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A field study of a household package treatment plant Gouge, Michael F. 1975

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A FIELD STUDY OF A HOUSEHOLD PACKAGE TREATMENT PLANT by MICHAEL F. GOUGE B.S c , Queen's U n i v e r s i t y at Kingston, 1973 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of C i v i l Engineering We accept t h i s t h e s i s as conforming to /the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA February, 1975 In presenting th i s thesis in par t i a l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i lab le for reference and study. I further agree that permission for extensive copying of th i s thes i s for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th i s thesis fo r f inanc ia l gain shal l not be allowed without my writ ten permission. Department of C i v i l Engineering The Univers i ty of B r i t i s h Columbia Vancouver 8, Canada Date February 15, 1975 ABSTRACT The f i e l d o p eration of an i n d i v i d u a l household aerobic treatment p l a n t was i n v e s t i g a t e d . The treatment p l a n t study was p a r a l l e l e d by a l i t e r a t u r e survey of curren t d i s p o s a l system p r a c t i c e s . I t was found that the Cromaglass type CA5-D aerobic wastewater treatment system produced, under c u r r e n t i n s t a l l a t i o n and o p e r a t i o n p r a c t i c e s , an average e f f l u e n t of 85 mg/1 BOD and 79 mg/1 SS. Under s i m i l a r circumstances, the type CA5-E p l a n t produced an average e f f l u e n t q u a l i t y of 67 mg/1 BOD and 56 mg/1 SS. As n e i t h e r type of p l a n t operated w i t h a VSS c o n c e n t r a t i o n of g r e ater than 150 mg/1, the treatment process cannot be described as a m o d i f i c a t i o n of the a c t i v a t e d sludge system. The l i t e r a t u r e i n d i c a t e s t h a t the mechanisms and processes o c c u r r i n g i n wastewater d i s p o s a l systems are inade-quately understood. As a consequence, no adequate t e s t has yet been developed which i s capable of r e l a t i n g measurable s o i l c o n d i t i o n s to s u i t a b i l i t y f o r a d i s p o s a l f i e l d . However, s e v e r a l authors have suggested that average e f f l u e n t BOD's of approximately 40 mg/1 w i l l be r e q u i r e d to permit a s i g n i f i -cant increase above curren t absorption f i e l d h y d r a u l i c l o a d i n g s . Under present c o n d i t i o n s of i n s t a l l a t i o n , s e r v i c e , o p e r a t i o n , and e f f l u e n t q u a l i t y , i t i s probable t h a t s i g n i f i c a n t r e l a x a t i o n of design c r i t e r i a f o r i n s i t u and imported f i l l d i s p o s a l f i e l d s cannot be permitted f o r the Cromaglass treatment systems. Indexing Terms: aerobic wastewater treatment, e f f l u e n t , BOD SS, wastewater, domestic wastewater treatment - i i i -TABLE OF CONTENTS Page No. LIST OF TABLES i v LIST OF FIGURES v ACKNOWLEDGEMENT v i CHAPTER 1 I n t r o d u c t i o n 1 CHAPTER 2 Un i t Operations 5 > CHAPTER 3 E f f l u e n t Q u a l i t y and General Observations 18 CHAPTER 4 Di s p o s a l Systems - State of the A r t 41 CHAPTER 5 Summary and Recommendations 6 0 REFERENCES 67 APPENDICES 69 - i v -LIST OF TABLES TABLE TITLE PAGE NO. 1 MLVSS In CA5-D P l a n t s 12 2 D i f f e r e n c e Between Mixed Liquor and E f f l u e n t Samples, Type CA5-D P l a n t s 13 3 Mixed Liquor Data - CA5-E P l a n t s 16 4 E f f l u e n t Sampling 19 5 Average E f f l u e n t Q u a l i t y From A l l Uni t s 21 6 E f f l u e n t Q u a l i t y 22 7 E f f l u e n t Q u a l i t y - Nitrogen 26 8 Results of S e t t l i n g of Type D E f f l u e n t 29 9 E f f e c t of Laundry Use on E f f l u e n t Q u a l i t y 31 10 NPS E f f l u e n t Data on Cromaglass Type CA5-D 34 11 E f f e c t of S e t t l i n g i n CA5-E P l a n t s 35 12 Present Design Suggestions f o r S e p t i c Tanks - P e r c o l a t i o n Rate versus Suggested Hydraulic Load 54 13 A p p l i e d E f f l u e n t Q u a l i t y - Thomas (24) 56 LIST OF FIGURES FIGURE TITLE PAGE NO, Cromaglass Type CA5-D Aerobic Wastewater Treatment System 6 Cromaglass Type CA5-E Aerobic Wastewater Treatment System 8 BOD versus TOC, Type D E f f l u e n t ( A l l D Plants) 25 E f f l u e n t BOD versus Hydraulic Loading 2 8 E f f e c t of A e r a t i o n Pump F a i l u r e on E f f l u e n t Q u a l i t y 32 - v i -ACKNOWLEDGEMENT I would l i k e to thank Dr. D.S. Mavinic and Dr. W.K. Oldham f o r t h e i r a s s i s t a n c e i n the o r g a n i z a t i o n of the p r o j e c t and f o r s u p e r v i s i o n of t h i s t h e s i s . Without the p a t i e n t help of Mr. W. B a i l e y and Mr. G. D u f f i e l d of the P r o v i n c i a l Health Branch, t h i s p r o j e c t would not have been p o s s i b l e . Their comments were i n v a l u a b l e . I would a l s o l i k e to express my a p p r e c i a t i o n to others who helped: To Mr. Pat M a r t i n and the s t a f f of Northern P u r i f i -c a t i o n Services L t d . f o r t h e i r t e c h n i c a l a s s i s t a n c e . To Mr. A l Spiede l of the P r o v i n c i a l Chemistry Laboratory f o r the e x t r a e f f o r t he put i n t o the a n a l y s i s . To Dr. J . de V r i e s f o r the background in f o r m a t i o n he s u p p l i e d i n the f i e l d of S o i l Science. -1-CHAPTER I  INTRODUCTION For many years suburban development has been o c c u r r i n g outside of regions served by sewer systems. In the past, wastewater management i n these areas has been suppli e d by the f a m i l i a r s e p t i c tank-absorption f i e l d system. Where la r g e l o t s are p e r m i s s i b l e and s o i l c o n d i t i o n s acceptable, t h i s system provides low c o s t , low maintenance treatment and d i s p o s a l . However, smaller l o t s i z e s and adverse s o i l or t e r r a i n c h a r a c t e r i s t i c s , have created a demand f o r a treatment system capable of adequately d i s p o s i n g of wastewater under these constrained c o n d i t i o n s . B a i l e y and Wallman (1) present a review of a few of the many systems which have been o f f e r e d i n response to t h i s demand.* Most of the systems u t i l i z e aerobic b i o l o g i c a l treatment but do not provide f o r d i s p o s a l of the e f f l u e n t . In general, aerobic treatment on an i n d i v i d u a l household s c a l e has not had widespread success. Many of the proposed p l a n t s have not survived the f i r s t stages of the e v o l u t i o n a r y design. Those th a t have proceeded to the workable p l a n t stage have, i n general, yet to overcome problems of r e l i a b i l i t y , s e r v i c e , i n s t a l l a t i o n , p a r t s i n v e n t o r i e s and p u b l i c acceptance. *Note: Because most of the systems proposed are of a patented, and t h e r e f o r e somewhat unique, design and because the o p e r a t i o n a l c h a r a c t e r i s t i c s have been t e s t e d under such v a r i e d circumstances no comparison w i t h other household aerobic wastewater treatment systems w i l l be made. However, i n t e r e s t i n g data does e x i s t (22,23). -2-The poor s u r v i v a l s t a t i s t i c s of these f a c i l i t i e s are not s u r p r i s i n g i n l i g h t of the design c r i t e r i a . The v a r i a t i o n i n wastewater c h a r a c t e r i s t i c s from household to household and even hour to hour w i t h i n one household i s not only immense, but completely unpredictable. Combined w i t h the t e c h n i c a l problems of small s c a l e treatment p l a n t design, t h i s makes design of a rugged r e l i a b l e u n i t very d i f f i c u l t . The only household-scale aerobic waste treatment p l a n t c u r r e n t l y a v a i l a b l e i n B r i t i s h Columbia i s the Cromaglass* Aerobic Wastewater Treatment System. C u r r e n t l y , no u n i f i e d treatment and d i s p o s a l system i s a v a i l a b l e . The Cromaglass system i n B r i t i s h Columbia has been undergoing e v o l u t i o n a r y development f o r approximately four years. The current type CA5-E p l a n t s are the most s o p h i s t i c a t e d u n i t s to emerge from the sequence thus f a r . Undoubtably, a d d i t i o n a l changes w i l l be made i n the f u t u r e . Although Cromaglass p l a n t s have been i n operation* f o r a. number of years, l i t t l e i n f o r m a t i o n , other than t h a t provided by the manufacturer, i s a v a i l a b l e on t h e i r f i e l d o p e r a tion. Normally the manufacturer does not p a r t i c i p a t e d i r e c t l y i n the i n s t a l l a t i o n , maintenance, or operation of the p l a n t s . As each of these f u n c t i o n s can, and o f t e n i s , performed by d i f f e r e n t groups, many people have an e f f e c t on the eventual operating c o n d i t i o n s of the p l a n t . I t was the purpose of t h i s study to i n v e s t i g a t e the performance of *Note: Cromaglass i s the r e g i s t e r e d trademark of Northern P u r i f i c a t i o n S e r vices L t d . , North Vancouver, B.C. -3-treatment u n i t s t h a t were subject to the normal sequence of s a l e , i n s t a l l a t i o n , hook-up to the t i l e f i e l d , and f i n a l l y o p eration by the householder. To ensure the data was r e p r e s e n t a t i v e of f i e l d experience, d i s r u p t i o n of household a c t i v i t i e s was minimized. In a d d i t i o n , no e x t r a o r d i n a r y a c t i o n was taken by r e g u l a t o r y , maintenance or manufacturing agencies during the sampling p e r i o d . The p l a n t s chosen f o r sampling were s e l e c t e d on the b a s i s of the c h a r a c t e r i s t i c s of the f a m i l y occupying the house. None of the p l a n t s was examined before the s e l e c t i o n of sampling s i t e s was made. During the sampling p e r i o d a l l of the t h i r t y p l a n t s , from which the 15 t e s t e d p l a n t s were chosen, were v i s u a l l y examined. Ge n e r a l l y , these examinations r e i n f o r c e d the contention t h a t the sampled p l a n t s were repre-s e n t a t i v e of operations i n tha t l o c a l i t y . The f i e l d t e s t i n g of treatment systems was comple-mented by a l i t e r a t u r e survey of d i s p o s a l system design. The greater p o r t i o n of the l i t e r a t u r e i s d i r e c t e d toward the design of s e p t i c tank absorption systems. These i n c l u d e i n s i t u f i e l d s , f i e l d s i n imported m a t e r i a l , w e l l s or p i t s and sand beds. Some data f o r the design of e v a p o t r a n s p i r a t i o n systems was a l s o a v a i l a b l e . However, t h i s m a t e r i a l i s not yet w e l l documented nor proven. Throughout t h i s r e p o r t , two p o i n t s should be kept i n mind. I t should be remembered th a t as system complexity a and system s t r e s s i n c r e a s e , cost w i l l i n e v i t a b l y increase a l s o . Secondly, i t should be emphasized th a t the data i n t h i s , r e p o r t - 4 -on treatment system operation and the background m a t e r i a l on d i s p o s a l systems from the l i t e r a t u r e provides, at best, a skeleton upon which to hang an o v e r a l l design. As design c r i t e r i a become more constrained there w i l l be a greater need to f i l l i n d e t a i l s . -5-CHAPTER 2  UNIT OPERATIONS I. Cromaglass Aerobic Wastewater Treatment System The treatment p l a n t s sampled during t h i s survey were a l l Cromaglass S e r i e s CA5 u n i t s , manufactured by Northern P u r i f i c a t i o n S e r vices L t d . The two l a t e s t designs i n an e v o l u t i o n a r y sequence were examined. In terms of a c t u a l c o n f i g u r a t i o n , however, three d i s t i n c t types of p l a n t s were stud i e d . A. CA5-D The CA5-D (type D) p l a n t was s o l d up to December 1973. The general p l a n t layout i s i l l u s t r a t e d i n Figure 1. The outer s h e l l and s e t t l i n g tank are of f i b e r g l a s s c o n s t r u c t i o n and the pumps are f u l l y submersible, sealed u n i t s . Under normal c o n d i t i o n s the p l a n t operates w i t h a t o t a l l i q u i d volume of approximately 330 Im p e r i a l g a l l o n s . I n f l u e n t enters the primary s o l i d s removal chamber from the house sewer. The wastewater then flows down through a screen i n t o the a e r a t i o n chamber. The a e r a t i o n pump p i c k s up mixed l i q u o r and c i r c u l a t e s i t up through a b l e e d - o f f connection and a v e n t u r i and back i n t o the a e r a t i o n tank. A p l a s t i c tube extending from the v e n t u r i to the basement of the house provides the a i r supply. Intimate contact of the a i r and wastewater i s achieved as the mixture i s i n j e c t e d back i n t o the mixed l i q u o r . The b l e e d - o f f connection allows some of the mixed l i q u o r to be continuously t r a n s f e r r e d to the s e t t l i n g tank. -6-1 aeration pump 2 discharge pump 3 venturi 4 air supply line 5 transfer line (to settling tank) 6 raw waste inlet 7 discharge line 8 float valve - for solids return 9 overflow 10 overflow (to disposal) 11 access manholes (with covers) 12 solids retention screen 13 aeration tank 14 settling tank 15 junction box FIGURE 1 CROMAGLASS TYPE CA5-D AEROBIC WASTEWATER TREATMENT SYSTEM - 7 -When l i q u i d l e v e l s i n the a e r a t i o n and s e t t l i n g tanks have e q u i l i b r a t e d , a f l o a t operated v a l v e , on the bottom of the s e t t l i n g chamber, opens to al l o w s o l i d s to r e t u r n to the a e r a t i o n chamber. The discharge pump i s c o n t r o l l e d by a f l o a t v a l v e , so th a t discharge takes place only a f t e r the l i q u i d l e v e l i n the whole p l a n t has reached the discharge depth. Continuous t r a n s f e r from the a e r a t i o n tank to the s e t t l i n g tank occurs at a r a t e of 1.5 to 4 gpm. The batch e f f l u e n t discharge, of approximately 48 I g a l , occurs i n 1.5 to 3.0 minutes. B. CA5-E The type E u n i t s d i f f e r from the o l d e r type D p l a n t s p r i m a r i l y i n t h e i r mode of ope r a t i o n . As f i g u r e 2 i n d i c a t e s , only the s p a t i a l arrangement of the components i s a l t e r e d . The other p h y s i c a l s p e c i f i c a t i o n s are i d e n t i c a l to the type D p l a n t s . The s i g n i f i c a n t change i n the type E p l a n t s i s the i n t r o d u c t i o n of i n t e r m i t t e n t o p e ration. C o n t r o l over the a e r a t i o n and discharge pumps i s e x e r c i s e d by a remotely mounted timer. The timer c o n t r o l s the mode of operation and the length of time the p l a n t operates i n a p a r t i c u l a r mode. These p l a n t s have two o p e r a t i o n a l modes. One i s the same as that which occurs i n the type D p l a n t s , t h a t i s , continuous a e r a t i o n and t r a n s f e r to the s e t t l i n g tank. The other mode i s complete quiescence throughout the p l a n t . This second mode i s intended to provide a quiescent s e t t l i n g p e r i o d before discharge to d i s p o s a l f a c i l i t i e s . Discharge occurs near the -8-1 aeration pump 2 discharge pump 3 venturi 4 transfer line (to settling tank) 5 air supply line 6 raw waste inlet 7 discharge line 8 float valve - for solids return 9 overflow 10 overf low (to disposal) 11 access manholes (with covers) 12 solids retention screen 13 aeration tank 14 settling tank 15 remotely mounted t imer control FIGURE 2 CROMAGLASS TYPE CA5-E AEROBIC WASTEWATER TREATMENT SYSTEM -9-end of the s e t t l i n g p e r i o d j u s t before a e r a t i o n begins again. Any d e s i r e d length of s e t t l i n g or a e r a t i o n p e r i o d can be achieved by a d j u s t i n g the timer. In a d d i t i o n to p r o v i d i n g improved s e t t l i n g c o n d i t i o n s , i n t e r m i t t e n t operation reduces power consumption and increases a e r a t i o n pump l i f e . The other major change i n the type E p l a n t s , s p a t i a l arrangement, was i n s t i g a t e d to increase mixing e f f i c i e n c y i n the a e r a t i o n tank. C. CA5-E(D) This u n i t appeared as a r e s u l t of a temporary shortage of timer c o n t r o l s . The p h y s i c a l c o n f i g u r a t i o n i s t h a t of a CA5-E p l a n t but i t operates continuously as does the CA5-D. These u n i t s are now being converted to CA5-E u n i t s w i t h the i n s t a l l a t i o n of the timer c o n t r o l by the manufacturer. As these p l a n t s functioned i n the same way as the CA5-D u n i t s , i t was