 2 6 ) . S o m e c o r r e l a t i o n i s e v i d e n t , p a r t i c u l a r l y i n t h e d i p s o n d a y 1 2 7 a n d d a y 1 5 4 , a n d t h e r i s e a f t e r d a y 1 7 0 . I n c o m p a r i s o n w i t h t h e i n f l u e n t o r t h o p h o s p h a t e , w h i c h a v e r a g e d 4 . 0 m g / L , t h e o r t h o p h o s p h a t e c o n c e n t r a t i o n s i n t h e c h a n n e l s a r e e x t r e m e l y l o w i r r e s p e c t i v e o f t h e p r e s e n c e o f a n u n s a t u r a t e d z o n e o r s o i l t y p e . T h e r a n g e o f t h e i n f l u e n t o r t h o p h o s p h a t e w a s 2 . 3 t o 6 . 4 m g / L . 0.04 - 0.03 - 0.02 - 0.01 0.00 100 110 120 130 140 150 160 170 180 DAY F i g u r e 2 6 . I n f l u e n t O r t h o p h o s p h a t e a n d M e a n C h a n n e l O r t h o p h o s p h a t e 53 4. DISCUSSION 4.1 C o l i f o r m Removal The r e d u c t i o n of c o l i f o r m s as i n f l u e n c e d by d i f f e r e n t depths of u n s a t u r a t e d s o i l d i d produce s u p e r i o r removal by 0.91 metres of u n s a t u r a t e d s o i l as compared t o 0.46 metres of u n s a t u r a t e d s o i l a c c o r d i n g to f i g u r e s 7 t h r o u g h 10. The p e r c e n t removal of t o t a l and f e c a l c o l i f o r m s f o r 0.91 metres of u n s a t u r a t e d s o i l ( F i g u r e s 8 and 10) l i e above the p e r c e n t removal f o r 0.46 metres of u n s a t u r a t e d s o i l . T h i s i s a r e s u l t t h a t one might e x p e c t , based on the l i t e r a t u r e r e v i e w , but the d i f f e r e n c e i s not g r e a t . In the removal of f e c a l c o l i f o r m s i n sand, 95 p e r c e n t of t h e v a l u e s f o r 0.91 metres of u n s a t u r a t e d s o i l were l e s s t h a n 5 c o l i f o r m s per 100 mL, w h i l e 95 p e r c e n t of the v a l u e s f o r 0.46 metres of u n s a t u r a t e d s o i l were l e s s than 10 c o l i f o r m s per 100 mL. A l t h o u g h c o n s i d e r a t i o n of the d i f f e r e n c e i n l o a d i n g r a t e s may l e a d one t o b e l i e v e t h a t t h i s s e p a r a t i o n s h o u l d be g r e a t e r (the 0.91 metre u n s a t u r a t e d zone was loaded a t a h i g h e r r a t e t h a n the 0.46 metre u n s a t u r a t e d z o n e ) , the d i f f e r e n c e s h o u l d not be a p p r e c i a b l e . F i g u r e s 7 and 8 show the same s u p e r i o r c o l i f o r m removal from 0.91 metres of u n s a t u r a t e d s o i l compared to 0.46 metres of u n s a t u r a t e d s o i l , but a g a i n t h i s d i f f e r e n c e i s not a p p r e c i a b l e . T h i s d i s a g r e e s w i t h the g e n e r a l l i t e r a t u r e b e l i e f t h a t a minimum of 0.9 metres of u n s a t u r a t e d s o i l i s r e q u i r e d f o r proper t r e a t m e n t , but s u p p o r t s the use of 0.41 metres of u n s a t u r a t e d s o i l i n the h e a l t h r e g u l a t i o n s . W i l s o n e t a l (1982) r e p o r t s t h a t a n u n s a t u r a t e d d i s t a n c e a s l i t t l e a s 0 . 2 3 m e t r e s i n c o n j u n c t i o n w i t h a 3 m e t r e s e t b a c k i n a w e t s o i l d i d n o t r e s u l t i n u n a c c e p t a b l e w a t e r q u a l i t y . T h e s t a t i s t i c a l c o m p a r i s o n o f t h e c o l i f o r m n u m b e r s a l s o s u p p o r t s t h e 0 . 4 1 m e t r e s i n t h e h e a l t h r e g u l a t i o n s . T h e s t a t i s t i c a l s i m i l a r i t y o f t h e m e a n v a l u e s s u g g e s t s n o b e n e f i t i n t h e a d d i t i o n a l d e p t h o f u n s a t u r a t e d s o i l . M o s t o f t h e c o l i f o r m r e d u c t i o n m a y o c c u r i n t h e f i r s t 0 . 4 6 m e t r e s o r l e s s o f u n s a t u r a t e d s o i l . T y l e r e t a l ( 1 9 7 7 ) o b s e r v e d a 3 l o g r e d u c t i o n o f c o l i f o r m s i n t h e f i r s t 30 c e n t i m e t r e s o f s o i l . O n e w o u l d e x p e c t s u p e r i o r r e d u c t i o n s w i t h t h e a d d i t i o n a l u n s a t u r a t e d s o i l a s s h o w n b y f i g u r e s 7 t h r o u g h 1 0 , b u t t h e d i f f e r e n c e i s a p p a r e n t l y n o t s t a t i s t i c a l l y s i g n i f i c a n t . T h e s e r e s u l t s a r e a l s o s i g n i f i c a n t w i t h r e s p e c t t o t h e u s e o f m o u n d e d d i s p o s a l s y s t e m s . I n s i t u a t i o n s w h e r e t h e i n s i t u s o i l m a t e r i a l i s n o t s u i t a b l e f o r s e p t i c t a n k e f f l u e n t d i s p o s a l , o r t h e g r o u n d w a t e r t a b l e l i e s t o o c l o s e t o t h e s u r f a c e , t h e m o u n d i s a s a t i s f a c t o r y a l t e r n a t i v e . T h e p l a c e m e n t o f f i l l m a t e r i a l o v e r t h e r e q u i r e d a r e a f o r t h e d i s p o s a l f i e l d t o e n s u r e a m i n i m u m o f 1 m e t r e o f u n s a t u r a t e d s o i l , a s s u g g e s t e d b y t h e l i t e r a t u r e , r e p r e s e n t s a m a j o r i n v e s t m e n t . T h e u s e o f f i l l m a t e r i a l t o e n s u r e a m i n i m u m o f 0 . 5 0 m e t r e s o f u n s a t u r a t e d s o i l , a s s u g g e s t e d b y t h e r e s u l t s , r e p r e s e n t s a m a j o r s a v i n g . T h e r e d u c t i o n o f c o l i f o r m s a s i n f l u e n c e d b y f l o w u n d e r c o m p l e t e l y s a t u r a t e d c o n d i t i o n s w a s s u b s t a n t i a l ( F i g u r e s 11 t h r o u g h 1 6 ) . A t 0 . 6 1 m e t r e s f r o m t h e i n l e t , p e a k s o f 1 0 , 0 0 0 c o l i f o r m s p e r 1 0 0 mL w e r e o b s e r v e d , w h i l e a t 2 . 7 4 m e t r e s f r o m 5 5 t h e i n l e t , p e a k s o f 1 0 0 0 c o l i f o r m s p e r 1 0 0 mL w e r e o b s e r v e d . O n e c o n f u s i n g r e s u l t i s t h e a p p a r e n t I n c r e a s e i n c o l i f o r m n u m b e r s f r o m 1 . 6 7 m e t r e s t o 2 . 7 4 m e t r e s . T h i s i n c r e a s e m a y h a v e b e e n c a u s e d b y s o m e s h o r t c i r c u i t i n g a r o u n d t h e c e n t r a l s a m p l e p o r t i n t h e s y s t e m , o r p o s s i b l e r e g r o w t h a t t h e e x i t o f t h e c h a n n e l . T h e r e l a t i v e l y s m a l l c o l i f o r m n u m b e r s o b s e r v e d i n t h e l o a m y -s a n d a t 0 . 