Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Effects of phosphorus addition on treatment efficiency of an anaerobic filter treating landfill… Muthukrishnan, Karthikeyan 1986

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1986_A7 M88.pdf [ 3.14MB ]
Metadata
JSON: 831-1.0062625.json
JSON-LD: 831-1.0062625-ld.json
RDF/XML (Pretty): 831-1.0062625-rdf.xml
RDF/JSON: 831-1.0062625-rdf.json
Turtle: 831-1.0062625-turtle.txt
N-Triples: 831-1.0062625-rdf-ntriples.txt
Original Record: 831-1.0062625-source.json
Full Text
831-1.0062625-fulltext.txt
Citation
831-1.0062625.ris

Full Text

EFFECTS OF PHOSPHORUS ADDITION ON TREATMENT EFFICIENCY OF AN ANAEROBIC FILTER TREATING LANDFILL LEACHATE by KARTHIKEYAN MUTHUKRISHNAN B.Tech.,Indian Institute of Technology, Madras, India, 1982 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in FACULTY OF GRADUATE STUDIES THE'DEPARTMENT OF CIVIL ENGINEERING We accept t h i s thesis as conforming to the required standard UNIVERSITY OF BRITISH COLUMBIA January,1986 © KARTHIKEYAN MUTHUKRISHNAN, January,1986 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 Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DF.-6 f l / R l ^ ABSTRACT Sanitary l a n d f i l l leachate i s a source of environmental concern due to i t s high organic strength and chemical d i v e r s i t y . The widespread use of sanitary l a n d f i l l s has resulted in regulatory authorities requiring municipalities to give serious consideration to the treatment and safe disposal of thi s wastewater. A number of lab-scale and p i l o t scale studies have indicated that the anaerobic f i l t e r .is highly competitive with other forms of b i o l o g i c a l treatment and has d i s t i n c t economic advantages. While there have been a number of studies based on a general o v e r a l l approach to leachate treatment by the anaerobic f i l t e r , limited' information is available on the role played by essential nutrients (phosphorus and nitrogen) in the b i o l o g i c a l treatment process. Laboratory studies were conducted at room temperature (22°C) to study the eff e c t of nutrient addition ( s p e c i f i c a l l y , phosphorus, the de f i c i e n t constituent of most leachates) on treatment e f f i c i e n c y of l a n d f i l l leachate by the upflow anaerobic f i l t e r . Two anaerobic f i l t e r s (0.975 metres x 0.15 metres diameter) were constructed using plexiglass pipes and packed with s t r i p s of corrugated fib r e - g l a s s sheets in four layers to form the f i l t e r bed. Leachate c o l l e c t e d from a nearby l a n d f i l l was applied at moderate organic loadings (2.0-4.2 kg COD/m3.day) to the two units maintaining a HRT of 0.987 days. i i During runs 2 and 4, leachate c o l l e c t e d from the Premier l a n d f i l l had a very low organic strength, necessitating the addition of acetic acid to raise that strength to around 2000 mg/l COD. When phosphorus addition was made at the 10 mg/l le v e l to this feed, no favourable e f f e c t on COD removal was observed, possibly because the feed was VFA based and not inclusive of complex organics. During run 3, the strength of the leachate increased to around 4000 mg/l, with a r e l a t i v e l y lower proportion of the COD present as VFA (around 1600 mg/l as acetic acid). When phosphorus addition was made to thi s feed at a 40 mg/l l e v e l , COD removal capacity of the anaerobic f i l t e r improved s i g n i f i c a n t l y , indicating that phosphorus may be added to an organically diverse waste with d i s t i n c t advantages. Table of Contents ABSTRACT i i LIST OF FIGURES wW LIST OF TABLES . viii' ACKNOWLEDGEMENT villi 1 . INTRODUCTION 1 2. RESEARCH OBJECTIVES 3 3. Literature Review 4 3.1 Microbiology of Anaerobic Digestion 4 3.1.1 Hydrolysis „ 4 3.1.2 ACID PRODUCTION 4 3.1.3 METHANE PRODUCTION 5 3.2 SUSPENDED AND ATTACHED GROWTH SYSTEMS 7 3.3 THE ATTACHED GROWTH SPECTRUM 8 3.3.1 THE FIXED BED (UPFLOW AND DOWNFLOW ANAEROBIC FILTERS) 8 3.3.2 THE MOVING BED (e.g.,the rotating b i o l o g i c a l contactor) ...8 3.3.3 THE EXPANDED BED 9 3.3.4 THE FLUIDI ZED BED 9 3.3.5 THE RECYCLED BED 9 3.4 OPERATIONAL CHARACTERISTICS OF ANAEROBIC FILTERS 10 3.4.1 FILTER START-UP 10 3.4.2 THE FILTER MEDIA 10 3.4.3 COD REMOVAL TRENDS 11 3.4.4 SLUDGE WASTING 12 3.4.5 ENVIRONMENTAL FACTORS OF IMPORTANCE ...12 3.4.5.1 TEMPERATURE 12 IV 3.4.5.2 pH 13 3.4.5.3 NUTRIENTS 13 3.4.5.4 TOXICITY 14 3.4.5.5 SHOCK LOADS 15 3.4.5.6 INTERMITTENT LOADS 16 3.5 ENERGY RECOVERY 16 3.6 VARIETY OF WASTES TREATED BY THE ANAEROBIC FILTER 17 4. EXPERIMENTAL PROCEDURE 19 4.1 LEACHATE COLLECTION AND HANDLING 19 4.2 EXPERIMENTAL SET-UP 20 4.3 FEED SCHEDULE 23 4.4 FILTER START-UP 24 4.5 SAMPLING SCHEDULE 24 5. EXPERIMENTAL METHODS 28 6. RESULTS 29 6.1 STEADY STATE 29 6.2 RUN 1 (DAY 1 to DAY 49) 38 6.3 RUN 2 (DAY 50 to DAY 98) 40 6.4 RUN 3(DAY 98-DAY130) 40 6.5 RUN 4 (DAY 130 - DAY 162) 41 6.6 RUN 5 (DAY 162-DAY DAY 177) 42 6.7 Gas Production 43 6.8 Solids Data 45 7. DISCUSSION OF RESULTS 47 7.1 P Addition at the 10mg/l l e v e l 47 7.2 P Addition at the 40 mg/l Level j 49 7.3 Gas Production 51 v 7.4 COD:P Ratio 52 7.5 TKN Uptake Data 53 7.6 To Add or not to Add Phosphorus 54 8. CONCLUSIONS 55 9 . RECOMMENDATIONS 58 BIBLIOGRAPHY 60 VI LIST OF FIGURES 3.1 PATHWAYS FOR METHANE FERMENTATION 06 4.1 EXPERIMENTAL SET UP 22 6.1 UNFILTERED COD VS TIME .. 30 6.2 FILTERED COD VS TIME 31 6.3 COD REMOVAL EFFICIENCY 32 6.4 METHANE PRODUCTION VS TIME 33 6.5 METHANE YIELD VS TIME 34 6.6 BOD REMOVAL EFFICIENCY 35 6.7 TOTAL KJELDAHL NITROGEN VS TIME 36 6.8 TOTAL PHOSPHORUS VS TIME 37 VII LIST OF TABLES 4.1 LEACHATE FEED CHARACTERISTICS 21 4.2 EXPERIMENTAL SCHEDULE 25 4.3 SAMPLING SCHEDULE 26 6.1 RESULTS OF STATISTICAL ANALYSES ON COD DATA 39 6.2 RESULTS OF STATISTICAL ANALYSES ON CH4 DATA 44 6.3 SUSPENDED SOLIDS DATA 46 0 v i i i ACKNOWLEDGEMENT I wish to express my appreciation and indebtedness to Professor J.W.Atwater, Assistant Professor of C i v i l Engineering, for his guidance, keen interest and constructive c r i t i c i s m during the course of thi s investigation and above a l l for introducing me to the joy and f u l f i l l m e n t of independent research. I also wish tb acknowledge the valuable advice and assistance received from Dr.Oldham. Thanks are also due to Susan Liptak, Paula Parkinson and Timothy Ma of the Environmental Engineering Laboratory for their invaluable advice and everpresent help throughout the course of t h i s work, especialy during periods of reactor breakdown. I also wish to express my gratitude to Guy Kirsch of the C i v i l Engineering Workshop for his help in the building and maintenance of the reactors. The f i n a n c i a l support for thi s work extended by the Natural Sciences and Engineeering Research Council of Canada i s g r a t e f u l l y acknowledged. I can never be thankful enough to my parents who placed my education above everything else in their l i v e s . viii? 1. INTRODUCTION The sanitary l a n d f i l l has come to be widely accepted for the ultimate disposal of s o l i d wastes. When water, either groundwater or rainwater, passes through the refuse bed, contaminated seepage known as leachate i s produced. This leachate usually contains a high concentration of organic and inorganic matter, including metals. The ch a r a c t e r i s t i c s of the leachate depend on the depth and composition of the refuse, the hydrogeology of the s i t e , the age of the l a n d f i l l , and the climate. Subsequent movement of the • leachate from the l a n d f i l l has the poten t i a l to cause serious degradation of groundwater or surface receiving waters. This may, in some instances, cause serious public health concerns especially i f the water body i s a source or potential source of drinking water. Therefore, i t i s often necessary to c o l l e c t and treat the leachate. B i o l o g i c a l treatment of leachate demands special attention due to the high concentration of organics and heavy metals. Chian and de Walle (1976) on detailed analysis of l a n d f i l l leachate, postulated, that for recent l a n d f i l l s , aerobic or anaerobic b i o l o g i c a l treatment processes are more e f f e c t i v e , whereas for s t a b i l i z e d l a n d f i l l s physical-chemical processes gave the best removal of organic matter. At the University of B r i t i s h Columbia, Uloth and Mavinic (1977) and Wong and Mavinic (1982) have shown that leachate lends i t s e l f well to aerobic stabilization.-Cameron and Koch (1980) demonstrated that anaerobic digestion i s a 1 2 suitable and e f f e c t i v e means of b i o s t a b i l i z a t i o n . Elsewhere, Henry e t . a l . (1982) and Austin et. al.(1984) have found that leachate, being a predominantly soluble organic waste, i s well suited for treatment by the anaerobic f i l t e r . The importance of the essential nutrients, phosphorus and nitrogen, in aiding aerobic b i o s t a b i l i z a t i o n of wastewater has been well established (Temoin,1980).It has also been quite well established (Speece and McCarty, 1964) that these nutrients play a leading role in the growth of microrganisms involved in anaerobic digestion. Since the anaerobic f i l t e r i s a r e l a t i v e l y new concept in wastewater technology (although the anaerobic f i l t e r was conceived in the late 1950's, i t was l e f t to Young and McCarty (1969) to pioneer the exploration of the anaerobic f i l t e r ) , the vast majority of the studies have been based on i t s a p p l i c a b i l i t y to d i f f e r e n t wastewaters and very few devoted to s p e c i f i c features of the f i l t e r . Limited information i s therefore available on nutrient requirements for b i o l o g i c a l treatment by the anaerobic f i l t e r . Since most l a n d f i l l leachates are c h a r a c t e r i s t i c a l l y low in phosphorus (P) and r i c h in nitrogen (N), phosphorus deficiency may place a l i m i t a t i o n on chemical oxygen demand (COD) removal. This study was i n i t i a t e d to determine the l i m i t a t i o n s on COD removal within an anaerobic f i l t e r due to the low concentrations of phosphorus in l a n d f i l l leachate. 