expected t h a t the e f f l u e n t they produce would be s i m i l a r to t h a t of the type D p l a n t s . Houses numbered I, 2,4,9, and 15 had the CA5-E(D) p l a n t s . As Table 6 shows, these u n i t s do not appear to be s i g n i f i c a n t l y d i f f e r e n t than the type D p l a n t s i n terms of e f f l u e n t q u a l i t y . I I . Treatment Design A. CA5-D The design i s based on the extended a e r a t i o n or aerobic s t a b i l i z a t i o n p r i n c i p l e w i t h i n t e r m i t t e n t batch d i s -charge. Input i s u n c o n t r o l l e d and t h e r e f o r e a l s o i n t e r m i t t e n t i n nature. P r o v i s i o n has been made f o r the r e t u r n of s o l i d s separated from the e f f l u e n t . -10-The d e s c r i p t i o n of the u n i t operation as extended a e r a t i o n i s t h e o r e t i c a l only. In f a c t , the operation of these p l a n t s i s impossible to analyze w i t h i n the framework of con-v e n t i o n a l b i o l o g i c a l treatment systems. To begin w i t h , the p l a n t s are subjected to a much more i r r e g u l a r "dosing" p a t t e r n than any l a r g e r s c a l e system. Hyd r a u l i c loadings can vary from 0 to 20 gpm inst a n t a n e o u s l y , w i t h great ranges i n the t o t a l volume of a s i n g l e input surge. Organic loads show even more dramatic peaks. As these p l a n t s have only a very rudimentary f a c i l i t y f o r p r o v i d i n g load e q u a l i z a t i o n , the use of any average values of i n f l u e n t c h a r a c t e r i s t i c s can be completely misleading. The i n s i g n i f i c a n t amount of MLVSS (see Table 1) precludes the i n c l u s i o n of these p l a n t s w i t h any of the v a r i a -t i o n s of the a c t i v a t e d sludge process. The t i m i n g of the batch discharge i s c o n t r o l l e d by the i n f l u e n t volume. Thus, the h y d r a u l i c residence time i s a l s o a f u n c t i o n of i n f l o w volume. The r e l a t i v e l y small working volume of the p l a n t s f a i l s to damp out f l u c t u a t i n g input volumes and thus average a e r a t i o n time can be h i g h l y v a r i a b l e . However, w i t h these a n a l y t i c a l shortcomings i n mind, some g e n e r a l i z a t i o n s can be made about the operations. The 330 g a l l o n o p e r a t i n g volume provides an average h y d r a u l i c residence time of 44 hours f o r a f a m i l y of four (see Appendix 2). This p e r i o d i s longer than the 18 to 36 hours g e n e r a l l y recommended f o r l a r g e r p l a n t s (18). In the -11-l a r g e r extended a e r a t i o n p l a n t s , a MLVSS of 3000 to 6000 mg/1 can be maintained under organic loadings of 10 to 25 3 l b BOD/day/1000 f t of a e r a t i o n tank volume. The continuous a e r a t i o n of the type D p l a n t s probably r e s u l t s i n short periods of overloaded and r e l a t i v e l y long periods of underloaded o p e r a t i o n . Appendix 2 suggests an organic load of 0.106 l b BOD/capita/day can be expected on the average (without garbage g r i n d i n g ) . Four persons would then be expected to provide 0.424 l b BOD/day. Based on a 3 design organic l o a d i n g range of 0.10 to 0.25 l b BOD/1000 f t /day a f a m i l y of four would r e q u i r e between 265 and 105 g a l l o n s of a e r a t i o n tank volume. The e f f e c t i v e a e r a t i o n chamber volume of the Cromaglass p l a n t s i s approximately 220 g a l l o n s . Thus, f o r any household of l e s s than f i v e people, the u n i t w i l l be operating at very low organic loadings most, i f not a l l , of the time. These low l o a d i n g c o n d i t i o n s and long h y d r a u l i c residence times could r e s u l t i n the d e s t r u c t i o n of v o l a t i l e s o l i d s by a u t o - o x i d a t i o n . The m a j o r i t y of the s o l i d s , formed during periods of high organic l o a d i n g , are o x i d i z e d during the low load periods at mid-day and at n i g h t . The low TSS and VSS concentrations found i n the mixed l i q u o r (Table 1) are not, then, unexpected. -12-TABLE 1  MLVSS IN CA5-D PLANTS House No. of Number Samples MLVSS, mg/1 high average low 1 4 105 83 68 3 2 86 69 52 4 6 110 64 32 5 4 101 96 87 6 5 139 87 58 7 4 70 54 28 8 4 100 77 68 9 1 - - 28 These low MLVSS concentrations emphasize th a t the system does not f u n c t i o n by c o n t a c t i n g incoming wastes w i t h l a r g e concentrated volumes of a c t i v e microorganisms. The treatment mechanism apparently c o n s i s t s of d i l u t i o n of the r e l a t i v e l y small volumes of incoming wastewater, to reduce the c o n c e n t r a t i o n , and then o x i d a t i o n over a r e l a t i v e l y long a e r a t i o n p e r i o d . Both o x i d a t i o n and discharge of s o l i d s i n the e f f l u e n t , c o n t r i b u t e to the maintenance of low s o l i d s l e v e l s . The high-rate t r a n s f e r from the a e r a t i o n to s e t t l i n g tank (measured at approximately 2 to 4 gpm) induces a great deal of turbulence i n the s e t t l i n g tank. The r e s u l t i s t h a t v i r t u a l l y no s o l i d s -13-removal i s a t t a i n e d and consequently no accumulated s o l i d s are a v a i l a b l e f o r r e t u r n to the a e r a t i o n chamber. That t h i s does occur can be seen from Table 2, which l i s t s the mean d i f f e r e n c e between simultaneous e f f l u e n t and mixed l i q u o r samples. TABLE 2 DIFFERENCE BETWEEN MIXED LIQUOR AND EFFLUENT SAMPLES TYPE CA5-D PLANTS standard d e v i a t i o n parameter mean d i f f e r e n c e * of d i f f e r e n c e BOD -0.6667 mg/1 20.1090 SS -0.1220 mg/1 ' 42.6639 VSS -6.9048 mg/1 17.1520 COD -15.7778 mg/1 35.2909 *mean d i f f e r e n c e = mean of ( S e t t l i n g Tank Concentration - Mixed Liquor Concentration) The submersible pumps used i n these p l a n t s operate at approximately 45 gpm. The shear w i t h i n the pumps and i n the v e n t u r i used f o r a e r a t i o n i s probably s u f f i c i e n t to d i s i n t e g r a t e any la r g e f l o e s of a c t i v a t e d sludge. I f the s e t t l i n g v e l o c i t y of the r e s u l t a n t f i n e f l o e were slow enough, s i g n i f i c a n t l y g r eater s o l i d s concentrations may be discharged i n the e f f l u e n t . The sewage i n l e t from the house discharges i n t o a -14-primary chamber, designed to provide some i n i t i a l s o l i d s r e t e n t i o n . The waste then flows through a screen i n t o the a e r a t i o n chamber. No attempt was made to measure the s o l i d s build-up i n t h i s chamber. However, i t may provide some red u c t i o n i n the s o l i d s loading on the system. The r e t a i n e d s o l i d s would t h e o r e t i c a l l y decompose.aerobically u n t i l small enough to escape through the screen i n t o the a e r a t i o n chamber. In l i g h t of the g e n e r a l l y underloaded c o n d i t i o n of these p l a n t s t h i s primary treatment may not be d e s i r a b l e . When the a e r a t i o n pump was operating at f u l l c a p a c i t y , d i s s o l v e d oxygen concentrations i n the mixed l i q u o r were i n the range of 1.0 to 8 mg/1. Often, however, the a e r a t i o n pumps would become p a r t i a l l y clogged, r e s u l t i n g i n a decrease i n d i s s o l v e d oxygen concentrations to the 0 to 5 mg/1 range. U s u a l l y , a clogged pump would c l e a r i t s e l f w i t h i n a day or two but some remained p a r t i a l l y clogged f o r a week. Oc c a s i o n a l l y the p e r s i s t e n c e of low d i s s o l v e d oxygen c o n d i t i o n s was s u f f i c i e n t to produce enough undesirable odor to cause the homeowner to c a l l i n s e r v i c e personnel. V o l a t i l e s o l i d s u s u a l l y made up 65 to 90 percent of the TSS but samples as low as 50 percent were recorded. As most of the p l a n t s had been operating from 6 to 15 months, the buildup of i n o r g a n i c m a t e r i a l does not appear to be a problem. This i s probably the r e s u l t of the discharge of s o l i d s w i t h the e f f l u e n t . B. CA5-E The p h y s i c a l and o p e r a t i o n a l changes i n s t i t u t e d -15-i n the CA5-E p l a n t s do apparently r e s u l t i n improved e f f l u e n t q u a l i t y (Chapter 3). The most s i g n i f i c a n t change i n terms of u n i t operations, the i n t r o d u c t i o n of i n t e r m i t t e n t a e r a t i o n , does have at l e a s t one undesirable side e f f e c t . In the p l a n t s included i n t h i s survey, the timer was set to give approximately a two hour s e t t l i n g p e r i o d . During t h i s time, there i s no i n t e r r u p t i o n of the p e r i o d i c i n p u t s . B i o l o g i c a l degradation of the e x i s t i n g and a p p l i e d organic loads continues, w i t h a r e s u l t a n t decrease i n d i s s o l v e d oxygen c o n c e n t r a t i o n . In some i n s t a n c e s , t h i s r e s u l t e d i n anaerobic c o n d i t i o n s r e l a t i v e l y soon a f t e r a e r a t i o n ceased. The presence of anaerobic c o n d i t i o n s was c o r r e l a t e d w i t h the load i n g of the p l a n t t o the extent t h a t i t only appeared i n p l a n t s s e r v i n g f i v e or more people. D i s s o l v e d oxygen concentrations returned to aerobic l e v e l s (5 to 7 mg/1) w i t h i n a few minutes of the resumption of a e r a t i o n . Thus, the oxygen d e f i c i t , created during the anaerobic p e r i o d (which l a s t e d as long as an hour), probably d i d not adversely a f f e c t the treatment process. The unpleasant odor however, was a source of householder complaints. Without exception, discharge occurred from 15 to 45 minutes before a e r a t i o n began. Because of the unpleasant odor a s s o c i a t e d w i t h the anaerobic c o n d i t i o n s prevailing..at the end of the s e t t l i n g p e r i o d , i t would be advantageous to begin a e r a t i o n immediately a f t e r the discharge. During the a e r a t i o n c y c l e , these p l a n t s f u n c t i o n s i m i l a r l y to the CA5-D u n i t s and e x h i b i t s i m i l a r c h a r a c t e r i s t i c s . - 1 6 -The average mixed l i q u o r data, shown i n Table 3, e x h i b i t s low VSS concentrations as were found i n the type D p l a n t s . Even though the a e r a t i o n pump was only operating f o r one hour out of every three, i t appears the s o l i d s were e f f e c t i v e l y d i s i n t e g r a t e d . TABLE 3 MIXED LIQUOR DATA - CA5-E PLANTS house average BOD average SS average VSS # mg/1 mg/1 mg/1 12 66 65 62 13 97 81 71 14 43 41 41 -17-SUMMARY The problems, afore discussed, concerning the a n a l y s i s of the u n i t o p e r a t i o n s , manifest themselves when ana l y z i n g the e f f l u e n t q u a l i t y data a l s o . Throughout these d i s c u s s i o n s , average values of parameters have been used, mainly because of a lack of data on i n f l u e n t c o n d i t i o n s and the consequent d i f f i c u l t y of a n a l y z i n g time s e r i e s data. However, re g a r d l e s s of the i n f l u e n t c h a r a c t e r i s t i c s , i t i s the q u a l i t y of the e f f l u e n t which governs d i s p o s a l system design. -18-CHAPTER 3 EFFLUENT QUALITY AND GENERAL OBSERVATIONS I. Sampling The primary purpose of t h i s i n v e s t i g a t i o n was to o b t a i n data on the q u a l i t y of e f f l u e n t to be expected under f i e l d c o n d i t i o n s . A t o t a l of f i f t e e n households, using Cromaglass systems, were surveyed during June, J u l y and August, 1974. The study was concentrated i n the type D u n i t s as i t was d i f f i c u l t to f i n d type E p l a n t s which were s u i t a b l e . However, f i v e type E p l a n t s were included i n the sampling program. E f f l u e n t samples were taken from the s e t t l i n g tanks. This was necessary because, i n a l l but two of the systems, the e n t i r e d i s p o s a l f i e l d , i n c l u d i n g the d i s t r i b u t i o n box, was i n a c c e s s a b l e . Samples were taken approximately s i x to e i g h t inches below the l i q u i d surface. G e n e r a l l y , t h i s depth i s approximately four to s i x inches above the discharge pump in t a k e . The sampling device had a l i d which was opened only a small amount a f t e r the device had been submerged. This prevented the i n f l o w of l i q u i d above the d e s i r e d sampling depth and allowed the i n f l o w r a t e to be c o n t r o l l e d . Turbulence i n the s e t t l i n g tank was minimized by t h i s procedure. Two type D p l a n t s were sampled simultaneously from the d i s t r i b u t i o n box and the s e t t l i n g tank. The r e s u l t s of t h i s sampling, as shown i n Table 4, i n d i c a t e d t h a t the s e t t l i n g tank sampling procedure was r e p r e s e n t a t i v e of the e f f l u e n t -19-which enters the t i l e f i e l d . * TABLE 4  EFFLUENT SAMPLING D i s t r i b u t i o n Box S e t t l i n g Tank D i f f e r e n c e BOD mg/1 SS mg/1 BOD mg/1 SS mg/1 A BOD mg/1 A SS mg/1 102 46 103 82 -1 -36 110 94 • 105 100 5 -6 105 88 105 72 0 16 78 106 85 105 -7 1 81 39 80 46 1 -7 63 39 63 36 0 3 86 30 78 42 8 -48 197 49 143 48 54 -1 standard average d e v i a t i o n of d i f f e r e n c e d i f f e r e n c e 7.5 19.29 -9.5 21.48 As noted e a r l i e r , the frequency of discharge of these p l a n t s i s regulated by the i n f l o w volume. Thus, i t i s not p o s s i b l e to p r e d i c t when the u n i t s w i l l discharge to the t i l e f i e l d . Without automatic sampling devices, i t becomes very d i f f i c u l t to c o l l e c t samples p r e c i s e l y when the p l a n t *Note: For s i m p l i c i t y and c l a r i t y most of the concepts presented are discussed i n terms of BOD only. Many of the same comments apply to SS, COD, and other, q u a l i t y parameters. -20-discharges. In order to develop a p r o f i l e of the p l a n t s o p e r a t i o n , over a 16 hour p e r i o d , sampling of the type D u n i t s was c a r r i e d out at one h a l f hour i n t e r v a l s . In p l a n t s s e r v i n g homes where moderate to high water use was o c c u r r i n g , t h i s sampling p e r i o d o f t e n c o i n c i d e d w i t h the discharge c y c l e . However, when water use was low, s e v e r a l e f f l u e n t samples may have been taken f o r each discharge to the t i l e f i e l d . Obviously, i f e f f l u e n t q u a l i t y was c o r r e l a t e d w i t h water use (h y d r a u l i c l o a d ) , t h i s procedure could b i a s the r e s u l t s c o n s i d e r a b l y . However, as w i l l be discussed l a t e r , i t was found t h a t h y d r a u l i c l o a d i n g was not c o r r e l a t e d w i t h e f f l u e n t q u a l i t y . Thus, t h i s sampling procedure should not bia s the r e s u l t s . I t should be emphasized t h a t most e f f l u e n t samples were a c t u a l l y taken during discharge to the t i l e f i e l d . During the course of the summer, many a e r a t i o n pump f a i l u r e s were observed. The e a r l y package p l a n t s came w i t h a metal housed a e r a t i o n pump. These were l a t e r replaced by pumps w i t h a p l a s t i c housing. These p l a s t i c pumps e x h i b i t e d such a high f a i l u r e r a t e t h a t Northern P u r i f i c a t i o n returned to the use of the metal housed pumps. Many of the pumps which f a i l e d during the summer were p l a s t i c u n i t s . During f a i l u r e periods and f o r one week a f t e r replacement, these p l a n t s were not sampled. One u n i t was sampled during and j u s t a f t e r the f a i l u r e and replacement of a metal housed pump. Thus, the e f f l u e n t values f o r house number four have -21-s e v e r a l high values. Number four was not the only house to experience the f a i l u r e of a metal pump. The p r a c t i c e of not sampling u n i t s during pump f a i l u r e would tend to make the o v e r a l l e f f l u e n t q u a l i t y presented i n t h i s r e p o r t , higher than a c t u a l l y occurred. Thus, i f the r e s u l t s presented are biased, they would tend to be of somewhat b e t t e r q u a l i t y than can be expected i n normal f i e l d o p e r a t i o n . For the type E u n i t s , only the r e s u l t s from samples taken during discharge to the t i l e f i e l d are reported. In a d d i t i o n t o a d i s c u s s i o n of the e f f l u e n t q u a l i t y data, t h i s chapter contains some general notes about f i e l d performance. I I . Overview A summary of the e f f l u e n t data i s presented i n Table 6. Some average values are given