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Biological-chemical treatment of landfill leachate Graham, David W. 1981

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BIOLOGICAL-CHEMICAL TREATMENT OF LANDFILL LEACHATE by David W. Graham B.A.Sc, University of B r i t i s h Columbia, 1977 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE THE FACULTY OF GRADUATE STUDIES (The Department of C i v i l Engineering) We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA February 1981 ( c ) David W. Graham, 1981 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Li b r a r y s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s t h e s i s for scholarly purposes may be granted by the Head of my Department or by h i s representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s thesis f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of C i v i l Engineering The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, B.C. V6T 1W5 DATE FEgetiA/Zr' Z 1 4 3 1 ABSTRACT Leachate i s an e f f l u e n t generated v i a the percol a t i o n of surface and groundwater through sanitary l a n d f i l l s . Depending on l o c a l conditions, large volumes of high strength and p o t e n t i a l l y t o x i c leachate can be prod-uced r e s u l t i n g i n s i g n i f i c a n t d e t e r i o r a t i o n of receiving water q u a l i t y . Leachate c o l l e c t i o n and treatment systems are currently being developed. The purpose of t h i s study was to determine the t r e a t a b i l i t y of high-strength leachate using a s e r i e s biological-chemical treatment system; that i s , aerobic b i o l o g i c a l degradation i n a f i l l and draw reactor followed by lime p r e c i p i t a t i o n i n a separate v e s s e l . The system proved to be highly e f f i c i e n t i n t r e a t i n g high-strength leachates both i n terms of organics and heavy metals removal. Using a series of treatment.combinations on a leachate with a COD of greater than 19,000 mg/SL and high metal concentrations, a l l the B r i t i s h Columbia 'AA'1 Level p o l l u t i o n control guidelines could be met with the exception of pH and manganese. Assessed on operating s t a b i l i t y and treatment e f f i c i e n c y , the two most favourable treatment configurations were; an aerobic b i o l o g i c a l u n i t of 12 day mean c e l l residence time (MCRT), with an addition of 800 mg/£ Ca (OH) f o r p o l i s h i n g , and a b i o l o g i c a l u n i t of 15 days MCRT, with an addition of 450 mg/£ Ca(OH) . The biotreatment system was very e f f e c t i v e i n the removal qf organics. Soluble COD removals ranged from 97.2% to 98.6% over a temperature range of 5° to 24°C and mean c e l l residence times of 9 days to 25 days. Soluble BOD,, removals ranged from 99.5% to 99.9%. Trace metals were also removed e f f e c t i v e l y . Metal removals were greater than 96% f o r Fe, Mn, and Zn, better than 80% f o r Ca, better than 70% f o r Pb, between 70 and 80% for Cr and Ni, and 40% f o r Magnesium. i i i Temperature reductions d i d not s i g n i f i c a n t l y influence the bi o -treatment removal e f f i c i e n c i e s ; however, some stress was noted i n the bi o -l o g i c a l systems at 5°C. Decreasing s e t t l e a b i l i t y and excess foaming was prevalent e s p e c i a l l y i n the lower MCRT u n i t s . Unit f a i l u r e was observed i n the 6 day MCRT digester when the temperature was reduced from 9° to 5°C. Further t e s t s on the cold temperature operation of b i o l o g i c a l units i n d i c a t -ed that ambient temperature a c c l i m a t i z a t i o n may be required, p r i o r to cold temperature operation. Lime p r e c i p i t a t i o n performed well on most e f f l u e n t s over the range of dosages tested. Unfortunately, the dosages required were quite high, p r i n c i p l y because of the very high sample a l k a l i n i t i e s . For a lime dosage of 900 mq/k Ca(OH) , at 25% reduction i n COD was obtained on a sample with an i n i t i a l COD of 551 mq/k and suspended s o l i d s l e s s than 25 mq/k. Metal removals were s u b s t a n t i a l l y more impressive. At a pH of 11.5 (900 mq/k Ca(0H) 2), t y p i c a l reductions were >99% f o r Fe, 91% for 2;n, 83% for Mn, 91% fo r Mg, and 73% f o r Ca. Other metals were i n i t i a l l y at very low concen-t r a t i o n s and as a r e s u l t , were not monitored during the lime p r e c i p i t a t i o n studies. The p r i n c i p l e removal mechanisms f o r organic materials were adsorp-t i o n and entrapment. A reasonable c o r r e l a t i o n was developed between i n i t i a l COD and a l k a l i n i t y , and the quantity of Ca(OH) required to achieve a prescribed treatment l e v e l . Metals were removed by chemical p r e c i p i t a -t i o n , and to a small extent, adsorption and entrapment. The removal o f metals was extremely dependent upon the s o l u b i l i z a t i o n pH of the respective metal hydroxides. i v TABLE OF CONTENTS Page ABSTRACT i - 1 LIST OF TABLES v i LIST OF FIGURES v i l ACKNOWLEDGEMENTS v i i i CHAPTER 1 INTRODUCTION 1 2 BACKGROUND 4 2.1 Introduction 4 2.2 L i t e r a t u r e Review of Previous Treatment E f f o r t s 4 2.3 General Conclusions 9 2.4 Experimental Format and Goals 11 2.5 Temperature E f f e c t s on B i o l o g i c a l Growth 12 3 EXPERIMENTAL METHODS AND MATERIALS 15 3.1 Design of the Treatment System 15 "3.2 Leachate Source and C h a r a c t e r i s t i c s . . . . . . 17 3.3 Operating Variables i n the B i o l o g i c a l Units 19 3.4 The Temperature Reduction Phase 21 3.5 The Cold Temperature Phase 27 3.6 The Lime-Polishing Phase 28 4 RESULTS AND DISCUSSION 3 2 4.1 First-Stage B i o l o g i c a l Treatment 32 4.2 Lime-Precipitation P o l i s h i n g 48 4.3 Combined Biological-Chemical Treatment 63 5 CONCLUSIONS AND RECOMMENDATIONS 6 7 5.1 Conclusions 67 5.2 Recommendations f or Future Studies 7 0 REFERENCES • • • 7 2 V TABLE OF CONTENTS (continued) Page APPENDICES I EFFECT OF COLD TEMPERATURE ON BIODEGRADATION 75 II BIOLOGICAL SOLIDS'LEVELS THROUGHOUT THE OPERATING SCHEDULE 76 III BIOLOGICAL TREATMENT DESIGN EQUATIONS . . . 79 IV BIOLOGICAL KINETIC PARAMETERS - . • 81 V THE MINIMUM CTP SOLIDS DETENTION TIME 88 VI RELEVANT SOLUBILITY PRODUCTS OF CATIONIC HEAVY METAL OXIDES AND HYDROXIDES 89 VII LIME PRECIPITATION REMOVAL DATA 90 v i LIST OF TABLES Table No. T i t l e Page 1 Range of Composition of Leachates 2 2 A Summary of P o t e n t i a l Treatment Methods 10 3 Physical C h a r a c t e r i s t i c s of Laboratory Lysimeters 18 4 Composition of Leachate Feed Used During This Study 20 5 Reactor I d e n t i f i c a t i o n 23 6 Leachate Dosage Rates 24 7 The Testing Schedule 27 8 B i o l o g i c a l Reactor Operating Conditions 33 9 B i o l o g i c a l Reactor Mixed Liquor Metal Concentrations 37 10 B i o l o g i c a l Reactor S e t t l i n g Conditions 39 11 E f f e c t of Temperature, S e t t l i n g Rate, and MCRT on the Removal of Oxygen Demanding Material 41 12 Summary of Metal Removal E f f i c i e n c i e s During the TRP 45 13 Summary of Metal Removal E f f i c i e n c i e s During the CTP 46 14 Second-Stage Influent C h a r a c t e r i s t i c s 49 15 Combined Treatment Removal E f f i c i e n c i e s 66 16 K i n e t i c Parameters, Y and b - BOD Basis 82 5 17 K i n e t i c Parameters, K and K - BOD_ Basis 84 s 5 18 K i n e t i c Parameters - COD Basis 86 v i i LIST OF FIGURES Figure No. Page 1 B i o l o g i c a l Treatment Unit 16 2 pH of Mixed Liquors vs. Mixed'Liquor Dissolved Oxygen 22 3 COD Removal vs. Organic Loading Rate During CTP 43 4 Lime Additions and COD Removals vs. pH^. ., A f t e r Lime , -,. . f i n a l r-T Additions =>1 5 Lime Required to Reduce COD by 20% vs. the Influent COD . . . . 52 6 Lime Required to Reduce COD by 20% vs. the Influent A l k a l i n i t y 54 7 Lime Additions vs. pH,.. . A f t e r Lime Additions 55 f i n a l 8 Lime Additions and Iron Removals vs. pH =. n A f t e r , • f i n a l rr-7 Lime Additions 9 Lime Additions and Zinc Removals vs. pH^ .. n A f t e r ,-,. . f i n a l r D Lime Additions ->° 10 Lime Additions and Manganese Removals vs. pH,.. ., A f t e r -,,. . f i n a l rQ Lime Additions ->y 11 Lime Additions and Magnesium Removals vs. pH_. , A f t e r - -, • . f i n a l C n Lime Additions o u 12 Lime Additions and Calcium Removals vs. pH . n A f t e r f i n a l c i Lime Additions toJ-A TSS During the TRP . . 76 B VSS During the TRP • 77 C Suspended Solids During the CTP 78 D Determination of Y and b Based on BOD,. Data 8 3 E Determination of K and K Based on BOD,. Data 8 5 s 5 F Determination of Y and b Based on COD Data 8 7 v i i i ACKNOWLEDGEMENTS The author wishes to thank Dr. D.S. Mavinic for h i s patience and support during the preparation of t h i s t h e s i s . He also wishes to thank Dr. W.K. Oldham, Dr. R.D. Cameron, and Mrs. E.C. MacDonald f o r t h e i r assistance i n various aspects of the reseach program. F i n a n c i a l support for t h i s research was provided by NSERC, the National Science and Engineering Research Council. 1. CHAPTER 1 INTRODUCTION The continuing use of sanitary l a n d f i l l s f o r disposing of s o l i d wastes and the subsequent p e r c o l a t i o n of p r e c i p i t a t i o n and groundwater through these f i l l s generates an effluent, known as leachate. Under c e r t a i n environmental conditions, large volumes of high strength, and sometimes t o x i c , leachates can be produced. As a r e s u l t of the p o t e n t i a l f o r serious d e t e r i o r a t i o n of r e c e i v i n g water q u a l i t y , l a n d f i l l leachates are now being given considerable a t t e n t i o n . The magnitude of the problems associated with the leachates generated i s dependent on a number of f a c t o r s . These include the amount and composi-t i o n of the refuse, the s i t e hydrology, the i n f i l t r a t i o n rates, the season, the climate, and the d i l u t i o n a v a i l a b l e i n the rec e i v i n g waters. A range of t y p i c a l leachate c h a r a c t e r i s t i c s i s presented i n TABLE 1. The age of the l a n d f i l l i s also s i g n i f i c a n t due to the changes i n the physical and chemical structure of the l a n d f i l l over time. The gradual degradation of the accumulated s o l i d waste i s a slow and highly complex process. I n i t i a l l y , aerobic conditions are prevalent; t h i s r e s u l t s i n the production of CO^ gas and low molecular weight v o l a t i l e acids. As a r e s u l t , the pH of the act i v e waters drops and i t s extraction c a p a b i l i t i e s increase (1). With the enhanced ex t r a c t i v e c a p a b i l i t y , the "leachate" leaches out compounds from the decaying wastes r e s u l t i n g i n a l i q u i d waste as varied as the refuse i t s e l f . The decomposition of the s o l i d waste i s an extremely slow process. This factor i s e s s e n t i a l l y what makes the l a n d f i l l leachate problem so s i g n i f i c a n t . Leachate generation-is.continuous and independent of the operation of the l a n d f i l l i t s e l f . Leachates will.continue to be TABLE 1 3 RANGE OF COMPOSITION OF LEACHATES Parameter Range of Values or Concentrations* ( L a n d f i l l s or Test Lysimeters) BODc 9-55,000 o COD 0-89,52 0 TOC 256-28,00 0 pH 3.7-8.5 Total Solids 0-59,20 0 Tota l Suspended Solids 10- 1,450 Total Dissolved Solids 600-45,000 A c i d i t y 0- 9,560 A l k a l i n i t y 0-20,900 Aluminum 0-122 Arsenic 0-11.6 Barium 0- 5.4 Calcium 5- 7,200 Cadmium 0-17.0 Chloride 4.7- 2,800 Chromium 0-33.4 Copper 0-10 Iron 0- 5,500 Lead 0- 5.0 Magnesium 17-15,600 Manganese 0.06- 1,400 Mercury 0-0.064 Nitrogen - t o t a l 0- 2,406 - NH 3 0- 1,106 Nick e l 0.01-0.80 Phosphorus - t o t a l 0- 154 Potassium 28- 3,770 Sodium 0- 7,700 Sulphates 1- 1,826 Zinc 0- 1,000 • a l l values except for pH are i n mg/£ 3. generated 20 to 30 years a f t e r the l a n d f i l l operation has been terminated. More and more cases have been documented where leachates have been an on-going problem, thus, causing serious health and environmental consequences ( 3 , 4 , 5 , 6 ) . There are a number of design precautions which can be performed to control or minimize the generation of leachate at the l a n d f i l l . They include d i v e r t i n g surface water away from the s i t e , l i n i n g the l a n d f i l l to prevent contact between the refuse and groundwater, and generally more c a r e f u l i n i t i a l s i t e s e l e c t i o n . In a r i d and semi-arid climates, where p r e c i p i t a t i o n i s minimal, s e a l i n g and sloping the surface of the l a n d f i l l , to reduce 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 , has been used very e f f e c t i v e l y . Unfortunately, most of these precautions can only be used on newly designed l a n d f i l l s i t e s . There are many old l a n d f i l l s , s t i l l generating leachates which must be handled and n e u t r a l i z e d . The problem of handling leachates generated from ol d l a n d f i l l s i s a topic of much current research; however, very few adequate solutions have been devised. This t h e s i s ideals .with treatment, .of. the l a n d f i l l leachates generated. There have been numerous, previous studies on leachate treatment, but there are s t i l l unanswered questions. The purpose of t h i s study, therefore, was to attempt to answer some of these questions and to suggest and evaluate an e f f e c t i v e means (in terms of p r a c t i c a l i t y and performance) of t r e a t i n g high strength, sanitary, l a n d f i l l leachates. 4. CHAPTER 2 BACKGROUND 2.1 Introduction The purpose of t h i s research work was to develop an e f f e c t i v e method of t r e a t i n g high-strength sanitary l a n d f i l l , leachates under varying operating conditions. Before t h i s could be done, a complete survey of relevant l i t e r a t u r e had to be undertaken to determine the most appropriate methods to examine. Leachate treatment has been a major concern over the l a s t ten years. Many in v e s t i g a t i o n s have already .been undertaken, yet none has produced a treatment method considered to be t o t a l l y s a t i s f a c t o r y . Methods such as bi o -l o g i c a l treatment, physical-chemical treatment, and leachate recycle have shown promise but each method has i t s own l i m i t a t i o n s and re l a t e d problems. Because of t h i s , i t was concluded that some combination of the above methods might be the most, e f f e c t i v e method of treatment, both i n terms of a p p l i c a -b i l i t y and treatment e f f i c i e n c y . P r i o r to the study, c e r t a i n treatment goals were established. The B r i t i s h Columbia P o l l u t i o n Control Board 'AA' l e v e l guidelines (PCB) were adopted as the treatment c r i t e r i a (7). Although c r i t e r i a l i s t e d i n the guidelines i s not r i g i d l y applied, i t i s a good measure of treatment eff e c t i v e n e s s . 