6 1 m e t r e s f r o m t h e p o i n t o f a p p l i c a t i o n s u g g e s t s a v e r y l a r g e r e d u c t i o n o f c o l i f o r m s i n t h a t s h o r t d i s t a n c e . T h e c o l i f o r m n u m b e r s r e m a i n v e r y h i g h i n t h e s a n d f i l l e d c h a n n e l a t t h e s a m e s a m p l i n g p o i n t , b u t d e c l i n e r a p i d l y a l o n g t h e l e n g t h o f t h e c h a n n e l . T h i s s u g g e s t s t h a t t h e f i n e r t e x t u r e d m a t e r i a l i s m o r e e f f e c t i v e i n s h o r t d i s t a n c e s , b u t t h e o v e r a l l r e d u c t i o n o v e r 3 m e t r e s i s s i m i l a r . F i g u r e s 7 t h r o u g h 1 0 p o i n t t o a s u p e r i o r r e d u c t i o n i n c o l i f o r m s i n u n s a t u r a t e d s o i l w i t h t h e s a n d a s o p p o s e d t o t h e l o a m y - s a n d . T h e s a t i s t i c a l c o m p a r i s o n o f t h e m e a n s s u g g e s t s n o d i f f e r e n c e b e t w e e n s o i l t y p e s , b u t t h e v e r y l a r g e s t a n d a r d d e v i a t i o n s s u g g e s t s t h e c o m p a r i s o n m a y b e m i s l e a d i n g . H a g e d o r n e t a l ( 1 9 8 1 ) s t a t e s a s a g e n e r a l i t y t h a t b a c t e r i a l r e t e n t i o n i s i n v e r s e l y p r o p o r t i o n a l t o p a r t i c l e s i z e , a l t h o u g h a s t u d y b y S t e w a r t e t a l ( 1 9 7 9 ) r e p o r t s t h a t a c o a r s e r t e x t u r e d s a n d i s j u s t a s e f f e c t i v e o v e r a l l a s a l o a m y - s a n d i n r e m o v i n g c o l i f o r m b a c t e r i a . S t e w a r t e t a l ( 1 9 7 9 ) p o i n t s o u t t h a t a f i n e t e x t u r e d m a t e r i a l i s m o r e e f f e c t i v e i n t h e f i r s t 1 5 c e n t i m e t r e s . R e a s o n i n g f o r t h i s o b s e r v a t i o n c a n n o t b e b a s e d o n a l o n g e r r e t e n t i o n t i m e i n t h e s a n d b e c a u s e t h e e s t i m a t e d p o r o s i t y i n t h i s s t u d y w a s l o w e r f o r t h e s a n d t h a n f o r t h e l o a m y - s a n d . A l a r g e r c h a n n e l i n p u t f l o w f o r t h e s a n d a l s o r e d u c e s t h e r e t e n t i o n t i m e 56 c o m p a r e d t o t h e l o a m y - s a n d . T h e e x p l a n a t i o n o f t h i s p o i n t m a y h a v e t o b e d i r e c t e d a t t h e s o i l m a t r i x i t s e l f . T h e s a n d m a t r i x , a l t h o u g h h a v i n g o v e r a l l l e s s p o r e s p a c e , h a s a m o r e o p e n s t r u c t u r e t o c o n v e y m o r e l i q u i d o r g a s t h r o u g h i t s m a t r i x , w h i c h a c o m p a r i s o n o f p e r c o l a t i o n r a t e s p r o v e s . B a s e d o n t h i s o n e w o u l d e x p e c t a m o r e a e r o b i c c o n d i t i o n w i t h i n t h e s a n d m a t r i x w h i c h c a n b e s u s t a i n e d b y s o i l a e r a t i o n . S u c h a n a e r o b i c c o n d i t i o n w o u l d s u p p o r t a h i g h e r l e v e l o f b a c t e r i a l a c t i v i t y a n d l e a d t o c o l i f o r m r e d u c t i o n b y c o m p e t i t i o n a n d a t t r i t i o n o f n u t r i e n t s . 4 . 2 R e d u c t i o n i n C h e m i c a l O x y g e n D e m a n d T h e m a j o r i t y o f t h e c h e m i c a l o x y g e n d e m a n d ( C O D ) v a l u e s r e c o r d e d w e r e e x t r e m e l y l o w , w i t h a l l o f t h e m e a n v a l u e s u n d e r 40 m g / L . I f d i l u t i o n a l o n e i s c o n s i d e r e d , t h e s e l o w v a l u e s m a y b e e x p l a i n e d . T h e r a n g e o f d i l u t i o n w i t h i n t h e c h a n n e l s w a s 1 i n 3 t o 1 i n 1 1 ; t h e a v e r a g e i n f l u e n t C O D w a s 1 5 0 m g / L . B a s e d o n d i l u t i o n a l o n e t h e m a x i m u m C O D w o u l d b e 4 5 m g / L . T h i s d o e s n o t e v e n c o n s i d e r t h e p o s s i b l e r e d u c t i o n s d u e t o b i o d e g r a d a t i o n i n t h e u n s a t u r a t e d z o n e . 4 . 3 C h a n g e s i n A m m o n i a A l t h o u g h t h e d o m i n a n t f o r m o f n i t r o g e n i n t h e S T - S A S , a n d t h e f o r m o f n i t r o g e n o f c o n c e r n i n t h i s i n v e s t i g a t i o n , i s i n o r g a n i c n i t r o g e n ( a m m o n i a , n i t r a t e a n d n i t r i t e ) , t h e p r e s e n c e o f o r g a n i c n i t r o g e n a n d i t s p o s s i b l e i n f l u e n c e s s h o u l d b e n o t e d . T h e r a w s e w a g e w h i c h w a s f e d t o t h e s e p t i c t a n k h a d a m e a n t o t a l K j e l d a h l n i t r o g e n o f 2 9 . 6 m g / L ( s o u r c e : E n v i r o n m e n t a l E n g i n e e r i n g 57 L a b o r a t o r y , U n i v e r s i t y o f B r i t i s h C o l u m b i a ) a s o p p o s e d t o a m e a n r a w s e w a g e i n o r g a n i c n i t r o g e n c o n c e n t r a t i o n o f 2 0 . 0 m g / L , i n d i c a t i n g t h e p r e s e n c e o f s u b s t a n t i a l o r g a n i c n i t r o g e n ( s e e T a b l e 2 ) . T o b e n o t e d i s t h e i n c r e a s e o f i n o r g a n i c n i t r o g e n u p o n e x i t f r o m t h e s e p t i c t a n k t o a c o n c e n t r a t i o n o f 2 1 . 8 m g / L , w h i c h i s 74 p e r c e n t o f t h e t o t a l n i t r o g e n . T h i s a g r e e s w i t h t h e f i g u r e o f 7 5 p e r c e n t q u o t e d b y S i k o r a a n d C o r e y ( 1 9 7 6 ) . T h e r e i s a p o s s i b i l i t y o f m i n e r a l i z a t i o n o f o r g a n i c n i t r o g e n t o a m m o n i a n i t r o g e n , w h i c h m a y p r o d u c e v a r i a t i o n s i n t h e r e s u l t s o f t h e i n v e s t i g a t i o n . T h e m i n e r a l i z a t i o n o f o r g a n i c n i t r o g e n , w h i c h w o u l d i n t r o d u c e a d d i t i o n a l n i t r o g e n i n t h e f o r m o f a m m o n i a , m a y s u g g e s t a h i g h e r c a p a c i t y f o r i n o r g a n i c n i t r o g e n r e m o v a l s i n c e t h e r e m o v a l was m e a s u r e d i n t e r m s o f i n f l u e n t i n o r g a n i c n i t r o g e n . T h e m i n e r a l i z a t i o n m a y a l s o s u g g e s t a g r e a t e r c a p a c i t y f o r a m m o n i a o x i d a t i o n , i f i t i s o x i d i z e d , s i n c e t h e t r a n s f o r m a t i o n w a s m e a s u r e d i n t e r m s , o f i n f l u e n t a m m o n i a ( S e e t a b l e 1 4 ) . T h e d e c r e a s e o f a m m o n i a u n d e r c o n d i t i o n s o f b o t h u n s a t u r a t e d a n d s a t u r a t e d f l o w w a s s u b s t a n t i a l ( S e e t a b l e s 8 a n d 9 ) . T h e u n s a t u r a t e d s o i l i n t h e s a n d f i l l e d c h a n n e l s h a d a s i g n i f i c a n t i n f l u e n c e o n t h e d e c r e a s e o f a m m o n i a w h e n c o m p a r e d t o t h e c h a n n e l w i t h n o u n s a t u r a t e d s o i l . T h e a c t u a l d e p t h o f u n s a t u r a t e d s o i l a p p e a r s t o h a v e l i t t l e i n f l u e n c e o n t h e d e c r e a s e o f a m m o n i a . T h e i n f l u e n c e o f t h e u n s a t u r a t e d s o i l i n t h e l o a m y -s a n d f i l l e d c h a n n e l s h a s n o s t a t i s t i c a l d i f f e r e n c e t o t h e s a t u r a t e d s o i l w h e n c o m p a r i n g t h e m e a n a m m o n i a c o n c e n t r a t i o n s . T h e i n f l u e n c e o f s a t u r a t e d f l o w o n a m m o n i a c o n c e n t r a t i o n s w a s v e r y d i f f e r e n t i n t h e t w o s o i l t y p e s . T h e a m m o n i a c o n c e n t r a t i o n r e m a i n e d s t a t i s t i c a l l y c o n s t a n t w i t h d i s t a n c e i n 58 t h e l o a m y - s a n d , w h i l e t h e a m m o n i a c o n c e n t r a t i o n d e c r e a s e d s t e a d i l y w i t h d i s t a n c e i n t h e s a n d . T h e l o w i n i t i a l c o n c e n t r a t i o n i n t h e l o a m y - s a n d s u g g e s t s a m m o n i a s t o r a g e o r r e m o v a l w i t h i n t h e f i r s t 0 . 