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Treatment of a municipal landfill leachate Lee, Ching Jiang 1979

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TREATMENT OF A MUNICIPAL LANDFILL LEACHATE by CHING JIANGiLEE M . S c , U n i v e r s i t y o f A l a s k a , 1973 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OP GRADUATE STUDIES i n the Department B.Sc N a t i o n a l Taiwan U n i v e r s i t y , 196 8 of C i v i l E n g i n e e r i n g We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA January, 197 9 © Ching J i a n g Lee, 1979 In presenting th is thes is in p a r 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 l y ava i lab le for reference and study. I fur ther agree that permission for extensive copying of th i s thes is for scho la r l y 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 is thes is for f i nanc ia l gain sha l l not be allowed without my wri t ten permission. Department of C i v i l Engineering The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V 6 T 1W5 Date January 8, 1979 ABSTRACT One of the problems a s s o c i a t e d with the d i s p o s a l of s o l i d wastes i n l a n d f i l l s , p a r t i c u l a r l y i n hig h p r e c i p i t a t i o n areas, i s the p o l l u t i o n caused by the p r o d u c t i o n of the o f t e n h i g h l y contaminated l e a c h a t e . T h i s study was i n i t i a t e d t o i n v e s t i g a t e the t r e a t a b i l i t y of a low-strength m u n i c i p a l l a n d f i l l l e a c h a t e u s i n g a e r o b i c d i g e s t i o n f o l l o w e d by a c t i v a t e d carbon p o l i s h i n g , , so t h a t the most c o s t e f f e c t i v e treatment system c o u l d be d e t e r -mined. Sludge d e s o r p t i o n and lea c h a t e t o x i c i t y assessment were a l s o i n c l u d e d i n the study. The a e r a t e d lagoon process alone was very e f f e c t i v e i n t r e a t i n g the leac h a t e t o a q u a l i t y t h a t i s n e a r l y a c c e p t a b l e f o r d i s c h a r g e t o a r e c e i v i n g water. Only SO4 and Fe i n the s e t t l e d e f f l u e n t s i g n i f i c a n t l y exceeded the l o c a l r e q u l a t o r y standards f o r s p e c i f i c d i s c h a r g e s . Carbon a d s o r p t i o n g r e a t l y improved the s e t t l e d e f f l u e n t q u a l i t y i n terms of c o l o r , Fe and COD. However, the a d d i t i o n of t h i s p o l i s h i n g process f o r combined treatment may not be cos t e f f e c t i v e . For an i n f l u e n t COD of 1,600 mg/1 and with MLVSS concen-t r a t i o n s ranging between 360 and 560 mg/1, the s e t t l e d e f f l u e n t COD removal i n c r e a s e d from 82.6% t o as high as 90.1% when 9 C was i n c r e a s e d from 2 t o 10 days. For the corresponding i n f l u e n t BOD5 of about 1,000 mg/1 and with 9 C g r e a t e r than 3 days, the BOD5 removal e f f i c i e n c i e s averaged 99.1% and the s e t t l e d e f f l u e n t BOD 5's were no g r e a t e r than 10 mg/1. T h i s i i i n d i c a t e s t h a t the raw le a c h a t e can be almost completely biodegraded by a e r o b i c d i g e s t i o n . The metal removal e f f i c i e n c y i n a e r o b i c treatment was gr e a t e r " t h a n 95% f o r Fe and Mn, b e t t e r than 90% f o r Zn and Pb, and about 80% f o r A l . Metals expected t o be mainly or s i g n i -f i c a n t l y removed by chemical p r e c i p i t a t i o n due t o pH change du r i n g treatment i n c l u d e d Ca, Fe, Mn, Zn and Pb. A n a l y s i s of the k i n e t i c parameters a s s o c i a t e d with the b i o l o g i c a l treatment i n d i c a t e d t h a t the c o n c e n t r a t i o n s o f p o l l u t a n t s , such as heavy metals, i n the leach a t e were not g r e a t enough t o cause s i g n i -f i c a n t i n h i b i t i o n of b i o l o g i c a l growth. I t a l s o showed t h a t t h i s l e a c h a t e c o u l d very l i k e l y be added to a domestic sewage, i n a h i g h percentage, f o r a e r o b i c treatment without producing adverse e f f e c t s . From a treatment e f f i c i e n c y p o i n t of view, the optimum s o l i d s d e t e n t i o n time was found t o be 7 to 10 days f o r l e a c h a t e BOD5 ranging from 1,000 to 3,000 mg/1. However, s i n c e the p r e d i c t e d 0 C f o r f a i l u r e was 0.42 day at 22°C f o r a 1,000 mg/1 BOD5 l e a c h a t e , a 9 C of 2 t o 4 days seems p o s s i b l e i n the f i e l d . On the o t h e r hand, the e f f e c t s of winter temperature on BOD5 removal and sludge s e t t l e a b i l i t y , as w e l l as many other unknown f a c t o r s on the o v e r a l l b i o l o g i c a l treatment e f f i c i e n c y must be con s i d e r e d . I t was, t h e r e f o r e , f e l t t h a t a s o l i d s d e t e n t i o n time of 5 days or more would be the more r e a l i s t i c approach f o r a f u l l - s c a l e treatment system, d e s p i t e the f a c t t h a t an economic a n a l y s i s favored a s h o r t e r 9 C. i v Leaching t e s t s f o r the b i o l o g i c a l sludge from a e r o b i c treatment i n d i c a t e d t h a t no severe d e s o r p t i o n problems would a r i s e from d i s p o s i n g of the sludge i n t o a l a n d f i l l . Under the t e s t c o n d i t i o n s used, most of the metals a s s o c i a t e d with the sludge such as Zn, Fe, Mn, A l and Ca tended to remain with the s o l i d phase, with only l e s s than 5% being leached out by p e r c o l a t e d water. Approximately 14% of the Cr i n the sludge however, was leached out. I t was p o s s i b l e t o t r e a t t h i s l e achate t o n o n - t o x i c l e v e l s u s i n g the aerated lagoon process as long as the l e a c h a t e BOD^ was not h i g h e r than 1,000 mg/1. At 3,000 mg/1 BOD5, the a d d i t i o n of carbon p o l i s h i n g might be necessary to reduce the e f f l u e n t t o x i c i t y to below the non-t o x i c l e v e l . The most c o s t e f f e c t i v e f u l l - s c a l e l e a c h a t e treatment scheme may be determined by conducting p i l o t s t u d i e s i n a f u l l -s c a l e , s i n g l e - c e l l , s l u d g e - r e c y c l e a b l e system. V TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v i i LIST OF FIGURES i x ACKNOWLEDGEMENT - X CHAPTER 1 INTRODUCTION ' 1 2 RESEARCH OBJECTIVES 9 2-1 General 9 2-2 Treatment Systems Review 11 2-3 Treatment System S e l e c t i o n 16 2- 4 Research O b j e c t i v e s 17 3 EXPERIMENTAL PROCEDURES 19 3- 1 Leachate Source and C h a r a c t e r i s t i c s 19 3-2 A n a l y t i c a l Procedures 22 3-3 A e r o b i c D i g e s t i o n 23 3-4 A c t i v a t e d Carbon P o l i s h i n g 28 3-5 Sludge Leaching 30 3-6 Removal of A r o c l o r 1254 - A PCB 31 3- 7 T o x i c i t y Assessment 33 4 RESULTS AND DISCUSSION 35 4- 1 A e r o b i c D i g e s t i o n 35 4-2 A c t i v a t e d Carbon P o l i s h i n g 50 4-3 Sludge Desorption 54 4-4 Removal of A r o c l o r 1254 - A PCB 61 v i CHAPTER Page 4- 5 T o x i c i t y Assessment 63 5 COST ANALYSIS 6 8 5- 1 I n t r o d u c t i o n 6 8 5-2 Design C a l c u l a t i o n s and C o n s i d e r a t i o n s 69 5- 3 Cost A n a l y s i s 73 6 CONCLUSIONS AND RECOMMENDATIONS 77 6- 1 Co n c l u s i o n s 77 6-2 Recommendations 81 REFERENCES 85 APPENDICES Appendix I Design Equations f o r B i o l o g i c a l 89 System Appendix II P r e d i c t i o n of O p e r a t i o n a l S o l i d s 91 Detention Time and MLVSS Conc e n t r a t i o n s Appendix I I I An E v a l u a t i o n on the Role of 93 Chemical P r e c i p i t a t i o n i n Metal Removal d u r i n g A e r o b i c D i g e s t i o n Process Appendix IV Determination of K i n e t i c Parameters 96 v i i LIST OF TABLES TABLE Page I RANGE OF CHEMICAL COMPOSITION OF SANITARY LANDFILL LEACHATE 2 II LEACHATE STRENGTH VERSUS AGE OF SITE 3 I I I REFUSE MATERIALS BY KIND, COMPOSITION AND SOURCES 7 IV LEACHATE TREATMENT DESIGN CRITERIA 10 V STRENGTH OF LEACHATE AT DIFFERENT SAMPLING POINTS 19 VI CHARACTERISTICS OF LEACHATES COLLECTED IN THIS STUDY 21 VII OPERATIONAL CHARACTERISTICS AND RESULTS OF AEROBIC DIGESTION STUDIES 38 V I I I CHARACTERISTICS OF LEACHATE FEED, SETTLED EFFLUENTS AND MIXED LIQUORS FROM AEROBIC DIGESTION STUDIES 42 IX SUMMARY OF METAL REMOVAL DURING AEROBIC DIGESTION 4 4 X SUMMARY OF KINETIC PARAMETERS DETERMINED IN THIS AND OTHER COMPARABLE STUDIES 4 8 XI ACTIVATED CARBON TEST I RESULTS 51 XII OPERATIONAL CHARACTERISTICS FOR SLUDGE LEACHING TESTS 55 XIII ANALYTICAL RESULTS FOR SLUDGE LEACHING TEST I 56 XIV ANALYTICAL RESULTS FOR SLUDGE LEACHING TEST II' 57 XV MASS BALANCE FOR SLUDGE LEACHING TESTS 60 XVI BEAKER TEST RESULTS FOR PCB REMOVAL 6 2 XVII TOXICITY BIOASSAY TEST RESULTS 63 XVIII SAMPLE CHARACTERISTICS FOR TOXICITY TESTS 64 XIX SUMMARY OF TOXICITY DATA AND PARALLEL LEACHATE QUALITIES FROM DIFFERENT RICHMOND LANDFILL LEACHATE STUDIES 66 v i i i TABLE , Page XX SUMMARY OF AERATED LAGOON DESIGN CALCULATIONS 71 XXI COST ESTIMATIONS FOR AERATED LAGOON PROCESS 7 5 i x LIST OF FIGURES FIGURE Page 1 RICHMOND LANDFILL LOCATION MAP 6 2 SCHEMATIC OF A LABORATORY AEROBIC DIGESTER 2 4 3 MIXED LIQUOR SOLIDS STABILIZATION CHART 36 4 COD REMOVAL EFFICIENCY VS. DETENTION TIME 39 5 BOD 5 REMOVAL EFFICIENCY VS. DETENTION TIME 39 6 COD REMOVAL EFFICIENCY VS. ORGANIC LOADING RATE 40 7 PREDICTION OF MINIMUM SOLIDS DETENTION TIME. SETTLED EFFLUENT CONCENTRATIONS VS. SLUDGE AGE. 49 8 ACTIVATED CARBON POLISHING CURVES FOR TEST II 52 A - l DETERMINATION OF Y AND b BASED ON BOD5 DATA 97 A-2 DETERMINATION OF K AND K s BASED ON BOD5 DATA 97 A-3 DETERMINATION OF Y AND b BASED ON COD DATA 100 ACKNOWLEDGEMENT The author wishes t o express h i s g r a t i t u d e t o Dr. R.D. Cameron f o r h i s guidance, p a t i e n c e and understanding d u r i n g t h i s study. He a l s o wishes t o thank Dr. D.S. M a v i n i c , Mr. Jim Atwater and Mrs. E.C. McDonald f o r t h e i r k i n d a s s i s t a n c e on v a r i o u s aspects of the r e s e a r c h . T h i s r e s e a r c h was supported with funds provided by Environment Canada, S o l i d Waste Management Branch. CHAPTER 1 INTRODUCTION S a n i t a r y l a n d f i l l has been, and s t i l l i s , one of .the most economical and widely accepted methods f o r s o l i d waste d i s p o s a l . A s e r i o u s problem can a r i s e however, p a r t i c u l a r l y i n h i g h p r e c i p i t a t i o n r e g i o n s , when l e a c h a t e i s produced which can p o l l u t e s u r f a c e and sub-surface waters. Leachate i s produced when s u r f a c e or groundwater p e r c o l a t e s through the l a y e r s of r e f u s e and e x t r a c t s contaminants from the f i l l m a t e r i a l . Under the i n i t i a l l y a e r o b i c c o n d i t i o n s , b i o l o -g i c a l a c t i v i t y r e s u l t s i n p r o d u c t i o n of C0 2 and some v o l a t i l e a c i d s . T h i s lowers the pH of the moving l i q u i d and consequently i n c r e a s e s i t s e x t r a c t i o n c a p a b i l i t i e s . As time goes on, c o n d i -t i o n s g r a d u a l l y become an a e r o b i c , w i t h i n c r e a s i n g CH4 and s u l f i d e g e n e r a t i o n i n a d d i t i o n to C0 2 and v o l a t i l e o r g a n i c a c i d s . Consequently, the contaminants c a r r i e d by le a c h a t e may i n c l u d e a v a r i e t y of c o n s t i t u e n t s o r i g i n a l l y present as p a r t of the f i l l m a t e r i a l , as w e l l as products of chemical r e a c t i o n s and m i c r o b i a l decomposition. Leachate s t r e n g t h can be h i g h l y v a r i a b l e as shown i n Table I. The f a c t o r s which c o n t r i b u t e t o t h i s v a r i a b i l i t y i n c l u d e the r e f u s e c h a r a c t e r i s t i c s , i n f i l t r a t i o n r a t e s , and c l i m a t e , as w e l l as sample h a n d l i n g and a n a l y t i c a l methods. Another very important f a c t o r i s the age of the l a n d f i l l . Table II i l l u s t r a t e s how l a n d f i l l age, and thus the degree of s t a b i l i z a t i o n , a f f e c t s 1 TABLE I RANGE OF CHEMICAL COMPOSITION OF SANITARY LANDFILL LEACHATE C o n s t i t u e n t Range of A n a l y s i s Chemical Oxygen Demand, mg/1 40 -- 89,520 5-Day B i o c h e m i c a l Oxygen Demand, mg/1 81 -- 33,360 T o t a l Organic Carbon, mg/1 256 -- 28,000 PH 3.7 -- 8.5 T o t a l S o l i d s , mg/1 0 -- 59,200 T o t a l D i s s o l v e d S o l i d s , mg/1 584 -- 44,900 S p e c i f i c Conductance, rurtho/cm 2,800 -- 16,800 T o t a l A l k a l i n i t y , mg/1 as CaC03 0 -- 20,850 T o t a l Hardness, mg/1 as CaC03 0 -- 22,800 T o t a l Suspended S o l i d s , mg/1 10 -- 700 T o t a l Phosphorus, mg/1 as P 0 -- 130 Orthophosphorus, mg/1 as P 6.5 -- 85 Ammonia N i t r o g e n , mg/1 as N 0 -- 1,106 N i t r a t e + N i t r i t e , mg/1 0.2 -- 10.29 Calcium, mg/1 50 -- 7,200 C h l o r i d e , mg/1 4.7 -- 2,467 Sodium, mg/1 0 -- 7,700 Potassium, mg/1 28 -- 3,770 S u l f a t e , mg/1 1 -- 1,558 Manganese, mg/1 0.09 -- 125 Magnesium, mg/1 17 -- 15,600 Iro n , mg/1 0 -- 2,820 Z i n c , mg/1 0 -- 370 Copper, mg/1 0 -- 9.9 Cadmium, mg/1 ^0.03 -- 17 Lead, mg/1 <0.10 -- 2 TABLE II LEACHATE STRENGTH VERSUS AGE OF SITE Source Average S i t e Age (years) C h a r a c t e r i s t i c Hardness BOD 5 C l NH3-N as CaC0 3 Phenols SO4 pH (mg/1) (mg/1)(mg/1) (mg/1) (ppb) (mg/1) F e r g u s - E l o r a * St. Agatha (leachate pond i n f l u e n t ) B r a n r f o r d * ( w e l l s 66 & 67) Waterloo*(well 504) Uncontaminated Groundwater (St. Agatha Well 8) F i n a l E f f l u e n t (Waterloo PCP) Domestic Sewage T y p i c a l Data 1 13000 1000 180 3400 — 500 — 4 225 900 600 1400 200 10 7.3 9 110 300 175 900 30 10 7.2 30 2 96 10 772 4 - 7.5 - 10 3 0 120 6 - 8.0 - 20 248 - 316 - 190 -200 250 25 300 _ 200 7.5 * L a n d f i l l l o c a t i o n s 4 l e a c h a t e composition. Since l a n d f i l l l e a c h a t e i s o f t e n contaminated w i t h high c o n c e n t r a t i o n s of e x o t i c o r g a n i c s , heavy metals and many other p o t e n t i a l l y t o x i c substances, i t may s e r i o u s l y impair the q u a l i t y of the r e c e i v i n g water i f allowed to d i s c h a r g e to surrounding environments without proper h a n d l i n g . The degree of p o l l u t i o n w i l l depend on the q u a l i t y and q u a n t i t y of l e a c h a t e produced and the d i l u t i o n a f f o r d e d by the r e c e i v i n g water. The h e a l t h and environmental e f f e c t s of l e a c h a t e s have been w e l l documented i n the l i t e r a t u r e / 3,4,5) Q n e Q ^ t ^ e m e a n s t o c o n t r o l l a n d f i l l l e a c h a t e i s to minimize i t s r a t e of p r o d u c t i o n by c a r e f u l s i t e s e l e c t i o n and d e s i g n , p l u s proper c o n s t r u c t i o n and o p e r a t i o n . T h i s e n t a i l s d i v e r t i n g s u r f a c e water from the l a n d f i l l s i t e , s e a l i n g and s l o p i n g the s u r f a c e to minimize or e l i m i n a t e p r e c i p i -t a t i o n i n f i l t r a t i o n and l i n i n g t o prevent c o n t a c t of groundwater wit h r e f u s e , as w e l l as to f a c i l i t a t e l e a c h a t e c o l l e c t i o n . T h i s method of c o n t r o l i s very e f f e c t i v e i n a r i d or s e m i - a r i d c l i m a t e s where p r e c i p i t a t i o n i s minimal. However, i n the Lower Mainland of B r i t i s h Columbia, p r e c i p i t a t i o n of 30 to 40 inches per year, combined wi t h poor cover m a t e r i a l s , has c r e a t e d c o n d i t i o n s where l e a c h a t e i s produced i n s u b s t a n t i a l q u a n t i t y . In the Lower Mainland of B r i t i s h Columbia, v i r t u a l l y a l l a c t i v e l a n d f i l l s i t e s are c u r r e n t l y d i s c h a r g i n g l e a c h a t e to s u r f a c e streams. In some cases, the volume d i s c h a r g e d and the d i l u t i o n a v a i l a b l e i s such t h a t no major problems are caused w h i l e others are e a s i l y .connected to sewers f o r subsequent 5 treatment. In 1977 however, a r e p o r t expressed concern over l e a c h a t e d i s c h a r g e from a l a n d f i l l s i t e l o c a t e d on the bank of the F r a s e r R i v e r . T h i s l a n d f i l l s i t e , l o c a t e d on a peat bog adjacent to the R i v e r i n Richmond (Figure 1), covers a t o t a l area of 4.27 km 2 (1,055 acres) of which o n l y 1.25 km 2 (310 acres) has been under a c t i v e o p e r a t i o n . I t r e c e i v e s 140,000 to 180,000 m e t r i c tons (150,000 to 200,000 tons) per year of r e f u s e and has a f i l l depth of 1.8 to 4.3 m (6 to 14 f t ) . Table I I I o u t l i n e s the g e n e r a l c l a s s i f i c a t i o n of r e f u s e m a t e r i a l s and p o s s i b l e sources, and i n d i c a t e s s p e c i f i c c o n s t i t u e n t s as observed at the Richmond L a n d f i l l s i t e . B a s i c a l l y , the l a n d f i l l i n g o p e r a t i o n i n v o l v e s the c o n s t r u c -t i o n of a mattress base which i s o v e r l a i n by the commercial and r e s i d e n t i a l compactor-transported r e f u s e , w i t h c o v e r i n g m a t e r i a l s on top. The mattress base may c o n t a i n a broad range of m a t e r i a l s such as wood c h i p s , d e m o l i t i o n wastes, paper wastes, p l a s t i c s , i n d u s t r i a l s o l i d wastes and other m i s c e l l a n e o u s m a t e r i a l s . Intermediate cover i s dredged sand and/or wood c h i p s . F i n a l cover i s dredged sand and/or other s o i l m a t e r i a l s such as d i t c h c u t t i n g s and dredged s p o i l s . The l a n d f i l l has three main sources of water i n f l u x . Pre-c i p i t a t i o n of approximately 102 0 mm (40 inches) per annum and water f l o w i n g through the permeable d i k e s a t h i g h r i v e r stage, p l u s water from the sand dredging o p e r a t i o n . a l l combine to produce between 4.5 to 9.0 m i l l i o n l i t r e s (1 t o 2 m i l l i o n I gal) of l e a c h a t e per day. The peat under the l a n d f i l l has, through Sampling Location Frostr River D E L T A F I G U R E Is R ICHMOND L A N D F I L L L O C A T I O N M A P . TABLE I I I . REFUSE MATERIALS BY KIND, COMPOSITION AND SOURCES KIND COMPOSITION NOTED R.L. SOURCES Garbage Wastes from p r e p a r a t i o n , cook-i n g , and s e r v i n g of food; market wastes; wastes from h a n d l i n g , storage, and s a l e of produce X Households, r e s t a u r a n t s , i n s t i t u t i o n s , s t o r e s , markets Rubbish Combustible:paper, c a r t o n s , boxes, b a r r e l s , wood, e x c e l -s i o r , t r e e branches, yard trimmings, wood f u r n i t u r e , bedding, dunnage X Noncombustible:metals, t i n cans, metal f u r n i t u r e , d i r t , g l a s s , crockery, m i n e r a l s X Ashes Residue from f i r e s from cook-i n g , h e a t i n g , o n - s i t e i n c i n e r a t i o n X S t r e e t Refuse Sweepings, d i r t , l e a v e s , c a t c h b a s i n d i r t , contents of l i t t e r r e c e p t a c l e s , d i t c h c l e a n i n g s X S t r e e t s , s i d e -walks, a l l e y s vacant l o t s Dead Animals Cats, dogs, horses, cows * X V e h i c l e s Unwanted c a r s , t r u c k s X I n d u s t r i a l Wastes Food proc. wastes, c i n d e r s , lumber scraps, metal s c r a p s , shavings X F a c t o r i e s D e m o l i t i o n Wastes Lumber, p i p e s , b r i c k , masonry, e t c . X S i t e s f o r new bl d g s . , e t c . Construe. Wastes Scrap lumber, p i p e , e t c . X New c o n s t r u c -t i o n , e t c . S p e c i a l Wastes E x p l o s i v e s , p a t h o l o g i c a l wastes, r a d i o a c t i v e wastes ** X Homes, h o t e l s , h o s p i t a l s , e t c . Sewage Treatment S o l i d s from s c r e e n i n g , e t c . ; sludge * ** X Treatment p l a n t s , s e p t i c tanks Former S.P.C.A. Dump ** Except E x p l o s i v e s and R a d i o a c t i v e M a t e r i a l s *** Handled i n past R.L. Richmond L a n d f i l l S i t e c o n s o l i d a t i o n under the l o a d of the r e f u s e , formed a r e l a t i v e l y impervious b a r r i e r t o l e a c h a t e flow. Most l e a c h a t e i s t h e r e f o r i n t e r c e p t e d by a s u r f a c e d i t c h system which d i s c h a r g e s i n t o the F r a s e r R i v e r e s t u a r y . The study of t h i s l a n d f i l l ^ i n d i c a t e d t h a t , while t h i s l e a c h a t e d i s c h a r g e was u n d e s i r a b l e , treatment c o s t s c o u l d be high. I t was t h e r e f o r e decided t h a t an experimental program should be conducted to determine the lowest c o s t treatment method f o r t h i s l a n d f i l l l e a c h a t e . The i n f o r m a t i o n o b t a i n e d would a l s o be of s i g n i f i c a n t v a l u e to o t h e r l a n d f i l l o p e r a t i o n s i n the area and p r o v i d e more r e a l i s t i c c o s t f i g u r e s than those determined i n the l a n d f i l l study. 