i n Table 5. TABLE 5 AVERAGE EFFLUENT QUALITY FROM ALL UNITS average median BOD mg/1 SS mg/1 BOD mg/1 SS mg/1 type D 85 79 80 75 type E 67 56 63 56 Note: Regulatory standards are o f t e n based on average e f f l u e n t q u a l i t y . TABLE 6 EFFLUENT QUALITY House Percent of the time th a t the e f f l u e n t Number of number q u a l i t y exceeds the st a t e d l e v e l * * samples 50/50 * 70/7 0"- 125/125 : BOD SS BOD SS BOD SS BOD SS type D u n i t s 1 100 67 87 52 17 2 46 42 2 93 93 93 71 0 29 14 14 3 68 92 49 46 0 0 37 37 4 69 51 64 40 51 29 39 35 5 93 91 73 64 0 9 15 11 6 64 78 14 50 0 6 22 18 7 12 47 6 47 0 24 17 17 8 100 100 89 58 0 0 19 19 9 0 75 0 0 0 0 4 4 15 0 0 0 0 0 0 1 1 ;ype E u n i t s 12 100 50 50 50 0 0 2*** • 2 13 100 100 67 33 0 0 3 3 14 0 0 0 0 0 0 2 2 16 100 0 100 0 0 0 1 1 17 50 100 0 0 0 0 2 2 * A 50/50 e f f l u e n t q u a l i t y was used by the B r i t i s h Columbia Health Branch i n i t s G u i d e l i n e s f o r Package Treatment Systems. A 70/70 e f f l u e n t q u a l i t y corresponds to an 80% removal of BOD and SS from an i n f l u e n t of 350 mg/1 (or 72% from an i n f l u e n t of 250 mg/1). -23-TABLE 6 - Cont. A 125/125 e f f l u e n t q u a l i t y represents a 50% removal from an i n f l u e n t of 250 mg/1 ( s e p t i c tank e f f l u e n t ) ** f o r example the e f f l u e n t from house number 3 exceeded 5 0 mg/1 BOD 68% of the time *** these are discharge samples only The type E u n i t s produce a b e t t e r q u a l i t y e f f l u e n t than do the o l d e r type D p l a n t s . However, n e i t h e r type i s capable of c o n s i s t e n t l y producing e f f l u e n t s i n the range of 30 to 4 0 mg/1 BOD. The e f f l u e n t of the type D p l a n t s i s not d i s s i m i l a r from th a t expected from a pr o p e r l y f u n c t i o n i n g s e p t i c tank (1, 15, 18). The f o l l o w i n g d i s c u s s i o n r e l a t e s an attempt to analyze the data i n more d e t a i l . The a n a l y s i s i s concentrated on the type D u n i t s f i r s t and then e x t r a p o l a t e d to the type E p l a n t s . A. E f f l u e n t Q u a l i t y - Type D The great v a r i a t i o n of the data from hour to hour and day to day make i t d i f f i c u l t to recognize any s i g n i f i c a n t c o r r e l a t i o n s w i t h other events. Another compounding f a c t o r i s the v a r i a t i o n of l a g times between i n f l u e n t events and e f f l u e n t discharge, as the input flow r a t e v a r i e s . The only statement t h a t can be made w i t h c e r t a i n t y i s tha t i t i s impossible to p r e d i c t the e f f l u e n t q u a l i t y of a p a r t i c u l a r p l a n t based on previous data, f a m i l y a c t i v i t i e s , other u n i t s performance or other measurable c r i t e r i a or combination thereof. 1. S p e c i f i c E f f l u e n t C h a r a c t e r i s t i c s The general e f f l u e n t q u a l i t y has been described i n -24-Tables 5 and 6 i n terms of BODr and SS. In a d d i t i o n to these o r o u t i n e l y performed analyses, some other t e s t s were run i n t e r m i t t e n t l y to provide a more complete d e s c r i p t i o n of the . e f f l u e n t c h a r a c t e r i s t i c s . One of the anomalies of the data i s the apparently u n e x p l i c a b l e peaks which occur i n a time s e r i e s of samples. For example, i n 80 percent of the sampling sequences one or two BOD values were s i g n i f i c a n t l y higher or lower than the average. These peaks were not c o r r e l a t e d w i t h i n f l u e n t events. One p o s s i b l e e xplanation was t h a t n i t r i f i c a t i o n was beginning at or near the f i v e day mark i n the BOD t e s t . This would r e s u l t i n the odd high or low BOD depending on how the samples were t r e a t e d . To t e s t t h i s hypothesis 5, 8 and 11 day BOD t e s t s were run on the same samples. Although the r e s u l t s were i n c o n c l u s i v e , an average increase of 54 percent above the 5 day values was found i n the 11 day t e s t s . That i s , the BODj. i s l e s s than 50 percent of the u l t i m a t e BOD. E f f l u e n t COD ranged from 109 to 330 mg/1 and averaged 218 mg/1 over a l l p l a n t s . The BOD to COD r a t i o ranged from 0.181 to 1.083 and averaged 0.432. In the e a r l y stages of the program, an attempt was made to c o r r e l a t e TOC w i t h BOD. As Figure.3 i l l u s t r a t e s , no such c o r r e l a t i o n could be found. In addition,...no . c o r r e l a t i o n was found between TOC and BOD w i t h i n a p a r t i c u l a r p l a n t . I t can be concluded t h a t n e i t h e r the TOC nor the COD t e s t can be used to estimate the BOD i n the e f f l u e n t of these p l a n t s . With respect to temperature, values ranged from 140 120 100 BOD 5 mg^ 80 60 — 40 — : 20 — 0 20 4 0 6 0 80 TOC mg/l 100 120 140 FIGURE 3 - BOD VERSUS TOC, TYPE D EFFLUENT (ALL D PLANTS) -26-22 to 31 °C wit h most p l a n t s averaging 25 °C. 2. N u t r i e n t s Phosphorus analyses were not conducted as t h i s data i s w e l l documented i n other sources (16). I t i s reasonable to expect, as phosphorus compounds are not v o l a t i l e and sludge removal i s not p r a c t i c e d , t h a t a f t e r a p e r i o d of op e r a t i o n , a q u a s i - e q u i l i b r i u m s t a t e w i l l be reached i n which a l l the phosphorus e n t e r i n g the p l a n t w i l l be discharged. To o b t a i n an order-of-magnitude estimate of e f f l u e n t n i t r o g e n c o n c e n t r a t i o n s , t e s t s were run on s i x samples, from two households. As Table 7 i l l u s t r a t e s , s i g n i f i c a n t n i t r a t e and n i t r i t e concentrations were recorded i n some samples (see a l s o d i s c u s s i o n of n i t r i t e i n Appendix 3). As Table 7 shows, TKN to BOD r a t i o s were s i g n i f i c a n t l y higher than t h a t normally considered necessary f o r a c t i v e m i c r o b i a l degradation. Thus, i f groundwater contamination i s a p o t e n t i a l problem, precaution w i l l be necessary i n t i l e f i e l d design to ensure d e n i t r i f i c a t i o n . TABLE 7 EFFLUENT QUALITY - NITROGEN, mg/lN House BOD5 NH 3 NO., N0 2 ORN TKN BOD/TKN # mg/1 mg/1 mg/1 mg/1 mg/1 mg/1 3 82 23.3 1.3 1.9 8.7 32 2.6 121 21.3 1.3 2.0 14.7 36 3.4 104 19.3 2.5 2.9 13.7 33 3.2 6 66 22.5 0.05 0.103 14.5 37 1.8 65 23.8 0.04 0.107 10.2 34 1.9 60 23.8 0.05 0.129 9.2 33 1.8 -27-3. D i s s o l v e d Oxygen Gen e r a l l y , d i s s o l v e d oxygen concentrations i n the e f f l u e n t were high. Unless the a e r a t i o n pump was p a r t i a l l y clogged, concentrations of 3 to 7 mg/1 were normal. Pump clog g i n g or f a i l u r e r e s u l t e d i n anaerobic e f f l u e n t a f t e r a r e l a t i v e l y short time. Many of the p l a n t s had broken, l e a k i n g , or missing t r a n s f e r l i n e components, which o f t e n r e s u l t e d i n s i g n i f i c a n t amounts of spray a e r a t i o n . This a d d i t i o n a l a e r a t i o n was s u f f i c i e n t to maintain high d i s s o l v e d oxygen co n c e n t r a t i o n s , even i n p l a n t s w i t h p a r t i a l l y clogged a e r a t i o n pumps. No c o r r e l a t i o n could be found between d a i l y average e f f l u e n t q u a l i t y and mixed l i q u o r d i s s o l v e d oxygen concentra-t i o n s when the a e r a t i o n pump was operating normally. The e f f e c t of a e r a t i o n pump f a i l u r e i s discussed l a t e r . 4. E f f l u e n t Q u a l i t y Versus Hydraulic Loading F a c i l i t i e s were not a v a i l a b l e f o r sampling the i n f l u e n t f o r organic content or volume. However, bi-monthly water consumption f i g u r e s were a v a i l a b l e f o r each household (Appendix 2). A p l o t of average e f f l u e n t BOD versus average d a i l y water consumption, Figure 4, i l l u s t r a t e s no i n t e r p r e t a b l e c o r r e l a t i o n . The Cromaglass p l a n t s are designed to produce t h e i r best e f f l u e n t q u a l i t y w i t h i n a range of d a i l y average h y d r a u l i c loadings. That i s , the manufacturer expects h i s u n i t s to produce an e f f l u e n t BOD of approximately 4 0 mg/1 when ser v i n g households d i s c h a r g i n g approximately 160 gpd. Depending on the t u r n down and overload c a p a c i t i e s of the p l a n t , good I NJ 00 I 33 67 100 WATER CONSUMPTION (HYDRAULIC LOADING) 133 gal per day 167 200 FIGURE 4 - EFFLUENT BOD VERSUS HYDRAULIC LOADING -29-treatment e f f i c i e n c y should be achievable over a range of h y d r a u l i c l o a dings. However, i f the d a i l y average input i s s u f f i c i e n t l y f a r removed from 160 gpd a decrease i n treatment e f f i c i e n c y would be expected. Although h y d r a u l i c loadings ranged from 20 to 195 gpd, s i g n i f i c a n t l y decreased treatment e f f i c i e n c i e s were not observed at the e x t r e m i t i e s . Thus, no d e c i s i o n about the p o s s i b l e e f f e c t s of h y d r a u l i c underloading or overloading can be made from these data. 5. S e t t l i n g Several attempts were made to measure s e t t l e a b l e s o l i d s i n both the e f f l u e n t and the mixed l i q u o r . The t e s t s were conducted i n 1000 ml p l a s t i c graduated c y l i n d e r s . In a l l cases, i n s u f f i c i e n t s o l i d s s e t t l e d to o b t a i n a measurement. However, samples of the supernatant of some of these t e s t s were analyzed. The r e s u l t s are reported i n Table 8. TABLE 8 RESULTS OF SETTLING OF TYPE D EFFLUENT Sample S e t t l i n g Time U n s e t t l e d S e t t l e d Percent Removal # hours BOD mg/1 SS mg/1 BOD mg/1 SS mg/1 BOD Q. "5 SS % 1 2 89 76 85 20 4 74 2 2 85 84 116 14 -36 83 3 1 92 68 94 25 -2 63 4 1 75 14 76 13 -1 7 -30-T h e s e r e s u l t s s u g g e s t t h a t f o r t y p e D p l a n t s , where e f f l u e n t s o l i d s c o n c e n t r a t i o n s a r e s i g n i f i c a n t , t h e e f f l u e n t c o u l d be i m p r o v e d by q u i e s c e n t s e t t l i n g . However, BOD r e m o v a l s c a n n o t be so a f f e c t e d . 6. E f f e c t o f L a u n d r y on E f f l u e n t Q u a l i t y A u t o m a t i c w a s h i n g m a c h i n e s u s e l a r g e v o l u m e s o f w a t e r and d i s c h a r g e w a s t e w a t e r a t h i g h r a t e s . B e c a u s e l a u n d r y d i s c h a r g e s t e n d t o s h o c k l o a d t h e t r e a t m e n t p l a n t , an a t t e m p t was made t o e v a l u a t e t h e i r e f f e c t on e f f l u e n t q u a l i t y . Many homeowners f o u n d i t was n e c e s s a r y t o s p r e a d t h e i r u s e o f t h e l a u n d r y m a c h i n e o v e r t h e week t o p r e v e n t e x c e s s i v e t i l e f i e l d e r u p t i o n * . However, two h o u s e w i v e s r e s t r i c t e d a l m o s t a l l o f t h e i r w a s h i n g t o one day o f t h e week. T a b l e 9 i l l u s t r a t e s t h a t l a u n d r y u s e a p p a r e n t l y has l i t t l e s i g n i f i c a n t e f f e c t on BOD and an i n c o n s i s t e n t e f f e c t on SS i n t h e e f f l u e n t . T h e s e d a t a may a l s o i n d i c a t e t h a t t h e p l a n t s w o u l d show good r e s i s -t a n c e t o o t h e r s h o c k h y d r a u l i c l o a d s . * N ote: Many homeowners e x p e r i e n c e d r e g u l a r ( o f t e n , e s s e n t i a l l y c o n t i n u o u s ) e r u p t i o n o f t h e i r a b s o r p t i o n f i e l d s y s t e m s . T h e s e e r u p t i o n s a r e u n d o u b t a b l y a t t r i b u t a b l e t o many c a u s e s . I t s h o u l d be e m p h a s i z e d t h a t t h e t r e a t m e n t p l a n t m a n u f a c t u r e r , N o r t h e r n P u r i f i c a t i o n S e r v i c e s L t d . , d i d n o t p a r t i c i p a t e i n t h e d e s i g n o r c o n s t r u c t i o n o f any o f t h e f i e l d s s u r v e y e d i n t h i s s t u d y . -31-TABLE 9 EFFECT OF LAUNDRY USE ON EFFLUENT QUALITY Wash Day Non-wash Day House average BOD average SS average BOD average SS # mg/1 mg/1 mg/1 mg/1 1 86 53 83 92 3 65 78 73 67 7. A e r a t i o n Pump F a i l u r e One u n i t was sampled to examine the e f f l u e n t q u a l i t y during periods of a e r a t i o n pump f a i l u r e . The e f f e c t s of such a f a i l u r e are i l l u s t r a t e d i n Figure 5. The a e r a t i o n pump i n t h i s p l a n t had f a i l e d l e s s than 24 hours before sampling began on J u l y 9 and the pump was replaced before sampling s t a r t e d on J u l y 10. The household c o n s i s t e d of two a d u l t s , one c h i l d and one i n f a n t . The f a i l u r e of the pump was not recognized by a member of the household. As the Figure shows, BOD increased immediately, but s o l i d s concentrations remained low. The low s o l i d s l e v e l may have occurred because the non-functioning a e r a t i o n chamber acted as a s e t t l i n g tank. The s o l u b l e or c o l l o i d a l BOD was not s e t t l e d out and was c a r r i e d i n t o the 'discharge' chamber through the overflow. A f t e r a e r a t i o n resumed, the stored s o l i d s were probably resuspended by the a e r a t i o n pump and hence r e s u l t e d i n the high s o l i d s concentrations on J u l y 10. Some increase -32-180 or E 140 O < Cr: U z O U UJ z> _ l L L LL LU U o < Cr: 100 h -60 h -20 \— 20 30 JUNE 10 . 20 30 11 JULY AUG FIGURE 5 - EFFECT OF AERATION PUMP FAILURE ON EFFLUENT QUALITY -33-i n BOD was a l s o noted on J u l y 10, probably i n d i c a t i n g the BOD a s s o c i a t e d w i t h the resuspended s o l i d s . By J u l y 18, e f f l u e n t q u a l i t y had returned to normal. The quick increase i n BOD concentrations ( i t took l e s s than 24 hours to reach 160 mg/1) emphasizes the need f o r e a r l y r e c o g n i t i o n of f a i l u r e as w e l l as the n e c e s s i t y of prompt a e r a t i o n pump replacement. The very high BOD concentrations e x h i b i t e d during f a i l u r e periods could lead to severe oxygen d e f i c i t s i n small d i s p o s a l f i e l d s . In a d d i t i o n , a f t e r a p e r i o d of dosing w i t h high BOD e f f l u e n t , the f i e l d would r e c e i v e two or three doses of e f f l u e n t w i t h very high SS concentrations. This may lead to c o n d i t i o n s from which the f i e l d could not normally recover. 8. Other Data I t i s very d i f f i c u l t to compare the o p e r a t i o n a l and e f f l u e n t c h a r a c t e r i s t i c s of the many household waste treatment u n i t s on the market. In f a c t , very l i t t l e data, c o l l e c t e d under f i e l d c o n d i t i o n s s i m i l a r to those of t h i s study, i s a v a i l a b l e . The only other e f f l u e n t data a v a i l a b l e f o r the type D Cromaglass p l a n t s . i s t h a t provided by the manufacturer. In a d d i t i o n to c o n t r o l l e d t e s t i n g , they sampled two p l a n t s which had been i n s t a l l e d and maintained under f a c t o r y s u p e r v i s i o n at p r i v a t e d w e l l i n g s . A f t e r sampling each p l a n t during s i x discharges over a two month p e r i o d , they r e p o r t the data shown i n Table 10. These s i g n i f i c a n t l y b e t t e r r e s u l t s may be e x p l i c a b l e -34-i n terms of the much improved (over general f i e l d p r a c t i c e ) i n s t a l l a t i o n and maintenance procedures used by the f a c t o r y personnel. C e r t a i n l y , t h i s q u a l i t y of e f f l u e n t i s i n an e n t i r e l y d i f f e r e n t range i n terms of t i l e f i e l d length requirements, than t h a t reported e a r l i e r i n t h i s chapter. TABLE 10 NPS EFFLUENT DATA ON CROMAGLASS TYPE CA5-D* House BOD, mg/1 SS, mg/1 high average low high average low A 60 34 21 115 60 15 B 51 36 18 47 33 23 * Data obtained through p r i v a t e communication w i t h Northern P u r i f i c a t i o n S e r v ices L t d . B. E f f l u e n t Q u a l i t y : Type CA5-E The sampling procedure discussed i n the f i r s t pages of t h i s chapter was modified s l i g h t l y f o r the type E p l a n t s . Based on the improvement i n q u a l i t y obtained by s e t t l i n g the type D e f f l u e n t , i t was assumed the s e t t l i n g p e r i o d would s i g n i f i c a n t l y improve the type E e f f l u e n t . In order to o b t a i n a sample of the best p o s s i b l e e f f l u e n t q u a l i t y , samples were taken c l o s e r to the l i q u i d surface i n the s e t t l i n g tank. In theory then, t h i s "supernatant" sample would be at l e a s t as good, i f not b e t t e r than, a sample taken from a greater depth near the discharge pump i n l e t . However, the sampling p o i n t -35-was f a r enough below the surface t h a t f l o a t i n g m a t e r i a l s were excluded. 