UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Effects of temperature on two-stage biostabilization of landfill leachate Zapf-Gilje, Reidar 1979

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

Item Metadata

Download

Media
831-UBC_1979_A7 Z36.pdf [ 3.49MB ]
Metadata
JSON: 831-1.0062564.json
JSON-LD: 831-1.0062564-ld.json
RDF/XML (Pretty): 831-1.0062564-rdf.xml
RDF/JSON: 831-1.0062564-rdf.json
Turtle: 831-1.0062564-turtle.txt
N-Triples: 831-1.0062564-rdf-ntriples.txt
Original Record: 831-1.0062564-source.json
Full Text
831-1.0062564-fulltext.txt
Citation
831-1.0062564.ris

Full Text

EFFECTS OF TEMPERATURE ON TWO-STAGE BIOSTABILIZATION OF LANDFILL LEACHATE B.Eng., McGill U n i v e r s i t y , Montreal, 1977 A THESIS SUBMITTED IN PARTIAL FULFILLMENT 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 thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October 1979 (cT) Reidar Zapf-Gilje., 1979 by Reidar Zapf-Gilje i n In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of Brit ish Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Tj- B-hJc^/Nfcg/^vM^ The University of Brit ish Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date C%&r(fi«r h=M ( i i ) ABSTRACT Leachate i s generated by seepage of water through sanitary land-f i l l s . Where conditions are unfavourable, leachate of high strength and large volumes may be produced, thus creating the p o t e n t i a l f o r serious water contamination problems. This study investigated aerobic, two-stage b i o l o g i c a l treatment of high strength leachate, at d i f f e r e n t operating temperatures. Completely mixed batch reactors of 10 l i t r e volume were employed and operated on a d a i l y fill-and-draw b a s i s . Nutrient loading was s l i g h t l y i n excess of B0Dj-:N:P = 100:5:1. Two-stage b i o l o g i c a l treatment were performed at 23-25°C, 16°C and 9°C. At room temperature the f i r s t stage reactors were operated at a mean c e l l residence time (MCRT) of 6, 9 and 20 days and the p o l i s h i n g reactors at 6, 9, 10 and 20 days. At lower temperatures, the f i r s t stage reactors that were operated at 20 days MCRT and the 10 and 20 days MCRT p o l i s h i n g reactors were eliminated. The leachate employed was lysimeter generated and characterized by COD and BOD,. concentrations of approximately 19,000 mg/L and 14,000 mg/L r e s p e c t i v e l y . In addition, i t contained a spectrum of heavy metals and inorganic s o l i d s . Organic removal by the f i r s t stage systems was exceptionally good. Better than 95% COD and 99% BOD,, were removed under a l l conditions investigated. Removal of heavy metals was 90% or better f o r most of the 9 metals monitored. N i c k e l and magnesium experienced only an average of 50% reduction. For temperatures ranging from 9°C to 25°C the removal performance was not s i g n i f i c a n t l y a f f e c t e d . However, the e f f l u e n t COD and BODj. were s l i g h t l y higher at 9°C, e s p e c i a l l y for the reactor r e c e i v i n g 3 the highest organic load of 3.2 kg COD/m -day. ( i i i ) As a r e s u l t of the low r e s i d u a l concentration of organic material i n the f i r s t stage e f f l u e n t , the p o l i s h i n g reactors experienced washout at a l l temperatures but 9°C. At t h i s temperature and f o r the range of MCRT's tested, the second stage digesters s t a b i l i z e d at low MLSS l e v e l s of 220-600 mg/L, removing about 45% of the r e s i d u a l COD and 80% of the re s i d u a l BOD,.; i n addition, manganese, i r o n and zinc were further reduced by 60-80%. S e t t l i n g problems caused by bulking, d e f l o c c u l a t i o n and probably some hindered s e t t l i n g were encountered throughout the experiment, e s p e c i a l l y at lower MCRT's and temperatures. Hence, i n order to produce enough feed f o r the p o l i s h i n g reactor, a l l e f f l u e n t s were obtained by f i l t e r i n g , rather than s e t t l i n g . The f i l t e r e d e f f l u e n t s a t i s f i e d the l o c a l p o l l u t i o n c o n t r o l objectives f o r most parameters under nearly a l l conditions tested; however, s l i g h t l y higher concentrations are expected under f i e l d conditions due to s o l i d s l o s t i n the e f f l u e n t . (iv) TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS i x CHAPTER 1 INTRODUCTION ." 1 2 BACKGROUND 3 2.1 Sanitary L a n d f i l l Leachates 3 2.2 Aerobic B i o l o g i c a l Treatment of Leachate . . . 6 2.2.1 Organic matter 7 2.2.2 Heavy metal removal 9 ' 2.2.3 Temperature e f f e c t s 12 2.2.4 C h a r a c t e r i s t i c s of fill-and-draw systems 14 3 EXPERIMENTAL MATERIAL AND METHODS 18 3.1 Laboratory System 18 3.2 Experimental Apparatus 18 3.3 Experimental Procedure 20 3.3.1 Acclimatizing 20 3.3.2 Room temperature study 21 3.3.3 Reduced temperature study 24 3.3.4 E f f e c t s of the fill-and-draw procedure 24 3.4 A n a l y t i c a l Procedures 25 3.4.1 Dissolved oxygen and pH 25 3.4.2 S o l i d s , COD arid B0D 5 25 3.4.3 Heavy metals 26 3.4.4 Others 26 3.5 Leachate C h a r a c t e r i s t i c s 26 4 RESULTS AND DISCUSSION 29 4.1 Mixed Liquor C h a r a c t e r i s t i c s 29 (v) TABLE OF CONTENTS (Continued) CHAPTER Page 4.2 Organic Matter Removal 31 4.2.1 BOD 33 4.2.2 COD 33 4.3 Heavy Metal Removal 36 4.4 Temperature E f f e c t s 38 4.5 B i o l o g i c a l P o l i s h i n g Reactors 40 4.6 E f f l u e n t Quality and the PCB Guidelines . . . . 41 4.7 E f f e c t s of the Fill-and-Draw Procedure 44 5 CONCLUSIONS AND RECOMMENDATIONS 50 5.1 Conclusions 50 5.2 Recommendations 52 REFERENCES 53 APPENDICES . . . 55 Appendix A: KINETICS 56 Appendix B: SUPPLEMENTARY RESULTS 62 Appendix C: ALKALINITY REMOVAL . . . . . . . . . . . . . . . 64 (vi) LIST OF TABLES Table No. T i t l e Page 1 Composition of Typ i c a l Leachates 4 2 Proposed Relationship Between COD/TOC, BOD/COD, Absolute COD, and Age of F i l l to Expected E f f i c i e n c i e s of Organic Removal from Leachate . . . . 5 3 Operational Parameters f or Activated Sludge Treatment of Domestic Sewage . . . 7 4 C h a r a c t e r i s t i c s of Mixed-Liquor P r i o r to F i r s t Leachate Addition 20 5 Lysimeter System C h a r a c t e r i s t i c s 27 6 Lysimeter Operational C h a r a c t e r i s t i c s 27 7 Composition of Refuse 27 8 Leachate C h a r a c t e r i s t i c s 28 9 Mixed-Liquor Solids Concentrations 29 10 Applied Organic and F/M Loadings 31 11 Reported Organic Loadings and Removal E f f i c i e n c i e s f o r Aerobic B i o l o g i c a l Treatment of Leachate 32 12 Organic Matter Removal i n Terms of BOD,, and COD . . . 34 13 Mixed-Liquor COD (MLCOD) Concentrations and MLVSS/MLCOD Ratios 36 14 Reported Metal Removal by Aerobic B i o l o g i c a l Digesters Treating Leachate 37 15 Metal Removal E f f i c i e n c i e s 38 16 Performance of B i o l o g i c a l P o l i s h i n g Reactors at 9°C 42 17 C h a r a c t e r i s t i c s of E f f l u e n t Produced by F i r s t Stage Aerobic B i o s t a b i l i z a t i o n of Leachate 43 18 E f f l u e n t C h a r a c t e r i s t i c s of B i o l o g i c a l P o l i s h i n g Treatment 44 19 Data f o r Determination of K i n e t i c Parameters 59 20 K i n e t i c Parameters Based on Soluble BOD^ Concentrations at Room Temperature 59 ( v i i ) LIST OF TABLES (Continued) 21 F i r s t Stage E f f l u e n t Concentrations 62 22 Mixed-Liquor BOD,., mg/L, Versus D i l u t i o n 62 23 Mixed-Liquor COD, TC and TOC i n mg/L 63 24 Average Metal Removals by F i r s t - s t a g e Reactors . . . . 64 ( v i i i ) LIST OF FIGURES Figure No. T i t l e Page 1 Laboratory Reactor Design . . . . 19 2 MLVSS and MLVSS/MLSS during the Acclimatizing Period . . . . 22 3 MLVSS Versus MCRT at Room Temperature . . . . . . 30 4 Removal of COD by Reactor A, B, and C at Room Temperature 35 5 Removal of COD f o r Reactor A, B, and C at Temperatures Ranging from 9-25 C 39 6 Range of S e t t l i n g Performance of Reactor A . . . 46 7 Mixed-Liquor V o l a t i l e Suspended S o l i d s , Dissolved Oxygen and pH Between Leachate Additions of Reactor B at 9°C 47 8 Soluble E f f l u e n t COD and B0D 5 Between Feedings of Reactor B at 9°C 48 9 Determination of k and K Based on Soluble BOD,. Concentrations 60 10 Determination of Y and k. Based on Soluble a r n B0Dr Concentration o l (ix) ACKNOWLEDGEMENTS The author wishes to express h i s gratitude to Dr. D.S. Mavinic for h i s guidance and understanding during t h i s study. He also wishes to thank Dr. R.D. Cameron, Dr. W.K. Oldham, and Mrs. E.C. McDonald f o r t h e i r kind assistance on various aspects of the research. This research was supported with funds provided by the National Research Council of Canada. - 1 -CHAPTER 1 INTRODUCTION Any method used f o r di s p o s a l of our waste products should minimize chemical and b i o l o g i c a l hazards and be environmentally safe. Sanitary l a n d f i l l s are s t i l l considered one of the safest and l e a s t expensive methods of s o l i d waste d i s p o s a l . However, poor s i t e s e l e c t i o n and improper design and operation, coupled with high p r e c i p i t a t i o n , have created serious groundwater p o l l u t i o n by l a n d f i l l leachate. Leachate i s generated by seepage of water through the f i l l . The water dissolves o r i g i n a l components and decomposition products; thus r e s u l t i n g i n a f i n a l product having high organic matter and inorganic ion•concentrations. Several incidences have been reported where leachate has contaminated the surrounding s o i l and p o l l u t e d nearby ground and surface waters. A garbage dump i n Krefeld, Germany, contaminated wells as f a r as 8 kilometers away for more than 18 years 1. In a more recent case, private wells located 300 meters downstream from Llangollon l a n d f i l l i n New Castle County, Delaware, U.S.A., were heavily polluted and subsequently abandoned 2. To reduce the leachate p o l l u t i o n hazard, three approaches are practised today; prevention of leachate production, r e c i r c u l a t i o n of leachate to the l a n d f i l l , and c o l l e c t i o n and treatment of l e a c h a t e 3 . Leachate production may be minimized by i n s t a l l i n g a low permeability cover to prevent the penetration of r a i n f a l l , by d i v e r t i n g upstream surface runoff, and by lo c a t i n g the f i l l above the ground water t a b l e . One disadvantage of t h i s approach i s the reduced rate of s o l i d waste s t a b i l i z a t i o n caused by the absence of water. The second a l t e r n a t i v e involves surface i r r i g a t i o n of leachate on top of l a n d f i l l s . This presumably maintains the moisture