2.2 L i t e r a t u r e Review of Previous Treatment E f f o r t s (a) B i o l o g i c a l Treatment - Aerobic b i o l o g i c a l treatment systems have been used very s u c c e s s f u l l y i n t r e a t i n g high strength l a n d f i l l leachates. Numerous laboratory studies i n c l u d i n g those done by Boyle and Ham (8), Chian and DeWalle (2,9), Cook and Force (10), Lee (I), and Uloth and Mavinic (11) 5. have reported COD removals of greater than 90%, at detention times from 5 to 20 days, for leachates ranging from 1,700 to 57,900 mg/& COD. Unfortunately, few attempts have been made at t r e a t i n g leachates by aerobic systems i n the f i e l d . Steiner et a l . (12) unsuccessfully t r i e d to operate a lagoon system i n 1977. They attributed, the f a i l u r e to ammonia t o x i c i t y ; however, i t seems more l i k e l y that the problems were r e l a t e d to the cold temperature acclimat-i z a t i o n conditions. In the l i t e r a t u r e , there i s very l i t t l e s aid about the e f f e c t s of temperature on the operation of aerobic b i o l o g i c a l leachate treatment systems. The fate of heavy metals i n aerobic b i o l o g i c a l systems has been examined i n a number of studies (1,9,10,11). At. moderate metal l e v e l s , k i n e t i c parameters have indicated some metal i n h i b i t i o n to b i o l o g i c a l growth. In general, however, trace metal concentrations have shown l i t t l e s i g n i f i c a n t adverse e f f e c t s on the o v e r a l l operation of aerobic b i o l o g i c a l treatment systems. Metal reductions have ranged from very good to very poor. Uloth and Mavinic (11) indicated that for a detention time of 20 days and i n i t i a l metal concentrations as high as 1,260 mq/SL (Fe) , removals of greater than 96.8% could be achieved f o r A l , Cd, Ca, Cu, Fe, Mn, and Zn. Pb, Ni, and Mg achieved reductions between 68.5% and 83.6%. Potassium (K) concentrations were not s i g n i f i c a n t l y reduced by b i o l o g i c a l treatment. S i m i l a r l y , Chian and DeWalle (9), with i n i t i a l metal concentrations as high as 2,125 mg/Jt (Fe) and a 30 day detention time, achieved Fe, Ca, and Zn removals of 99.4% or greater. They also achieved 81.9% Mg removal; however, they found the removal of Na and K to be n e g l i g i b l e . Other research has indicated that the optimum nutrient requirements f o r an aerated lagoon, t r e a t i n g leachates, i s 100:3:1 (BOD :N:P), rather 6. than the conventional r a t i o 100:5:1 (13). There have been many, studies performed on the anerobic treatment of l a n d f i l l leachates (3,8,9,14). COD removals of between 92% and 97% have been achieved, using, detention times from 7 to 27 days, for leachates ranging from 5,000 mg/£ to 62,000 mg/£ COD. Poorman and Cameron (14) found no adverse e f f e c t s on the anaerobic degradation process as a r e s u l t of high heavy metal concentrations. Boyle and Ham (8) found that anaerobic treatment produced greater than 90% BOD removal, providing that the temperature was between 23°C and 30°C. Treatment was s i g n i f i c a n t l y i n h i b i t e d by temperatures lower than 23°C, when the detention time was 30 days. F a i l u r e occurred at deten-t i o n times le s s than 20 days. (b) Chemical Treatment - The p r i n c i p a l chemical treatment methods include p r e c i p i t a t i o n , coagulation, and oxidation. A l l three mechanisms have been only marginally successful i n leachate treatment i n previous studies. The two most common chemicals used as p r e c i p i t a n t s are lime and sodium sulphide. Ho et a l . (15) found that better r e s u l t s were obtained with lime, although neither method performed well.enough by i t s e l f to be considered an e f f e c t i v e treatment method. Bjorkman and Mavinic (16) showed that Fe, suspended s o l i d s , and colour were reduced very e f f e c t i v e l y by lime p r e c i p i t a t i o n . P, Zn, Cd, K, and Ca also showed some reductions; however, organics removals were poor, with a COD reduction of only 0% to 26% being achieved with lime dosages as high as 2,760 mg/Z Ca(OH) 2 (16). Sludge production rates were found to be very high (1, 15, 16). The common chemical coagulents are alum, f e r r i c c h l o r i d e , ferrous sulphate, and c e r t a i n polymers. Results achieved with these chemicals were s i m i l a r to those obtained with lime and sodium sulphide (15,16). Fe, colour, and suspended s o l i d s were removed e f f e c t i v e l y , while the removal of other 7. metals and organics was minimal. Chemical dosage rates and the sludge volumes produced were p r o h i b i t i v e l y high. Chemical oxidation can be performed using chlorine, calcium hypo-c h l o r i t e , potassium permanganate, and ozone. The most impressive r e s u l t s were obtained using ozone. . COD removals ranging from 22% to 48% were achieved under v a r i a b l e ozone contact times (2). Bjorkman and Mavinic (16) showed the Fe and colour were also e f f e c t i v e l y removed; however, ozone dosages were found to be high (130 mg/l ozone). Lime and ozone together, provided some improvements i n e f f l u e n t metal concentrations; however, f or the best value (lowest achieved) e f f l u e n t s , lime dosages were greater than 2,000 rag/H Ca(0H) 2 and ozone dosages were greater than 97 mg/£ ozone. (c) Physical Treatment - The p r i n c i p a l p h y s i c a l treatment methods include activated carbon adsorption, reverse osmosis and ion exchange. Activated carbon adsorption, with batch and column systems, have achieved anywhere from 34% to 85% COD removals, with dosages between 10,000 mg/i and 160,000 mg/£ carbon (2). The removals of metals are not well documented. Because of high organic loadings, low adsorptive c a p a c i t i e s , and the presence of suspended s o l i d s i n the raw leachates, regular f o u l i n g of the carbon columns have been observed (9). Indications are that the activated carbon process i s currently uneconomical f o r raw leachate treatment. Reverse osmosis of raw leachates was quite successful i n t r e a t i n g organics. Chian and DeWalle (2) found COD reductions of between 56% and 89%, f o r a high strength leachate of 53,300 mg/l COD. Removal of t o t a l s o l i d s was up to 99% when i n f l u e n t p r e f i l t r a t i o n was performed. Organic removals were greatly improved when the pH of the raw leachate was increased. Like activated carbon, reverse osmosis units were subject to membrane f o u l i n g , 8. when the suspended s o l i d s l e v e l s were higher. There i s no documentation of the metal removal effectiveness of reverse osmosis u n i t s . The use of ion exchange processes f o r raw leachate treatment was considered only f o r the removal of ammonia i n low strength leachates (9). I t was found to be a very i n e f f e c t i v e means of ammonia removal, due to the presence of i n t e r f e r i n g substances which compete for bonding s i t e s . Organic removal was not examined but was believed to be very low. (d) Combined Treatment - From -the foregoing i t can be assumed that no single system can completely s a t i s f y a l l treatment requirements. Com-bined treatment i s therefore considered necessary f o r achieving e f f e c t i v e leachate treatment. Chian and DeWalle (2,9) present a survey of treatment combinations that have been t r i e d . The combinations can be separated i n t o three cata-gories; aerobic b i o l o g i c a l treatment with p o l i s h i n g , anaerobic b i o l o g i c a l with p o l i s h i n g , and activated carbon adsorption, with some sort of pre-treatment. Activated carbon, ion exchange, ozonation, and reverse osmosis have been employed as aerobic treatment p o l i s h i n g steps. In terms of organic removal, reverse osmosis was the most e f f e c t i v e (85% to 97% COD removal). Because of membrane - s o l i d s f o u l i n g , sand f i l t r a t i o n or chemical p r e c i p i t a -t i o n was required p r i o r to the reverse osmosis u n i t . Reverse osmosis was followed i n effectiveness by activated carbon (86% COD removal), ion exchange using strong base ion exchange resins (82% to 85% COD removal), and ozonation (37% to 48% COD removal) (9). The removal of trace metals by the p o l i s h i n g steps i s not well documented. With activated carbon, Lee (1) indicated that 99% removal of Fe was possible; however, boron l e v e l s showed no sign of improvement. There 9. was no metal removal information a v a i l a b l e on the other treatment methods. Anaerobic b i o l o g i c a l treatment has been combined with activated carbon, reverse osmosis, and lime p r e c i p i t a t i o n . As with aerobic bio-treated e f f l u e n t s , reverse osmosis provided the best organics removal (98% removal with an i n i t i a l GOD.of 900 mg/l). Activated carbon provided a 50% COD removal from an e f f l u e n t with.a COD of 932 mg/£ (2) . Ho et a l . (15) achieved only a 7.7% COD removal, using lime p o l i s h i n g ; however, they d i d achieve complete Fe and colour removal, and good suspended s o l i d s removal. They concluded that the combination of lime p o l i s h i n g and b i o l o g i c a l t r e a t -ment was promising. Lime addition.and alum addition have been used as preliminary steps to activated carbon adsorption. For an i n i t i a l COD of 3,290 mg/l, activated carbon, with lime pretreatment, achieved 81% COD removal (10). Van F l e e t et a l . (17) found that for an i n i t i a l COD of 2,000 mg/£, activated carbon column treatment of alumrpretreated leachate achieved a 94% COD removal. Both methods achieved e f f e c t i v e suspended s o l i d s and colour removals; however, trace metals were not mentioned. 2.3 General Conclusions TABLE 2 presents a summary of the major p o t e n t i a l treatment methods. Af t e r an evaluation of previous work performed at U.B.C. and elsewhere, i t was decided that two p a r t i c u l a r systems were quite promising: a two-stage b i o l o g i c a l system and a two-stage aerobic b i o l o g i c a l - l i m e p r e c i p i t a t i o n system. When considering sanitary l a n d f i l l leachates highly v a r i a b l e nature, the most f l e x i b l e system would probably be the most e f f e c t i v e . The chemical p r e c i p i t a t i o n system would appear to be the more operationally f l e x i b l e . I t i s also well suited to being combined with aerobic b i o l o g i c a l treatment. 10. TABLE 2 A SUMMARY OF THE POTENTIAL TREATMENT METHODS Method Organics Removal Metals Removal Comments Aerobic B i o l o g i c a l Very Good Good to Very Good - I f organics are bio-degradable, organics removal i s excellent -Not good on re f r a c t o r y organics. - S e t t l i n g and sludge d i s -disposal are serious problem areas. Anaerobic B i o l o g i c a l Good to Very Good Good to Very Good -Same as above except required t i g h t e r opera-t i n g c o n t r o l . - P o s s i b i l i t y of energy production from gases produced. -Activated Carbon Adsorption Good Not well known for Leachates -Most e f f e c t i v e on ref r a c t o r y organics re-moval. -Carbon f o u l i n g can be a problem. Activated carbon adsorption i s very expensive. Lime P r e c i p i t a t i o n Poor Good to Very Good -Not e f f e c t i v e at r e -moval of organics, although removal i s better on refr a c t o r y organics than biodegrad-able organics. Metals and suspended s o l i d s r e -removal i s very good. -Lime i s r e a d i l y a v a i l -able and inexpensive i f dosages can be minimized -High sludge production and subsequent disposal might be a problem. 11 . Aerobic b i o l o g i c a l treatment would e f f e c t i v e l y reduce the organics and most metals; the lime treatment would then remove the r e s i d u a l metals, some re f r a c t o r y organics, and excess suspended s o l i d s and colour from the b i o l o -g i c a l e f f l u e n t s . Because t h i s treatment combination has not been previously examined i n d e t a i l under low. operating temperatures, t h i s study was i n s t i g a t e d to evaluate t h i s treatment combination. 2.4 Experimental Format and Goals The operating v a r i a b l e s that were c o n t r o l l e d i n the aerobic b i o l o g i c a l u nits included temperature, aeration rate, s o l i d s detention time and nutrient l e v e l s . In the p r e c i p i t a t i o n u n i t s , the chemical dosage rate was c o n t r o l l e d . Lime was chosen as the chemical f o r p o l i s h i n g because of i t s r e l a t i v e l y low cost, i t s a v a i l a b i l i t y , and i t s effectiveness i n previously tested treatment systems. The key parameters i n the system were temperature, s o l i d s detention time, and lime dosage rate. For each temperature selected, the b i o l o g i c a l systems were operated at a serie s of s o l i d s detention times. Lime dosage rates were varied according to the ph y s i c a l c h a r a c t e r i s t i c s of the f i r s t stage e f f l u e n t s , so as to optimize the system removal e f f i c i e n c i e s . C h a r a c t e r i s t i c s evaluated included BOD , COD, suspended s o l i d s and selected 5 metal concentrations. Although i t i s recognized that t h i s optimization procedure would only be of value f o r the leachate used i n t h i s study, i t does give some idea of the detention times and the lime dosages required f o r a leachate of comparable strength. I t also indicates whether t h i s type of system can operate over a wide range of temperatures and how temperature a f f e c t s such important para-meters as s e t t l i n g , system s t a b i l i t y , and sludge morphology. The study was c a r r i e d out i n three phases. The "temperature reduction 12. phase" (or TRP) was designed to acclimatize the microbial population to l a n d f i l l leachates at room temperature, and then to reduce the temperature downward, step by step, to a minimum temperature of 5°C. At each temperature step, f u l l e f f l u e n t c h a r a c t e r i z a t i o n was c a r r i e d out. The "cold temperature phase" (or CTP). was designed to observe more completely, the operation of the bio-system under the coldest p r a c t i c a l temperature conditions. Throughout the TRP and the CTP, s e t t l e d and f i l t e r e d e f f l u e n t s were stored f or use i n the l i m e - p r e c i p i t a t i o n u n i t . The " l i m e - p r e c i p i t a t i o n phase" (or LPP) was i n i t i a t e d to observe and evaluate the' effectiveness and dosage requirements of lime-polishing as a means of t r e a t i n g aerobic b i o l o g i c a l e f f l u e n t s . The l e v e l of t e s t i n g i n the LPP was determined by the q u a l i t y of the incoming f i r s t - s t a g e e f f l u e n t s (7). 2.5 Temperature E f f e c t s on B i o l o g i c a l Growth ever since b i o l o g i c a l waste treatment methods were first.attempted; however, only recently has any r e a l progress been made on the subject. Previously, the Streeter-Phelps empirical modification of the Arrhenius law was used to define the e f f e c t of temperature on the reaction rate constants involved i n b i o l o g i c a l treatment. Recent work by Novak (18) and Friedman and Schroeder (19) has shown that the Streeter-Phelps modification i s r e a l l y of l i m i t e d value when p r e d i c t i n g such temperature e f f e c t s . The modified Arrhenius equation can be written as follows (20): The e f f e c t of temperature on bio-synthesis has been of great concern n (T-20) (1) where k the unknown rate constant of temperature T °C. T k 20 the known rate constant at 20°C 8 = the temperature a c t i v i t y c o e f f i c i e n t . The l i m i t a t i o n s l i e i n the f a c t that the temperature a c t i v i t y c o e f f i c i e n t , 0', i s dependent upon many factors and therefore, cannot be assumed to be constant. I t has been found that 0 varies, with the temperature range, the substrate concentration, the food to micro-organism r a t i o , the number of t e s t temperatures employed, the type of substrate, and the method of chemical analysis (18). As a r e s u l t , to give a true representation of the tempera-ture-substrate e f f e c t s , 0 must be a multi-rvariable function. Novak suggested that the growth rate k, for a given organism and substrate, should follow a general equation of the form k = £ (composition) . f (temperature) (2) Proper evaluation of the two functions would then produce an equation that truly• r e f l e c t s , the i n t e r r e l a t i o n s h i p of temperature and substrate. Another l i m i t a t i o n of the Arrhenius modification i s that i t only accounts f o r temperature e f f e c t s on the growth rate. The temperature e f f e c t s on the other constant, k , i s not accounted for at a l l . Since k modifies the s s s p e c i f i c u t i l i z a t i o n rate as defined below, s 3 where U = the s p e c i f i c u t i l i z a t i o n rate, M/L T k = the growth rate, T S = the substrate concentration, M/L"^  k = the substrate concentration when the rate s 3 of substrate uptake = 1/2 k, M/L i t would be s i g n i f i c a n t i f k^, along with k, was found to vary with tempera-ture . For aerobic biosynthesis, Novak (18) found that, as temperature was 14. increased, both k and k increased l o g a r i t h m i c a l l y . Based on the Novak s r e s u l t s i t would appear that a comparable temperature.function f o r k , s s i m i l a r to Equation (1) , may be appropriate; however, more s p e c i f i c research to v e r i f y t h i s i s required. Because leachates are highly v a r i a b l e , both i n terms of strength and composition, the interdependence of substrate and temperature i s c r i t i c a l l y important when considering the possible e f f e c t s of temperature on the b i o -degradation of l a n d f i l l leachates. Although there i s i n s u f f i c i e n t data from t h i s study to f u l l y evaluate, both k and k^, a subsequent manuscript with Zapf-GiTje (21) , i n conjunction with t h i s research, should provide a more complete evaluation of the temperature k i n e t i c s and leachate bio-synthesis. A short summary of the s p e c i f i c e f f e c t s of cold temperatures on biodegradation i s presented i n Appendix I. CHAPTER 3 EXPERIMENTAL METHODS AND MATERIALS 3.1 Design of. the Treatment System (a) The B i o l o g i c a l Digesters.