6 1 m e t r e s o f s a t u r a t e d s o i l . R e n e a u ( 1 9 7 7 ) o b s e r v e d t h e c h a n g e i n a m m o n i a c o n c e n t r a t i o n w i t h d i s t a n c e i n a s a n d y - l o a m , a n d r e c o r d e d d e c r e a s e s o f 9 0 p e r c e n t o v e r a d i s t a n c e o f 1 m e t r e i n s a t u r a t e d g r o u n d w a t e r f l o w . T h e d e c r e a s e i n a m m o n i a i s m u c h s l o w e r i n t h e s a n d , a l t h o u g h t h e f i n a l c o n c e n t r a t i o n i s s t a t i s t i c a l l y s i m i l a r . T h e c o n c e n t r a t i o n o f a m m o n i a i n t h e s a n d f i l l e d c h a n n e l f a l l s b e l o w t h e l o a m y - s a n d a t 1 . 6 7 m e t r e s f r o m t h e p o i n t o f a p p l i c a t i o n . T h i s c o n f i r m s t h e o b s e r v a t i o n b y P r e u l a n d S c h r o e p f e r ( 1 9 6 8 ) t h a t a d s o r p t i o n o f a m m o n i a i s g r e a t e s t i n f i n e r g r a i n e d m a t e r i a l . T h e d e c r e a s e o f a m m o n i a i n t h e s a n d i s s u p e r i o r t o t h e l o a m y - s a n d i n t h e u n s a t u r a t e d f l o w c o n d i t i o n . T h e p r o b a b l e c a u s e i s t h e s u p e r i o r n i t r i f i c a t i o n i n t h e u n s a t u r a t e d z o n e o f t h e s a n d . A s m a l l t e m p o r a l v a r i a t i o n o f t h e a m m o n i a c o n c e n t r a t i o n i n t h e l o a m y - s a n d f i l l e d c h a n n e l s c a n b e s e e n i n a l l t h r e e c a s e s ( S e e f i g u r e 1 8 ) . P r e u l a n d S c h r o e f f e r ( 1 9 6 8 ) r e p o r t e d a d e c l i n e i n a d s o r p t i o n a f t e r 40 d a y s a s a d s o r p t i o n c a p a c i t y w a s r e a c h e d , w h i c h m a y e x p l a i n t h i s i n c r e a s e . 4 . 4 N i t r i f i c a t i o n N i t r i f i c a t i o n w i t h i n t h e u n s a t u r a t e d z o n e w a s v e r y e v i d e n t w i t h i n s o m e o f t h e c h a n n e l s . T h e h i g h c o n c e n t r a t i o n s o f n i t r a t e i n c o n j u n c t i o n w i t h v e r y l o w c o n c e n t r a t i o n s o f a m m o n i a i n t h e s a n d f i l l e d c h a n n e l s i n d i c a t e s s u b s t a n t i a l n i t r i f i c a t i o n 59 a c t i v i t y . A c a l c u l a t i o n w a s p e r f o r m e d t o d e t e r m i n e t h e p e r c e n t a m m o n i a n i t r i f i c a t i o n , b a s e d o n e f f l u e n t v a l u e s , a s f o l l o w s : ( S a m p l e c a l c u l a t i o n f o r s a n d f i l l e d c h a n n e l w i t h 0 . 4 6 m e t r e s o f u n s a t u r a t e d s o i l ) E f f l u e n t n i t r a t e - B a c k g r o u n d n i t r a t e - I n f l u e n t n i t r a t e I n f l u e n t a m m o n i a = F r a c t i o n o f i n f l u e n t a m m o n i a n i t r i f i e d ( 2 . 8 6 m g / L - 0 . 0 8 m g / L ) * 1 3 5 . 7 L / d a v - 2 . 6 m g / d a y 2 1 . 7 m g / L * 2 3 . 4 L / d a y = 3 7 4 . 6 m g / d a y = 0 . 7 4 * 1 0 0 % = 74 p e r c e n t 5 0 7 . 8 m g / d a y S i m i l a r c a l c u l a t i o n s c a n b e p e r f o r m e d o n t h e o t h e r c h a n n e l s w i t h u n s a t u r a t e d z o n e s r e s u l t i n g i n t h e v a l u e s s h o w n i n t a b l e 1 4 . T h i s n i t r i f i c a t i o n c a l c u l a t i o n u s e d t h e v a l u e s o b t a i n e d u p o n e x i t f r o m t h e c h a n n e l , a s o p p o s e d t o t h e v a l u e s o b t a i n e d a t t h e p o i n t c l o s e s t t o t h e b a s e o f t h e u n s a t u r a t e d s e c t i o n b e c a u s e o f p o s s i b l e i n c o m p l e t e m i x i n g a t t h e c l o s e s t p o i n t . S i m i l a r p e r c e n t a g e s w e r e o b t a i n e d b y P r e u l a n d S c h r o e p f e r ( 1 9 6 8 ) , a n d A n d r e o l l e t a l ( 1 9 7 9 ) . P r e u l a n d S c h o e p f e r ( 1 9 6 8 ) m a d e u s e o f a s a n d t o o b t a i n t h e 77 p e r c e n t n i t r i f i c a t i o n , l o a d i n g a t a r a t e 50 p e r c e n t l a r g e r t h a n t h i s e x p e r i m e n t . A n d r e o l i e t a l ( 1 9 7 9 ) o b t a i n e d 80 p e r c e n t n i t r i f i c a t i o n , a t a l o a d i n g r a t e m u c h l o w e r t h a n t h i s e x p e r i m e n t , a n d u n f o r t u n a t e l y t h e y d i d n o t s p e c i f i c a l l y i d e n t i f y t h e s o i l m a t e r i a l . 6 0 T a b l e 1 4 . P e r c e n t o f I n f l u e n t A m m o n i a N i t r i f i e d a n d P e r c e n t o f I n f l u e n t I n o r g a n i c N i t r o g e n R e m o v e d S o i l T y p e U n s a t u r a t e d Z o n e P e r c e n t I n f l u e n t A m m o n i a N i t r i f i e d P e r c e n t o f I n o r g a n i c N i t r o g e n R e m o v e d m e t r e s l o a m y - s a n d l o a m y - s a n d l o a m y - s a n d s a n d 0 . 9 1 0 . 46 0 . 0 0 0 . 9 1 0 . 4 6 0 . 0 0 0 . 6 1 . 1 74 74 9 1 92 8 5 26 2 5 68 s a n d s a n d T h e p e r c e n t n i t r i f i c a t i o n s h o u l d f o l l o w i n v e r s e l y t h e c h a n g e i n a m m o n i a c o n c e n t r a t i o n w i t h i n t h e c h a n n e l s . E x t r e m e l y l o w e f f l u e n t a m m o n i a c o n c e n t r a t i o n s a g r e e w i t h r e l a t i v e l y h i g h v a l u e s o f p e r c e n t a m m o n i a n i t r i f i c a t i o n . T h e l o w p e r c e n t a m m o n i a n i t r i f i c a t i o n i n t h e l o a m y s a n d d o e s c o r r e s p o n d t o r e l a t i v e l y h i g h c o n c e n t r a t i o n s o f a m m o n i a i n t h e e f f l u e n t . T h e t e m p o r a l v a r i a t i o n i n n i t r a t e c o n c e n t r a t i o n w i t h i n t h e l o a m y - s a n d f i l l e d c h a n n e l w i t h 0 . 4 6 m e t r e s o f u n s a t u r a t e d s o i l s u g g e s t s e i t h e r a f a i l u r e i n t h e n i t r i f i c a t i o n o r a n i n c r e a s e i n t h e d e n l t r i f i c a t i o n c a p a b i l i t y o f t h e u n s a t u r a t e d s e c t i o n . S t e w a r t e t a l ( 1 9 7 0 ) r e p o r t e d a n i t r i f i c a t i o n f a i l u r e i n a l o a m y -s a n d s i g n i f i e d b y a n i n c r e a s e i n a m m o n i a a n d a d e c r e a s e i n n i t r a t e . T h e d e f i n i t e r i s e i n a m m o n i a c o n c e n t r a t i o n c e r t a i n l y d o e s n o t m a t c h t h e s u d d e n d r o p i n n i t r a t e c o n c e n t r a t i o n s h o w n i n f i g u r e s 2 1 a n d 2 3 . T h i s s u d d e n d r o p i n c o n c e n t r a t i o n I s m o r e l i k e l y t h e r e s u l t o f d e n l t r i f i c a t i o n w i t h i n t h e l o a m y - s a n d . D e n l t r i f i c a l t o n w i t h i n t h e l o a m y - s a n d m a y e x p l a i n w h y a s i m i l a r d r o p i n n i t r a t e c o n c e n t r a t i o n w a s n o t o b s e r v e d i n t h e l o a m y - s a n d w i t h 0 . 