content of -2-the s o l i d waste at an optimum l e v e l f o r anaerobic b i o l o g i c a l degradation. The refuse then functions as an anaerobic f i l t e r s t a b i l i z i n g the leachate. The most e f f i c i e n t method involves the c o l l e c t i o n of generated leachate f o r subsequent b i o l o g i c a l and/or physical-chemical treatment. The quantity of leachate produced depends mainly on p r e c i p i t a t i o n and cover mat e r i a l , whereas the q u a l i t y i s a function of refuse composition and l a n d f i l l age. B i o l o g i c a l treatment has been found to be superior in t r e a t i n g high-strength leachate from recently deposited refuse, while physical-chemical methods y i e l d better r e s u l t s t r e a t i n g the lower-strength leachate (produced by more s t a b i l i z e d f i l l s ) 2 . Nearly a l l leachate t r e a t a b i l i t y studies have so f a r been performed at room temperatures. In s i t u , a leachate temperature of 10-15°C i s more l i k e l y to be observed; hence, i t i s of great importance to determine the e f f e c t s these colder conditions have on the b i o l o g i c a l treatment process. The purpose of t h i s i n v e s t i g a t i o n was to evaluate the t r e a t a b i l i t y of high-strength leachates from domestic l a n d f i l l s by aerobic b i o l o g i c a l reactors at temperatures ranging from 10-25°C. Due to the high i n f l u e n t concentration of p o l l u t a n t s , the e f f l u e n t was not expected to s a t i s f y the l o c a l wastewater discharge g u i d e l i n e s 4 ; hence the performance of b i o l o g i c a l p o l i s h i n g reactors was a l s o of i n t e r e s t . To accomplish these objectives, semi-continuous, fill-and-draw, bench-scale reactors were operated at various loadings and temperatures. -3-CHAPTER 2 BACKGROUND 2.1 Sanitary L a n d f i l l Leachates Seepage of water through a l a n d f i l l produces a l i q u i d c a l l e d leachate. The name r e f e r s to the f a c t that water d i s s o l v e s o r i g i n a l components and de-composition products as i t enters the f i l l . When the f i l l has reached i t s moisture absorption capacity, leachate may move i n t o the surrounding s o i l s t r a t a or surface as a spring, depending on the geological c h a r a c t e r i s t i c s of the s i t e . The quantity of leachate produced may range from zero to several m i l l i o n gallons per day, depending on such f a c t o r s as l a n d f i l l composition and geometry, hydrological conditions and the c h a r a c t e r i s t i c s of the f i n a l s o i l cover and i t s vegetation. Although some l a n d f i l l s may not generate any leachate, i t i s important to recognize the p o t e n t i a l f or doing so i f conditions are changed through, for example, future development. The composition of leachates from d i f f e r e n t l a n d f i l l s v a r i e s widely as shown i n Table l 5 . The Chemical Oxygen Demand (COD) concentration may range from "not detectable" to 90,000 mg/L. The strength of the leachate depends, among other f a c t o r s , on the degree of s o l i d waste s t a b i l i z a t i o n within the f i l l . The main s t a b i l i z a t i o n process i s anaerobic b i o l o g i c a l degradation. This process i s dependent on the a v a i l a b i l i t y of water; hence, l a n d f i l l s i n wet climates s t a b i l i z e r e l a t i v e l y f a s t (10-20 years), and concomitantly produce large volumes of leachate. On the other hand, f i l l s i n a r i d regions may remain e s s e n t i a l l y unchanged f o r decades. Chian and DeWalle 2 suggest the use of COD, COD/TOC, BOD5/COD, and age of f i l l to determine the most e f f e c t i v e organic removal treatment method. Table 2 shows the c h a r a c t e r i s t i c s of young, medium and o l d l a n d f i l l s as suggested by Chian and DeWalle 2. -4-TABLE 1 COMPOSITION OF TYPICAL LEACHATES Parameter Range of Values ( L a n d f i l l s and or Concentrations* Test Lysimeters) BOD5 9 - 55 000 COD 0 - 90 000 Total Carbon 715 — 22 350 Total Organic Carbon 715 - 22 350 Total Solids 1 000 _ 45 000 Total V o l a t i l e S o l i d s 1 000 - 23 157 Total Dissolved Solids 0 - 42 300 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 Beryllium 0 - 0.3 Calcium 5 - 4 000 Cadmium 0 - 0.19 Chloride 34 - 2 800 Chromium 0 - 33.4 Copper 0 - 10 Iron 0.2 - 5 500 Lead 0 - 5.0 Magnesium 165 - 15 600 Manganese 0.06 - 1 400 Mercury 0 - 0.064 Molybdenum 0 - 0.52 Nitrogen - t o t a l 0 - 2 406 - NH3 0 - 1 106 Nickel 0.01 - 0.80 Phosphorus - t o t a l 0 - 154 Potassium 2.8 - 3 770 Sodium 0 - 7 700 Sulphates 1 - 1 826 Sulphides 0 - 0.13 Titanium 0 - 5.0 Vanadium 0 - 1.4 Zinc 0 - 1 000 PH 3.7 - 8.5 Tannin-like compounds 78 - 1 278 Colour (chloroplatinate) 0 - 12 000 Odour not detectable to t e r r i b l e * A l l values except those f o r pH, colour and odour are i n mg/L. TABLE 2 PROPOSED RELATIONSHIP BETWEEN COD/TOC,.BOD^/COD, ABSOLUTE COD, AND AGE OF FILL TO EXPECTED EFFICIENCIES OF ORGANIC REMOVAL FROM LEACHATE2 Chemical COD/TOC BODv/COD Age of F i l l COD, i n milligrams per l i t r e B i o l o g i c a l Treatment p r e c i p i -t a t i o n Cmass lime dose) Chemical Oxidation Ca (C10) 2 °3 Reverse Osmosis Activated Carbon Ion ex-change r e s i n s >2.8 >0.5 Young (<5 yr) >10,000 Good Poor Poor Poor F a i r Poor Poor 2.0-2.8 0.1-0.5 Medium (5 yr-10 yr) 500-10,000 F a i r F a i r F a i r F a i r Good F a i r F a i r <2.0 <0.1 Old (>10 yr) <500 Poor Poor F a i r F a i r Good Good F a i r -6-The leachate used i n t h i s study was generated from a 7-year o l d " f i l l " and had an average COD concentration of 19,250 mg/L, a COD/TOC of 3.15 and a BOD^/COD of 0.71; hence, b i o l o g i c a l treatment was expected to be most e f f i c i e n t i n terms of organic removal. 2.2 Aerobic B i o l o g i c a l Treatment of Leachate B i o l o g i c a l treatment involves the conversion of poll u t a n t s by a heterogeneous mixture of b a c t e r i a l cultures and t h e i r predators. Most of the organic matter i s oxidized to provide energy, although some i s synthesized i n t o new c e l l u l a r materials. Aerobic b i o l o g i c a l processes are used f o r removal of soluble, c o l l o i d a l and fine suspended organics not removed by primary sedimentation. "Suspended-culture" processes, such as activated sludge (A/S), aerated lagoons and oxidation ponds, are most commonly used. The b a c t e r i a form fl o e s which aire kept in. suspension by aeration, mechanical mixing or a combination of both. The suspended f l o e s adsorb inflowing-organic material, most of -which i s " converted to energy and new c e l l material. The r e s t i s removed with the b i o - f l o c s i n the f i n a l c l a r i f i e r . The A/S process i s commonly operated by c o n t r o l l i n g the food-to-microorganism r a t i o (F/M) or the mean c e l l residence time (MCRT). Both parameters are c o n t r o l l e d by p a r t i a l recycle of f i n a l c l a r i f i e r sludge. Table 3 shows the range of some operating parameters used f o r A/S t r e a t -ment of domestic sewage. In t h i s i n v e s t i g a t i o n , a modified A/S process was used. This semi-continuous fill-and-draw process had no c e l l u l a r recycle and hence the MCRT was i d e n t i c a l to the hydraulic detention time. TABLE 3 OPERATIONAL PARAMETERS FOR ACTIVATED SLUDGE TREATMENT OF DOMESTIC SEWAGE6 Process Modification MCRT, days F/M, kg BOD 5Ag MLVSS-day Organic loading rate kg BOD5/m3-day MLSS, mg/L Conventional 5-15 0.2-0.4 0.32 - 0.64 1500-3000 Complete-mix 5-15 0.2 - 0.6 0.80 - 1.92 3000-6000 Extended Aeration 20-30 0.05 - 0.15 0.16 - 0.40 3000-6000 High-rate Aeration 5-10 0.4 - 1.5 1.60 - 16.0 4000-10000 2.2.1 Organic matter Boyle and Ham7 studied the b i o l o g i c a l t r e a t a b i l i t y of several leachates, with COD concentrations ranging from 2700 to 12300 mg/L. They used aerobic and anaerobic fill-and-draw reactors with mixed-liquor volumes ranging from 500 to 2000 mL. No nutrients were added. At room temperature, the aerobic process using an MCRT of 5 days resu l t e d i n 80 and 93% reduction of COD, at organic loadings of 0.545 and 1.04 kg COD/m3-day re s p e c t i v e l y . An increase i n organic loading from 1.04 to 1.75 caused considerable reduction i n process e f f i c i e n c y . An organic loading of 6.1 kg C0D/m3-day and a F/M r a t i o i n excess of 1.5 was unsuccessful. An aerobic p o l i s h i n g u n i t t r e a t i n g e f f l u e n t from the anaerobic reactors (COD = 740 mg/L, B0D 5 = 130 mg/L) was capable of further reducing COD and BOD by 40 and 70% r e s p e c t i v e l y . -8-Cook and Foree 8 investigated aerobic b i o s t a b i l i z a t i o n of medium-strength leachate at room temperatures (BOD5 = 7,100 mg/L, COD = 15,800 mg/L, pH = 5.45). Based on a preliminary study, i t was decided to run four 2-L reactors a t 10 days detention time, to determine the e f f e c t s of time and nu t r i e n t addition on the removal e f f i c i e n c i e s . An a d d i t i o n a l fill-and-draw unit operating at an MCRT of 5 days, and a continuous-flow reactor operating at 2 days detention time,.both experienced wash-out. The addition of lime and nutrients d i d not s i g n i f i c a n t l y improve the removal e f f i c i e n c i e s . At an organic loading of 1.58 kg C0D/m3-day, the u n i t being fed leachate only s t a b i l i z e d at MLVSS = 4,400 mg/L, giving a F/M of 0.16 kg BOD^/kg MLVSS-day. The s e t t l i n g c h a r a c t e r i s t i c s were good, with a sludge volume index (SVI) of 55 and only 55 mg/L t o t a l sus-pended s o l i d s (TSS) i n the e f f l u e n t . The BOD^ and COD concentrations i n the e f f l u e n t were 26 and 360 mg/L (99.7 and 97.6% removal) r e s p e c t i v e l y , which indicates almost complete b i o l o g i c a l s t a b i l i z a t i o n of the leachate. Uloth and M a v i n i c 9 ' 1 0 used high-strength leachate i n t h e i r b i o l o g i c a l t r e a t a b i l i t y study. The digesters were operated on a d a i l y fill-and-draw basis and the 4.5 L mixed-liquor kept aerobic. Nutrients were added approximately to the recommended r a t i o of 100:5:1 (B0D,-:N:P). For i n f l u e n t concentrations between 44,000 and 52,000 mg/L, the COD removal increased from 96.8 to 99.2%, as the mean c e l l residence time (MCRT) increased from 10 to 60 days. The B0D 5 removal was better than 99.7% f o r an i n f l u e n t ranging from 32,000-38,000 mg/L. Approximately 2 hours were needed f o r complete s e t t l i n g of the b i o l o g i c a l f l o e s , due to the high MLVSS concentrations of 8,000-16,000 mg/L. An