2. RESEARCH OBJECTIVES Microorganisms involved in anaerobic processes, l i k e their aerobic counterparts, have been shown to require a s u f f i c i e n t supply of the essential nutrients P and N for uninhibited growth and consequent optimum digestion of the wastewater. L a n d f i l l leachate i s normally r i c h in nitrogen and d e f i c i e n t in phosphorus. Hence leachates low in phosphorus may be undergoing digestion by the anaerobic f i l t e r at sub-optimal conditions. If t h i s i s indeed the case, i t would seem that d i r e c t addition of phosphorus to the leachate would remove t h i s l i m i t a t i o n and l e t digestion occur at the true capacity of the f i l t e r . Hence th i s study was devoted to the following purposes: 1. To study the ef f e c t s of phosphorus addition on treatment c h a r a c t e r i s t i c s of the anaerobic f i l t e r . 2. To determine i f P deficiency imposed a l i m i t a t i o n on the COD removal capacity of the anaerobic f i l t e r . 3. To determine, i f possible, the COD:P r a t i o necessary for optimum treatment of l a n d f i l l leachate. 4 . To determine i f P addition enhanced any of the discrete steps involved in the digestion process. 3 3. LITERATURE REVIEW 3.1 MICROBIOLOGY OF ANAEROBIC DIGESTION Anaerobic digestion is a b i o l o g i c a l process in which organic matter i s converted to methane and carbon dioxide. It i s a three stage process involving, normally , three groups of microorganisms. The stages are hydrolysis, acid production and methane production. 3.1.1 HYDROLYSIS In t h i s phase, the insoluble portion of the complex organics i s hydrolyzed by b a c t e r i a l e x t r a c e l l u l a r enzymes to simple soluble compounds.Celluloses and starches are hydrolyzed to simple sugars; proteins are hydrolyzed to amino acids. Fatty acids are the only compounds that are not attacked by these e x t r a c e l l u l a r enzymes. These s o l u b i l i z a t i o n reactions proceed fast enough to prevent t h i s step from l i m i t i n g the rate of the o v e r a l l anaerobic digestion process (Bailey and 011is,l977) unless l i p i d s form a major portion of the waste (Kennedy and van den Berg, 1981 ).. 3.1.2 ACID PRODUCTION In t h i s stage, long chain fatty acids, amino acids and carbohydrates are fermented to form shorter chain fatty acids, hydrogen and carbon dioxide. In a stable anaerobic system t h i s results in the production of, mainly acetic 4 5 acid, and propionic and other v o l a t i l e fatty acids in smaller proportions. Production of propionic acid or any of the higher fatty acids in comparable quantity is a sign of i n s t a b i l i t y (Kennedy and Van den Berg, 1982). The acid production step proceeds faster than the next step, the methane production step. This means that a sudden increase in e a s i l y degradable organics w i l l result in increased acid production leading to an accumulation of acids which can i n h i b i t the methane production step. 3.1.3 METHANE PRODUCTION The various possible pathways of methane production from a complex waste are presented in Figure 3.l(Emcon Associates, 1980). As can be readily observed from the figure, more than 70% of methane i s produced via the methyl group of acetic acid. CH 3 COOH = CH 4 +C02 Propionic acid accounts for 30% of methane production with 17% of t h i s coming from acetic acid as an intermediary. In effect therefore, 85% of the t o t a l methane produced (13% d i r e c t l y from propionic acid and 72% from acetic acid as intermediary) i s from one of propionic or acetic acids and only 15% from other intermediates. Hence the importance of the groups of bacteria catabolizing acetic and propionic acids i s readily obvious. These bacteria also happen to be the slowest growing and the most sensitive to environmental changes. 6 FIGURE 3.1: PATHWAYS FOR METHANE FERMENTATION OF COMPLEX WASTES (Emcon Associates, 1980) 7 3.2 SUSPENDED AND ATTACHED GROWTH SYSTEMS Anaerobic processes may be divided into two classes depending on the mode of solids retention and biomass-substrate contact within the reactor.They are: 1. The suspended growth systems 2. The attached growth systems. Both systems are based on the proven rel a t i o n s h i p between solids retention time and e f f i c i e n c y of waste treatment(Garret and Sawyer ,1952). This was later borne out with s p e c i f i c reference to methane fermentation by studies which showed that washout of microorganisms u t i l i z i n g acetate, propionate and butyrate occurred with c e l l retention times of about 4 days at 35°C (McCarty, 1966; Lawrence and McCarty, 1969). The suspended growth system r e l i e s on some form of secondary c l a r i f i c a t i o n and recycle of s e t t l e d biomass. Examples of thi s system are the anaerobic contact process, the anaerobic c l a r i g e s t e r and the upflow anaerobic sludge blanket. The contact process provides for biomass-substrate contact by means of mechanical mixing. The anaerobic c l a r i g e s t e r and the upflow anaerobic sludge blanket provide t h i s function by virtue of the feed having to pass through a thick sludge layer in the lower half of the reactor. The attached growth system r e l i e s on one or both of a fi x e d - f i l m attached to a f i l t e r medium and s o l i d s retained in the void spaces within. The effluent i s recyled to the influent tank only i f pH or t o x i c i t y problems aris e or in the case of expanded and f l u i d i z e d 8 beds, to provide expansion of the f i l t e r bed. Examples of thi s system are the upflow anaerobic f i l t e r , the downflow stationary f i x e d - f i l m reactor, the moving bed, the expanded bed, the f l u i d i z e d bed and the recycled bed . 3 . 3 T H E A T T A C H E D GROWTH S P E C T R U M 3.3.1 THE FIXED BED (UPFLOW AND DOWNFLOW ANAEROBIC FILTERS) The downflow and upflow reactors, named after the di r e c t i o n of flow of wastewater, are examples of the fixed bed reactor. The main difference between the two modes i s that, in the upflow mode, a large proportion of the biomass is present as i n t e r s t i t i a l s o l i d s within the f i l t e r bed and a smaller proportion as f i x e d - f i l m whereas -the downflow mode is r e s t r i c t e d to the l a t t e r . This places a serious l i m i t a t i o n on the loading rate of the downflow f i l t e r and therefore r e s t r i c t s i t s a p p l i c a b i l i t y to lower organic loadings (Kennedy and van den Berg, 1982a, 1982b, 1982c, I982d). The upflow f i l t e r , on the other hand, i s well suited to high organic loadings (up to 30 kgCOD/m3.day). 3.3.2 THE MOVING BED (E.G.,THE ROTATING BIOLOGICAL  CONTACTOR) In t h i s type, microorganisms are attached to an inert media, which i s moved through the wastewater. Excess sludge leaves the reactor together with the treated wastewater. 9 3.3.3 THE EXPANDED BED This set-up consists of microorganisms attached to an inert support media such as sand, gravel, anthracite or p l a s t i c . A high degree of recycle keeps the biofilm-covered media expanded to' provide good biomass-substrate contact. Sludge in excess of that required for maximum treatment may be withdrawn from any place within the bed. 3.3.4 THE FLUIDIZED BED The f l u i d i z e d bed i s very similar to the expanded bed except that a much higher recycle r a t i o keeps the bed p a r t i c l e s f l u i d i z e d , thereby making for even better biomass-substrate contact than the expanded bed.Excess sludge may be drawn off from the bed regeneration stream taken out from the top of the bed where the bi o f i l m tends t.o have maximum thickness (Henze, 1983). 3.3.5 THE RECYCLED BED In t h i s form of attached growth reactor, suspended floes and biofilm-covered media in the effluent stream are set t l e d out in a c l a r i f i e r and recycled back to the reactor. Excess sludge may be drawn off from the recycle pipe. 10 3.4 OPERATIONAL CHARACTERISTICS OF ANAEROBIC FILTERS 3.4.1 FILTER START-UP Anaerobic processes have always been prone to problems of slow start-up and the anaerobic f i l t e r i s no exception. However, the a v a i l a b i l i t y of microbial culture grown on the waste in question cuts the start-up period by a considerable length of time(Young and McCarty, 1969,'Chian and de Walle, 1977). Young and McCarty(1969) found that heavy bottom seeding rather than l i g h t uniform seeding reduced the start-up period a good deal. Start-up period may also be shortened by providing temporary c l a r i f i c a t i o n and recycling of s e t t l e d biomass. Benjamin et al.