- Since t h i s research was an extension of on-going work at U.B.C, the treatment system design was derived from those previously used by the Environmental Engineering Group. The f i r s t -stage b i o l o g i c a l units were four, 1 0 - l i t r e capacity glass b o t t l e s . The bottom of each b o t t l e was removed and the necks were f i t t e d with large rubber stoppers secured i n place by heavy s t a i n l e s s s t e e l wires. Holes were bored through the stoppers and porous glass, coarse bubble a i r d i f f u s e r s were f i t t e d i n the bottom of each unit.: O i l - f r e e air.was supplied by the laboratory compressed a i r system at a rate c o n t r o l l e d by adjustable clamps placed on the a i r l i n e to each u n i t . Though the d i f f u s i n g a i r bubbles created some.turbulence, mechanical surface mixers were also employed to ensure complete mixing. The a i r flow rates and the mechanical s t i r r i n g speeds were adjusted to maintain aerobic conditions throughout the digesters, while minimizing foaming. Only 5 l i t r e s of mixed l i q u o r were maintained (as another precaution against foaming), thus allowing approximately 7 inches (18 cm) of freeboard i n each u n i t . A schematic diagram of a t y p i c a l digester i s presented i n FIGURE 1. (b) Temperature Control - The system was i n i t i a l l y i n s t a l l e d i n the main section of the laboratory, where there are no temperature c o n t r o l s . As a r e s u l t , the start-up was performed at room temperature (between 22°C and 25°C) . When i t was time to reduce the system temperature, the units were transferred to a temperature c o n t r o l l e d room. A l l t e s t i n g at 16°C, 9°C, and 5°C was performed therein. 16. E l e c t r i c Motor P o r o u s G l a s s A i r D i f f u s e r P l a s t i c Tubing To o ther Uni ts St i r r ing Rod 5 L i t res R u b b e r Stopper W i r e B r a c i n g A d j u s t a b l e C l a m p Air f rom co m pre s s e d a i r s u p p l y FIGURE 1: B i o l o g i c a l Treatment Unit (11) (c) E f f l u e n t Storage - While the digesters were operated, f i r s t - s t a g e e f f l u e n t s were c o l l e c t e d , i d e n t i f i e d and l a b e l l e d i n accordance with tempera-ture, sludge age, and degree of s e t t l i n g , and stored at 4°C for second-stage treatment. To maintain a uniform f i r s t - s t a g e e f f l u e n t sample, no second-stage te s t s were performed u n t i l there was s u f f i c i e n t sample to do a complete set of l i m e - p r e c i p i t a t i o n experiments. (d) Lime-Precipitation Testing Procedure - Although there are a number of chemical combinations commonly r e f e r r e d to as lime, f o r the purpose of t h i s paper, lime was defined as Ca(OU)^. The l i m e - p r e c i p i t a t i o n u n i t processes were performed on two standard six-paddle j ar t e s t i n g units (as manufactured by Phipps and B i r d ) . Since the stored f i r s t - s t a g e e f f l u e n t volumes were i n short supply (due to the l i m i t e d quantities of raw leachate a v a i l a b l e ) , 600 ml. beakers were chosen as the j a r t e s t containers. The lime was added as a s l u r r y at concentrations calculated to ensure that the f i n a l volumes i n the j a r t e s t beakers were approximately constant. 3.2 Leachate Source and C h a r a c t e r i s t i c s The leachate produced by four lysimeters located at the Uni v e r s i t y of B r i t i s h Columbia, was used as the f i r s t - s t a g e i n f l u e n t f o r the systems. The c h a r a c t e r i s t i c s of the lysimeters are found i n TABLE 3. The t y p i c a l percentage garbage composition i n the lysimeters were: Food Waste - 11.8 Garden Waste - 9.8 Paper Products - 47.6 Cardboard - 5.4 T e x t i l e s - 3.6 Wood - 4.7 TABLE 3 PHYSICAL CHARACTERISTICS OF LABORATORY LYSIMETERS Lysimeter Code Number Dimensions Cover Material Total Wt. of Garbage (lbs) Depth of Garbage (f t ) Wt. Density Before F i n a l Cover (lb/yd 3) R a i n f a l l (in/yr) Moisture Content (%) T 14 f t . deep, 4 f t . i n diameter Hog Fuel 3,420 8 884 15 34.7 X Same Hog Fuel 3,506 8 874 15 35.1 H Same S o i l 3,556 8 876 15 39.9 W Same S o i l 3,556 8 879 15 37.0 19. Metals 8.7 Glass & Ceramics 7.'0 Ash, Rock, and D i r t 1.4 TOTAL 100.0% Leachate from the lysimeters was c o l l e c t e d and stored (at 4°C) i n p l a s t i c containers f o r two months, p r i o r to the system start-up. Before the a c t i v a t i o n of the b i o l o g i c a l u n i t s , the stored samples were combined, mixed, and re-stored at 4°C to ensure as homogeneous an i n f l u e n t as p o s s i b l e . Approximately 250 l i t r e s of leachate was made av a i l a b l e f o r t h i s and another p a r a l l e l study being performed i n the lab (Zapf-Gilje (21)). The leachate composition during the temperature reduction phase (TRP) i s shown i n TABLE 4. Tests were performed throughout the duration of the TRP and l i t t l e v a r i a t i o n i n the c h a r a c t e r i s t i c s of the leachate was observed. As the TRP continued, i t became apparent that there was going to be i n s u f f i c i e n t leachate sample f or the cold temperature phase (CTP). To o f f s e t t h i s f o r the month p r i o r to the CTP, more leachate was c o l l e c t e d from the lysimeters and stored separately at 4°C. The c h a r a c t e r i s t i c s of the CTP composite sample are also shown i n TABLE 4. The CTP leachate c o n s t i t u -ent concentrations, p a r t i c u l a r l y f o r the metals, are s l i g h t l y lower than those found i n the TRP leachate. However, t h i s i s c h a r a c t e r i s t i c of land-f i l l leachates, as the l a n d f i l l ages. Other parameters d i f f e r e d only marginally. 3.3 Operating Variables i n the B i o l o g i c a l Units (a) pH and Dissolved Oxygen - No form of pH control was employed, since previous experiments indicated that the pH of the b a c t e r i a l culture would n a t u r a l l y adjust i t s e l f to a preferred operating l e v e l (10,11). TABLE 4 COMPOSITION OF LEACHATE FEED USED DURING THIS STUDY Parameter Temperature Cold Reduction Temperature Phase (mg/£) Phase (mg/£) BOD5 COD Lead Magnesium Manganese Nitrogen - TKN Ni c k e l Phosphorus Zinc pH* 13,640 12,920 19,250 19,370 Total Carbon 6,170 Tota l Organic Carbon 6,115 Total Solids 10,440 10,445 Tota l V o l a t i l e Solids 5,810 5,890 Total Suspended Solids 1,040 1,470 Tota l V o l a t i l e Suspended Solids 750 965 A c i d i t y as CaC0 3 (pH=8.3) 3,100 2,930 A l k a l i n i t y as CaC0 3 (pH=3.7) 4,110 4,120 Aluminum Calcium Cadmium Chromium 0.098 0.102 Iron 0.62 0.49 775 638 0.04 0.035 1,225 1,035 0.031 0.026 71.5 66.0 14.0 12.2 32.0 29.2 N03+N02 <0.05 0.33 0.10 10.0 10.1 39.2 22.8 5.2 5.2 * - Not i n mg/£ 21. A f t e r 15 days of operation, the pH i n a l l four units had s t a b i l i z e d above 8.1. The pH a f t e r t h i s time remained r e l a t i v e l y stable, varying only by ±0.2, depending upon the mixed l i q u o r dissolved oxygen l e v e l . FIGURE 2 shows that as the mixed l i q u o r dissolved oxygen increased, the mixed l i q u o r pH also increased. The mixed l i q u o r dissolved oxygen was maintained as high as the a i r supply system would permit. A s i g n i f i c a n t reduction i n dissolved oxygen was noted immediately a f t e r feeding. Yet, only on a few occasions was the dissolved oxygen monitored below 2.0 mg/l. On two occasions, a i r l i n e s were broken and for short periods of time, no a i r was being supplied to the system. The tanks temporarily went anaerobic and i n each case, i t took a few days f o r the system to s t a b i l i z e once again. No tes t s were performed during these "down" periods. (b) Nutrients - As the i n f l u e n t BOD /N/P r a t i o was only 100/0.23/ 0.07, nutrient addition was necessary to achieve the recommended nutrient l e v e l of 100/5/1 (22) . The a d d i t i o n a l nutrients were supplied by the d a i l y addition of predetermined q u a n t i t i e s of NH^NO^ and NH^H^PO^. (c) Organics and Metal Concentrations - No modifications were made to the organic and metal concentrations i n the i n f l u e n t . 3.4 The Temperature Reduction Phase The purpose of t h i s phase of the study was to acclimatize the b a c t e r i a to the leachate feed and then gradually reduce the system temperature. Before start-up, i t was necessary to decide upon "safe" mean c e l l r e t e n t i o n times (MCRT). Uloth (11) indicated that the optimum MCRT f o r a very high-strength leachate (B0D5 = 36,000 mg/l, COD = 48,000 mg/l) was 20 days f o r a system operated at 23°C. Koers (23) found that, with aerobic d i g e s t i o n of domestic sludge, when the mixed l i q u o r suspended s o l i d s (MLSS) FIGURE 2: pH of Mixed Liquors vs. Mixed Liquor Dissolved Oxygen (24°C) 23. were very high, the optimum MCRT varied by a fac t o r of four when operating at 5°C as compared to 20°C. As a r e s u l t , even though t h i s system's leachate sample was h a l f as strong as the Uloth sample, i t was decided that the MRCT's should be long enough (10, 15, and 20 days) to allow for v a r i a t i o n as the temperature was reduced. This study would operate two digesters at 10 days and two at 20 days, while a t h i r d set of three reactors would be operated by R. Zap f - G i l j e at an MCRT of 15 days. The reactors are i d e n t i f i e d i n TABLE 5. The reason for s p l i t t i n g the study i n t h i s manner was that both studies required as much homogeneous f i r s t - s t a g e e f f l u e n t as possible; therefore, multiple units were required at each MCRT. Because the systems were i d e n t i c a l , i t was agreed that b i o l o g i c a l k i n e t i c s would be examined at a l a t e r date using data from both studies. TABLE 5 REACTOR IDENTIFICATION REACTOR MEAN CELL RESIDENCE TIME - days AT START-UP STEADY-STATE - TRP STEADY-STATE - CTP A 20 25 25 B 20 25 25 C 10 15 15 D 10 •15 12 E ' - - 9 F - - . 6* * - Unit f a i l e d at 5°C. 24. (a) Start-Up - The b a c t e r i a l seed used f or the digesters was ob-tained from the Mamquam extended aeration Sewage Treatment Plant i n Squamish, B.C. The Mamquam activated sludge, had been previously used su c c e s s f u l l y by the-Environmental Group; therefore, i t was also chosen - for•these systems. The MLVSS of the seed was between 3,600 mg/Jt and 4,000 mg/Z; as a r e s u l t no modifications were made to the sludge s o l i d l e v e l s p r i o r to use. The study'was i n i t i a t e d by f i l l i n g reactors A and C with 5 l i t r e s of sludge feed. The a i r l i n e s were then connected and adjusted and the mechanical s t i r r e r s were turned on. S t i r r i n g speeds were set approximately equal i n each tank. The pH was recorded and the nutrients and i n i t i a l leachate dosages were added. The leachate dosage rates were calculated assuming that the system was complete mix - no r e c y c l e . With that assumption, the prescribed dosages rates were as shown i n TABLE 6: TABLE 6 LEACHATE DOSAGE RATES MCRT - days REACTOR VOLUME - l i t r e s LEACHATE DOSAGE RATE - ml/day 25 5 200 20 5 200 15 5 330 12 5 420 10 5 500 9 4.5 500 6 4.5 750 25. Although the dosage rates were to be 250 ml/day for reactors A and B and 500 m£/day f o r reactors C and D, i t was decided to i n i t i a l l y feed the reactors with a combination of raw sewage and leachate at a somewhat lower rate. The i n i t i a l dosage.to both tanks was 100 mi leachate plus 100 mi domestic sewage. I t was hoped that because the sludge was accustomed to degrading sewage, the a c c l i m a t i z a t i o n process might be hastened by sewage addition. However, within two days of start-up, the pH and the mixed l i q u o r suspended s o l i d s concentrations i n each reactor started to drop. I n i t i a l l y , i t was believed that t h i s was due to the addition of the low pH leachate feed and that i t would adjust i t s e l f when the system became acclimatized. But by day 5, the s o l i d s were s t i l l dropping and i t was decided to a r t i f i -c i a l l y adjust the pH up to 8.0. Within one hour of the pH adjustment, the pH was back down to 5.5 again and i t was apparent that something might be wrong with the systems. To determine what would happen, i t was decided to eliminate the sewage ad d i t i o n . Within two days, the pH started to r i s e and the systems began to s t a b i l i z e . I t i s s t i l l unclear what was wrong with the system while the sewage was being added; however when i t was ceased the problems were resolved. On day 8, reactors B and D were i n i t i a t e d , using one-third sludge from tanks A and C and two-thirds new activated sludge from the treatment plant. By day 11, the systems had s t a b i l i z e d and a regular operating procedure could be established. (b) Operation and Testing - The i n i t i a l operating schedule was designed to increase the MLSS concentrations as r a p i d l y as po s s i b l e . The d a i l y procedure was as follows: (1) Replace water l o s t through evaporation by the addition of 26. d i s t i l l e d water up to the 5 l i t r e mark. (2) Scrape' tank walls i n each digester to remove most of the adhering micro-organisms, thus returning- them to the mixed l i q u o r . (3) Check the pH, dissolved oxygen, and temperature. (4) Turn o f f a i r and s t i r r e r s to allow the b i o l o g i c a l s o l i d s to s e t t l e . (5) S e t t l e u n t i l there i s s u f f i c i e n t clean supernatant to withdraw 250 mH from digesters A and B and 500 mH from digesters C and D. The supernatant was wasted. (6) Turn on a i r and s t i r r e r s again. (7) Add volumes of leachate equal to those withdrawn from each digester. (8) Add n u t r i e n t s . Solids concentrations were monitored every 3 to 5 days through t h i s period. No other te s t s were performed on a continuous bas i s . On day 26, i t was decided that sludge wasting could begin and the systems could be allowed to approach steady-state. The new operating schedule was the same as previously noted, except mixed l i q u o r was wasted rather than supernatant. On day 30, the sludge ages were changed from 10 to 20 days to 15 and 25 days, r e s p e c t i v e l y , because i t appeared at that time, that the predeter-mined sludge ages might be too low and problems might a r i s e at the colder temperatures. The systems were operated for two and one-half weeks under the new conditions and by day 48, steady-state s o l i d s l e v e l s were achieved. (c) Steady-State Testing - The major change i n the steady-state operating procedure was that the withdrawn mixed l i q u o r was s e t t l e d (or f i l t e r e d ) , and then c o l l e c t e d and stored for the second-stage t e s t s . The t e s t i n g schedule was also expanded . s i g n i f i c a n t l y . TABLE 7 presents the c h a r a c t e r i s t i c s which were monitored throughout the TRP. A l l te s t s were performed according to Standard Methods ( 2 4 ) . At the end of each temperature operating period, the temperatures were reduced, the the systems were allowed one week of a c c l i m a t i z a t i o n p r i o r to the resumption of normal t e s t i n g . This time period was somewhat short, but was a consequence of the l i m i t e d quantity of feed a v a i l a b l e . TABLE 7 THE TESTING SCHEDULE FOR THE TRP SAMPLE CHARACTERISTIC REGULARITY OF TESTED FOR TESTING COD - 5 to 7 days BOD , TSS, VSS, TS r 2 weeks SVI Metals - At the end of each temperature l e v e l . COD, BODc - 3 weeks 5 TSS, VSS, Metals, TS, - Immediately p r i o r to A l k a l i n i t y A c i d i t y second-stage t e s t i n g Mixed Liquors COD, MLSS, MLVSS - 5 to 7 days TS - 2 weeks Metals - At the end of each temperature l e v e l 3.5 The Cold Temperature Phase The purpose of t h i s phase of the study was to observe the e f f e c t s of even colder temperatures on a b i o l o g i c a l treatment system (temperatures which might be encountered under Canadian f i e l d c onditions). To t h i s end, Col l e c t e d E f f l u e n t s Stored E f f l u e n t s 28. two new reactors and a new leachate composite sample were employed. The reactors were adopted from Za p f - G i l j e (21) nine days p r i o r to the CTP, and were already acclimatized to both colder temperatures and leachate feed. With the addition of the new reactors and the modification of reactor D to 12 days MCRT, a complete cross-section of MCRT u n i t s , ranging from 6 to 25 days, was av a i l a b l e f o r the CTP. This would allow an expanded a n a l y s i s , i n c l u d i n g b i o l o g i c a l k i n e t i c s at 5°C. The i n t e n s i t y of t e s t i n g during the CTP was greater than during the TRP. C h a r a c t e r i s t i c s such as sludge volume index, COD, suspended s o l i d s , and BOD were measured every three or four days. The operating schedule of 5 the CTP, however, was i d e n t i c a l to that of the TRP. 3.6 The Lime-Polishing Phase The purpose of t h i s phase of the study was to evaluate the e f f e c t i v e -ness of lime p r e c i p i t a t i o n as a means of p o l i s h i n g the aerobic b i o l o g i c a l e f f l u e n t s . Throughout the TRP and CTP, f i r s t - s t a g e e f f l u e n t s were c o l l e c t e d f o r the lime-polishing phase (LPP). No p o l i s h i n g was performed u n t i l the b i o l o g i c a l units were "shut down"; as a r e s u l t , some of the stored samples were held for more than three months p r i o r to t h e i r use. The long storage period resulted i n some minor a l t e r a t i o n s i n the c h a r a c t e r i s t i c s of the stored e f f l u e n t s , e s p e c i a l l y i n those with higher i n i t i a l s o l i d s ; however, the changes were not so great that they would n u l l i f y the second-stage procedure. (a) Sample Se l e c t i o n - The second-stage te s t s were only performed on those e f f l u e n t s which required further treatment by PCB standards (7). The f i r s t - s t a g e f i l t e r e d e f f l u e n t s from 24°C, 16°C, and 9°C were quite acceptable; consequently minimal t e s t i n g was c a r r i e d out on those samples. 