MCRT of 20 days and a F/M of l e s s than 0.15 kg BOD^/kg MLVSS-day was recommended f o r aerobic s t a b i l i z a t i o n of s i m i l a r strength leachate at room temperature. -9-Studies of the b i o l o g i c a l aerated lagoon or extended aeration process were conducted by Chian and DeWalle 3, using s i x completely mixed f i l l - a n d -draw reactors with no c e l l u l a r r e c y c l e . Undiluted leachate of 57,900 mg/L COD was fed to three digesters operating at MCRT's of 85.7, 60 and 30 days i n the f i r s t part of the experiment. These mean c e l l residence times corresponded to organic loadings of 0.67, 0.96 and 1.94 kg COD/m3-day re s p e c t i v e l y . During the l a t t e r h a l f of the i n v e s t i g a t i o n , undiluted leachate, which had a COD concentration of 35,200 mg/L, was used. The three reactors then received 1.15, 2.35 and 5.02 kg COD/m3-day, corresponding to MCRT's of 30, 15 and 7 days r e s p e c t i v e l y . A wide range of n u t r i e n t additions were tested with the conclusion that, at low MCRT's ( i . e . high organic loadings), the addition should be at a r a t i o of 100 :5.2:0.6. (COD:N:p) f o r optimum organic removal and^settling performance. The highest loaded reactor (MCRT = 7 days), with MLVSS = 13,500 mg/L and F/M = 0.373 kg COD/kg MLVSS-day, reduced COD by 97.1%. The removal e f f i c i e n c y increased to 99.3% f o r a MCRT of 85.7 days. 2.2.2 Heavy metal removal The activated sludge process has been shown to e f f e c t i v e l y remove heavy metal ions present i n the i n f l u e n t 2 ' 3 ' 9 ' 1 0 ' 1 1 ' 1 2 . The main mechanisms of removal are p r e c i p i t a t i o n of metal hydroxides, with subsequent entrapment i n the b i o l o g i c a l f l o e , sorption by organic s o l i d s and consump-t i o n by the biomass. These mechanisms depend on such factors as: r e l a t i v e a f f i n i t y and t o t a l capacity f o r cation sorption by organic s o l i d s , concen-t r a t i o n of cations and the r e l a t i v e s o l u b i l i t y products of metal hydroxides. The pH has a s i g n i f i c a n t e f f e c t on metal-ion removal. Hydrogen ion competes with other cations, i n c l u d i n g metals, f o r binding s i t e s on the sludge f u n c t i o n a l groups; therefore, as the pH i s r a i s e d , more binding -10-s i t e s are a v a i l a b l e f o r the formation of metal-organic complexes. Also, as the pH i s increased, the hydroxyl ion s u c c e s s f u l l y competes with other ligands, thus r e s u l t i n g i n p r e c i p i t a t i o n of metal hydroxides. Cheng et_ a l 1 1 investigated the uptake of heavy metals by activ a t e d sludge, using semi-continuous batch reactors being fed d i l u t e d dog food. Using slug doses of up to 25 mg/L of cadmium, copper, lead and n i c k e l , i t was found that metal uptake was v i r t u a l l y complete a f t e r 3-10 minutes contact time. I t was also concluded that, at low concentrations, the metal uptake was mainly due to metal-organic complex formation, whereas metal-ion p r e c i p i t a t i o n played a more s i g n i f i c a n t r o l e at higher concen-t r a t i o n s . Metal uptake by the biomass was found to increase s i g n i f i c a n t l y with increasing pH, organic matter and metal concentrations. At MLVSS l e v e l s of 1600-1800 mg/L, removal e f f i c i e n c i e s of 90, 89, 80 and 58% were obtained for lead, copper, cadmium and n i c k e l r e s p e c t i v e l y . Neufeld and Hermann 1 2 studied the uptake of mercury, cadmium and zinc by acclimated activated sludge using shock doses of 30, 100, 300 and 1000 mg/L. The substrate was composed of neopephone, sugar and yeast extr a c t , and appropriate additions of mono- and d i - b a s i c phosphate (providing s u f f i c i e n t phosphate nutrients and pH bu f f e r c a p a c i t y ) . A l l metals were r a p i d l y removed from the aqueous s o l u t i o n by the b i o l o g i c a l f l o e . At doses up to 300 mg/L, 95% mercury, 73% cadmium and 53% zinc were removed a f t e r only 3 hours of contact. No s i g n i f i c a n t metal uptake occurred i n the next two weeks. The p o t e n t i a l f o r recovery of heavy metals from very d i l u t e solutions was shown by the b i o l o g i c a l f l o e ' s c a p a b i l i t y to concentrate the aqueous metals. At equilibrium, the weight r a t i o of metal i n biomass to metal i n s o l u t i o n ranged from 4000 to 10,000 f o r mercury, cadmium and z i n c . -11-B i o l o g i c a l i n h i b i t i o n caused by mercury could be t o t a l l y counter-acted by increasing the concentration of organic substrate. This i n d i c a t e s that mercury competes with the substrate f o r some v i t a l l i n k i n the enzyme-substrate chain, thus causing the t o x i c e f f e c t to decrease with increasing substrate concentration. Similar i n h i b i t i o n was also caused by cadmium and z i n c . However, as t h e i r concentrations increased beyond a threshold of 25 mg/L Zn and 63 mg/L Cd, the metabolic rate decreased, unaffected by the substrate l e v e l . Based on t h e i r r e s u l t s , Neufeld and Hermann concluded that even wastewater with high organic and heavy-metal concentration can be e f f e c t i v e l y treated, simply by varying the sludge age of the acclimatized activated sludge. Cook and Foree 8 a t t r i b u t e d the e f f i c i e n t removal of ir o n (>96%) and calcium (97%) mainly to p r e c i p i t a t i o n , caused by the high mixed-liquor pH of 8.4. However, t h i s pH i s too low to cause s i g n i f i c a n t p r e c i p i t a t i o n of magnesium. Only 18% magnesium was removed from the digester fed only leachate. Uloth and M a v i n i c 9 ' 1 0 experienced better than 95% removal of aluminum, cadmium, calcium, chromium, i r o n , manganese and zinc i n most of t h e i r reactors. An average of 85% lead, 60% magnesium and 77% n i c k e l were also removed by the b i o l o g i c a l f l o e , whereas potassium remained almost completely i n s o l u t i o n (12% removed). The e f f e c t i v e metal uptake was a t t r i b u t e d to high pH values (pH > 8.5) and high mixed-liquor v o l a t i l e suspended s o l i d s (MLVSS) concentrations of 8,000-16,000 mg/L. The removal of a l l metals was comparable f or the s i x reactors, i n d i c a t i n g that the metal uptake i s independent of applied loading rates ( i . e . MCRT). -12-The study performed by Chian and DeWalle 3 supports the above suggestion. When s u f f i c i e n t nutrients were added, better than 99% removal of i r o n , calcium and zinc were experienced f o r a l l applied loadings. The average removal of magnesium, sodium, and potassium were 76%, 24% and 17% r e s p e c t i v e l y . The mixed-liquor pH ranged from 8.5 to 8.8 and the MLVSS concentrations were 8,000-13,500 mg/L. 2.2.3 Temperature e f f e c t s Temperature v a r i a t i o n s a f f e c t a l l b i o l o g i c a l processes. Lower temperatures normally decrease the oxygen u t i l i z a t i o n irate caused by the metabolic a c t i v i t y . However, the activated sludge process i s r e l a t i v e l y i n s e n s i t i v e to temperature changes normally encountered. E c k e n f e l d e r 1 3 explains the temperature i n s e n s i t i v i t y of the A/S process as follows: Oxygen d i f f u s e s from the surrounding l i q u i d i n t o the b i o l o g i c a l f l o e . The environmental conditions within the f l o e depend on the oxygen d i f f u s i o n r a t e . At high temperatures and r e s u l t a n t high u t i l i z a t i o n rates, oxygen i s r a p i d l y exhausted by b a c t e r i a l r e s p i r a t i o n ; hence, the oxygen penetration i s short, leaving a large portion of the f l o e anaerobic. At lower temperatures, the reduced oxygen u t i l i z a t i o n rate leaves a greater portion of the f l o e aerobic. As he puts i t , "- one high-speed worker i s the equivalent of ten low-speed workers -." As the organic loading i s increased, however, the oxygen penetration at low temperatures i s i n s u f f i c i e n t to compensate f o r the reduced u t i l i z a -t i o n r a t e . The Streeter-Phelps' empirical modification of the Arrhenius law has been widely used to describe the temperature e f f e c t s on rate constants used i n b i o l o g i c a l treatment of wastewaters. However, recent i n v e s t i g a -t i o n s 1 ^ ' 1 5 conclude that the modified Arrhenius equation (Appendix A) does not accurately describe such temperature e f f e c t s . The a p p l i c a b i l i t y -13- . of the equation i s l i m i t e d because the temperature a c t i v i t y c o e f f i c i e n t , 9, depends on the substrate c h a r a c t e r i s t i c s as well as the gross b a c t e r i a l culture adaptation. The gross b a c t e r i a l culture adaptation, i n turn, depends on population s h i f t s and the acclimation of s p e c i f i c b a c t e r i a within the mixed c u l t u r e 1 4 > 1 6. Benedict and C a r l s o n 1 6 investigated temperature adaptation of mixed cultures fed primary s e t t l e d , domestic wastewater of 4°C. The continuous flow systems were f i r s t operated at 19°C then at 4°C and 32°C. Aft e r the i n i t i a l shock of the 15°C temperature change, i t took the 4°C culture two.weeks to s t a b i l i z e , as measured by the endogenous r e s p i r a t i o n rate. The 32°C d i d not reach steady-state operation i n i t s 26 days of operation. The f a i l u r e of t h i s reactor was a t t r i b u t e d to washout of biomass caused by s e t t l i n g problems. The SVI was only 45 but the coloured supernatant contained f i n e d i s c r e t e suspended materials. The 4°C and 19°C systems had SVI's of 110 and 98 r e s p e c t i v e l y . Both cultures produced a c l e a r but coloured e f f l u e n t with l e s s than 45 mg/L suspended s o l i d s . For applied organic loadings of 0.25-0.4 kg BOD^/kg MLSS-day, the mean e f f l u e n t q u a l i t y of the 4°C system was found to be only s l i g h t l y worse than that of the 19°C (89 compared to 82 mg/L COD).. Benedict and Carlson .therefore concluded that, although the endogenous r e s p i r a t i o n rate i n d i c a t e d a reduced culture a c t i v i t y , the o v e r a l l system performance was apparently not af f e c t e d by the temperature drop. Sayign and M a l i n a 1 4 evaluated the e f f e c t s of temperature on the k i n e t i c s and performance e f f i c i e n c i e s of the complete-mix activated sludge process t r e a t i n g domestic wastewater. The 10-L continuous-flow reactors were completely mixed by d i f f u s e d a i r aeration and operated i n a temperature c o n t r o l l e d room. Quasi-steady-state conditions were achieved a f t e r 2 weeks of acclimation at each respective operating temperature. The -14-operational parameters were a l l evaluated at 4°, 10°, 20°, and 31°C. In summary, the authors found that the organic removal e f f i c i e n c y i s v i r t u a l l y independent of temperature which the range studied. The microorganism growth r a t e , the substrate u t i l i z a t i o n rate as well as the sludge s e t t l e a b i l i t y (SVI) were not a f f e c t e d by temperature i n the range from 4° to 20°C. At 31°C, however, the s p e c i f i c growth rate decreased s i g n i f i c a n t l y , the substrate u t i l i z a t i o n rate increased, and d e t e r i o r a t i o n of s e t t l i n g performance was observed. The dissolved oxygen u t i l i z a t i o n rates were i d e n t i c a l at 10° and 20°C, whereas a lower rate was experienced at 4°C and a higher at 31°C. Based on t h e i r f i n d i n g s , the authors concluded that the modified Arrhenius equation does not accurately apply when evaluating temperature e f f e c t s on t r e a t i n g domestic wastewater by the completely mixed continuous-flow activated sludge process. 