9 1 m e t r e s o f u n s a t u r a t e d s o i l . T h i s d e e p e r s e c t i o n o f u n s a t u r a t e d f l o w m a y n o t h a v e b e e n a b l e t o m a i n t a i n a n a e r o b i c 6 1 s t a t e d u e t o t h e t i g h t n e s s o f t h e s o i l , t h u s a l l o w i n g a n a n a e r o b i c c o n d i t i o n t o d e v e l o p . T h e a n a e r o b i c c o n d i t i o n i n c o n j u n c t i o n w i t h o r g a n i c m a t e r i a l w o u l d p r o m o t e d e n i t r i f i c a t i o n . S e v e r a l COD s a m p l e s o n t h e l o a m y - s a n d w e r e p e r f o r m e d o n u n s e t t l e d s a m p l e s ( i n c l u d i n g s u s p e n d e d s o i l m a t e r i a l ) p r o d u c i n g C O D v a l u e s o f 120 t o 1 8 0 m g / L . D e n i t r i f i c a t i o n i n t h e s a t u r a t e d z o n e i s a p p a r e n t i n f i g u r e 23 w h e r e a r e d u c t i o n i n n i t r a t e c o n c e n t r a t i o n i s d i s p l a y e d b e t w e e n t h e s a m p l i n g p o i n t s a t 0 . 6 1 m e t r e s a n d 1 . 6 7 m e t r e s . T h e d e c r e a s e i n n i t r a t e c o n c e n t r a t i o n f r o m a v a l u e g e n e r a l l y a b o v e 2 m g / L t o v a l u e s l e s s t h a n 0 . 4 m g / L a t 1 . 6 7 m e t r e s , s u g g e s t s t h a t d e n i t r i f i c a t i o n i s o c c u r r i n g . T h i s r e d u c t i o n m a y n o t b e t h e r e s u l t o f a d s o r p t i o n b y s o i l p a r t i c l e s b e c a u s e P e a v y e t a l ( 1 9 7 7 ) r e p o r t s t h i s d o e s n o t o c c u r i n a s a t u r a t e d s o i l . A c o n s i d e r a t i o n o f d i l u t i o n a l s o d o e s n o t e x p l a i n t h e r e d u c t i o n o f n i t r a t e f r o m a m e a n o f 2 . 6 . . m g / L t o 0 . 2 2 m g / L , s i n c e t h e d i l u t i o n f a c t o r i s o n l y 1 : 4 . 4 . T h e p o s s i b i l i t y o f d e n i t r i f i c a t i o n w i t h i n t h e u n s a t u r a t e d a n d s a t u r a t e d z o n e s o f t h e l o a m y - s a n d c o u l d m a k e t h e p e r c e n t i n f l u e n t a m m o n i a n i t r i f i e d c a l c u l a t i o n f o r t h i s s o i l i n e r r o r , s i n c e t h e a c t u a l n i t r a t e c o n c e n t r a t i o n w o u l d h a v e b e e n m u c h h i g h e r i f d e n i t r i f i c a t i o n h a d n o t o c c u r r e d . 4 . 5 I n o r g a n i c N i t r o g e n R e m o v a l A m a s s b a l a n c e c a n b e p e r f o r m e d t o d e t e r m i n e t h e n e t i n o r g a n i c n i t r o g e n r e m o v a l i n e a c h o f t h e c h a n n e l s . ( S a m p l e c a l c u l a t i o n f o r l o a m y - s a n d f i l l e d c h a n n e l w i t h 0 . 4 6 m e t r e s o f u n s a t u r a t e d s o i l ) 62 M a s s B a l a n c e E q u a t i o n Sum i n f l u e n t n i t r o g e n = S u m e f f l u e n t n i t r o g e n + N i t r o g e n r e m o v e d o r I n f l u e n t a m m o n i a + I n f l u e n t n i t r a t e = E f f l u e n t a m m o n i a + E f f l u e n t n i t r a t e + E f f l u e n t n i t r i t e + N i t r o g e n r e m o v e d ( 2 1 . 7 m g / L ) 1 6 . 8 L / d a y = ( 0 . 2 8 m g / L + 0 . 0 8 m g / L + 0 . 0 2 m g / L ) 7 4 . 5 L / d a y + N i t r o g e n r e m o v e d 3 6 4 . 6 m g / d a y = 2 8 . 3 m g / d a y + N i t r o g e n r e m o v e d N i t r o g e n r e m o v e d = 3 3 6 . 3 m g / d a y R e d u c t i o n o f 92 p e r c e n t S i m i l a r c a l c u l a t i o n s c a n a l s o b e p e r f o r m e d o n a l l o f t h e o t h e r c h a n n e l s p r o d u c i n g t h e r e s u l t s s h o w n i n t a b l e 1 4 . A c o m p a r i s o n o f t h e v a l u e s o f p e r c e n t i n f l u e n t a m m o n i a n i t r i f i e d a n d p e r c e n t i n o r g a n i c n i t r o g e n r e m o v e d s u g g e s t s a r e l a t i o n s h i p b e t w e e n t h e c o n c e n t r a t i o n o f a m m o n i a o r n i t r a t e , a n d t h e r e m o v a l o f i n o r g a n i c n i t r o g e n . I n p a r t i c u l a r , n i t r o g e n i n t h e f o r m o f n i t r a t e d o e s n o t a p p e a r t o b e a s r e a d i l y r e m o v e d a s n i t r o g e n i n t h e f o r m o f a m m o n i a . P r e u l a n d S c h r o e p f e r ( 1 9 6 8 ) s u p p o r t t h i s s t a t e m e n t b y r e p o r t i n g n o i n h i b i t i o n t o n i t r o g e n m o v e m e n t w h e n i t i s i n t h e f o r m o f n i t r a t e . P r e u l a n d S c h r o e p f e r ( 1 9 6 8 ) r e p o r t t h a t n i t r o g e n r e m o v a l ( a d s o r p t i o n ) i s g r e a t e s t i n s o i l s w i t h f i n e r g r a i n e d m a t e r i a l , s u c h a s s i l t s o r c l a y s . T h e r e m o v a l o f n i t r o g e n i n t h e l o a m y -s a n d i s v e r y h i g h ; C h o w d r y ( 1 9 7 7 ) r e p o r t e d a 9 0 p e r c e n t n i t r o g e n r e m o v a l i n a s a n d c l a y m i x t u r e . P r e u l a n d S c h r o e p f e r ( 1 9 6 8 ) r e p o r t t h e n i t r o g e n r e m o v a l i n s a n d t o b e 22 p e r c e n t , w h i c h i s i n a g r e e m e n t w i t h t h e s a n d f i l l e d c h a n n e l s , e x c e p t f o r t h e c h a n n e l w i t h n o u n s a t u r a t e d f l o w . T h e 68 p e r c e n t n i t r o g e n r e m o v a l w i t h i n t h i s c h a n n e l f a l l s o u t o f l i n e w i t h b o t h t h e l o a m y - s a n d a n d t h e s a n d . 6 3 4 . 6 O r t h o p h o s p h a t e R e m o v a l T h e e f f l u e n t v a l u e s f o r o r t h o p h o s p h a t e a r e v e r y l o w i n a l l o f t h e c h a n n e l s i n d i c a t i n g a n e q u a l c a p a b i l i t y o f p h o s p h o r u s r e m o v a l i n b o t h s o i l s . A m a s s b a l a n c e f o r t h e o r t h o p h o s p h a t e c a n b e p e r f o r m e d t o d e t e r m i n e t h e o r t h o p h o s p h a t e r e m o v e d i n t h e c h a n n e l s . ( S a m p l e c a l c u l a t i o n f o r l o a m y - s a n d f i l l e d c h a n n e l w i t h 0 . 4 6 m e t r e s o f u n s a t u r a t e d s o i l ) M a s s B a l a n c e E q u a t i o n I n f l u e n t o r t h o p h o s p h a t e = E f f l u e n t o r t h o p h o s p h a t e + O r t h o p h o s p h a t e r e m o v e d ( 4 . 0 m g / L ) 1 6 . 8 L / d a y = ( 0 . 0 2 0 m g / L ) 7 5 . 4 L / d a y + O r t h o p h o s h a t e r e m o v e d 6 7 . 2 m g / d a y = 1 . 4 9 m g / d a y + O r t h o p h o s p h a t e r e m o v e d O r t h o p h o s p h a t e r e m o v e d = 6 5 . 7 m g / d a y R e d u c t i o n o f 98 p e r c e n t S i m i l a r c a l c u l a t i o n s c a n b e p e r f o r m e d o n a l l o f t h e o t h e r c h a n n e l s p r o d u c i n g t h e r e s u l t s s h o w n i n T a b l e 1 5 . T a b l e 1 5 . P e r c e n t o f I n f l u e n t O r t h o p h o s p h a t e R e m o v e d S o i l T y p e U n s a t u r a t e d Z o n e P e r c e n t O r t h o p h o s p h a t e m e t r e s R e m o v e d l o a m y - s a n d 0 . 9 1 9 7 l o a m y - s a n d 0 . 4 6 98 l o a m y - s a n d 0 . 0 0 96 s a n d 0 . 9 1 9 9 s a n d 0 . 4 6 9 7 s a n d 0 . 