1. E f f e c t of S e t t l i n g As noted e a r l i e r , quiescent s e t t l i n g s i g n i f i c a n t l y reduced SS i n the type D e f f l u e n t . This improvement was not g e n e r a l l y observed during the two hour s e t t l i n g p e r i o d of the type E p l a n t s . Samples, taken at 15 to 30 minute i n t e r v a l s , as shown i n Table 11, g e n e r a l l y e x h i b i t e d increased, not decreased, SS concentrations. TABLE 11 EFFECT OF SETTLING IN CA5-E PLANTS E f f l u e n t at Cessation E f f l u e n t a f t e r approx. of A e r a t i o n 2 hours of s e t t l i n g BOD SS BOD SS 70 57 76 80 31 16 33 41 34 35 45 31 76 22 94 39 97 54 105 51 66 65 65 63 72 48 40 61 One e x p l a n a t i o n , f o r the poor s o l i d s removal p e r f o r -mance, may be r e l a t e d to the observation of f l o a t i n g s o l i d s i n those p l a n t s which became anaerobic before discharge. This may i n d i c a t e that a resuspension of the s o l i d s by r i s i n g gas -36-was o c c u r r i n g . The increased or unchanged BOD concentrations are to be expected from the type D t e s t r e s u l t s . C e r t a i n l y , the quiescent p e r i o d d i d not appear to c o n s i s t e n t l y improve e f f l u e n t q u a l i t y . The VSS to TSS r a t i o exceeded 0.875 and averaged 0.953 f o r the type E u n i t s as compared w i t h an average of 0.788 f o r the type D p l a n t s . This may i n d i c a t e t h a t the s e t t l i n g p e r i o d does decrease the concent r a t i o n of i n o r g a n i c SS r e l a t i v e to the organic s o l i d s i n the e f f l u e n t . As w i t h the type D p l a n t s , the i n a b i l i t y of the s e t t l i n g tank .portion of these u n i t s to remove s o l i d s from the mixed l i q u o r means th a t l i t t l e or no s o l i d s w i l l be returned to the mixed l i q u o r . 2. D i s s o l v e d Oxygen As noted f o r the type D p l a n t s , d i s s o l v e d oxygen concentrations were more than adequate during the a e r a t i o n c y c l e . Continuing b i o l o g i c a l a c t i v i t y caused a decrease i n D.O. concentrations during the s e t t l i n g p e r i o d . In p l a n t s s e r v i n g more than four persons, D.O. l e v e l s below 1.0 mg/1 were measured at the end of the s e t t l i n g p e r i o d . These low D.O. concentrations i n the e f f l u e n t put an e x t r a s t r e s s on the t i l e f i e l d . In a d d i t i o n , the consequent odor i s the source of complaints. C. General Observations In a d d i t i o n to the s p e c i f i c data on e f f l u e n t q u a l i t y , thus f a r discussed, some general observations were made. Most of the houses to which the t e s t u n i t s were connected had plumbing i n the basement. To o b t a i n g r a v i t y -37-flow to the p l a n t , i t was placed i n a la r g e manhole or wooden box as much as s i x f e e t below ground l e v e l . U s u a l l y t h i s meant that the t i l e f i e l d was l o c a t e d s e v e r a l f e e t above the discharge l e v e l of the p l a n t . As the t o t a l volume of f i f t y f e e t (many of the t i l e f i e l d s had f i f t y f e e t of d i s t r i b u t i o n pipe) of four i n c h diameter t i l e (27 gal) i s only h a l f the discharge volume of the u n i t (48 g a l ) , a s i g n i f i c a n t p o r t i o n of the discharge would flow back i n t o the u n i t a f t e r pumping stopped. This r e s u l t e d i n some u n i t s d i s c h a r g i n g as of t e n as every ten minutes during high water use periods. Excessive pump wear i s then due, not only to frequent o p e r a t i o n , but a l s o to the pumping of ino r g a n i c s o l i d s washed i n t o the tank from the f i e l d . The problem could be a l l e v i a t e d by i n s t a l l i n g a check valve between the pump and the d i s t r i b u t i o n box* A l t e r n a t i v e l y , a twelve to eighteen i n c h drop from a high p o i n t i n the discharge l i n e to the d i s t r i b u t i o n box could be constructed. The l o c a t i o n of u n i t s below ground l e v e l a l s o l e d to ground water i n f i l t r a t i o n problems. Several u n i t s were observed w i t h ground water showing between the access manholes. During high ground water periods a number of these u n i t s could e a s i l y be flooded. Drainage of the area around the p l a n t s i s r e q u i r e d to prevent overloading the discharge pumps. A d d i t i o n a l l y , c o l l a r s , bonded to the p l a n t and p r o j e c t i n g to ground l e v e l , could be i n s t a l l e d . The f a i l u r e of a e r a t i o n pumps, i f not q u i c k l y c o r r e c t e d , can be s e r i o u s l y d e t r i m e n t a l to small t i l e f i e l d s . In almost a l l cases of a e r a t i o n pump f a i l u r e , the problem -38-was f i r s t recognized by the t e c h n i c i a n doing the sampling or by the householder, only a f t e r the anaerobic odor had become int e n s e . At no time were the warning systems r e s p o n s i b l e f o r the r e c o g n i t i o n of f a i l u r e . Some u n i t s went as long as f i v e or s i x days before the householder became aware of the problem. I f t i l e f i e l d l ength i s to be minimized, a b e t t e r system of pump f a i l u r e warning i s needed. In respect to s e r v i c i n g , one of two p o l i c i e s must be adopted. I f the present frequency of p r o f e s s i o n a l s e r v i c e i s a l l t h a t can be economically provided, the householder must be taught to i n s p e c t and s e r v i c e h i s own u n i t . Most im p o r t a n t l y , he must be able to recognize and c o r r e c t clogged a e r a t i o n pumps and to maintain the c l e a n l i n e s s of the u n i t . There i s no question that without t h i s owner p a r t i c i p a t i o n , the present s e r v i c e frequency i s inadequate. The other procedure would exclude the householder almost completely and increase the dealer s e r v i c e to monthly a t l e a s t . Monthly s e r v i c e may s t i l l be i n s u f f i c i e n t . This p o l i c y would r e q u i r e a good alarm system and the cooperation of the householder i n responding to i t . One of the problems i n a n a l y z i n g the operation of the p l a n t s i s the number of missing or damaged components and the v a r i a t i o n , i n arrangement of pumps and chambers. Several p l a n t s had broken or l e a k i n g t r a n s f e r l i n e s which l e d to spray a e r a t i o n and high d i s s o l v e d oxygen l e v e l s . M i s s i n g t r a n s f e r l i n e s meant that the mixed l i q u o r was j e t t e d i n t o the s e t t l i n g tank. This created more than normal turbulence and undoubtedly decreased s e t t l i n g e f f i c i e n c y . D i f f e r e n t -39-depths of the discharge pump i n the s e t t l i n g chamber meant t h a t some u n i t s scoured the bottom of the s e t t l i n g tank more thoroughly during discharge. This may have a f f e c t e d s o l i d s l e v e l s i n the e f f l u e n t . In a d d i t i o n to sampling the treatment p l a n t s , approximately 30 d i s p o s a l f i e l d s were inspected v i s u a l l y . These i n s p e c t i o n s were supplimented by i n t e r v i e w s w i t h the current householders. Of the t h i r t y , f i e l d s , 13 were reported to erupt r e g u l a r l y . These eruptions were g e n e r a l l y confirmed by i n s p e c t i o n . Four other householders had not occupied t h e i r houses long enough to comment. Thus, 13 of 26 f i e l d s were er u p t i n g r e g u l a r l y . At l e a s t four homeowners had i n s t a l l e d major m o d i f i c a t i o n s to t h e i r f i e l d s . Undoubtably, there are a number of explanations f o r these f a i l u r e s , not the l e a s t of which i s poor c o n s t r u c t i o n techniques. Another major complaint was t h a t of e f f l u e n t washed out of neighbouring t i l e f i e l d s onto the a d j o i n i n g l o t . This was an acute problem i n some areas during the high ground water l e v e l periods i n the s p r i n g . Apparently, l i t t l e has been done to i s o l a t e i n d i v i d u a l t i l e f i e l d s . Two t i l e f i e l d s which had been b u i l t from g r a v e l p i t r a k i n g s , as p r e s c r i b e d by the Health Branch, were sampled f o r s o i l a n a l y s i s . The probable drainage c h a r a c t e r i s t i c s of both f i e l d s were described as "poor". Both f i e l d s erupted during the summer. However, one of the f i e l d s erupted only a f t e r the house had been occupied by ten people f o r one week. Apparently, another source of t i l e f i e l d s o i l should be recommended. -40-SUMMARY In gene r a l , the data suggest t h a t the p l a n t s i n s t a l l e d under the i n s p e c t i o n , s u p e r v i s i o n , and c o n s t r u c t i o n c o n d i t i o n s p r e v a i l i n g i n the l a s t two years, are not capable of producing an e f f l u e n t i n the 30 to 4 0 mg/1 BOD,- range. In Chapter 4, i t w i l l be noted t h a t l i t e r a t u r e suggests t h i s r e l a t i v e l y high q u a l i t y e f f l u e n t i s r e q u i r e d before s i g n i f i c a n t d e v i a t i o n s from curren t d i s p o s a l f i e l d design p r a c t i c e can be permitted. -41-CHAPTER 4  DISPOSAL SYSTEMS - STATE OF THE ART INTRODUCTION: The survey described i n t h i s chapter was undertaken to review the current s t a t e - o f - t h e - a r t i n the design of absorption f i e l d d i s p o s a l systems. The premier question to be considered i n t h i s regard i s : What i s the purpose of a t i l e f i e l d ? C o n f l i c t i n g opinions e x i s t between those who are p r i m a r i l y concerned w i t h keeping e f f l u e n t below the ground surface (wastewater d i s p o s a l ) and those whose f i r s t p r i o r i t y i s a d d i t i o n a l treatment. C e r t a i n l y , both features are important. This question could be considered by d i v i d i n g t i l e f i e l d s i n t o two c a t e g o r i e s . In one group are those f i e l d s which serve houses r e c e i v i n g municipal water s u p p l i e s . The problem of groundwater p o l l u t i o n i s then not of concern i n the p u b l i c h e a l t h context unless the groundwater surfaces near the t i l e f i e l d . However, p o l l u t i o n of surface waters can occur. Many Ontario lakes (3) and the Okanagan lakes (20) i n B.C., among other s , are s i g n i f i c a n t l y a f f e c t e d by n u t r i e n t s c a r r i e d from s o i l d i s p o s a l systems to surface waters by groundwater. The second category would in c l u d e those d w e l l i n g s r e l y i n g upon w e l l water taken from a s i t e r e l a t i v e l y c l o s e to the t i l e f i e l d . Here groundwater p o l l u t i o n i s an important f a c t o r . The c u r r e n t , g e n e r a l l y recommended, minimum dis t a n c e of one hundred f e e t from a t i l e f i e l d to a w e l l may, i n some -42-s o i l s , be i n s u f f i c i e n t to prevent water supply contamination (19) . One could c a r r y on a d i s c u s s i o n and formulate r e g u l a t i o n s f o r the two c a t e g o r i e s s e p a r a t e l y . However, many authors have warned of the undesirable and o f t e n unpredictable e f f e c t s of b l a t a n t groundwater p o l l u t i o n (19, 20). This chapter w i l l then, concentrate on systems which provide both p r o t e c t i o n of groundwater q u a l i t y and adequate long term h y d r a u l i c c a p a c i t y . The d i s c u s s i o n i s o r i e n t e d p r i m a r i l y toward absorption f i e l d s constructed i n i n s i t u s o i l or s p e c i f i e d imported f i l l . F i e l d s constructed w i t h s p e c i a l f a c i l i t i e s f o r i n t r o d u c i n g a i r are touched on near the end of the chapter. I t i s important to c l a r i f y some b a s i c concepts i n a d i s c u s s i o n of l i q u i d a p p l i c a t i o n to s o i l s . The f o l l o w i n g d e f i n i t i o n s w i l l help to put the d i s c u s s i o n on a common f o o t i n g . From McGauhey and Winneberger (17): P o r o s i t y : i s the f r a c t i o n of the t o t a l s o i l volume which i s v o i d . In other words, i t i s the p r o p o r t i o n of the s o i l volume which can be occupied by a i r and/or l i q u i d . Perviousness: r e f e r s to the s i z e d i s t r i b u t i o n of the v o i d spaces i n v o l v e d i n p o r o s i t y . I t i s , however, measured by the r a t e of passage of l i q u i d under standard c o n d i t i o n s . This measure i s c a l l e d the p e r m e a b i l i t y (or h y d r a u l i c c o n d u c t i v i t y , K) of the system. The i n f i l t r a t i v e c a p a c i t y i s the r a t e at which l i q u i d w i l l pass through the s o i l - w a t e r i n t e r f a c e . The p e r c o l a t i v e c a p a c i t y i s the r a t e at which water moves through the s o i l once i t has passed the i n t e r f a c e . Both the i n f i l t r a t i v e and the p e r c o l a t i v e c a p a c i t y can be l i m i t i n g . However, i n t i l e f i e l d design, i t i s d e s i r a b l e to maintain a higher p e r c o l a t i o n than i n f i l t r a t i o n r a t e . This - 4 3 -i s necessary to prevent the problems a s s o c i a t e d w i t h s o i l s a t u r a t i o n discussed l a t e r . Many f a c t o r s have been shown to have a s i g n i f i c a n t e f f e c t on the r a t e of passage of l i q u i d s i n t o and through s o i l . Among these are 1. r a t e and p a t t e r n of a p p l i c a t i o n 2 . chemical and b i o l o g i c a l composition of the l i q u i d 3. temperature 4. s o i l t e x t u r e , s t r u c t u r e and composition 5. s o i l depth 6 . depth to groundwater (and f l u c t u a t i o n s of t h i s depth) 7. s o i l moisture t e n s i o n (degree of satu r a t i o n ) 8 . slope of a p p l i c a t i o n surface 9. s o i l p e r m e a b i l i t y , p o r o s i t y and homogeneity 10. presence of s w e l l i n g c l a y s Many of these f a c t o r s are a f u n c t i o n of the s o i l t e x t u r e as i t r e l a t e s to pore s i z e . As water i s transported through the s o i l pores, the s i z e and number of these pores has a great e f f e c t upon the water t r a n s p o r t r a t e . Thus, any change i n the number or s i z e d i s t r i b u t i o n of the pores w i l l a f f e c t the r a t e of water t r a n s p o r t . Adverse changes i n s o i l ' pore s i z e or d i s t r i b u t i o n are termed c l o g g i n g . I. S o i l Pore Clogging There are three fundamental types of s o i l pore cl o g g i n g ; P h y s i c a l , Chemical and Biochemical. _44-P h y s i c a l Clogging P h y s i c a l c l o g g i n g i s due p r i m a r i l y to poor construc-ri', t i o n techniques. To a very l a r g e degree, t h i s problem could be reduced by education of c o n t r a c t o r s , i n s p e c t o r s and house-holders. I t can probably be blamed f o r the e a r l y f a i l u r e of many otherwise adequately s i z e d t i l e f i e l d s . McGaughey and Winneberger (17) have summarized the causes of p h y s i c a l c l o g g i n g as f o l l o w s : 1. Compaction of the s o i l by superimposed loads 2. Smearing of s o i l surfaces by excavation equipment 3. M i g r a t i o n of f i n e s by v i b r a t i o n of dry s o i l during s i t e p r e p a r a t i o n 4. M i g r a t i o n of f i n e s due to r a i n f a l l beating a g a i n s t surfaces 5. Washdown of f i n e s perched on l a r g e r p a r t i c l e s . To these might be added: 1. Movement of f i n e s by water pressure during high volume discharges to small t i l e f i e l d s . 2. Fines moved i n t o and onto the f i e l d by f l o o d i n g 3. Suspended s o l i d s i n the a p p l i e d e f f l u e n t 4. S w e l l i n g of some c l a y f r a c t i o n s (a physio-chemical e f f e c t ) . The most important e f f e c t of the p h y s i c a l c l o g g i n g mechanism i s the s e a l i n g of the trench bottom. V i b r a t i o n and water flow c a r r y the f i n e s to the bottom of the trench where they c o n t r i b u t e to the s e a l i n g of t h i s surface. Thus, where even r e l a t i v e l y small amounts of f i n e s are present, t h e i r c o n c e n t r a t i o n on the bottom of the trench e f f e c t i v e l y e l i m i n a t e s t h i s surface as an i n f i l t r a t i o n area. - 4 5 -I t i s apparent from the mechanisms of t h i s type of clogging that i t can be l a r g e l y e l i m i n a t e d by: 1. Taking care during c o n s t r u c t i o n to avoid heavy loads / : on the s i t e s u r f a c e , minimize or c o r r e c t smearing and minimize v i b r a t i o n . 