2.2.4 C h a r a c t e r i s t i c s of fill-and-draw systems I t i s generally accepted that the k i n e t i c s of completely mixed fill-and-draw systems c l o s e l y r e l a t e s to those of continuous-flow processes such as aerated lagoon and conventional activated sludge treatment (plug-flow) . As f o r plug-flow systems, the fill-and-draw reactor experiences a "shock" immediately a f t e r feeding. The mixed-liquor DO drops as the growth rate and substrate u t i l i z a t i o n rate increase. For a normal loading range, the biomass returns to steady-state operation within 24 hours. Selna and S c h r o e d e r 1 7 ' 1 8 studied the e f f e c t s of t r a n s i e n t organic loading using continuous flow, stirred-tank reactors. The t r a n s i e n t loadings were imposed on the experimental system by suddenly increasing the feed concentration to 2.0-7.5 times the steady-state i n f l u e n t COD. After 5 hours the feed concentration was suddenly dropped to the background l e v e l of 265 mg/L. (This loading pattern i s c a l l e d the square-wave model). -15-The authors found that the response of the microorganisms to the tra n s i e n t loading was nearly immediate, as indicated by sudden changes i n MLSS, u n i t growth r a t e , substrate u t i l i z a t i o n r a te, and dissolved oxygen concentration. For a square-wave amplitude of 6.85 and a MCRT of 5.4 days the MLSS, u n i t growth r a t e , and substrate u t i l i z a t i o n rate a l l increased s i g n i f i c a n t l y during the tr a n s i e n t loading period. The mixed l i q u o r DO dropped from near saturation to approximately 3 mg/L shor t l y a f t e r the square-wave loading was i n i t i a t e d . A l l parameters returned to steady-state values within 24 hours a f t e r the transient loading was imposed. The authors also noted that, i n the reactors containing bulking sludge, a s i g n i f i c a n t d e f l o c c u l a t i o n was evident a f t e r i n i t i a t i o n pf tra n s i e n t loading. They postulate that the d e f l o c c u l a t i o n was probably due to increased growth rates and l e s s production of extra c e l l u l a r slime during the transient loadings. The performance of the activated sludge process i s dependent on the a b i l i t y of the secondary c l a r i f i e r to separate and concentrate the sludge from the treated e f f l u e n t . Excessive l o s s of s o l i d s i n t o the e f f l u e n t may be caused by poor design and operation of the secondary c l a r i f i e r or by poor f l o c c u l a t i o n and s e t t l i n g c h a r a c t e r i s t i c s of the biomass. Bulking i s generally defined as any activated sludge which s e t t l e s slowly, compacts poorly and has a sludge volume index (SVI) greater than 1 9 , 2 0 . 150. This condition i s normally a t t r i b u t e d to excess growth of filamentous organisms. Non-filamentous or zoogleal bulking occurs when activated sludge organisms secrete an extra c e l l u l a r material with a high degree of hydration. As a r e s u l t , b i o f l o c s with excessive amounts of bound water are produced. The large amounts of entrapped water reduces the density and hence the s e t t l e a b i l i t y of the f l o e s . Both filamentous and zoogleal -16-bulking have been associated with shock loadings of organic, a c i d i c or to x i c nature. I n e f f e c t i v e aeration, causing anaerobic conditions i n the aeration tank, and i n s u f f i c i e n t n u t r i e n t s may also produce a bulking s l u d g e 1 9 ' 2 0 . Turbid e f f l u e n t s are mainly caused by the formation of pinpoint f l o e s or by a d e f l o c c u l a t i o n process. Deflocculation involves breaking up of activa t e d sludge f l o e s into i n d i v i d u a l microbial c e l l s and p a r t i c l e s . The sludge which s e t t l e s u sually compacts well and i s e a s i l y separated by sedimentation. The same conditions producing a bulking sludge may also cause d e f l o c c u l a t i o n ; hence, sometimes a mixed-liquor may be produced that s e t t l e s slowly, compacts poorly and gives a t u r b i d e f f l u e n t ^ u . Pinpoint f l o e e f f l u e n t contains many small but v i s i b l e sludge fl o e s (pinpoint floes) which remain suspended i n the supernatant. This type of sludge i s characterized by a r e l a t i v e l y high "zone-settling" v e l o c i t y and poor c l a r i f i c a t i o n above the sludge i n t e r f a c e during s e t t l i n g . The absence of filamentous organisms has been associated with pinpoint f l o e s i n e f f l u e n t s . Sezgin et a l 2 1 suggest that f l o c c u l a t i o n of b a c t e r i a l -sized primary p a r t i c l e s form microstructures. A well developed activated sludge f l o e (macrostructure) consists of a coherent mass of microstructures. Filaments then form a r i g i d backbone to which these zoogleal microstructures can attach themselves. I f i n s u f f i c i e n t filamentous organisms are present, the f l o e w i l l be weak and subject to breaking up i n t o smaller aggregates in the turbulent environment of the aeration basin. Hoepker and Schroeder 2 2 studied the e f f e c t s of loading rate on e f f l u e n t q u a l i t y , using batch (0 f i l l time) and semi-batch (8-hour f i l l time) fill-and-draw activated sludge systems. The e f f l u e n t TOC concentra-tions of both systems were comparable and increased with increasing organic f eed-jconcentrations. -17-The batch systems, however, were very unstable with respect to s e t t l e a b i l i t y , thereby r e s u l t i n g i n wide v a r i a t i o n s i n both MLSS and e f f l u e n t SS concentrations. The l o s s of s o l i d s i n the e f f l u e n t was mainly a t t r i b u t e d to dispersed growth or d e f l o c c u l a t i o n . Hence, the authors concluded that the sludge's s e t t l e a b i l i t y i s c r i t i c a l , both i n terms of design and operation and must therefore be s a t i s f a c t o r i l y described before batch processes can be used. The study described herein made use of completely mixed f i l l - a n d draw systems and s e t t l i n g problems were encountered. However, based on the above discussion, i t i s f e l t that the performance of the reactors can be re l a t e d to l a r g e r - s c a l e , continuous flow systems. -18-CHAPTER 3 EXPERIMENTAL MATERIAL AND METHODS 3.1 Laboratory System The u t i l i z a t i o n of bench-scale, semi-continuous reactors for the evaluation of b i o l o g i c a l t r e a t a b i l i t y c h a r a c t e r i s t i c s of a wastewater o f f e r s many advantages over a continuous-flow system. A continuous flow experiment, although more c l o s e l y r e l a t e d to a f u l l scale A/S process, i s f ar more time consuming, unstable and requires extensive maintenance and large volumes of feed. The fill-and-draw system i s simple, r e l i a b l e and enables the in v e s t i g a t o r to quickly determine the t r e a t a b i l i t y of wastewaters under d i f f e r e n t environmental conditions. For t h i s i n v e s t i g a t i o n , two a d d i t i o n a l factors governed the choice of experimental systems, namely the importance of ty i n g i n to previous work performed at the University of B r i t i s h Columbia and the volume l i m i t a t i o n . o f lysimeter-generated leachate. 3 .2 Experimental Apparatus A l l reactors used were made from 10 L glass j a r s . The bottoms were removed and rubber stoppers were, a f t e r 24 hours soaking i n d i l u t e acids fo r removal of metals, placed i n the necks. Coarse bubble, glass d i f f u s e r stones were f i t t e d through a hole i n the stoppers. O i l free a i r was supplied by the laboratory compressed a i r system. A f a i r l y constant a i r flow of one l i t r e a i r per l i t r e of mixed l i q u o r per minute was maintained by means of a pressure reducing valve on the a i r supply l i n e and adjustable hose clamps on a l l i n d i v i d u a l tubing. Constant speed s t i r r e r s kept feed and biomass completely mixed throughout the experiment. The laboratory reactor used i s schematically shown i n Figure 1. -19-Vo lumet r i c G r a d u a t i o n Porous Glass A i r D i f f u s e r P l a s t i c T u b i n g O i l - Free A i r E l e c t r i c Mo to r D r i v e n S t i r r e r Rubber S topper Ad jus tab le Screw Clamp To Other D i g e s t e r s FIG. 15 LABORATORY REACTOR D E S I G N . 3.3 Experimental Procedure 3.3.1 Acclimatizing For successful 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 i t i s necessary to gradually acclimatize the microbial population to the high concentrations of organic matter and metal ions. Mixed l i q u o r from domestic a c t i v a t e d sludge plants have a large and highly d i v e r s i f i e d biomass capable of f a i r l y r a p id adaptation to leachate. About 20 L of activa t e d sludge was obtained from the Mamquam sewage treatment plant (STP) located i n Squamish, B.C., about 50 km north of Vancouver. This package plant tre a t s domestic sewage, mixed with some l i g h t i n d u s t r i a l wastewater. Five l i t r e s of the mixed-liquor were added to each of the three reactors (called A). The biomass was then thoroughly mixed and aerated p r i o r to f i r s t leachate addition. The c h a r a c t e r i s t i c s of the mixed-liquor immediately p r i o r to the f i r s t leachate feeding are shown i n Table 4. TABLE 4 CHARACTERISTICS OF MIXED LIQUOR PRIOR TO FIRST LEACHATE ADDITION Parameter .Value MLSS 4690 mg/L MLVSS 3820 mg/L MLVSS/MLSS 0. 