(198l) found that increasing the organic loading on the f i l t e r in steps helped in minimizing start-up time. Henze(l983) recommends that during start-up,loading should be approximately 0.1 kgCOD/kgVSS.day corresponding to 1-2 kgCOD/m3.day for a reactor with a biomass concentration of 10-20 kgVSS/m3 and when gas production increases, the load should be increased in steps of 50% every week. VFA should be monitored and i f increased le v e l s are observed (>1.0—1.5 kg as acetic acid/m 3), the loading should be reduced u n t i l the acids l e v e l goes down again. 3.4.2 THE FILTER MEDIA Since s o l i d s retention in the i n t e r s t i t i a l spaces is the predominant form of biomass retention within the f i l t e r 11 bed, the a b i l i t y of the f i l t e r to retain s o l i d s influences COD removal considerably more than the surface area provided for b i o f i l m formation (Young and Dahab, 1982a). F i l t e r beds with a larger modular media and smaller surface area were found to perform better than f i l t e r s with a smaller modular media and larger surface area, probably because the l a t t e r are prone to channeling problems (Young and Dahab, 1982). Van den Berg and Lentz(l980) found that clay media were better than p l a s t i c media in that the f i l m developed faster(1-3 months vs 7 months or longer), area loading rates were higher and the process was more stable. However, t h i s study found that high unit surface area afforded higher COD removal in contrast to Young and Dahab(1982)'s observation. 3.4.3 COD REMOVAL TRENDS Data from various studies on the e f f e c t of reactor height on treatment e f f i c i e n c y indicate that for equal loading rates and for a l l kinds of media, more e f f i c i e n t use of reactor volume i s made when shallow rather than t a l l reactors are used. Young and Dahab (1982b), concluded on reviewing a number of studies that the COD removal e f f i c i e n c y could be expressed (for reactors having heights in excess of about 1m and receiving organic loadings up to about 20 kgCOD/day.m3) as: E = 100 (1-V0) where, V = average upflow v e l o c i t y , 0, a reactor c o e f f i c i e n t = ©_ /H 1 2 where 6 T = proportionality c o e f f i c i e n t (Time) and H = reactor height Hence, COD removal e f f i c i e n c y i s inversely proportional to average upflow v e l o c i t y and strongly related to media type, represented by 0. The equation above, supported by data points from a number of studies, v e r i f i e s that waste concentration i s not a c r i t i c a l factor in determining COD removal e f f i c i e n c y . 3.4.4 SLUDGE WASTING Low net c e l l synthesis of anaerobic reactions and long SRT results in low net production of b i o l o g i c a l s o l i d s . Hence, f i l t e r s treating VFA based waste such as leachate may run for a considerable length of time (1 year or longer) before clogging and short c i r c u i t i n g occur. In general, however, proper media selection and a regular sludge wasting schedule should be given due attention to avoid these problems. 3.4.5 ENVIRONMENTAL FACTORS OF IMPORTANCE 3.4.5.1 TEMPERATURE The most common range for operation i s 30-40^ C (Henze, 1983). However, there have been a number of investigations (Kennedy and van den Berg, 1981 and 1982; Jorgensen, 1972) in the temperature range 10-35°C without major changes in the microbial ecosystem. It appears that, apart from the normal decrease in reaction rate due to a 13 lower temperature, there i s no serious loss of treatment e f f i c i e n c y at low temperature. Due to a high decay rate above 40°C, the observed y i e l d c o e f f i c i e n t of methane bacteria approaches zero and renders continuous operation d i f f i c u l t ( V a n den Berg, 1977). 3.4.5.2 pH Methane bacteria have their optimum pH in the 6 to 8 range (Zehnder et al.,1981) whereas acid formers have their optimum in the 5 to 6 range (Henze, 1983). Since methane formers are much slower growing than acid formers, i t i s recommended that the pH be maintained around 7 for ove r a l l e f f i c i e n c y . 3.4.5.3 NUTRIENTS The nutrients nitrogen and phosphorus are esse n t i a l to anaerobic treatment. If these are not present in required concentrations sub-optimum treatment may r e s u l t . Nutrient requirement as a function of organic loading may be calculated using the y i e l d c o e f f i c i e n t and may be represented in the form of a COD/N/P r a t i o . Van den Berg and Lentz (1977) observe that a COD/N ra t i o of 420/7 i s appropriate for high organic loadings (0.8-1.2 kgCOD/kgVSS.day). For low organic loadings (<0.5 kgCOD/kgVSS.day), the COD/N r a t i o increases sharply to 1000/7 or more.Speece and McCarty (1964) found that nitrogen and phosphorus content of the sludge was approximately 10.5% and 1.5% respectively. Hence, using a 1 4 N/P ra t i o of 7:1 and COD/N rati o s noted previously, a COD/P r a t i o between 1000:1 and 420:1 could be suggested. Apart from nitrogen and phosphorus, a number of other micronutrients are required. Amongst them i s n i c k e l , which i s usually present in most wastes in the trace concentrations necessary. In general, to eliminate the p o s s i b i l i t y of micronutrient deficiency, addition of standard nutrient s a l t s or yeast to the influent i s recommended (Henze,1983). 3.4.5.4 TOXICITY Like a l l other b i o l o g i c a l processes, the anaerobic f i l t e r i s prone to upsets by toxic substances. General b e l i e f has been that the process i s incapable of to l e r a t i n g transient and chronic toxicity,thus i n h i b i t i n g i t s application to many wastewaters. Contrary to the conventional theory of suspended growth systems, a number of studies on the response of attached growth systems to toxins (Chou et. a l . , 1979; Yang et. a l . , 1980) have indicated that the merits of suspended and attached growth systems are quite comparable in thi s regard. In addition, Parkin and Speece (1982) observed that the high sludge retention and the plug flow mode of operation which passes slug doses of toxins quickly make the anaerobic f i l t e r more tolerant of transient t o x i c i t y than suspended growth reactors. Parkin and Speece (1982) conducted experiments with cyanide, chloroform, formaldehyde, ammonium, nickel and sulphide to evaluate the responses of an anaerobic 1 5 f i l t e r and a suspended growth reactor to transient and chronic t o x i c i t y . Transient t o x i c i t y , measured by the magnitude of decrease in methane production, was found to be a function of toxin type, concentration and duration of exposure in both reactors. Recovery of the anaerobic f i l t e r was complete in the case of cyanide and ammonium, but recovery from the other toxins was e r r a t i c and incomplete. The outstanding feature observed was the difference in downtime (defined as the period of zero or decreased gas production) between the anaerobic f i l t e r and the suspended growth reactor. For instance, addition of 5 ml/1 cyanide to the suspended growth reactor resulted in a downtime of about 29 days while the addition of 10 ml/1 to an anaerobic f i l t e r showed no noticeable e f f e c t . The answer to chronic t o x i c i t y appears to l i e in proper acclimation to the toxin in question. E f f i c i e n t COD removal was found to be achieved in both reactors in the presence of toxin concentrations which were 20-50 times greater than the toxin concentration which exhibited 50% i n h i b i t i o n to unacclimated methanogens. 3.4.5.5 SHOCK LOADS Young and McCarty (1969) report that the anaerobic f i l t e r exhibits remarkable capacity to accept high shock loads. Doubling the organic loading had l i t t l e adverse impact on the COD removal (92%), and gas production s t a b i l i z e d within a few days. When the loading was doubled again, bringing the l e v e l to four times that in the 1 6 i n i t i a l phase of operation, methane production s t a b i l i z e d after 20 days but COD removal dropped to 60% with a pronounced r i s e in effluent suspended s o l i d s , indicating there appears to be a p r a c t i c a l l i m i t beyond which solids wasting from the f i l t e r bed and/or c l a r i f i c a t i o n should be performed to improve effluent q u a l i t y . 3.4.5.6 INTERMITTENT LOADS The anaerobic f i l t e r has been known to completely recover i t s COD removal e f f i c i e n c y within a few days of restoring feed after stoppage for 14 days. Young and Dahab (1982b) report that an anaerobic f i l t e r treating a milk waste, which was shut down for 6 months, recovered almost completely within 24 days of r e s t a r t . Rapid restart within 1-4 months of inoperation has also been reported when treating potato wastes (Taylor, 1972). Hence, i t would seem that the anaerobic f i l t e r i s well suited for industries producing wastes on an intermittent basis. 