2. To i n s p e c t the s i t e soon a f t e r the t i l e i s l a i d to prevent l e a v i n g the trenches open to the weather f o r extended periods. 3. Prevent groundwater f l o o d i n g . 4 . M a i n t a i n a low suspended s o l i d s i n the a p p l i e d e f f l u e n t . With care, e a r l y f i e l d f a i l u r e due t o p h y s i c a l . c l o g g i n g should be r e l a t i v e l y r a r e . Chemical Clogging Chemical c l o g g i n g i s u s u a l l y i n s i g n i f i c a n t or p r o h i b i t i v e . The cause of most chemical c l o g g i n g i s r e l a t e d t o the sodium exchange c a p a c i t y of some c l a y s . The a d d i t i o n of excess sodium causes these c l a y s to become s t r u c t u r a l l y unstable and pore cl o g g i n g r e s u l t s . In most l o c a t i o n s , t h i s problem does not e x i s t . However, where i t i s encountered, i t u s u a l l y means e i t h e r sodium removal must be p r a c t i c e d , or i n s i t u seepage beds are impossible. I t i s i n t e r e s t i n g to note t h a t chemical i s the o n l y form of c l o g g i n g which can be estimated i n l a b o r a t o r y e x p e r i -ments. -46-B i o l o g i c a l Clogging B i o l o g i c a l c l o g g i n g i s p r i m a r i l y due to the growth of b a c t e r i a i n the s o i l . This type of clogging can occur i n two forms, depending on the s o i l p a r t i c l e s i z e and the organic l o a d i n g r a t e . Surface c l o g g i n g , i n which a b i o l o g i c a l mat l e s s than two centimeters t h i c k forms, g e n e r a l l y occurs i n s o i l s w i t h an e f f e c t i v e p a r t i c l e s i z e of l e s s than 0.1 mm r e g a r d l e s s of the organic lo a d i n g (17). In coarser s o i l s , a r e l a t i v e l y permeable l a y e r of b i o l o g i c a l growth has been observed (24, 26). The depth of t h i s l a y e r ranges from 5 to 35 cm. Although t h i s type of formation reduces the i n f i l t r a t i o n r a t e , i t s presence o f t e n i n d i c a t e s the p o s s i b i l i t y of e s t a b l i s h i n g a r e l a t i v e l y good long term i n f i l t r a t i o n c a p a c i t y . That i s , the long term c a p a c i t y of the system w i l l be a r e l a t i v e l y high percentage of i t s i n i t i a l r a t e . The d e s t r u c t i o n of b i o l o g i c a l mats i s c a r r i e d out by r o t i f e r s , c i l i a t a and other higher organisms. These orga-nisms do not f u n c t i o n w e l l under anaerobic c o n d i t i o n s . Consequently, the extent of b i o l o g i c a l c l ogging i s a f f e c t e d by oxygen content of the immediate s o i l . The oxygen content of the s o i l i s i n f l u e n c e d by 1. oxygen content of the a p p l i e d e f f l u e n t 2. s o i l t e x t u r e and pore s i z e d i s t r i b u t i o n 3. temperature 4. depth of the f i e l d 5. a p p l i e d organic load - 4 7 -6. s o i l moisture t e n s i o n among others. In order to maintain the pyramid of higher organisms necessary to c o n t r o l b a c t e r i a l p r o l i f e r a t i o n , i t i s e s s e n t i a l to maintain aerobic c o n d i t i o n s . l a r g e numbers of b a c t e r i a , s i g n i f i c a n t c l o g g i n g occurs through the d e p o s i t i o n of ferrous sulphide. Formed under anaerobic c o n d i t i o n s , t h i s compound i s deposited as a s l i g h t l y s o l u b l e c r y s t a l on the i n s i d e of the s o i l pores. Aerobic c o n d i t i o n s are needed f o r i t s e l i m i n a t i o n . overloading of the s o i l surface. The normal s o i l b a c t e r i a p o p u l a t i o n expands r a p i d l y i n response to t h i s increased food source. The presence of suspended s o l i d s i n the e f f l u e n t can cause immediate cl o g g i n g of some pores. I f the organic l o a d i n g i s maintained at a s u f f i c i e n t l y high r a t e , e i t h e r i n t e r m i t t e n t l y or continuously, the p r o l i f e r a t i o n of b a c t e r i a w i l l continue. E v e n t u a l l y a more or l e s s s t a b l e p o p u l a t i o n which i s i n e q u i l i b r i u m w i t h the organic load i s reached. The net e f f e c t i s i l l u s t r a t e d below. In a d d i t i o n to the clogging due to the presence of B i o l o g i c a l c l o g g i n g i s i n i t i a t e d by the organic NTS. biological surface mat unsaturated, aerobic soil -48-As the i n f i l t r a t i o n r a t e i s g r e a t l y reduced by the mat, the l i q u i d which passes through the surface q u i c k l y p e r c o l a t e s away. This leaves the s o i l under and around the trench aerobic and unsaturated but the contents of the trench remain anaerobic. U s u a l l y , even i f the a p p l i e d l i q u i d has a s i g n i f i c a n t D.O., i t w i l l q u i c k l y become anaerobic i n the trench. Thus, i n s o i l s where surface mat formation i s l i k e l y to occur, every e f f o r t should be made to introduce as much a i r i n t o the system as p o s s i b l e . In most conventional s e p t i c tank systems, the f i e l d i s dosed by g r a v i t y induced t r i c k l e flow. This flow tends to overload each increment of the f i e l d s e q u e n t i a l l y and thus induces r a p i d f a i l u r e . I f the organic load could be spread over the e n t i r e e f f e c t i v e surface area of the f i e l d a t once, the organic load per u n i t area would be minimized. This would r e s u l t i n a minimum demand on l o c a l oxygen reserves and a minimum production of b a c t e r i a per u n i t area. B i o l o g i c a l c l o g g i n g would be thus reduced and f i e l d l i f e extended. Obviously, higher d i s s o l v e d oxygen l e v e l s and lower biochemical oxygen demands i n the e f f l u e n t would decrease the amount of anaerobic c l o g g i n g . I t has been i l l u s t r a t e d (6) t h a t the d e p o s i t i o n of suspended s o l i d s from the e f f l u e n t i s important i n i n i t i a t i n g c l o g g i n g . Thus, e f f l u e n t q u a l i t y i s important from the f i r s t day of ope r a t i o n . Even i n beds which are dosed i n t e r m i t t e n t l y , the d e p o s i t i o n of suspended s o l i d s on the trench bottom, i n conj u n c t i o n w i t h the p h y s i c a l c l o g g i n g discussed e a r l i e r , e f f e c t i v e l y s e a ls t h i s surface (except in. very coarse s o i l s ) . -49-Consequently, a f t e r a short p e r i o d of o p e r a t i o n , almost a l l of the a p p l i e d e f f l u e n t i s being processed through the s i d e w a l l area of the trench. In f i n e s o i l s , the best o p e r a t i o n , i n terms of maintaining i n f i l t r a t i v e c a p a c i t y , may be to dose the f i e l d evenly and then wait u n t i l the a p p l i e d organic m a t e r i a l has been a s s i m i l a t e d by the b a c t e r i a . The next dose would be a p p l i e d a f t e r the b a c t e r i a l p o p u l a t i o n had been reduced to i t s i n i t i a l l e v e l . A l a r g e e f f l u e n t storage f a c i l i t y and a very l a r g e absorption f i e l d , i n most s o i l s , would be r e q u i r e d to handle the wastes from one household, i f t h i s o peration were adopted. This type of operation i s approached i n pump and siphon dosed f i e l d s . However, normally the h y d r a u l i c load i s such t h a t dosing must be c a r r i e d out more f r e q u e n t l y than t h i s i d e a l o p e ration. One a l t e r n a t i v e suggestion (17) has been to c o n s t r u c t a f i e l d of r e l a t i v e l y coarse imported m a t e r i a l . Here the build-up of a r e l a t i v e l y l a r g e b a c t e r i a l p o pulation leads to an in-depth b i o l o g i c a l l a y e r . The surface c r u s t i s avoided yet s u f f i c i e n t b a c t e r i a are present to provide r e l a t i v e l y good treatment. This sand bed technique a l s o r e q u i r e s p r o v i s i o n f o r good a i r c i r c u l a t i o n . Other methods of reducing b i o l o g i c a l c l o g g i n g i n c l u d e the a l t e r n a t i n g use of two or more beds and dosing f i e l d s e c t i o n s i n sequence. McGauhey and Winneberger (17) have suggested surface b i o l o g i c a l matting can be expected to be i n f i l t r a t i o n r a t e c o n t r o l l i n g i n s o i l s w i t h an e f f e c t i v e p a r t i c l e s i z e of l e s s -50-than 0.1 mm ( f i n e sand). Clogging occurs i n these s o i l s even at very low organic loadings and when apparently aerobic c o n d i t i o n s e x i s t . I f s o i l analyses i n d i c a t e t h a t t h i s e f f e c t i v e p a r t i c l e s i z e (0.1 mm) i s not exceeded, they conclude t h a t a conservative design h y d r a u l i c l o a d i n g r a t e i s 0.03 ft/day based on s i d e w a l l area. Bouma (5) observed t h i s surface c l o g g i n g phenomena i n much coarser s o i l s , up to 4 mm i n s i z e . However, c r u s t s i n these coarser s o i l s appear to maintain i n f i l t r a t i o n r a t e s of 0.10 to 0.26 f t / d a y . McGaughey and Winneberger (17) have suggested using a conservative design f i g u r e of 0.06 ft/day i n these s o i l s . Thomas (23) suggested t h a t the long term a b i l i t y of a s o i l to accept e f f l u e n t may be c o n t r o l l e d by the r a t e of oxygen d i f f u s i o n to the loaded surface. His idea supports the contention t h a t i t i s the b i o l o g i c a l mat which c o n t r o l s the i n f i l t r a t i o n r a t e and not the s o i l p e r c o l a t i o n c h a r a c t e r i s t i c s per se. B i o l o g i c a l c l o g g i n g may be a c c e l e r a t e d by other a f f e c t s . De V r i e s (26) r e p o r t s on the e f f e c t s of c o l d temper-atures on surface dosed sand f i l t e r s . B i o l o g i c a l c l o g g i n g , which d i d not occur a t room temperature, was induced q u i c k l y at 4 °C. These r e s u l t s may be an i n d i c a t i o n of the i n a b i l i t y of the b i o l o g i c a l system to process heavy organic loads at low temperatures. Groundwater inundation of a p r e v i o u s l y unclogged bed can lead to the anaerobic c o n d i t i o n s which cause c l o g g i n g . Recession of the water t a b l e does not n e c e s s a r i l y mean tha t -51-the clogged bed has the a b i l i t y to regenerate i t s e l f w hile s t i l l r e c e i v i n g e f f l u e n t . The consensus i s that a l l seepage beds w i l l s u f f e r 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 w i t h time. I t has been shown (5, 17, 24, 26) tha t much of t h i s l o s t c a p a c i t y can be regained by ' r e s t i n g ' the bed, tha t i s , by a l l o w i n g the bed to d r a i n and dry and a l l o w i n g time f o r the accumulated organics and b a c t e r i a t o be o x i d i z e d . The d i f f u s i o n of a i r i n t o the system w i l l a l s o o x i d i z e any ferrous sulphide d e p o s i t s . Not a l l of the l o s t c a p a c i t y w i l l be regained because of the d e p o s i t i o n of r e s i s t a n t organic and i n o r g a n i c m a t e r i a l s . The question of how long a r e s t p e r i o d i s r e q u i r e d before a f i e l d i s returned t o operation i s impossible to answer. Some of the f a c t o r s which i n f l u e n c e the r a t e of recovery are the amount of organic m a t e r i a l accumulated i n the bed, the r a t e at which the bed d r a i n s , r a t e of oxygen d i f f u s i o n i n t o the bed, temperature, moisture t e n s i o n of the surrounding s o i l and so on. Rest periods of anywhere from a week to a year have been suggested f o r var i o u s values of the above mentioned f a c t o r s . I f the bed i s to be operated on an i n t e r m i t t e n t b a s i s , another d i s p o s a l s i t e w i l l be r e q u i r e d to operate i n the i n t e r v e n i n g p e r i o d . Thus, i n order to minimize f a i l u r e through organic c l o g g i n g , the f o l l o w i n g suggestions might be implemented: 1. maintain an aerobic e f f l u e n t , low i n BOD and SS 2. discharge i n such a f a s h i o n t h a t the whole f i e l d r e c e i v e s an equal organic load per u n i t area -52-3. m a i n t a i n a e r o b i c c o n d i t i o n s i n t h e f i e l d by a. good b ed d e s i g n and c o n s t r u c t i o n b. a l l o w i n g t h e f i e l d t o r e s t p e r i o d i c a l l y c. p r e v e n t i n g g r o u n d w a t e r i n u n d a t i o n 4. c o n s t r u c t i n g t r e n c h e s w i t h a h i g h s i d e w a l l a r e a t o volume r a t i o E f f e c t i v e u s e o f e a c h o f t h e above c r i t e r i a w o u l d i n c r e a s e b o t h c a p i t a l and o p e r a t i n g c o s t s above p r e s e n t d a y p r a c t i c e . T h e i r i m p l e m e n t a t i o n must be w e i g h e d a g a i n s t t h e c o s t o f m e r e l y i n s t a l l i n g a v e r y much o v e r d e s i g n e d t i l e f i e l d . One o t h e r p o i n t r e l e v a n t t o f i e l d d e s i g n and c l o g g i n g s h o u l d be r e c o g n i z e d . Most r e g u l a t i o n s s t i p u l a t e t h a t t h e t r e n c h a r o u n d t h e d i s t r i b u t i o n p i p e be f i l l e d w i t h g r a v e l . T h i s p r a c t i c e c r e a t e s an a b r u p t change i n p a r t i c l e s i z e a t t h e s o i l i n t e r f a c e . E f f l u e n t m o v i n g away f r o m t h e p i p e r e c e i v e s l i t t l e f i l t e r i n g u n t i l i t r e a c h e s t h e s o i l i n t e r f a c e . The t o t a l o r g a n i c l o a d i s t h e n c o n c e n t r a t e d on t h e i n t e r f a c e . A s e c o n d r e s u l t o f t h i s p r a c t i c e i s t h e b l i n d i n g o f t h e s o i l s u r f a c e as i l l u s t r a t e d b e l o w . blinded regions - unavailable for effluent disposal B o t h o f t h e s e c o n d i t i o n s c o u l d be a v o i d e d by h a v i n g an e v e n l y g r a d e d p a r t i c l e s i z e f r o m t h e p i p e t o t h e w a l l . A l t h o u g h i m p o s s i b l e , i n a p r a c t i c a l s e n s e , a two o r t h r e e l a y e r e d s y s t e m m i g h t be u s e d . -53-This short d e s c r i p t i o n of some of the mechanisms of d i s p o s a l f i e l d o p eration leads to the more p r a c t i c a l questions of f i e l d design and s i z i n g . I I . T i l e F i e l d Design T i l e f i e l d design i s u s u a l l y based upon the p e r c o l a -t i v e c a p a c i t y of the s o i l . As discussed p r e v i o u s l y , t h i s i s of t e n i n f l u e n c e d by the organic l o a d i n g . T r a d i t i o n a l l y , most r e g u l a t o r y agencies have defined the design h y d r a u l i c c a p a c i t y as 0.5 to 5 percent of the p e r c o l a t i o n r a t e as measured by a p e r c o l a t i o n t e s t . ( s e e Appendix 1). Table 12 contains some suggested f i g u r e s . As emphasized e a r l i e r i n t h i s chapter, the most important s i n g l e f a c t o r a f f e c t i n g f i e l d design i s u s u a l l y the l i m i t a t i o n of the i n f i l t r a t i o n r a t e by the b i o l o g i c a l mat. The l i t e r a t u r e g e n e r a l l y suggests that i t i s i n a d v i s a b l e to design f i e l d s on the ba s i s of maintaining aerobic c o n d i t i o n s throughout the f i e l d . I t i s f e l t t h a t the degree of r e l i a b i l i t y and c o n t r o l needed to maintain aerobic c o n d i t i o n s i n the f i e l d i s not r e a d i l y a v a i l a b l e . In a d d i t i o n , recovery from upsets or environmental i n f l u e n c e s can be slow. Most authors agree th a t i n s i t u f i e l d s are not s u i t a b l e f o r s o i l s w i t h a p e r c o l a t i o n r a t e slower than 30 min/in. A l s o many authors, r e c o g n i z i n g p o t e n t i a l groundwater p o l l u t i o n problems, suggest r a t e s f a s t e r than 3 min/in be modified unless there i s a great depth to groundwater. An acceptable loading r a t e w i l l depend on the de s i r e d l i f e of the system (7), overdesign f a c t o r s , e f f l u e n t -54-TABLE 12 PRESENT DESIGN SUGGESTIONS FOR SEPTIC TANKS  PERCOLATION RATE VS SUGGESTED HYDRAULIC LOAD P e r c o l a t i o n Suggested design h y d r a u l i c loading Rate min/in Rate I g a l / f t 2 / d a y Source 1 2 3 4 5 6a 6b 6c 7 1 0.56 0. 52 2. 08 0.75, 0.25 1.85 1.39 1.47 2 1.67 0.75 0.25 1.47 3 1.33 0.75 0.25 1.47 4 1.17 0. 75 0. 25 0.76 5 0.54 0.46 1. 08 0. 75 0.25 1. 05 1. 04 0.78 0.76 10 0.50 0.38 0. 83 0.75 0. 25 0.79 0.60 0.76 15 0.45 0.31 0.75 0.25. 0.50 20 0.41 0.25 0.60 0. 