81 pH 7 .0 For a mean c e l l residence time of 20 days, e a r l i e r s t u d i e s y , l u indicated that the MLVSS would s t a b i l i z e f a r above 3800 mg/L. Thus, i n order to increase the MLVSS more r a p i d l y , i t was decided to withdraw only supernatant from the reactors.. -21-During t h i s period, water l o s t by evaporation was d a i l y replaced by d i s t i l l e d water. The reactor sides and s t i r r e r were scraped and the adhering biomass returned to the mixed l i q u o r . Then the a i r flow and s t i r r e r were turned o f f and the mixed l i q u o r allowed to s e t t l e f o r no more than 30 minutes. Approximately 250 mL c l e a r supernatant was subse-quently removed from each reactor and replaced by an equal amount of leachate. Nutrients were added i n s l i g h t excess of 100:5:1 (B0Dg:N:P). Af t e r 3 weeks of operation, the MLVSS had increased to 5,800 mg/L and the MLVSS/MLSS r a t i o had decreased to 0.64 (see Figure 2). The pH had e a r l i e r s t a b i l i z e d at about 8.3. At t h i s point, i t was decided to increase the mixed l i q u o r volume to 7.5 L i n order to produce more super-natant for subsequent t e s t i n g , and feeding of the p o l i s h i n g reactors. The increased volume was obtained by merely eliminating the d a i l y supernatant withdrawal for 10 days. Upon reaching the designated mixed-liquor volume, d a i l y withdrawal of 375 mL mixed-liquor was i n i t i a t e d , corresponding to a MCRT of 20 days. Figure 2 shows, a f t e r i n i t i a t i o n of mixed-liquor with-drawal, the MLVSS concentration dropped to about the same l e v e l as p r i o r to any leachate additions. The a c c l i m a t i z i n g process, as described, took 46 days. I t i s believed that by operating the reactors at the desired MCRT throughout the a c c l i m a t i z i n g period, steady-state operation may be reached i n only 3-4 weeks. 3.3.2 Room temperature study  Run I, 23°C: Three reactors of 7.5 L mixed l i q u o r each were operated at a mean c e l l residence time of 20 days (reactors A). The d a i l y operational procedures were: 1. Replaced evaporated water with d i s t i l l e d water (DW). -22-6 5 0 0 _Wi thd rawa l of S u p e r n a t a n t No W i t h d r a w a l of I W i t h d r a w a l M i x e d L i q u o r ^ , 5 5 0 0 1 E to to > _ i 2 4 5 0 0 1 -Q o 0.5 1 10 20 30 Ti me , days 4 0 FIG.2 5 MLVSS AND MLVSS/MLSS DURING THE ACCLIMATIZING PERIOD. -23-2. Scraped reactor wall and s t i r r e r to prevent los s of biomass. 3. Withdrew 375 mL of mixed l i q u o r from each reactor (MCRT=20 days). 4. Fed each reactor 375 mL of leachate brought to room temperature. 5. Added d i l u t e d NH^I^PO^ and NH^NO^ to ensure a nutrie n t loading of 100:5:1 (BODc:N:P). o The removed mixed-liquor was s e t t l e d i n a one l i t r e graduated c y l i n d e r and i t s s e t t l i n g c h a r a c t e r i s t i c s recorded (see Figure 6). Of the c l e a r supernatant obtained, 450 mL was fed to the p o l i s h i n g reactors and the r e s t was used f o r a n a l y s i s , e i t h e r fresh or a f t e r storage at 4°C. When steady-state operation of a l l three A reactors had been reached, two p o l i s h i n g reactors were st a r t e d up, using a c t i v a t e d sludge from the Mamquam STP; t h i s was d i l u t e d with DW to a MLVSS concentration of 1430 mg/L. Due to feed l i m i t a t i o n s , a mixed-liquor volume of 3 L was used. The mixed-liquor was mixed and aerated f o r 24 hours p r i o r to f i r s t feeding. The two reactors were operated at 10 and 20 days MCRT and the d a i l y operational procedures were as described for reactors A. Run I I , 25°C: The organic removal performances of the three "A" reactors were extremely good, leaving only 23 mg/L BOD,, i n the s e t t l e d e f f l u e n t ( f i l t e r e d BOD,. = 6 mg/L). As a r e s u l t , both polishing'reactors experienced washout and subsequently "died". In order to produce e f f l u e n t of higher organic content, f i r s t stage reactors operated at a MCRT of 6 days (reactor B) and 9 days (reactor C) res p e c t i v e l y , were started. The e f f l u e n t s from both reactors each fed two po l i s h i n g reactors operated at 6 and 12 days MCRT. Reactor B was f i l l e d with 6 L of mixed-liquor from reactors A and 9 L was added to reactor C. These mixed-liquor volumes were d i c t a t e d by the l i m i t e d a v a i l a b i l i t y of leachate, as well as the necessity to produce enough supernatant (SN) for a n a l y s i s , -24-and f o r feeding of the 3 L mixed-liquor p o l i s h i n g reactors. The operational and t e s t procedures were i d e n t i c a l to those of Run I , with the exception of e f f l u e n t c o l l e c t i o n . During Run I , a l l of the supernatant was c o l l e c t e d by s e t t l i n g of withdrawn mixed-liquor. The s e t t l i n g c h a r a c t e r i s t i c s of the 20-day MCRT reactors v a r i e d s i g n i f i c a n t -l y f o r no apparent reason. On a poor day, a s e t t l i n g time of several hours was needed to generate enough e f f l u e n t , hence producing anaerobic sludge. Due to t h i s s e t t l i n g i n s t a b i l i t y and because the s e t t l i n g c h a r a c t e r i s t i c s deteriorated s i g n i f i c a n t l y f o r lower MCRT's, i t was decided to obtain c l e a r supernatant f o r a l l subsequent runs by f i l t e r i n g of the mixed-liquor, using Whatman No. 4 f i l t e r paper. 3.3.3 Reduced temperature study Run I I I , 16°C: A l l reactors used i n Run I I were set up i n a "cold room" of 16°C. The biomass adjusted well to the sudden 8°C temperature change and steady-state conditions, as determined by mixed-liquor COD and s o l i d s concentra-t i o n s , were established a f t e r 12 days. A l l procedures were as e a r l i e r described. Run I V , 9°C; Af t e r s u f f i c i e n t a n alysis had been performed at 16°C, the temperature was gradually dropped to 9°C over two days. Steady-state operation was evident a f t e r only 10 days of a c c l i m a t i z i n g . The s e t t l i n g c h a r a c t e r i s t i c s had deteriorated further at these lower temperatures; hence, a l l mixed-l i q u o r was f i l t e r e d to produce s u f f i c i e n t e f f l u e n t of consistent q u a l i t y . 3.3.4 E f f e c t s of the fill-and-draw procedure Poor s e t t l i n g performances were experienced at a l l temperatures f o r mean c e l l residence times of 6 and 9 days. The sludge s e t t l i n g was extremely slow and produced a highly t u r b i d supernatant. -25-I t i s suspected that the d a i l y leachate addition shocked the biomass, thereby r e s u l t i n g i n the adverse s e t t l i n g performance. To support t h i s suspicion, mixed-liquor DO and pH were monitored. In addition, MLVSS, as well as e f f l u e n t BOD,, and COD, were determined f o r several 24 hour b periods, and photomicrographs were made during the same period. An a d d i t i o n a l study of Reactor B was performed to determine the e f f e c t s of fill-and-draw procedures performed every 12 hours compared to every 24 hours. The mean c e l l residence time was kept at 6 days and the l i q u i d temperature at 9°C. The above mentioned parameters were monitored between feedings f o r several 12 hour periods. 3.4 A n a l y t i c a l Procedures 3.4.1 Dissolved oxygen and pH The mixed-liquor DO and pH were determined at the end of each 24 hour period f o r Run I, II and I I I and continuously monitored i n subsequent runs. A Yellow Springs Instrument Co. Ltd., Model 54 Oxygen Meter was R used f o r a l l DO analyses. For the analysis of pH, a Fisher Acumet Model 210 or . 320 pH Meter was used. 3.4.2 S o l i d s , COD and BODc Mixed-liquor s o l i d s , and mixed l i q u o r and e f f l u e n t COD concentrations were determined twice-a-week throughout the i n v e s t i g a t i o n . The analysis of mixed-liquor TS, SS and VSS were performed according to Standard Methods 2 3, 14th e d i t i o n , whereas the procedure used for,the COD t e s t was adopted from the 12th e d i t i o n , to conform with e a r l i e r i n v e s t i g a t i o n s 9 ' 1 0 . BOD,, t e s t i n g of the mixed-liquor was e a r l i e r eliminated, due to apparent b i o l o g i c a l i n h i b i t i o n . Unseeded BOD,, tes t s on a l l e f f l u e n t s were performed at l e a s t twice during the l a t t e r part of each steady-state period, according to Standard Methods 2 3. I t was found necessary to use -26-seeded d i l u t i o n water for BOD,, analysis of the leachate. 3.4.3 Heavy metals At the end of each run, samples of mixed-liquors e f f l u e n t s and the leachate were "wet-ash" digested according to the recommended EPA procedure 2 5. Heavy metal analysis was determined by atomic absorption (AA) using a J a r r e l l Ash AA, Model 810. For improved s e n s i t i v i t y , a nitrous oxide-acetylene flame was used for aluminum and z i n c . Concentrations of a l l other elements were determined using an.air-ace tylene f1ame. 3.4.4 Others Other parameters such as t o t a l Kjeldahl nitrogen (TKN), ammonia nitrogen (NH^-N), n i t r a t e s (N0 3), t o t a l phosphorus. (TP), t o t a l carbon (TC), t o t a l organic carbon (TOC), a l k a l i n i t y and a c i d i t y were tested as needed, according to Standard Methods 2 3. 