1 7 3.5 ENERGY RECOVERY The t h e o r e t i c a l amount of methane that can be produced in anaerobic systems i s about 350 l i t r e s / kg COD destroyed, i f a l l the COD i s converted to methane based on the following emperical equation: C n H a °b = (n/2-a/8+b/4)C0 2 + (n/2+a/8-b/4)CH4 Genung et. a l . (1982) report that 360 l i t r e s of methane per kgCOD destroyed were produced in an anaerobic f i l t e r treating municipal wastewater. Most reports c i t e values in the range 350-425 litres/kgCOD destroyed. Hall and Mercer (1982) constructed a cost comparison with an aerobic activated sludge treatment plant for pretreatment of a 5000 mg/l COD waste with a flow rate of 1360 m3/day. The results indicate that the anaerobic f i l t e r technology has the potential to recover enough energy to cover annual operation and maintanance costs adequately . Since the difference i s primarily a function of energy costs, the advantages of anaerobic over aerobic treatment are l i k e l y to grow. 3.6 VAR IETY OF WASTES TREATED BY THE ANAEROBIC F I L T E R Starting with the study by Young and McCarty (1969) on the treatment of a protein-carbohydrate mixture, a wide variety of wastes, including domestic and i n d u s t r i a l have been treated by the anaerobic f i l t e r . Treatment of domestic wastes by the anaerobic f i l t e r has met with rather moderate success (Genung et. a l . , 1982; Raman and Chakladar, 1972a, 18 1 9 7 2 b ) . Henze ( 1 9 8 3 ) points out that low temperatures ( < 3 0 ° C ) found in municipal wastewater i s the reason for poor soluble organics removal. However, innumerable i n d u s t r i a l wastes have been treated succesfully by the anaerobic f i l t e r . The l i s t includes dairy wastes, milk wastes, d i s t i l l e r y wastes, malting wastes, food wastes, piggery wastes, cow manure, molasses, s u l f i t e evaporator condensate, pulp and paper m i l l wastes, chemical wastes, t e x t i l e wastes and l a n d f i l l leachate(Henze,1983). In general, i t would seem that most any soluble waste may be successfully treated by the anaerobic f i l t e r and those with a COD l e v e l of 1 0 0 0 - 2 0 0 0 mg/l or greater are i d e a l l y suited. 4. EXPERIMENTAL PROCEDURE 4.1 LEACHATE COLLECTION AND HANDLING Leachate used in t h i s study was obtained from Premier l a n d f i l l , a municipal waste l a n d f i l l , which services the Vancouver North Shore . The Premier l a n d f i l l leachate has been the subject of several investigations at the University of B r i t i s h Columbia. Current work includes an on-site p i l o t - s c a l e RBC(rotating b i o l o g i c a l contactor) treatment and a study of the possible e f f e c t s of glucose addition on the start-up period of a lab-scale anaerobic f i l t e r at rooom temperature. The Premier l a n d f i l l produces upto 1600 m3/day of leachate and the l a n d f i l l s i t e covers an area of 100,000 m2 out of which 40,000 m2 are being a c t i v e l y f i l l e d . The leachate was co l l e c t e d in polyethylene containers of 20L capacity once a month and subsequently stored in large drums at 4°C. Analysis to determine the COD of the leachate was done within one or two days. Due to s i t e variations which affect chemical c h a r a c t e r i s t i c s of leachate, such as r a i n f a l l , the organic strength varied considerably over the study period. The COD varied from 150 to 4200 mg/L with a BOD/COD r a t i o of 0.48-0.55. In order to compare data with those obained in studies elsewhere, i t was decided to l i m i t the minimum strength of the influent to about 2000 mg/l COD. Whenever the leachate strength f e l l below 2000 mg/l COD, required amount of sodium acetate was added to raise the strength to about 2000 mg/l COD. Phosphorus was added in 19 20 required amounts to the influent to reactor 2 in runs 2, 3 and 4 only at the time of feed addition to influent tank. The feed thus obtained after phosphorus and acetate addition is henceforth referred to as leachate feed. Analyses for a l l parameters which describe the general character of the leachate feed, except heavy metals, were conducted over the following week. Samples for heavy metals analysis were a c i d i f i e d and stored for analysis over the following month. Table 4.1 l i s t s the c h a r a c t e r i s t i c s of the leachate feed. 4.2 EXPERIMENTAL SET-UP Two i d e n t i c a l lab-scale f i l t e r s (0.975 metres x 0.150 metres diameter) were constructed out of plexiglass pipes. One f i l t e r was to be the study control with the other subject to phosphorus addition. Provision was made for sampling within the reactors by means of three sampling ports (see Figure 4.1). A perforated aluminum b a f f l e plate was placed near the bottom of the reactor to help d i s t r i b u t e the influent evenly across the cross-sectional area of the f i l t e r . The study of various media types and their influence on so l i d s retention capacity and COD removal e f f i c i e n c y done by Young and Dahab (1982) indicates that modular corrugated blocks used as media have superior c h a r a c t e r i s t i c s in both respects. Hence, s t r i p s of corrugated fiberglass roofing sheets were cross-stacked at 45° and stuck together at 21 Table 4.1 Leachate Feed Characterisics PARAMETER RANGE LEACHATE LEACHATE FEED pH 6.6-7.8 6.6 - 7.8 A l k a l i n i t y (mg/L) N.A. 1 800 - 1200 Total Solids (mg/L) N.A. 140 -190 V o l a t i l e Solids N.A. 50 - 80 (mg/L) COD (mg/L) 150-4200 1800 - 4200 BOD (mg/L) 75-2700 1200 -2700 TOC (mg/L) N.A. 800 - 1425 BOD/COD 0.48-0.55 0.48 - 0.85 V o l a t i l e Fatty N.A. 1360 - 2075 Acids (mg/L) TKN2 (mg/L) as N N.A. 36-153 TP (mg/L) as P B.D.L.3 B.D.L.- 49 Temperature (°C) N.A. 19.0 - 20.5 Heavy Metals Fe (mg/L) N.A. 7.6 - 68.83 Mn (mg/L) N.A. 1.27 - 9.93 Zn (mg/L) N.A. 0.01 - 2.05 1 Not Available 2 Total Kjeldahl Nitrogen 3 Below Detection Limits FIGURE 4.1 i EXPERIMENTAL S E T UP. 23 contact points to form a modular f i l t e r medium. The media was placed in four layers to form the complete f i l t e r bed. The void volume of the f i l t e r bed is 13.5 l i t r e s (0.0135 m2) with a porosity of 0.93. The t o t a l surface area of the media in each reactor is 11.1658 m2 with a s p e c i f i c surface area of 80 m2/m3. A p e r i s t a l t i c pump with two heads was used to pump the feed into the two reactors. A timer (with a 15-min on, 15 min-off cycle) was used in conjunction with the pump speed c o n t r o l l e r to maintain an average flow rate of 13.5 l i t r e s / d a y (0.0135 m 3). Mixers were i n s t a l l e d in each influent tank to keep the contents s t i r r e d continuously. Gases given off during anaerobic treatment of the leachate feed were channelled from the top of the reactor through a gas meter and a gas sampling device before being vented away to the atmosphere. 4.3 FEED SCHEDULE Whenever necessary, as discussed in section 4.1, sodium acetate was added to the drums containing leachate and mixed thoroughly by means of a submersible pump. S u f f i c i e n t quantity of leachate feed was added everyday to the influent tanks to make sure that they never ran dry and a i r was never pumped through the anaerobic systems. At feed time, leachate feed was drawn off from a drum after mixing the contents of the drum in order to maintain uniformity of the feed through the month. Although the feed was at 4°C when just out of 24 low-temperature storage room, the mixing of fresh feed with the exi s t i n g contents of the influent tank and the low flow rate allowed for s u f f i c i e n t detention at room temperature before being pumped into the reactors.. Phosphoric acid solution was added in required proportion d i r e c t l y to the influent tank. 4.4 FILTER START-UP In accordance with the studies quoted in section 3.5.1, the two f i l t e r s were seeded with about two l i t r e s of sludge co l l e c t e d from a lab-scale anaerobic digester operating on leachate from the same l a n d f i l l . Steady COD removal e f f i c i e n c i e s , gas production, methane content in gas and pH were used as indicators of steady-state. Once the reactors attained steady-state, run 1 was begun at DAY 1. Each run was conducted for a s u f f i c i e n t length of time to allow the parameters studied to steady out. This practice made for the c o l l e c t i o n of data r e f l e c t i n g the features of the new run accurately. The leve l s of phosphorus addition and the length of each run are l i s t e d in Table 4.2. 4 . 5 SAMPLING SCHEDULE Grab samples were c o l l e c t e d from the influent tanks in the middle of the mixing cycle. Effluent samples were co l l e c t e d from the respective effluent l i n e . The sampling schedule, s t a r t i n g at DAY 1 i s shown in Table 4.3. The t o t a l phosphorus l e v e l in the leachate was below detection l i m i t s Table 4.2 Experimental Schedule 25 RUN FROM TO P ADDED TO NUMBER (DAY) (DAY) REACTOR #2 (mg/L) 1 1 50 0 2 50 98 10 3 98 130 30 - 50 4 130 162 10 5 162 177 0 26 Table 4.3 Sampling Schedule PARAMETER TYPE of SAMPLE FREQUENCY TSS/TVSS U 1 Once every two weeks COD U + F 2 Once every two days BOD F Weekly TP and TKN U For Reactor 1, Once every 4 days For Reactor 2, Once every 2 days A l k a l i n i t y U Weekly PH U Twice a week Methane Content Gas From Twice a week In Off Gas Gas Sampler 1 U n f i l t e r e d Sample 2 F i l t e r e d Sample 27 during the period of the study, sampling for TP and TKN were done less frequently in reactor 1 (once every 4 days for reactor 1 as compared to once every 2 days for reactor 2) which did not receive any phosphorus addition. 5. EXPERIMENTAL METHODS Analysis for s o l i d s , a l k a l i n i t y , COD, BOD and heavy metals were carried out in duplicate in accordance with "Standard Methods" (1980). Mercuric sulphate was added to samples for COD determination to prevent interference from chloride. At least three d i l u t i o n s of each sample were used for BOD determination. Analyses for heavy metals were conducted using the J a r r e l Ash Model 810 Atomic Absorbtion Spectrophotometer . The pH meter used was a Fisher Accumet Model 320 Expanded Scale Research pH meter. V o l a t i l e Fatty Acids were determined according to the method s p e c i f i e d by SUPELCO,INC using a 60/80 carbopack C/0.3% carbowax 20M/0.1% H 3 P0 4 packing for the column. Samples - for TP and TKN analyses were subjected to a preliminary digestion step with the block digester method using sulphuric acid. The digested samples were then analysed using a Technicon Autoanalyser 2 . Total Phosphorus was analysed by modified Technicon method #327-74w and TKN using #321-74W. The gas meter used in the determination of gas quantities was a wet type gas meter M75-INS (Alexander Wright & CO. Ltd., U.K.). Gas composition was determined using a Fisher Hamilton Gas Partitioner with a 3380A Hewlett Packard Integrator. 