9 CHAPTER 2 RESEARCH OBJECTIVES 2-1 General In order to f i n d the most economical way of treating Lower Mainland municipal l a n d f i l l leachates over a long time period, a review of relevant l i t e r a t u r e was f i r s t conducted. The search for e f f e c t i v e treatment techniques for l a n d f i l l leachate has been the topic of i n t e r e s t of many investigations in recent years. The techniques include b i o l o g i c a l treatment, physical-chemical treatment and leachate recycle. While many have been found to provide e f f e c t i v e removal for some of the pollutants i n leachate, none of these methods alone can remove a l l objectionable pollutants. Also, each method has i t s own l i m i t a t i o n s and associated problems so that a combination of methods might be necessary to achieve the required treatment goals. Therefore, i n reviewing the l i t e r a t u r e the s u i t a b i l i t y of the various treatment methods, both alone and i n combination, had to be kept i n mind. Before the treatment systems were assessed, however, i t was necessary to define a s p e c i f i c e ffluent q u a l i t y i n order to determine design c r i t e r i a for a f u l l - s c a l e treatment system. It was decided to adopt the B r i t i s h Columbia Po l l u t i o n Control Board (P.C.B.) 'AA' l e v e l guidelines for s p e c i f i c discharges (7) as an acceptable e f f l u e n t q u a l i t y . These ef f l u e n t guidelines are shown i n Table IV. This Table also provides the suggested influent design c r i t e r i a based on the sample data co l l e c t e d 10 TABLE IV LEACHATE TREATMENT DESIGN CRITERIA (8) Parameter I n f l u e n t B.C. E f f l u e n t % Reduction Design Standards (7) Required COD mg/1 1500 BOD 5 mg/1* 750 T o t a l Residue mg/1 4000 N o n - f i l t r . , R e s i d u e mg/1 200 Spec. Conduct. juS/cm 7000 pH 6-7.5 A l k a l i n i t y mg/1 as CaC0 3 1700 Hardness mg/1 as CaC0 3 1500 Inorganic Carbon mg/1 400 Organic Carbon mg/1 400 NH3-N mg/1 N 45 CI mg/1- 2000 S0 4 (Dissolved) mg/1 200 B (Dissolved) 5 Cr (Total) mg/1 0.1 Fe (Dissolved) mg/1 50 Pb ( T o t a l ) mg/1 0.1 Mn (Dissolved) mg/1 5.0 Ni (Dissolved) mg/1 0.1 Zn (Total) mg/1 1.25 PCB jug/1 20 96-hr TLm %V/V 20 100 100 6.5-8.5 Not abnormally high 50 5.0 0.1 0.3 0.05 0.05 0.3 0.5 Non t o x i c 87 50 75 0 0 99, 50 99 0 60 80 * Estimate using BOD5/COD = 0.5 and T0C/B0D5 = 0.4. \ 11 (6) d u r i n g the l a n d f i l l study. 2-2 Treatment Systems Review (a) B i o l o g i c a l Treatment Among a l l the a e r o b i c b i o l o g i c a l systems i n c l u d i n g c o n v e n t i o n a l a c t i v a t e d sludge and i t s m o d i f i c a t i o n s , only the aerated lagoon has met with success and has been able to achieve e f f e c t i v e BOD removal i n l e a c h a t e treatment. A f u l l s c a l e lagoon i n England was e f f e c t i v e i n r e d u c i n g BOD of a low s t r e n g t h l e a c h a t e (BOD 5 = 185 mg/1) by about 94%. Laboratory s t u d i e s by Cook and Foree, Boyle and Ham, Chian and DeWalle, ^ 1 2 ^  (13) and U l o t h and Mavinic have r e p o r t e d COD removal of g r e a t e r than 90% a t d e t e n t i o n times ranging from 5 to 20 days f o r high and medium s t r e n g t h l e a c h a t e s of 6,000 to 48,000 mg/1 COD. Boyle and Ham^ 1 1' a l s o showed t h a t l e a c h a t e of 10,000 mg/1 COD c o u l d be added to an e x i s t i n g extended a e r a t i o n a c t i v a t e d sludge system t r e a t i n g domestic wastewater, up to a l e v e l of 5% by volume, without s e r i o u s l y a f f e c t i n g e f f l u e n t q u a l i t y . At g r e a t e r than 5%, l e a c h a t e a d d i t i o n s r e s u l t e d i n poor s e t t l e a b i l i t y and high oxygen uptake r a t e s . (13) Only one study has mentioned the f a t e of heavy metals i n an aerated lagoon. T h i s study showed e f f e c t i v e r e d u c t i o n of A l , Cd, Cr and N i to l e s s than the r e q u i r e d e f f l u e n t standards at 20 t o 30 day d e t e n t i o n times. Detention times of 45 and 60 days were r e q u i r e d t o meet the Zn and Fe standards r e s p e c t i v e l y , how-ever, and a c c e p t a b l e l e v e l s of As, Pb and Mn c o u l d not be met 12 even at a 60 day d e t e n t i o n time f o r t h i s high s t r e n g t h l e a c h a t e . Heavy metals posed no s i g n i f i c a n t o p e r a t i o n a l problems but some b i o l o g i c a l i n h i b i t i o n was i n d i c a t e d by the determined k i n e t i c (14) . parameters. Another study i n v e s t i g a t e d the n u t r i e n t requirements of the aerated lagoon process and found an optimum r a t i o of 100:3:1 (BOD 5:N:P), i n s t e a d of the c o n v e n t i o n a l r a t i o of 100:5:1. Anaerobic treatment of l a n d f i l l l e a c h a t e from v a r i o u s s t u d i e s has r e s u l t e d i n COD removals ranging from 92 to 99% at 7 t o 27 day d e t e n t i o n times as quoted by Chian and D e W a l l e . ^ 5 ^ Boyle and Ham^ ''"' showed t h a t a drop from the mean o p e r a t i o n a l temperature of 23°C t o l e s s than 20°C l e d t o e i t h e r a s u b s t a n t i a l decrease i n performance or a t o t a l f a i l u r e d u r i n g anaerobic (16) lea c h a t e treatment. Poorman and Cameron ob t a i n e d 80 t o 96% BOD5 removals at d e t e n t i o n times ranging from 5 t o 20 days and i n f l u e n t B0D5's ranging from 11,000 t o 16,000 mg/1. They found no adverse e f f e c t on the anaerobic d i g e s t i o n process from the presence o f high metal c o n c e n t r a t i o n s . While the lowest e f f l u e n t BOD5 of 188 mg/1 exceeded the accep t a b l e standards, e f f e c t i v e metal removal was achieved i n t h i s l a s t study. The metals exceeding B.C. e f f l u e n t standards were Fe, Mn, Zn and Pb. Combined a e r o b i c / a n a e r o b i c treatment has been found t o r e q u i r e 1 t o 7 days a e r a t i o n , f o l l o w i n g anaerobic d i g e s t i o n to achieve r e s i d u a l COD removals of 17 to 4 0 % . ^ ^ Leachate treatment u s i n g anaerobic d i g e s t i o n f o l l o w e d by a e r o b i c p o l i s h i n g t h e r e f o r e , does not appear p r a c t i c a l . 13 (b) Chemical Treatment Chemical treatment of l e a c h a t e i n c l u d e s p r e c i p i t a t i o n , c o a g u l a t i o n and o x i d a t i o n . Treatment e f f i c i e n c i e s from many (15) chemical treatment s t u d i e s are summarized i n Chian and DeWalle. P r e c i p i t a n t s and coagulants such as lime, alum, f e r r i c c h l o r i d e , polymers and sodium s u l f i d e have g e n e r a l l y been found to p r o v i d e good removals of suspended s o l i d s , c o l o r and Fe. However, the removal of COD, BOD and TDS was i n s i g n i f i c a n t , and chemical dosage requirements and sludge p r o d u c t i o n r a t e s were . . . (10,17,18) hxgh. ' ' Oxidants i n c l u d i n g C I 2 , O C 1 - , ozone and KMnO^ have a l s o been used t o t r e a t l e a c h a t e s . The r e p o r t e d r e s u l t s again showed t h a t h i g h dosages and long d e t e n t i o n times were r e q u i r e d to achieve e f f e c t i v e c o l o r removal, 20 t o 50% COD r e m o v a l ( 1 ° , 1 5 , 1 8 , 1 9 ) and (18) 91 t o 1 0 0 % Fe removal. Using lime and ozone, other metal (19) removal e f f i c i e n c i e s r e p o r t e d as the best v a l u e s were 96 to 1 0 0 % f o r Cu, Zn and Mn. (c) P h y s i c a l Treatment P h y s i c a l treatment processes i n c l u d e a c t i v a t e d carbon a d s o r p t i o n , peat treatment, r e v e r s e osmosis and i o n exchange. A c t i v a t e d carbon treatment of l e a c h a t e has been found t o provide COD removals of 34 t o 85% a t dosages ranging from 10,000 t o 160 ,000 mg/1 i n batch and column systems. Ho e t a l . ^ ^ showed t h a t at l e a s t 4,000 mg/1 of g r a n u l a r a c t i v a t e d carbon was necessary t o achieve 55% COD removal a t 20 min d e t e n t i o n time. They a l s o i n d i c a t e d t h a t up t o 70% i r o n removal c o u l d be achieved 14 i n the carbon a d s o r p t i o n p r o c e s s . Peat treatment of a low s t r e n g t h (650 mg/1 COD) leachate has been r e p o r t e d by Cameron and C o r b e t t . ^ 2 < ^ They were e s p e c i a l l y i n t e r e s t e d i n the metal removal and found t h a t approximately 159 Kg of dry peat per 1,000 L of l e a c h a t e would be r e q u i r e d to meet the B.C. e f f l u e n t g u i d e l i n e s . Mn was found t o be the l i m i t i n g parameter. Some d e s o r p t i o n of p o l l u t a n t s d i d occur when the expended peat was s u b j e c t e d to the p e r c o l a t i o n of tap water. Reverse osmosis was found to be the most e f f e c t i v e p h y s i c a l -chemical method i n l e a c h a t e COD removal, with the e f f i c i e n c y ranging from 56 to 89% u s i n g c o n v e n t i o n a l c e l l u l o s e a c etate m e m b r a n e s . T h e removal e f f i c i e n c y was g r e a t l y improved by u s i n g p o l y e t h y l e n i m i n , NS-100 membrane and by i n c r e a s i n g the pH from 5.5 to 8.0. The removal of t o t a l d i s s o l v e d s o l i d s was as high as 99%. However, f o u l i n g of membranes was a problem and b i o l o g i c a l pretreatment of l e a c h a t e was c o n s i d e r e d t o be necessary. No r e p o r t s have been found d e s c r i b i n g raw l e a c h a t e treatment u s i n g an i o n exchange process, (d) Combined Treatment As observed by many r e s e a r c h e r s , no one s i n g l e system has been found to achieve s a t i s f a c t o r y removal of a l l l e a c h a t e contaminants. Combined treatment i s t h e r e f o r e necessary to p r o v i d e e f f e c t i v e l e a c h a t e treatment. Cook and F o r e e ^ ^ found t h a t a c t i v a t e d carbon, f o l l o w i n g a e r o b i c treatment of leachate p r o v i d e d a t o t a l COD removal of over 99%. The removal of c o l o r and suspended s o l i d s was a l s o very e f f e c t i v e . Studies by 15 Pohland i n d i c a t e d t h a t a l l measured i o n i c i m p u r i t i e s i n the e f f l u e n t from .aerobic l e a c h a t e treatment were e f f e c t i v e l y removed by mixed i o n exchange r e s i n s , g i v i n g a s p e c i f i c conductance r e d u c t i o n o f g r e a t e r than 99.5%. R e s u l t s from these s t u d i e s u s i n g a c t i v a t e d carbon as the p o l i s h i n g system showed 90% COD removal at a 4,000 mg/1 dosage, but both TDS and s p e c i f i c conduc-tance i n c r e a s e d as carbon dosage i n c r e a s e d due t o l e a c h i n g of d i s s o l v e d s o l i d s from the carbon. Pohland a l s o suggested t h a t a c t i v a t e d carbon a d s o r p t i o n f o l l o w e d by mixed r e s i n i o n exchange would be most e f f e c t i v e i n removing r e s i d u a l o r g a n i c s and i n o r g a -n i c s i n the e f f l u e n t s from a e r o b i c and anaerobic b i o l o g i c a l p r o-cesses t r e a t i n g l e a c h a t e . Data from reverse-osmosis p o l i s h i n g of b i o l o g i c a l l e a c h a t e e f f l u e n t s i n d i c a t e d COD removal e f f i c i e n c i e s of 95 and 98%, u s i n g c e l l u l o s e a c e t a t e and Du Pont B-9 membranes r e s p e c t i v e l y . ^ 5 ^ The authors p r e f e r r e d combined treatment u s i n g anaerobic d i g e s t i o n or an aerated lagoon f o l l o w e d by e i t h e r r e v e r s e osmosis or a c t i -v ated carbon, with the p o s s i b l e a d d i t i o n of i o n exchange, (e) Leachate Recycle R e c y c l i n g of leac h a t e back through the l a n d f i l l i s thought t o pro v i d e a c o n t r o l l e d , o n - s i t e , i n t e r n a l anaerobic treatment of the r e c y c l e d l e a c h a t e , as w e l l as the r e f u s e c o n s t i -tuents w i t h i n the f i l l . I t a c c e l e r a t e s the b i o l o g i c a l s t a b i l i -z a t i o n of the r e f u s e o r g a n i c s and g r e a t l y reduces the p o l l u t a n t s t r e n g t h i n leac h a t e t o such l e v e l s t h a t i t c o u l d be dis c h a r g e d or r e l e a s e d f o r a d d i t i o n a l treatment, w i t h i n a r e l a t i v e l y s h o r t 16 p e r i o d o f ' t i m e . Through simulated l a n d f i l l s t u d i e s , Pohland (22) and Cameron showed t h a t r e c y c l e d l e a c h a t e c o u l d reach, i n a reasonable l e n g t h of time, a q u a l i t y s u i t a b l e f o r c o n s i d e r a t i o n f o r u l t i m a t e r e l e a s e i n t o r e c e i v i n g waters. However, t h i s would be dependent on r e s u l t s from l a r g e s c a l e l a n d f i l l o p e r a t i o n s being the same as those from experiments. B i o l o g i c a l uptake, chemical p r e c i p i t a t i o n and a d s o r p t i o n on the r e f u s e are the mechanisms thought to be e f f e c t i v e i n r e d u c i n g the c o n c e n t r a t i o n s of metals a s s o c i a t e d with the l e a c h a t e . I t i s not known whether or not adsorbed or c h e m i c a l l y p r e c i p i t a t e d metals w i t h i n the f i l l w i l l e v e n t u a l l y be r e l e a s e d once r e c y c l e stops. s A major problem with l e a c h a t e r e c y c l e i s the h y d r a u l i c aspect. In high r a i n f a l l a r e a s , t h i s technique c o u l d probably o n l y be p r a c t i s e d d u r i n g the dry season.. In the r a i n y season, the volume of l e a c h a t e to be handled would become unmanageable i n very s h o r t p e r i o d of time. 2-3 Treatment System S e l e c t i o n For the r e l a t i v e l y low s t r e n g t h l e a c h a t e (Table IV) to be used i n t h i s study, i t was concluded t h a t the most s u i t a b l e approach would be a two or three stage treatment system. That i s , l e a c h a t e would be f i r s t t r e a t e d i n an aerated lagoon f o l l o w e d by a c t i v a t e d carbon a d s o r p t i o n and then, i f necessary, f u r t h e r p o l i s h e d u s i n g r e v e r s e osmosis or a mixed i o n exchange pro c e s s . Anaerobic d i g e s t i o n was p r e c l u d e d because of the a s s o c i a t e d o p e r a t i o n a l d i f f i c u l t i e s , low l e a c h a t e s t r e n g t h , and high 17 c a p i t a l and o p e r a t i n g c o s t s . Chemical treatment was not s e r i o u s l y c o n s i d e r e d f o r p o l i s h i n g because of the p o s s i b l e high dosage requirements, h i g h sludge p r o d u c t i o n and i n a b i l i t y to remove a broad range of p o l l u t a n t s . Leachate r e c y c l e was not co n s i d e r e d due to the i n h e r e n t h y d r a u l i c problems and the f u t u r e plans f o r the s i t e . 2-4 Research O b j e c t i v e s Although i t has been shown t h a t a e r o b i c s t a b i l i z a t i o n of lea c h a t e i s t e c h n i c a l l y and ec o n o m i c a l l y f e a s i b l e f o r oxygen demanding m a t e r i a l s , there are some qu e s t i o n s which remain unanswered. These q u e s t i o n s r e l a t e t o the f a t e of heavy metals and s y n t h e t i c complex o r g a n i c s such as p o l y c h l o r i n a t e d b i p h e n y l s (PCB's) d u r i n g a e r o b i c treatment, necessary p o l i s h i n g techniques and sludge d i s p o s a l . The purpose of t h i s study was to t r y to pro v i d e some answers to these q u e s t i o n s based on l a b o r a t o r y s c a l e experiments. While a l l p r e v i o u s s e r i e s of leac h a t e treatment s t u d i e s conducted at the U n i v e r s i t y of B r i t i s h Columbia, i n c l u d i n g a e r o b i c b i o s t a b i l i -z a t i o n ^ 3 '^5) a n a e r o b i c d i g e s t i o n , ^ ^ and p h y s i c a l - c h e m i c a l (19) treatment, had obtained t h e i r "high s t r e n g t h " l e a c h a t e s from l y s i m e t e r s , i t was f e l t t h a t u s i n g a leac h a t e from an e x i s t i n g m u n i c i p a l l a n d f i l l would p r o v i d e more meaningful r e s u l t s f o r ope r a t o r s o f such e x i s t i n g l a n d f i l l s . The intended o b j e c t i v e s were t h e r e f o r e e s t a b l i s h e d as f o l l o w s : 18 1. To determine the t r e a t a b i l i t y of l e a c h a t e from an e x i s t i n g l a n d f i l l u s i n g an a e r o b i c d i g e s t i o n p r o c e s s . 2. To c h a r a c t e r i z e the s e t t l e d b i o l o g i c a l e f f l u e n t and to assess i t s environmental impact through b i o a s s a y t o x i c i t y t e s t s . 3. To study the t r e a t a b i l i t y of s y n t h e t i c complex o r g a n i c s such as PCB i n the a e r o b i c b i o l o g i c a l system. 4. To f i n d an e f f e c t i v e p o l i s h i n g method f o r r e d u c i n g the r e s i d u a l p o l l u t a n t c o n c e n t r a t i o n s i n the b i o l o g i c a l e f f l u e n t t o a c c e p t a b l e l e v e l s . 