0 0 96 J o n e s a n d L e e ( 1 9 7 9 ) r e p o r t p h o s p h o r u s r e m o v a l t o b e t y p i c a l l y 9 5 p e r c e n t i n m e d i u m s a n d y s o i l s a n d J o h n ( 1 9 7 4 ) 64 r e p o r t s 90 t o 9 5 p e r c e n t p h o s p h o r u s r e m o v a l i n l o a m s . T h e s e l i t e r a t u r e v a l u e s a r e v e r y m u c h i n l i n e w i t h t h e v a l u e s o b t a i n e d i n t h i s s t u d y . T h e e q u a l l y g o o d p e r c e n t a g e r e m o v a l o f o r t h o p h o s p h a t e i n t h e s a n d a n d t h e l o a m y - s a n d s u g g e s t s o r t h o p h o s p h a t e r e m o v a l i s n o t d e p e n d e n t u p o n m a t e r i a l s i z e . J o n e s a n d L e e ( 1 9 7 9 ) c o n c l u d e d t h a t rainerology c o n t r o l l e d p h o s p h a t e r e m o v a l a n d n o t p a r t i c l e s i z e . T h e f o r m a t i o n o f i n s o l u b l e p h o s p h a t e c o m p o u n d s , a s d i s c u s s e d b y E n f i e l d a n d B l e d s o e ( 1 9 7 9 ) , w a s a l s o i n d e p e n d e n t o f p a r t i c l e s i z e . T h e t e m p o r a l v a r i a t i o n s i n o r t h o p h o s p h a t e c o n c e n t r a t i o n d i s p l a y v a r i a t i o n s w h i c h a t f i r s t a n a l y s i s d o n o t s h o w a n y p a t t e r n . A c o m p a r i s o n t o i n f l u e n t o r t h o p h o s p h a t e ( F i g u r e 2 6 ) p o i n t s t o s o m e s i m i l a r p a t t e r n s i n c o n c e n t r a t i o n s , p a r t i c u l a r l y t h e l o w i n f l u e n t c o n c e n t r a t i o n n e a r d a y 1 3 0 a n d t h e s i m i l a r l o w p o i n t s i n t h e s a n d a n d l o a m y - s a n d . T h e h i g h p o i n t i n i n f l u e n t c o n c e n t r a t i o n n e a r d a y 1 8 0 i s r e p e a t e d m o s t n o t i c e a b l y i n t h e s a n d f i l l e d c h a n n e l s . A m a t h e m a t i c a l c o m p a r i s o n o f t h e s e s i m i l a r i t i e s y i e l d s a n o v e r a l l c o r r e l a t i o n c o e f f i c i e n t f o r a l l t h e c h a n n e l s o f 0 . 7 8 ( S e e a p p e n d i x , p a r t 2 ) . L a n c e ( 1 9 7 7 ) r e c o r d e d a s i m i l a r f l u c t u a t i o n o f i n f l u e n t a n d e f f l u e n t o r t h o p h o s p h a t e c o n c e n t r a t i o n , a l t h o u g h t h e c h a n g e s i n i n f l u e n t c o n c e n t r a t i o n w e r e t h e r e s u l t o f i n f i l t r a t i o n r a t e . T h i s s u g g e s t s i n c r e a s e d r e m o v a l w i t h i n c r e a s e d l o a d i n g , a s l o n g a s t h e s o i l h a s a d s o r p t i o n c a p a c i t y . L a n c e ( 1 9 7 7 ) c o n c l u d e d t h a t r e m o v a l was d e p e n d e n t u p o n i n f i l t r a t i o n r a t e ( l o a d i n g ) . 6 5 5 . C O N C L U S I O N S C o n t r a r y t o m u c h o f t h e l i t e r a t u r e , t h e r e s u l t s o f t h i s s t u d y s u g g e s t t h a t 0 . 4 1 m e t r e s o f u n s a t u r a t e d s o i l ( 1 6 i n c h e s ) , a s u s e d i n t h e B . C . p r o v i n c i a l g u i d e l i n e s , s a t i s f a c t o r i l y r e d u c e s c o l i f o r m s , b i o d e g r a d e a b l e m a t e r i a l a n d n u t r i e n t s , w i t h t h e e x c e p t i o n o f n i t r a t e i n t h e t w o s o i l s t e s t e d . T h e s e r e s u l t s m a y b e e x t e n d e d t o i n c l u d e m o u n d e d d i s p o s a l s y s t e m s . T h e r e s u l t s s u g g e s t t h a t a n o m i n a l 0 . 5 m e t r e s o f u n s a t u r a t e d s o i l i n t h e f i l l m a t e r i a l m a y b e s u f f i c i e n t t o e n s u r e t h e r e d u c t i o n o f a l l c o n t a m i n a n t s o f c o n c e r n , e x c e p t n i t r a t e . T h e p r o b l e m o f n i t r i f i c a t i o n w i t h i n t h e u n s a t u r a t e d s o i l o n l y a p p e a r s t o b e a s i g n i f i c a n t p r o b l e m i n t h e s a n d . A l t h o u g h t h e l o a d i n g r a t e s i n t h i s s t u d y w e r e s e v e r a l t i m e s g r e a t e r t h a n t h e r e c o m m e n d e d l o a d i n g r a t e s b a s e d o n p e r c o l a t i o n r a t e s , o n e m i g h t e x p e c t n i t r a t e c o n c e n t r a t i o n s o f s e v e r a l m i l l i g r a m s p e r l i t r e o r h i g h e r i n a f i e l d s i t u a t i o n . T h e p o s s i b l e r o l e o f d e n i t r i f i c a t i o n i n t h e l o a m y - s a n d p r o v i d e d a s o l u t i o n f o r a n y p o t e n t i a l p r o b l e m s w i t h n i t r i f i c a t i o n i n t h i s s o i l . S p e c i a l c o n s i d e r a t i o n o f p o s s i b l e d r i n k i n g w a t e r c o n t a m i n a t i o n s h o u l d b e m a d e w h e r e h i g h d e g r e e s o f n i t r i f i c a t i o n c a n o c c u r i n t h e d i s p o s a l s o i l . T h e r e s u l t s o b t a i n e d a l o n g t h e h o r i z o n t a l s a t u r a t e d z o n e s u g g e s t t h a t 3 . 0 m e t r e s o f s a t u r a t e d s o i l c a n r e d u c e c o l i f o r m s , b i o d e g r a d e a b l e m a t e r i a l , n i t r o g e n a n d p h o s p h o r u s , a n d m a y o f f e r , f o r s o m e s o i l s , a r e d u c t i o n o f c o n t a m i n a n t s c o m p a r a b l e t o u n s a t u r a t e d s o i l . T h e f o r m a t i o n o f n i t r a t e s i s n o t a p r o b l e m 6 6 u n d e r t h i s c o n d i t i o n b e c a u s e t h e r e i s n o u n s a t u r a t e d z o n e i n w h i c h n i t r i f i c a t i o n c a n o c c u r . T h e r e m o v a l o f n u t r i e n t s w i t h i n t h e s a t u r a t e d a n d u n s a t u r a t e d z o n e s w a s v e r y s a t i s f a c t o r y f o r t h e d u r a t i o n o f t h e s t u d y . T h e t e m p o r a l v a r i a t i o n s i n a m m o n i a o b s e r v e d s u g g e s t I n c r e a s e d c o n c e n t r a t i o n s w i t h t i m e , a s a d s o r p t i v e c a p a c i t y i s u s e d u p . T h e a d s o r p t i o n o f o r t h o p h o s p h a t e d i d n o t d e c l i n e d u r i n g t h e s t u d y , b u t t h e l i t e r a t u r e p o i n t e d o u t t h e f i n i t e a d s o r p t i v e c a p a c i t y o f s o i l s . I n a d d i t i o n t o h o r i z o n t a l a n d v e r t i c a l s e p a r a t i o n d i s t a n c e s , t h e c o n s i d e r a t i o n o f p e r c o l a t i o n r a t e i n t h e h e a l t h g u i d e l i n e s p r o m o t e s c o a r s e r m a t e r i a l a s s u p e r i o r f o r t h e d i s p o s a l o f s e p t i c t a n k e f f l u e n t . T h i s s u g g e s t s t h e m a j o r d i f f i c u l t y i s o n e o f l i q u i d d i s p o s a l a n d n o t w a s t e w a t e r r e n o v a t i o n . A b e t t e r u n d e r s t a n d i n g o f a l l t h e i n f l u e n c i n g f a c t o r s i n t h e r e n o v a t i o n o f w a s t e w a t e r i n s o i l m a y p r o d u c e r e g u l a t i o n s w h i c h a l l o w c o m p r e h e n s i v e d e s i g n i n a r e a s w i t h l e s s t h a n i d e a l c o n d i t i o n s f o r o n - s i t e d i s p o s a l . T h e u n s a t u r a t e d a n d s a t u r a t e d z o n e s w i t h i n a t w o - z o n e s y s t e m b o t h h a v e c h a r a c t e r i s t i c s w h i c h m a y b e u s e d t o m a x i m i z e t h e e f f l u e n t q u a l i t y i n s o i l d i s p o s a l o f s e p t i c t a n k e f f l u e n t . T h e s o l u t i o n t o t h e p o t e n t i a l p r o b l e m s c a u s e d b y e a c h z o n e i s t o d e s i g n a n e f f l u e n t d i s p o s a l f i e l d b a s e d o n t h e s o i l a n d g r o u n d w a t e r c h a r a c t e r i s t i c s o f a i n d i v i d u a l s i t e . 