29. Complete lime-polishing was performed on a l l the 5°C f i l t e r e d e f f l u e n t s and a l l poorly s e t t l e d e f f l u e n t s from higher temperature runs. The c h a r a c t e r i s t i c s monitored depended upon the i n i t i a l character-i s t i c s of the sample. COD, pH, i r o n , calcium, manganese, zinc , arid magnesium t e s t i n g were performed on a l l samples. Other metals were tested where necessary; however, i n many cases, the i n i t i a l concentrations were very low. BOD was not tested because there was i n s u f f i c i e n t sample to do 5 a complete a n a l y s i s . COD was employed as the measure to determine the quantity of organics removed by the lime treatment process. (b) The Test Procedure - The l i m e - p r e c i p i t a t i o n t e s t procedure employed was s i m i l a r to that used by MacLean (25). I t was as follows: (1) F i l l 600 m£ beakers with 400 m£ of sample and turn on paddles. (2) Add dosage of lime s l u r r y at a concentration that would leave between 500 mJl and 520 m£ of s o l u t i o n i n the beaker. (3) Rapid mix (100 rpm) the s o l u t i o n f o r 1 minute to disperse and completely mix the lime and the sample. (4) Slow mix (20-30 rpm) the s o l u t i o n f o r 5 minutes to enhance coagulation and f l o c c u l a t i o n . (5) Turn o f f paddles and s e t t l e f o r 30 minutes. I t was found that i f s e t t l i n g was going to occur, only 15 minutes of s e t t l i n g time was required. For the purpose of the experiments however, 30 minutes was a r b i t r a r i l y chosen as the s e t t l i n g time. (6) Prepare the samples f o r t e s t i n g . (c) Operational Problems - Unfortunately, the l i m e - p r e c i p i t a t i o n t e s t s d i d not run smoothly. A s i g n i f i c a n t problem arose during f l o e s e t t l i n g . 30. When the paddles were turned o f f , the f l o e was allowed to s e t t l e . The i n i t i a l s e t t l i n g was usually good; however, a f t e r approximately 10 minutes, a scum layer would..- form on the surface of the solu t i o n and the supernatant would s t a r t to cloud up. It.was evident that the fi n e f l o e s were being c a r r i e d by a gas to the surface of the so l u t i o n , but there was no immediate explanation as to where the gas was coming from. Although no s p e c i f i c t e s t s were performed on the gas, a hypothesis has been developed" to explain what i t was and possibly how i t was formed. It i s believed that the gas was N 2 and that i t was formed by d e n i t r i f i c a t i o n during the extended storage period. Most of the nitrogen i n the b i o l o g i c a l e f f l u e n t s was NO^-N. During storage, the samples became anaerobic and the NO^-N was converted by deni-t r i f i c a t i o n to N 2 gas. This res u l t e d i n the stored (at 4°C) samples becoming supersaturated with gas. When the samples were exposed to room temperature a i r , the gas slowly bubbled out of sol u t i o n . As the bubbles rose to the surface, they picked up p a r t i c l e s of lime f l o e . Eventually the surface became so clogged with f l o e that the gas could not escape and the sol u t i o n began to cloud up with f i n e , suspended f l o e p a r t i c l e s . To a l l e v i a t e t h i s problem, a simple procedure was developed. A f t e r the paddles were turned o f f , the samples were allowed to s e t t l e f o r 15 minutes. At that time, the q u a l i t y of s e t t l i n g and the c l a r i t y of the supernatant were assessed. I f i t was evident that the s e t t l i n g was s a t i s -factory, the s e t t l i n g was continued f o r the a l l o t t e d 30 minutes. I f a f t e r the 15 minutes, the f l o e was not forming well and the s e t t l i n g was poor, i t was concluded that the dosage used was too low to permit good s e t t l i n g and sample/dosage was l a b e l l e d "poor c l a r i f i c a t i o n " . The samples which were deemed " s a t i s f a c t o r y " were f i l t e r e d using 31. Whatman #4 f i l t e r paper and subsequently tested. This procedure was con-sidered acceptable because previous studies have shown that f i l t r a t i o n would produce s i m i l a r e f f l u e n t to l i m e - p r e c i p i t a t i o n where there was good f l o e formation (25). No f i l t r a t i o n was performed on samples that d i d not s e t t l e adequately. 32. CHAPTER 4 RESULTS AND DISCUSSION 4.1 First-Stage B i o l o g i c a l Treatment (a) B i o l o g i c a l Environment - Mixed l i q u o r leachate a c c l i m a t i z a t i o n was complete a f t e r 26 days of operation. Sludge wasting was then started and three more weeks elapsed before the system achieved steady-state condi-t i o n s . These conditions were maintained for one and a h a l f months, during which time e f f l u e n t c o l l e c t i o n and analysis was performed. The temperature was then reduced and s i m i l a r procedures were followed at subsequent tempera-ture l e v e l s . A summary of the steady-state operating conditions i s presented i n TABLE 8. The mixed l i q u o r v o l a t i l e suspended s o l i d s (MLVSS) and the mixed l i q u o r suspended s o l i d s (MLSS) concentrations are average values and derived from composite graphs of the digester s o l i d s (see Appendix I I ) . As the temperatures were reduced, the MLSS, the MLVSS, and MLVSS/MLSS r a t i o were a l l found to increase. There are a number of possible explanations for the observed e f f e c t s . The t r a d i t i o n a l explanation states that the increased MLVSS i s due to l e s s endogenous r e s p i r a t i o n at low temperatures, which allows a greater net growth of b a c t e r i a at long s o l i d s retention times (22). This assumes that the b a c t e r i a l species present are s i m i l a r at the reduced temperatures as at the higher temperatures. However, when considering a gradual temperature drop from 20°C to 5°C, i t i s po s s i b l e that there have been s i g n i f i c a n t changes i n the predominant b a c t e r i a l species present. T h e o r e t i c a l l y , as the temperature drops, the predominant b a c t e r i a l species w i l l s h i f t from the mesophilic range which predominates at the mid-range temperatures (15°C to 35°C) , to the psychrophilic range, which predominates at TABLE 8 BIOLOGICAL REACTOR OPERATING CONDITIONS Operating Temperature 24°C 16°C 9 C C 5< C MCRT (days) 15 25 15 25 15 25 9 12 15 25 Kg COD/kg MLVSS-day 0.41 0.26 0.34 0.26 0.26 0.19 0.38 0.31 0.24 0.17 Kg BOD5/kg MLVSS-day 0.29 0.18 0.24 0.18 0.18 0.13 0.25 0.21 0.16 0.11 MLSS (mg/£) 6,590 6,685 6,820 5,500 8,110 6,845 9,030 8,320 8,310 7,495 MLVSS (mg/£) 3,105 3,115 3,760 3,010 4,980 4,060 5,600 5,210 5,265 4,600 MLVSS 0.471 0.466 0.551 0.547 0.614 0.593 0.620 0.626 0.634 0.614 MLSS Mixed Liquor pH 8.2 8.3 8.1 8.2 8.1 8.2 7.9 8.1 8.0 8.2 34. the lower temperatures (-5°C to 20°C). Because t h e i r a c t i v e metabolic rates and m o t i l i t y are lower, the^psychrophiles depend more on food storage than do mesophiles (26). Therefore, as more psychrophilic bacteria are present, the food required per ba c t e r i a i s reduced (because each b a c t e r i a requires l e s s food from the feed due to greater storage and l e s s mobility) and a greater number of bac t e r i a i s required to degrade the same quantity of sub-s t r a t e . The MLVSS i s s h i f t e d upward accordingly u n t i l a new steady-state MLVSS i s established. The n o n - v o l a t i l e suspended s o l i d s l e v e l i s dependent upon the inorganic s o l i d s i n the feed, the formation of non-volatile end products through b i o -a c t i v i t y , and the suspended s o l i d s formed by p r e c i p i t a t i o n due to the high mixed l i q u o r pH (8.2). With t h i s waste, the increase i n MLVSS with tempera-ture was s i g n i f i c a n t l y greater than the increase i n MLSS. As a r e s u l t , the MLVSS/MLSS r a t i o also increased accordingly. The sudden drop i n s o l i d s i n the 25 day MCRT reactors between 24°C and 16°C was unexpected. I t i s believed to have been caused by the unstable conditions encountered i n the digesters a f t e r they were transferred from the open laboratory to the temperature c o n t r o l l e d room. The 15 day MCRT units showed some i n i t i a l i n s t a b i l i t y due to the t r a n s i t i o n ; however, they recovered quite r a p i d l y . The subsequent temperature drops caused very l i t t l e s t a b i l i t y problems i n the 15 and 25 day MCRT u n i t s . When the 6, 9, and 12 day MCRT units were adopted for the CTP work, maintaining s t a b i l i t y i n these units was a problem. The 12 day MCRT un i t , which was converted from a 15 day MCRT u n i t , showed some excess foaming due to the change i n feed rate,- however, the s o l i d s remained stable and no remedial measures were required. The 9 day MCRT un i t , however,, had serious foaming problems throughout the e n t i r e CTP. Foaming was so great that, to prevent foam from flowing over the walls of the reactor, the feed had to be added i n t e r m i t t e n t l y over an hourly period. S u r p r i s i n g l y , the s o l i d s l e v e l s i n the 9 day units were quite stable, despite the foaming problems. The 6 day MCRT un i t f a i l e d when the temperature was dropped to 5°C. For the f i r s t few days a f t e r the temperature drop, the reactor appeared to be operating s a t i s f a c t o r i l y (other than some minor foaming problems); however, by day 5 of the CTP, the unit began to change colour from dark brown to grey brown, and smell l i k e the leachate feed. The oxygen uptake was checked a f t e r feeding and was very close to zero. By day 8, i t was apparent that the unit had f a i l e d . The f a i l u r e was i n i t i a l l y believed to be due to a combination of the change of the leachate feed and the temperature drop. When looking at the CTP k i n e t i c s however - (see-APPENDICES 'III, IV, and V), i t would appear that~ the f a i l u r e would have occurred regardless of the change i n the feed and was d i r e c t l y a r e s u l t of the temperature drop. Calculations i n APPENDIX V, show that the minimum operational MCRT at 5°C was approximately 7.6 days. This explains the f a i l u r e of the 6 day.MCRT un i t and also shows why the 9 day MCRT uni t experienced such i n s t a b i l i t y problems. A f t e r the 6 day MCRT unit f a i l e d , an e f f o r t was made to start-up a new 25 day MCRT un i t at 5°C; however, within 10 days of operation, t h i s u n i t also f a i l e d . The f a i l u r e occurred i n a s i m i l a r way to that with the 6 day uni t . Immediately a f t e r start-up, the reactor appeared to be operating as was hoped f o r . The mixed l i q u o r pH was gradually increasing and foaming was at a minimum. But a f t e r 5 days, the mixed l i q u o r s o l i d s started to drop and the colour of the mixed l i q u o r changed to grey-brown. By day 10, the unit had f a i l e d . 36. This i s a very i n t e r e s t i n g r e s u l t , i n so much as i t indicates that, even though the systems can operate at cold temperatures, warmer temperature a c c l i m a t i z a t i o n appears to be necessary with a leachate feed as strong and as tox i c as that used i n t h i s study. Another aspect of t h e " b i o l o g i c a l environment not previously mentioned, i s the steady-state trace metal concentration i n the mixed l i q u o r , as pre-sented i n TABLE 9. From TABLE 9, i t can be seen that .under some circum-stances, the mixed l i q u o r metal concentrations were higher than those i n the leachate feed. The major point to be drawn here i s that the b i o l o g i c a l system was able to operate e f f e c t i v e l y , regardless of the high metal l e v e l s . There was also no change i n the mixed l i q u o r metals concentrations as the temperatures were reduced. This implies that the mixed l i q u o r metal concentrations were determined more by hydraulics and other f a c t o r s , than by b i o l o g i c a l conditions. The actual metal state ( s o l i d , dissolved, complexed etc.) i n the mixed l i q u o r i s r e l a t e d to the b i o l o g i c a l conditions and metal s o l u b i l i t i e s . This point w i l l be considered l a t e r . (b) F i l t e r e d versus Se t t l e d E f f l u e n t s - Before examining treatment e f f i c i e n c i e s , i t might be h e l p f u l to present a b r i e f d e s c r i p t i o n of the e f f l u e n t s . Both f i l t e r e d and s e t t l e d samples were taken at each temperature l e v e l , with the exception of 16°C, where only f i l t e r e d samples were taken (due to the short operating period at that temperature). F i l t r a t i o n was performed using Whatman #4 f i l t e r paper. The e f f l u e n t s were l i g h t brown i n colour and possessed a "dusty" smell. Despite f i l t r a t i o n , there was s t i l l f i n e c o l l o i d a l s o l i d s i n the samples. S e t t l i n g was performed i n one l i t r e graduated c y l i n d e r s f o r a period of 2 hours. The colour and smell of the s e t t l e d samples was the same as was found i n the f i l t e r e d samples. The quantity of s o l i d s present depended upon TABLE 9 BIOLOGICAL REACTOR MIXED LIQUOR METAL CONCENTRATIONS Operating Temperature 24°C 16c C 9 C C 5° C MCRT (days) TRP Leachate Feed 15 25 15 25 15 25 CTP Leachate Feed 9 12 15 25 Aluminum (mg/£) 0.62 0.53 0.53 0.56 0.51 0.53 0.51 0.49 0.48 0.44 0.40 0.42 Cadmium (mg/£) 0.04 0.049 0 .033 0.041 0.035 0.039 0.035 0.035 0 .038 0 .036 0 .035 0 .036 Calcium (mg/£) 775 129 153 124 127 199 221 638 241 167 149 131 Chromium (mg/£) 0.098 0.109 0 .094 0.090 0.112 0.095 0.091 0.102 0 .102 0 .080 0 .103 0 .105 Iron (mg/i) 1,225 1,175 1 ,152 1,190 1,140 1,186 1,093 1,035 1 ,025 1 ,029 1 ,025 994 Lead (mg/£) 0.031 0.023 0 .056 0.020 0.033 0.019 0.032 0.026 0 .027 0 .033 0 .020 0 .023 Magnesium (mg/i) 71.5 57.0 61.2 53.6 61.0 54.6 55.5 66.0 64.2 56.0 51.0 53.5 Manganese (mg/£) 14.0 8.2 10.7 8.3 9.3 10.4 13.5 12.2 10.6 8.3 8.1 8.3 Ni c k e l (mg/£) 0.33 0.36 0.32 0.26 0'.31 0.42 0.29 0.10 0.12 0.10 0.13 0.07 Zinc (mg/i) 39.2 28.5 26.3 31.2 26.1 32.1 24.2 22.8 21.2 18.9 18.7 