75 0.25 0.62 0.46 0.50 30 0.35 0.17 0.40 0.75 0.25 0.42 0.52 0.39 0.50 40 0.35 0.42 45 0.28 0. 08 0.42 60 0.30 0.37 90 0.15 120 0. 04 1 Benhart (2) data f o r aerobic e f f l u e n t 2 Benhart (2) data f o r anaerobic e f f l u e n t 3 Winneberger (25) Ari z o n a 4 Huddleston and Olson (13) 3% of p e r c o l a t i o n r a t e 5 Huddleston and Olson (13) 1% of p e r c o l a t i o n r a t e 6 B.C. Health Branch ( c a l c u l a t e d based on d i f f e r e n t areas) 7 Wisconsin Guide as su b s t a n t i a t e d by Bouma (5) Note: McGauhey and Winneberger (17) make the f o l l o w i n g l o a d i n g r a t e suggestions e f f e c t i v e s o i l s i z e h y d r a u l i c l o a d i n g r a t e I g a l / f t 2 / d a y < 0.1 mm 0.1 to 1.0 mm > 1.0 mm 0.10 0.14 0.21 -55-q u a l i t y , r e l i a b i l i t y of the preceding treatment and other f a c t o r s . Some authors suggest, and t h i s author concurs, t h a t because of the r e l a t i v e l y low c o s t of i n s i t u f i e l d i n s t a l l a t i o n (and even i n s t a l l a t i o n i n imported f i l l ) , t h a t very conservative design loadings should be used. As Table 12 i n d i c a t e s , McGaughey and Winneberger have proposed the most conservative r a t e s . The present P r o v i n c i a l Health Branch r e g u l a t i o n s , depending upon how they are c a l c u l a t e d , appear to be s i m i l a r to other r e g u l a t o r y agencies. I f d i f f e r e n t , they tend to permit somewhat greater h y d r a u l i c loadings. A l s o , they are much l e s s conservative than McGaughey and Winneberger 1s recommendations. However, i f the f i e l d s i z e i s r e s t r i c t e d by l o t s i z e or i f s o i l c o n d i t i o n s are very poor, improved e f f l u e n t q u a l i t y w i l l be r e q u i r e d to permit a s i g n i f i c a n t increase i n l o a d i n g r a t e s . Even the r a t e s suggested above f o r " f u l l s i z e " s e p t i c tank t i l e f i e l d s have not had complete success. The question of how much improvement i n e f f l u e n t q u a l i t y i s r e q u i r e d , before s i g n i f i c a n t reductions i n the f i e l d length can be made, has not been adequately examined i n the l i t e r a t u r e . Thomas (24) observed surface c l o g g i n g of sand f i l t e r s 2 when loa d i n g them at a r a t e of 0.67 ft/day (4.2 g a l / f t /day). The average q u a l i t y of the a p p l i e d e f f l u e n t i s shown i n Table 13. I n f i l t r a t i o n r a t e s d e c l i n e d from 3 min/in to 1500 min/in. (Note i n Table 12 t h a t the a p p l i c a t i o n r a t e i s w i t h i n the suggested range f o r absorption beds based on the i n i t i a l i n f i l t r a t i o n r a t e ) . The sand had an e f f e c t i v e s i z e of 0.2 mm. -56-TABLE 13 APPLIED EFFLUENT QUALITY - THOMAS (24) parameter Thomas' value (average) Cromaglass type D mg/1 mg/1 COD 198 218 BOD 87 85 SS 50 79 VSS 40 NH3~N 24 22 ORG N 6.7 11. 8 pH 7-8.1 u n i t s 7-7.9 u n i t s T °C 2-21 °C 22-31 °C I t should be emphasized th a t the a p p l i e d e f f l u e n t was of s i m i l a r q u a l i t y to tha t of the Cromaglass type D p l a n t s . The major d i f f e r e n c e to be noted i s tha t the Cromaglass e f f l u e n t has a higher d i s s o l v e d oxygen con c e n t r a t i o n . The e f f e c t of the increased D.O. may be more than o f f s e t by the greater tendency of underground systems to c l o g . A l s o , the e f f l u e n t i n Thomas' experiment was a p p l i e d only once per day. From these data, i t would appear th a t e f f l u e n t of t h i s q u a l i t y cannot be a p p l i e d at t h i s r a t e without inducing c l o g g i n g . Other authors (2, 22) have suggested t h a t average BOD and SS concentrations as low as 30 to 4 0 mg/1 would be req u i r e d before s i g n i f i c a n t l y higher loading r a t e s are permis-s i b l e . When co n s i d e r i n g beds constructed i n imported -57-m a t e r i a l , i t i s very important to measure i n f i l t r a t i o n r a t e s a f t e r the m a t e r i a l has been placed. D i s t u r b i n g " n a t u r a l " s o i l can reduce i t s i n f i l t a t i o n and p e r c o l a t i o n r a t e s from 20 to 500 times. A d d i t i o n a l l y , i f the imported s o i l i s placed on a r e l a t i v e l y impermeable s u b s o i l , s u f f i c i e n t storage must be provided i n the imported f i l l to prevent e r u p t i o n during periods of high l o a d i n g . In c o a s t a l B r i t i s h Columbia areas, t h i s may mean considerable depths of f i l l , below the a c t u a l seepage bed, w i l l be r e q u i r e d . There appears to be no reason f o r i n c r e a s i n g the load i n g r a t e s i n imported m a t e r i a l over those f o r i n s i t u m a t e r i a l of the same p e r c o l a t i o n r a t e . Most authors c a u t i o n against decreasing f i e l d s i z e on the p r o v i s i o n t h a t aerobic c o n d i t i o n s are maintained. As discussed e a r l i e r , organic matting occurs even under 'appar-e n t l y a e r o b i c 1 c o n d i t i o n s . Once anaerobic c o n d i t i o n s are i n i t i a t e d , they spread q u i c k l y and are slow to be e r a d i c a t e d . For i n s i t u beds and f i e l d s i n imported f i l l , no allowance should be made f o r aerobic c o n d i t i o n s . Another response t o . c o n s t r a i n e d . c o n d i t i o n s f o r wastewater d i s p o s a l on land, i n a d d i t i o n to improved treatment, has been the development of some 'high r a t e ' d i s p o s a l systems. Two types of systems have been developed; sand beds, and ev a p o t r a n s p i r a t i o n f i e l d s . The sand bed c o n s i s t s of a small t i l e f i e l d , l a i d e n t i r e l y i n an excavation f i l l e d w i t h sand. The e f f l u e n t i s a p p l i e d to the f i e l d at a high r a t e by discharge through p e r f o r a t e d t i l e near the surface of the f i e l d . The sand -58-serves two f u n c t i o n s . F i r s t l y , i t provides a l a r g e storage volume so t h a t the a p p l i e d e f f l u e n t does not erupt, but i n s t e a d , can p e r c o l a t e away c o n s t a n t l y through the p o o r l y permeable s u b s o i l . Secondly, the sand acts as a b i o l o g i c a l f i l t e r and r e a c t o r to remove clo g g i n g c o n s t i t u e n t s . U s u a l l y , s p e c i a l p r o v i s i o n i s made to introduce a i r i n t o these beds. The e v a p o t r a n s p i r a t i o n f i e l d f u n c t i o n s much the same as the sand bed. However, i n s t e a d of r e l y i n g on slow p e r c o l a t i o n through the s u b s o i l , l i q u i d i s removed from the f i e l d s by e v a p o t r a n s p i r a t i o n through a v e g e t a t i v e cover. In f a c t , sometimes these f i e l d s are sealed w i t h a p l a s t i c sheet on the bottom. However, both of these systems r e q u i r e a s u f f i c i e n t l y high q u a l i t y e f f l u e n t such t h a t c l o g g i n g of the. sand around the d i s t r i b u t i o n pipes does not occur. Design c r i t e r i a f o r these f i e l d s are not w e l l documented and s i g n i f i c a n t d i s p a r i t i e s e x i s t . For example, Bernhart (2) suggests an e v a p o t r a n s p i r a t i o n r a t e of 32 inches per year can be expected i n Vancouver, but Oldham (21) estimates t h i s f i g u r e to be 15 to 20 inches per year. Data on sand beds i s s i m i l a r l y divergent. -59-SUMMARY This b r i e f review of some of the l i t e r a t u r e a v a i l a b l e on d i s p o s a l f i e l d design i n d i c a t e s the widespread lack of info r m a t i o n about design c r i t e r i a . The mass of informat i o n which has been published of l a t e on large s c a l e surface d i s p o s a l techniques, a l s o i n d i c a t e s , to a s i g n i f i c a n t extent, the l a c k of understanding of the mechanisms i n v o l v e d i n ground d i s p o s a l . Recognizing these problems, r e g u l a t o r y agencies have u s u a l l y s p e c i f i e d the use of conservative design f i g u r e s . The r e l a t i v e l y recent demand f o r more " h i g h l y s t r e s s e d " wastewater c o n t r o l systems has not been adequately researched. Few authors have ventured an e s t i m a t i o n of the req u i r e d improvement i n treatment e f f i c i e n c y needed to a l l o w increased d i s p o s a l f a c i l i t y l o a d i n gs. Even, wi t h what i s p r e s e n t l y considered to be conservative design, a l a r g e number of systems f a i l . U n t i l a b e t t e r understanding of the operation of d i s p o s a l f i e l d s i s gained and a b e t t e r procedure f o r f i e l d a n a l y s i s of p o t e n t i a l d i s p o s a l areas i s developed, the use of h i g h l y loaded f i e l d s w i l l r e s u l t in- a s i g n i f i c a n t percentage of f a i l u r e s . -60-CHAPTER 5  SUMMARY AND RECOMMENDATIONS I. I n t r o d u c t i o n I t i s not d i f f i c u l t to conclude t h a t the e f f l u e n t q u a l i t y r e s u l t s of t h i s survey i n d i c a t e t h a t the Cromaglass package p l a n t s are not c o n s i s t e n t l y producing a high q u a l i t y e f f l u e n t . Whether these r e s u l t s are i n t e r p r e t e d as being r e p r e s e n t a t i v e of average f i e l d o p eration may be open to question. Every e f f o r t was made to exclude other than normal f i e l d c o n d i t i o n s during the sampling periods. The householders were very cooperative i n c a r r y i n g on normal a c t i v i t i e s w hile the survey was underway. The r e g u l a t o r y and s e r v i c e agencies made no e x t r a e f f o r t to review the p l a n t s ; nor d i d the manufac-t u r e r c a l l f o r any changes while the study was i n progress. The manufacturer l a t e r s t a t e d t h a t s e v e r a l of the u n i t s sampled were e i t h e r i n c o r r e c t l y assembled or inadequately i n s t a l l e d . Whether the same percentage of improperly f u n c t i o n i n g p l a n t s can be expected throughout the province i s d i f f i c u l t to say. The households p a r t i c i p a t i n g i n t h i s study were l a r g e l y middle c l a s s . The 1974 market value of these houses was i n the $45,000 to $60,000 range. People i n other socio-economic groups may have s u f f i c i e n t l y d i f f e r e n t h a b i t s such t h a t e f f l u e n t q u a l i t y may be improved, but t h i s i s open to s p e c u l a t i o n . However, i t i s u n l i k e l y , f o r economic reasons, t h a t Cromaglass p l a n t s would be i n s t a l l e d i n very much l e s s expensive houses. A l l o f t h e h o u s e h o l d s s u r v e y e d , e x c e p t one, were l o c a t e d i n a s i n g l e s u b d i v i s i o n . However, t h e one p l a n t f r o m o u t s i d e t h e d i s t r i c t e x h i b i t e d t h e same c h a r a c t e r i s t i c s and p r o b l e m s as t h o s e w i t h i n . I f i t i s n e c e s s a r y t o o b t a i n more i n f o r m a t i o n , t o v e r i f y w h e t h e r t h e r e s u l t s p r e s e n t e d a r e i n d e e d r e p r e s e n t a t i v e two a p p r o a c h e s c o u l d be u s e d . I t may be p o s s i b l e t o r e p e a t t h e work done d u r i n g t h i s p r o j e c t i n a s u b s e q u e n t y e a r . A l t e r n a t i v e l y , a s i m i l a r p r o g r a m i n a n o t h e r a r e a m i g h t be u n d e r t a k e n . However, now t h a t a n i n v e s t i g a t i o n h a s b e e n i n i t i a t e d , one o f t h e most i m p o r t a n t a s p e c t s o f f u r t h e r s t u d y w i l l be t o i n s u r e t h a t n o r m a l f i e l d c o n d i t i o n s and p r o c e d u r e s a r e m a i n t a i n e d . As t h i s s t u d y was l a r g e l y i n d e p e n d e n t o f m a n u f a c t u r i and r e g u l a t o r y c o n c e r n s , t h e c o n c l u s i o n s p r e s e n t e d b e l o w a r e t h o s e o f an u n b i a s e d o b s e r v e r . I I . U n i t O p e r a t i o n s I t i s d i f f i c u l t t o f o r m u l a t e c o n c l u s i o n s c o n c e r n i n g u n i t o p e r a t i o n s f r o m t h e d a t a a v a i l a b l e . Some p o i n t s c a n , however, be made: 1. T r e a t m e n t d o e s n o t a p p e a r t o be e f f e c t e d t h r o u g h t h e a c t i v a t e d s l u d g e mechanism. 2. The s e t t l i n g t a n k i n t h e t y p e D p l a n t a p p e a r s t o p e r f o r m no t r e a t m e n t f u n c t i o n . 3. The s e t t l i n g t a n k i n t h e t y p e E p l a n t a p p e a r s t o p e r f o r m no t r e a t m e n t f u n c t i o n . -62-4. In d w e l l i n g s occupied by more than four people, anaerobic c o n d i t i o n s can o f t e n be expected at the end of the 2 hour s e t t l i n g p e r i o d of the type E p l a n t s . 5. Based on l i t e r a t u r e values f o r the i n f l u e n t l o a d i n g of extended a e r a t i o n p l a n t s , i t i s evident t h a t , on the average, the p l a n t s are underloaded. The a u t o - o x i d a t i o n of microorganisms i n underloaded u n i t s may be a major cause of the very low MLVSS concentrations. In order t o increase organic and s o l i d s l o a d i n g s , i t may be d e s i r a b l e t o r e q u i r e the i n s t a l l a t i o n of garbage g r i n d e r s i n houses wit h these p l a n t s . However, as s e v e n t y - f i v e percent of the i n f l u e n t load i s o f t e n r e c e i v e d i n a s i x hour p e r i o d , conservative design i s probably j u s t i f i e d . I l l . E f f l u e n t Q u a l i t y and D i s p o s a l Systems In l i g h t of the poor understanding of c u r r e n t absorption f i e l d design c r i t e r i a , the l i t e r a t u r e i n d i c a t e s t h a t e f f l u e n t q u a l i t y must c o n s i s t e n t l y be below 40 mg/1 BOD and 50 mg/1 SS to permit s i g n i f i c a n t reductions i n present day s e p t i c tank absorption f i e l d requirements. The e f f l u e n t q u a l i t y , of n e i t h e r the CA5-D nor the CA5-E p l a n t s surveyed i n t h i s study, was s u f f i c i e n t l y high to a l l o w any r e d u c t i o n i n the s i z e of i n s i t u or imported f i l l beds. Because of the a c c e l e r a t e d r a t e of organic degradation i n sand beds or c e r t a i n s p e c i a l l y constructed f i e l d s , some r e d u c t i o n i n f i e l d l e n g t h may be p e r m i s s i b l e . -63-IV. General Observations 1. As mentioned e a r l i e r , many a e r a t i o n pump f a i l u r e s were noted during the summer of 1974. Since t h a t time, the manufacturer has changed to a pump which he f e e l s w i l l provide the necessary s e r v i c e . However, t h i s problem does underline a bas i c d i f f i c u l t y w i t h any mechanical device - the n e c e s s i t y of maintaining p a r t s i n v e n t o r i e s and s u p p l i e s . The l o g i s t i c s of a back-up s e r v i c e to se v e r a l thousand p l a n t s i s con s i d e r a b l e . 2. The frequency of s e r v i c e i n s p e c t i o n s needs to be increa s e d , e i t h e r through greater owner p a r t i c i p a t i o n or more s e r v i c e i n s p e c t i o n s . 3. Regardless of how the s e r v i c e frequency i s increased, a b e t t e r alarm system i s r e q u i r e d . 4. I n s t a l l a t i o n of a device to prevent back flow from the t i l e f i e l d to the u n i t should be mandatory. 5. U n i t s i n s t a l l e d below ground l e v e l r e q u i r e a good drainage network to prevent f l o o d i n g of the u n i t . 6. T i l e f i e l d s should be i s o l a t e d from the surrounding area by c o l l e c t o r d r a i n s . 7. At present, the f o l l o w i n g people are normally i n v o l v e d w i t h the treatment and d i s p o s a l system: 1. manufacturer 2. sales and s e r v i c e dealer 3. i n s t a l l e r of the treatment p l a n t 4. i n s t a l l e r of the t i l e f i e l d (and subcontractors) 5. c o n t r a c t o r f o r the house 6. Health i n s p e c t o r -64-7. householder (often i n h e r i t s the product of the foregoing) 8. householder's lawyer I f a reasonable degree of c o n t r o l over e f f l u e n t q u a l i t y , s e r v i c e , and i n s t a l l a t i o n i s to be maintained, .some-of these people must be e l i m i n a t e d . From the p o i n t of view . of the manufacturer, r e g u l a t o r y agency, and the householder, i t would be d e s i r a b l e to have a s i n g l e concern who would be r e s p o n s i b l e f o r the i n s t a l l a t i o n and maintenance of the e n t i r e treatment and d i s p o s a l system. In other words, the systems approach to the e n t i r e waste-management scheme i s needed. 