28 6. RESULTS 6.1 S T E A D Y S T A T E After nearly twelve weeks of continuous operation, steady state was reached. COD removal e f f i c i e n c y was in the 60-70% range for both reactors. TSS in the effluents from reactor 1 and reactor 2 were =60 mg/L and =90 mg/L respectively. Total gas production in both reactors had increased to above 6.5 l i t e r s / d a y and methane content in the off-gas had steadied out at =90%. This marked the beginning of detailed analysis with DAY 1. The reactor u n f i l t e r e d and f i l t e r e d COD influents and effluents and COD removal e f f i c i e n c i e s are presented in figures 6.1,6.2 and 6.3 respectively. The plots of gas production and methane y i e l d are shown in Figures 6.4 and 6.5 respectively. BOD removal e f f i c i e n c y , influent and effluent TP and TKN leve l s are presented in figures 6.6,6.7 and 6.8 respectively. S t a t i s t i c a l analyses were conducted to determine the s i g n i f i c a n t difference, i f any, between the COD destroyed in the two reactors. The COD destroyed per day in passage of feed through each reactor was calculated for each sampling day by taking the difference of the influent and effluent COD's and integrating i t over a 24 hour period, applying the average flow rate of 13.5 l i t r e s per day. For the purpose of estimating the s t a t i s t i c a l l y s i g n i f i c a n t difference, a ' t ' d i s t r i b u t i o n of the data was assumed since the the sample size in a l l runs was less than 30. The 29 30 UNFILTERED COD VS TIME 4200-4200-3700 3200 \ 2700r cn J , Q 2200 O o 1700-1200 700 31 41 51 61 Days In Steady State P Added 30-50 mg/l Legend K Reoctori (iNf) x ReoctorKEfT) v R«ocior2 (err) X X , P Addition Slopped OPtRATlOK WTERRUPTOH DAT 10610 IK 1 U$ P Added 10 m g / l 103 113 123 133 143 153 163 173 Days In Steady State FIGURE 6.1 UNFILTERED COD VS TIME FILTERED COD VS TIME 31 21 31 41 51 61 71 81 Days In Steady State P Added 10 mg/l Legend * R«oclor1 (INF) O Peactor2 I^Nf^ x ReoctorJJEFF) 7 R«aclor2 (CFF) \ O P E R A T I O N M T C R R U P T I O N DAT IQ610116 91 103 113 123 133 143 153 Days In Steady State 163 173 FIGURE 6.2 FILTERED COD VS TIME COD REMOVAL EFFICIENCY tOO T 90 80 70 & 60H u § 50-w 40 L U P Added 10 m g / l 30 20' 10-"T" 11 41 —r* 51 Legend X R«oc1or 1 A Rtoctor 2 21 31 Days In Steady State T-61 71 81 100 90 80 70 60->» o c 50 -40-Ui 30 -20-10-OPtRAt lOHIKl tRRUPIION DAT » 6 TO 116 I ***** X x P A d d e d 30-50 mg/l P Added 10 m g / l P Addition Stopped Legend x R«octor 1 • i • 99 149 i ' ' ' ' l ' ' 159 169 109 119 129 139 Days In Steady State FIGURE 6.3 COD REMOVAL EFFICIENCY METHANE PRODUCTION VS TIME P Added 10 mg/ l O P E R A T I O N I N T E R R U P T I O N D A T 1 0 8 T O I I S P Added 30-50 mg/l P Addiiion Slopped P Added 10 mg/l Legend A Reaclor 1 X Reactor 2 M " " I • 1 , 1 1 1 1 1 • I " " I1 • 1 1 i ' 1 " I " " I ""I""!""!""! 1 1 1 1 ! I 11 21 31 41 51 61 71 81 91 101 111 121 131 U1 151 161 171 Days In Steady State FIGURE 6.4 METHANE PRODUCTION VS TIME 34 METHANE YIELD VS TIME 500 480-Tl 460->» O u 440-"w <o 420-Q Q 400-O O 380-CO .X 360-V. 340-CD CL • Q) 320 J C D £: 300-"a> 280-OT 260-ID 240-'3 220-P Added 30-50 mg/l Legend A REACT0R1 X REACT0R2 0 P [ R A I I 0 H 1 K T [ R R U P T I 0 H O A T W 6 T O 116 I P Addition Slopped 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171 Days In Steady State FIGURE 6.5 METHANE YIELD VS TIME BOD REMOVAL EFFICIENCY 100 90 H 80 70 H 60^ >» u c 50 .2 S io 30 20 10 4 i i P Added P Added P Added P Addition 10 mg/ l 30-50 mg/l 10 mg/l Stopped Legend x Reoctor 1 A Reoclor 2 10 13 16 19 22 Weeks ln Steady State FIGURE 6.6 BOD REMOVAL EFFICIENCY T 25 36 TOTAL KJELDAHL NITROGEN VS TIME CO J , c OJ CO o o SL ,0 160-150-140-130-120-110-100-90-80-70-60-50-40-30-20 10 Legend X Raoclorl (INQ x Reaclorl_(EPT) v R « o c i o r 2 (err) 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 Days In Steady State FIGURE 6.7 TOTAL KJELDAHL NITROGEN VS TIME TOTAL PHOSPHURUS VS TIME ft / ?6 It! O P E R A T I O N I N T E R R U P T I O N O A T 1 0 6 T 0 1 1 5 Legend * R « o c l o d (INF) O R e o c l o r 2 J[INF^  X ReaclorjJErF) V R « o c l o r 2 (EFF) J> 1f.< i M i |>d i > ( | 1 X 1 ' ) ; ( • i M ' | V < i M | • > ' • • " > ; « • . . ? . ( • | > ' i i > < | > M i ')|0 i M . |)d •)•( 59 69 79 89 99 109 119 129 139 149 159 169 Days In Steady State FIGURE 6.8 TOTAL PHOSPHURUS VS TIME 38 confidence l e v e l employed was 95%. The parameter i/d expresses the interval in which the s t a t i s t i c a l l y s i g n i f i c a n t difference for a confidence l e v e l of 95% l i e s . Results of these analyses are summarized in Table 6.1. 6.2 RUN 1 (DAY 1 TO DAY 49) The effluent from reactor 1 was consistently superior in terms of COD throughout th i s run. The influen.ts to the reactors being the same in quantity and c h a r a c t e r i s t i c s , reactor 1 was therefore better in terms of COD removal e f f i c i e n c y and mass of COD destroyed (200 x I0~ 6kg/day < fid < 629 x I0~ 6kg/day). The BOD removal e f f i c i e n c y trend confirms that reactor 1 had superior b i o l o g i c a l c h a r a c t e r i s t i c s (difference of 2-9%). Phosphorus (measured as TP) in the leachate was found to be below detection l i m i t s in a l l batches of leachate used in the study, thus eliminating the need for frequent monitoring of TP in the influent and effluent from both reactors in th i s and run 5 and in the influent and effluent from the control reactor for the rest of the study. It would seem that in spite of the e f f o r t s to develop equivalent b i o l o g i c a l systems in the two reactors, reactor 1 turned out to be superior. It was decided to use the superior system (reactor 1) as control, so that any improvement in performance of reactor 2 could be convincingly demonstrated in d i r e c t comparison with reactor 1 . 39 Table 6.1 Results of S t a t i s t i c a l Analyses on COD Data P No. of Data M d 1 Run # Added Points per {REACTOR 1}-{REACTOR 2} mg/L Reactor (kg COD destroyed/day) x 10"6 1 0 25 200 < M d < 629 2 10 24 494 < M d < 756 3 30-50 1 2 -3403 < jud < -4847 4 10 16 -154 < M d < 887 5 0 7 -59 < M d < 421 1 95% confidence in t e r v a l for the s i g n i f i c a n t difference between data for reactor 1 and reactor 2 measured as {REACTOR 1} - {REACTOR 2}. Note: Each COD determination was ca r r i e d out to an accuracy of 18.0±18.6 mg/L. 40 6.3 RUN 2(DAY 50 TO DAY 98) Addition of phosphoric acid to the feed tank for reactor 2 was found to cause chemical p r e c i p i t a t i o n res u l t i n g in removal of 20-200 mg/L COD from the feed. Effluent from reactor 2 improved and became better than effluent from reactor 1 by 50-200 mg/L COD . The BOD removal e f f i c i e n c y of reactor 2 was better by 2-6%. However the amount of COD destroyed in reactor 1 continued to be higher than in reactor 2 (474 x I0~ 6kg/day < uo\ < 755 x I0~ 6kg/day), thus contradicting the trend shown by the COD removal e f f i c i e n c i e s alone. This i s explained by the pr e c i p i t a t i o n of 20-200 mg/L of COD in the feed tank to reactor 2 on addition of phosphoric acid. Total Phosphorus l e v e l s in the feed tank to reactor 2 were in the range 8.6-12.6 mg/L due to phosphorus addition. The TP l e v e l in the effluent from reactor 2 was in the range 3.8-8.8 mg/L giving a range of 1.6-6.4 mg/L for phosphorus used in passage through the reactor. The amount of TKN used up in reactor 2 was generally higher than in reactor 1 (Figure 6.7). 6.4 RUN 3(DAY 98-DAY130) The beginning of run 3 coincided with a sharp increase in the strength of the leachate to about 4000 mg/L COD. Therefore, to double the P/COD r a t i o in order to proceed to the next l e v e l of phosphorus addition, the P added had to be increased to =*40 mg/L. This resulted in increased chemical 41 p r e c i p i t a t i o n and removal of 100-350 mg/L COD. Run 3 marks a d i s t i n c t l y d i f f e r e n t trend from run 2 in terms of COD and BOD removal e f f i c i e n c i e s . The effluent from both reactors had deteriorated considerably from the previous run to >1400 mg/L COD, quite possibly due to the near doubling of organic loading to 4.0 kgCOD/m3.day. Reactor 2 continued to produce better q u a l i t y effluent than reactor 1, only the difference increased to 300-600 mg/L. COD removal e f f i c i e n c i e s in the reactors registered a sharp decrease to the 55-65% range. COD destroyed in reactor 2 was greater compared to reactor 1 by 3403 x 10"6kg/day < nd <4847 x I0" 6kg/day. BOD removal e f f i c i e n c y trends (58-70% for reactor 1 vs 66-77% for reactor 2) confirmed that reactor 2 ihad performed better than reactor 1. Total phosphorus levels in the feed tank to reactor 2 were in the range 30-49 mg/L. The effluent TP l e v e l in reactor 2 was in the range 14-27 mg/L, giving a range of 12-34 mg/L for phosphorus used in passage through the reactor. The influent TKN increased with the sharp increase in COD, to about 150 mg/L. The influent and effluent TKN level s do not show a s p e c i f i c trend regarding the TKN used in the reactors. 