5. To c a r r y out small s c a l e sludge l e a c h i n g t e s t s to o b t a i n some i n d i c a t i o n of the f a t e of r e s i d u a l s such as heavy metals, once they were concentrated i n t o the s e t t l e d sludge s o l i d s and r e t u r n e d t o the l a n d f i l l f o r d i s p o s a l . 6. To determine the most c o s t e f f e c t i v e s o l i d s d e t e n t i o n time and leachate treatment system. CHAPTER 3 EXPERIMENTAL PROCEDURES 3-1 Leachate Source and C h a r a c t e r i s t i c s As mentioned p r e v i o u s l y , the l e a c h a t e used f o r t h i s study was c o l l e c t e d from the Richmond L a n d f i l l , one of the e x i s t i n g m u n i c i p a l l a n d f i l l s d i s c h a r g i n g l e a c h a t e i n t o the F r a s e r River e s t u a r y . To s e l e c t the a p p r o p r i a t e sampling s i t e , a p r e l i m i n a r y i n v e s t i g a t i o n t r i p was taken whereby s i x l e a c h a t e samples from v a r i o u s l o c a t i o n s were c o l l e c t e d . Table V shows the v a r i a b i l i t y of the s t r e n g t h , as i n d i c a t e d by the COD v a l u e , of these l e a c h a t e s . TABLE V STRENGTH OF LEACHATE AT DIFFERENT SAMPLING POINTS Sampling P o i n t Approximate L o c a t i o n * COD(mg/1) PH 1 South end c e n t r a l , d i t c h 135 6.6 2 C e n t r a l n o r t h , d i t c h 305 6.7 3 North e a s t , d i t c h 805 6.8 4 North e a s t , s p r i n g 1530 6.7 5 North west, d i t c h 1710 6.4 6 North west, s p r i n g 1820 6.1 L o c a t i o n s r e f e r to the 1.25 km a c t i v e f i l l area around the No. 8 Road D i t c h ( 6 ) . I t was then decided t h a t the l e a c h a t e sample would be taken from sampling p o i n t No. 6, the l a r g e s t s p r i n g l e a d i n g to the west 19 20 h a l f of the n o r t h e r n d i v e r s i o n d i t c h , because i t s high s t r e n g t h would provide a reasonable s a f e t y f a c t o r f o r the design of a f u l l s c a l e treatment system. I t was a l s o f e l t t h a t , i f a p r o p e r l y designed l e a c h a t e c o l l e c t i o n system were to be used, the d i l u t i o n e f f e c t of i n f l o w i n g s u r f a c e and r i v e r water would be e l i m i n a t e d , so t h a t the c o l l e c t e d l e a c h a t e s t r e n g t h would approach t h a t of sample No. 6. A l e a c h a t e s p r i n g was chosen because the l e a c h a t e i n the d i t c h e s was s u b j e c t t o o x i d a t i o n and d i l u t i o n . Leachate was c o l l e c t e d twice d u r i n g the study. Leachate I was c o l l e c t e d i n J u l y 1977 and was used p r i m a r i l y f o r a e r o b i c and p o l i s h i n g treatment s t u d i e s . The volume c o l l e c t e d was 400 l i t r e s at a s p r i n g flow r a t e of approximately 40 L/rain. Lea-chate I I , c o l l e c t e d i n January 1978 at the same spot, was used only to generate s e t t l e d e f f l u e n t s f o r b i o a s s a y t o x i c i t y s t u d i e s and some of the sludge f o r l e a c h i n g t e s t s . The volume c o l l e c t e d was 200 l i t r e s a t a flow r a t e of about 60 L/min. Once c o l l e c t e d , o the l e a c h a t e was r e t u r n e d to the l a b o r a t o r y and s t o r e d at 4 C to minimize b i o l o g i c a l a c t i v i t y and chemical changes. The c h a r a c t e r i s t i c s of the l e a c h a t e s are shown i n Table VI. P e r i o d i c a n a l y s i s of the l e a c h a t e i n d i c a t e d t h a t as long as the c o n t a i n e r s were kept f u l l of l e a c h a t e with l i t t l e space l e f t f o r a i r , the COD change due to b i o l o g i c a l and chemical o x i d a t i o n was l e s s than 2% over the five-month storage p e r i o d . On the other hand, when a c o n t a i n e r was only h a l f f i l l e d and was open occa-s i o n a l l y the corresponding COD l o s s c o u l d be as h i g h as 20% even i f i t was kept at l e s s than 4°C. 21 TABLE VI CHARACTERISTICS OF LEACHATES COLLECTED IN THIS STUDY* C h a r a t e r i s t i c s Leachate I Leachate I I COD 1,860 4,720 BOD 5 1,140 2,980 T o t a l Carbon (TC) 930 1,830 T o t a l Organic Carbon (TOC) 810 1,600 T o t a l S o l i d s (TS) 3 ,190 6 ,490 T o t a l V o l a t i l e S o l i d s (TVS) 1,470 2,930 T o t a l D i s s o l v e d S o l i d s (TDS) 3,070 6 ,470 pH 6.2 6.3 A c i d i t y as CaC03 (pH 8.3) 540 790 A l k a l i n i t y as CaC03 (pH 3.7) 1,350 3,050 T o t a l K j e l d a h l N i t r o g e n (TKN) 8.78 46.0 NH3-N as N 0.3 37.5 T o t a l - P as P 4 .67 3.1 S0 4 250 83 CI 125 390 S u l f i d e 0.02 30 B 5.89 7. 43 Ca 535 1,065 Na 128 358 K 51 137 Mg 39 84 Fe 22 . 4 1. 62 Mn 4.30 7.76 Zn 1.32 0.55 A l 0 .36 1.26 Cr 0.025 0.085 Cu 0 .050 0.010 Ni 0 .002 0.012 Pb 0.051 0.023 Cd 0 .002 0.001 Se 0.018 0.013 As 0.006 NA * A n a l y s i s c a r r i e d out w i t h i n 10 days of c o l l e c t i o n . ** A l l u n i t s i n mg/1 except pH. NA = Not analyzed. 22 3-2 A n a l y t i c a l Procedures A l l analyses were performed i n accordance w i t h the proce-(23) dures d e s c r i b e d ^ i n "Standard Methods" u n l e s s otherwise s t i p u l a t e d . For metal a n a l y s i s , a J a r r e l l - A s h MV500 atomic a b s o r p t i o n spectrophotometer was used. D i g e s t i o n of the sample was necessary t o ensure t h a t a l l metals were i n s o l u t i o n , so t h a t t o t a l c o n c e n t r a t i o n s were measured. Since i t was necessary to concentrate the sample ten times f o r the d e t e c t i o n of c e r t a i n heavy metals, a second d i g e s t i o n procedure was used i n order t o achieve proper d i g e s t i o n and c o n c e n t r a t i o n . The d i g e s t i o n procedure o u t l i n e d i n "Standard Methods" was m o d i f i e d based on (24) past a n a l y t i c a l experience with l e a c h a t e samples. The d i g e s t i o n procedure used was as f o l l o w s : 1. For the "as i s " p o r t i o n , 10 ml of 1:1 co n c e n t r a t e d HC1-HNO3 was added t o 100 ml of sample and b o i l e d down t o a p p r o x i -mately 75 ml. A f t e r c o o l i n g , the sample was f i l t e r e d i n t o a 10 0-ml v o l u m e t r i c f l a s k u s i n g No. 4 Whatman paper and made up to volume with d e i o n i z e d d i s t i l l e d water. 2. For the " c o n c e n t r a t i o n " p o r t i o n , 5 ml of concentrated HNO3 and b o i l i n g beads were added t o 500 ml of sample. The volume was b o i l e d down t o approximately 40 ml. One ml of conce n t r a t e d HC1 was added, the sample covered and d i g e s t e d f o r another 5 min. A f t e r c o o l i n g , the sample was f i l t e r e d i n t o a 50 ml v o l u m e t r i c f l a s k u s i n g No.4 Whatman f i l t e r paper and made up t o volume with d e i o n i z e d d i s t i l l e d water. 23 3. Reagent and f i l t e r blanks were a l s o run along with samples u s i n g d e i o n i z e d d i s t i l l e d water. A l l BOD5 t e s t s were performed u s i n g a domestic sewage seed, as without the seed, low BOD value s i n v a r i a b l y r e s u l t e d . 3-3 A e r o b i c D i g e s t i o n A bench-scale semi-batch, or f i l l and draw a e r o b i c system was s e l e c t e d t o e v a l u a t e the b i o l o g i c a l s t a b i l i z a t i o n of l a n d f i l l l e achate because i t was simple, easy t o operate, and a l s o most c l o s e l y simulated the s e l e c t e d f i e l d process of an aerated lagoon. T h i s system c o n s i s t e d of three 10-L r e a c t o r s (or d i g e s t e r s ) , made from l a r g e g l a s s b o t t l e s . A l l r e a c t o r s were f i t t e d with porous g l a s s , coarse-bubble a i r d i f f u s e r s . A i r was pro v i d e d f o r each r e a c t o r from the o i l - f r e e l a b o r a t o r y compressed a i r system (Figure 2 ) . To ensure complete mixing and uniform d i s t r i b u t i o n of food and microorganisms, a Sargent-Welch cone-drive s t i r r e r was a l s o p r o v i d e d f o r each r e a c t o r . T h i s mechanical mixing a l s o served to reduce the foaming problem caused by the a e r a t i o n p r o c e s s . Mixing speeds were s e t approximately equal i n a l l r e a c t o r s and a i r flow r a t e s were a d j u s t e d t o be j u s t high enough such t h a t a e r o b i c c o n d i t i o n s c o u l d be maintained d u r i n g the h i g h oxygen demand p e r i o d r i g h t a f t e r f e e d i n g . T h i s whole treatment system (25) had been used s u c c e s s f u l l y by U l o t h i n pr e v i o u s work. In order t o c o n t a i n any foam which might be produced dur i n g the study, o n l y 5.0 L of the t o t a l c a p a c i t y was used as the 24 E lect r i c Motor Dr iven ^ S t i r re r Volumetric Graduat ion Porous Glass A i r Di f fu se r P l a s t i c T u b i n g Oi l - Free Air Rubber Stopper Adjustable Screw Clamp To Other D igesters F I G U R E 2= S C H E M A T I C OF A L A B O R A T O R Y AEROBIC DIGESTER. ft 25 a c t u a l o p e r a t i n g volume. Nonetheless, foaming was never found to be a problem f o r t h i s low-strength l e a c h a t e d u r i n g the e n t i r e o p e r a t i o n . I t was decided t o use the b i o l o g i c a l s o l i d s d e t e n t i o n time, © c , as the b a s i c c o n t r o l parameter (Appendix I ) . Based on the 0 C v a l u e s used and k i n e t i c parameters found i n p r e v i o u s s t u d i e s , (10,25,26) p r e d i c t e d o p e r a t i o n a l 0 C s u i t a b l e f o r t h i s s p e c i f i c l e a c h a t e f e l l i n the range of 3 to 10 days (Appendix I I ) . To produce an a c c l i m a t i z e d m i c r o b i a l p o p u l a t i o n f o r the leachate d i g e s t i o n p r o c e s s , i t was f e l t t h a t raw sewage ( r a t h e r than the c o n v e n t i o n a l a c t i v a t e d sludge mixed l i q u o r ) seeding might p r o v i c e a g r e a t e r d i v e r s i t y of microorganisms. Conse-quently, the d i g e s t e r s were s t a r t e d w i t h 3 L of raw sewage, obtained from a l o c a l sewage treatment p l a n t , and 0.5 L of l e a -chate. More l e a c h a t e was added d u r i n g the next few days u n t i l a f i n a l 5.0 L volume was reached. At 2 4 hr i n t e r v a l s , the water l o s t by e v a p o r a t i o n eas r e p l a c e d with d i s t i l l e d water. The s i d e s of the d i g e s t e r s and s t i r r e r s were scraped to r e t u r n a l l adhering s o l i d s t o the mixed l i q u o r and then the contents were completely mixed. A f t e r the a i r and s t i r r e r s i n a l l d i g e s t e r s were shut o f f , the b i o l o g i c a l f l o e was allowed to s e t t l e f o r 1 h r . The r e q u i r e d volume of supernatant was then withdrawn from each d i g e s t e r a c c o r d i n g t o the i n d i v i d u a l s o l i d s d e t e n t i o n time. Volumes of l e a c h a t e feed equal to the volume removed were then added to each d i g e s t e r . Leachate was s t o r e d i n 5-gal p l a s t i c c o n t a i n e r s . Each day 26 the t o t a l r e q u i r e d volume of feed was t r a n s f e r r e d t o a sm a l l e r f e e d - c o n t a i n e r and brought t o room temperature before f e e d i n g , so that temperature shock t o microorganisms c o u l d be prevented. N u t r i e n t s o l u t i o n was the only i n g r e d i e n t added t o the feed. The BOD5:N:P r a t i o of 100:0.8:0.4 i n the leac h a t e was low i n N and P, compared t o the commonly recommended r a t i o of 100:5:1. A d d i t i o n a l n u t r i e n t s were t h e r e f o r e added t o the le a c h a t e feed to ensure the proper growth of microorganisms. For the leac h a t e with a B O D 5 of 1040 mg/1, the estimated requirements f o r n u t r i e n t a d d i t i o n were 43 mg/1 N and 5.6 mg/1 P. The r e q u i r e d n u t r i e n t s o l u t i o n was made from N H 4 C I and (NI^^HPO^ which, when added i n a p p r o p r i a t e p r o p o r t i o n s would supply 45 mg/1 N and 6 mg/1 P t o the le a c h a t e . C h l o r i d e l e v e l s were, of course, a l s o i n c r e a s e d . No pH adjustment of leac h a t e feed was found necessary because the pH of a l l mixed l i q u o r s was i n the range of 7.4 to 7.7 a f t e r 4 days of a c c l i m a t i z a t i o n , and rose t o 8.4 i n 10 days. For the r e s t of the study, the pH of the mixed l i q u o r never went beyond the range of 8.4 to 8.6 r i g h t before f e e d i n g , and of 8.2 to 8.4 r i g h t a f t e r f e e d i n g , r e g a r d l e s s of the value s of 0 C. No temperature c o n t r o l was p r o v i d e d , so t h a t the temperature ranged from 21° t o 24°C d u r i n g the e n t i r e o p e r a t i o n of a e r o b i c d i g e s t i o n . A p r e l i m i n a r y t e s t u s i n g s o l i d s d e t e n t i o n times of 5, 10, and 15 days showed t h a t a Gc of 5 days was the most r e a l i s t i c approach f o r treatment and design purposes. I t was then decided to use ec of 3, 5 and 7 days, f o r d i g e s t e r s A, B and C resp e c -t i v e l y , f o r the f i r s t stage treatment e f f i c i e n c y study. A f t e r 27 completing t h i s f i r s t stage, the s o l i d s d e t e n t i o n time was broadened t o cover 2 and 10 days d u r i n g the second stage of the study. The second phase t h e r e f o r e , i n c o r p o r a t e d d i g e s t e r D ( 0 C = 7 days), d i g e s t e r E ( 6 C = 2 da y s ) , and d i g e s t e r F (9^ = 10 days). T h i s second stage o p e r a t i o n was conducted t o provide s u f f i c i e n t p o i n t s f o r the de t e r m i n a t i o n of k i n e t i c parameters and to enable an economic a n a l y s i s t o be made f o r the d i f f e r e n t d e t e n t i o n times. Some of these d e t e n t i o n times, while l e s s than the optimum from a b i o l o g i c a l treatment viewpoint, c o u l d produce an e f f l u e n t meeting e x i s t i n g d i s charge standards. T h e r e f o r e , they were i n c l u d e d t o p r o v i d e data t o enable a r a t i o n a l d e c i s i o n t o be made on the s i z e of a treatment f a c i l i t y . As i n d i c a t e d b e f o r e , d u r i n g the a c c l i m a t i z a t i o n and s o l i d s b u i l d - u p p e r i o d , only the c l e a r supernatants were withdrawn from each d i g e s t e r . To determine the mixed l i q u o r v o l a t i l e sus-pended s o l i d (MLVSS) l e v e l at which s o l i d wasting c o u l d be s t a r t e d , c a l c u l a t i o n s were performed based on assumed COD removal e f f i c i e n c y and growth k i n e t i c parameters (Appendix I I ) . The p r e d i c t i o n showed t h a t f o r a 6 C range of 3 t o 10 days, the steady s t a t e MLVSS c o n c e n t r a t i o n s would be between approximately 50 0 and 700 mg/1. However, i t was decided t h a t s o l i d s wasting should not begin u n t i l MLVSS c o n c e n t r a t i o n s reached 900-1,000 mg/1 f o r d i g e s t e r s A, B and C, i n case the p r e d i c t e d MLVSS values were under-estimated. For d i g e s t e r s D, E and F, the beginning of s o l i d wasting would depend upon the a c t u a l steady s t a t e s o l i d s c o n c e n t r a t i o n s found d u r i n g the f i r s t stage o p e r a t i o n . When performing sludge wasting, the contents of the d i g e s t e r s were 28 v i g o r o u s l y mixed and the r e q u i r e d volume of mixed l i q u o r withdrawn from each d i g e s t e r , u s i n g a l a r g e - t i p - o p e n i n g household b a s t e r . During the a c c l i m a t i z a t i o n and s o l i d s b u i l d - u p p e r i o d , pH, d i s s o l v e d oxygen (DO) and oxygen uptake r a t e i n each d i g e s t e r were checked f r e q u e n t l y t o ensure the r i g h t c o n d i t i o n s f o r b i o l o g i c a l growth. The COD and TSS of s e t t l e d e f f l u e n t s and MLVSS concen-t r a t i o n s were measured every 2 t o 3 days. During the treatment e f f i c i e n c y s t u d i e s , the growth c o n d i t i o n s were w e l l under c o n t r o l so t h a t pH and DO were checked on l y o c c a s i o n a l l y . Oxygen uptake r a t e , MLVSS, p l u s COD and TSS of 1-hr s e t t l e d e f f l u e n t however, were measured every other day f o r each d i g e s t e r . The B O D 5 of the mixed l i q u o r and s e t t l e d e f f l u e n t s was determined every 7 days or so. These parameters were used t o determine when steady s t a t e c o n d i t i o n s were achieved. Once steady s t a t e was reached, s e t t l e d e f f l u e n t s from each d i g e s t e r were c o l l e c t e d d a i l y . The e f f l u e n t s from each d i g e s t e r were s e p a r a t e l y composited f o r e f f l u e n t c h a r a c t e r i z a t i o n as w e l l as f o r e f f l u e n t p o l i s h i n g s t u d i e s and t o x i c i t y t e s t s . C e r t a i n amounts of mixed l i q u o r s and sludges were a l s o kept under 4°C f o r sludge c h a r a c t e r i z a t i o n and l e a c h i n g s t u d i e s . 3-4 A c t i v a t e d Carbon P o l i s h i n g S e t t l e d e f f l u e n t s from a e r o b i c b i o l o g i c a l treatment were p o l i s h e d u s i n g a c t i v a t e d carbon columns. The carbon s e l e c t e d was 12 t o 40 mesh Nuchar WV-G g r a n u l a r carbon manufactured by Westvaco. I t i s a h i g h - d e n s i t y carbon with a l a r g e s u r f a c e area. The pore s t r u c t u r e and the wide range of mesh s i z e enable i t t o e f f i c i e n t l y adsorb a g r e a t v a r i e t y of both h i g h and low molecular weight i m p u r i t i e s from wastewater. The columns were made from 100 ml b u r e t t e s and had a c r o s s - s e c t i o n a l area of 1.77 cm2. Glass beads and g l a s s wool were p l a c e d a t the bottom of the column to act as a f i l t e r and t o prevent the p l u g g i n g of the o u t l e t v a l v e with carbon p a r t i c l e s . To prepare the column, a proper amount of carbon was measured and b o i l e d i n d i s t i l l e d water f o r 15 min to degas. With the column p a r t i a l l y f i l l e d w i t h d i s t i l l e d water, carbon s l u r r i e s were then spooned i n u n t i l the r e q u i r e d depth was reached. O c c a s i o n a l tapping on the column was necessary to ensure a t i g h t and uniform packing and thus minimize the p o s s i b i l i t y of flow channeling. Two carbon a d s o r p t i o n t e s t s were run i n t h i s study. In the f i r s t t e s t a column of 30 cm (1 f t ) and a le a c h a t e l o a d i n g r a t e of 2 L/sec-m 2 (3 U.S.gpm/ft 2) were employed. In the second t e s t a 122 cm (4 f t ) column and the same h y d r a u l i c l o a d i n g r a t e were used. Carbon-leachate c o n t a c t time based on the empty bed volume was 2.5 min f o r T e s t I and 10 min f o r - T e s t I I . The feed used i n these t e s t s was t r e a t e d e f f l u e n t from d i g e s t e r C f o r Test I and from d i g e s t e r F f o r T e s t I I . Both t e s t s were run at the 22 C room temperature. A f t e r f i l l i n g , s e v e r a l hundred mis of d i s t i l l e d water was run through the columns i n order t o a d j u s t the flow r a t e as w e l l as t o wash out any p o s s i b l e contaminants. The s e t t l e d e f f l u e n t 30 was then allowed t o f i l l and pass through the column a t the same r a t e . The f i r s t volume of e f f l u e n t equal t o the empty carbon bed volume was d i s c a r d e d , and the subsequent p o l i s h e d e f f l u e n t was c o l l e c t e d i n p o r t i o n s of 5 0 0 ml f o r a n a l y s i s . 