3.5 Leachate C h a r a c t e r i s t i c s A l l leachate used i n t h i s i n v e s t i g a t i o n was produced from four of sixteen l a n d f i l l lysimeters, situated at the University of B r i t i s h Columbia. The lysimeters are part of a long-term program, i n i t i a t e d i n 1971, by Dr. R.D. Cameron of the Department of C i v i l Engineering, to investigate the production and composition of l a n d f i l l leachates with time; also being studied i s the e f f e c t of p r e c i p i t a t i o n , cover material, sep t i c tank sludge a d d i t i o n , r e c y c l i n g of leachate and other parameters on the produced leachate. The c h a r a c t e r i s t i c s of the lysimeters are summarized i n Tables 5, 6 and 7. Uloth and M a v i n i c 9 ' 1 0 used leachate generated from lysimeter T, as part of t h e i r i n v e s t i g a t i o n performed i n 1975. The strength of the leachate has since then reduced by more than 50%. -27-TABLE 5 LYSIMETER SYSTEM CHARACTERISTICS26 Lysimeter Refuse"*" Top Cover 61 cm Inter-mediate Cover 15 cm Refuse Saturated p r i o r to Operation Weight kg Wet Density kg/m3 Moisture % H 3556 521 39.9 S o i l - No T 3420 526 34.7 Hog f u e l Hog f u e l No W 3556 523 37.0 S o i l - Yes X 3506 520 35.1 Hog f u e l - Yes Average refuse depth was 244 cm. TABLE 6 LYSIMETER OPERATIONAL CHARACTERISTICS Lysimeter Simulated P r e c i p i t a t i o n , mm/year Septic tank Sludge Additions l i t r e s Recycling ° f 1 leachate H 381 91 No T 381 - No W 381 454 Yes X 381 - Yes Approximately 80% of the leachate was returned to the lysimeter. TABLE 7 COMPOSITION OF REFUSE 2 Category Composition, % Food Waste 11.8 Garden Waste 9.8 Paper Products 47.6 Cardboard 5.4 Te x t i l e s 3.6 Wood 4.7 Metals 8.7 Glass & Ceramics 7.0 Ash, rocks and d i r t 1.4 Total 100.0 -28-Approximately 150 L of leachate were c o l l e c t e d , mixed and stored i n 20 L polyethylene containers at 4°C, throughout the study. Of the 150 L, about 80 were used i n t h i s i n v e s t i g a t i o n . Fellow graduate student, D. Graham, used the remainder i n a bio-chemical t r e a t a b i l i t y study, performed concurrently. The leachate was tested at the end of each run and showed no s i g n i f i c a n t change during the four months of storage. The average c h a r a c t e r i s t i c s of the leachate are given i n Table 8. TABLE 8 LEACHATE CHARACTERISTICS Parameter Concentration * B0D5 13,640 COD 19,250 TC 6,170 TOC 6,115 TS 10,440 TVS 5,810 MLSS 1,040 MLVSS 750 A c i d i t y 3,100 as CaC0 3 (pH = 8 .3) A l k a l i n i t y 4,110 as CaC0 3 (pH = 3 .7) V o l a t i l e Acids 8,505 Acetic Acid PH 5.2 Aluminum 0.62 Calcium 775 Cadmium 0.040 Chromium 0.440 Iron 1225 Lead 0.031 Magnesium 71.5 Manganese 14.0 Nickel 0.18 Nitrogen - TKN 32 - NH4+ <0.05 as N - N03+N02 <0.05 as N Phosphorous - t o t a l 10 Zinc 39.2 * A l l u n i t s , except f o r pH, i n mg/L. -2 9-CHAPTER 4 RESULTS AND DISCUSSION 4.1 Mixed Liquor C h a r a c t e r i s t i c s The mixed-liquor t o t a l s o l i d s (TS) , suspended s o l i d s (MLSS) -and v o l a t i l e s o l i d s (MLVSS) concentrations were monitored throughout the in v e s t i g a t i o n . Steady-state conditions, as determined by mixed-liquor VSS and COD, were generally reached i n l e s s than two weeks i n each run. The steady-state MLSS ranged from 7,400 mg/L f o r a mean c e l l residence time of 20 days at 23°C to 9,000 mg/L at 16°C and a 6 day MCRT. These concentrations are, as expected, higher than those of a conventional a c t i v a t e d sludge plant t r e a t i n g domestic sewage due to the high organic strength of the leachate-feed. However, the s e t t l i n g problems encountered, e s p e c i a l l y at lower MCRT and temperature, are thought to be due to the nature of the fill-and-draw operation (as discussed i n Section 2.2.4), as well as some hindered s e t t l i n g . TABLE 9 MIXED LIQUOR SOLIDS CONCENTRATIONS Parameter Reactor A Reactor B Reactor C MCRT, days 20 6 9 Temperature, °C 23 25 16 9 25 16 9 TS, mg/L 9110 10400 - 11460 9800 - 9570 MLSS, mg/L 7400 8340 8960 8600 7980 8515 7460 MLVSS, mg/L 3930 4670 5970 5880 4390 5425 5445 MLVSS/MLSS 0.53 0.56 0.67 0.68 0.55 0.64 0.73 Table 9, as well as Figure 3, indicate that a l l s o l i d s concentrations increased with decreasing MCRT, r e s u l t i n g i n a f a i r l y constant MLVSS/MLSS r a t i o . As the temperature was lowered to 16°C, the MLVSS/MLSS r a t i o -30-F1G. 3= MLVSS VERSUS MCRT AT ROOM T E M P E R A T U R E . -31-increased from 55% to about 68%, as a r e s u l t of higher MLVSS concentrations. Microscopic examination of the biomass confirmed the presence of various forms of ba c t e r i a , protozoa, free swimming c i l i a t e s and r o t i f e r s i n the 20-day MCRT digester (Reactor A). Fungal growth was v i r t u a l l y absent throughout the experiment. The biomass seemed les s d i v e r s i f i e d at reduced MCRT's and temperatures. Photomicrographs taken of the 6-day MCRT mixed-liquor, at 9°C, revealed a bulky b a c t e r i a l mass and a near absence of other organisms. 4.2 Organic Matter Removal In the case of fill-and-draw reactors, each mean c e l l residence time represents a s p e c i f i c organic loading (MCRT = hydraulic retention time). The F/M r a t i o , however, i s also dependent on the MLVSS concentra-t i o n and hence va r i e s with changing environmental conditions. The organic loadings and F/M r a t i o s used i n t h i s i n v e s t i g a t i o n are l i s t e d i n Table 10. TABLE 10 APPLIED ORGANIC AND F/M LOADINGS Parameter Reactor A Reactor B Reactor C MCRT, days 20 6 9 Temperature, °C 23 25 16 9 25 16 9 Organic Loading/ kg C0D/m3-day 0.96 3.21 3.21 3 .21 2.14 2.14 2 .14 kg B0D5/m3-day 0.68 2.27 2.27 2 .27 1.52 1.52 1 .52 F/M Ratio kg COD/kg MLVSS-day 0.25 0.69 0.54 0 .55 0.49 0.39 0 .39 kg B0D 5/kg MLVSS-day . 0.18 0.49 0.38 0 .39 0.35 0.28 0 .28 In terms of F/M r a t i o , a l l digesters were operated within the suggested range for activ a t e d sludge treatment given i n Table 3. The organic loading rates were s l i g h t l y higher f o r Reactor B and s l i g h t l y lower f o r reactor A. -32-Table 11 shows the c h a r a c t e r i s t i c s and organic removal e f f i c i e n c i e s of four successful aerobic treatment systems reported i n the l i t e r a t u r e . The organic loading and F/M r a t i o range from 1 to 5 kg COD/m3-day and 0.16-0.37 kg COD/kg MLVSS-day, r e s p e c t i v e l y . These values compare well to the loadings used i n t h i s i n v e s t i g a t i o n (see Table 10). TABLE 11 REPORTED ORGANIC LOADINGS AND REMOVAL EFFICIENCIES FOR AEROBIC BIOLOGICAL TREATMENT OF LEACHATE Parameter Boyle & Ham7 Cook & Foree 8 Uloth & M a v i n i c 9 ' 1 0 Chian & DeWalle 3 Temperature, °C 23-25 -22 21-25 -24 MCRT, days 5 10 20 7 Organic loading, kg COD/m3-day 1.04 1.58 2.40 5.02 kg BOD5/m3-day 0.58 0.71 1.80 -F/M r a t i o kg COD/kg MLVSS-day 0.358 0.159 0.373 kg BOD5/kg MLVSS-day - 0.161 0.119 -COD i n f l u e n t , mg/L 6,200 15,800 48,000 35,237 COD e f f l u e n t , mg/L 430 360 594 1,034 COD removal, % 93 97.6 98.8 96.8 BOD5 i n f l u e n t , mg/L 2,900 7,100 36,000 -BOD,, e f f l u e n t , mg/L 200 26 32.4 -BOD,, removal, % 93 99.6 99.9 -MLVSS, mg/L - 4,410 15,100 13,500 Nutrient Addition No No Yes Yes -33-4.2.1 BOD,. b In order to obtain s u f f i c i e n t e f f l u e n t of consistent q u a l i t y , the mixed-liquor was f i l t e r e d rather than s e t t l e d i n a l l but the f i r s t run. Therefore, the BOD,, and COD concentrations obtained r e f l e c t the soluble part of the organic matter, excluding c e l l u l a r materials, and thus give a better picture of the organic matter a v a i l a b l e to the biomass of the p o l i s h i n g reactors. In Reactor A, the s e t t l e d and f i l t e r e d e f f l u e n t BODr were 23 and b 6 mg/L re s p e c t i v e l y , the difference being mainly due to biomass l o s s . Mixed-liquor BOD,, tests were e a r l i e r eliminated, since values obtained showed a s i g n i f i c a n t dependence on d i l u t i o n s used; higher d i l u t i o n gave higher BOD,, concentrations, i n d i c a t i n g a b i o l o g i c a l i n h i b i t i o n (see Table 20, Appendix B) . Nearly a l l of the BOD,, and metals were associated with the b i o l o g i c a l f l o e ; hence, the b i o l o g i c a l i n h i b i t i o n observed was most l i k e l y due to excess metals. Uloth and M a v i n i c 9 ' 1 0 came to a s i m i l a r conclusion i n t h e i r leachate treatment study. The BOD,, of the f i l t e r e d e f f l u e n t was very low for a l l reactors, i n d i c a t i n g that organic "removal" was v i r t u a l l y independent of MCRT and temperatures within the range used i n t h i s study (see Table 12). The term "removal", as used throughout t h i s t h e s i s , i ndicates the t o t a l removal in c l u d i n g that of the f i l t r a t i o n process. An increase i n e f f l u e n t BOD,, was, however, observed at 9°C and 6-day MCRT, but the t o t a l BOD^ removal f o r t h i s reactor was s t i l l 99.3%. The BOD^ tests of the e f f l u e n t s showed no sign of i n h i b i t i o n over a wide range of d i l u t i o n s and seeded t e s t s gave comparable r e s u l t s to unseeded. 4.2.2 COD Mixed-liquor and e f f l u e n t COD tests were performed twice a week throughout the experimental period. These tests were, i n conjunction with MLVSS, used to determine steady-state operation, besides evaluation the organic removal performance of the b i o l o g i c a l treatment system. F i l t e r e d -34-TABLE 12 ORGANIC MATTER REMOVAL IN TERMS OF BOD_ AND COD Parameter Reactor A Reactor B Reactor C MCRT, days 20 6 9 o Temperature, C 23 25 16 9 25 16 9 BODj. i n f l u e n t , mg/L 13,640' 13,640 13,640 13,640 13,640 13,640 13,640 BOD5 e f f l u e n t * , mg/L 6 26 34 97 20 11 27 BOD,, removal, % 99.9 99.0 99.8 99.3 99.9 99.9 99.8 COD i n f l u e n t , mg/L 19,250 19,250 19,250 19,250 19,250 19,250 19,250 COD e f f l u e n t * , mg/L 300 580 515 905 470 360 410 COD removal, % 98.4 97.0 97.3 95.3 97.6 98.1 97.9 * E f f l u e n t was obtained by gra v i t y f i l t r a t i o n u t i l i z i n g Whatman f i l t e r paper No. 4. e f f l u e n t s were used for reasons described i n Section 4.2.1. The s e t t l e d e f f l u e n t from Reactor A t y p i c a l l y had,a COD concentration of 380 mg/L, while f i l t e r i n g reduced i t to 300 mg/L. The lower f i l t e r e d e f f l u e n t COD concentration was: mainly due to s o l i d s l o s t i n f i l t r a t i o n . The mixed-liquor COD concentration increased with decreasing mean c e l l residence time and temperature as d i d the MLVSS. The average mixed-l i q u o r VSS/COD r a t i o s were 0.79, 0.67 and 0.66 for Reactor A, B and C, re s p e c t i v e l y . These r a t i o s and the mixed l i q u o r COD concentrations are shown i n Table 13. With an average i n f l u e n t COD of 19,250 mg/L, the removal e f f i c i e n c y ranged from 95.3% to 98.4%. The COD concentration i n the e f f l u e n t increased s l i g h t l y as the MCRT decreased, as shown i n Table 12 and Figure 4. Temperature d i d not s i g n i f i c a n t l y a f f e c t the COD removal except f o r reactor B a t 9°C. Its e f f l u e n t COD concentration increased from 515 mg/L to 905 mg/L as the temperature was reduced from 16°C to 9°C. -35-F I G . 4 ' REMOVAL OF COD BY REACTOR A . B AND C AT ROOM T E M P E R A T U R E . -36-d e t e r i o r a t i o n of the e f f l u e n t from Reactor B, whereas the e f f e c t on Reactor C was i n s i g n i f i c a n t . TABLE 13 MIXED-LIQUOR COD (MLCOD) CONCENTRATIONS AND MLVSS/MLCOD RATIOS Parameter Reactor A Reactor B Reactor MCRT, days 20 6 9 Temperature, °C 23 25 16 9 25 16 9 MLCOD, mg/L 4980 7100 8795 9200 642 0 8000 8430 MLVSS, mg/L 3930 4670 5970 5880 4390 5425 5445 MLVSS/MLCOD 0.79 0.66 0.68 0.64 0.68 0.68 0.65 4.3 Heavy metal removal The pH, a l k a l i n i t y and a c i d i t y of the leachate were 5.2, 4110 mg/L as CaC0 3 (pH=3.7) and 3100 mg/L as CaC0 3 (pH=8.3), r e s p e c t i v e l y (see Table 8). Immediately a f t e r feeding, the mixed-liquor pH dropped to about 6 but s t a b i l i z e d at 8.3 within 24 hours (as shown i n F i g . 