6.5 RUN 4(DAY 130 - DAY 162) The COD of the leachate dropped to below 2000 mg/L and was made up to about 2000 mg/L by adding sodium acetate. The phosphorus addition was reduced to 10 mg/L to match the 42 P/COD ra t i o in run 2, resu l t i n g in COD removal trends reverting to those seen in run 2. The BOD removal data does not allow for the determination of a s p e c i f i c trend, b a s i c a l l y because of fewer data points than run 2. The amount of COD destroyed/day was higher (as in run 2) in reactor 1 (-154 x I0~ 6kg/day < nd < 887 x I0" 6kg/day). Therefore chemical p r e c i p i t a t i o n was again the predominant eff e c t of phosphorus addition. TP levels in the feed tank to reactor 2 ranged from 9.2-11.5 mg/L. The effluent TP l e v e l in reactor 2 was in the range 5.0—10.2 mg/L giving a range of 1.3-4.8 mg/L for phosphorus used in passage through the reactor. The influent TKN remained at the high l e v e l of about 150 mg/L and the amounts of TKN used in the reactors do not show, as in the previous run, a s p e c i f i c trend. 6.6 RUN 5(DAY 162-DAY DAY 177) On day 162, run 5 was begun by stopping phosphorus addition to reactor 2. The reactors displayed a trend similar to that seen in run 1 with reactor 1 displaying marginally better treatment c h a r a c t e r i s t i c s than reactor 2. The amount of COD destroyed in reactor 1 was higher (-59 x I0~ 6kg/day < jud < 421 x I0~ 6kg/day) as in run 1. The in t e r v a l in which Md l i e s , displays a s h i f t to the negative range, c l e a r l y the result of data for day 165 when the difference the between the COD destroyed in the reactors was -202 X 10"6 kg/day. Neither BOD (due to fewer data points 43 than run 1) nor TKN data allowed for the determination of s p e c i f i c trends. 6.7 GAS PRODUCTION The methane component of the off-gas from both reactors was normally 90-92% and the quantity of methane produced varied from 4.5 to 10.0 l i t r e s per day. It can be seen from Figure 6.4 that the actual quantities of methane produced in the two reactors are clos e l y similar enough to be considered i d e n t i c a l . Peak methane production (-10 l i t r e s per day) occurred during run 3 when the leachate strength doubled to about 4000 mg/l COD. S t a t i s t i c a l analyses i d e n t i c a l to those described in section 6.1 were performed on the methane production data and the results are l i s t e d in Table 6.2. From t h i s table i t can be observed that during runs 1 and 2, methane production was s l i g h t l y greater in reactor 1, commensurate with the higher COD destroyed in those runs. During run 3, methane production was greater in reactor 2, but by a very small amount as compared with the high Md value obtained for the COD destroyed. Runs 4 and 5 are similar to runs 2 and 1 respectively, in that they display a range of po s i t i v e values for Md. An examination of Figure 6.5 reveals that the reactors displayed comparable methane y i e l d trends in a l l runs except run 3 when reactor 2 c l e a r l y lagged behind. 44 Table 6.2 Results of S t a t i s t i c a l Analyses on Methane Data P No. of Data M d 1 Run # Added Points per {REACTOR 1}-{REACTOR 2} mg/L Reactor ( l i t r e s CH4 produced/day) 1 0 25 -0.08 < jud < 0.29 2 10 24 0.02 < M<3 < 0.32 3 30-50 12 -0.20 < M d < -0.62 4 10 16 0.26 < MC3 < 0.42 5 0 7 -0.23 < ud < 0.75 1 95% confidence in t e r v a l for the s i g n i f i c a n t difference between data for reactor 1 and reactor 2 measured as {REACTOR 1} - {REACTOR 2}. 45 6.8 SOLIDS DATA The t o t a l suspended solids data is presented in Table 6.3. It can been seen that the interruption in operation from day 106 to 116 due to clogging of the f i l t e r bed in reactor 2 was preceeded by a sharp increase in the suspended so l i d s content of the ef f l u e n t . After day 49, the t o t a l suspended solids content of influent to reactor 2 was usually higher than reactor 1, probably due to the presence of phosphorus-related p r e c i p i t a t i o n f l o e s . The v o l a t i l e suspended solids to t o t a l suspended s o l i d s r a t i o of the influents and the effluents remained, with few exceptions, in the 3*6-49 % range throughout the study. 46 Table 6.3 Suspended Solids Data Reactor#1 Reactor#1 Reactor#2 Reactor#2 Day# Influent Effluent Influent Effluent 1 212 1 45 212 118 15 238 92 238 73 30 192 61 192 82 45 1 62 71 1 62 78 60 142 23 166 41 75 147 23 230 1 13 90 180 32 210 148 105 175 46 215 112 1 1 5 316 105 460 307 135 190 35 240 98 150 210 40 230 146 165 185 57 185 63 7. DISCUSSION OF RESULTS 7.1 P ADDITION AT THE 10MG/L LEVEL Phosphorus addition at 10 mg/l l e v e l in runs 2 and 4 indicated that the effect on the anaerobic f i l t e r was r e s t r i c t e d to chemical p r e c i p i t a t i o n and the b i o l o g i c a l system did not seem to be affected at a l l . P was not, therefore, l i m i t i n g COD removal under the retention time and loading conditions in th i s run. It would seem then, that for the waste used in th i s study, t h i s chemical related COD removal benefit may be gained from some other form of cheaper p r e c i p i t a t i o n , possibly lime. Therefore for the waste used in th i s study, P addition at the 10 mg/l le v e l would seem f u t i l e . A closer look at the anaerobic processes involved brings out some points regarding COD removal. As stated in Chapter 3, anaerobic processes ( l i k e aerobic processes) require a certain l e v e l of phosphorus and nitrogen for sat i s f a c t o r y microbial u t i l i z a t i o n of waste. Therefore the fact that enhancement of b i o l o g i c a l processes in the f i l t e r did not occur on P addition gives r i s e to two p o s s i b i l i t i e s : either the P added was not available for microbial digestion or the waste treated was e a s i l y biodegraded even with the trace amounts of P ava i l a b l e . The f i r s t p o s s i b l i t y would seem to be extremely remote with the residual P in the effluent in the range 3.6-8.4 mg/l, indicating that P available i s in excess of the amount used in passage through 47 48 the reactor. The second p o s s i b i l i t y i s best evaluated by examining the waste c h a r a c t e r i s t i c s and the mechanisms of COD removal in anaerobic processes. The important steps in waste reduction are hydrolysis, acid formation, reduction of longer chain acids to acetic acid and methane generation, in that order. The leachate feed used during the 10 mg/l P addition had a t o t a l VFA content of 1300-2000 mg/l (as acetic acid), v i r t u a l l y a l l of i t in acetic acid form. Hence the o v e r a l l COD removal can be affected to a s i g n i f i c a n t degree only at the acetic acid to methane conversion step. The COD destroyed rate (kg COD destroyed / day) was not affected to any extent in spite of the 1.6-6.4 mg/l P used. Since acetic acid was the predominant form of organics present, the sugars, proteins and other building blocks essential for biomass production have to be synthesized from acetic acid. To t h i s end, a large amount of energy w i l l have to be expended and hence, more of the COD reduced w i l l be converted to gas and energy and less to biomass. In other words, the y i e l d c o e f f i c i e n t would be much lower than i f the waste was more complex and provided readily available sugars and proteins for biomass synthesis. With the net phosphorus requirement being d i r e c t l y proportional to biomass production, the negligible phosphorus uptake in runs 2 and 4 as compared to run 3 is only to be expected. Therefore, i t seems reasonable to suppose that for a waste consisting predominantly of acetic acid, phosphorus requirements are low due to the higher energy production and lower biomass 49 synthesi s. 7.2 P ADDITION AT THE 40 MG/L LEVEL When the organic loading on the anaerobic f i l t e r s was doubled in run 3, the COD removal e f f i c i e n c y dropped from 65-75% to 50-60%. This would seem l i k e a small loss in e f f i c i e n c y considering the abrupt nature of the loading change. This supports observations quoted in Chapter 3 that the anaerobic f i l t e r i s excellent at handling shock loads. Reactor 2 was uniformly better than reactor 1 in terms of the amount of COD destroyed, indicating that P addition held out d e f i n i t e b i o l o g i c a l benefits. Again, as in runs 2 and 4, a look at the waste composition brings out some points. The leachate used for t h i s run had a very high COD (up to 4500 mg/l) and a r e l a t i v e l y low VFA content (around 1600 mg/l). Hence, in t h i s feed, the amount of organics to be hydrolysed and subsequently converted to acids, forms a large portion of the t o t a l COD. Therefore, unlike runs 2 and 4, the rate l i m i t i n g steps could be any of the steps mentioned previously. The enhanced b i o l o g i c a l treatment in reactor 2 means that one or more of these steps were possibly limited by the deficiency of phosphorus. A closer look at the nature of the VFA's reduced in the two reactors sheds some l i g h t on one of these steps, the conversion from longer chain acids to acetic acid, the precursor to methane formation. The VFA's in the influent consist of =1100 mg/l acetic acid and =*500 mg/l propionic acid. Hence, in order to achieve maximum 50 COD destruction, in addition to the complex organics conversion, the existing propionic acid has to be broken down to acetic acid before being converted to methane. Samples of effluent from the reactors show