17.6 38. the q u a l i t y of s e t t l i n g which was achieved. There were two reasons for c o l l e c t i n g both f i l t e r e d and s e t t l e d e f f l u e n t s . F i r s t l y , f i l t e r e d samples were c o l l e c t e d to determine the i d e a l i z e d soluble organic and metal removal e f f i c i e n c i e s , independent of the problems r e l a t e d to s e t t l i n g . Secondly, the f i l t e r e d sample data was also used i n the b i o l o g i c a l k i n e t i c s c a l c u l a t i o n s presented i n APPENDICES IV and V. The s e t t l e d samples were c o l l e c t e d to observe what e f f e c t the temperature drop would have on the q u a l i t y of s e t t l i n g . (c) S e t t l i n g - TABLE 10 presents a summary of the s e t t l i n g en-countered throughout the operating period. Before the data can be evaluated, a few q u a l i f i c a t i o n s must be made. F i r s t l y , the COD values i n the table are the stored sample COD's and as a r e s u l t , are the average values from through-out the e n t i r e operating period. This explains some discrepancy between the e f f l u e n t TSS and the e f f l u e n t non-soluble COD. Secondly, the Sludge Volume Index (SVI) values cannot be compared d i r e c t l y to those achieved using other wastewaters, because o f the very high suspended s o l i d s concentrations. The SVI's can, however, be compared to each other. As can be seen, the q u a l i t y of s e t t l i n g throughout the operating schedule was highly v a r i a b l e . However, there were some general trends observed. The following i s a b r i e f summary of the observations. (1) At colder temperatures, the s e t t l i n g rate-was more e r r a t i c . (2) E f f l u e n t c l a r i t y was also worse at colder temperatures. (3) The rate and q u a l i t y of s e t t l i n g was s l i g h t l y better at higher MCRT's. The p r i n c i p a l conclusion i s that, as the b i o l o g i c a l conditions become more extreme (higher feed rates, colder temperatures e t c . ) , more problems are encountered i n s o l i d s s e t t l i n g . This, combined with the well documented TABLE 10 BIOLOGICAL REACTOR SETTLING CONDITIONS Operating Temperature 24°C g c C 5° C MCRT (days) 15 25 15 25 9 12 15 25 Kg COD/kg MLVSS-day Kg BOD^/kg MLVSS-day 0.41 0.29 0.26 0.18 0.26 0.18 0.19 0.13 0.38 0.25 0.31 0.21 0.24 0.16 0.17 0.11 Soluble COD e f f l u e n t 352 331 270 262 551 448 331 314 (mg/A) Non-Soluble COD effluent 71 26 145 130 680 177 67 108 (mg/£) Total COD e f f l u e n t 423 357 415 392 1,231 625 398 422 (mg/A) MLSS (mg/l) T o t a l Suspended Solids E f f l u e n t (mg/Jc) Ty p i c a l Sludge Volume Index (m£/gm) Physical Description of S e t t l i n g 6,590 70 (30-140)* 75 (61-125)* -very slow s e t t l i n g 6,685 60 (45-100) 62 (51- 70) -adequate s e t t l i n g 8,110 275 (250-300) 55 (46- 63) -adequate s e t t l i n g 6,845 230 (190-270) 44 (38- 51) -good s e t t l i n g 9,030 705 (450-900) 33 (27- 42) -good to very good s e t t l i n g 8,320 250 (210-270) 27 (24- 29) -very good s e t t l i n g 8,310 140 (110-160) 33 (26-38) -very good s e t t l i n g 7,495 120 (105-145) 25 (18- 33) -very good s e t t l i n g -clear to very clear super--very c l e a r super-natant -very cloudy super-natant -very cloudy super-natant -very,very cloudy super-natant -very cloudy super-natant -cloudy super-natant -cloudy super-natant natant * - Refers to the range of values encountered. NOTE: - No s e t t l i n g tests were performed at 16°C. u> VO 40. problems associated with -transient loading conditions and the fill-and-draw feeding procedure, re s u l t e d i n the s e t t l i n g observed (21). The main symptom of the extreme operating conditions was poor f l o e formation. I t was e s p e c i a l l y evident at the colder temperatures. This was also observed by Selna and.Schroeder under parallel.treatment conditions (27,28). They a t t r i b u t e d the problems to the sudden increases i n organic loading, which res u l t e d i n greatly varying growth rates and less extra-c e l l u l a r slime, thus inducing breakup and poor formation of f l o e . The f i l l -and-draw feeding procedure, by nature, continuously shock loads the b i o l o g i c a l sludge. The extremes i n s e t t l i n g , therefore, were a r e s u l t of general system i n s t a b i l i t y . In a f u l l - s c a l e treatment system, t h i s i n s t a b i l i t y may not be a problem because the loading conditions are l i k e l y to be l e s s severe. Another po s s i b l e cause of the e r r a t i c s e t t l i n g behaviour was micro-b i o l o g i c a l s p e c i a t i o n . Although no d e t a i l e d t e s t s were performed to determine the composition of the b i o l o g i c a l population, i t i s well known that as temperature and feed rate change, the b a c t e r i a l population can a l t e r accordingly (26). The f l o e formation c h a r a c t e r i s t i c s of one population can be s i g n i f i c a n t l y d i f f e r e n t than another and therefore can induce changes i n s e t t l i n g conditions. (d) Biotreatment Removal E f f i c i e n c i e s - Unless otherwise s p e c i f i e d , t h i s section deals p r i m a r i l y with f i l t e r e d e f f l u e n t s . A summary of the t y p i c a l organic removal e f f i c i e n c i e s i s presented i n TABLE 11. COD removal was found to range from 97.2% (5°C, 9 day MCRT) to 98.6% (9°C, 25 day MCRT). The range i n BODc removals was from 99.5% (5°C, 9 day 5 MCRT) to greater than 99.9% (24°C, 25 day MCRT). For MCRT greater than 12 days, the e f f l u e n t BOD,, l e v e l s were superior to the B.C. P o l l u t i o n Control Board standards under a l l temperature conditions (7), with a l l e f f l u e n t TABLE 11 EFFECT OF TEMPERATURE, SETTLING RATE AND MCRT ON THE REMOVAL OF ORGANIC MATERIAL Operating Temperature 5°C 9°C 16° C 24° C Mixed Liquor COD A=8, 080 (53.3)* (mg/Jc-) B=7, 395 (61.8) C=7, 335 (62.1) C=7, 160 (62.8)* C=6 ,020 (68.7)* C=4 ,680 (75.7)* D=6, 480 (66.5) D=5, 530 (71.3) D=4 ,800 (75.1) D=4 ,205 (78.2) Settled E f f l u e n t COD mg/£) A=1, 231 (93.6) (2 hour s e t t l i n g period) B= 625 (96.8) (97.8) C= 398 (97.9) C= 415 (97.8) - C= 419 D= 422 (97.8) D= 392 (97.9) D= 357 (98.1) F i l t e r e d E f f l u e n t COD (mg/£) A= 551 (97.2) (Whatman #4 f i l t e r ) B= 448 (97.7) C= 331 (98.3) C= 270 (98.6) C= 295 (98.5) C= 352 (98.2) D= 314 (98.4) D= 262 (98.6) D= 315 (98.4) D= 331 (98.3) Settled E f f l u e n t BOD5 {mg/l) A= 176 (98.6) (2 hour s e t t l i n g period) B= 98 (99.2) C= 29 (99.8) C= 31 (99.8) - C= 21 (99.8) D= 41 (99.7) D= 24 (99.8) D= 12 (99.9) F i l t e r e d E f f l u e n t BOD5 (mg/l) A= 70 (99.5) (Whatman #4 f i l t e r ) B= 29 (99.8) C= 15 (99.9) C= 9 (99.9) C= 16 (99.9) C= 10 (99.9) D= 31 (99.8) D= 6(>99.9) D= 10 (99.9) D= 4(>99.9) Digester Description: A = 9 day MCRT units B = 12 day MCRT units *brackets r e f e r to percent removal with respect to raw C = 15 day MCRT units leachate values D = 25 day MCRT units 42. BOD ' s les s than 31 mg/i. This indicates that raw leachate can be e f f e c t i v e l y 5 treated through aerobic bio-treatment (assuming good s o l i d s removal i s provided). COD removal e f f i c i e n c y was found to be r e l a t i v e l y independent of the organic loading rate and the temperature l e v e l f o r the 15 day and 25 day MCRT un i t s . During the CTP.however, i n the lower MRCT un i t s , the COD removal e f f i c i e n c y decreased as the food to micro-organism r a t i o (F/M) was increased. FIGURE 3 shows the COD removal e f f i c i e n c y as a function of the organic loading during the CTP. FIGURE 3 also gives some i n d i c a t i o n of the operational changes which occurred as 'fa i l u r e was approached i n the b i o l o g i c a l u n i t . The removal e f f i c i e n c y of the system remained r e l a t i v e l y constant up u n t i l the loading rate approached the loading rate at which f a i l u r e occurred. At that time, the v i t a l c h a r a c t e r i s t i c s deteriorated very r a p i d l y , with the un i t f a i l i n g suddenly. This point of f a i l u r e was a r e s u l t of several f a c t o r s , including the system temperature, the system operational s t a b i l i t y , and the developed organic and metal t o x i c i t y ( r e s u l t i n g from higher feed concentrations). This was s i m i l a r l y observed at the warmer temperatures by Zapf - G i l j e (21). There i s one inconsistency i n the data presented. Unexpectedly, as the temperature was reduced from 24°C to 9°C, the f i l t e r e d COD removal e f f i c i e n c y improved s l i g h t l y . There was no corresponding change i n the se t t l e d e f f l u e n t COD removal e f f i c i e n c y . This discrepancy possibly r e s u l t e d from the more stable operating conditions i n the temperature c o n t r o l l e d room, and as a r e s u l t , was not necessar i l y r e l a t e d to the rate of b i o - a c t i v i t y achieved at the d i f f e r e n t temperatures. TABLE 12 and TABLE 13 present a summary of the metal removal e f f i c i e n c i e s through b i o l o g i c a l treatment of the leachate. In general, the \ \ Organic Loading Rate - kgCOD/kg MLVSS-day FIGURE 3: COD Removal vs. Organic Loading Rate During CTP 44. removal of metal contaminants was very good. Removals of greater than 96% were achieved for Fe, Mn, and Zn i n the f i l t e r e d samples. Ca (86.8% to 96.0%), Pb (greater than 70%), Cr (70.0% to 80.0%), and Ni (67.8% to 82.0%) were also e f f e c t i v e l y removed. Reduction of Mg (32% to 40%) was found to be substan-t i a l l y l e s s . No figures are reported for Cu and A l because of contamination i n the stored samples. B i o l o g i c a l systems can remove metals by three mechanisms; simple p r e c i p i t a t i o n , micro-organism uptake by the sludge, and phy s i c a l adsorption to or entrapment by the b i o l o g i c a l f l o e s . The primary removal mechanism for each metal depends upon the s o l u b i l i t y products and the r e l a t i v e a f f i n i t y f o r sludge uptake of the given metal. The factors a f f e c t i n g the uptake of metals by the sludge include pH, metal concentrations, MLVSS concentration, and metal form, e i t h e r soluble or insoluble (29). Because of the large increase i n f i x e d suspended s o l i d s between the leachate feed (pH = 5.2) and the mixed l i q u o r (pH > 8.0), i t appears that metal p r e c i p i t a t i o n was the major metal removal mechanism i n t h i s study. Most l i k e l y , sludge uptake also contributed to metal removal, p a r t i c u l a r l y with metals such as Pb and Cr (30); however, with the pH increase and the very high metals concentrations, p r e c i p i t a t i o n was probably much more prominent. L i s t e d below i s a b r i e f evaluation of possible removal mechanisms fo r each metal: (1) Calcium - Ca was p r i m a r i l y removed as CaCO^ p r e c i p i t a t e . The s e t t l i n g of CaCO^ was aided by adsorption and entrapment onto the b i o l o g i c a l f l o e . Other mechanisms were not considered l i k e l y because of the magnitude of the removals achieved (3). (2) Iron - Fe was probably removed by p r e c i p i t a t i o n as FePO^ and Fe(OH) , and s e t t l e d out with the a i d of adsorption and TABLE 12 SUMMARY OF METAL REMOVAL EFFICIENCIES DURING THE TRP Operating Temperature 24°C 16°C go C MCRT - days F - F i l t e r e d , S-Settled TRP Leachate Feed 15 F 15 S 25 F 25 S 15 F 25 F 15 F 15 S 25 F 25 S Calcium (mg/i) 775 39.7 (94.9)' 41.0 '(94.7) 58.6 (92.4) 60.0 (92.3) 31.2 (96.0) 82.7 (89.3) 61.1 (92.1) 62.7 (91.9) 102.5 (86.8) 103.9 (86.6) Chromium (mg/£) 0.098 0.014 (85.7) 0.020 (79.6) 0.019 (80.6) 0.028 (71.4) 0.026 (73.5) 0.020 (79.6) 0.023 (76.5) 0.036 (63.3) 0.014 (85.7) 0.029 (70.4) Iron (mg/i) 1,225 1.1 (99.9) 8.7 (99.3) 1.4 (99.9) 12.1 (99.0) 1.4 (99.9) 1.5 (99.9) 4.1 (99.7) 33.2 (97.3) 1.1 (99.9) 31.0 (97.5) Lead (mg/i) 0.031 <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) <0.01 (>68) Magnesium (mg/i) 71.5 48.2 (32.6) 49.2 (31.2) 46.3 (35.2) 47.0 (34.3) 46.0 (35.7) 45.9 (35.8) 44.2 (38.2) 46.0 (35.7) 45.2 (36.8) 45.6 (36.2) Manganese (mg/i) 14.0 0.05 (99.6) 0.15 (98.9) 0.02 (99.9) 0.14 (99.0) 0.17 (98.8) 0.02 (99.9) 0.08 (99.4) 0.25 (98.2) 0.17 (98.8) 0.33 (97.6) Nic k e l (mg/i) 0.33 0.11 (66.7) 0.11 (66.7) 0.07 (78.8) 0.07 (78.8) 0.06 (81.8) 0.06 (81.8) 0.06 (81.8) 0.06 (81.8) 0.06 (81.8) 0.06 (81.8) Zinc (mg/i) 39.2 0.20 (99.5) 0.51 (98.7) 0.20 (99.5) 0.57 (98.5) 0.16 (99.6) 0.19 (99.5) 0.86 (97.8) 2.02 (94.8) 0.16 (99.6) 1 .41 (96.4) * - Brackets r e f e r to percent removal. TABLE 13 SUMMARY OF METAL REMOVAL EFFICIENCIES DURING THE CTP Operating Temperature 5°C MCRT - days F - F i l t e r e d , S-Settled CTP Leachate Feed 9 F 9 s 12 F 12 S 15 F 15 s 25 F 25 S Calcium (mg/l) 638 51.0 (92.0)* 51.2 (92.0) 44.8 (93.0) 45.6 (92.9) 54.7 (91.4) 55.2 (91.3) 66.1 (89.6) 67.8 (89.4) Chromium (mg/l) 0.102 0.30 (70.6) 0.39 (61.8) 0.024 (76.5) 0.039 (61.8) 0.025 (75.5) 0.050 (51.0) 0.024 (76.5) 0.047 (53.9) Iron (mg/l) 1,035 1.4 (99.9) 35.0 (96.6) 1.2 (99.9) 35.1 (96.6) 0.8 (99.9) 25.6 (97.5) 2.5 (99.8) 23.2 (97.8) Lead (mg/£) 0.026 <0.01 (>61.5) <0.01 (>61.5) <0.01 (>61.5) <0.01 (>61.5) <0.01 (>61.5) <0.01 (>61.5) <0.01 (>61.5) <0.01 (>61.5) Magnesium (mg/l) 66.0 45.0 (31.8) 45.0 (31 .8) 43.9 (33.5) 44.6 (32.4) 43.8 (33.6) 44.8 (32.1) 43.1 (34.7) 44.0 (33.3) Manganese (mg/l) 12.2 0.46 (96.2) 0.71 (94.2) 0.29 (97.6) 0.64 (94.8) 0.20 (98.4) 0.53 (95.7) 0.22 (98.2) 0.55 (95.5) tNick e l (mg/Jc) 0.10 0.10 (0.0) 0.10 (0.0) 0.07 (30.0) 0.08 (20.0) 0.07 (30.0) 0.09 (10.0) 0.07 (30.0) 0.09 (10.0) Zinc (mg/l) 22.8 0.27 (98.8) 1.16 (94.9) 0.21 (99.1) 1 .47 (93.6) 0.17 (99.3) 0.80 (96.5) 0.23 (99.0) 1.32 (94.2) * - Brackets r e f e r to percent removal t - Influent too low to provide s i g n i f i c a n t r e s u l t s 47. entrapment. The soluble i r o n concentration i s highly pH dependent. (3) Zinc, Lead, and Chromium - Zn, Pb, and Cr were removed by a combination of p r e c i p i t a t i o n and b i o l o g i c a l uptake. Zn and Pb could have formed carbonate or. phosphate p r e c i p i t a t e s , while Cr probably formed hydroxides. A l l . these metals have been shown to have a high a f f i n i t y for sludge uptake (30). (4) Manganese - Mn was probably removed by carbonate p r e c i p i t a t i o n . B i o l o g i c a l uptake and adsorption may also have played a role i n Mn removal (1). (5) Nickel - Ni may have been p r e c i p i t a t e d out as a hydroxide or complexed with other compounds present. I t i s u n l i k e l y that b i o l o g i c a l uptake played a s i g n i f i c a n t r o l e i n the removal of Ni, because of the very low micro b i o l o g i c a l requirements for N i . (6) Magnesium - Magnesium hydroxides w i l l not p r e c i p i t a t e out at a pH lower than 10.5; therefore Mg removal was poor. The removal achieved was probably a r e s u l t of some p r e c i p i t a t i o n , adsorption, and entrapment i n the f l o e . No s i g n i f i c a n t change was noted i n the e f f l u e n t metals' concentrations as the detention time was reduced. Neufeld (30) and Cheng (29) showed previously, that much of the metal uptake and p r e c i p i t a t i o n i n the mixed l i q u o r (95%) occurs very r a p i d l y a f t e r feeding; therefore, detention time would not play a s i g n i f i c a n t r o l e i n metal removal. Although the metal-compounds are,' i n general, s l i g h t l y more soluble at warmer temperatures, f i l t e r e d e f f l u e n t metal removals were not s i g n i f i c a n t l y a f f e c t e d by temperature, reduction. However, some metal removals, p a r t i c u l a r l y 48. at the colder.temperature, were quite d i f f e r e n t i n the s e t t l e d e f f l u e n t s . This was a r e s u l t of the va r i a b l e l e v e l s of s e t t l i n g noted and the chemical form which the metal was predominently i n ( s o l i d , dissolved, complexed e t c . ) . Fe and Zn, and to a l e s s e r extent Mn and Cr, showed increases i n concentration i n the poorly s e t t l e d e f f l u e n t s . Apparently, these metals were t i g h t l y bound into the b i o l o g i c a l f l o e and t h i s removal was highly dependent upon the q u a l i t y of s e t t l i n g . The other metals, Pb, Mg, Ca, and Ni, were e i t h e r dissolved i n the mixed l i q u o r or were i n a form which could be s e t t l e d more r e a d i l y , than the f l o e s with higher Fe and Zn content. I t would be i n t e r e s t i n g to examine the c h a r a c t e r i s t i c s of poorly s e t t l e d f l o e , as compared to well s e t t l e d f l o e , to see whether there i s a chemical d i f f e r e n c e . 