3-5 Sludge Leaching The e f f e c t s of sludge d i s p o s a l i n t o a l a n d f i l l were assessed by s u b j e c t i n g dewatered sludge t o smal l s c a l e l e a c h i n g t e s t s . Two l e a c h i n g or d e s o r p t i o n t e s t s were performed. Test I em-ployed sludge from d i g e s t e r C ( 9 C = 7 days) t r e a t i n g Leachate I. Test II made use of sludge from two d i g e s t e r s t r e a t i n g Leachate I I . These d i g e s t e r s were operated i n p a r a l l e l a t 0 C of 10 days and are r e f e r r e d to as d i g e s t e r G. Buchner funnels with What-man No.541 f i l t e r paper ( 2 0 - 2 5 ja) f i t t e d on the bottom were used as l e a c h i n g supports. These f i l t e r s , c h a r a c t e r i z e d as "hardened a s h l e s s " and " f a s t " i n f i l t e r speed, had been found t o produce n e g l i g i b l e contamination of samples at the metal c o n c e n t r a t i o n s of concern. As a p r e c a u t i o n a r y measure, when s t a r t i n g the t e s t , Buchner funnels and f i l t e r s were pre-washed wi t h a c i d and r i n s e d w i t h d e i o n i z e d d i s t i l l e d water. The known q u a n t i t i e s of sludge were then i n t r o d u c e d and allowed t o d r a i n by g r a v i t y u n t i l such drainage stopped. T h i s l i q u i d was c o l l e c t e d and s t o r e d f o r a n a l y s i s . Tap water was then a p p l i e d t o the sludge at r a t e s commensurate w i t h sludge p e r m e a b i l i t y u s i n g p i p e t t e s or droppers. The amount of sludge i n each f u n n e l was s p e c i f i c a l l y p r o p o r t i o n -ed such t h a t the r e s u l t a n t t h i c k n e s s , a f t e r d r a i n i n g , p rovided 31 a reasonably f a s t l e a c h i n g r a t e and enabled the c o l l e c t i o n of the r e q u i r e d volumes of l e a c h a t e w i t h i n a r e l a t i v e l y s h o r t p e r i o d of time. The tap water used was c o l l e c t e d from the tap a f t e r the water had been allowed to run f o r at l e a s t 15 min, to m i n i -mize metal contamination e s p e c i a l l y Cu and Fe. Tap water was used i n s t e a d of rainwater because i t d i d not r e q u i r e storage. I t was a l s o f e l t t h a t tap water would have a more c o n s i s t e n t composition than r a i n w a t e r . Three 8-cm diameter and one 13-cm diameter Buchner funnels were used. The l e a c h i n g r a t e f o r Test I was 0.5 cm/hr or 6 ml/g sludge dry wt./hr and the r e s u l t a n t sludge t h i c k n e s s was 1.0 to 1.2 cm. For T e s t I I , the l e a c h i n g r a t e was 1.2 cm/hr or 18 ml/g sludge dry wt./hr and the r e s u l t a n t sludge t h i c k n e s s was 0.5 to 0.6 cm. Leachate p o r t i o n s of 400 ml and 200 ml were c o l l e c t -ed i n T e s t I and 800-ml p o r t i o n s were c o l l e c t e d i n T e s t II f o r a n a l y s i s . Samples i n T e s t I were analyzed u n f i l t e r e d , while samples i n T e s t II were analyzed both f i l t e r e d and u n f i l t e r e d . 3-6 Removal of A r o c l o r 12 5 4 - A PCB Solvent e x t r a c t i o n , i n c o n j u n c t i o n with g a s - l i q u i d chromato-graphy, was used t o study the t r e a t a b i l i t y of PCB i n the a e r o b i c d i g e s t i o n system. The e x t r a c t i o n procedure was the one used t o e x t r a c t organo-c h l o r i n a t e d p e s t i c i d e s and PCB's f o r a n a l y s i s , s i m i l a r to those (23) given i n "Standard Methods" and i n Reference No. 27. Hexane was the s o l v e n t used. The instrument used was a Hewlett-Packard 32 5750 GLC, equipped w i t h n i c k e l c e l l e l e c t r o n - c a p t u r e d e t e c t o r . The GLC column used was 3% OV-101 on 80/100 Chromosorb W. Before PCB removal e f f i c i e n c y c o u l d be determined, i t was important t o check whether or not the d i s s o l v e d r e s i d u a l o r g a n i c s i n the e f f l u e n t would cause i n t e r f e r e n c e with the proposed PCB s p i k i n g s . Both s e t t l e d e f f l u e n t s from b i o l o g i c a l treatment of Leachate I and Leachate I I were s u b j e c t e d t o the t e s t . Two hundred ml of the f i l t e r e d f i r s t e f f l u e n t (COD = 180 mg/1) was spiked w i t h 60 jag/1 A r o c l o r 1254 and e x t r a c t e d with a t o t a l volume of 50 ml hexane. T h i s e x t r a c t , when compared with the sample blank and PCB standard of the same c o n c e n t r a t i o n , showed no s i g n i f i c a n t i n t e r f e r e n c e from o r g a n i c r e s i d u a l s . S i m i l a r l y , 50 ml of the f i l t e r e d second e f f l u e n t (COD = 600 mg/1) was spi k e d with 120 jig/1 A r o c l o r 1254 and e x t r a c t e d with 50 ml hexane. Again, the o r g a n i c r e s i d u a l s presented l i t t l e i n t e r f e r e n c e . I t was t h e r e f o r e unnecessary t o p r e t r e a t the samples f o r o r g a n i c i n t e r f e r e n c e s u s i n g a column such as f l o r i s i l . The two d i g e s t e r s t r e a t i n g Leachate I I at the 0 C of 10 days ( d i g e s t e r G) were then s p i k e d with 50 and 250 yug/1 of the PCB, A r o c l o r 1254. A t h i r d d i g e s t e r was used as a c o n t r o l r e a c t o r where mixed l i q u o r was r e p l a c e d w i t h d i s t i l l e d water. T h i s c o n t r o l r e a c t o r was cleaned and s t e r i l i z e d w i t h NaOCl s o l u t i o n b e f o r e o p e r a t i o n , and was covered with a l a r g e p i e c e of f i l t e r paper a f t e r i t was spi k e d w i t h 250 jug/1 PCB. The purpose of the c o n t r o l r e a c t o r was to pro v i d e some i n s i g h t as t o whether or not f a c t o r s o t h e r than b i o l o g i c a l uptake, such as a d s o r p t i o n , would c o n t r i b u t e to the PCB removal. PCB stock s o l u t i o n s used f o r s p i k i n g were prepared i n a l c o h o l . For the 2 d i g e s t e r s , leachate feed was s p i k e d with PCB, while f o r the c o n t r o l r e a c t o r the PCB was added to the whole volume a t the beginning of the t e s t . Mechanical s t i r r i n g and a i r supply were p r o v i d e d f o r the c o n t r o l r e a c t o r i n the same manner as f o r the other d i g e s t e r s . U n f o r t u n a t e l y , a sample taken from the c o n t r o l r e a c t o r a f t e a r e t e n t i o n time of 18 hrs i n d i c a t e d t h a t 90% of the spiked PCB had been l o s t , presumably to the r e a c t o r w a l l and/or to the a i r . Thus, i t seemed very u n l i k e l y t h a t d e t e r m i n a t i o n of the t r e a t -a b i l i t y of PCB through t h i s bench s c a l e aerated system' would be p o s s i b l e . A f u r t h e r t e s t was attempted to account f o r the l o s s of PCB i n the c o n t r o l r e a c t o r . Two l a r g e beakers having about the same w a l l c o n t a c t area per u n i t l i q u i d volume as the c o n t r o l r e a c t o r were se t up. A e r a t i o n was p r o v i d e d f o r one beaker and not f o r the o t h e r . Both beakers were spi k e d with 250 jug/1 PCB a t time zero. P e r i o d i c a n a l y s i s of the remaining PCB l e v e l s was expected to t e l l i f the PCB l o s s i n the previous c o n t r o l r e a c t o r was due to the a e r a t i o n e f f e c t or w a l l a d s o r p t i o n . 3-7 T o x i c i t y Assessment T o x i c i t y assessment through b i o a s s a y t e s t s has become i n c r e a s i n g l y important because, u s i n g the n a t i v e s p e c i e s of the r e c e i v i n g water, i t p r o v i d e s a b e t t e r understanding of the impact of a wastewater on the r e c e i v i n g environment than the o f t e n a r b i t r a r y e f f l u e n t standards set by r e g u l a t o r y agencies. 34 In t h i s r e s e a r c h , t o x i c i t y t e s t s were run on the raw l e a c h a t e s and the t r e a t e d s e t t l e d e f f l u e n t s , t o determine the t o x i c i t y of raw l e a c h a t e s and to what extent t h i s t o x i c i t y was reduced by the a e r o b i c d i g e s t i o n treatment. Included i n these t e s t s were the standard 9 6 - h r LC50 b i o a s s a y and r e s i d u a l oxygen bi o a s s a y (ROB). The 9 6 - h r L C ^ Q was performed i n accordance with a standard ( 2 8 ) procedure u s i n g Salmo g a i r d n e r i (rainbow t r o u t ) . The ROB ( 2 9 procedure used was based on the work of V i g e r s and Maynard, a l s o u s i n g rainbow t r o u t . 35 CHAPTER 4 RESULTS AND DISCUSSION 4-1 A e r o b i c D i g e s t i o n With the proper growth c o n d i t i o n s p r o v i d e d , MLVSS concen-t r a t i o n s of approximately 1,000 mg/1 were reached i n a 30-day a c c l i m a t i z a t i o n period, f o r d i g e s t e r s A, B and C. Once sludge wasting was s t a r t e d , another 2 t o 3 weeks were needed t o reach s t e a d y - s t a t e c o n d i t i o n s , although d i g e s t e r s were kept under o p e r a t i o n f o r a much longer time i n order t o generate enough e f f l u e n t f o r other s t u d i e s . The s t a b l e o p e r a t i o n , which r e s u l t e d i n good sludge s e t t l e a b i l i t y and high q u a l i t y s e t t l e d e f f l u e n t (as r e f l e c t e d by COD and B O D 5 ) f o r d i g e s t e r s A, B and C, showed t h a t the p r e d i c t i o n of 9 C had pro v i d e d the r i g h t s e l e c t i o n of s o l i d s d e t e n t i o n times of 3, 5 and 7 days. The s t e a d y - s t a t e MLVSS c o n c e n t r a t i o n s ranged from 36 0 to 560 mg/1 which i s reasonably c l o s e to the p r e d i c t e d range of 500 t o 700 mg/1. F i g u r e 3 i s a composite graph showing the MLVSS v a r i a t i o n s f o r 6 d i g e s t e r s throughout the time of o p e r a t i o n . I t was observed t h a t on the average, MLVSS accounted f o r only 30% of MLSS. T h i s was thought t o be r e l a t e d to the low TVS/TS r a t i o of 0.46 i n the leachate f e e d , as w e l l as the formation of i n o r g a n i c p r e c i p i t a t e s accompanying the pH change du r i n g the b i o l o g i c a l treatment process. A simple t e s t of the e f f e c t of a pH i n c r e a s e on the leac h a t e t o t a l and v o l a t i l e suspended s o l i d s (TSS and VSS) was c a r r i e d out whereby pH 36 MOO IOOO Symbol Digester 0 c,days 4 0 0 o A x T • A B C D E F 3 5 7 2 7 10 Dashed L ines Indicate Steady - State M L V S S Levels A O A , B — D - C E F 3 0 0 2 0 0 ' _L _L J I I 8 10 12 14 16 18 20 22 24 26 28 Time from Star t ( d a y s ) FIGURE 3 s MIXED LIQUOR SOLIDS STABIL IZATION C H A R T . 37 was a d j u s t e d and the TSS and VSS measured before and a f t e r . The r e s u l t s showed a 205 mg/1 TSS i n c r e a s e to 330 mg/1 and a 40 mg/1 VSS i n c r e a s e to 120 mg/1 i n h a l f an hour as the pH was changed from 6.3 t o 8.4, the normal o p e r a t i o n a l pH of the d i g e s t e r s . The n a t u r a l pH i n c r e a s e d u r i n g treatment i s t h e r e -f o r e a s i g n i f i c a n t f a c t o r i n keeping the MLVSS/MLSS r a t i o low. The r e s u l t s and c h a r a c t e r i s t i c s of the e n t i r e a e r o b i c d i g e s t i o n o p e r a t i o n are summarized i n Table V I I . F i g u r e s 4 and 5 show the removal e f f i c i e n c y of COD and BOD 5 r e s p e c t i v e l y , as a f u n c t i o n of s o l i d s d e t e n t i o n time. COD removal i n c r e a s e d from 82.6 to as high as 90.1% when 9 C i n c r e a s e d from 2 to 10 days. The corresponding i n c r e a s e i n BOD5 removal e f f i c i e n c y was from 97.0 to as high as 99.3%. For 9 C g r e a t e r than 3 days, the BOD5 removals averaged 99.1% and the s e t t l e d e f f l u e n t BOD 5's were no g r e a t e r than 10 mg/1. T h i s i n d i c a t e s t h a t the raw le a c h a t e can be almost completely biodegraded by a e r o b i c b i o l o g i c a l treatment. F i g u r e 6 shows the COD removal e f f i c i e n c y as a f u n c t i o n of the o r g a n i c l o a d i n g . The COD removal e f f i c i e n c y decreased with i n c r e a s i n g food t o microorganism r a t i o (F/M). At F/M r a t i o s l e s s than 0.4 mg BOD5/mg MLVSS/day, the i n f l u e n t COD removals were g r e a t e r than 88.5%. As the F/M r a t i o i n c r e a s e d to above 0.6 mg BOD5/mg MLVSS/day the i n f l u e n t COD removal decreased r a p i d l y . T h i s g e n e r a l t r e n d of r a p i d decrease i n COD removal wi t h i n c r e a s i n g F/M r a t i o was the same as t h a t observed by Cook and F o r e e ^ " ' and U l o t h and M a v i n i c . 38 TABLE VII OPERATIONAL CHARACTERISTICS AND RESULTS OF AEROBIC DIGESTION STUDIES D i g e s t e r A B C D E F G 4 9 C, days 3 5 7 2 7 10 10 Feed COD, mg/1 1 1760 1760 1760 1580 1580 1580 4720 Feed BOD 5, mg/1 1 1040 1040 1040 940 940 940 2980 S e t t l e d E f f l u e n t COD, mg/12 215 200 175 275 170 170 600 S e t t l e d E f f l u e n t BOD 5, mg/1 2 9 10 7 28 8 8 18 MLVSS, mg/1 560 560 480 490 400 360 1150 S e t t l e d E f f l u e n t SS, mg/1 2 14 22 10 34 15 18 40 COD Removal, % 87.8 88.6 90.1 82.6 89.2 89.2 87.3 BOD 5 Removal, % 99.1 99.0 99.3 97 .0 99.1 99.1 99. 4 F/M, mg BOD5/mg MLVSS/day 3 0.61 0.37 0.31 0.93 0.33 0.26 0.26 COD and BOD^ va l u e s are lower than shown i n Table VI due to a r e d u c t i o n i n s t r e n g t h d u r i n g storage of Leachate I. 2 1-hr s e t t l i n g time. 3 C a l c u l a t e d based on BOD removal, 4 Leachate II (see Table V I ) . In the case of the h i g h - s t r e n g t h l e a c h a t e s (7,000 and 36,000 mg/1 BOD5 r e s p e c t i v e l y ) used by these i n v e s t i g a t o r s the best opera-t i o n a l F/M r a t i o was found t o be l e s s than 0.15 mg BOD5/mg MLVSS/day. The r e d u c t i o n i n optimum F/M r a t i o with i n c r e a s e d l e a c h a t e s t r e n g t h i s probably due t o i n c r e a s e d metal and o r g a n i c t o x i c i t y , b i o l o g i c a l c o m p e t i t i o n and i n c r e a s e d s o l u b l e BOD5 t r a n s f e r r a t e s . The s e t t l e d e f f l u e n t suspended s o l i d s i n t h i s study v a r i e d > o E ce Q o o 90 8 8 h 86 84 82 80 / I I 1 1 1 2 3 4 5 6 7 8 9 Solids Detention Time (days) e R L U 10 FIGURE 4= COD REMOVAL EFFICIENCY VS. DETENTION TIME 100 Z 99 o > o E 9) cc 98 Q O 97 96 / / / / o •-Q-0 R L I 2 4 6 8 Solids Detention Time (days) 10 FIGURE 5' B 0 D 5 REMOVAL EFFICIENCY VS. DETENTION TIME 40 FIGURE 6 ! COD REMOVAL EFFICIENCY VS.ORGANIC LOADING RATE. 41 i r r e g u l a r l y and ranged from•10 mg/1 at 6 C of 7 days t o 34 mg/1 at 0 C of 2 days. Thus, the 7-day d e t e n t i o n time p r o v i d e d the b e s t s e t t l e a b i l i t y . The 2-day d e t e n t i o n time r e s u l t e d i n r e l a t i v e l y poor s e t t l i n g , p o s s i b l y due t o i t s high o r g a n i c l o a d i n g r a t e . T h i s .might have l e d to the development of filamentous microorganisms and d i s p e r s e d f l o e . F i g u r e s 4, 5 and 6 a l s o show the corresponding data a t 9 C of 10 days f o r Leachate II (RL I I ) . In s p i t e of i t s s t r e n g t h being three times t h a t of Leachate I (RL I ) , RL II gave a BOD5 removal e f f i c i e n c y of 99.4%. T h i s was as good as the e f f i c i e n -c i e s f o r RL I at d e t e n t i o n times g r e a t e r than 7 days. However, the COD removal e f f i c i e n c y of 87.3% f o r RL I I was r e l a t i v e l y low i n comparison with those f o r RL I at 0 C's g r e a t e r than 5 days. No c o n c l u s i o n c o u l d be drawn from RL I I treatment r e g a r d i n g the r e l a t i o n s h i p between l e a c h a t e s t r e n g t h and optimum F/M r a t i o s i n c e there was only one p o i n t a v a i l a b l e . The raw l e a c h a t e used i n these s t u d i e s e x h i b i t e d a c o l o r of y e l l o w i s h grey f o r RL I and g r e e n i s h grey f o r RL I I , with a reasonably s t r o n g obnoxious odor. S e t t l e d e f f l u e n t s from a l l 6 d i g e s t e r s t r e a t i n g RL I were l i g h t brown i n c o l o r compared to the dark brown c o l o r f o r s e t t l e d e f f l u e n t s from RL II treatment. The s e t t l e d e f f l u e n t s from d i g e s t e r s A, B and C are f u r t h e r c h a r a c t e r i z e d i n Table V I I I . A l s o shown i n Table V I I I are the c h a r a c t e r i s t i c s of corresponding mixed l i q u o r s , the leachate (7) feed composition, and the P.C.B. standards. The d i s c r e p a n c y i n l e a c h a t e composition (RL I) between Table VI and Table V I I I 42 TABLE V I I I CHARACTERISTICS OF LEACHATE FEED, SETTLED EFFLUENTS AND MIXED LIQUORS FROM AEROBIC DIGESTION STUDIES Leachate S e t t l e d E f f l u e n t Mixed F e e d 2 (1 hr s e t t l i n g ) L i q u o r P.C.B. (7) D i g e s t e r A B C A B C Standard 9 C (days) 3 5 7 3 5 7 C h a r a c t e r i s t i c s 1 BOD5 1040 9 10 7 240 210 210 100 COD 1760 215 200 175 940 890 810 -TC 780 98 93 84 235 341 427 -TOC 630 9 9 9 30 130 246 TS 2980 1260 1310 1250 2670 2680 2640 -TSS 125 14 22 10 1540 1520 1480 100 pH 6.3 8.4 8.4 8.4 8.4 8.4 8.4 6.5-8 A l k a l i n i t y ( p H 4 . 5 ) 520 340 400 330 NA NA NA -(pH3.7) 730 360 430 360 NA NA NA -Acidity(pH8.3) 222 0 0 0 0 0 0 -TKN 9.34 5.63 5.03 3.41 57.5 55.8 56.6 -NH3-N 3.0 2.7 1.0 <0.3 ~2 .7 'vl.O ^0.3 -T o t a l - P 4.82 0.48 0.62 0.45 13.5 14.0 14.2 -CI 125 230 234 232 234 232 227 -SO4 278 292 274 256 298 274 251 50 B 6.05 6 .05 5.94 5.96 6.52 6.44 6.60 5.0 Ca 550 173 188 182 540 552 545 -Na 120 124 126 122 123 123 127 -K 44.0 44.2 43.8 44.2 48.7 48.0 48.7 -Mg 39.2 37.0 37 .0 36.4 36.6 35.3 36.6 -Fe 20.2 0.83 1.17 0.67 19.3 19.6 19.6 0.3 Mn 4.10 0.01 0.11 0.04 3.75 3.82 3.84 0.05 Zn 1.17 0.10 0.11 0.10 1.11 1.19 1.18 0.5 A l 0.33 0.06 0.08 0.07 0.37 0.36 0.31 2.0 Cr .017 .009 .007 .006 .018 .016 .016 0.1 Cu .030 .030 .031 .033 .042 .039 .050 0.2 Ni <.002 <.002 <.002 <.002 <.002 <.0 02 <. 002 0.3 Pb .045 <.003 <.003 <.003 .051 .045 .047 0.05 Cd .0015 <.0005 <.0005 <.0005 .0020 .0018 .0018 .005 As .027 NA .036 .038 NA .050 .044 0.05 Se .024 .011 .011 .011 .032 .021 .018 0.05 1 A l l v a l u e s are i n mg/1 except pH. 2 Sample (RL I) was analyzed about 2 months a f t e r c o l l e c t i o n b e f o r e n u t r i e n t s of 25 mg/1 of ( N H 4 ) 2 H P 0 4 and 150 mg/1 of N H 4 C I were added. NA = Not analyzed. 