67 6. R E C O M M E N D A T I O N S F u r t h e r i n v e s t i g a t i o n i n t o t h e r o l e o f s a t u r a t e d z o n e s f o r d i s p o s a l o f s e p t i c t a n k e f f l u e n t w o u l d b e d e s i r a b l e t o s t r e n g t h e n t h e r e s u l t s o b s e r v e d i n t h i s s t u d y . T h e u s e o f o t h e r s o i l m a t e r i a l s w o u l d a l s o b r o a d e n t h e s c o p e o f t h i s s t u d y f o r p o s s i b l e a p p l i c a t i o n t o m o d i f y t h e g u i d e l i n e s . A f i e l d s t u d y t o a s s u r e p r a c t i c a l a p p l i c a t i o n o f t h e s e r e s u l t s w o u l d b e a d e s i r a b l e f i n a l s t e p t o c o m p l e t e t h e s c o p e o f t h i s t o p i c . 68 B I B L I O G R A P H Y 1 . A M E R I C A N P U B L I C A T I O N H E A L T H A S S O C I A T I O N . 1 9 8 0 . S t a n d a r d M e t h o d s f o r t h e E x a m i n a t i o n o f W a t e r a n d W a s t e r w a t e r . F i f t e e n t h E d i t i o n . 2 . A N D R I O L I , A . , B A R T I L U C C I , N . , F O R G I O N E , R . , R E Y N O L D S , R . 1 9 7 9 . N i t r o g e n R e m o v a l i n a S u b s u r f a c e D i s p o s a l S y s t e m . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 5 1 , N o . 4 , p p . 8 4 1 - 8 5 4 . 3 . B O U M A , J . , Z I E B E L L , W . A . , W A L K E R , W . G . , O L C O T T , P . G . , M c C O Y , E . , H O L E , F . D . 1 9 7 2 . S o i l A b s o r p t i o n o f S e p t i c T a n k E f f l u e n t : A f i e l d s t u d y o f s o m e M a j o r S o i l s i n W i s c o n s i n . C i r c u l a r N o . 2 0 , U n i v e r s i t y o f W i s c o n s i n , M a d i s o n . 4 . BOUMA J . 1 9 7 5 . U n s a t u r a t e d F l o w D u r i n g s o i l T r e a t m e n t o f S e p t i c T a n k E f f l u e n t . J o u r n a l o f t h e E n v i r o n m e n t a l E n g i n e e r i n g D i v i s i o n , A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s , V o l . 9 8 , N o . E E 6 , p p . 9 6 7 - 9 8 3 . 5 . B R A N D E S , M . , C H O W D R Y , N . A . , C H E N G , W . W . 1 9 7 4 . E x p e r i m e n t a l S t u d y o n R e m o v a l o f P o l l u t a n t s F r o m D o m e s t i c S e w a g e b y U n d e r d r a i n e d S o i l F i l t e r s . P r o c e e d i n g s o f t h e N a t i o n a l Home S e w a g e D i s p o s a l S y m p o s i u m , p p . 2 9 - 3 5 . 6 . B R O W N , K . W . , S L O W E Y , J . F . , W O L F , H . W . 1 9 7 7 . T h e M o v e m e n t o f S a l t s , N u t r i e n t s , F e c a l C o l i f o r m s a n d V i r u s B e l o w S e p t i c L e a c h F i e l d s i n 3 S o i l s . P r o c e e d i n g s o f t h e S e c o n d N a t i o n a l Home S e w a g e T r e a t m e n t S y m p o s i u m , p p . 2 0 8 - 2 1 7 . 7 . B U T L E R , R . G . , O R L O B , G . T . , M c G A U H E Y , P . H . 1 9 5 4 . U n d e r g r o u n d m o v e m e n t o f B a c t e r i a l a n d C h e m i c a l P o l l u t a n t s . J o u r n a l o f t h e A m e r i c a n W a t e r W o r k s A s s o c i a t i o n , V o l . 4 6 , p p . 9 7 - 1 1 1 . 8 . C H A N , H . T . 1 9 7 9 . S t u d y o f C o n v e n t i o n a l T i l e F i e l d s i n F i n e -G r a i n e d S o i l s . R e p o r t S 7 4 , O n t a r i o M i n i s t r y o f t h e E n v i r o n m e n t . 9 . C H A N L E T T , E . T . 1 9 7 9 . E n v i r o n m e n t a l P r o t e c t i o n . M c G r a w - H i l l , p p . 1 9 5 - 1 9 8 . 1 0 . C H O W D R Y , N . A . 1 9 7 8 . D o m e s t i c W a s t e W a t e r D i s p o s a l a n d N u t r i e n t R e m o v a l b y S e p t i c T a n k - S a n d F i l t e r S y s t e m . R e p o r t N o . 7 7 , O n t a r i o M i n i s t r y o f t h e E n v i r o n m e n t . 1 1 . C H O W D R Y , N . A . 1 9 7 7 . S e p t i c T a n k S a n d F i l t e r S y s t e m f o r T r e a t m e n t o f D o m e s t i c S e w a g e . R e p o r t N o . W 6 4 , O n t a r i o M i n i s t r y o f E n v i r o n m e n t . 69 1 2 . C O G G E R , C , C A R L I L E , B . 1 9 8 4 . F i e l d P e r f o r m a n c e o f C o n v e n t i o n a l a n d A l t e r n a t i v e S e p t i c S y s t e m s i n Wet S o i l s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 1 3 , N o . l , p p . 1 3 7 - 1 4 2 . 1 3 . C O N V E R S E , J . C . 1 9 7 4 . D i s t r i b u t i o n o f D o m e s t i c W a s t e E f f l u e n t i n S o i l A b s o r p t i o n B e d s . T r a n s a c t i o n s o f t h e A m e r i c a n S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s , V o l . 4 . 1 4 . D E V R I E S , J . 1 9 8 3 . P e r s o n a l c o m m u n i c a t i o n s . 1 5 . D E V R I E S , J . 1 9 8 3 . P h y s i c a l B e h a v i o u r o f S o i l s . L a b o r a t o r y M a n u a l : S o i l S c i e n c e 4 1 3 , D e p a r t m e n t o f S o i l S c i e n c e , U n i v e r s i t y o f B r i t i s h C o l u m b i a . 1 6 . D E V R I E S , J . 1 9 7 2 . S o i l F i l t r a t i o n o f W a s t e w a t e r E f f l u e n t a n d t h e M e c h a n i s m o f P o r e C l o g g i n g . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 4 , N o . 4 , p p . 5 6 5 - 5 7 3 . 1 7 . D E W A L L E , F . B . , S C H A F F , R . M . 1 9 8 0 . G r o u n d w a t e r P o l l u t i o n b y S e p t i c T a n k D r a i n f i e l d s . J o u r n a l o f t h e E n v i r o n m e n t a l E n g i n e e r i n g D i v i s i o n , A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s , V o l . 1 0 3 , N o . E E 3 , p p . 6 3 1 - 6 4 6 . 1 8 . E N F I E L D , C . G . , B L E D S O E , B . E . 1 9 7 5 . F a t e o f W a s t e w a t e r P h o s p h o r o u s i n S o i l . J o u r n a l o f t h e I r r i g a t i o n a n d D r a i n a g e D i v i s i o n , A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s , V o l . 1 0 1 , N o . 3 , p p . 1 4 5 - 1 5 5 . 1 9 . F R A N K I C H , K . 1 9 8 4 . I n t r o d u c t i o n t o A d j u s t m e n t s o f S u r v e y i n g M e a s u r e m e n t s . B r i t i s h C o l u m b i a I n s t i t u t e o f T e c h n o l o g y S u r v e y i n g D e p a r t m e n t . 2 0 . F R E E Z E , R . A . , C H E R R Y , J . A . 1 9 7 9 . G r o u n d w a t e r . P r e n t i c e -H a l l . 2 1 . F R E N C H , B . 1 9 7 2 . T h e P h y s i c a l P r o p e r t i e s a n d S u i t a b i l i t y f o r S e p t i c T a n k D r a i n f i e l d o f a F r a s e r V a l l e y S o i l . U n d e r g r a d u a t e T h e s i s , D e p a r t m e n t o f A g r i c u l t u r a l S c i e n c e , U n i v e r s i t y o f B r i t i s h C o l u m b i a . 2 2 . H A G E D O R N , C . 1 9 8 4 . G r o u n d w a t e r P o l l u t i o n M i c r o b i o l o g y -M i c r o b i o l o g i c a l A s p e c t s o f G r o u n d w a t e r P o l l u t i o n D u e t o S e p t i c T a n k s , e d i t e d b y G . B i t t o n a n d C P . G e r b a . F i r s t e d i t i o n . J o h n W i l e y a n d S o n s , T o r o n t o . p p . 1 8 1 - 1 9 5 . 2 3 . H A G E D O R N , C , M c C O Y , E . L . , R A H E , T . M . 1 9 8 1 . P o t e n t i a l f o r G r o u n d W a t e r C o n t a m i n a t i o n F r o m S e p t i c T a n k E f f l u e n t s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 1 0 , N o . 1 , p p . 1 - 7 . 2 4 . H A G E D O R N , C , H A N S E N , D . T . , S I M O N S O N , G . H . 1 9 7 8 . S u r v i v a l a n d M o v e m e n t o f F e c a l I n d i c a t o r B a c t e r i a U n d e r C o n d i t i o n s o f S a t u r a t e d F l o w s , . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 7 , N o . 1 . p p . 5 5 - 5 9 . 70 2 5 . H A N S E L , M . J . , M A C H M E I E R , R . E . 1 9 8 0 . O n s i t e W a s t e w a t e r T r e a t m e n t i n P r o b l e m S o i l s . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 5 2 , N o . 3 , p p . 5 4 9 - 5 5 8 . 2 6 . H E A L Y , K . A . , L A A K , R . 1 9 7 3 . F a c t o r s A f f e c t i n g t h e P e r c o l a t i o n T e s t . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 5 , N o . 7 , p p . 1 5 0 8 - 1 5 1 6 . 2 7 . J O H N , M . K . 1 9 7 4 . W a s t e w a t e r R e n o v a t i o n T h r o u g h S o i l P e r c o l a t i o n . W a t e r , A i r a n d S o i l P o l l u t i o n , V o l . 3 , N o . 1 , p p . 3 - 1 0 . 2 8 . J O N E S , R . A . , L E E , G . F . 1 9 7 9 . S e p t i c T a n k W a s t e w a t e r D i s p o s a l S y s t e m s a s P h o s p h o r o u s S o u r c e s f o r S u r f a c e W a t e r s . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 5 1 , N o . 1 1 , p p . 2 7 6 4 - 2 7 7 5 . 2 9 . K R I S T I A N S E N , R . 1 9 8 1 . S a n d f i l t e r T r e n c h e s f o r P u r i f i c a t i o n o f S e p t i c T a n k E f f l u e n t : P a r t 1 - T h e C l o g g i n g M e c h a n i s m a n d S o i l P h y s i c a l E n v i r o n m e n t , P a r t 2 - T h e F a t e o f N i t r o g e n . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 1 0 , N o . 3 , p p . 3 5 3 - 3 6 1 . 3 0 . K R O P F , F . W . , L A A K , R . , H E A L Y , K . A . 1 9 7 7 . E q u i l i b r i u m O p e r a t i o n o f S u b s u r f a c e A b s o r p t i o n S y s t e m s . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 9 , N o . 9 , p p . 2 0 0 7 -2 0 1 6 . 3 1 . L A M B E , T . W . 1 9 5 1 . S o i l T e s t i n g f o r E n g i n e e r i n g . J o h n W i l e y a n d S o n s , T o r o n t o . 3 2 . L A N C E , J . C . 1 9 7 7 . P h o s p h a t e R e m o v a l F r o m S e w a g e W a t e r b y S o i l C o l u m n s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 6 , N o . 3 , p p . 2 7 9 - 2 8 4 . 3 3 . L A N C E , J . C . 1 9 7 5 . F a t e o f N i t r o g e n i n S e w a g e E f f l u e n t A p p l i e d t o S o i l . J o u r n a l o f t h e I r r i g a t i o n a n d D r a i n a g e D i v i s i o n , A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s , V o l . 1 0 1 , N o . 3 , p p . 1 3 1 - 1 4 3 . 3 4 . L A N C E , J . C . 1 9 7 2 . N i t r o g e n R e m o v a l b y S o i l M e c h a n i s m s . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 4 , N o . 7 , p p . 1 3 5 3 - 1 3 6 1 . 3 5 . M A G D O F F , F . R . , K E E N E Y , D . R . , B O U M A , J . , Z I E B E L L , W . A . 1 9 7 4 . C o l u m n s R e p r e s e n t i n g M o u n d - T y p e D i s p o s a l S y s t e m s I I . N u t r i e n t T r a n s f o r m a t i o n s a n d B a c t e r i a l P o p u l a t i o n s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 3 , N o . 3 , p p . 2 2 9 - 2 3 4 . 3 6 . M A G D O F F , F . R . , K E E N E Y , D . R . 1 9 7 5 . N u t r i e n t M a s s B a l a n c e i n C o l u m n s R e p r e s e n t i n g F i l l S y s t e m s f o r D i s p o s a l o f S e p t i c T a n k E f f l u e n t . E n v i r o n m e n t a l L e t t e r s , V o l . 1 0 , p p . 2 8 5 - 2 9 4 . 3 7 . M I N I S T R Y O F T H E E N V I R O N M E N T , P R O V I N C E O F B R I T I S H C O L U M B I A . 1 9 7 9 . P o l l u t i o n C o n t r o l O b j e c t i v e s f o r M u n i c i p a l T y p e W a s t e D i s c h a r g e s i n B r i t i s h C o l u m b i a . 71 3 8 . M I N I S T R Y O F H E A L T H , P R O V I N C E O F B R I T I S H C O L U M B I A . 1 9 7 5 . H e a l t h A c t . V i c t o r i a , B . C . 3 9 . O L D H A M , W . K . , K E N N E D Y , G . F . 1 9 7 2 . I n f l u e n c e o f S e p t i c T a n k E f f l u e n t o n R e c e i v i n g W a t e r N u t r i e n t G a i n F r o m G r o u n d w a t e r . O k a n a g a n B a s i n S t u d y , T a s k 1 3 9 ( P a r t T h e r e o f ) . 4 0 . O L I V E I E R I , A . W . , R O C H E , , J O H N S T O N , . 1 9 8 1 . G u i d e l i n e s f o r C o n t r o l o f S e p t i c T a n k S y s t e m s . J o u r n a l o f t h e E n v i r o n m e n t a l E n g i n e e r i n g D i v i s i o n , A m e r i c a n S o c i e t y o f C i v i l E n g i n e e r s , V o l . 1 0 7 , N o . E E 5 , p p . 1 0 2 5 - 1 0 3 3 . 4 1 . O T I S , R . J . , C O N V E R S E , J . C . , C A R L I L E , B . L . , W I T T Y , J . E . 1 9 7 7 . E f f l u e n t D i s t r i b u t i o n . Home S e w a g e T r e a t m e n t , A m e r i c a n S o c i e t y f o r A g r i c u l t u r a l E n g i n e e r s P u b l i c a t i o n . 4 2 . P E A V Y , H . S . , G R O V E S , K . S . 1 9 7 7 . T h e I n f l u e n c e o f S e p t i c T a n k D r a i n f i e l d s i n A r e a s o f H i g h G r o u n d w a t e r . P r o c e e d i n g s o f t h e S e c o n d N a t i o n a l Home S e w a g e D i s p o s a l S y m p o s i u m , C h i c a g o , p p . 2 1 8 - 2 2 5 . 4 3 . P R E U L , H . C . , S C H R O E P F E R , G . J . 1 9 6 8 . T r a v e l o f N i t r o g e n i n S o i l s . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 0 , N o . 1 , p p . 3 0 - 4 8 . 4 4 . R A H E , T . M . , H A G E D O R N , C , M c C O Y , E . L . , K L I N G , G . F . 1 9 7 9 . T r a n s p o r t o f A n t i b i o t i c - R e s i s t a n t E s c h e r i c h i a C o l i T h r o u g h W e s t e r n O r e g o n H i l l s l o p e S o i l s U n d e r C o n d i t i o n s o f S a t u r a t e d F l o w . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 7 , N o . 4 , p p . 4 8 7 - 4 9 4 . 4 5 . R E N E A U , R . B . 1 9 7 9 . C h a n g e s i n C o n c e n t r a t i o n o f S e l e c t e d C h e m i c a l P o l l u t a n t s i n W e t , T i l e D r a i n e d S o i l S y s t e m s a s I n f l u e n c e d b y D i s p o s a l o f S e p t i c T a n k E f f l u e n t s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 8 , N o . 2 , p p . 1 8 9 - 1 9 5 . 4 6 . R E N E A U , R . B . 1 9 7 8 . I n f l u e n c e o f A r t i f i c i a l D r a i n a g e o n P e n e t r a t i o n o f C o l i f o r m B a c t e r i a f r o m S e p t i c T a n k E f f l u e n t s i n t o W e t T i l e D r a i n e d S o i l s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 7 , N o . 1 , p p . 2 3 - 2 9 . 4 7 . R E N E A U , R . B . 1 9 7 7 . C h a n g e s i n I n o r g a n i c N i t r o g e n o u s c o m p o u n d s f r o m S e p t i c T a n k E f f l u e n t i n a S o i l w i t h a F l u c t u a t i n g W a t e r T a b l e . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 6 , N o . 2 , p p . 1 7 3 - 1 7 8 . 4 8 . R E N E A U , R . B . , P E T T R Y , D . E . 1 9 7 6 . P h o s p h o r o u s d i s t r u b u t i o n f r o m S e p t i c T a n k E f f l u e n t i n C o a s t a l P l a i n S o i l s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 5 , N o . 1 , p p . 3 5 - 3 9 . 4 9 . R E N E A U , R . B . , P E T T R Y , D . E . 1 9 7 5 . M o v e m e n t o f C o l i f o r m B a c t e r i a f r o m S e p t i c T a n k E f f l u e n t T h r o u g h S e l e c t e d C o a s t a l P l a i n s o i l s o f V i r g i n i a . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 4 , N o . 1 , p p . 4 1 - 4 4 . 72 5 0 . S A W H N E Y , B . L . , H I L L , D . E . 1 9 7 5 . P h o s p h a t e S o r p t i o n C h a r a c t e r i s t i c s o f S o i l s T r e a t e d w i t h D o m e s t i c W a s t e w a t e r . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 4 , N o . 3 , p p . 3 4 2 - 3 4 6 . 5 1 . S A W H N E Y , B . L . , S T A R R , J . L . 1 9 7 7 . M o v e m e n t o f P h o s p h o r o u s f r o m a S e p t i c T a n k D r a i n F i e l d . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 9 , N o . 1 1 , p p . 2 2 3 9 - 2 2 4 2 . 5 2 . S I K O R A , L . J . , C O R E Y , R . B . 1 9 7 5 . F a t e o f N i t r o g e n a n d P h o s p h o r o u s i n S o i l s U n d e r S e p t i c T a n k W a s t e D i s p o s a l F i e l d s . T r a n s a c t i o n s o f t h e A m e r i c a n S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s , V o l . 5 , p p . 8 6 6 - 8 7 5 . 5 3 . S I M O N S , A . P . , M A G D O F F , F . R . 1 9 7 9 . L a b o r a t o r y E v a l u a t i o n o f D e s i g n P a r a m e t e r s f o r M o u n d S y s t e m d i s p o s a l o f S e p t i c T a n k E f f l u e n t . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 8 , N o . 4 , p p . 4 8 7 - 4 9 2 5 4 . S T E W A R T , L . W . , C A R L I L E , B . L . , C A S S E L , D . K . E v a l u a t i o n o f A l t e r n a t i v e S i m u l a t e d T r e a t m e n t s o f S e p t i c T a n k E f f l u e n t . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 8 , N o . 3 , p p . 3 9 7 - 4 0 3 . 5 5 . S T E W A R T , L . W . , R E N E A U , R . B . 1 9 8 1 . M o v e m e n t o f F e c a l C o l i f o r m B a c t e r i a f r o m S e p t i c T a n k E f f l u e n t T h r o u g h C o a s t a l P l a i n S o i l s w i t h H i g h S e a s o n a l F l u c t u a t i n g G r o u n d w a t e r T a b l e s . P r o c e e d i n g s o f t h e T h i r d N a t i o n a l S y m p o s i u m o n I n d i v i d u a l a n d s m a l l C o m m u n i t y S e w a g e T r e a t m e n t , C h i c a g o . 5 6 . S T E W A R T , L . W . , R E N E A U , R . B . 1 9 8 1 . S p a t i a l a n d T e m p o r a l V a r i a t i o n o f F e c a l C o l i f o r m M o v e m e n t s u r r o u n d i n g S e p t i c T a n k -S o i l A b s o r p t i o n S y s t e m s i n T w o A t l a n t i c C o a s t a l P l a i n S o i l s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 1 0 , N o . 4 , p p . 5 2 8 -5 3 1 . 5 7 . T Y L E R , E . J . , L A A K , R . , M c C O Y , E . , S A N D H U , S . S . 1 9 7 7 . T h e S o i l a s a T r e a t m e n t S y s t e m . Home S e w a g e T r e a t m e n t , P u b l i c a t i o n o f t h e A m e r i c a n S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s , S t . J o s e p h , M i c h i g a n , p p . 5 5 - 7 0 . 5 8 . U N I T E D S T A T E S 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 . 1 9 8 0 . A l t e r n a t i v e S y s t e m s f o r S m a l l C o m m u n i t i e s a n d R u r a l A r e a s . O f f i c e o f W a t e r P r o g r a m O p e r a t i o n s , W a s h i n g t o n , D . C . 5 9 . V I R A R A G H A N , T . , W A R N O C K , R . G . 1 9 7 6 . G r o u n d w a t e r P o l l u t i o n F r o m a S e p t i c T i l e F i e l d . W a t e r , A i r a n d S o i l P o l l u t i o n , V o l . 5 , N o . 3 , p p . 2 8 1 - 2 8 7 . 6 0 . V I R A R A G H A V A N , T . , W A R N O C K , R . G . 1 9 7 6 . T r e a t m e n t E f f i c i e n c y o f S e p t i c T a n k - T i l e S y s t e m . J o u r n a l o f t h e W a t e r P o l l u t i o n C o n t r o l F e d e r a t i o n , V o l . 4 8 , p . 9 3 4 . 6 1 . W A L P O L E , R . E . , M Y E R S , R . H . 1 9 7 8 . P r o b a b i l i t y a n d S t a t i s t i c s f o r E n g i n e e r s a n d S c i e n t i s t s . M a c M i l l a n P u b l i s h i n g C o m p a n y I n c o r p o r a t e d , New Y o r k . 73 6 2 . W I L S O N , S . A , P A E T H , R . C , R O N A Y N E , M . P . 1 9 8 2 . E f f e c t o £ T i l e D r a i n a g e o n D i s p o s a l o f S e p t i c T a n k E f f l u e n t i n W e t S o i l s . J o u r n a l o f E n v i r o n m e n t a l Q u a l i t y , V o l . 1 1 , N o . 3 , p p . 3 7 2 - 3 7 6 . 6 3 . W I N N E B E R G E R , J . H . T . 1 9 7 4 . R y o n ' s S e p t i c T a n k P r a c t i c e s C o r r e c t e d . P r o c e e d i n g s o f t h e N a t i o n a l Home S e w a g e D i s p o s a l S y m p o s i u m . 6 4 . Z I E B E L L , W . A . , A N D E R S O N , J . L . , B O U M A , J . M c C O Y , E . 1 9 7 5 . F e c a l B a c t e r i a : R e m o v a l f r o m S e w a g e b y S o i l s . A m e r i c a n S o c i e t y o f A g r i c u l t u r a l E n g i n e e r s , W i n t e r M e e t i n g . 6 5 . Z I E B E L L , W . A . , N E R O , D . H . , D E I N I N G E R , J . F . , M c C O Y , E . 1 9 7 4 . U s e o f B a c t e r i a i n A s s e s s i n g W a s t e T r e a t m e n t a n d S o i l D i s p o s a l S y s t e m s . N a t i o n a l Home S e w a g e D i s p o s a l S y m p o s i u m . 74 A P P E N D I X 75 P A R T 1 C a l c u l a t i o n o f S t a t i s t i c a l S i g n i f i c a n c e o f M e a n V a l u e s w i t h i n t h e E x p e r i m e n t a l C h a n n e l s ( R e f e r e n c e : I n t r o d u c t i o n t o A d j u s t m e n t s o f S u r v e y i n g M e a s u r e m e n t s , P r a n k i c h ) T e s t i n g o f t w o m e a n s . X = m e a n o f x v a l u e s Y = m e a n o f y v a l u e s S x = s x S y = s y S t a n d a r d e r r o r s f~n J m t = X - Y h a s a p p r o x i m a t e l y t h e s t u d e n t t - d i s t r i b u t i o n \ S x ' f S y 2 -w i t h d e g r e e s o f f r e e d o m v = ( S X 2 + Sy 2 ) - 2 S x 4 + S y 4 n - 1 m - 1 n a n d m a r e t h e n u m b e r o f o b s e r v a t i o n s o f X a n d Y . E x a m p l e : A m m o n i a c o n c e n t r a t i o n s i n l o a m y - s a n d f i l l e d c h a n n e l s w i t h z o n e s o f u n s a t u r a t e d s o i l ( 0 . 9 1 m e t r e s a n d 0 . 4 6 m e t r e s o f u n s a t u r a t e d s o i l ) . X = 0 . 2 0 6 S x = 0 . 0 8 5 S x = 0 . 0 2 5 6 0 . 9 1 m e t r e s y = 0 . 3 5 6 S y = 0 . 0 9 5 S y = 0 . 0 2 8 6 0 . 4 6 m e t r e s t = 1 . 1 8 v = 18 F r o m a t a b l e o f s t u d e n t t - d i s t r i b u t i o n s a v a l u e o f 2 . 1 0 1 i s o b t a i n e d f o r a 9 5 p e r c e n t c o n f i d e n c e i n t e r v a l , t h e r e f o r e i n d i c a t i n g n o s t a t i s t i c a l d i f f e r e n c e i n t h e s e m e a n s . 76 PART 2 C a l c u l a t i o n of C o r r e l a t i o n C o e f f i c i e n t s ( R e f e r e n c e : P r o b a b i l i t y and S t a t i s t i c s f o r E n g i n e e r s and S c i e n t i s t s , Walpole and Myers) Sxx = S x - ( S x)z n Syy = S y - (,£ yf n Sxy = S: xy - S i x S y n r = Sxy JsxxSyy Example: C a l c u l a t i o n f o r othophosphate i n f l u e n t and e f f l u e n t i n sand f i l l e d c h a n n e l s w i t h zones of u n s a t u r a t e d s o i l . x = 38.9 x = 162.2 I n f l u e n t y = 0.155 y = 0.00330 E f f l u e n t xy = 0.694 Sxx = 10.9 Syy = 0.0000898 Sxy = 0.0910 r = 0.92 77 

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