that the effluent from reactor 1 was low in acetic acid (=75 mg/l) and high in propionic acid (=400 mg/l), whereas effluent from reactor 2 was evenly divided between the two acids (130 mg/l each). This suggests the p o s s i b i l i t y that the step in which propionic acid i s broken down to acetic acid i s enhanced by phosphorus addition, contributing, at least in part, to the o v e r a l l COD removal. Kennedy and Van den Berg (1982c) suggest that low propionic l e v e l s in the reactor indicate b i o l o g i c a l s t a b i l i t y . Reactor 2, therefore, seems to have attained greater s t a b i l i t y , leading to greater e f f i c i e n c y in removing COD. A consideration of biomass production, as in runs with P = 10 mg/l, serves to explain the COD removal trends observed. The leachate feed used in run 3 was more varied and complex in nature than in other runs. This means that more of the sugars, proteins and other building blocks are readily available and less energy i s required for biomass synthesis. Therefore, one would expect that a r e l a t i v e l y larger proportion of the destroyed COD would be converted to biomass. Since the phosphorus uptake i s d i r e c t l y proportional to biomass synthesized, i t seems reasonable to suppose, on the basis of higher consumption of phosphorus in run 3, that t h i s may have indeed occurred. The suspended 51 s o l i d s data does not shed any l i g h t on t h i s supposition. 7.3 GAS PRODUCTION The methane y i e l d normally observed in t h i s study, (290-390 x 10"3 m3/kg COD destroyed) is similar to the range of 350-450 x 10"3 m3/kg COD destroyed reported for a variety of waste types (Henry et a l . , 1982; Genung et a l . , 1982). During run 3, actual methane production in reactor 2 i s greater than in reactor 1, but the difference between the reactors (0.02 l i t r e s < /id < 0.20 l i t r e s ) f a l l s considerably short of values predicted from COD destroyed data (1.45-2.06 l i t r e s / d a y ) . This would indeed be the case, i f , as suggested in section 7.2, a smaller proportion of the organics i s u t i l i z e d for energy and a higher proportion for biomass construction. A comparison of t h e o r e t i c a l and actual phosphorus consumption serves to support the theory of higher biomass synthesis in t h i s run. The extra COD destroyed in reactor 2 was in the 3400-4847 x 10"6 kg/day range. Assuming a CODrTOC r a t i o of 4:1, the corresponding TOC i s in the 850-1200 mg/day range. Therefore, for a P/biomass r a t i o by dry weight of 3% (Schroeder,1977), the t h e o r e t i c a l phosphorus requirement i s in the 25-36 mg/day range. The actual phosphorus consumption was much higher (162-408 mg/day), indicating that Phosphorus was l i k e l y not l i m i t i n g the conversion of COD to biomass. During runs 4 and 5, reactor 1 displayed better methane production c h a r a c t e r i s t i c s matching the trend seen in kg COD 52 destroyed data. 7 . 4 COD:P RATIO The COD:P ra t i o observed during run 3 for 60% COD removal e f f i c i e n c y was 333:1 to 114:1. As noted in Chapter 3, other researchers found that the required COD:P values are in the range 1200:1 to 100:1.. Therefore the range of COD:P values found in thi s study are in reasonable agreement with some of the values quoted. The best agreement was found with the study by van den Berg and Lentz (1977) who found that the COD:P ra t i o was 100:1 in treating bean blanching waste. The same study also found a value of 250:1 in treating rum s t i l l a g e by the anaerobic f i l t e r . The disagreement with other values may be due to one or any of a number of variations in experimental parameters such as HRT (20-30 days used in the study by van den Berg et a l . vs =1.0 day used in thi s day), temperature (29-35°C vs 22°C used in this study), chemical composition of the wastes (food processing wastes vs l a n d f i l l leachate), form of P addition (Na 2HPO„ or K2HPOu vs H 3PO„ used in t h i s study) and so on. Moreover, in treating pear peeling waste, potato wastes and rum s t i l l a g e , van den Berg et a l . added yeast extract to the waste and obtained lower P requirements, suggesting the p o s s i b i l i t y that a balanced supply of a l l nutrients (micro-and macro-) lowered the quantities of individual nutrients required for optimum digestion of wastes. 53 The r a t i o of COD:P quoted was obtained from run 3 when the loading was nearly doubled from the previous run in an abrubt manner. Hence, i t would seem l i k e l y that the sharp increase in biomass production neccessary to cope with the higher COD available for degradation may have caused the higher uptake. It should also be borne in mind that t h i s run lasted a short length of time and i t is l i k e l y that the stage when biomass would cease to be produced and lyses of c e l l s combined with a nominal uptake of P from solution would sustain substrate degradation, had not been reached. P consumed in run 3 includes the portion chemically precipitated. Also of relevance is the fact that phosphate phosphorus, only one of the d i f f e r e n t forms of phosphorus, was measured in the van den Berg studies, whereas in thi s study TP was measured, suggesting that just a phosphate measurement would possibly have indicated lower P requi rements. 7.5 T K N U P T A K E D A T A TKN uptake data did not display a detectable trend in any of the runs, except run 2, because of the small magnitude of the t y p i c a l difference between the influent and effluent l e v e l s . Since the trend seen in run 2 does not have the b e n i f i t of comparison with any other run, the TKN data ov e r a l l f a i l s to lend an insight into any of the other phenomena recorded in t h i s study. 54 7 . 6 TO ADD OR NOT TO ADD PHOSPHORUS The question of the need for phosphorus addition w i l l have to be addressed on a s p e c i f i c basis for each waste. The nature of the organics constituting the waste would influence the decision to a large extent. For a waste that has gone through the acetic acid production stage, phosphorus addition would seem to hold l i t t l e benefit. However, for a waste that i s more complex in terms of i t s COD forms, the e f f e c t s of phosphorus on the various steps from hydrolysis through acid production need careful consideration. It would seem that phosphorus addition holds out some d e f i n i t e advantages for wastes with a diverse organic nature. The answer would depend on a balanced consideration of economics and technological advantages gained. From what has been learned and discussed about phosphorus requirements for higher biomass synthesis, i t seems reasonable to suggest that phosphorus addition would be of great importance in the start-up period of an anaerobic system to accelerate production of biomass and thereby a t t a i n peak treatment e f f i c i e n c y sooner. 8. CONCLUSIONS 1. Phosphorus addition at the 10 mg/L le v e l (at a volumetric loading rate of 2.0 kg COD/m3/day) did not affect the b i o l o g i c a l system in the anaerobic f i l t e r at a l l . Extra COD removal was r e s t r i c t e d to chemical p r e c i p i t a t i o n on addition of phosphorus as phosphoric acid. 2. When the organic loading was doubled from 2.0 kg COD/m3/day to 4.2 kg COD/m3/day, the f i l t e r s were affected to a minor extent only, supporting the findings of studies elsewhere that the anaerobic f i l t e r i s well suited to shock and intermittent loading. 3. Phosphorus addition at the 40 mg/L l e v e l marked a disce r n i b l e improvement in b i o l o g i c a l performance, measured by the amount of COD removed and by BOD removal e f f i c i e n c y , indicating that phosphorus addition at th i s l e v e l did hold out some d e f i n i t e advantages. 4. For wastes which are varied and complex in the forms of organics present, such as the one applied in run 3, the greater proportion of the COD destroyed i s possibly u t i l i z e d for c e l l synthesis. Since b i o l o g i c a l phosphorus requirement i s d i r e c t l y proportional to biomass production, wastes of this type would be in greater need of phosphorus addition. 5. When phosphorus was added to the waste r i c h in v o l a t i l e fatty acids, especially acetic acid, the b i o l o g i c a l system showed l i t t l e response, indicating that since most of the COD reduced was converted into energy, phosphorus 55 56 requirements for energy production are in the range normally found in the leachate. 6. The COD:P rat i o observed during run 3 at an organic loading of 4.2 kg COD/m3 /day was in the 400:1.2 to 400:3.5 range. The higher P consumption in this run in comparison with runs 2 and 4 and the low increase in methane production corresponding to the higher COD destroyed in reactor 2 suggests that a r e l a t i v e l y large proportion of the COD destroyed was u t i l i z e d for biomass production and a minimal amount for energy requirements. 7. From run 3, in which leachate was applied at a high rate, i t seems possible that the step in which propionic acid i s converted to acetic acid en route to methane production i s enhanced by phosphorus addition . 8. Methane production for a given increase in COD destroyed is higher when the organic component of the leachate consists of just acetic acid than when the organics are more complex and varied in nature, because of higher energy requirements for c e l l production. 