8. Under the present system, "one-shot" h e a l t h i n s p e c t i o n i s not s u f f i c i e n t to ensure th a t h e a l t h r e g u l a t i o n s have been met by a l l of the v a r i o u s c o n t r a c t o r s i n v o l v e d i n the system i n s t a l l a t i o n and o p e r a t i o n . 9. As Chapter 4 i n d i c a t e s , the s o i l absorption system i s a complex, r a t h e r s o p h i s t i c a t e d device, which, i f i t i s to operate at high r a t e s , r e q u i r e s very c a r e f u l c o n s t r u c t i o n techniques. The education of c o n t r a c t o r s and i n s p e c t o r s , to the degree of care needed i n the p r e p a r a t i o n of these f i e l d s , i s most important. The hap-hazard c o n s t r u c t i o n witnessed during t h i s study only r e i n f o r c e s the contention t h a t many f i e l d f a i l u r e s are probably due to poor construc-t i o n technique. 10. M a t e r i a l recommended as f i l l f o r t i l e f i e l d c o n s t r u c t i o n needs to be c a r e f u l l y examined, not only i n s i t u , but a f t e r removal, t r a n s p o r t and reforming. -65-V. Householder As a general p o l i c y , i t i s probably conservative to exclude the householder w i t h respect to s e r v i c e , care, and management of the treatment and d i s p o s a l systems. Obviously, cases do e x i s t i n which the householder i s f u l l y capable and w i l l i n g to s e r v i c e h i s system. However, many homeowners " i n h e r i t " the p l a n t from a c o n t r a c t o r or previous owner w i t h l i t t l e knowledge o f, or i n t e r e s t i n , the system. In order to minimize problems throughout the l i f e of the p l a n t , i t i s s t r o n g l y suggested t h a t any system be as independent as p o s s i b l e from the householder, w i t h respect to i n s t a l l a t i o n , o p e r a t i o n , and maintenance. -66-SUMMARY Regardless of the somewhat negative conclusions of t h i s r e p o r t , there remains a demand f o r high e f f i c i e n c y waste-water treatment i n o u t l y i n g areas. The theory of on- t h e - l o t systems i s fundamentally sound. I t i s based on a philosophy of low cost and l i t t l e maintenance, j u s t i f i e d on the b a s i s of la r g e overdesign f a c t o r s . When these overdesign f a c t o r s are eroded, i n order t o remain w i t h i n the c o n s t r a i n t s of l o t s i z e and ground.conditions, cost and maintenance requirements w i l l i n c r e ase. The recommendations discussed above must then be considered i n l i g h t of t h e i r a f f e c t on the cost of wastewater management (14, 23). Obviously, the d e s i r e of r u r a l Regional D i s t r i c t s to have i n d i v i d u a l s , r a t h e r than d i s t r i c t s , assume wastewater management costs w i l l be a major f a c t o r i n t h i s a n a l y s i s . However, the fundamental co n c l u s i o n of t h i s study, t h a t improved treatment performance i s apparently not yet capable of o f f - s e t t i n g the problems a s s o c i a t e d w i t h h i g h - r a t e d i s p o s a l systems, remains. U n t i l these problems can be overcome, no s i g n i f i c a n t r e l a x a t i o n of t i l e f i e l d overdesign f a c t o r s should be permitted. ' -67-REFERENCES 1. . B a i l e y , J . and Wallman, H. : A Survey of Household Waste Treatment Systems, JWPCF, 43, No. 12 (1971) p.2349 2. Bernhart, A.P. : Treatment and D i s p o s a l of Wastewater  from Homes by S o i l I n f i l t r a t i o n and E v a p o t r a n s p i r a t i o n , U of Toronto Press, 2nd ed., v o l 1 (1973) 3. Brandes, M. : Studies on Subsurface Movement of E f f l u e n t  from P r i v a t e Sewage Di s p o s a l Systems using Radioactive  and Dye Tracers, i n t e r i m r e p o r t - p a r t 1 (1972), Ontario M i n i s t r y of the Environment 4. Bouma, J . : E v a l u a t i o n of the F i e l d P e r c o l a t i o n Test and an A l t e r n a t i v e Procedure to Test S o i l P o t e n t i a l f o r D i s p o s a l of S e p t i c Tank E f f l u e n t , S o i l S c i . Soc. Amer.  P r o c , 30, (1966) p.641 5. Bouma, J . , et al_ : S o i l Absorption of S e p t i c Tank E f f l u e n t , U of Wisconsin, i n f o r m a t i o n c i r c u l a r #20 (1972) 6. Carn, J.M. and Beatty, M.T. : D i s p o s a l of S e p t i c Tank E f f l u e n t i n S o i l s , Jour, of S o i l and Water Conser., 20, (1965) p.101-105 7. C o t t e r a l , J.A. and N o r r i s , D.P. : S e p t i c Tank Systems, Jour. San. Eng. Div. , ASCE P r o c , 95, (1969) p.715 8. Derr, B.D. et a_l : S o i l Factors I n f l u e n c i n g P e r c o l a t i o n Test Performance, S o i l S c i . Soc. Am. P r o c , 33, (1969) p.942-946 9. French, B. : The P h y s i c a l P r o p e r t i e s and S u i t a b i l i t y  For S e p t i c Tank D r a i n f i e l d s of a Fraser V a l l e y S o i l , undergraduate t h e s i s , UBC, (1972) 10. Hausenbuiller, R.L. : S o i l Science P r i n c i p a l s and P r a c t i c e s , W.C. Brown Company (1972) 11. Healy, K.A. and Laak, R. : Factors A f f e c t i n g the P e r c o l a -t i o n Test, JWPCF, 45, No. 7, (1973) p.1509 12. H i l l e l , D. : S o i l and Water: P h y s i c a l P r i n c i p l e s and  Processes, New York, Academic Press (1971) 13. Huddleston, J.H. and Olson, G.W. : S o i l Survey I n t e r p r e t a -t i o n For Subsurface Sewage D i s p o s a l , S o i l Science, 104, No. 6 (1967) p.401-409 14. Lamp, G.E. : Package Treatment P l a n t P r i c e s , JWPCF, 46, No. 11 (1974), p.2605 15. Lawrence, C.H. : S e p t i c Tank Performance, J.E.H., 36, No. 3, (1973), p.226 -68-16. Ligman, K. , et a_l : Household Wastewater C h a r a c t e r i s t i c s , Jour. Env. Eng. Div., ASCE, No.2 (1974) p.201 17. McGauhey, P.H. and Winneberger, J.H. : A Study of  Methods of Preventing F a i l u r e of S e p t i c Tank P e r c o l a t i o n  Systems, U.S. Dept of Housing and Urban Development (1968) 18. Me t c a l f and Eddy Inc. : Wastewater Engineering, McGraw H i l l , (1972) 19. Mink, L.L. : S e p t i c Tank Performance Under High Water Table C o n d i t i o n s , presented at the PNPCA conference i n Richland, Washington (1974) 20. Oldham, W.K. , et a_l : Canada - B r i t i s h Columbia Okanagan Basin Agreement, Task 139 (part t h e r e o f ) , Estimate of T o t a l N u t r i e n t s U l t i m a t e l y Reaching Receiving Waters i n Groundwater, (1972) 21. Oldham, W.K. : (professor UBC) p r i v a t e conversations (1974) 22. Reid, L.C. : Design of Wastewater D i s p o s a l Systems f o r I n d i v i d u a l Dwellings, JWPCF, 43, No. 10 (1971) p.2004 23. Thomas, H.A. , et a_l : Technology and Economics of Household Sewage Di s p o s a l Systems, JWPCF, 32, No. 2, (1960) p.113 24. Thomas, R.E., et al_ : S o i l Chemical Changes and I n f i l t r a -t i o n Rate Reduction Under Sewage Spreading, S o i l S c i .  Soc. Amer. Proc., 30, (1966) p.641 25. Winneberger, J.T. : Septic-Tank P r a c t i c e s , A r i z o n a , p a r t 2, (1972) 26. de V r i e s , J . : S o i l I n f i l t r a t i o n of Wastewater E f f l u e n t and the Mechanism of Pore Clogging, JWPCF, 44, No. 4, (1972) p.565 27. Zanoni, A.E. and Rutkowski, R.J. : Per Capita Loadings of Domestic Wastewater, JWPCF, 44, No.9, (1972) p.1756 -69-APPENDICES -7 0-APPENDIX 1 - P e r c o l a t i o n Testing As noted i n Chapter 4, one of the gre a t e s t d i f f i c u l -t i e s i n the design of d i s p o s a l f i e l d s , i s the la c k of accurate design parameters. This problem i s l a r g e l y due to the i n a b i l i t y t o r e l a t e long term t i l e f i e l d o p eration to a simple, r e l i a b l e f i e l d t e s t procedure. For many years, the p e r c o l a t i o n t e s t has been used t o ca t e g o r i z e s o i l s . The " p e r c o l a t i o n t e s t " was f i r s t used by Ryon i n the mid 1920's. He proposed and u t i l i z e d a r e l a t i v e l y standard t e s t , i n conjunction w i t h some f i e l d f a i l u r e data, to p r e d i c t the s u i t a b i l i t y of va r i o u s s o i l s f o r seepage f i e l d i n s t a l l a -t i o n . His t e s t , much maligned and poorly understood, remains as v i r t u a l l y the only measure f o r f i e l d design i n widespread use today. However, i t i s almost u n i v e r s a l l y agreed t h a t t h i s n o n - s p e c i f i c , p o o r l y standardized, inadequately understood, o f t e n one-shot t e s t has no simple c o r r e l a t i o n w i t h the long term a b i l i t y of a s o i l to accept e f f l u e n t . Most authors f e e l t hat the t e s t , p r o p e r l y performed, under standard c o n d i t i o n s , w i l l a l l o w a very rough c a t e g o r i z a t i o n of s o i l s to be made. However, even when t e s t i n g i s c a r r i e d out under very c l o s e l y c o n t r o l l e d c o n d i t i o n s , by s k i l l e d t e c h n i c i a n s , the v a r i a b i l i t y of the r e s u l t s make them d i f f i c u l t to i n t e r p r e t . An examination of some of the inherent problems of the "standard p e r c o l a t i o n t e s t " (SPT) w i l l serve to unde r l i n e these d i f f i c u l t i e s . The SPT i s u s u a l l y one of two b a s i c t e s t s . The most common, the f a l l i n g head t e s t , apparently i s l e s s r e p r o d u c i b l e . -71-The s t a t i c head t e s t , although h i g h l y v a r i a b l e , i s somewhat b e t t e r . At present, most agencies do not s t r i c t l y d e f i n e how a p e r c o l a t i o n t e s t should be c a r r i e d out. Depth and diameter of the hole, water l e v e l s , number of f i l l i n g s before measurement, weather c o n d i t i o n s , number of holes per s i t e , q u a l i t y of water used i n the t e s t , number of days upon which the t e s t must be performed, and experience of t e s t i n g personnel are but l o o s e l y o u t l i n e d . The importance of c a r e f u l d e f i n i t i o n and c o n t r o l of these parameters i s i l l u s t r a t e d i n the l i t e r a t u r e . Healy and Laak (11) compared a mathematical model wit h l a b o r a t o r y and f i e l d data. They make the f o l l o w i n g c o n c l u s i o n s . 1. P e r c o l a t i o n r a t e w i l l not decrease s i g n i f i c a n t l y a f t e r two f i l l i n g s of the t e s t hole. 2. A p e r c o l a t i o n hole i n any s o i l except sand or g r a v e l w i l l y i e l d a wide range of p e r c o l a t i o n r a t e s depending on the degree of s a t u r a t i o n of the s o i l d eposit at the time of the t e s t . Confirmed wi t h both f i e l d and l a b o r a t o r y t e s t i n g . 3. Test hole shape can s i g n i f i c a n t l y a f f e c t p e r c o l a t i o n r a t e s (up to f a c t o r s of 6 or more). 4. Depth to the water t a b l e has a great e f f e c t on p e r c o l a t i o n r a t e even a f t e r the s o i l s have been soaked twice (for water t a b l e s l e s s than 6 f t . ) . 5. P e r c o l a t i o n r a t e s v a r i e d from 20 to 90 times the "permeabil-i t y " ( h y d r a u l i c c o n d u c t i v i t y , K) i n l a b o r a t o r y t e s t s . The lower the P.R./K r a t i o s occurred at the f a s t e r p e r c o l a -t i o n r a t e s . 6. D i s t u r b i n g the s o i l r e s u l t e d i n a p e r m e a b i l i t y decrease of 10 to 200 times. 7. The saturated p e r m e a b i l i t y was from 2 to 40 times greater than the unsaturated value. Laboratory data i n d i c a t e t h a t K . i s probably 2 to 3 times K .. S a t U n Sat 8. "The p e r c o l a t i o n r a t e i s not a measure of the e f f e c t i v e absorption p r o p e r t i e s of a s o i l d eposit and should not -72-be used as a b a s i s f o r determining allowable h y d r a u l i c loads on seepage beds. Bouma (4) presents Table A l - 1 as a comparison of some t e s t methods c a r r i e d out under standardized c o n d i t i o n s ( c o e f f i c i e n t of v a r i a b i l i t y f o r each t e s t s i t e i n brackets) TABLE A l - 1 S o i l type P e r c o l a t i o n F a l l i n g Head Rate cm/day S t a t i c Head K s a t cm/day s i l t loam 160 (41) 360 (35) 60 (25) s i l t loam 200 (45) 600 (30) 28 (25) s i l t loam 420 (82) 600 (30) 95 (30) s i l t loam 1200 (30). 1200 (20) 80 loamy sand 16 00 (30) 1800 (20) 300 (20) Apparently the most re p r o d u c i b l e t e s t i s the i n s i t u s a turated h y d r a u l i c c o n d u c t i v i t y measurement. He a l s o concludes t h a t the p e r c o l a t i o n r a t e i s s i g n i f i c a n t l y a f f e c t e d by s o i l moisture content and the depth of the water i n the t e s t hole. Derr et a l (8) attempted to c o r r e l a t e v a r i o u s s o i l c h a r a c t e r i s t i c s and other f a c t o r s w i t h p e r c o l a t i o n r a t e s . They conclude 1. On the average, v a r i a b i l i t y c o e f f i c i e n t s of 73 percent can be expected w i t h i n an i n d i v i d u a l d i s p o s a l s i t e . However t h i s v a r i a b i l i t y can range from 0 to over 250%. 2. "The v a r i a b i l i t y between i n d i v i d u a l t e s t s w i t h i n s i t e s on the same s o i l i s g e n e r a l l y greater than the v a r i a b i l i t y between i n d i v i d u a l t e s t s at a s i t e . Furthermore, the v a r i a b i l i t y between s i t e medians on d i f f e r e n t s o i l s e r i e s i s g r e a t e r , but not g e n e r a l l y s i g n i f i c a n t l y d i f f e r e n t , than the v a r i a t i o n between s i t e medians on the same s o i l s e r i e s . " -73-3, "The p e r c o l a t i o n t e s t i s i n f l u e n c e d by a complex a s s o c i a t i o n of s o i l and environmental c h a r a c t e r i s t i c s and the v a r i a b i l -i t y caused by t h i s complexity reduces the r e l i a b i l i t y of p e r c o l a t i o n t e s t r e s u l t s . " Winneberger (25) c a r r i e d out an extensive a n a l y s i s of p e r c o l a t i o n data c o l l e c t e d i n Arizona and southern C a l i f o r n i a . He found p e r c o l a t i o n r a t e s are s i g n i f i c a n t l y a f f e c t e d by: 1. The depth to which the t e s t hole i s f i l l e d 2. The surface area to volume r a t i o of the t e s t hole, 3. The method of digg i n g the hole (manual versus power auger) 4. The person who performs the t e s t 5. The device used to measure the water drop. The extent of some of these e f f e c t s i s shown i n Table A l - 2 . However, even a f t e r presenting the data i n Table A l - 2 , Winneberger suggests a standardized p e r c o l a t i o n t e s t i s s t i l l the best p r a c t i c a b l e method f o r c a t e g o r i z i n g s o i l s . In c o n t r a s t , Bouma et_ a_l (5) , a f t e r an extensive study of s e v e r a l t i l e f i e l d s which had been operating f o r periods of a few months t o 25 years, makes the statement, " P e r c o l a t i o n t e s t r e s u l t s , do not p r e d i c t the i n f i l t r a t i o n r a t e s as they occur from seepage trenches." The consensus of the l i t e r a t u r e i s that the SPT i s a very poor method of determining s o i l s u i t a b i l i t y . However, there are two d i s t i n c t r e a c t i o n s to t h i s problem. The p o l l u t i o n c o n t r o l engineers, r e g u l a t o r y agencies, and c o n s t r u c t i o n people p r e f e r a w e l l defined p e r c o l a t i o n t e s t ; probably as much f o r h i s t o r i c reasons as any other. The s o i l s c i e n t i s t s are i n favour of the i n s i t u saturated h y d r a u l i c c o n d u c t i v i t y -74-TABLE Al-2 Test Parameters 1. Width of Hole narrow hole (dia 3.3") wide hole (dia 13") 2. Method of Digging Hole l o c a t i o n A B C D E 3. Depth of Water i n Hole depth of hole 8" 18" 14" 18" 50" 54" S t a b i l i z e d P e r c o l a t i o n Rate 33 i n / h r (1.82 min/in) 9.6 i n / h r (6.25 min/in) hand auger 5.0 min/in 4.3 2.4 0.8 10 f i r s t f i l l i n / h r 116 292 1860 power auger 240 min/in 120 >60 80 240 second f i l l i n / h r 148 204 4. Personnel l o c a t i o n personnel number #1 #2 #3 1 23 min/in 118 min/in 37 2 15 59 172 3 2 15 32 4 130 91 161 5 5 59 73 6 2 12 24 7 3 39 229 8 4 22 34 9 19 63 • 259 - 7 5 -method. In terms of f i e l d performance, both experience d i f f i -c u l t i e s . The extent of p e r m i s s i b l e overdesign of the f i e l d w i l l govern the degree of refinement r e q u i r e d i n the permeabil-i t y t e s t i n g procedure. I f i t i s p r a c t i c a l l y and economically f e a s i b l e to i n s t a l l f i e l d s w i t h a 50% overdesign, there i s probably l i t t l e need f o r a r e f i n e d t e s t . However, where small l o t s i z e and poor s o i l c o n d i t i o n s e x i s t , a good estimate of