7). The mixed-liquor a c i d i t y was zero and the a l k a l i n i t y 600 mg/L at the end of the 24 hour period. Approximately 70 meq/L a l k a l i n i t y and 84-105 meq/L metal were removed, i n d i c a t i n g that the drop i n a l k a l i n i t y r e s u l t e d mostly from the p r e c i p i t a t i o n of metal hydroxides and metal carbonates (see Appendix C). The e x c e l l e n t removal of most metals was l i k e l y due, i n part, to p r e c i p i t a t i o n caused by high mixed-liquor p H 2 » 3 » 7 > S ' 9 > 1 0 . Sorption of metal ions onto b i o l o g i c a l s o l i d s and subsequent removal by s e t t l i n g may also be an important mechanism, whereas microbial consumption i s thought to be i n s i g n i f i c a n t . In Table 14 are l i s t e d the metal concentrations of the leachate feed and the corresponding removal e f f i c i e n c i e s obtained i n other i n v e s t i g a -t i o n s . The r e l a t i v e order and e f f i c i e n c y of metal removal observed i n t h i s study are: i r o n , manganese, zinc (99.1) > chromium (97.1%) > cadmium -37-(93.3%) > calcium (93.0%) > aluminum (91.0%) > n i c k e l (56.4%) > magnesium (50.8%). (See Table 15). The percent removal e f f i c i e n c i e s are the average f o r Reactors A, D and C under a l l conditions. TABLE 14 REPORTED METAL REMOVAL BY AEROBIC BIOLOGICAL DIGESTERS TREATING LEACHATE Parameter Cook & Foree 8 Uloth & Mavinic 9» 1 0 Chian & DeWalle 3 Leachate Concen-t r a t i o n mg/L Removal E f f i c i e n c y % Leachate Concen-t r a t i o n mg/L Removal E f f i c i e n c y % Leachate Concen-t r a t i o n mg/L Removal E f f i c i e n c y % Aluminum 41.8 98 5 Cadmium 0.39 97 7 Calcium 1200 96.8 1394 98 5 3010 99.6 Chromium 1.9 96 8 Iron 240 >95.8 960 99 7 1020 >99.9 Lead - 1.44 86 1 Magnesium 170 17.6 310 61 6 306 61.0 Manganese 41 98 3 Nickel 0.65 72 3 Zinc 233 99 4 55 • 99.9 pH 5.4 8.4 5.0 8. 7 5.7 8.5 Temperature and mean c e l l residence time had minimal e f f e c t on the removal of metals. As Table 15 shows, the concentration of i r o n , manganese and zi n c i n the e f f l u e n t remained v i r t u a l l y unchanged for the d i f f e r e n t operational and environmental conditions. Aluminum and cadmium experienced s l i g h t l y better removal at higher MCRT's. The removal of aluminum also increased somewhat as l i q u i d temperature decreased. TABLE 15 METAL REMOVAL EFFICIENCIES Parameter Reactor A Reactor B Reactor C Leachate Feed mg/L MCRT, days 20 6 9 -Temperature,°C 23 25 16 9 25 16 9 -pH* 8.2 8.2 8.4 8.4 8.2 8.4 8.4 5.2 Removal i n %: Aluminum 91.9 88.7 87.1 93.5 88.7 91.9 95.2 0.62 Cadmium 97.5 85.0 85.0 97.5 95.0 95.0 97.5 0.040 Calcium 90 .3 94.9 95.7 93.2 93.9 93.1 89.5 775.0 Chromium 98.6 96.6 93.6 97.7 98.2 97.5 97.7 0.440 Iron 99.7 98.8 97.8 99.2 99.6 99.0 99.7 1225.0 Magnesium 47.6 49.9 47.6 60.1 47.6 44.6 58.0 71.5 Manganese 98.6 99.4 99.1 98.8 99.3 99.0 99.2 1400 Nickel 66.7 61.1 55.6 44.4 38.9 66.7 61.1 0.18 Zinc 99.6 99.0 98.3 99.3 99.5 99.1 99.5 39.20 * Mixed-Liquor pH 24 hours a f t e r feeding. 4.4 Temperature E f f e c t s Temperature changes between 9 C and 20 C seem to have minimal e f f e c t s on the b i o s t a b i l i z a t i o n process of leachate. Better than 99% B0D(. was removed from every reactor at a l l temperatures; i n terms of COD, removal e f f i c i e n c i e s i n excess of 97% were experienced i n a l l cases, except f o r a MCRT of 6 days at 9°C. At t h i s l i q u i d temperature, reactor B's ef f l u e n t had s i g n i f i c a n t l y higher COD and BOD,, concentrations i n d i c a t i n g that the biomass was working under stress (see Figure 5). The r e l a t i v e i n s e n s i t i v i t y of the activated sludge process to temperature changes normally encountered i s well e s t a b l i s h e d 6 ' 1 3 ' 1 5 ' 1 6 . At lower temperatures, reduced oxygen u t i l i z a t i o n rate may r e s u l t i n better -39-F I 6 . 5 - - R E M O V A L OF COD FOR R E A C T O R A , B A N D C AT T E M P E R A T U R E R A N G I N G FROM 9 ° - 2 5 ° C . -40-penetration of oxygen i n t o the b i o l o g i c a l f l o e , thus leaving a greater portion aerobic. Since b i o l o g i c a l degradation u s u a l l y i s more e f f i c i e n t under aerobic, rather than anaerobic conditions, the e f f e c t of a lower oxygen u t i l i z a t i o n rate may be reduced or possibly even n u l l i f i e d . At high organic loading, however, increased oxygen penetration may be i n s u f f i c i e n t to compensate f o r the reduced u t i l i z a t i o n r a t e 1 3 . The mixed-liquor v o l a t i l e suspended s o l i d s (MLVSS) concentrations increased by approximately 25%, i n both reactors, when the temperature was reduced from 25°C to 16°C. A further drop to 9°C l e f t the MLVSS v i r t u a l l y unchanged but resulted i n a s i g n i f i c a n t worsening of the e f f l u e n t q u a l i t y of the highest organically-loaded reactor (reactor B). The o v e r a l l oxygen tr a n s f e r e f f i c i e n c y for a b i o l o g i c a l treatment system remains v i r t u a l l y unchanged with a 5°C to 30°C temperature range. The MLVSS concentration u s u a l l y represents approximately 20% organic matter and 80% v i a b l e micro-organisms 5. Hence, the above described e f f e c t s that temperature have on the MLVSS concentrations may have res u l t e d from an increase i n organic material caused by slower b i o l o g i c a l a c t i v i t y . However, the most l i k e l y explanation i s that the i d e a l operating temperature of the dominating b i o l o g i c a l community was lower than 25°C but somewhat higher than 9°C. Temperature d i d not seem to a f f e c t removal of metal ions. Iron, manganese and zinc removal remained unchanged. The removal of aluminum increased s l i g h t l y with decreasing temperature. Results obtained for other elements seemed to vary randomly. 4.5 B i o l o g i c a l P o l i s h i n g Reactors Leachates, from recently deposited l a n d f i l l s , have been reported to reach COD and BOD,, concentrations of 90,000 and 55,000 mg/L r e s p e c t i v e l y , as well as very high concentrations of most metals 5. Aerobic b i o s t a b i l i z a -t i o n of such leachate w i l l remove most of these p o l l u t a n t s but the e f f l u e n t i s not l i k e l y to s a t i s f y federal or p r o v i n c i a l q u a l i t y requirements; -41-hence, some form of a d d i t i o n a l treatment w i l l be required. In t h i s i n v e s t i g a t i o n , i t was decided to look at b i o l o g i c a l p o l i s h i n g , due to the high expected organic content i n the e f f l u e n t . The p o l i s h i n g reactors were operated at 10 and 20 days MCRT i n Run I. In subsequent runs, mean c e l l residence times of 6 and 12 days were used. At 25°C and 16°C the reactors experienced washout due to the excell e n t organic removal by the main digesters; the r e s u l t i n g feed had a BOD^ concentration of only 6-30 mg/L. At 9°C, however, the mixed-liquor v o l a t i l e suspended s o l i d s (MLSS) concentrations s t a b i l i z e d at approximately 150 mg/L for a MCRT of 6 days and at approximately 335 mg/L for 12 days MCRT. "Starvation" i s the most l i k e l y cause f o r the lower MLSS i n the 6 days MCRT reactor. The i n f l u e n t and e f f l u e n t concentrations, as well as the correspond-ing removal e f f i c i e n c i e s f o r several parameters, are given i n Table 16. As shown, the re s i d u a l organic removal was s i g n i f i c a n t , with a 30-60% COD reduction and a BOD,, removal of approximately 80% f o r a l l reactors. The concentration of most heavy metals was only s l i g h t l y reduced, probably due to the very low i n f l u e n t concentrations. Manganese, i r o n and z i n c , however, were reduced by an average of 87, 82 and 62%, re s p e c t i v e l y . As experienced by the f i r s t stage reactors, the performance, i n terms of organic removal, improved with increasing MCRT. Reactor E, operating at an MCRT of 12 days and fed e f f l u e n t from Reactor B (BOD^ = 97 mg/L), experienced the highest removal e f f i c i e n c i e s . 4.6 E f f l u e n t Quality and the PCB Guidelines Aerobic b i o s t a b i l i z a t i o n of the greenish-black and strong smelling leachate r e s u l t e d i n odour-free e f f l u e n t s of s l i g h t l y yellow colour. Other c h a r a c t e r i s t i c s of the e f f l u e n t produced, as well as t h e i r maximum permissible concentrations s p e c i f i e d by the B r i t i s h Columbia P o l l u t i o n Control Board (PCB) Ob j e c t i v e s 4 , are l i s t e d i n Table 17. -42-TABLE 16 PERFORMANCE OF BIOLOGICAL POLISHING REACTORS AT 9°C Parameter Reactor D Reactor E Reactor F Reactor G MCRT, days 6 12 6 12 Organic Loading, kg COD/m -day 0.15 0.075 0.068 0.034 F/M, kg BOD5/kg MLVSS-day 0.111 0.021 0.02 9 0.008 MLVSS, mg/L 145 380 155 290 MLVSS/MLSS, % 58.0 62.3 70.5 62.4 pH* 8.8 8.8 8.9 8.9 COD i n f l u e n t , mg/L 905 905 410 410 e f f l u e n t , mg/L 505 365 295 275 removal, % 44.2 59.7 28.0 32.9 BODj. i n f l u e n t , mg/L 97 97 27 27 e f f l u e n t , mg/L 20 16 5 5 removal, % 79.4 83.5 81.5 81.5 Manganese** i n f l u e n t , mg/L 0.166 0.166 0.119 0.119 e f f l u e n t , mg/L 0.023 0.010 0.014 0.022 removal, % 86.1 94.0 88.2 81.5 Iron i n f l u e n t , mg/L 10.0 10.0 4.0 4.0 e f f l u e n t , mg/L 2.80 1.40 0.45 0.80 removal, % 72.0 86.0 88.8 80.0 Zinc i n f l u e n t , mg/L 0.29 0.29 0.20 0.20 e f f l u e n t , mg/L 0.15 0.09 0.07 0.07 removal, % 48.2 69.0 65.0 65.0 * Mixed-liquor pH 24 hours a f t e r feeding. ** Other heavy metals experienced i n s i g n i f i c a n t removal. -43-TABLE 17 CHARACTERISTICS OF EFFLUENT PRODUCED. BY FIRST STAGE AEROBIC BIOSTABILIZATION OF LEACHATE Parameter Reactor A Reactor B Reactor C PCB4 Guidelines MCRT, days 20 6 9 Temperature, °C 23 25 16 9 25 16 9 COD, mg/L 300 580 515 905 470 360 410 -BOD5, mg/L 6 26 34 97 20 11 27 45 Aluminum, mg/L 0.05 0.07 0.08 0.04 0.07 0.05 0.03 0.5 Cadmium, mg/L 0.001 0.006 0.006 0.001 0.002 0.002 0.001 0.005 Calcium, mg/L 75.0 39.6 35.5 53.0 47.0 48.7 81.2 -Chromium, mg/L 0.006 0.015 0.028 0.010 0.008 0.011 0.010 0.10 Iron, mg/L 3.2 15.0 27.1 10.0 5.2 12.6 4.0 0.3 Magnesium, mg/L 37.5 35.8 37.5 28.5 37.5 39.6 30.0 -Manganese, mg/L 0.193 0.084 0.130 0.166 0.092 0.142 0.119 0.05 Ni c k e l , mg/L 0.06 0.07 0.08 0.10 0.11 0.06 0.07 0.3 Zinc, mg/L 0.16 0.39 0.67 0.29 0.18 0.35 0.20 0.5 In terms of organic matter, the e f f l u e n t s from a l