9. The methane y i e l d observed i s in good agreement with the range of values quoted in the l i t e r a t u r e . Feed used in runs 2 and 4, being v o l a t i l e f a t t y acids based, were more suited to energy prodution rather than biomass production. Hence, no change in methane y i e l d was observed during those runs. In run 3, however, methane y i e l d was s l i g h t l y lower in reactor 2, quite possibly due to the higher conversion biomass rather than to energy. Differences, i f 57 any, in the actual methane production between the reactors, could not be measured within the accuracy afforded by the gas meter employed. 9 . RECOMMENDATIONS 1. Direct phosphorus addition to waste applied to the anaerobic f i l t e r does hold out some advantages when the waste composition i s varied and complex in nature, but the improvement seen (=* 10% COD removal e f f i c i e n c y ) i s of such a magnitude that the decision to add phosphorus would be dictated by a balanced consideration of economics and technical advantages gained. 2. An extension of t h i s study to cover lower temperatures would be of pa r t i c u l a r value to leachate management shemes in Canada. 3.Studies may be pr o f i t a b l y conducted to determine the effects of addition of other forms of phosphorus, espe c i a l l y organic, which i s probably more e a s i l y u t i l i z e d by microorganisms. 4.It would be useful to determine the exact steps of the anaerobic process which require phosphorus addition. To this end, multi-stage anaerobic processes could be constructed and phosphorus usage in the various stages studied. 5.Presently, at the University of B r i t i s h Columbia, work i s in progress to evaluate the usefulness of glucose addition to an acetate-based leachate feed to decrease the start-up period of the anaerobic f i l t e r . The lab-scale anaerobic f i l t e r s used in the study by the author are being used in th i s study with one as control, receiving an acetate-based leachate and the other receiving a feed consisting of the 58 59 acetate-based leachate and glucose. Excess phosphorus(=25 mg/l) i s being added to the two influents to study the uptake c h a r a c t e r i s t i c s of the f i l t e r s during start-up. BIBLIOGRAPHY 1. Austin T.P., Thirumurthi D., Ramalingiah and S.Khakria (1984), "Aerobic/Anaerobic treatment of municipal l a n d f i l l leachate", Presented at the 7th symposium on wastewater treatment, Montreal. 2. Bailey J.E. and D.F. O l l i s (1977), "Biochemical engineering fundamentals", McGraw H i l l . 3. Benjamin M.M., Ferguson J.F. and M.E. Buggins (1981), "Treatment of sulphite evaporator condensate with an anaerobic reactor", TAPPI Environmental Conference, 1981, New Orleans. 4. Cameron R.D. and F.A.Koch (1980), "Trace metals and anaerobic digestion of leachate", Journal WPCF, Vol .52, No. 2. 5. Chian E.S.K. and F.B. de Walle (1976), "Sanitary l a n d f i l l leachates and th e i r treatment",Journal of the Environmental Engineering Divi s i o n , ASCE, Vol. 102, No. EE2. 6. Chian E.S.K. and F.B. de Walle (1977), "Treatment of high strength acidic wastewater with a completely mixed anaerobic f i l t e r " , Water Res.,V 15. 7. Chou W.L., Speece R.E. and R.H. Siddiqi (1979), "Acclimation and degradation of petrochemical wastewater components by methane fermentation", Biotechnology and Bioengineering symposium, 8, 391-414. 8. Emcon Associates, 1980. "Methane generation and recovery from l a n d f i l l s " , Prepared for Consolidated Concrete 60 Limited and Alberta Environment, Ann Arbor Science. 9. Garret M.T. and C.N. Sawyer (1952), "Kinetics of soluble BOD removal by activated sludge", Proceedings of the 7th Industrial Waste Conference, Purdue University, Lafyette, Indiana. 10. Genung R.K., Hancher C.W., Rivera A.L. and M.T. Harris (1982), "Energy conservation and methane production in municipal wastewater treatment using fixed-film anaerobic bioreactors",Biotechnology and Bioengineering Symposium, V 12. 11. Hall E.R. and H. Mercer (1982), "Energy recovery From wastewater by high rate anaerobic treatment", Presented at the Western Canada Water and Sewage Conference", Winnepeg, Manitoba, September 1982. 12. Henry J.G., Prasad D., Sidhwa R. and M.Hilgerdenaar (1982), "Treatment of l a n d f i l l leachate by anaerobic f i l t e r : Part 1: Laboratory Studies",Water P o l l . Res. J. Canada : Vol. 17. 13. M. Henze ( 1983), Editor, "Anaerobic treatment of wastewater in fixed-film reactors", Proceedings of a specialized seminar of the IAWPRC, Copenhagen, Denmark, 1982. H.J.B.Jorgensen (1972),"The Anaerobic treatment of leachate", M.Sc. Thesis, University of Wisconsin. 15.Kennedy K.J. and L. van den Berg (1981), "Effects of temperature and overloading on the performance of anaerobic f i x e d - f i l m reactors", Presented at the 36th 61 Industrial Waste Conference, Purdue University, Lafayette, Indiana. 16. Kennedy K.J. and L. van den Berg (1982), " S t a b i l i t y and performance of anaerobic fixed-film reactors during hydraulic overloading at 10 to 35°C, Water Res. 17. Kennedy K.J. and L. van den berg (1982a), "Anaerobic digestion of piggery waste using a staionary f i x e d - f i l m reactor", A g r i c u l t u r a l Wastes, vol 4. 18. Kennedy K.J. and L. van den Berg (1982b), "Effect of height on the performance of anaerobic downflow stationary f i x e d - f i l m (DSFF) reactors treating bean blanching waste, Presented at the 37th Purdue Industrial Waste Conference, Purdue University, Lafayette, Indiana. 19. Kennedy K.J. and L. van den Berg (1982c), "Thermophilic downflow stationary f i x e d - f i l m reactors for methane production from bean blanching waste", Biotechnology Letters, vol 4(3). 20. Kennedy K.J. and L. van den Berg (I982d), "Continuos vs slug loading of downflow stationary f i x e d - f i l m reactors digesting piggery waste", Biotechnology Letters, vol 4(2). 21. Lawrence A.W. and P.L.McCarty (1969), "Kinetics of methane fermentation in anaerobic treatment", Journal WPCF, 41, R1-R7. 22. P.L.McCarty (1966), "Kinetics of waste assimilation in anaerobic treatment", Developements in i n d u s t r i a l Microbiology, 7,144. 23. Parkin G.F. and R.E. Speece (1982), "Attached versus 62 suspended growth anaerobic reactors: Response to toxic substances", Presented at the IAWPRC specia l i z e d seminar held in Copenhagen, Denmark, 1982, 261-289. 24. Raman V. and N. Chakladar (1972a), "Upflow f i l t e r s for septic tank efflu e n t s " , Journal WPCF, 44, 1552-1559. 25. Raman V. and N. Chakladar (1972b), "Low cost treatment of effluent from septic tanks by reverse flow (upflow) f i l t e r s " , In Proceedings of the low cost waste treatment symposium, NEERI, Nagpur, India. 26. E.D. Schroeder (1977), "Water and wastewater treatment", McGraw H i l l series in water resources and environmental engineering. 27.Speece R.E. and P.L. McCarty (1964), "Nutrient requirements and b i o l o g i c a l solids accumlation in anaerobic digestion", In Proceedings of the f i r s t international conference of Water p o l l . res., London, U.K., 2, 305. 28. "Standard Methods for examination of water and wastewater", American Public Health Association Inc., 14th edition, 1980. 29. D.W. Taylor (1972), " F u l l - s c a l e anaerobic t r i c k l i n g f i l t e r evaluation", In Proceedings of the 3rd National symposim on food processing wastes, report no. EPA-R2-72-018, U.S. EPA. 30. E.P. Temoin (1980), "Nutrient requirements for aerobic 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 leachate", M.A.Sc. thesis, The University of B r i t i s h Columbia. 63 31. Uloth V.C. and D.S. Mavinic (1977), "Aerobic biotreatment of a high-strength leachate", Journal of the Environmental Engineering d i v i s i o n ASCE, 103, 647-661. 32. L. van den Berg (1977), "Effect of temperature on growth and a c t i v i t y of a methanogenic culture u t i l i z i n g acetate", Canadian journal of microbiology, 23, 898-902. 33. Van den Berg L. and C P . Lentz (1977), "Food processing waste treatment by anaerobic digestion", In Proceedings of the 32nd i n d u s t r i a l waste conference, Purdue University, Lafayette, Indiana, 252-258. 34. Van den Berg L. and C P . Lentz (1980), "Effects of f i l m area-to-volume r a t i o , film support, height and di r e c t i o n of flow on performance of methanogenic fixed f i l m reactors", In "Anaerobic f i l t e r s : An energy plus for waste treatment", Report no. ANL/CNSV-TM-50, Argonne National Laboratory, Argonne, I l l i n o i s , 1-10. 35. Wong P.T. and D.S. Mavinic (1982), "Treatment of a municipal leachate under multi-variable conditions", Presented at the 17th Canadian symposium on water P o l l , research, CCIW, Burlington, Ontario. 36. Yang J. and others (1980), "The response of methane fermentation to cyanide and chloroform", Prog. Wat. Tech., 12, 977-987. 37. Young J.C. and M.F. Dahab (1982a), "Effect of media design on the performance of fixed-bed anaerobic reactors", Presented at the IAWPRC specialized seminar held in Copenhagen, Denmark, 1982. 64 38. Young J.C. and M.F. Dahab (1982b), "Operational c h a r a c t e r i s t i c s of anaerobic packed-bed reactors", Biotechnology and Bioengineering Symposium, 12, 303-316. 39. Young J.C. and P.L. McCarty (1969), "The anaerobic f i l t e r for waste treatment", Journal WPCF, vol 41, no. 5, part 2, R160-R173. 40. Zehnder A.J.B., Ingrarsen K. and T. Marti (1981), "Micrbiology of methane bacteria", Presented at the 2nd international symposium on anaerobic digestion, Travemunde, Germany. 65 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0062625/manifest

Comment

Related Items