the long term p e r c o l a t i o n c a p a c i t y i s r e q u i r e d . In response to the apparent need f o r small systems w i t h high loading r a t e s , other t e s t s have been researched. The most o f t e n suggested a l t e r n a t i v e i s the in_ s i t u , s a t urated, double-tube, h y d r a u l i c - c o n d u c t i v i t y t e s t . Bouma, de V r i e s and others have used t h i s t e s t . A comparison of the SPT and the h y d r a u l i c c o n d u c t i v i t y t e s t w i t h a c t u a l t i l e f i e l d i n f i l t r a t i o n r a t e s i s i l l u s t r a t e d i n Table Al-3 (4). TABLE Al-3 a c t u a l flow HC SPT Q/A Q/A (Q/A) HC SPT L/day L/day L/day 2500 261000 1392000 0.0096 0.0018 280* 19000 288000 0.0147 0.0010 800* 19000 288000 0.0421 0.0028 16 22.5 225 0.7111 0.0711 * Data from same f i e l d . Second value taken a f t e r r e s t i n g -76-The important feature of Table Al-3 i s the r a t i o s between the t e s t and the a c t u a l l o a d i n g r a t e . For each t e s t , e x c l u d i n g the l a s t s i t e , the measured r a t e to t e s t value r a t i o v a r i e s by a f a c t o r of approximately three to four . Thus, although these r a t i o s d i f f e r by an order of magnitude i n each case, one does not appear t o be s i g n i f i c a n t l y more r e p r o d u c i b l e than the other. Some have argued that the h y d r a u l i c c o n d u c t i v i t y t e s t i s more d i f f i c u l t to perform than the SPT. However, when the SPT i s p r o p e r l y performed, t h i s does not appear t o be a v a l i d p o i n t . French (9) suggested using the h y d r a u l i c c o n d u c t i v i t y t e s t to e s t a b l i s h l o a d i n g r a t e s f o r r e p r e s e n t a t i v e s o i l s . Then, i n s t e a d of performing i n f i l t r a t i o n r a t e t e s t s at each s i t e , samples of the s o i l p r o f i l e would be analyzed. The r a t e determining l a y e r could then be found from the h y d r a u l i c c o n d u c t i v i t y data on the nearest r e p r e s e n t a t i v e s o i l . The only d i f f i c u l t y w i t h t h i s approach i s the great v a r i e t y and non-homogeneity of B r i t i s h Columbia s o i l s . This problem occurs to such an extent t h a t s e v e r a l p r o f i l e s would be r e q u i r e d at each s i t e . The expense and time r e q u i r e d f o r t h i s a n a l y s i s may be p r o h i b i t i v e . A s i m i l a r approach has been suggested by Huddleston and Olson (13). They conducted SPT 1s on approximately f i f t e e n recognized s o i l types. These s o i l types were w e l l documented ge o g r a p h i c a l l y on r e a d i l y a v a i l a b l e s o i l survey maps. Thus, they proposed system design on the b a s i s of the s o i l type designated on the survey map. -77-However, i n order t o provide f o r l o c a l d i f f e r e n c e s i n s o i l s t r u c t u r e , they proposed t h a t the p e r c o l a t i o n r a t e assigned to each s o i l type be the average of the measured p e r c o l a t i o n r a t e s plus one standard d e v i a t i o n . And to add a f u r t h e r conservative feature to t h e i r design suggestions, they proposed th a t three c a t e g o r i e s of p e r c o l a t i o n r a t e would be used. Any s o i l w i t h a p e r c o l a t i o n r a t e plus SD between 0 and 30 min/in i s s u i t a b l e f o r i n s i t u bed c o n s t r u c t i o n . From 30 t o 90 min/in imported f i l l must be used and f o r s o i l s g reater than 90 min/in, sand f i l t e r s are s p e c i f i e d . They f e e l then, t h a t the use of the above c r i t e r i a , i n conjunction w i t h s o i l survey maps, w i l l e l i m i n a t e a l t o g e t h e r , the need f o r any o n - s i t e t e s t i n g . This proposal s u f f e r s from the same d e f i c i e n c y as French's. C e r t a i n l y , i n some areas i t might be p r a c t i c a l but, f o r use as a province wide standard, i t i s not s u i t a b l e . To the present, there does not appear to have been developed a p r a c t i c a l t e s t which i s simply r e l a t e d to the long term c a p a c i t y of a s o i l to accept e f f l u e n t . The l i t e r a t u r e , f o r p r a c t i c a l and t r a d i t i o n a l reasons, favours the use of the standard p e r c o l a t i o n t e s t . The h y d r a u l i c c o n d u c t i v i t y t e s t appears to be at l e a s t as good and perhaps b e t t e r . However, a l l of the l i t e r a t u r e s t r e s s e s the need f o r standardized t e s t procedures c a r r i e d out by t r a i n e d , experienced personnel. -78-APPENDIX 2 .- Waste C h a r a c t e r i s t i c s Most of the data a v a i l a b l e i n standard t e x t s f o r per c a p i t a water consumption and l i q u i d waste generation are based on averages computed f o r l a r g e municipal areas. They do not a c c u r a t e l y r e f l e c t the a c t u a l use of water on an i n d i v i d u a l household b a s i s . Many agencies have used the value of 75 US g a l per c a p i t a per day (approximately 61 Igal/c/day) as the b a s i s f o r design r e g u l a t i o n s . This f i g u r e i s used f o r the s i z i n g of s e p t i c tanks, other treatment u n i t s and t i l e f i e l d s . Peak flow estimates are a l s o much d i f f e r e n t f o r s i n g l e f a m i l y d w e l l i n g s than municipal systems. Peaks of two to four times the average may be encountered i n municipal systems where an i n d i v i d u a l household may discharge peaks of 6 to 10 times the d a i l y average. A l s o , f o r a lar g e p o r t i o n of the day, the i n f l o w to the s i n g l e f a m i l y u n i t i s zero. Table A2-1 i l l u s t r a t e s some per c a p i t a per day flow r a t e s f o r i n d i v i d u a l d w e l l i n g s taken from the l i t e r a t u r e . The average of these i s approximately 41 Igal/c/day. A f a m i l y of four would then be expected to discharge an average of 164 Igal/day. A l l o w i n g an overdesign f a c t o r of approximately 2 i n d i c a t e s that conservative design could be based on 325 Igal/day. For comparison, Table A2-2 contains the water consumption data f o r the houses sampled during t h i s study plus some others i n the neighbourhood (data from the GVWD). I t should be noted t h a t during the per i o d when most o f these water readings were c o l l e c t e d , the m a j o r i t y of the homeowners -79-TABLE A2-1 WASTE WATER FLOW infor m a t i o n source flow g/cap'/day (Imp) # of people 1. S e p t i c Tank Performance 2, 3, 4, C,H, Lawerence 36 #3 J.E.H. 25. 8 measured p226 40. 8 measured A.P. Bernhart 44 Zanoni and Rutkowski 48 Ligman H u t z l e r & Boyle 15 to 57 l i t e r a t u r e review l i s t 40. 6 vari o u s r e f 41 17. 7 to 43.6 25 34. 1 to 6 9.1 10. 8 to 48.3 48. 3 to 114 39. 1 29. 1 to 41.6 41. 6 to 74.9 23. 3 40 37. 0 Bouma et a l 26. 4 measured 41. 6 measured 36. 1 measured 34. 7 measured Zanoni and Rutkowski 54. 1 measured 37. 5 measured 20. 8 measured 4.8. 3 (average (6) (5) (3) (3) (3) (6) average 4 0.9 Igal/c/day TABLE A2-2 House Dish Auto No. of Number Washer Washer people days of week used 1 None Yes 3 2 Yes Yes 2 3 Yes Wringer 1 6 4 None Yes 7 4 5 None Yes 7 4 6 None Yes 7 3 7 None Yes 2 4 8 None Yes 5 9 Yes Yes. 2 10 None Yes 1 4 11 None Yes 2 12 - Yes 2 13 None Yes 5 14 Yes Yes 2 15 None Yes 7 5 16 Yes Yes 2 17 None Yes 7 9 18 L i t t l e use Yes 2 19 None None 2 2 0 None Yes 7 21 None Yes 7 22 None Yes 23 None Yes 24 None Yes 25 None Yes 26 None Yes 2 27 Yes Yes 28 None L i t t l e use 2 9 None Yes 1 Average Water Use gal/month g/person/d t o t a l 3000 32 600 10 4600 25 5800 46 4400 36 5000 54 4200 34 4700 30 2000 33 2800 23 1900 30 3700 60 16200 105 5600 90 8100 52 3700 60 high 2 3500 57 4734 76 5 6300 41 4 4300 35 2 4000 65 2 3200 52 2 4900 79 2 3800 62 2 3115 50 3 3600 39 3 2500 27 4 2800 23 average exc l u d i n g house #13 45.2 0^,-standard d e v i a t i o n 19.28 -81-were using very l i t t l e water which d i d not enter the treatment system (the neighbourhood had few gardens and most of the data was c o l l e c t e d during the winter when outside a c t i v i t i e s were at a minimum). The average of these f i g u r e s , excluding one household which was using a l o t of water f o r masonry construc-t i o n , i s 45.2 Igal/c/day. In t h i s case, the f a m i l y of four would be expected to use 181 Igal/day. Conservative design i n t h i s case would be f o r 360 Igal/day. Figure A2-1 i n d i c a t e s , as expected, t h a t per c a p i t a consumption r a t e s are somewhat higher f o r houses wi t h low populations but l e v e l o f f f o r households w i t h more than three people. The problem of peak loadings i s d i f f i c u l t to design f o r . For example, flows can increase from zero to 20 gpm w i t h the removal of the bathtub plug. Normally, as w i t h municipal p l a n t s , peak loadings occur between 0800 and 1000 hrs. and 1700 and 1900 h r s . . However, e r r a t i c flow behaviour can occur at any time. The same t e x t s , which supply sewage flow r a t e data, a l s o supply per c a p i t a organic loadings derived from mu n i c i p a l averages. Generally speaking, these f i g u r e s are not a p p l i c a b l e to i n d i v i d u a l households. Ligman et a_l (16) conducted a d e t a i l e d study of waste c h a r a c t e r i s t i c s from r u r a l and urban d w e l l i n g s . Their r e s u l t s (which i n c l u d e data from an extensive l i t e r a t u r e survey) are summarized wi t h others i n Table A2-3.. From the f i g u r e s i n Table A2-3, i t i s evident that organic peaks occur and t h a t these do not n e c e s s a r i l y c o i n c i d e -82-FIGURE A2-1 -83-TABLE A2-3  HOUSEHOLD WASTE CHARACTERISTICS 1. r e f Ligman et a l (16) Wastewater Event C h a r a c t e r i s t i c s i n l b s per c a p i t a per day Water event BODs T o t a l SS T o t a l T o t a l Fats S o l i d s N P (dry wt) (dry wt) bath/shower 0. 020 0. 046 0. 012 - - -dishwashing 0. 013 0. 022 0. 006 - 0. 001 -garbage d i s p o s a l 0. 068 . 0. 135 0. 096 0. 002 - .0.017 c l o t h e s washer 0. 021 .0. 088 o. 016 - 0. 005 -T o i l e t feces 0. 025 0. 060 0. 048 0. 003 0. 001 0.010 uri n e 0. 023 0. 132 - 0. 034 0. 002 -paper 0. 004 0. 022 0. 020 - - -Average a d u l t c h a r a c t e r i s t i c s 0. 174 0. 505 0. 198 - 0. 009 -Average a d u l t c h a r a c t e r i s t i c s without garbage 0. 106 0. 370 0. 102 0. 009 2. r e f Benhart(2) lb/cap/day average a d u l t c h a r a c t e r i s t i c s without garbage g r i n d i n g 0.082 - 0.132 0.115 - 0.143 -84-w i t h the h y d r a u l i c peaks. The average BOD co n c e n t r a t i o n f o r an a d u l t occupying a d w e l l i n g which does not have a garbage g r i n d e r can be c a l c u l a t e d as f o l l o w s : 0.106 x _ J _ day_cap x 1 Q 6 g a l x _1' mg/1 ~ 2 6 0 _ 2 3 5 m g / 1 cap day 41-45 I g a l MG 10 lb/MG Peak concentrations as high as 600 mg/1 are not uncommon. However, a great p r o p o r t i o n of the time, there i s no i n f l u e n t to the treatment u n i t . To achieve an e f f l u e n t of approximately 50 mg/1, an e i g h t y percent removal i s r e q u i r e d but to achieve 30 mg/1 BOD a n i n e t y percentage e f f i c i e n c y i s needed. Considering the i r r e g u l a r i n f l u e n t p a t t e r n , treatment e f f i c i e n c y must range from zero to almost one hundred percent at v a r i o u s times during the day. These e r r a t i c waste c h a r a c t e r i s t i c s only compound the problems of small s c a l e treatment design. -85-APPENDIX 3 - T e s t i n g and A n a l y s i s  Tests The l i t e r a t u r e i s f a r from agreement on which parameters are of importance when ana l y z i n g an e f f l u e n t which i s to be a p p l i e d to the s o i l . Most authors agree DO, SS and n u t r i e n t concentrations have s i g n i f i c a n t impacts on the s o i l i n the d i s p o s a l s i t e . I t has been suggested (2) t h a t a c i l i a t a count would be of value i n determining how q u i c k l y c l o g g i n g b a c t e r i a w i l l be removed. However, the g r e a t e s t d i v e r s i t y of o p i n i o n e x i s t s i n how to measure the organic content of the e f f l u e n t . The standard f i v e day BOD t e s t i s most o f t e n used; probably f o r t r a d i t i o n a l and comparatory reasons. As noted i n Chapter 3, there appears to be very l i t t l e c o r r e l a t i o n , i f any, of BOD w i t h e i t h e r COD or TOC. In terms of s o i l c l o gging p o t e n t i a l , the important organic measurement i s oxygen u t i l i z a -t i o n , while the e f f l u e n t i s i n the v i c i n i t y of the t i l e f i e l d . However, i n g r a v e l s o i l s , the important organic measurement may be the r e s i d u a l BOD discharged to groundwater. In a d d i t i o n , there i s the long standing d i s s a t i s f a c -t i o n w i t h the BODj- t e s t i n general. However, u n t i l i t can be demonstrated t h a t another parameter i s b e t t e r c o r r e l a t e d w i t h t i l e f i e l d r e s u l t s , the BOD,, t e s t w i l l continue to be used. Analyses A l l samples were d e l i v e r e d to the Chemistry Labora-t o r y of the Water Resources S e r v i c e i n V i c t o r i a f o r a n a l y s i s . Samples were stored i n c o o l e r s w i t h i c e packs i f not d e l i v e r e d -86-w i t h i n e i g h t hours of c o l l e c t i o n . A l l samples were turned over to the l a b w i t h i n twenty hours of c o l l e c t i o n . A l l a n a l y s i s were c a r r i e d out i n accordance w i t h the procedures adopted by the Water Resources S e r v i c e . The COD t e s t procedure deserves s p e c i a l d i s c u s s i o n . I t i s the p o l i c y of the Chemistry Lab to perform a s t a r c h -i o d i d e t e s t f o r r e s i d u a l c h l o r i n e compounds on a l l samples i t r e c e i v e s f o r BOD a n a l y s i s . A p o s i t i v e t e s t i n d i c a t e s the presence of a strong o x i d i z i n g agent. Table A3-1 shows tha t the amount of o x i d i z i n g agent c o r r e l a t e s w e l l w i t h the amount of n i t r i t e i n the sample. O r t h o t o l i d i n e - a r s e n i t e t e s t s d i d not i n d i c a t e the presence of C h l o r i n e compounds. Thus, n i t r i t e and not c h l o r i n e may be re s p o n s i b l e f o r the p o s i t i v i e s t a r c h -i o d i d e t e s t . TABLE A3-1 Sample Mg/L NO" ** ml C l 2 n e u t r a l i z e d * 1 1.9 3.5 2 2.0 3.0 3 2.9 2.5 4 0.103 n i l 5 0.107 n i l 6 0.129 n i l * ml of the o x i d i z i n g compound i n d i c a t e d by the s t a r c h - i o d i d e t e s t ** The N O 2 t e s t used by the Chemistry Lab i s subject to i n t e r f e r e n c e s by sulphide and f r e e c h l o r i n e and has a d e t e c t i o n l i m i t of 0.005 mg/1 N f o r e x t r a c t e d samples -87-However, i f a sample shows a p o s i t i v e s t a r c h - i o d i d e t e s t , i r r e g a r d l e s s of the cause, the Chemistry Lab n e u t r a l i z e s the sample wi t h sodium s u l f i t e and seeds the sample wi t h s e t t l e d m u n i c i p a l sewage. Table A3-2 i n d i c a t e s t h a t a s i g n i f i -cant d i f f e r e n c e i n BOD,, e x i s t s between seeded and unseeded samples. TABLE A3-2 Five day BOD i n mg/1 sample seeded No s u l f i t e unseeded No s u l f i t e number s u l f i t e seeded s u l f i t e No seed 1 78 59 69 52 2 78 56 66 55 3 76 55 59 54 4 69 61 66 57 average of four samples 75 58 65 55 The a d d i t i o n of the s u l f i t e has a much gre a t e r a f f e c t on the r e s u l t s than does the seeding. The d i f f i c u l t y a r i s e s when comparing r e s u l t s from the Chemistry Lab and p r i v a t e l a b o r a t o r i e s . The p r i v a t e l a b s , i f t o l d a sample does not or should not con t a i n any r e s i d u a l c h l o r i n e compounds, do not perform the s t a r c h - i o d i d e t e s t and consequently do not n e u t r a l i z e or seed. Thus, s i g n i f i c a n t d i f f e r e n c e s can r e s u l t from these two d i f f e r e n t procedures. Approximately e i g h t y - f i v e percent of the samples -88-c o l l e c t e d t h i s summer had p o s i t i v e s t a r c h - i o d i d e t e s t s . As the p r o v i n c i a l government i s the t e s t i n g and r e g u l a t o r y agency f o r these systems, the data, as would be presented by the Chemistry Lab under normal circumstances, w i l l be used. In the m a j o r i t y of cases, t h i s means the BOD t e s t r e s u l t s are from samples which have been n e u t r a l i z e d and seeded. 

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