4.2 Lime-Precipitation P o l i s h i n g (a) Introduction - 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 t r e a t i n g the raw leachate, both i n terms of organic removal and metal removal, but because of the very high i n i t i a l concentrations, further t r e a t -ment was s t i l l required to reduce the e f f l u e n t concentrations to below the PCB standards. TABLES 12, 13, and 14 present the second-stage i n f l u e n t c h a r a c t e r i s t i c s of the stored samples. Any discrepancies between TABLE 14 and those tables previously presented are a r e s u l t of modifications which occurred during storage. Tests were performed on a l l of the samples i d e n t i f i e d . A l l data from the lime p r e c i p i t a t i o n schedule are presented in'APPENDIX VII. (b) C l a r i f i c a t i o n - The l e v e l of c l a r i f i c a t i o n was dependent upon the pH . „ of "the treated sample. The pH_. • ., at^whieh adequate c l a r i f i -* f i n a l f i n a l ' cation took place (the c l a r i f i c a t i o n pH), ranged from 9.45 to 10.10 for samples with i n i t i a l a l k a l i n i t i e s and hardness between 396 mg/£ and TABLE 14 SECOND-STAGE INFLUENT CHARACTERISTICS TEMPERATURE MCRT-days Sample pH COD BODc Total T o t a l A l k a l i n i t y A c i d i t y T o t a l C O F or S # (mg/4) (mg/?) Solids Suspended mg/A mg/£ Dissolved ( m g / £ ) Solids as CaC0 3 as CaC0 3 Solids ( m g / A ) 24 15 - S 1 7.4 419 21 1565 140 629 37 1425 24 25 - S 2 7.6 357 12 1720 120 528 11 1600 24 15 - F 3 7.9 352 10 1795 25 528 14 1770 24 25 - F 4 7.8 331 4 1855 25 523 12 1830 16 15 - F 5 8.2 295 16 1420 15 518 3 1405 16 25 - F 6 8.2 315 10 1700 25 427 2 1670 9 15 - S 7 7.7 415 31 1745 220 555 16 1525 9 25 - S 8 7.8 392 24 1920 380 466 13 1540 9 15 - F 9 8.1 270 9 1540 25 540 10 1515 9 25 - F 10 8.2 262 6 1685 5 424 6 1680 5 9 - S 11 7.6 1231 176 2275 450 851 21 1825 5 12 - S 12 7.8 625 98 2110 240 498 16 1870 5 15 - S 13 8.0 398 29 1795 145 631 10 1650 5 25 - S 14 8.0 422 41 1955 100 437 8 1355 5 9 - F 15 7.8 551 70 1920 20 732 16 1900 5 12 - F 16 8.1 448 29 1860 10 485 7 1850 5 15 - F 17 8.0 331 15 1645 5 570 6 1640 5 25 - F 18 8.2 314 31 1610 5 396 3 1605 50. 851 mg/£, and 100 mg/Z and 150 mg/£ as CaCO^ re s p e c t i v e l y . This i s s i m i l a r to r e s u l t s obtained with raw wastewater and secondary e f f l u e n t , where f or high alkalinity-hardness samples (greater than 350 mg/Z of CaCO^), a c l a r i -f i c a t i o n pH of 9.5 was common (31). This pH roughly corresponds to the pH -2 where insoluble CO^ a l k a l i n i t y (which can r e a d i l y form p r e c i p i t a t e s ) be-comes the predominent carbonate specie present rather than soluble HCO^ a l k a l i n i t y (22). The r e l a t i o n s h i p between the lime dosage added and the j _ n a ^ °f t n e solution i s presented i n FIGURE 4. This general curve w i l l be used on the subsequent curves i n d i c a t i n g organic and metal removals r e l a t i v e to lime dosage. (c) Organic Removals - FIGURE 5 indicates the l e v e l s of COD reduc-t i o n as re l a t e d to the lime dosages applied ( r e l a t i v e to the pH_. , a f t e r f i n a l e f f l u e n t s e t t l i n g ) . In a sample with an i n i t i a l COD of between 262 mg/Z and 551 mg/2, and suspended s o l i d s equal or l e s s than 25 mg/Z, a dosage of 900 mg/Z Ca(0H) 2 was required to achieve a 25% reduction i n COD. This removal rate i s equal or better than that achieved using l i m e - p r e c i p i t a t i o n on raw leachate (16,31). Lime-precipitation treatment i s t r a d i t i o n a l l y more e f f e c t i v e on r e f r a c t o r y organics (31). Since most of the organic material remaining a f t e r b i o l o g i c a l treatment i s non-biodegradable, the improved removal rate was as expected. The l e v e l s of suspended s o l i d s i n the i n f l u e n t were an important f a c t o r i n the removal of re s i d u a l organics. An attempt was made to co r r e l a t e the suspended s o l i d s l e v e l with organic removal but no s t a t i s t i c a l l y s i g n i -f i c a n t r e l a t i o n s h i p could be developed. Generally, the higher the suspended s o l i d s , the greater the percent removal i n COD was achieved (at a constant lime dosage). This occurred p r i m a r i l y because of the quantity of organic material which was i n i t i a l l y present i n the suspended s o l i d s of the samples. 51. I 5 0 0 r -pH_. A f t e r L i m e addit ion F i n a l FIGURE 4 : Lime Additions* vs. pH — f i n a l A f t e r Lime Additions *NOTE . For second stage lime addition. A l l i n f l u e n t s o l i d s l e v e l s . 52. FIGURE 5; Lime Additions and COD Removals* vs. pH_, , Aft e r Lime Additions, f i n a l *NOTE: For Second Stage Lime Addition, Where Total Suspended S o l i d s i s 25 mg/L or Less i n the Influent. Percent removals are misleading i n samples containing higher i n i t i a l s o l i d s l e v e l s . 53. The addition of lime improved the s e t t l i n g of the b i o l o g i c a l s o l i d s and thus the apparent COD removal was greater. In the higher suspended s o l i d s samples, the c l a r i f i c a t i o n pH appeared to be higher than the average. This was p r i m a r i l y a r e s u l t of the slower s e t t l i n g rates (due to the very high s o l i d s l e v e l s i n the t e s t beakers). As expected, the higher i n i t i a l suspended s o l i d s samples produced greater volumes of sludge. The other factors a f f e c t i n g the c l a r i f i c a t i o n pH, and consequently, the lime dosage required to achieve further organic removals, were the in f l u e n t COD and the a l k a l i n i t y . FIGURES 6 and 7 show the quantity of lime required to achieve a further 20% COD removal at the corresponding COD and a l k a l i n i t y l e v e l s . Both figures show reasonable c o r r e l a t i o n between the i n i t i a l c h a r a c t e r i s t i c measured and the dosage required. An attempt was made to r e l a t e the a l k a l i n i t y with the COD; however, no s t a t i s t i c a l c o r r e l a t i o n could be developed. Even though neither fi g u r e has quite enough points to be t o t a l l y convincing, i t i s possible to reach general conclusions: (1) At lower suspended s o l i d s l e v e l s (**25 mg/£) , sample a l k a l i n i t y and COD are both very important i n determining the lime dose required. A l k a l i n i t y i s probably more important than COD. (2) The higher the a l k a l i n i t y and COD, the higher the lime dosage required to achieve a consistent percentage organic removal e f f i c i e n c y . This i s roughly defined on FIGURES 6 and 7. (3) At high suspended s o l i d s l e v e l s (not shown), the COD i s more s i g n i f i c a n t r e l a t i v e to the percent removal e f f i c i e n c y (because of the presence of organics i n the excess s o l i d s ) , although a l k a l i n i t y i s s t i l l important. (d) Metal Removals - Fe, Zn, Mn, Mg, and Ca were a l l monitored a f t e r 54. 600 i -500 e g 4001 o c o 300 Sample : # COD (mg/L) Lime (mg/L) : 3 352 790 : 4 . 331 790 5 295 840 6 315 750 9 270 770 10 262 710 15 551 1110 16 448 930 17 331 810 18 314 710 / / / / / / I I L= I.465C + 3I2.8 r 2 = 0.862 / / / / + + / +/ / 200' 0 / J 500 1000 1500 (L) Lime required to reduce COD by 20%-mg/LCa(0H) 2 FIGURE 6: Lime Required to Reduce COD by 20% vs. the Influent COD*. *NOTE: For Second Stage Lime Addition, Where Suspended Solids i s 25 mg/L or Less i n the Influent. 55. 800r-o < 500 400 Sample # A l k a l i n i t y mg/L as CaC0 3 Lime (mg/L) 3 528 790 4 523 790 5 518 840 ro O 700 — 6 427~ 750 O a 9 540 770 o 10 424 710 o 15 732 1110 _ l 16 485 930 E 17 570 810 l >s 600 — 18 396 710 +-L = 1.50A + 47.8 2= 0.701 0 500 1000 1500 (L)Lime required to reduce COD by 2 0 % - m g / L Ca(0H) 2 FIGURE 7: Lime Required to Reduce COD by 20% vs. the Influent A l k a l i n i t y * *N0TE: For Second Stage Lime Addition, Where Suspended So l i d s i s 25 mg/L or Less i n the Influent. 56. the l i m e - p r e c i p i t a t i o n t e s t s , where po s s i b l e . The other metal concentrations were below the PCB standards already (7). FIGURES 8 through 12 indi c a t e the removals observed for the respective metals. Fe, Zn, Mn, and Mg a l l followed e s s e n t i a l l y the same removal pattern. The higher the lime dosage (and pH - n a l ) / the greater the metal removal. The pH at which "effective""'' metal removal occurred, varied from metal to metal. As pH was increased, Fe was removed f i r s t , then Zn, then Mg and f i n a l l y Mn. This corresponds well with the hydroxide s o l u b i l i t y products presented i n APPENDIX VI. The l e v e l of suspended s o l i d s i n the i n f l u e n t d i d not s i g n i f i c a n t l y a f f e c t the pH at which " e f f e c t i v e " metal removal was achieved. Calcium showed a s l i g h t l y d i f f e r e n t removal, pattern. At lime dosages between 300 mg/£ and 700 mg/£ Ca(OB)^, Ca removal was c o n s i s t e n t l y around 79%; however, at dosages greater than 700 mg/£ CafOH)^, Ca removal declined. At a dosage of 1,350 mg/£ CatOH),^ the e f f l u e n t Ca l e v e l was s l i g h t l y greater than the i n f l u e n t Ca concentration and was increasing with higher dosages. Apparently, at a dosage of roughly 700 mg/£ CatOH)^, the r e s i d u a l a l k a l i n i t y i n s o l u t i o n was used up, and the excess Ca added, accumulated i n s o l u t i o n . (e) Removal Mechanisms - Generally, the l e v e l of organic material removed d i r e c t l y corresponded to the v i s u a l l y observed quantity of f l o e developed and the subsequent q u a l i t y of s e t t l i n g . As there was no s p e c i f i c t r a n s i t i o n pH at which the organic removal rate improved (as with the metals), i t would appear that the organics were removed by a general increase i n the f l o e formed. This implies that organic removals with lime p r e c i p i t a t i o n are r e l a t e d to phy s i c a l mechanisms such as adsorption and entrapment i n con-"effective'.,ias,„d_§fined by PCB removal .requirements (7) . 57. I500r-E • o CO •o O lOOOh X o o o ^ 500 h CO E Final After Lime addition FIGURE 8 . Lime Additions and Iron Removals* vs. pH.. , A f t e r Lime Additions. — f i n a l *N0TE: For Second Stage Lime Addition, Where Total Suspended S o l i d s i s 25 mg/L or Less i n the Influent. In samples with TSS greater than 25 mg/L, percent removals are misleading because of high i n i t i a l Fe i n s o l i d s . 58. I500r-E i T3 0> •o •a a CM I o a o 1000 ^ 500 a> E Poor C l a r i f i c a t i o n 8 o — > % i n d i c a t e d + - % i n d i c a t e d 00 80 60 i o > o E a> 40 a: c M 20 9 10 II pH^. After Lime addition Final 12 FIGURE 9: Lime Additions and Zinc Removals* vs. pH . , A f t e r Lime Additions — f i n a l *N0TE: For Second Stage Lime Addition, Where T o t a l Suspended Solids i s 25 mg/L or Less i n the E f f l u e n t . In samples with TSS greater than 25 mg/L, percent removals are misleading because of high i n i t i a l Zn i n s o l i d s . 59. 8 9 10 II 12 pH . After Lime addition Final FIGURE 10: Lime Additions and Manganese Removals* vs. pH,.. , A f t e r Lime Additions. — f i n a l *NOTE: For Second Stage Lime Addition. A l l i n f l u e n t s o l i d s l e v e l s . 9 10 II 12 3l-L. After Lime addition Final FIGURE 1 1 : Lime A d d i t i o n s and Magnesium Removals* v s . pH,. , A f t e r Lime A d d i t i o n s . — c f i n a l *n0te: For Second Stage Lime Addition. A l l i n f l u e n t s o l i d s l e v e l s . FIGURE 12: Lime Additions and Calcium Removals* vs. pH . , Aft e r Lime Additions — f i n a l *NOTE: For Second Stage Lime A d d i t i o n . A l l i n f l u e n t s o l i d s l e v e l s . . 62. junction with the metal p r e c i p i t a t i o n . Apparently, as the metal hydroxides (and CaCO^) are formed, the organic materials, which are probably i n i t i a l l y complexed with the metals, are c a r r i e d out of so l u t i o n with the s e t t l i n g hydroxides. There i s also probably some phys i c a l entrapment of organic suspended s o l i d s during s e t t l i n g . The r e s u l t i s , that as the quantity of f l o e i s increased (as the pH i s increased), the l e v e l of organic removal i s increased. This was not necessar i l y the case with the removal of metals from s o l u t i o n . Although f l o e formation was important, the metal removals appear more d i r e c t l y r e l a t e d to the pH at which the corresponding metal hydroxides were formed. The observed sequential metal removals, as pH was increased, appears to v e r i f y t h i s . (f) Suspended Solids Removal - Indications are that the addition of lime reduced suspended s o l i d s most e f f e c t i v e l y . The lime dosage required to achieve acceptable suspended s o l i d s removal (based on v i s u a l observation), was approximately 450 mg/£ Ca^H)^-(g) Lime Requirements With and Without B i o l o g i c a l Pre-Treatment -When considering a treatment system when pH adjustment i s required, i t i s extremely important to evaluate the natural buf f e r i n g capacity of the waste. The quantity of chemical required, i n t h i s case lime, can be very high i f the system b u f f e r i n g capacity i s high. Bjorkman and Mavinic (16) found that with an i n i t i a l a l k a l i n i t y of roughly 4,000 mg/£ CaCO^, with raw leachate, 2,700 mg/l lime was required to increase the pH from 5.2 to between 10 and 11 where p r e c i p i t a t i o n w i l l occur. Although treatment using lime p r e c i p i t a t i o n (with no b i o l o g i c a l pre-treatment), i s unsatisfactory based on organic r e -movals alone, the p r o h i b i t i v e l y high lime dosage makes i t doubly unsuitable. With an a l k a l i n i t y removing step, l i k e b i o l o g i c a l treatment, p r i o r 63. to lime addition, the lime dosages can be reduced s i g n i f i c a n t l y . TABLE 14 indicates the reductions i n a l k a l i n i t y derived by bio-treatment i n t h i s study. With i n i t i a l raw leachates.- a l k a l i n i t i e s of roughly 4,120 mg/l CaCO^, the average f i r s t - s t a g e e f f l u e n t a l k a l i n i t y was 540 mg/l CaCO^. This i s a reduction of 85%. The r e s u l t i n g reductions i n lime required for lime p r e c i p i t a t i o n a f t e r bio-treatment are dramatic. To achieve a s i m i l a r pH of between 10 and 11 (as with Bjorkman), as average lime dosage of roughly 600 mg/l CafOH)^ was required. This i s a reduction of lime required (as compared to Bjorkman) of greater than 75%. Although the lime dosages are s t i l l quite high, they are s i g n i f i c a n t l y l e s s than i f there was no pre-treatment.. 