43 i s mainly due to b i o l o g i c a l o x i d a t i o n and chemical r e a c t i o n s d u r i n g s t o r a g e . A comparison of the s e t t l e d e f f l u e n t charac-t e r i s t i c s with the P.C.B. standards immediately shows t h a t the a e r o b i c treatment was so e f f e c t i v e i n removing most of the or g a n i c and i n o r g a n i c p o l l u t a n t s , i n c l u d i n g heavy metals, t h a t only SO^ and Fe s i g n i f i c a n t l y exceeded the standards. Boron exceeded the standard only m a r g i n a l l y . For the e f f l u e n t from d i g e s t e r B, Mn a l s o exceeded the P.C.B. standard, probably because d i g e s t e r B contained * h i g h e r suspended s o l i d s . The c o n c e n t r a t i o n s of BOD5 and suspended s o l i d s i n the s e t t l e d e f f l u e n t s are f a r below the l e v e l s which might be r e q u i r e d by the r e g u l a t o r y agency. Although most of the metal c o n c e n t r a t i o n s i n the leac h a t e feed were below the P.C.B. standards, the removal of metal contaminants was very e f f e c t i v e . Table IX summarizes the removal e f f i c i e n c i e s f o r v a r i o u s metal s p e c i e s . I t shows t h a t g r e a t e r than 90% of Fe, Mn, Zn and Pb, about 80% of A l , and not l e s s than 66% of Cd and Ca i n the le a c h a t e feed were removed with the s e t t l e d sludge s o l i d s . No f i g u r e s are r e p o r t e d f o r Ni and Cu because of the non-detectable c o n c e n t r a t i o n s of Ni and a contamination problem r e s u l t i n g from high Cu l e v e l s i n the l a b o r a t o r y water supply. As expected, e s s e n t i a l l y a l l Na and K passed r i g h t through the treatment system remaining almost completely i n the l i q u i d phase. In a b i o l o g i c a l system, metals may be removed by simple p r e c i p i t a t i o n , microorganism uptake and a d s o r p t i o n t o or TABLE IX SUMMARY OF METAL REMOVAL DURING AEROBIC DIGESTION* Digester A B C G c (days) 3 5 7 Percentage of Metal Removal: Mn 99. 8 97 .3 99.0 Fe 95.9 94.2 96.7 Pb >93.3 >93.3 >93.3 Zn 91.5 90.6 91.5 A l 81.8 75.8 78.8 Cd >66.7 >66.7 >66.7 Ca 69.1 66.4 67.5 Cr 47.1 58.8 64.7 Mg 5.1 5.1 7.1 Na ~ 0 ~ 0 /v 0 K rsj 0 A/0 A/0 Ni NP NP NP Cu NP NP NP Calculations based on the concentrations i n leachate feed and i n se t t l e d e f f l u e n t . NP = Not possible to calculate. 45 entrapment w i t h i n b i o l o g i c a l f l o e s . The metals d i s s o l v e d i n the l i q u i d f r a c t i o n of the sludge w i l l a l s o appear to be removed. The p r e v i o u s l y d i s c u s s e d 370% i n c r e a s e i n f i x e d suspended s o l i d s (FSS), r e s u l t i n g from a change of pH from 6.3 t o 8.5, i n d i c a t e s t h a t chemical p r e c i p i t a t i o n has played an important r o l e i n the o v e r a l l removal of c e r t a i n metals. Based on the s o l u b i l i t y products of v a r i o u s p o s s i b l e compounds, the p o s s i b i l i t y of p r e c i p i t a t e formation f o r Ca, Fe, Zn, Pb, Mn and Mg due to the above pH change was b r i e f l y e v a l u a t e d (Appendix I I I ) . Despite the f a c t t h a t the presence of v a r i o u s o r g a n i c s and suspended s o l i d s makes the l e a c h a t e a complex and u n p r e d i c t a b l e system, the rough c a l c u l a t i o n s i n Appendix I I I do p r o v i d e some u s e f u l i n f o r m a t i o n . F i r s t , i t i s very l i k e l y t h a t Ca was removed p r i m a r i l y as CaCO^ p r e c i p i t a t e which was p a r t i c a l l y aided i n s e t t l i n g by b i o l o g i c a l a d s o r p t i o n and entrapment. T h i s i s supported both by the s o l u b i l i t y product theory and by the evidence t h a t the amount of Ca removed with the sludge s o l i d s was c a l c u l a t e d to be n e a r l y c h e m i c a l l y e q u i v a l e n t to the amount of i n o r g a n i c carbon a s s o c i a t e d with the sludge s o l i d s ; t h a t i s , the 910 mg/1 of Ca as CaCO^ was n e a r l y equal to the 1,000 mg/1 of i n o r g a n i c carbon as CaCO^ A l s o , a s c a l e formation was observed i n s i d e the r e a c t o r s . T h i s s c a l e was r e a d i l y d i s s o l v e d by a c i d washing, which supports the p o s s i b i l i t y of i t s being a carbonate. Although i t i s always p o s s i b l e t h a t Ca might a l s o be removed by 46 forming p r e c i p i t a t e s with o t h e r anions or by b i o l o g i c a l uptake, i t i s hard t o imagine any o t h e r mechanisms which were s i g n i f i c a n t enough t o remove Ca to such an extent. I f the c a l c i u m removed with the sludge s o l i d s had been q u a n t i t a t i v e l y p r e c i p i t a t e d as CaC03, the i n c r e a s e of FSS due to n a t u r a l pH change d u r i n g d i g e s t i o n should have been at l e a s t 910 mg/1. The data f o r MLVSS and TSS i n Tables VII and V I I I show t h a t FSS i n c r e a s e d by about 1,000 mg/1, thus s u p p o r t i n g the theory of chemical p r e c i -p i t a t i o n . The s h o r t , simple pH adjustment t e s t p r e v i o u s l y mentioned showed an i n c r e a s e i n FSS of only 165 mg/1. I t i s t h e r e -f o r e apparent t h a t there i s a s i g n i f i c a n t time e f f e c t i n v o l v e d . Secondly, the removal of Zn and Pb was p o s s i b l y through the formation of carbonate and/or phosphate p r e c i p i t a t e s as w e l l as microorganism uptake and a d s o r p t i o n . T h i r d l y , Fe was probably removed mainly as FePC>4 and Fe(OH)3 p r e c i p i t a t e s , while Mn might have been removed mainly by e a r l y formation of MnCC>3 f o l l o w e d by spontaneous o x i d a t i o n t o Mn0 2, as w e l l as other mechanisms i n c l u d i n g b i o l o g i c a l uptake and a d s o r p t i o n . The formation of i n s o l u b l e , o r g a n o - m e t a l l i c compounds co u l d a l s o have been one of the p o s s i b l e mechanisms f o r metal removal. The i n f o r m a t i o n presented i n Table VII .was used t o determine the k i n e t i c parameters a s s o c i a t e d with a e r o b i c treatment of t h i s m u n i c i p a l l a n d f i l l l e a c h a t e . The equations and procedures i n v o l v -ed are o u t l i n e d i n Lawrence and Mc C a r t y ^ 3 0 ^ and M e t c a l f and Eddy, (31) Inc. Design equations are shown i n Appendix I. D e t a i l e d c a l c u l a t i o n s and graphs are shown i n Appendix IV. The k i n e t i c 47 parameters thus determined are summarized i n Table X, where value s from other l e a c h a t e treatment s t u d i e s as w e l l as those f o r domestic wastewater are a l s o given f o r comparison. Note t h a t the COD-based growth y i e l d c o e f f i c i e n t , Y, and microorganism decay c o e f f i c i e n t , b, obtained from t h i s study are extremely c l o s e to those from Cook and F o r e e , a l t h o u g h the lea c h a t e COD 1s d i f f e r by a f a c t o r of 10. The BOD5~based Y and b values from t h i s study are comparable t o those f o r domestic sewage. The growth parameters K and K s a l s o c l o s e l y agree with those f o r domestic waste, c o n s i d e r i n g the r e l a t i o n s h i p between BOD5 and COD p l u s the d i f f e r e n c e i n waste s t r e n g t h . T h i s means t h a t the microorganism p o p u l a t i o n a c c l i m a t i z e d i n t h i s study c o u l d u t i l i z e or s t a b i l i z e the l e a c h a t e as e f f i c i e n t l y as the c o n v e n t i o n a l a c t i v a t e d sludge process used i n t r e a t i n g domestic sewage. Two reasons were f e l t t o be r e s p o n s i b l e f o r these r e s u l t s . F i r s t , adequate n u t r i e n t s have been p r o v i d e d f o r b i o l o g i c a l growth . Second, the c o n c e n t r a t i o n s of heavy metals, e x o t i c o r g a n i c s or any oth e r p o t e n t i a l t o x i c substances i n t h i s l e a c h a t e were not high enough t o cause s i g n i f i c a n t b i o l o g i c a l i n h i b i t i o n d u r i n g the a e r o b i c treatment p r o c e s s . Based on the o p e r a t i o n a l and k i n e t i c c h a r a c t e r i s t i c s d e t e r -mined as w e l l as the equation g i v e n i n Appendix I, the t h e o r e t i -c a l s o l i d s d e t e n t i o n time f o r f a i l u r e was p r e d i c t e d t o be 0.42 day (Figure 7 ) . From a treatment e f f i c i e n c y p o i n t of view, the optimum s o l i d s d e t e n t i o n time was observed t o be about 7 days f o r Leachate I and 10 days f o r Leachate I I . TABLE X SUMMARY OF KINETIC PARAMETERS DETERMINED IN THIS AND OTHER COMPARABLE STUDIES Wastewater Type 1 Treatment Process Parameter B a s i s I n f l u e n t BODc or COD (mg/1) ( Y mg-VSS mg-BOD b K )( d a y 1 ) ( d a y 1 )(mg/1) Ref. NO. L.L. A.L. BOD 5 1,000 0.59 0.040 4.5 99 T h i s L.L. A.L. COD 1,700 0.42 0.056 NR NR Study L.L. A.L. COD 17,500 0.40 0.05 0.60 175 10 L.L. A.L. BOD 5 36,000 0.33 0.0025 0.75 21,375 13* L.L. A.S. COD 360 0.59 0.115 1.8 182 26 D.W. 1 A.S. BOD 5 NR 0.50 0.055 NR NR 31 D.W. 2 A.S. COD NR 0.67 0.07 5.6 22 31 1 L.L. = L a n d f i l l l e a c h a t e ; D.W. = Domestic waste 2 A.L. = Aerated lagi oon; A.S. = A c t i v a t e d sludge. * K i n e t i c data based on mixed l i q u o r BOD^, others used s e t t l e d e f f l u e n t v a l u e s . NR = Not r e p o r t e d . 49 8 0 0 r -7 0 0 c,min. K S 0 K s+S 0 - b S 0 = 990mg/ l Y = 0.59 b = 0.040day K = 4.5day K s= 9 9 m g / l - l 80 7 0 0c,min= 0-42 day E O o 6 0 0 5 0 0 = 4 0 0 UJ X3 - 3 0 0 a> 2 0 0 0 0 Ef f luen t C O D s and B 0 D 5 s are cor rec ted to the same influent s t r e n g t h using given removal e f f i c i e n c i e s (Table YJT.) Predicted 0, _ J I c.min. 0.42day J 4 6 8 10 Sol ids Detention Time (days) 60 -E 50 £ o m 40 | H — L U 30 ^ CO 20 - 10 12 FIGURE 7= PREDICTION OF MINIMUM SOLIDS DETENTION TIME. SETTLED EFFLUENT CONCENTRATIONS VERSUS SLUDGE A G E . 5 0 4-2 A c t i v a t e d Carbon P o l i s h i n g B i o l o g i c a l treatment was found to be e f f e c t i v e i n removal of most heavy metals as w e l l as o r g a n i c m a t e r i a l s i n the l e a c h a t e . Iron, sulphate and boron however, exceeded e f f l u e n t standards. I t was t h e r e f o r e f e l t t h a t some p r e l i m i n a r y t e s t i n g should be c a r r i e d out to assess the e f f e c t i v e n e s s of a c t i v a t e d carbon as a p o l i s h i n g step. The a n a l y t i c a l r e s u l t s f o r s e t t l e d e f f l u e n t p o l i s h i n g u s i n g a c t i v a t e d carbon are presented i n Table XI and F i g u r e 8. Boron was not i n c l u d e d i n the a n a l y s i s because i t s behavior toward a c t i v a t e d carbon was expected t o be s i m i l a r to SO^ and because i t exceeded the p o s s i b l e standard o n l y m a r g i n a l l y . Table XI pr o v i d e s data f o r Tes t I where a 30-cm (1 f t ) column was used. The poor r e s u l t s were due to the s h o r t d e t e n t i o n time. The treatment r e s u l t s f o r Tes t I I , where the column le n g t h was 122 cm (4 f t ) , were g r e a t l y improved and are p l o t t e d i n F i g u r e 8. These t e s t s showed t h a t a c t i v a t e d carbon was extremely e f f e c t i v e i n removing c o l o r and f a i r l y e f f e c t i v e i n removing r e s i d u a l o r g a n i c s and i r o n , p r o v i d e d t h a t a reasonably long c o n t a c t time was used. However, carbon a d s o r p t i o n was found t o remove l i t t l e s u l f a t e no matter how much co n t a c t time was allowed. For the h y d r a u l i c l o a d i n g r a t e of 2.0 L / s e c m 2 (3 U.S.gpm/ f t 2 ) and a con t a c t time of 10 min used i n Tes t I I , the s e t t l e d e f f l u e n t c o l o r was completely e l i m i n a t e d up t o a throughput volume of 6 L. Only 5 u n i t s remained a f t e r 10 L had passed through 51 TABLE XI ACTIVATED CARBON TEST I RESULTS T o t a l Throughput Volume (L) E f f l u e n t C o n c e n t r a t i o n % Remaining i n E f f l u e n t C o l o r (units) COD (mg/1) Fe (mg/1) s o 4 (mg/1) C o l o r COD Fe s o 4 Feed 400 160 1.40 247 NA NA NA NA 0.5 50 15 0.37 232 12.5 9.4 26 . 4 93 . 9 1.0 80 34 0.52 238 20.0 21.3 37.1 96.4 1.5 100 46 0.68 242 25.0 28.8 48.6 98.0 2.0 120 54 0.81 245 30 .0 33 . 8 57.9 99.2 2.5 125 59 0. 83 246 31.3 36.9 59.3 99.6 3.0 150 65 . 0.86 258 37.5 40 .6 61.4 >100 3.5 175 67 0.88 240 43.8 41.9 62.9 97 .2 4.0 175 69 0.88 250 43.8 43 .1 62.9 >100 4.5 200 71 0 .90 240 50.0 44.4 64.3 97 .2 5.0 200 75 0.90 244 50.0 46.9 64.3 98.8 5.5 225 80 0.93 246 56.3 50.0 66.4 99.6 6.0 225 84 0.95 245 56.3 52.5 67.9 99.2 * Column le n g t h = 1 f t ; c o n t a c t time = 2.5 min. NA = Not a p p l i c a b l e . the 1.5 cm diameter column. Under the same c o n d i t i o n s , the COD removal ranged from 99% a t 1 L throughput volume t o 91% at 10 L throughput. A l o g i c a l breakthrough p o i n t f o r Fe would be 0.3 mg/1, the P.C.B. standard f o r s p e c i f i c d i s c h a r g e s , which corresponds t o 30% of the i n f l u e n t Fe c o n c e n t r a t i o n . U n f o r t u -n a t e l y , the volume of s e t t l e d e f f l u e n t a v a i l a b l e f o r p o l i s h i n g was not enough t o al l o w the t e s t t o be c a r r i e d out t h a t f a r . With the combined treatment of a e r o b i c d i g e s t i o n f o l l o w e d Legend : c V 3 .71 20 CP c o E <u or c o ± 10 o a. c a> o a A Fe (C 0= l .00mg/l ) o C0D(C 0 = I65mg/I ) X Color(C0= 400units) Carbon Westvaco WV-G,12X40 Hydraulic Loading 2.0l itres/m 2 Contact Ti me : 10 mi n. Co lumn : <f> = I. 5cm 4 5 6 7 Throughput Volume (litres) 8 10 FIGURE 8 « ACT IVATED CARBON POLISHING CURVES FOR TEST 3t . U l 53 by carbon p o l i s h i n g , the o v e r a l l removal e f f i c i e n c i e s f o r COD and Fe i n the leac h a t e amounted t o g r e a t e r than 99.2 and 99.4% r e s p e c t i v e l y , u s i n g a c o n t a c t time of 10 min and a throughput volume of 10 L as p r e v i o u s l y mentioned. In f a c t , the combined treatment was s u c c e s s f u l enough t o have a l l parameters i n the f i n a l e f f l u e n t meet the P.C.B. standards, with the e x c e p t i o n of SO4 and B. To e f f e c t i v e l y remove these two p o l l u t a n t s , a process such as re v e r s e osmosis, i o n exchange or chemical p r e c i -p i t a t i o n might be r e q u i r e d . I t was f e l t however, t h a t adding a s i n g l e e x t r a s o p h i s t i c a t e d treatment system j u s t f o r SO4 and B was unreasonable from an economic or c o s t - e f f e c t i v e p o i n t of view. No f u r t h e r attempts were t h e r e f o r e , made t o add to t h i s treatment system. For p h y s i c a l - c h e m i c a l treatment of domestic and i n d u s t r i a l (32) wastewater, the EPA Technology T r a n s f e r Manual recommends a h y d r a u l i c l o a d i n g of 1.4 t o 6.8 L / s e c m 2 (2 t o 10 U.S.gpm/ft 2) and a c o n t a c t time o f 10 to 50 min. I t a l s o recommends t h a t 91 t o 182 Kg (200 to 400 lbs) of a c t i v a t e d carbon be used f o r t e r t i a r y treatment of each m i l l i o n U.S. g a l l o n s of wastewater. A rough c a l c u l a t i o n showed t h a t a combination of 10 min c o n t a c t time and 2.0 L / s e c m 2 (3 U.S.gpm/ft 2) l o a d i n g r a t e f o r 12x40, WV-G Westvaco g r a n u l a r carbon, while p r o v i d i n g good p o l i s h i n g e f f i c i e n c y , would r e q u i r e about 630 Kg of carbon per m i l l i o n U.S. g a l l o n s of l e a c h a t e . While i t i s l i k e l y t h a t other combi-n a t i o n s of these three o p e r a t i o n a l parameters c o u l d p rovide more e f f e c t i v e and economic treatment, no f u r t h e r attempts were made 54 to d e f i n e the optimum carbon p o l i s h i n g system. Although t h i s was l a r g e l y due to the l a c k of a e r o b i c a l l y t r e a t e d e f f l u e n t , i t was a l s o f e l t t h a t , i n the f i e l d , a e r o b i c treatment alone would pro-duce an e f f l u e n t q u a l i t y a c c e p t a b l e to the r e g u l a t o r y agency. I f carbon p o l i s h i n g were found t o be necessary i n the f i e l d , d e t e r m i n a t i o n of the optimum system should be based on t e s t s u s i n g the f i e l d e f f l u e n t . 4-3 Sludge Desorption In order to assess the p o t e n t i a l adverse e f f e c t s of d i s p o s i n g of sludge i n l a n d f i l l s , sludge d e s o r p t i o n t e s t s were c a r r i e d out. 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 of the sludge l e a c h i n g study are summarized i n Table X I I . Samples were analyzed f o r c o l o r , s o l i d s , COD, TOC and as many metals as p o s s i b l e i n c l u d i n g Ca, Fe, Mn, Zn, Cr, A l , Ni and Pb. The r e s u l t s of these analyses are presented i n T a b l e s XIII and XIV f o r T e s t s I and II r e s p e c t i v e l y . Note t h a t T e s t I was performed on sludge from d i g e s t e r C and T e s t II on sludge from d i g e s t e r G. As c o n t a c t time and temperature were f e l t to be important i n the d e s o r p t i o n p r o c e s s , they were b r i e f l y e v a l u a t e d . The time e l a p s e d between c o l l e c t i n g T e s t I sample 3 and sample 4 was 48 h r s , w h i l e no more than 8 hrs was allowed between other c o l l e c t i o n s . In the same t e s t sample 5 was o b t a i n e d a t a l e a c h -i n g temperature of 4°C, while a l l other l e a c h i n g was c a r r i e d out at the room temperature of 22°C. In T e s t I I , the l e a c h i n g temperature was 22°C and the time r e q u i r e d f o r each c o l l e c t i o n 55 TABLE XII OPERATIONAL CHARACTERISTICS FOR SLUDGE LEACHING TESTS C h a r a c t e r i s t i c s T e s t I T e s t I I T o t a l Wet Sludge Volume, ml 585 375 Sludge S o l i d s C o n c e n t r a t i o n , % 4. .5 5.0 T o t a l Sludge Dry Weight, g 26. .3 18. 8 Sludge T h i c k n e s s , cm 1.0-1. .2 0.5-0.6 Leaching Rate, cm/hr 0. .5 1.2 ml/g dry sludge/hr 6 18 T o t a l tapwater throughput, L 2 . 