4.3 Combined Biological-Chemical Treatment The combination of aerobic b i o l o g i c a l treatment, followed by lime-p o l i s h i n g , was shown to be a very e f f e c t i v e means of t r e a t i n g moderate to high strength sanitary l a n d f i l l leachates. There are two possible ways of operating the system, each being e f f e c t i v e under d i f f e r e n t circumstances. The f i r s t format would operate the b i o l o g i c a l unit at a low MCRT, thus r e l y i n g upon the lime-polishing unit to a greater extent. This would be e f f e c t i v e i f the temperature v a r i a t i o n s were not expected to be too great. A "safe" MCRT would be established, designed to achieve only "adequate" treatment and removal rates. Lime additions would be quite large but could be varied according to the f i r s t stage e f f l u e n t q u a l i t y . This study has shown that at lower MCRT l e v e l s (higher organic loading r a t e s ) , s e t t l i n g can be a problem; however, with higher lime dosages, the i n f e r i o r q u a l i t y f i r s t -stage e f f l u e n t s would be c l a r i f i e d without much trouble. The major problem with t h i s system would be the quantity of sludge being produced and subject to f urther treatment and di s p o s a l , as well as the cost of such large 64. quantities of lime. The advantage of t h i s system would be, that the b i o l o g i -c a l reactor would be r e l a t i v e l y small and c a p i t a l costs could be minimized. The second operating format would.have a longer MCRT i n the b i o -treatment p o r t i o n and employ s u b s t a n t i a l l y smaller lime dosages i n the po l i s h i n g u n i t . This would be e f f e c t i v e i f the temperatures were expected to be more v a r i a b l e . The system would depend almost e n t i r e l y upon the b i o -l o g i c a l u n i t f o r organic and metal removals. Lime treatment would only be employed i f the s e t t l i n g was poor, or at very cold temperatures when the ef f l u e n t q u a l i t y was le s s consistent. The advantage of t h i s system i s that the lime dosages would be reduced s u b s t a n t i a l l y and the chemical costs would be reduced accordingly. This system would also be l e s s prone to operational problems (because of the longer detention time), than the f i r s t system. The disadvantage i s that, with a larger b i o l o g i c a l reactor, the c a p i t a l costs would probably be higher. E i t h e r of these formats would be improved s i g n i f i c a n t l y i f the lime dosages could be reduced. The best means of reducing the lime requirement might be by the addit i o n of magnesium. Lime-magnesium treatment has also been shown to improve metal removals from wastewater (25). This should be examined i n a future study. The best operating MCRT for leachates l i k e those i n t h i s study, would be from 12 to 15 days. At 12 days, the removals were not quite as good as 15 days; however, the system was quite stable and with lime addition, good q u a l i t y e f f l u e n t s were produced. I f the 12 day MCRT unit was used, continu-ous lime add i t i o n would probably be required, since s e t t l i n g was a problem and the b i o l o g i c a l e f f l u e n t s d i d not quite meet the e f f l u e n t standards at the cold temperatures. I f the 15 day MCRT u n i t was used, l i t t l e lime p o l i s h i n g would be required. Lime p o l i s h i n g would only be employed i f s e t t l i n g deteriorated or i f other problems occurred at the colder tempera-tures. TABLE 15 presents the net removal e f f i c i e n c i e s achieved using 12 and 15 day MCRT u n i t s , and the "optimum" lime dosages at 5°C. A l l PCB standards (7) were met, with the exception of pH and Mn. TABLE 15 COMBINED TREATMENT REMOVAL EFFICIENCIES Constituent CTP MCRT=12 d. Lime Net MCRT=15 d. Lime Net PCB Leachate Settled Added Percent Se t t l e d Added Percent Standard (mg/i) Sample (mg/i) =800 mg/i Removal Sample (mg/i) =450 mg/i Removal (mg/i) pH 1 5.2 7.8 11.2 — 8.0 10.0 - 6.5-8.5 BOD5 12,910 98 <292 >99.8 29 <152 >99.9 45 COD 19,370 625 383 98.0 398 358 98.2 -TS 10,445 2,110 1,550 85.2 1,795 1 ,430 <1003 86.3 -TSS 1,470 240 <1003 >93.2 145 >93.2 100 Ca 638 45.6 9.6 98.5 55.2 10.0 98.4 -Cr 0.102 0.039 <0.01 >91.2 0.050 <0.01 >91.2 0.1 Fe 1,035 35.1 <0.07 >99.9 25.6 0.13 >99.9 0.3 Pb 0.026 <0.01 <0.01 >61.5 <0.01 <0.01 >61.5 0.05 Mg 66.0 44.6 9.8 85.2 44.8 40.2 39.1 150 Mn 12.2 0.64 0.21 98.3 0.53 0.24 98.0 0.05 Ni 0.10 0.08 <0.08 >20.0 0.09 <0.08 >20.0 0.3 Zn 22.8 1.47 0.11 99.5 0.80 0.21 99.1 0.5 Not i n mg/i - From f i l t e r e d samples or i f suspended s o l i d s were removed by improved s e t t l i n g - Assumed from c l a r i f i c a t i o n data 67. CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS The previous chapter presented the experimental r e s u l t s obtained from t h i s study. The. purpose of t h i s chapter i s to present a summary of the re s u l t s and to make suggestions f o r future research p r o j e c t s . 5.1 Conclusions The experimental r e s u l t s led to the following conclusions: (1) Aerobic b i o l o g i c a l treatment i s very e f f e c t i v e i n the treatment of high strength sanitary l a n d f i l l leachates (BOD = 13,300 mg/Jc, 5 COD = 19,300 mg/Jc.) . Soluble COD removals ranged from 97.2% (5°C, 9 day MCRT) to 98.6% (9°C, 25 day MCRT).' Soluble -B0D5 removals ranged from 99.5% (5°C, 9 day MCRT) to greater than 99.9% (24°C, 25 day MCRT). (2) Within the operating range tested, the soluble COD removal e f f i c i e n c y was independent of the organic loading rate and temperature f o r units with an MCRT of 15 days or greater. At 5°C, for units with MCRT of less than 15 days, COD removal e f f i c i e n c y decreased as the organic loading rate was increased. (3) The k i n e t i c parameters obtained at 5°C indicated that b i o -l o g i c a l growth was influenced by temperature reduction. The predicted minimum MCRT was 7.6 days. Extreme i n s t a b i l i t y was noted i n the 9 day MCRT un i t and the 6 day MCRT unit f a i l e d at 5°C. (4) As the temperatures were decreased, the mixed l i q u o r v o l a t i l e suspended s o l i d s concentrations increased, r e s u l t i n g i n lower operating F/M r a t i o s at the colder temperatures. The reduced 68. F/M r a t i o s seemed to counterbalance the lower b a c t e r i a l metabolic rates and resulted i n adequate treatment at the colder temperatures. (5) I t was not possible to start-up a 25 day MCRT unit at 5°C. This i n d i c a t e s that, even though e f f e c t i v e removals are possible at colder temperatures, -warmer, temperature acclima-t i z a t i o n , followed by gradual temperature reduction, may be necessary to prepare the units f o r cold temperature operations. (6) Metals were removed by b i o l o g i c a l uptake/entrapment and/or chemical p r e c i p i t a t i o n due to the high system pH. Metal removal e f f i c i e n c y , during aerobic b i o l o g i c a l treatment, was greater than 96% f o r Fe, Mn, and Zn, better than 80% for Ca, better than 70% f o r Pb, between 70 and 80% for Cr and Ni, and 40% f o r Mg. There was no s i g n i f i c a n t change i n metal removal e f f i c i e n c y as the temperatures were reduced or as the MCRT was increased. (7) The highly v a r i a b l e s e t t l i n g conditions were p r i m a r i l y a r e s u l t of the "shock load" nature of the fill-and-draw feeding procedure. The d e t e r i o r a t i o n i n s e t t l i n g q u a l i t y at colder temperatures was probably a r e s u l t of b i o l o g i c a l speciation and higher MLVSS l e v e l s . (8) The poor s e t t l i n g at the colder temperatures res u l t e d i n a carryover of excess organics into the f i r s t - s t a g e e f f l u e n t . Some metals,- (Fe and Zn, and to a les s e r extent, Mn and Cr) also showed s i g n i f i c a n t increases i n concentration i n the poorly s e t t l e d e f f l u e n t s . (9) The e f f i c i e n c y of c l a r i f i c a t i o n , due to lime addition, was 69. dependent upon the pH _. ., of the treated sample. The f i n a l c l a r i f i c a t i o n pH ranged from 9.45 to 10.10 for samples with i n i t i a l a l k a l i n i t i e s and hardnesses between 396 mg/l and 851 mg/l, and 100 mg/l and 150 mg/l as CaCO^, re s p e c t i v e l y . (10) In a sample with an i n i t i a l COD of between 262 mg/£ and 551 mg/l and low suspended s o l i d s (-^ 25 mg/£.) , a dosage of 900 mg/£ Ca(OH)^ was required to achieve a further 25% reduction i n COD. The samples with higher suspended s o l i d s concentrations had better percent removals of COD and produced a greater volume of sludge. (11) The i n f l u e n t COD and a l k a l i n i t y were s i g n i f i c a n t i n deter-mining the c l a r i f i c a t i o n pH and consequently the lime dosage required. When p l o t t i n g -the lime dosage required to reduce COD by 20%, versus COD and a l k a l i n i t y , i t was found that; L (lime required) = 1.465 C (COD) + 312.8 described the r e l a t i o n s h i p between lime and i n i t i a l COD (with 86% confidence) and; L (lime required) = 1.50 A ( a l k a l i n i t y ) +47.8 described the r e l a t i o n s h i p between lime and a l k a l i n i t y (with 70% confidence). The s i m i l a r slopes indicate that COD and a l k a l i n i t y are equally s i g n i f i c a n t i n the range of values presented here. (12) Fe, Zn, Mg, and Mn followed e s s e n t i a l l y the same removal pattern. The higher the lime dosage, the greater the amount of metal removed. The pH at which each metal was e f f e c t i v e l y removed was roughly determined by the hydroxide s o l u b i l i t y product of each metal. (1-3) The lime dosage required to achieve "adequate" suspended s o l i d s removal was approximately 450 mg/i Ca(0H) 2, the point where c l a r i f i c a t i o n was concluded to be e f f e c t i v e . (14) An aerobic b i o l o g i c a l u n i t of 12 days MCRT, with an addition of 800 mg/£ Ca(0H) 2 f o r p o l i s h i n g , and a b i o l o g i c a l u n i t of 15 days MCRT, with an addition of 450 mq/H Ca(OH) 2 for p o l i s h i n g , were found equally e f f e c t i v e at t r e a t i n g the raw leachate samples at 5°C. Both systems produced e f f l u e n t which would meet most of the PCB standards (7). 5.2 Recommendations for.Future Studies Much work has been'done to the treatment of sanitary l a n d f i l l leach-ates, but there i s s t i l l some research that should be.carried out. I t should include: (1) An evaluation of methods which might be used i n t r e a t i n g the metal-rich sludge which i s produced by the b i o l o g i c a l system. (2) An examination of how the i n i t i a l leachate strength a f f e c t s the k i n e t i c parameters. This could be performed by taking an i n i t i a l leachate sample and making three or four d i l u t i o n s , then t e s t i n g the c h a r a c t e r i s t i c a l l y proportional samples under i d e n t i c a l b i o l o g i c a l treatment conditions. (3) A p i l o t - s c a l e b i o l o g i c a l study, using e f f l u e n t s from a new sanitary l a n d f i l l , to observe the e f f e c t s of the changes i n the leachate c h a r a c t e r i s t i c s on the b i o l o g i c a l system. (4) An i n v e s t i g a t i o n of other p o t e n t i a l b i o l o g i c a l systems in c l u d i n g Rotating B i o l o g i c a l Contact Units (RBC), which would be capable of handling the v a r i a b l e flows involved with leaching systems. (5) An i n v e s t i g a t i o n of lime-magnesium treatment as a means of reducing the lime dosages required i n the p o l i s h i n g u n i t . (6) An examination of the p o t e n t i a l f or lime:regeneration and reuse from leaehate^lime p r e c i p i t a t i o n sludge. As indicated i n t h i s study, lime dosages, can be high. I t would be ex-tremely valuable i f lime regeneration from the sludge could be performed, thus e f f e c t i v e l y reducing the actual lime required for the treatment system. 72. REFERENCES 1. Lee, C.J., "Treatment of a Municipal L a n d f i l l Leachate," M.A.Sc. th e s i s , U n i v e r s i t y of B r i t i s h Columbia, Dept. of C i v i l Engineering, Vancouver, B.C., 100 pp., January 1979. 2. Chian, E.S.K. and DeWalle, F.B., " C h a r a c t e r i s t i c s of L a n d f i l l Leachates and Their Treatment," Journal of the Environmental. Engineering D i v i s i o n , ASCE, V o l . 102, No. EE2, pp. 411-431 (1976). 3. Cameron, R.D., "The E f f e c t s of S o l i d Waste L a n d f i l l Leachates on Received Water," paper presented at the 1975 B r i t i s h Columbia Water and Waste Association Conference, Harrison Hot Springs, B.C., 14 pages, A p r i l 1975. 4. Watkins, J.V., "A Study of Leachates from Sanitary F i l l s and Their E f f e c t s of Receiving Waters," Dept. of F i s h e r i e s and Forestry, P a c i f i c Region, Vancouver, B.C., 17 pp., J u l y 1970. 5. Hughes, G., Trembly, J . , Anger, H., D'Graz, J . , " P o l l u t i o n of Ground-water Due to Municipal Dumps," Technical B u l l e t i n No. 42, Inland Waters Branch, Dept. of Energy, Mines, and Resources, Ottawa, Canada, 98 pp., (1971) . 6. Zanoni, A.E., "Groundwater P o l l u t i o n from Sanitary L a n d f i l l s and Refuse Dump Grounds - A C r i t i c a l Review," Dept. of Natural Resources, Madison, Wisconsin, 43 pp. (1971). 7. Department of Lands, Forests, and Water Resources, " P o l l u t i o n Control Objectives f o r Municipal Type Waste Discharge i n B r i t i s h Columbia," V i c t o r i a , B.C., September 1975. 8. Boyle, W.C. and Ham, R.K., " B i o l o g i c a l T r e a t a b i l i t y of L a n d f i l l Leachate," Journal of Water P o l l u t i o n Control Federation, 45:860-872 (1974). 9. Chian, E.S.K. and DeWalle, F.B., "Evaluation of Leachate Treatment, Vo l . I I : B i o l o g i c a l and Physical-Chemical Processes," Environmental Protection Technology Series, U.S. Environmental Protection Agency, C i n c i n n a t i , Ohio, EPA-600/2-77-1866, 243 pp., November 1977. 10. Cook, E.N. and Force, E.G., "Aerobic S t a b i l i z a t i o n of L a n d f i l l Leach-ate," Journal of Water P o l l u t i o n Control Federation, 46:380-392 (1977). 11. Uloth, V.C. and Mavinic, D.S., "Aerobic Bio-Treatment of a High-Strength Leachate," Journal of the Environmental Engineering D i v i s i o n , ASCE, V o l . 103, No. EE4, pp. 647-661 (1977). 12. Steiner, R.L., Keenan, J.E., and Fungalori, A.A., Demonstration of a  Leachate Treatment Plant. U.S. National Technical Information Service, S p r i n g f i e l d , Va., PB/269/502, (1977). 73. 13. Mavinic, D.S., "Leachate Treatment Schemes - Research Approach1;" Paper presented at the EPA/SHWRD F i f t h Annual Research Symposium, Orlando, F l o r i d a , U.S.A., March 1979. 14. Poorman, B.L. and Cameron, R.D., " T r e a t a b i l i t y of Leachate from a Sanitary L a n d f i l l by Anaerobic Digestion," S o l i d Wastes Technical Report No. 5, Dept. of C i v i l Engineering, U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C., 75.pp., A p r i l 1974. 15. Ho, S., Boyle, W.C., and Ham, R.K., "Chemical Treatment of Leachates from Sanitary Landfills,'-' Journal of Water P o l l u t i o n Control Federa-t i o n , 46:1776-1791 (1974). 16. Bjorkman, V.B. and Mavinic, D.S., "Physio-Chemical Treatment of a High-Strength Leachate," presented at 32nd Annual Purdue Ind. Waste Confer-ence, West Lafayette, Indiana, 14 pp., May 1977. 17. Van F l e e t , S.R. et a l . , "Discussion, Aerobic B i o s t a b i l i z a t i o n of Sanitary L a n d f i l l Leachate,'! Journal of Water P o l l u t i o n Control Federation, 46:2611-2612 (1974). 18. Novak, J.T., "Temperature-Substrate Interactions i n B i o l o g i c a l Treat-ment';!' Journal of Water P o l l u t i o n Control Federation, 46:1984-1994 (1974). 19. Friedman, A.A. and Schroeder, E.D., "Temperature E f f e c t s on Growth Y i e l d i n Activated Sludge,'-' Journal of Water P o l l u t i o n Control Federa-t i o n , 44:1433-1442 (1972). 20. Benedict, A.H. and Carlson, ,D.A. ,- "Temperature .Acclimatization i n Aerobic Bio-Oxidation .Systems," Journal .of Water P o l l u t i o n Control Federation, 45:10-24 (1978). 21. Zapf-Gilje,, R..,-..."Effects of Temperature on Two-Stage B i o s t a b i l i z a t i o n of L a n d f i l l . Jjeachate, 1 1 M.A.Sc.- t h e s i s , Dept..,, of ..Civil Engineering, •University ^ofjJBritish", Columbia, October 1979. 22. Metcalf and Eddy, Inc., Wastewater Engineering, McGraw-Hill Book Co., New York, 1972. 23. Mavinic, D.S. and Koers, D.A., "Performance and K i n e t i c s of Low-Temperature Aerobic Sludge Digestion," Journal of Water P o l l u t i o n Control Federation, 51:2088-2097 (1979). 24. A.P.H.A., A.W.W.A., W.P.C.F., Standard Methods for the Examination of  Water and Wastewater, American Public Health Association, Inc., 14th E d i t i o n , 1976. 25. MacLean, B.H., "The Removal of Heavy Metals From Municipal Wastewaters by Lime-Magnesium. Coagulation;V M.A.Sc. Thesis, Dept. of C i v i l Engineering, U n i v e r s i t y of B r i t i s h Columbia, June 1977. 74. 26. F a r r e l l , J . and Rose, A.H., "Low Temperature Microbiology, 1' Advances i n Applied Microbiology, V o l . 7, Academic Press, New York, p. 335-378, (1965). 27. Selna, M.W. and Schroeder, E.D., "Response of Activated•Sludge Processes to Organic Transient I - Kinetics,'! Journal of Water P o l l u -t i o n Control Federation, 50:944-956 (1978). 28. Selna, M.W. and Schroeder, E.D., "Response of Activated Sludge Processes to Organic Transient II - Stoichiometry.^'" Journal of Water P o l l u t i o n Control Federation, 51:150-157 (1979). 29. Cheng, M.H., Paterson, J.W., and Minear, R.A., "Heavy Metals Uptake of Activated Sludge," Journal of Water P o l l u t i o n Control Federation, 47:362-376 (1975) . 