0 4.0 was 2.5 h r s . Due t o the long c o n t a c t time between the sludge and i t s r e s i d u a l moisture content, g r e a t e r contaminant c o n c e n t r a t i o n s were present i n sample 4 than i n sample 3 i n T e s t I. The same t h i n g o c c u r r e d i n both t e s t s where, due t o the long c o n t a c t times f o r sample 1, the measured c o n c e n t r a t i o n s were much high e r i n sample 1 than i n sample 2. In a r e a l l a n d f i l l , where sludge of t h i s nature i s d i s p o s e d o f , a long c o n t a c t time r e s u l t i n g from a p e r i o d of dry weather or low sludge p e r m e a b i l i t y may produce the same r e s u l t , i . e . , a l e a c h a t e having r e l a t i v e l y h i g h p o l l u t a n t c o n c e n t r a t i o n s . Temperature was expected to a f f e c t the k i n e t i c s and e q u i l i b r i u m of the many p h y s i c a l and chemical r e a c t i o n s o c c u r r i n g d u r i n g the l e a c h i n g p r o c e s s . The data i n Table XIII however, shows no s i g n i f i c a n t d i f f e r e n c e between sample 5 at 4°C and sample 6 at 22°C. TABLE XIII ANALYTICAL RESULTS FOR SLUDGE LEACHING TEST I Sample 1 D e s c r i p - ] t i o n Through-put V o l . (L) Contact Time (hrs) Leaching Temp. <°C) Co l o r (units) COD TC TOC TS TSS Ca Fe Mn Zn Drained L i q u i d 0.4 - 22 500 520 400 305 1,500 200 170 12.8 4.0 0 .100 Leaching Sample 1 0.4 >48 22 300 260 220 145 655 70 75 5.3 1.7 0 .020 2 0.8 ^ 8 22 200 90 85 65 230 32 40 2.6 0.70 0 .010 3 1.2 ^ 8 22 200 60 65 40 230 16 48 1.8 0.80 0 .020 4 1.4 48 22 180 120 85 50 320 <16 68 2.8 1.60 0 .005 5 1.6 ^ 8 4 130 53 51 30 165 «16 48 1.4 0.80 0 .005 6 1.8 ^8 22 120 60 55 30 150 0 48 1.4 0.80 0 .005 7 2.0 ^8 22 100 30 48 27 130 0 48 1.4 0.70 0 .000 Tap Water - - - A/ o 4 5 1 50 ^0 12 0.1 0.0 0 .015 1 A l l u n i t s are i n mg/1 u n l e s s otherwise s p e c i f i e d ; and a l l analyses were done on u n f i l t e r e d samples except c o l o r . TABLE XIV ANALYTICAL RESULTS FOR SLUDGE LEACHING TEST I I Sample Throughput C o l o r TS TDS COD TC TOC Ca D e s c r i p t i o n Volume (L) (units) T ^* D 2 T D T D T D Drained L i q u i d (0.26) 1200 3320 2420 1820 610 960 430 720 220 420 400 Leaching Sample 1 0.8 500 810 670 520 185 220 140 140 70 136 132 2 1.6 150 160 125 60 35 50 36 22 11 35 36 3 2.4 120 120 90 45 25 45 35 18 12 35 36 4 3.2 90 105 70 40 25 40 27 18 9 35 33 5 4.0 90 55 35 25 25 35 27 13 8 35 33 Tap Water - 0 50 A/ 0 9 9 5 5 3 3 19 12 1 A l l u n i t s are i n mg/1 u n l e s s otherwise s p e c i f i e d . 2 T = T o t a l ; D = D i s s o l v e d or f i l t e r e d . U l TABLE XIV (cont'd) ANALYTICAL RESULTS FOR SLUDGE LEACHATE TEST I I Sample Throughput Fe Mn Zn Cr A l N i Pb D e s c r i p t i o n Volume (L) ip2 D 2 T D T D T T T T Drained L i q u i d ( 0 . 2 6 ) 0 . 7 7 0 . 3 7 0 . 3 1 0 . 2 1 . 1 6 0 . 1 6 0 . 0 6 0 . 5 1 . 0 0 9 * Leaching Sample 1 0 . 8 0 . 2 5 0 . 1 6 0 . 1 0 0 . 0 7 . 0 2 0 . 0 2 0 . 0 2 0 . 1 8 . 0 0 3 . 0 1 6 2 1 . 6 0 . 1 2 0 . 0 5 0 . 0 5 0 . 0 3 . 0 1 0 . 0 1 5 . 0 0 2 . 0 7 . 0 0 1 . 0 0 2 3 2 . 4 0 . 0 5 0 . 0 5 0 . 0 4 0 . 0 2 . 0 0 5 . 0 0 0 . 0 0 2 . 0 6 A / . 0 0 1 . 0 0 2 4 3 . 2 0 . 0 5 0 . 0 5 0 . 0 4 0 . 0 2 . 0 1 0 . 0 2 0 . 0 0 2 . 0 6 < . 0 0 1 < . 0 0 2 5 < ; 4 . 0 0 . 0 5 0 . 0 5 0 . 0 2 0 . 0 2 . 0 1 5 . 0 0 0 < . 0 0 2 . 0 6 < . 0 0 1 ^ . 0 0 2 Tap Water - 0 . 0 3 0 . 0 3 0 . 0 2 0 . 0 2 . 0 2 0 . 0 1 5 . 0 0 2 . 0 6 /v/.OOl < . 0 0 2 1 A l l u n i t s are i n mg/1 u n l e s s otherwise s p e c i f i e d . 2 T = T o t a l c o n c e n t r a t i o n ; D = D i s s o l v e d c o n c e n t r a t i o n . * Unreasonable v a l u e , datum l e f t out. 59 Table XIV shows t h a t a major p o r t i o n of the t o t a l c o n c e n t r a -t i o n of COD, TC and TOC i n the sludge l e a c h a t e was due to suspen-ded s o l i d s , e s p e c i a l l y at the begi n n i n g of the l e a c h i n g p r o c e s s . On the other hand, i t shows that e s s e n t i a l l y a l l Ca and Zn were present i n s o l u b l e forms. As the l e a c h i n g process went on, the suspended s o l i d s content i n the sample g r a d u a l l y reduced, and consequently the importance of the suspended s o l i d s c o n t r i b u t i o n g r a d u a l l y d i m i n i s h e d . To e v a l u a t e the a b i l i t y of the sludge to r e t a i n the v a r i o u s p o l l u t a n t s i t had co n c e n t r a t e d from the b i o l o g i c a l treatment process such as metals, a mass balance was c a r r i e d out based on the i n f o r m a t i o n p r o v i d e d i n Tables X I I , XIII and XIV. The r e s u l t s of t h i s mass balance i n Table XV show t h a t no Zn has been leached out a t the given r a t e of p e r c o l a t i o n . In f a c t , the Zn content of the tap water had a tendency t o be adsorbed by the sludge s o l i d s . On the oth e r hand, a s i g n i f i c a n t percentage of Cr i n sludge was r e l e a s e d t o the l e a c h i n g water i n the e a r l y stages o f the l e a c h i n g p r o c e s s . The a f f i n i t y of Fe, Mn, Ca and A l f o r the sludge s o l i d phase f e l l between Zn and Cr. S t i l l , these metals remained a s s o c i a t e d with sludge reasonably w e l l . No proper mass balance was p o s s i b l e f o r Ni and Pb because of the la c k of data. However, t h e i r d i s t r i b u t i o n s between s e t t l e d e f f l u e n t s and sludge s o l i d s (Tables V I I I and XVIII) i n d i c a t e t h a t Ni would l e a c h out e a s i l y , while Pb would be mostly r e t a i n e d i n the sludge. When the same mass balance i s a p p l i e d to COD and TOC, the TABLE XV MASS BALANCE FOR SLUDGE LEACHING TESTS* Tes t No. Parameter Cone, i n Wet Sludge (mg/1) T o t a l Amt. i n Sludge (mg) Amount i n Free Drain (mg) Amount Leached out (mg) T o t a l out of Sludge (mg) T o t a l % out Zn 34.9 20.4 0.04 -0.01 0.03 0.1 I Ca 11,800 6,900 68 80 148 2.1 Fe 607 355 5.1 4.7 9.8 2.8 Mn 122 71.4 1.6 1.9 3.5 4.9 Zn 10.2 3.83 0.04 -0.04 0.00 0 Mn 140 52.5 0.08 0.12 0.20 0.4 Ca 28 ,000 10,500 109 221 330 3.1 II Fe 32.0 12.0 0.20 0.30 0.50 4.2 A l 12.7 4.76 0.13 0.10 0.23 4.8 Cr 0.59 0.22 0.016 0.016 0.032 14.5 COD 18,400 6,900 474 516 990 14 .3 TOC 5,960 2,240 187 158 345 15.4 * R e s u l t s o f Te s t I and Tes t I I are comparable c o n s i d e r i n g the combination of l e a c h i n g r a t e and t o t a l throughput volume. A l s o , t o t a l c o n c e n t r a t i o n s were shown i n t a b l e . 61 percentages leached were 14.3 and 15.4 r e s p e c t i v e l y . Although COD and TOC are no n - c o n s e r v a t i v e , these f i g u r e s i n d i c a t e t h a t a t l e a s t 15% of the o r g a n i c carbon a s s o c i a t e d with the sludge would be leached out by p e r c o l a t i n g water. S i g n i f i c a n t amounts of some of the metals might, i n the long run, be r e l e a s e d from the sludge through the i n e v i t a b l e b i o l o g i c a l o x i d a t i o n of the b i o d e -gradable r e s i d u a l o r g a n i c s . In summary, t h i s study showed t h a t , under the given l e a c h i n g r a t e s and time p e r i o d s , most of the metals a s s o c i a t e d w i t h the sludge tended to remain with the s o l i d s phase. Only a smal l f r a c t i o n would be leached out by p e r c o l a t i n g water i n the l a n d f i l l . 4-4 Removal of A r o c l o r 125 4 - A PCB As s t a t e d i n Chapter 3, a p r e l i m i n a r y t e s t had i n d i c a t e d t h a t the d i s s o l v e d o r g a n i c r e s i d u a l s i n the b i o l o g i c a l s e t t l e d e f f l u e n t s would not cause i n t e r f e r e n c e with the d e t e c t i o n of the PCB s p i k i n g s o f 50 and 250 jug/1 of A r o c l o r 1254. Fu r t h e r experiments u s i n g a c o n t r o l r e a c t o r showed t h a t the de t e r m i n a t i o n of A r o c l o r 1254 t r e a t a b i l i t y through the aerated b i o l o g i c a l system was out of the q u e s t i o n because of the l o s s of A r o c l o r 1254 to the r e a c t o r w a l l and/or the a i r . In order to study the r e l a t i v e importance of these two p o s s i b l e mechanisms of l o s s , a beaker t e s t was i n i t i a t e d ( S e c t i o n 3-6). Table XVI summarizes the r e s u l t s of t h i s beaker t e s t . I t shows t h a t the major l o s s of A r o c l o r 1254 (92% i n 12 hrs) i n the c o n t r o l r e a c t o r was due to the a e r a t i o n p r o c e s s . Only a 62 TABLE XVI BEAKER TEST RESULTS FOR PCB REMOVAL Time Lapse(hrs) PCB Remaining (%) Beaker A 1 Beaker B 2 0 100 100 12 84 8 24 82 3 60 70 1 Spiked with 250 ppb A r o c l o r 1254, no a e r a t i o n . 2 Spiked with 250 ppb A r o c l o r 1254, with a e r a t i o n . s m a l l f r a c t i o n (30% i n 60 hrs) was e i t h e r adsorbed on the r e a c t o r w a l l or v o l a t i l i z e d . The b u b b l i n g a c t i o n of the a e r a t i o n p r o-cess generated numerous l i q u i d d r o p l e t s of v a r i o u s s i z e s which e i t h e r shot out of the r e a c t o r or escaped t o the a i r i n the form of a e r o s o l s . S u b s t i t u t i n g a l e s s v o l a t i l e s p i k i n g s o l v e n t f o r a l c o h o l may h e l p t o slow down the v o l a t i l i z a t i o n p r o c e s s , but s t i l l would not s o l v e the b a s i c problem caused by a e r a t i o n . In the case of l a r g e s c a l e systems such as b i g lagoons, where PCB i s presen t without any accompanying v o l a t i l e s o l v e n t , the v o l a t i l i z a t i o n i s expected to be minimized and l a r g e l i q u i d d r o p l e t s would f a l l back i n t o water. S t u d i e s of b i o l o g i c a l d e gradation of PCB should t h e r e f o r e more p r o p e r l y be performed onl y i n l a r g e s c a l e systems. However, the a e r o s o l s generated by the a e r a t i o n process may c o n t a i n s i g n i f i c a n t amounts of PCB and render a h e a l t h hazard t o people i n the v i c i n i t y . 63 4-5 T o x i c i t y Assessment Table XVII shows the L C 5 0 and ROB t e s t r e s u l t s f o r the raw l e a c h a t e s and the s e t t l e d e f f l u e n t s from a e r o b i c b i o l o g i c a l treatment. Table XVIII l i s t s the sample c h a r a c t e r i s t i c s i n the above t e s t s . A l s o shown i n Table XVIII i s the composition of ML I I , the mixed l i q u o r from t r e a t i n g RL I I a t 9 C of 10 days. These r e s u l t s have been l i s t e d so t h a t a comparison can be made between the treatment outcome f o r RL II and t h a t f o r RL I as shown i n Table V I I I . TABLE XVII TOXICITY BIOASSAY TEST RESULTS* ROB pH T h r e s h o l d A j u s t e d Value RL I 7.5 - NP 7.0 ** SE I 8.4 - NP 7.0 >100% RL II 6.7 NP 4.2% 7.0 7.7% SE I I 8.6 7.0 61% 7.0 72% * A l l r e s u l t s expressed i n percent volume/volume. ** No number ob t a i n e d due t o e x c e s s i v e oxygen demand problem. NP = Not performed; SE = S e t t l e d e f f l u e n t . Cameron ' had found t h a t l e a c h a t e t o x i c i t y was s i g n i f i -c a n t l y reduced when the sample pH was lowered. A p p l y i n g h i s r e l a t i o n s h i p t o the ROB t o x i c i t y of 7 . 7 % f o r RL II produces a T • J, • l 96-hr L C 5 u I n i t i a l o u Sample pH T o x i c i t y p A d j u s t e d L e v e l 64 TABLE XVIII SAMPLE CHARACTERISTICS FOR TOXICITY TESTS .Ch.ar.ac t e r i s t i c s 2 RL I 3 SE I. RL II SE II ML II COD 1760 175 4720 600 1850 BOD5 1040 7 2980 18 260 TC 780 84 1830 420 1020 TOC 630 9 1600 210 580 TS 2980 1250 6490 2370 5200 TDS 2880 1240 6470 2330 2330 PH 7.5 8.4 6.7 8.6 8.6 Ac i d i t y (pH8.3) 222 0 790 0 0 A l k a l i n i t y (pH3.7) 730 360 3050 850 2015 TKN 9.34 3.41 46 .0 33.8 108 NH3-N 3.0 0.3 37.5 NA NA Total-P 4.82 0.45 3.1 1.35 28.5 S0 4 278 256 83 168 148 CI 125 232 390 545 534 B 6.05 5.96 7.43 6.58 6.93 Ca 560 182 965 194 870 Na 118 122 358 342 350 K 44.0 44.2 127 112 105 Mg 39.2 36.4 74 66.2 67.4 Fe 20.2 0.67 1.77 0.48 1.91 Mn 4.10 0.04 7.76 0.23 7 . 30 Zn 1.17 0.10 0.55 0.03 0.59 A l 0.33 0.07 1.26 0.25 1.02 Cr 0.017 0 .006 0.085 0 .056 0.086 Cu 0.030 0.033 40 .01 0.02 0 .05 Ni 40.002 40.002 0.012 0.009 0.011 Pb 0.045 0.003 0.023 0.003 0.021 Cd 0.0015 40.0005 40.001 40.004 40.005 Se 0.024 0.038 0 .013 0 .0013 0.0048 As 0.027 0 .011 NA 0.015 0 .025 Sulfide 1 0.026 40.02 ~30 NA NA 1 RL = Raw leachate; SE = Settled e f f l u e n t ; ML - Mixed liquor NA = Not analyzed. 2 A l l units are in mg/1 except pH. 3 Measured pH d i f f e r e n t from those shown before due to time/oxidation e f f e c t . value of about 4.0% at pH 6.7. T h i s agrees c l o s e l y with the 96-hr L C 5 Q of 4.2% f o r t h i s sample. I t i s f e l t reasonable to assume t h e r e f o r e t h a t the 96-hr L C ^ Q f o r S E I would be comparable to the ROB t o x i c i t y which i s g r e a t e r than 100%. T h i s assumption (29) i s supported by the f i n d i n g s of V i g e r s and Maynard who concluded t h a t 96-hr LC50 t o x i c i t y v a l u e s were comparable to those determined i n the ROB t e s t . A comparison of the compositions of S E I and S E II immedi-a t e l y r e v e a l s why the ROB t e s t s showed S E I as n o n - t o x i c while S E II had a 72% t h r e s h o l d c o n c e n t r a t i o n . T h i s d i f f e r e n c e was due to the presence of h i g h e r c o n c e n t r a t i o n s of almost every c o n s t i t u e n t i n S E II such as heavy metals, r e s i d u a l o r g a n i c s , s o l i d s , TKN, and probably a l s o NH3-N, s u l f i d e and some other (20 34) p o t e n t i a l l y t o x i c substances. ' ' Note t h a t i n a d d i t i o n to SO4, Fe and B, the Mn c o n c e n t r a t i o n i n S E II a l s o f a r exceeds the P.C.B. g u i d e l i n e s . I t i s l i k e l y , however, t h a t S E II would be n o n - t o x i c a f t e r being s u b j e c t e d to a c t i v a t e d carbon p o l i s h i n g . Table XIX presents a summary of the t o x i c i t y data and para-l l e l l e a c h a t e q u a l i t y o b t a i n e d i n t h i s and two other comparable Richmond L a n d f i l l l e a c h a t e s t u d i e s . I t shows t h a t the measured t o x i c i t y of RL II i n t h i s study i s much g r e a t e r than those from other s t u d i e s . T h i s i s thought to be due t o the lower p o l l u t a n t c o n c e n t r a t i o n s i n other s t u d i e s , which probably r e s u l t e d from one or more of the f o l l o w i n g f a c t o r s : (1) l o c a t i o n of l e a c h a t e source w i t h i n the l a n d f i l l , (2) chemical and/or b i o l o g i c a l o x i d a -t i o n d u r i n g r e t e n t i o n i n the d i t c h e s , (3) d i l u t i o n by r i v e r or 66 TABLE XIX SUMMARY OF TOXICITY DATA AND PARALLEL LEACHATE QUALITIES FROM DIFFERENT RICHMOND LANDFILL LEACHATE STUDIES Reference 35 6 35 T h i s Study Leachate No. RL A RL B RL C RL II Sampling S i t e No.8 Road D i r e c t D i s - N. S p r i n g N. Spring i n Richmond D i t c h Near charge t o before i n t o b efore i n t o L a n d f i l l South End F r a s e r R. No.8 Road N. D i v e r s i o n D i t c h D i t c h Leachate Composition: COD 300 290 1800 4720 BOD 5 18 NA 345 2980 TS 2430 2000 3270 6490 A l k a l i n i t y 875 800 1780 NA TKN NA NA NA 46 NH3-N 10 16 48 38 P 0.33 0 .16 3.6 3.1 C l 820 500 350 390 Na NA 400 NA 358 Ca 190 180 460 1065 Mg 61 60 65 84 Fe 6.3 36 20 1.6 Mn NA 2.1 NA 7.8 Zn 0.22 0.24 5.3 0.55 Pb 0.02 0.04 0.13 0.023 pH 7.6 7.0 7.6 6.7 S u l f i d e 0.01 NA 0.01 30 96-hr LC50 NA NA NA 4.2% ( o r i g i n a l pH) 96-hr L C 5 0 (pH -> 7.0) > 100% 44% 22% NA ROB (pH 7.0) 58% NA 32% 7.7% NA = Not analyzed or not performed. 67 e s t u a r y t i d a l w a t e r as r e f l e c t e d by t h e h i g h s o d i u m a nd c h l o r i d e c o n c e n t r a t i o n s . I n summary, t h i s t o x i c i t y a s s e s s m e n t s t u d y showed t h a t i t i s p o s s i b l e t o t r e a t t h e R i c h m o n d L a n d f i l l l e a c h a t e t o a n o n -t o x i c l e v e l u s i n g an a e r a t e d d i g e s t i o n p r o c e s s a l o n e , when t h e l e a c h a t e s t r e n g t h i s t h a t o f o r no h i g h e r t h a n RL I . F o r l e a c h a t e o f t h e s t r e n g t h o f RL I I , t h e a d d i t i o n o f a c t i v a t e d c a r b o n p o l i s h i n g may a l s o p r o d u c e a n o n - t o x i c f i n a l e f f l u e n t . 68 CHAPTER 5 COST ANALYSIS 5-1 I n t r o d u c t i o n The purpose of t h i s chapter i s to p r o v i d e a c o s t comparison f o r a b i o l o g i c a l treatment system, u s i n g an a e r a t e d lagoon s i z e based on s e v e r a l s e l e c t e d s o l i d s d e t e n t i o n times. While there are many a l t e r n a t i v e s f o r the design and c o n s t r u c t i o n of an aerated lagoon at the l a n d f i l l s i t e , only one method was s e l e c t e d . T h i s was f e l t t o be s u f f i c i e n t t o show the e f f e c t of i n c r e a s i n g d e t e n t i o n times on c o s t . The design a l t e r n a t i v e chosen was to p r e - l o a d the lagoon s i t e with dredged sand, thereby m i n i m i z i n g the f u t u r e peat s e t t l e m e n t . Without p r e l o a d i n g t h i s settlement would cause s i g n i f i c a n t c o n s t r u c t i o n and o p e r a t i o n problems f o r the lagoon system. Subsequent e x c a v a t i o n and removal of p a r t of the p r e - l o a d and l i n i n g the lagoon with impermeable m a t e r i a l was a l s o i n c l u d e d . The p r e - l o a d method i s l i k e l y the most c o s t l y , but does serve the purpose of showing a c o s t comparison. From a treatment e f f i c i e n c y p o i n t of view, i t has been shown t h a t the optimum 9 C i s 7 days f o r RL I and 10 days f o r RL I I . I t has a l s o been shown t h a t f o r RL I, a 9 C of 3 days w i l l produce a s e t t l e d e f f l u e n t of high q u a l i t y t h a t meets P.C.B. standards almost as w e l l as the 7-day 9 C s e t t l e d e f f l u e n t . Three d e t e n t i o n times of 3, 5 and 10 days have t h e r e f o r e been s e l e c t e d f o r c o s t a n a l y s i s . They are intended to cover the many f a c t o r s which may have e i t h e r p o s i t i v e or negative e f f e c t s on the l e a c h a t e 69 treatment e f f i c i e n c y such as d i l u t i o n and o x i d a t i o n of leac h a t e w i t h i n the c o l l e c t i o n d i t c h e s , f l u c t u a t i o n s of l e a c h a t e flow and the changes i n f i e l d temperature d u r i n g d i f f e r e n t seasons of the year. Based on three assumptions: (a) a p r e c i p i t a t i o n r a t e of 1,020 mm (40 inches) per year, (b) a l a n d f i l l area of 1.25 km 2 (310 a c r e s ) , and (c) n e g l i g i b l e s u r f a c e r u n o f f and e v a p o r a t i o n , the l e a c h a t e flow r e s u l t i n g from r a i n f a l l would average 3.5x10^ L/day (770,000 I g a l / d a y ) . I n c l u d i n g i n f i l t r a t i o n from the F r a s e r R i v e r , the t o t a l d e s ign flow was chosen to be 4.5x10^ L/day ( l x l O 6 Igpd). 5-2 Design C a l c u l a t i o n s and C o n s i d e r a t i o n s Based on the r e s e a r c h conducted the design c r i t e r i a used f o r the c o s t a n a l y s i s of an aera t e d lagoon a r e : I n f l u e n t BOD 5 1,000 mg/1 E f f l u e n t BOD 5 (av.) MLVSS (av.) 500 mg/1 10 mg/1 Growth parameters: Y b K 0.040 d a y - 1 4.5 d a y - 1 99 mg/1 0.59 mgVSS/mgBOD5 A e r a t o r 1.2 Kg 02/KWH or 2.0 l b 0 2/HP-hr under f i e l d c o n d i t i o n s Sludge p r o d u c t i o n (av.) 6,800 Kg/day or 15,000 lbs/day dry weight Water depth ( f o r lagoon and s e t t l i n g basin) 3 m (10 f t ) Average win t e r l i q u i d temperature 8°C 1 70 Temperature c o e f f . , © 1.06 (T>20°C) 1.10 (T<20°C) Average f i r s t - o r d e r s o l u b l e . B O D 5~removal-rate 5.0 day" consta n t , k @ 22°C* Design equations given i n M e t c a l f & Eddy, I n c . ^ 3 1 ^ and P a r k e r ^ 3 6 ^ were used t o determine v a r i a b l e s such as lagoon s i z e , oxygen and energy requirements. The r e s u l t s of the c a l c u l a t i o n s are summarized i n Table XX. With the hig h sludge accumulation r a t e shown i n Table XX, a f a c u l t a t i v e lagoon was c o n s i d e r e d t o be i m p r a c t i c a l . A complete-mix a e r o b i c lagoon w i t h a separate, m e c h a n i c a l l y - c l e a n e d s e t t l i n g b a s i n was t h e r e f o r e s e l e c t e d . With poor subsurface c o n d i t i o n s , i t was decided t h a t the s e t t l i n g b a s i n would be b u i l t u s i n g a p i l e supported concrete b a s i n i n order to prevent damage from d i f f e r e n t i a l ground s e t t l e m e n t . Using a c o n s e r v a t i v e overflow r a t e of 19,600 L/day-m 2 (400 I g p d / f t 2 ) , the r e q u i r e d s u r f a c e area of the s e t t l i n g b a s i n would be 230 m2 (2,500 f t 2 ) . T h i s corresponds t o a d e t e n t i o n or s e t t l i n g time of 3.7 h r s . Table XX shows t h a t the power requirements f o r mixing i s the c o n t r o l l i n g f a c t o r f o r s i z i n g a e r a t o r s . I t a l s o shows t h a t a drop of temperature from 22°C t o 8°C c o u l d i n c r e a s e the s e t t l e d e f f l u e n t BOD5 up to a l e v e l of 70 mg/1 dependent on 0 C v a l u e s , * C a l c u l a t e d from measured valu e s of S, S D, X and K s at d i f f e r e n t 0 C ' s , u s i n g the equation S 1 S ° 1 + J 2 - ( Z ) KS+SKQ> (Reference 31) TABLE XX SUMMARY OF AERATED LAGOON DESIGN CALCULATIONS D e s c r i p t i o n 0 C, days 3 5 10 •3 3 Lagoon Volume, m ( f t ) 14 ,000 (480,000) 23,000(800,000) 45,000(1,600,000) Lagoon Surface Area, m (acres) 4,500(1.1) 7,400 (1.8) 15,000(3.6) k @ 8°C, d a y - 1 * 1.4 1.4 1.4 P r e d i c t e d E f f l . BOD 5 @ 8°C,mg/l ** 25-70 25-70 25-70 O2 Requirement, Kg/day(lb/day) 3,400(7,500) 3,400 (7,500) 3,400(7,500) Energy Requirement, KW(HP) f o r a e r a t i o n f o r complete-mix 120(160) 200(270) 120(160) 340 (450) 120(160) 670 (900) Sludge Volume (5% s o l i d s ) , m 3 / d a y ( f t 3 / d a y ) 140(4,800) 140(4,800) 140 (4,800) Sludge Accumulation Rate i n ,^ "ic "K IX Lagoon, m/month(ft/month) 0.91(3.0) 0.55(1.8) 0.27(0.90) C a l c u l a t e d from average k value @ 22°C. I n d i v i d u a l k values @ 8°C may be computed from the corresponding values @ 22°C. A range of BOD5 g i v e n f o r a l l © c ' s because of the u n c e r t a i n t y of the p r e d i c t i o n . One would expect the r e l a t i o n s h i p of high e r BOD5 f o r lower 9 C . I f no separate s e t t l i n g b a s i n p r o v i d e d . 72 not i n c l u d i n g any change i n s o l i d s s e t t l e a b i l i t y . Other design aspects which have been used i n c l u d e the f o l l o w i n g : 1. The use of f l o a t i n g s u r f a c e a e r a t o r s i s c o n s i d e r e d the most p r a c t i c a l f o r mixing as w e l l as oxygen supply, because i t i s f e l t t h a t they would be e a s i e r t o operate and s e r v i c e . "Snake-fusers" may a l s o be c o n s i d e r e d , whereby submerged a i r d i f f u s e r s made of f l e x i b l e p i p i n g a re employed. 2. I f the sludge produced i s t o be r e a p p l i e d t o the l a n d f i l l , a dewatering process i s not c o n s i d e r e d necessary because the lea c h a t e flow i n c r e a s e due to sludge g r a v i t y drainage i s only a steady i n t e r n a l r e c y c l e of a minor f r a c t i o n of the t o t a l hydrau-l i c l o a d i n g . 3. In order t o assure no movement of le a c h a t e i n t o the sub-s o i l , l i n i n g of the s i d e s and bottom of the lagoon with imper-meable b a r r i e r s i s i n c l u d e d . One of the most popular l i n e r s c u r r e n t l y used i s p o l y v i n y l c h l o r i d e (PVC). The c o n s t r u c t i o n of a lagoon l i n e r r e q u i r e s c a r e f u l subgrade p r e p a r a t i o n . L i n e r p r o t e c t i o n with an e a r t h cover 0.6 m (2 f t ) t h i c k , i n a d d i t i o n to the l i n e r i n s t a l l a t i o n , i s i n c l u d e d i n the c o s t a n a l y s i s . 4. For an aerated lagoon of 3.0 m (10 f t ) water depth and 0.9m (3 f t ) bottom matrix of l i n e r and l i n e r p r o t e c t i o n , a c o n s e r v a t i v e estimate of the necessary p r e - l o a d i n g on 4.6 to 6.1 m (15 to 20 f t ) of peat s o i l i s 1500 g/cm 2 (3000 l b s / f t 2 ) or an e q u i v a l e n t dredged sand h e i g h t of 7.3 m (24 f t ) . 73 5-3 Cost Analysis Cost estimates were carried out on the basis of previous design data and points of consideration. It must be remembered however, that the following costs are not absolute costs for leachate treatment but only an estimate of r e l a t i v e costs for the three design detention times. The t o t a l c a p i t a l , operation and maintenance (0 & M) costs include: 1. Pre-loading (cap i t a l only) 2. Lagoon construction and operation (capital including exca-vation, subgrade preparation, l i n e r i n s t a l l a t i o n , l i n e r protection or earth cover, and embankment protection; 0 & M including labor, power and materials) 3. Aerators (flo a t i n g surface,aerators) 4. Engineering and administration (capital only) 5. Land ac q u i s i t i o n (c a p i t a l only) 6. Leachate c o l l e c t i o n and piping system 7. S e t t l i n g basin 8 . Activated carbon system (optional). The costs of the f i r s t f i v e items are functions of 0 C . For the l a s t three items, the costs would be the same for a l l detention times because the sludge production rate, the solids s e t t l e -a b i l i t y , and the se t t l e d e f f l u e n t flow and quality are approxi-mately the same for each 9 C . Costs for land a q u i s i t i o n and leach-ate c o l l e c t i o n and piping have not been included i n t h i s analysis. Costs for activated carbon treatment are l i s t e d 74 s e p a r a t e l y f r o m t h e t o t a l b i o l o g i c a l t r e a t m e n t c o s t s , s o t h a t c o m p a r i s o n s c a n be made t o d e c i d e w h e t h e r t h e i n s t a l l a t i o n o f a c a r b o n s y s t e m i s e c o n o m i c a l l y j u s t i f i e d . The c o s t s f o r p r e - l o a d i n g a n d e x c a v a t i o n were b a s e d on c u r r e n t p r i c e i n f o r m a t i o n s u p p l i e d by l o c a l c o n t r a c t o r s . The c o s t f o r l i n e r i n s t a l l a t i o n i n c l u d i n g s u b g r a d e and e a r t h c o v e r (37) p r e p a r a t i o n s were o b t a i n e d f r o m G e s w e i n . O t h e r c a p i t a l , o p e r a t i o n and m a i n t e n a n c e c o s t s f o r a e r a t e d l a g o o n w e r e e s t i -(38) m a t e d e i t h e r f r o m B l a c k and V e a t c h ' o r f r o m Adams and (39) E c k e n f e l d e r . A l l c o s t s w e re b r o u g h t t o May, 1978 w h e r e v e r a p p l i c a b l e . The E n g i n e e r i n g N e w s - R e c o r d (ENR) C o n s t r u c t i o n C o s t I n d e x was u s e d t o u p d a t e t h e o p e r a t i o n a n d m a i n t e n a n c e c o s t s . An a v e r a g e p a y r a t e o f $12.00 p e r man-hr, i n c l u d i n g o v e r h e a d c o s t s , was u s e d i n e s t i m a t i n g l a b o r c o s t s . F o r power r e q u i r e m e n t s , a c o s t o f 3C/KWH was u s e d . C a p i t a l c o s t s h a v e b e e n a m o r t i z e d o v e r 20 y e a r s a t 9%. C o s t s f o r a c t i v a t e d c a r b o n p o l i s h i n g w e r e e s t i m a t e d f r o m t h e EPA T e c h n o l o g y T r a n s f e r M a n u a l and were b a s e d on a c a r b o n r e q u i r e m e n t o f 400 l b s p e r m i l l i o n g a l l o n s o f d e s i g n f l o w . The r e s u l t s o f t h i s c o s t a n a l y s i s a r e p r e s e n t e d i n T a b l e X X I . I t c a n be s e e n f r o m T a b l e X X I t h a t t h e t o t a l c o s t o f l e a c h -a t e t r e a t m e n t u s i n g an a e r a t e d l a g o o n i n c r e a s e s s t e a d i l y , a l t h o u g h n o t p r o p o r t i o n a l l y , w i t h i n c r e a s i n g l a g o o n s i z e . I t i s a l s o shown t h a t t h e p r e - l o a d i n g c o s t i s one o f t h e m a j o r c o s t s , r a n g -i n g f r o m 26 t o 31% o f t h e t o t a l c a p i t a l c o s t . I n v i e w o f t h e n e g a t i v e e f f e c t s o f t e m p e r a t u r e d u r i n g t h e w i n t e r a n d many o t h e r 75 TABLE XXI COST ESTIMATIONS FOR AERATED LAGOON PROCESS 1 0 C, days 3 5 10 Lagoon Surface Area m 2 ( f t 2 ) 4,500(48,000) 7,400(80,000) 15,000(160,000) S e t t l i n g B a s i n Area m 2 ( f t 2 ) 230(2,500) , 230(2,500) 230(2,500) Power Requirements KW(HP) 200(270) 340(450) 670(900) P r e - l o a d i n g Volume m 3(yd 3) 42,000(56,000) 65,000(86,000) 130,000(17 4,000) Exc a v a t i o n Volume M 3(yd 3) 32,000(43,000) 53,000(70,000) 104,000(138,000) Estimated L i n i n g Area m 2(yd 2) 5,900(7,100) 9,700(11,700) 18,000(21,700) C a p i t a l Cost, $ p r e - l o a d i n g 168,000 173,000 349,000 e x c a v a t i o n 43,000 77,000 166,000 l i n i n g 2 " 25,000 41,000 76,000 a e r a t o r s 112,000 168,000 299,000 embankment 11,000 15,000 26,000 s e t t l i n g b a s i n 3 134,000 134,000 134,000 e n g i n e e r i n g & admin. 60,000 70,000 102,000 T o t a l C a p i t a l Cost, $ 542,000 663,000 1,126,000 C a p i t a l Recovery, $/yr 60,000 73,000 124,000 Annual O & M, $ la b o r 10,000 12,000 14,000 power 53,000 88,000 176,000 m a t e r i a l s 4,000 6,000 8,000 s e t t l i n g b a s i n 4 18,000 18,000 18,000 T o t a l 0 & M, $/yr 85,000 124,000 216,000 T o t a l Cost of Aerated Lagoon, C/IOOO I g a l 40 54 93 Act. Carbon P o l i s h i n g , ^ c a p i t a l c o s t , $ 1,200,000 1,200,000 1,200,000 c a p i t a l r e c o v e r y , $/yr 132,000 132,000 132,000 O & M c o s t , $/yr 15,000 15,000 15,000 T o t a l a d d i t i o n a l Cost, A c t . Carbon, C/lOOOIgal 40 40 40 1 A l l c o s t s are i n U.S. d o l l a r s . 2 I n c l u d i n g subgrade and e a r t h . 3 Cost i n c l u d i n g concrete and c o l l e c t i n g equipment. 4 Estimated from primary sedimentation b a s i n f i g u r e s . 5 Costs i n c l u d i n g pumping, r e g e n e r a t i o n and make-up carbon. 76 unknown f a c t o r s a f f e c t i n g the b i o l o g i c a l treatment e f f i c i e n c y , i t i s f e l t t h a t a 8 C of 5 days or more may have t o be used i n s p i t e of the i n c r e a s e d c o s t over t h a t of a 0 C of 3 days. The c o s t o f a c t i v a t e d carbon treatment ranges from 43% t o 100% of the a e r a t e d lagoon c o s t as the d e t e n t i o n time decreases from 10 days t o 3 days. T h i s i n d i c a t e s t h a t the a d d i t i o n of an a c t i v a t e d carbon process f o r p o l i s h i n g may not be c o s t e f f e c t i v e c o n s i d e r i n g the l i m i t e d i n c r e a s e t h i s process p r o v i d e s i n over-a l l treatment e f f i c i e n c y . (41) Recently Chian and DeWalle presented a c o s t e s t i m a t i o n f o r t r e a t i n g l e a c h a t e having a BOD5 of 5,0 00 mg/1 and flow r a t e of 30,000 U.S.gpd u s i n g an aer a t e d lagoon. I n c l u d i n g c o s t s f o r land a c q u i s i t i o n and p i p i n g , but not f o r p r e - l o a d i n g and l i n i n g , they found a treatment c o s t of $4.10/1000 U.S.gal or $4.90/1000 I g a l (August 1977). That i s about f i v e times as hi g h as the c o s t from t h i s study a t 0 C of 10 days. The main reason f o r t h i s d i f f e r e n c e i s t h a t they used a s o l i d s d e t e n t i o n time of 30 days and a design flow r a t e of only 0.03 U.S.mgd. CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS The preceding two chapters have presented the experimental r e s u l t s o b tained i n t h i s r e s e a r c h and a c o s t a n a l y s i s of t r e a t -ment systems. The purpose of t h i s chapter i s to examine the i m p l i c a t i o n s of these r e s u l t s and to make suggestions f o r f u t u r e s t u d i e s , i n c l u d i n g p i l o t - s c a l e r e s e a r c h and f u l l - s c a l e system d e s i g n . 6-1 Co n c l u s i o n s Based upon the r e s u l t s of t h i s r e s e a r c h , some major c o n c l u s i o n s may be drawn as f o l l o w s : (1) The aera t e d lagoon process i s very e f f e c t i v e i n t r e a t i n g the Richmond L a n d f i l l l e a c h a t e to such a q u a l i t y t h a t i s cons i d e r e d a c c e p t a b l e f o r d i s c h a r g e to the F r a s e r Estuary. Only S0 4 and Fe s i g n i f i c a n t l y exceed the P.C.B. 'AA' l e v e l standards f o r s p e c i f i c d i s c h a r g e s . (2) A c t i v a t e d carbon a d s o r p t i o n g r e a t l y improves the s e t t l e d e f f l u e n t q u a l i t y i n terms of c o l o r , Fe and COD. However, the a d d i t i o n of t h i s p o l i s h i n g process f o r the combined treatment of l e a c h a t e may not be c o s t e f f e c t i v e . (3) From a treatment e f f i c i e n c y p o i n t of view, the optimum s o l i d s d e t e n t i o n time appears to be 7 to 10 days f o r le a c h a t e BOD5 ranging from 1,000 to 3,000 mg/1. 77 78 However, because the p r e d i c t e d 6 f o r f a i l u r e i s 0.42 c days at 22°C f o r a 1,000 mg/1 BOD 5 l e a c h a t e , a 0 c of 2 to 4 days seems p o s s i b l e . Using a va l u e o f 8 c lower than 7 days c o u l d c o n s i d e r a b l y reduce both c a p i t a l and o p e r a t i o n c o s t s . (4) Chemical p r e c i p i t a t i o n as a r e s u l t of n a t u r a l pH i n c r e a s e d u r i n g b i o l o g i c a l treatment i s the major f a c t o r c o n t r i -b u t i n g to the observed low MLVSS/MLSS r a t i o of 0.30. (5) For i n f l u e n t COD of 1,600 to 1,800 mg/1 and wit h MLVSS c o n c e n t r a t i o n s ranging between 360 and 560 mg/1, the s e t t l e d e f f l u e n t COD removal i n c r e a s e s from 82.6 to as high as 90.1% when 9 c i s i n c r e a s e d from 2 to 10 days (F/M r a t i o decreases from 0.93 to 0.2 6 mg B0D5/mg VSS/ day). For the corres p o n d i n g i n f l u e n t BOD^ of about 1,000 mg/1 and with e=c g r e a t e r than 3 days, the BOD^ removals average 99.1% and the s e t t l e d e f f l u e n t BOD^'s are no g r e a t e r than 10 mg/1. T h i s i n d i c a t e s t h a t the raw l e a c h a t e can be almost completely biodegraded by ae r o b i c d i g e s t i o n . (6) Many of the metals i n l e a c h a t e feed end up a s s o c i a t e d w i t h the sludge s o l i d s , through removal by b i o l o g i c a l adsorption/entrapment and /or through chemical p r e c i p i t a -t i o n due to pH change. The metal removal e f f i c i e n c y i n a e r o b i c treatment i s g r e a t e r than 95% f o r Fe and Mn, b e t t e r than 90% f o r Zn and Pb, and about 80% f o r A l . Metals expected to be mainly or s i g n i f i c a n t l y removed by chemical p r e c i p i t a t i o n i n c l u d e Ca, Fe, Mn, Zn and Pb. (7) Because of the d e f i c i e n c y of n i t r o g e n and phosphorus i n raw l e a c h a t e , n u t r i e n t a d d i t i o n i s d e f i n i t e l y necessary to ensure e f f e c t i v e b i o l o g i c a l treatment. A n a l y s i s of the n u t r i e n t s i n the s e t t l e d e f f l u e n t s i n d i c a t e d t h a t a BOD^:N:P r a t i o of 100:5:1 was s a t i s -f a c t o r y , and the n i t r o g e n and phosphorus a d d i t i o n s to the l e a c h a t e feed d i d not appear to be s i g n i f i c a n t l y e x c e s s i v e . (8) The k i n e t i c parameters f o r t h i s l e a c h a t e are very s i m i l a r to those f o r domestic sewage. T h i s suggests t h a t the c o n c e n t r a t i o n s of p o l l u t a n t s , such as heavy metals, i n the l e a c h a t e are not high enough to cause s i g n i f i c a n t i n h i b i t i o n of b i o l o g i c a l growth. I t i s a l s o very l i k e l y t h a t t h i s l e a c h a t e c o u l d be combined wit h domestic sewage i n a high percentage f o r a e r o b i c treatment without producing adverse e f f e c t s . (9) A c t i v a t e d carbon i s very e f f e c t i v e i n removing c o l o r , r e s i d u a l o r g a n i c s and i r o n from s e t t l e d e f f l u e n t , but does nothing to s u l f a t e (and probably boron as w e l l ) . The o v e r a l l removal e f f i c i e n c i e s f o r COD and Fe i n l e a c h a t e were g r e a t e r than 99% with a column c o n t a c t time of 10 min. As a r e s u l t , a l l parameters i n the p o l i s h e d f i n a l e f f l u e n t meet the P.C.B. standards, 80 except s u l f a t e and p o s s i b l y boron. (10) Under the t e s t c o n d i t i o n s used, i t appears t h a t the b i o l o g i c a l sludge from a e r o b i c treatment can be disposed of i n t o a l a n d f i l l without p r e s e n t i n g severe d e s o r p t i o n problems. Most of the metals a s s o c i a t e d with the sludge such as Zn, Fe, Mn, A l and Ca tend t o remain with the s o l i d phase, and onl y a small f r a c t i o n w i l l be leached out by p e r c o l a t i n g water. On the other hand, the t o t a l mass of Cr leached was 14.5% of the Cr contained i n the sludge. (11) The removal study f o r a PCB, such as A r o c l o r 1254, by a e r o b i c d i g e s t i o n was not f e a s i b l e because of the severe and r a p i d l o s s of A r o c l o r 1254 r e s u l t i n g from the r e q u i r e d a i r b u b b l i n g o p e r a t i o n . In a f u l l s c a l e lagoon, where l o s s of d r o p l e t s due to edge e f f e c t i s n e g l i g i b l e , a PCB removal study may show some encourag-in g r e s u l t s . (12) The 96-hr L C 5 0 v a l u e f o r Richmond L a n d f i l l l e a c h a t e i s as low as 4.2%, I t i s p o s s i b l e to t r e a t t h i s l e a c h a t e to n o n - t o x i c l e v e l s , u s i n g an aerated lagoon p r o c e s s , as long as the le a c h a t e s t r e n g t h i s at the l e v e l of 1,000 mg/1 B O D 5 . F o r leac h a t e of s t r e n g t h comparable to 3,000 mg/1 BOD5, the a d d i t i o n of a c t i v a t e d carbon p o l i s h i n g may be necessary t o reduce the e f f l u e n t t o x i -c i t y t o below the non - t o x i c l e v e l . 