30. Newfeld, R.D. and Hermann, E.R., "Heavy Metal Removal by Acclimated Activated Sludge," Journal of Water P o l l u t i o n Control Federation, 47:210-229 (1975) . 31. Minton, G.R. and Carlson, D.A., "Effects of Lime Addition on Treatment Plant Operation,'' Journal of Water P o l l u t i o n Control Federation, 48:1697-1727 (1976). 32. Ed. Weast, R.C., "CRC Handbook of Chemistry and Physics, 1' 51st e d i t i o n , Chemical Rubber Co. Pub., Inc., Cleveland, 1971. 33. Sayigh, B.A. and Molina, J.F., "Temperature E f f e c t s on the Activated Sludge Process';',' Journal of Water P o l l u t i o n Control Federation, 50:678-687 (1978). APPENDIX I EFFECT OF COLD TEMPERATURE ON BIODEGRADATION This i s a b r i e f summary of the possible e f f e c t s of temperature reduction on aerobic b i o l o g i c a l treatment. The conclusions presented are derived from the treatment of domestic wastewaters between 4°C and 20°C and may vary s l i g h t l y from that which occurred with the leachate feed (33): (1) The c e l l - s y n t h e s i s y i e l d c o e f f i c i e n t (mixed l i q u o r v o l a t i l e s o l i d s produced/unit of substrate u t i l i z e d ) i s independent, of temperature at low i n f l u e n t soluble substrate concentra-ti o n s ; however, at higher i n f l u e n t substrate l e v e l s , temperature w i l l e f f e c t the y i e l d c o e f f i c i e n t . (2) The micro-organism decay c o e f f i c i e n t i s independent of temperature, but can vary with the mean c e l l residence time. (3) Reducing the temperature w i l l reduce the soluble substrate removal e f f i c i e n c y , e s p e c i a l l y at higher feed rates. (4) Dissolved oxygen uptake rate i s reduced s i g n i f i c a n t l y as temperature i s reduced. (5) Sludge s e t t l i n g , i n terms of the sludge volume index (SVI), i s s a t i s f a c t o r y between 4°C and 20°C; however, nothing has been conclusively said about supernatent c l a r i t y i n the s e t t l e d e f f l u e n t s as the temperatures are reduced. (6) As the temperature i s reduced, the mixed l i q u o r v o l a t i l e suspended s o l i d concentrations (MLVSS) increase; the greater the system feed rate, the greater the MLVSS increase observed. APPENDIX II BIOLOGICAL SOLIDS LEVELS THROUGHOUT THE OPERATING SCHEDULE 2000 10 20 30 40 50 60 70 80 90 100 110 120 Time From Start-up ( Days) FIGURE; A : TSS Dur ing The TRP 6 0 0 0 h E c o •o o CO T3 <V T3 C <D Q . t o 3 CO CD O > 5 0 0 0 h 4 0 0 0 h 3 0 0 0 2 0 0 0 10 20 30 40 50 60 70 80 90 100 110 120 Time From Star t -up ( Days) FIGURE B: VSS Dur ing the TRP 6000 E I TO O </> T3 CD T3 C d) o. 3 (/) CD O > 5000H 40001-3500 Time From Start - up ( Days) 5000 10 20 Time From Start-up ( Days ) FIGURE C: Suspended Solids During the CTP (Temp=5°C) 79. APPENDIX III BIOLOGICAL TREATMENT DESIGN EQUATIONS The equations employed to define the b i o l o g i c a l operations and k i n e t i c s are presented i n Metcalf and Eddy (22). These include: dS __KXS s dt K + S( 1 ) dX/dt „ ds/dt 1 YKS F " r~TT ~ b (3) c s where dS ^ x. x . x . • - i • x . • mass -— = rate of substrate u t i l i z a t i o n , — ; — dt volume-time K = • maximum rate of waste u t i l i z a t i o n per unit weight of micro-organisms, mass/mass-time S = soluble substrate concentration, mass/volume X = mixed l i q u o r micro-organism concentration, mass/volume dX — - = net growth rate of micro-organism, mass/volume-time dt K = substrate concentration when dS/dt _ K 5 X ~ 2 Y = growth-yield c o e f f i c i e n t , mass of micro-organisms/mass of substrate u t i l i z e d b = micro-organism decay c o e f f i c i e n t , time ^ 6 = X , time C dX/dt For a complete-mix-no-recycle system, f i x i n g the mean c e l l residence time 8^ establishes the micro-organism concentration i n the reactor. 80. Metcalf and Eddy showed that on a f i n i t e time basis, that the rate of food u t i l i z a t i o n could be defined as: AS Qj (S -S ) - S o ~ S e At = v ° e " e — ( 4 ) c and i n turn, the b i o l o g i c a l s o l i d s concentrations as Y (S -S ) * - TT5T- <») C where Q = i n f l u e n t waste flow rate, volume/time V = volume of the reactor, volume S = t o t a l i n f l u e n t waste concentration soluble, mass/ o volume S = e f f l u e n t waste concentration, mass/volume, e To determine the minimum s o l i d s detention time, 9 . , S can be c mm replaced by S^ i n Equation (3). That i s , YKS 1 ° - b (6) ) . K + S c min s o The minimum s o l i d s detention time i s defined as "the residence time at which c e l l s are washed out of the system more r a p i d l y than they can reproduce". 81. APPENDIX IV BIOLOGICAL KINETIC PARAMETERS Although an analysis of k i n e t i c s over the e n t i r e temperature range i s not p o s s i b l e due to i n s u f f i c i e n t data, b i o l o g i c a l k i n e t i c s can be deter-mined for the cold temperature phase. A more complete evaluation of the k i n e t i c s w i l l be presented i n a future report, using data from both t h i s work and that of Z a p f - G i l j e (19). (1) Determination of Y and b (BOD Basis) 5 From Appendix I I , Equation (2): AX/At „ AS/At = Y — D X X s —s where AS o e A t . „ X "X X and AX e o e (assume X = 0) At e e o c c and AX/At _ 1_ x e A p l o t of AX/At vs. AS/At should y i e l d a s t r a i g h t l i n e with Y being X X the slope and -b being the y-axis intercept. 82. TABLE 16 KINETIC PARAMETERS, Y AND b - BOD,. BASIS . e c X S o S e AS/At (AS/At)/X (AX/At)/X=l/6 days mg/£ mg/£ mg/£ mg/£/day day day 9 5,600 12,920 70 1,428 0.255 0.111 12 5,210 12,920 29 1,074 0.206 0.083 15 5,265 12,920 15 860 0.163 0.067 25 4,600 12,920 31 515 0.112 0.040 The above data p l o t t e d i n FIGURE D, with a l e a s t squares f i t gives: Y = 0.49 mg VSS/mg BOD5 and b = 0.0148 day" 1 The c o r r e l a t i o n c o e f f i c i e n t i s 0.99. (2) Determination of K and K (BOD,. Basis) s 5 From Appendix I I , Equation 1: AS = e At ~ K +S s e Rearranging t h i s , we get X = f s 1__ 1 AS/At ~ K S + K e P l o t t i n g X vs. 1_ should y i e l d a s t r a i g h t l i n e with _s_ as the slope AS/At S K e and 1_ as the y-int e r c e p t . K 83. I o T3 X 0.1 0 0.08 0.06 0.04 0.02 -b -0.02 -0.04 • 0.05 y = 0.49x - 0.0148 .'.Y = 0.49 ( mg VSS/mg B0D 5 ) b =0.0148 day" 1 0.10 0.15 As/A t 0.20 0.25 (mg B0D 5/mg VSS/day) FIGURE D: Determination of Y and b Based on B0D 5 Data 84. TABLE 17 KINETIC PARAMETERS, K and K - BOD_ BASIS 8 c X S g AS/At 1/S X/(AS/At) days • mg/i mg/i mg/£/day i/mg day 9 5,600 70 1,428 0.014 3.92 12 5,210 29 1,074 0.034 4.85 15 5,265 15 860 0.067 6.13 25 4,600 31 515 0.032 8.93 The above data p l o t t e d i n FIGURE E, with a l e a s t squares f i t gives: K = 0.29 mg BOD^mg VSS/day K = 20.2 mg/£ s The c o r r e l a t i o n c o e f f i c i e n t i s only 0.08. This i s due to the e r r a t i c per-formance of the 25 day reactor at 5°C. I f the 25 day reactor i s not included, the c o r r e l a t i o n c o e f f i c i e n t i s 0.99 (the dotted l i n e on FIGURE E). This l i n e gives: K = 0.30 mg BOD5/mg VSS/day and K s = 1 2 - 3 m g / / £ Thus, the re s u l t a n t k i n e t i c parameters are not s i g n i f i c a n t l y d i f f e r e n t even though the c o r r e l a t i o n c o e f f i c i e n t i s low; the K and K^ parameters would appear to be acceptable. (3) Determination of. Y and b (COD Basis) Using s i m i l a r procedures as developed i n part (1), AX/At vs. AS/At X X can be plo t t e d , y i e l d i n g Y as the slope and -b as the y-intercept. 85. A 8 >» o T3 \ m Q O CD CP E \ cn cn > cn E y = 69.7x + 3.39 y = 41.4x + 3.38 w 3 < ".—=3.39 , K = 0.29 mgB0D5/mgVSS/day K K, K 69.7 , Ks= 20.2mg/L 0 J L 0 0.01 0.02 0.03 0.04 0.05 l/Se ( L/mg) 0.06 0.07 FIGURE E: Determination of K and K Based s on B0D 5 Data 86. TABLE 18 KINETIC PARAMETERS - COD BASIS e c days X mg/£ S. o. mq/SL S e mg/£ AS/At mg/£/day (AS/At)/X day ^ (AX/At)/X=l/0 day 9 5,600 19,370 551 2,091 0.373 0.111 12 5,210 19,370 448 1,577 0.303 0.083 15 5,265 19,370 331 1,269 0.241 0.067 25 4,600 19,370 314 762 0.166 0.040 The above data p l o t t e d i n FIGURE F, with a l e a s t square f i t gives: Y = 0.34 mg VSS/mg COD and b = 0.0157 day" 1 The c o r r e l a t i o n c o e f f i c i e n t i s 0.99. I t was not possible to develop K and K^ on a„COD basis because when X and 1_ were p l o t t e d , 1_ • ;was found to be a negative value. Apparently, AS/At S K e COD data oc c a s i o n a l l y cannot be used f o r k i n e t i c parameters. 87. A i >» o T3 < 0.1 0 0 . 0 8 h 0.06 0.04 0.02 -b -0.02 -0.04 y = 0.34x - 0.0157 .'. Y = 0.34 ( mg VSS/mgCOD ) b = 0 .0157 day -1 ( mg COD/mg VSS/day ) FIGURE F: Determination of Y and b Based on COD Data APPENDIX V THE. MINIMUM CTP SOLIDS DETENTION TIME From Appendix IV, on a BOD^ basis : Y = 0.49 mg VSS/mg BOD 5 b = 0.0148 day 1 K = 0.29 mg BODr/mg VSS/day 5 K = 20.2 mg/£ s From Appendix I I I , the minimum s o l i d s detention i s defined as YKS 1 = ° - b 0 . K +S c mm s o With an i n f l u e n t waste concentration of 12,920 mg/£ BOD,., 0 . can be 5 c min cal c u l a t e d : 1 (0.49) (0.30) (12,920) 3 . 12.3 + 12,920 c mm - 0.0148 = 0.132 Therefore, the minimum s o l i d s detention time, 9 . , would be 7.58 days c mm at 5°C. APPENDIX VI RELEVANT SOLUBILITY PRODUCTS OF .CATIONIC HEAVY, METAL ..OXIDES AND 'HYDROXIDES ^ 3 2^ ' Compound ksp (@25°C) Pb 3 (PO 4) 2 1 x 10" 5 4 Fe (OH) 3 -38 6 x 10 Cr(OH) 3 1 x 10 Cu(OH) 2 -19 3 x 10 Zn(OH) 2 -17 4.5 x 10 Ni(OH) 2 -16 1.6 x 10 Fe(OH) 2 -15 1.8 x 10 Pb 20(OH) 2 -15 1.6 x 10 Pb„CO„ 3 3 -15 1.5 x 10 Cd(OH) 2 -14 2 x 10 Mn(OH)2 2 x 10~ 1 3 Mg(OH)2 8.0 x 10~ 1 2 MnC03 8.8 x 10~ 1 1 ZnC0 3 2 x 10" 1 0 CaC0 3 -9 4.7 x 10 Ca(OH)„ -6 1.3x10 90. APPENDIX VII LIME PRECIPITATION. REMOVAL DATA The following are notes on the tables presented below: 1) A l l units are mg/& unless otherwise indicated. pH i s dimensionless. 2) "PC" indicates that "poor c l a r i f i c a t i o n " was obtained and no other tests were performed. 3) A l l metals were performed on a t o t a l basis. That data i s presented i n Section 5.3. 4) Samples 12 and 13 had t e s t s f o r extra metals performed on them. 5) B0Dc i s not presented because of sample contamination. 91. APPENDIX VII Lime P r e c i p i t a t i o n Removal Data 1 Sample Description: T=24°C, MCRT=15 d., TSS=140 mg/Jc. A l k a l i n i t y = 629 mg/£ as CaCO 3 Lime Dosage 0 200 450 800 1100 1540 pH 7.4 8.0 9.3 10.8 11.5 12.1 COD 419 PC PC 275 231 210 Fe 8.7 PC PC 0.11 <0.07 <0.07 Zn 0.51 PC PC 0.17 0.09 0.04 Mn 0.15 PC PC 0.11 0.05 <0.02 Mg 49.2 PC PC 24.2 4.61 0.78 Ca 41.0 PC PC 9.8 26.0 78.0 2 Sample Description: T=24°C, MCRT=25 d., TSS=120 mg/Jc-A l k a l i n i t y = 528 mg/Jl as CaCO 3 Lime Dosage 0 200 450 800 1100 1540 pH 7.6 8.4 9.6 11.1 11.6 12.2 COD 357 PC 262 245 210 193 Fe 12.1 PC 0.19 <0.07 <0.07 <0.07 Zn 0.57 PC 0.36 0.19 <0.02 <0.02 Mn 0.14 PC 0.13 0.07 0.07 0.02 Mg 47.0 PC 44.9 16.9 3.10 1 .02 Ca 60.0 PC 13.2 15.3 21.1 103.0 3 Sample Description: T=24°C, MCRT=15 d., TSS=24 mg/Jc-A l k a l i n i t y = 528 mg/Jc- as CaCO 3 Lime Dosage 0 200 450 800 1100 1540 pH 7.9 8.2 9.7 11.3 11.7 -COD 352 PC 332 280 260 -Fe 1.1 PC 0.24 <0.07 <0.07 -Zn 0.20 PC 0.15 0.04 <0.02 -Mn 0.05 PC 0.04 0.02 0.02 -Mg 48.2 PC 45.1 5.95 2.50 -c 39.7 PC 9.1 10.9 16.2 — 92. APPENDIX VII Lime P r e c i p i t a t i o n Removal Data 4 Sample Description: T=24°C, MCRT=25 d., TSS=25 mg/i A l k a l i n i t y = 523 mg/i as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 7.8 8.0 10.0 11.3 11.6 -COD 331 PC 298 264 242 -Fe 1.4 PC 0.16 <0.07 <0.07 Zn 0.20 PC 0.14 0.04 <0.02 -Mn 0.02 PC 0.02 0.03 <0.02 -Mg 46.3 PC 40.1 6.90 2.91 -Ca 58.6 PC 12.3 15.0 .21.0 — 5 Sample Description: T=16°C, MCRT=15 d., TSS=15 mg/i A l k a l i n i t y = 518 mg/i as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 8.2 8.6 10.1 11.3 11.8 -COD 295 PC 265 244 201 -Fe 1.4 PC 0.13 <0.03 <0.02 -Zn 0.16 PC 0.08 0.03 <0.02 -Mn 0.17 PC 0.15 0.05 0.02 -Mg 46.0 PC 39.1 5.95 2.01 -Ca 31.2 PC 7.9 10.1 23.2 — 6 Sample Description: T=16°C, MCRT=25d., TSS=25 mg/i A l k a l i n i t y = 427 mg/i as CACO, Lime Dosage 0 200 450 800 1100 1540 pH 8.2 8.9 10.4 11.6 12.0 -COD 315 PC 271 243 192 -Fe 1.5 PC 0.16 <0.07 <0.07 -Zn 0.19 PC 0.06 <0.02 <0.02 -Mn 0.02 PC 0.02 <0.02 <0.02 -Mg 45.9 PC 36.2 3.90 1.12 -Ca 82.7 PC 17.2 24.1 110.0 — 93. APPENDIX VII Lime P r e c i p i t a t i o n Removal Data 7 Sample Description: T=9°C, MCRT=15 d., TSS=220 mg/l A l k a l i n i t y = 555 mg/SL as CaC0 3 Lime Dosage 0 200 450 800 1100 1549 pH 7.7 8.7 10.1 11.5 11.8 -COD 41.5 PC 210 193 176 -Fe 33.2 PC 0.11 <0.07 <0.07 -Zn 2.02 PC 0.51 0.11 <0.02 -Mn 0.25 PC 0.13 0.07 <0.02 -Mg 46.0 PC 39.7 5.12 2.96 -Ca .62.7 PC 14.1 19.2 49.2 — Sample Description: T=9°C, MCRT=25 d., TSS=380 mg/l A l k a l i n i t y = 466 mg/£ as CaC0 3 Lime Dosage 0 200 450 800 1100 1540 PH 7.8 8.4 10.1 11.0 11.6 -COD 392 PC 221 196 183 -Fe 31.0 PC <0.07 <0.07 <0.07 -Zn 1.41 PC 0.19 0.06 <0.02 -Mn 0.33 PC 0.13 0.08 0.06 -Mg 45.6 PC 34.2 10.2 2.93 -Ca 103.9 PC 21.1 27.1 45.6 -9 Sample Description: T=9°C, MCRT=15 d., TSS=25 mg/£ A l k a l i n i t y = 540 mg/l as CaCO., Lime Dosage 0 200 450 800 1100 1540 PH 8.1 9.0 10.4 11.6 11.8 -COD 270 PC 229 220 200 -Fe 4.1 PC 0.29 <0.07 <0.07 -Zn 0.86 PC 0.39 <0.02 0.06 -Mn 0.08 PC 0.06 <0.02 <0.02 -Mg 44.2 PC 31.4 3.56 3.06 -Ca 61.1 PC 12.3 24.1 37.2 — 94. APPENDIX VII Lime P r e c i p i t a t i o n Removal 10 Sample Description: T=9°C, MCRT=15 d., TSS=25 mg/i A l k a l i n i t y = 540 mg/i as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 8.2 8.5 10.1 11.2 11.9 -COD 262 PC 229 204 179 -Fe 1.1 PC <0.07 <0.07 <0.07 -Zn 0.16 PC 0.06 <0.02 <0.02 -Mn 0.17 PC 0.13 0.06 0.03 -Mg 45.2 PC 37.6 10.2 1.46 -Ca 102.5 PC 19.0 18.1 76.2 — 11 Sample Description: T=5°C, MCRT=9 d., TSS=450 mg/i A l k a l i n i t y =851 mg/i as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 7.6 8.3 9.1 10.9 11.7 12.2 COD 1231 PC PC 622 545 416 Fe 35.0 PC PC 0.89 0.24 0.15 Zn 1.16 PC PC 0.27 0.09 0.07 Mn 0.17 PC PC 0.33 0.09 0.03 Mg 45.0 PC PC 19.2 4.27 2.76 ca 51.2 PC PC 13.6 18.3 97.0 12 Sample Description: T=5°C, MCRT=12 d., TSS=240 mg/i A l k a l i n i t y = 498 mg/£ as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 7.8 8.2 9.5 11.2 11.5 -COD 625 PC 518 383 342 -Fe 35.1 PC 1.6 <0.07 <0.07 -Zn 1.47 PC 1.21 0.11 0.10 -Mn 0.64 PC 0.55 0.21 0.13 -Mg 44.6 PC 37.2 9.8 3.96 -Ca 45.6 PC 10.1 9.6 16.5 — 95. APPENDIX VII Lime P r e c i p i t a t i o n Removal Data 13 Sample Description: T=5°C, MCRT=15 d., TSS=145 mg/l A l k a l i n i t y =631 mg/l as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 8.0 8.8 10.0 11.6 11.9 12.3 COD 398 PC 358 254 248 176 Fe 25.6 PC 0.13 <0.07 <0.07 <0.07 Zn 0.80 PC 0.21 0.11 0.09 <0.02 Mn 0.53 PC 0.24 0.11 0.13 0.02 Mg 44.8 PC 40.2 3.88 0.65 0.41 Ca 55.2 . PC 10.0 25.3 63.1 128.0 14 Sample Description: T=5°C, MCRT=25 d., TSS=100 mg/l A l k a l i n i t y = 437 mg/l as CaCO. Lime Dosage . . 0 200 450 800 1100 1540 PH 8.0 8.7 10.1 11.4 11.7 -COD 422 PC 351 323 290 -Fe 23.2 PC 0.79 <0.07 <0.07 -Zn 1.32 PC 0.30 0.10 0.06 -Mn 0.55 PC 0.20 0.18 0.15 -Mg 44.0 PC 39.1 4.4 1.30 -Ca 67.8 PC 16.0 21.0 30.1 — 15 Sample Description: T=5°C, MCRT=9 d., TSS=20 mg/l A l k a l i n i t y = 732 mg/£ as CaCO, Lime Dosage 0 200 450 800 1100 1540 pH 7.8 8.0 9.1 10.3 11.3 12.0 COD 551 PC PC 501 395 300 Fe 1.4 PC PC 0.13 <0.07 <0.07 Zn 0.27 PC PC 0.10 0.04 <0.02 Mn 0.46 PC PC 0.40 0.10 0.02 Mg 45.0 PC PC 34.3 5.01 0.44 Ca 51.0 PC PC 11.5 15.8 107.6 96. APPENDIX VII Lime P r e c i p i t a t i o n Removal Data 16 Sample Description: T=5°C, MCRT=12 d., TSS=10 mg/£ A l k a l i n i t y = 485 mg/£ as CaCO, Lime Dosage 0 200 450 800 1100 1540 PH 8.1 8.5 9.7 11.2 11.5 -COD 448 PC 402 333 276 -Fe 1.2 PC 0.30 <0.07 <0.07 - • Zn 0.21 PC 0.15 0.04 <0.02 -Mn 0.29 PC 0.24 0.10 0.07 -Mg 43.9 PC 39.1 8.9 4.01 -. Ca. . 44.8 PC 9.9 12.1 15.0 — 17 Sample Description: T=5°C, MCRT=15 d., TSS=5 mg/£ A l k a l i n i t y = 570 mg/£ as CaCO, Lime Dosage . 0 200 450 800 . 1100 1540 PH 8.0 9.0 10.3 11.7 11.9 -COD 331 PC 314 257 236 -Fe 0.8 PC <0.07 <0.07 <0.07 -Zn 0.17 PC 0.09 <0.02 <0.02 -Mn 0.20 PC 0.15 0.04 <0.02 -Mg 43.8 PC 36.8 1.45 0.96 -Ca 54.7 PC 11.9 28.9 64.0 — 18 Sample Description: T=5°C, MCRT=25 d., TSS=5 mg/Jl A l k a l i n i t y = 396 rag/Si as CaCO, Lime Dosage 0 200 450 800 1100 1540 PH 8.2 8.7 10.5 11.5 11.9 -COD 314 PC 282 256 195 -Fe 2.5 PC 0.11 <0.07 <0.07 -Zn 0.23 PC 0.09 <0.02 <0.02 -Mn 0.22 PC 0.21 0.05 0.03 -Mg 43.1 PC 12.1 4.50 2.01 -Ca 66.1 PC 12.9 19.0 47.0 — 

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