81 (13) The high sludge p r o d u c t i o n and accumulation r a t e i s f e l t to r e q u i r e a separate s e t t l i n g b a s i n equipped with a mechanical sludge c l e a n i n g d e v i c e f o r f u l l s c a l e lagoon treatment. (14) In view of the e f f e c t s of winter temperature on BOD^ removal and sludge s e t t l e a b i l i t y , as w e l l as many other unknown f a c t o r s on the o v e r a l l b i o l o g i c a l treatment e f f i c i e n c y , i t i s f e l t t h a t a s o l i d s d e t e n t i o n time of 5 days or more would be the most r e a l i s t i c approach d e s p i t e the economics f a v o r i n g s h o r t e r 9 6-2 Recommendations Th i s r e s e a r c h has p r o v i d e d answers to some of the q u e s t i o n s concerning the treatment and d i s p o s a l of a low-strength m u n i c i p a l l a n d f i l l l e a c h a t e . However, i t i s b e l i e v e d t h a t f u r t h e r s t u d i e s are necessary before a f u l l - s c a l e treatment system can be designed. These i n c l u d e : (1) The i n v e s t i g a t i o n of temperature e f f e c t s on the a e r o b i c d i g e s t i o n of l e a c h a t e . The a e r o b i c treatment of l e a c h a t e has been c a r r i e d out at room temperature throughout t h i s study. Since the temperature of the Lower Mainland of B r i t i s h Columbia goes below the f r e e z i n g p o i n t i n the w i n t e r , i t i s important to determine how the lowering of temperature below 20°C a f f e c t s the treatment e f f i c i e n c y of the b i o l o g i c a l system. 82 (2) The det e r m i n a t i o n of optimum n u t r i e n t requirements. Although the BOD5:N:P r a t i o of 100:5:1 used i n t h i s study was s a t i s f a c t o r y , reduced n u t r i e n t a d d i t i o n s might be p o s s i b l e . (3) More d e t a i l e d s t u d i e s i n a c t i v a t e d carbon p o l i s h i n g . The optimum carbon treatment system should be determined i f the p o l i s h i n g i s found necessary i n the f i e l d . T h i s would i n c l u d e the s e l e c t i o n of the best combination of carbon type, c o n t a c t time and h y d r a u l i c l o a d i n g r a t e , based upon breakthrough of a s e l e c t e d p o l l u t a n t whose c o n c e n t r a t i o n exceeds P.C.B. standards. Larger columns should be used t o minimize the w a l l e f f e c t s of sample s h o r t - c i r c u i t i n g . A study of the r e g e n e r a t i o n of spent carbon i s a l s o recommended. (4) F u r t h e r study of sludge d e s o r p t i o n . In t h i s r e s e a r c h , sludge l e a c h i n g t e s t s were conducted at room temperature and a t a tap water a p p l i c a t i o n r a t e of about 1 cm/hr. That i s e q u i v a l e n t t o 8 8,0 00 mm/yr (3,500 i n / y r ) as opposed t o the n a t u r a l p r e c i p i t a t i o n r a t e of 750 to 1,000 mm/yr (30 to 40 i n / y r ) . T h i s high a p p l i c a t i o n or l e a c h i n g r a t e was designed t o generate enough volume of le a c h a t e i n a sh o r t p e r i o d of time f o r a n a l y s i s . For f u t u r e study, i t i s important t h a t the tap water a p p l i c a t i o n r a t e s be no g r e a t e r than, say, 5,000 mm/yr (200 i n / y r ) . T h i s would r e q u i r e a l a r g e q u a n t i t y of sludge, i n order t o produce more and l a r g e r 83 sludge beds, such t h a t enough l e a c h a t e p o r t i o n s c o u l d be c o l l e c t e d f o r a n a l y s i s i n a reasonable l e n g t h of time. (5) P i l o t - S c a l e S t u d i e s . In order to determine the most c o s t e f f e c t i v e l e a c h a t e treatment scheme f o r a f u l l - s c a l e system, p i l o t - s c a l e s t u d i e s may be s e t up a t the Richmond L a n d f i l l s i t e . T h i s might i n c l u d e the i n s t a l l a t i o n of a l e a c h a t e c o l l e c t i o n system and three p i l o t - s c a l e (say, 200 to 500-L volume each) complete-mix ae r a t e d tanks, w i t h continuous flow and separate s e t t l i n g b a s i n s . The s t u d i e s c o u l d be s t a r t e d with s o l i d s d e t e n t i o n times of 3 , 5 and 7 days. The system would then be monitored throughout the year and 0 c changed whenever necessary, u n t i l an a c c e p t a b l e treatment e f f i c i e n c y i s achieved. The temperature e f f e c t s and n u t r i e n t requirements i n the b i o l o g i c a l system, p l u s the l e a c h i n g c h a r a c t e r i s t i c s and volume of the sludge s o l i d s generated from the lagoons, c o u l d a l s o be determined i n the f i e l d . I f necessary, the optimum carbon treatment system c o u l d be s t u d i e d a t the same time. (6) P i l o t s t u d i e s i n a f u l l - s c a l e system. Another a l t e r n a t i v e f o r determining the most c o s t e f f e c t i v e l e a c h a t e treatment scheme i s to conduct p i l o t s t u d i e s i n i n a f u l l - s c a l e , s i n g l e - c e l l system. T h i s s i n g l e - c e l l 84 lagoon c o u l d be b u i l t , say, based on a 9 C of 3 days, and would be p r o v i d e d with a sludge r e c y c l e f a c i l i t y . The c e l l would be monitored with a d e t e n t i o n time s t a r t i n g a t 3 days, and the treatment e f f i c i e n c y e v a l u -ated. I f a 9 C of 3 days f a i l e d to pr o v i d e s a t i s f a c t o r y treatment, the d e t e n t i o n time could be i n c r e a s e d by r e c y c l i n g an a p p r o p r i a t e amount of sludge u n t i l e f f e c t i v e treatment i s o b t a i n e d . Once the acceptable 9 C i s found, the temperature e f f e c t s and n u t r i e n t requirements, p l u s the sludge l e a c h i n g c h a r a c t e r i s t i c s c o u l d be s t u d i e d . When necessary, the optimum carbon p o l i s h i n g system c o u l d a l s o be determined. The f i n a l system would then be c o n s t r u c t e d . T h i s a l t e r n a t i v e i s c o n s i -dered t o be more advantageous because the c a p i t a l c o s t of a p i l o t f a c i l i t y would be e l i m i n a t e d . I t a l s o c o u l d r e s u l t i n the lowest p o s s i b l e c o s t f a c i l i t y being c o n s t r u c t e d . 85 REFERENCES 1. Pohland, F.G. and Engelbrecht, R.S., "Impact of Sanitary L a n d f i l l - An Overview of Environmental Factors and Control Alt e r n a t i v e s " . Report Prepared for American Paper Inst., 82 pp., February (1976). 2. Rovers, F.A., Nunan, J.P. and Farquhar, G.J., " L a n d f i l l Contaminant Flux - Surface & Subsurface Behavior". Proceed-ings of the 21st Ontario Industrial Waste Conference, p.14, June (1974). 3. Watkins, J.V., "A Study of Leachates from Sanitary F i l l s and Their Effects on Receiving Waters". 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C , Dept. of C i v i l Eng., P o l l u t i o n C o n t r o l E n g i n e e r i n g Group, 33pp., March (1974). 87 25. U l o t h , V.C., "Aerobic B i o s t a b i l i z a t i o n of A High Strength L a n d f i l l Leachate". M.A.Sc. T h e s i s , Univ. of B. C , Dept. o f C i v i l Eng., Vancouver, B.C., 106pp., Feb. (1976). 26. P a l i t , T. and Qasim, S.R., " B i o l o g i c a l Treatment K i n e t i c s of L a n d f i l l Leachate". J . En v i r o n . Engr. Div., ASCE, 103, EE2:353-366 (1977). 27. I n t e r n a l P u b l i c a t i o n , "Procedure f o r A n a l y s i s of Organo-c h l o r i n a t e d P e s t i c i d e and PCB's i n Waters". Water Q u a l i t y Lab, Environment Canada, Canada, A p r i l (1974). 28. Davis, J.C. and Hoos, R.A.W., " S t a n d a r d i z a t i o n o f Salmonid Bioassay Procedures Using Sodium Pentachlorophenate and Dehy d r o a b i e t i c A c i d as Reference T o x i c a n t s " . I n t e r -l a b o r a t o r y C o o p e r a t i v e Study, J . F i s h Research Board, Canada, 3_2, No.3:411 (1975). 29. V i g e r s , G.A. and Maynard, A.W.., "The R e s i d u a l Oxygen B i o -assay: A Rapid Procedure t o P r e d i c t E f f l u e n t T o x i c i t y to Rainbow T r o u t " . Water Research, 11:343-346 (1977). 30. Lawrence, A.W. and McCarty, P.L., "A U n i f i e d B a s i s f o r B i o l o g i c a l Treatment Design and Oper a t i o n " . J . S a n i t a r y Engr. Div., ASCE, 96, No.SA3:757-778, Proc. Paper 7365, June (1970). 31. M e t c a l f , L. and Eddy, H., Inc., Wastewater E n g i n e e r i n g : C o l l e c t i o n , Treatment, D i s p o s a l . McGraw-Hill Book Com-pany, Inc., New York, N.Y. (1972). 32. EPA Technology T r a n s f e r , "Process Design Manual f o r Carbon A d s o r p t i o n " . U.S. EPA, C i n c i n n a t i , Ohio, Oct. (1973). 33. Cameron, R.D., "A Comparison of the Standard TLm Bioassay with the Rapid T o x i c i t y Assessment f o r M u n i c i p a l Refuse and Hog F u e l Leachates". 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Black and Veatch, C o n s u l t i n g E n g i n e e r s , E s t i m a t i n g Costs and Manpower Requirements f o r C o n v e n t i o n a l Wastewater  Treatment F a c i l i t i e s " W.L. P a t t e r s o n and R.F. Banker (Eds.), U.S. EPA, Report No.17090 DAN 10/77, 251pp., C i n c i n n a t i , Ohio, Oct. (1971). 39. Adams, C.E.,Jr. and E c k e n f e l d e r , W.W.,Jr. (Eds.), Process Design Techniques f o r I n d u s t r i a l Waste Treatment. AWARE, Inc., E n v i r o P r e s s , N a s h v i l l e , Tennessee, pp.247-275 (1974). 40. EPA Technology T r a n s f e r , "Process Design Manual f o r Up-gradi n g E x i s t i n g Wastewater Treatment P l a n t s " . U.S.EPA, C i n c i n n a t i , Ohio, pp.7-23 t o 7-38, Oct. (1974). 41. Chian, E.S.K. and DeWalle, F.B., " E v a l u a t i o n of Leachate Treatment, V o l . I I : B i o l o g i c a l and P h y s i c a l - C h e m i c a l Processes".' U.S. EPA, Report EPA-600/2-77-1866, pp.233-244, C i n c i n n a t i , Ohio, Nov. (1977). APPENDICES 89 APPENDIX I DESIGN- EQUATIONS FOR BIOLOGICAL SYSTEM , In t h i s study the s o l i d s d e t e n t i o n time, 9 C, and the food-to-microorganism r a t i o , F/M, were used as b a s i c d e sign para-meters , whereas 9 C was a l s o used as a treatment c o n t r o l parameter i n the a e r o b i c b i o l o g i c a l system. A l l design parameters used f o r the k i n e t i c s of b i o l o g i c a l growth are given i n M e t c a l f and (31) Eddy: ' These i n c l u d e : dS = KXS . dt K s+ S ( A ' dX/dt = y dSZ^t _ b ( B ) 1 YKS 9 C K s+ S - b (C) where dS/dt = r a t e o f ' s u b s t r a t e u t i l i z a t i o n , mass/volume-time K = maximum r a t e of waste u t i l i z a t i o n per u n i t weight of microorganisms, t i m e - 1 X = c o n c e n t r a t i o n of microorganisms, mass/volume S = s u b s t r a t e c o n c e n t r a t i o n , mass/volume K s = s u b s t r a t e c o n c e n t r a t i o n when dS/dt _ K mass/volume X 2 ' dX/dt = net growth r a t e of microorganisms, mass/volume-time Y = g r o w t h - y i e l d c o e f f i c i e n t , mass of microorganisms/ mass of s u b s t r a t e u t i l i z e d ("a" i n Reference 30) b = microorganism-decay or endogenous r e s p i r a t i o n c o e f f i c i e n t , t i m e ~ l ("k^" i n Reference 31) e c = X , time. dX/dt 90 For a complete-mix-no-recycle system, f i x i n g 9 C e s t a b l i s h e s X or mixed l i q u o r v o l a t i l e suspended s o l i d s , MLVSS, i n the r e a c t o r ; and AS = Q ( S 0 - S e) = Sp- S e , m A t V 9 C ( U ) y - y (Sp — S e) ( v . x ~ 1 + b e c ( E ) where Q = i n f l u e n t waste flow r a t e , volume/time V = volume of r e a c t o r , volume S Q= i n f l u e n t waste c o n c e n t r a t i o n , mass/volume S e= e f f l u e n t waste c o n c e n t r a t i o n , mass/volume. The minimum s o l i d s d e t e n t i o n time, ® C / m i n . / at which the micro-organisms are washed out or wasted from the system as f a s t as they can reproduce themselves, can be c a l c u l a t e d by s u b s t i t u t i n g S with S Q i n Eq.(C). That i s , 91 APPENDIX II PREDICTION OF OPERATIONAL SOLIDS DETENTION TIME AND MLVSS CONCENTRATIONS In order to predict the operational 9 C, k i n e t i c data from previous studies are l i s t e d i n the following table as a reference: Reference No. 10 25 26 31 Wastewater Type* L.L. L.L. D.L.L. D.S. Treatment Process* A.L. A.L. A.S. A.S. Parameter Basis COD BOD5 COD COD Influent COD, mg/1 17,500 48,000 360 NR Influent BOD5, mg/1 9 ,500 36 ,000 ,NR NR Y 0.40 0.33 0.59 0.67 b, d a y - 1 0.05 0. 0025 0.115 0.07 K, d a y - 1 0 .60 . 0.75 1. 8 5.6 K s, mg/1 175 21,400 182 22 e c / days (operational) 10 20-30 5-15 NR ec,min.' d a v s 5.3 6.5 NR 0.27 ©c/©c,min. 2 3-5 - -L.L. = L a n d f i l l leachate; D.S. = Domestic sewage; A.L. = Aerated lagoon; A.S. = Activated sludge; D.L.L. = Diluted l a n d f i l l leachate. NR = Not reported. For the purpose of prediction, assume S Q = COD = 1,800 mg/1, Y = 0.50, b = 0.05 day - 1 , K = 1.5 day - 1, and K s = 100-900 mg/1. Using Equation (F) i n Appendix I, we have @ K s = 100 mg/1, e C / m i n . = 1.5 days; @ K s = 900 mg/1, © c,min. = 2 - 2 days. 92 M e t c a l f & Eddy v ; suggested: e c = (2 to 20) x © c , m i n . In t h i s study, i f © c / e c , m i n . = 2 to 4, we get 3.0 6e c ^8.8. T h e r e f o r e , the p r e d i c t e d sludge age i n days i s 3^e c^10 ( f o r extremes of K s) . To p r e d i c t the MLVSS c o n c e n t r a t i o n s , a COD removal e f f i -c i e n c y of 90% i s assumed. That i s , S Q - S e = 1,800 x 0.90 = 1,600 mg/1. S u b s t i t u t i n g t h i s v alue as w e l l as the assumed Y and b value s i n t o Equation (E) i n Appendix I, we o b t a i n @ 0 C = 3 days, X = 696 mg/1; @ 6 C = 10 days, X = 533 mg/1. T h e r e f o r e , f o r s o l i d s d e t e n t i o n times of 3 to 10 days, the p r e d i c t e d steady s t a t e MLVSS c o n c e n t r a t i o n s are i n the range of 500 t o 700 mg/1. I 93 APPENDIX I I I AN EVALUATION ON THE ROLE OF CHEMICAL PRECIPITATION IN METAL REMOVAL DURING AEROBIC DIGESTION PROCESS (1) Required data taken from Table V I I I are l i s t e d i n the f o l l o w i n g t a b l e ( a l l i n mg/1): Parameter Cone. i n Leachate Feed Cone, i n S e t t l e d E f f . ( a v . ) Cone. i n Mixed L i q . ( a v . I norganic Carbon 150 80 200 A l k a l i n i t y as CaC03 520 355 NA T o t a l - P 13 .9** 0.52 13.9 Ortho-P 10* NA NA PH 6.3 8.4 8.4 Ca 550 180 545 Fe 20.2 0.89 19.5 Mn 4.10 0.05 3.80 Zn 1.17 0.10 1.16 Pb 0.045 0.003 0.047 Mg 39.2 36.8 36.2 * C o n c e n t r a t i o n a f t e r n u t r i e n t a d d i t i o n . ** Assumed value (ortho-P 9.2 mg/1). NA = Not analyzed. (2) The r e s u l t s of c a l c u l a t i o n and the comparison of i o n c o n c e n t r a t i o n products with s o l u b i l i t y products are shown i n the next t a b l e where C i = t o t a l c o n c e n t r a t i o n a v a i l a b l e i n lea c h a t e feed, mole/L ° — — Cf = Cc03_3> CP043 o r C 0 I0 c a l c u l a t e d from pH-dependent d i s t r i b u t i o n diagrams or equations wherever a p p l i c a b l e . (2) Metal of Concern Possible /Anion for P r e c i p i t a t i o n Formation c o T P04~~ OH" C ^ - ^ C f 2.5xl0~ 4 4.7xl0~ 8 2.5xl0~ 6 Ca 1.4xl0~ 2 K Sp = 4.8xl0~ 9 Q C a J t c o y = 3.5x10~6 K s p = ^ 10" 2 6 [ C a J^PO^ J = 6 . l x l 0 ~ 2 1 NA Fe 3.6xl0 - 4 NA K s p = 1.3xl0~ 2 2 (Fe][PO a 4]= 1 . 7 x l 0 _ 1 1 -39 K s p = 10 |FeJ[OH] = 5.6x10~ 2 1 Mn 7.5xl0~ 5 K s p = 5.0xl0~ 1 0 [Mn ]C C 03j = l - 9 x l 0 ~ 8 NA K s p = 1.6xl0~ 1 3 [MnJ[OHj<<Ksp Zn 1.8xl0~ 5 K Sp = 2 . 0 x l 0 _ 1 1 £ZnJ[C03j = 4.6xl0~ 9 -32 K s p = 10 CZnJS[P04]= 1 0 - 2 9 K s p = 10" 1 6 CznJ[OH]= l . l x l O " 1 6 Pb 2.2xl0~ 7 K Sp = 6.3xl0~ 1 4 I^P1DJ(C031 = 6. 3 x10 - 1 1 K s p = 7.9xl0" 4 3 [PbJ [P0 4 J = 2.3x10 J D NA Mg 1.6xl0~ 3 K Sp = 10" 5- 0 [ M g ] [ C 0 5 ] < K s p NA NA Notes: (a) Concentration products shown in table were calculated at pH 8.4. Calculations done at pH 6.3 indicated that only FeP0 4 and Fe(OH)3 can e x i s t as precipitates at pH 6.3. Therefore, i t i s possible that part of the 20.2 mg/1 Fe in leachate feed was present as part i c u l a t e s of FeP0 4 and Fe(OH)3. (b) Cf values for C O 3 were calculated from inorganic carbon concentration. (c) NA = Not applicable. (d) If a l k a l i n i t y = [ H C 6 3 J + 2 [ C 0 3 J , [ 0 0 3 ] = 4.4xl0~ 4 M @pH 8.4. (e) At pH 6.3: C f = 6.2xl0~ 7 for C O 3 , 3 . 2 x l 0 _ 1 1 for P0 4, 2.0xl0~ 8 for OH~. VD 0 95 \ (3) Remarks: The complexation of metals with both o r g a n i c s and i n o r g a n i c s as w e l l as of anions with v a r i o u s c a t i o n s was bound t o occur i n the complicated matrix of le a c h a t e s o l u t i o n , which l i m i t s the a v a i l a b i l i t y of f r e e i o n s f o r the formation of p r e c i p i t a t e s of concern. However, i t was f e l t t h a t as long as the c o n c e n t r a t i o n products are at l e a s t one or two orders of magnitude g r e a t e r than the s o l u b i l i t y p r o d u c t s , K Sp, the formation of p r e c i p i -t a t e s of i n t e r e s t would be q u i t e l i k e l y . APPENDIX IV DETERMINATION OF KINETIC PARAMETERS (1) Determination of Y and b (BODt; Basis) From Appendix I, Equation (B): A X / A t A S / A t _ . X X where A S _ S 0 - S p A t 0, 'c AX_ = Xe- -^X Q = Xg_ ( a s s u m i n g X q = 0) and AX/At _ _ 1 _ X © c A p l o t of AX/At v s . AS/At should t h e r e f o r e y i e l d a s t r a i g h t X X l i n e w ith slope Y and i n t e r c e p t -b. ©c X So s e AS/At (AS/At) /X (AX/At)/X=1/0 C days mg/1 mg/1 mg/1 mg/l/day d a y - 1 day - 1 2 490 940 28 456 0.93 0.500 3 560 1040 9 344 0.61 0.333 5 560 1040 10 206 0.37 0.200 7 480 1040 7 148 0.31 0 .143 7 400 940 8 133 0.33 0.143 10 360 940 8 93 0.26 0.100 The above data i s p l o t t e d i n F i g u r e A - l from which a l e a s t square f i t g i v e s : Y = 0.59 mgVSS/mgBOD5 b = 0.040 d a y - 1 . 0.5 0.4 ~ 0.3 o T3 3 X < X 0.2 97 y = 0.59X- 0 .040 . Y=0.59 mgVSS/mgB0D 5 b = 0.040day -I 0.2 0.4 0.6 AS/At 0.8 1.0 1.2 (mgB0D 5/mg VSS/day) FIGURE A - l : DETERMINATION OF Y AND b BASED ON BOD 5 DATA ~ 4 >» o T3 «o o co 3 £ co co > 2 E < 'co < o°o K = 4.5mg B0D 5/mg VSS/day K s= 99mg/ l y = 22X + 0.22 0.02 0.04 0.06 0.08 0.10 I / Se ( litres /mg) 0.12 0.14 FIGURE A - Z- DETERMINATION OF K AND K s BASED ON B0D 5 DATA APPENDIX IV (cont'd) (2) Determination of K and K g (BODc; Basis) From Appendix I, Equation (A): AS _ KXS e_ A t K s+ S e By r e a r r a n g i n g the above e q u a t i o n , we get: X = Kg (_!_, , 1 AS/At K v S e ; K X 1 A p l o t of A S y A t v s . —g— should y i e l d a s t r a i g h t l i n e with slope K s/K and i n t e r c e p t 1/K. ©c X S e AS/At 1/S e X/(AS/At) days mg/1 mg/1 mg/l/day (mg/1)- 1 day 2 490 28 456 0.036 1.07 3 560 9 344 0.111 1.63 5 560 10 206 0.100 2.72 7 480 7 148 0.143 3.24 .7 400 8 133 0.125 3.01 10 360 8 93 0 .125 3.87 The above data i s p l o t t e d i n F i g u r e A-2 from which a l e a s t squares f i t g i v e s : K = 4.5 mgBOD5/mgVSS/day K s = 99 mg/1. 99 APPENDIX IV (cont'd) (3) Determination of Y and b (COD Basis) AX/At = AS/At X X ©c X So s e AS/At (AS/At)/X (AX/At)/X=l/9 c days mg/1 mg/1 mg/1 mg/l/day d a y - 1 d a y l 2 490 1580 275 653 1.33 0.500 3 560 1760 215 515 0.92 0.333 5 560 1760 200 312 0.56 0.200 7 480 1760 175 226 0 .47 0.143 7 400 1580 170 201 0.50 0.143 10 360 1580 170 141 0.39 0.100 The above data i s p l o t t e d i n F i g u r e A-3. From t h i s graph i t i s o b t ained t h a t : Y = 0.42 mgVSS/mgCOD b = 0.056 d a y - 1 . 100 FIGURE A - 3 « DETERMINATION OF Y AND b BASED ON COD DATA 

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