l f i r s t stage reactors, except Reactor B operating at 9°C, were s a t i s f a c t o r y . Of the heavy metals, only i r o n and manganese were present i n concentrations s i g n i f i c a n t l y higher than s p e c i f i e d i n the guidelines. The p o l i s h i n g reactors f a i l e d a t a l l temperatures, except at 9°C, due to the excellent performance of the main reactors. At t h i s temperature, organic matter and metal concentrations were further reduced, thus r e s u l t i n g i n e f f l u e n t s that s a t i s f i e d PCB P o l l u t i o n Control Objectives f o r a l l parameters except ir o n (see Table 18). The iro n concentrations, however, were very low (0.5 - 2.8 mg/L); hence, a d d i t i o n a l treatment i s not l i k e l y to be required. -44-I t should be noted t h a t a l l e f f l u e n t s were ob ta ined by g r a v i t y f i l t r a t i o n , through Whatman f i l t e r paper No. 4 f o r reasons d i s cus sed i n S e c t i o n 4.2.1. Therefore , under f i e l d c o n d i t i o n s , h ighe r e f f l u e n t s o l i d s concen t r a t i ons would be expected . TABLE 18 EFFLUENT CHARACTERISTICS OF BIOLOGICAL POLISHING TREATMENT Parameter Reactor D Reactor E Reactor F Reactor G PCB4 G u i d e l i n e s MCRT, days 6 12 6 12 COD, mg/L 505 365 295 275 -BOD 5 , mg/L 20 16 5 5 45 Manganese, mg/L 0.023 0.010 0.014 0.022 0.05 I r o n , mg/L 2.80 1.40 0.45 0.80 0.3 Z i n c , mg/L 0.15 0.09 0.07 0.07 0.5 4.7 E f f e c t s o f the F i l l - a n d Draw Procedure Three c r i t e r i a d i c t a t e d the use o f ba t ch r e a c t o r s i n t h i s l eacha te t r e a t a b i l i t y s tudy . F i r s t l y , t h i s system i s more s t a b l e and l e s s t ime consuming. Secondly , i t was d e s i r a b l e t o keep the exper imenta l methods and m a t e r i a l s as c l o s e as p o s s i b l e t o p rev ious i n v e s t i g a t i o n s performed a t the U n i v e r s i t y o f B r i t i s h Columbia , i n order t o t i e i n t o t h i s work. F i n a l l y and most impor tan t , the a v a i l a b l e q u a n t i t y o f leacha te p l a i n l y p r o h i b i t e d the use o f con t inuous - f low r e a c t o r s . The l i t e r a t u r e c l e a r l y i n d i c a t e s tha t ba tch system and t r a n s i e n t o rgan ic l oad ings may s e v e r e l y a f f e c t the s e t t l i n g c h a r a c t e r i s t i c s o f a p a r t i c u l a r m i x e d - l i q u o r 1 7 ' 1 8 (see S e c t i o n 2.2.4). I t i s suggested t h a t b u l k i n g may occur as a r e s u l t o f repeated shock l o a d i n g s o f o r g a n i c , a c i d i c o r t o x i c m a t e r i a l 1 9 ' 2 0 ' 2 2 . Sudden i nc r ea se s i n i n f l u e n t o rgan ic s may -45-also increase the growth rate, as w e l l as reduce the production of extra c e l l u l a r slime; hence, the a b i l i t y of the biomass to form proper b i o l o g i c a l f l o e s could be i m p a i r e d 1 7 ' 1 8 . S e t t l i n g problems were r e a d i l y encountered i n t h i s i n v e s t i g a t i o n . In Run I (MCRT = 20 days, Temperature = 23°C), the mixed-liquor's s e t t l i n g c h a r a c t e r i s t i c s varied s i g n i f i c a n t l y , f o r no apparent reason. Figure 6 shows the range of s e t t l i n g performance, as well as the appearance of the e f f l u e n t s . B r i e f l y , slower sludge s e t t l i n g produced c l e a r e r supernatant. The s e t t l i n g c h a r a c t e r i s t i c s deteriorated s i g n i f i c a n t l y with decreasing MCRT and temperature to a point where 30 minutes of s e t t l i n g produced only 3% of very t u r b i d e f f l u e n t (MCRT = 6 days, temperature = 9°C). A l l s e t t l i n g t e s t s were performed according to Standard Methods 2 3. Since the a b i l i t y of the mixed-liquor to separate i s v i t a l to the activated sludge process, an a d d i t i o n a l study was performed. The purpose of t h i s study was to support the suggestion that the nature of the batch process, rather than the biomass' reaction to the leachate feed, caused part of the s e t t l i n g problems encountered. Reactor B (MCRT = 6 days) was monitored at 9°C during several 24 hour periods. The r e s u l t s are depicted i n Figures 7 and 8. Immediately a f t e r feeding, the DO concentration dropped to near zero and remained low for the next 4-5 hours before r a p i d l y r i s i n g to near saturation l e v e l . As shown i n Table 8, the leachate contained e a s i l y assimilated organics ( i e . V o l a t i l e Acids = 8500 mg/L as Acetic a c i d ) , s i g n i f i c a n t concentrations of metals ( i e . Iron = 1220 mg/L) and had zero DO concentration; hence, e s s e n t i a l l y the leachate possessed Immediate Dissolved Oxygen Demand (IDOD). The immediate DO drop res u l t e d from a combination of increased b i o l o g i c a l a c t i v i t y , d i l u t i o n and oxidation of metals. The f a c t that the DO rose so ra p i d l y a f t e r remaining near zero f o r 4-5 hours, i n d i c a t e s that DO concen-t r a t i o n was c o n t r o l l e d by a zero-order metal oxidation process. -46-I 2 0 0 3 0 0 * ' 1 1 0 I 2 3 S e t t l i n g t i m e , hours FIG.6-- R A N G E OF S E T T L I N G P E R F O R M A N C E OF R E A C T O R A. -47-F I G . 7 ' M I X E D L I Q U O R V O L A T I L E S U S P E N D E D S O L I D S , D I S S O L V E D O X Y G E N A N D pH B E T W E E N L E A C H A T E A D D I T I O N S O F R E A C T O R B A T 9 ° C . -48-FIG.8* S O L U B L E E F F L U E N T COD AND B 0 D 5 B E T W E E N F E E D I N G S OF R E A C T O R B AT 9 ° C . -49-The leachate addition also caused the mixed-liquor pH to drop to approximately 6, before r a p i d l y approaching former l e v e l s . In add i t i o n , the MLVSS concentration dropped to about 5100 mg/L as a r e s u l t of mere d i l u t i o n . The growth rate subsequently increased tremendously and the i n i t i a l MLVSS concentration of 6000 mg/L was reached i n 4 hours. The MLVSS peaked a f t e r 6 hours, at 6100 mg/L, and then endogenous r e s p i r a t i o n dominated f o r the next 18 hours. This corresponds well to the e f f l u e n t COD and BOD,, concentrations shown i n Figure 8. The concentrations of these parameters escalated r a p i d l y , due to the added soluble organic matter, but nearly a l l of the substrate was u t i l i z e d within 6 hours. Because there was usable leachate remaining, Reactor B was then operated on twice-a-day feeding schedule, but s t i l l at MCRT of 6 days, i n order to determine the e f f e c t s of reduced feed volumes. The mixed-l i q u o r DO, pH and VSS, as well as e f f l u e n t COD and BOD,., a l l behaved as previously noted f o r the once-a-day operation. Neither was any improve-ment of the s e t t l i n g c h a r a c t e r i s t i c s observed. However, i t i s believed that, as the time between feedings i s further reduced and the shock loading e f f e c t s diminished, the s e t t l i n g performance would indeed improve. -50-CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 5.1 Conclusions ; 1. Aerobic b i o s t a b i l i z a t i o n was shown to be an e f f e c t i v e method of t r e a t i n g high-strength leachate, as long as s u f f i c i e n t time i s provided f o r a c c l i m a t i z a t i o n . Using mixed-liquor from a domestic activated-sludge plant, an i n i t i a l a c c l i m a t i z a t i o n period of 3-4 weeks was s u f f i c i e n t . 2. At steady-state, aerobic digestion of t h i s leachate may be operated at: a mean c e l l residence time as low as 6 days, an organic loading as high as 3.21 kg C0D/m3-day and a F/M r a t i o of up to 0.5 kg BOD^/kg MLVSS-day, without s i g n i f i c a n t s a c r i f i c e of performance. 3. For an i n f l u e n t strength of approximately 19,000 mg/L COD and 14,000 mg/L BOD,., removals of better than 95% COD and 99% BOD5 were achieved at l i q u i d temperatures.ranging from 9 to 25°C. 4. The high mixed-liquor pH of 8.3 i s believed to be the main reason f o r the s i g n i f i c a n t metal removal. Sorption of metal ions onto b i o l o g i c a l s o l i d s i s also important but the microbial consumption i s most l i k e l y i n s i g n i f i c a n t . The r e l a t i v e order and average metal removal e f f i c i e n c i e s were: i r o n , manganese, zinc (99.1%) > chromium (97.1%) > cadmium (93.3%) > calcium (93.0%) > aluminum (91.0%)> n i c k e l (56.4%) > magnesium (50.8%) . 5. The mean c e l l residence time d i d not s i g n i f i c a n t l y a f f e c t metal removals. A longer MCRT i s l i k e l y to improve the removal e f f i c i e n c i e s s l i g h t l y for aluminum and cadmium. 6. Within the range of 9-25°C, temperature was not an important fa c t o r f o r the metal removal. However, s l i g h t l y better e f f i c i e n c i e s were r e a l i z e d at lower temperatures for aluminum. Iron, manganese and zinc .removals were unaffected by temperature, whereas r e s u l t s obtained f o r other elements, appeared to vary randomly. 7. The mixed-liquor VSS increased from approximately 3900 mg/L to approximately 6000 mg/L, with decreasing mean c e l l residence time, and temperature reduction to 16°C. A further drop i n temperature to 9°C d i d not a f f e c t the MLVSS concentration. For a temperature o o range of 9 C ;to 25 C, the average mixed-liquor VSS/COD r a t i o s were 0.79, 0.67 and 0.66 for MCRT's of 20, 6 and 12 days, r e s p e c t i v e l y . .8. The performance of a l l reactors fed leachate, were exce l l e n t and produced f i l t e r e d e f f l u e n t s (Whatman No. 4 f i l t e r paper) that meet the l o c a l p o l l u t i o n c o n t r o l objectives f o r nearly a l l parameters, under most conditions. 9. B i o l o g i c a l p o l i s h i n g of f i r s t stage e f f l u e n t s was not f e a s i b l e at higher temperatures, due to the low r e s i d u a l concentration of biodegradable organic material. I t was only marginally operational at 9°C, the lowest temperature investigated. At t h i s temperature, 45% BODj. and 80% COD removal was achieved, as well as a further reduction of some metal concentrations. 10. Bulking, d e f l o c c u l a t i o n and some hindered s e t t l i n g (MLSS = 7400 -9000 mg/L), produced a slow s e t t l i n g sludge and a t u r b i d e f f l u e n t . The s e t t l i n g c h a r a c t e r i s t i c s deteriorated with decreasing mean c e l l residence time and temperature. As reported by others, the s e t t l e a b i l i t y of batch systems vary widely. The s e t t l i n g problems -52-r e s u l t mainly from the repeated shock loadings of the fill-and-draw procedure, rather than biomass' reaction to the feed. Therefore, a continuous-flow process, e s p e c i a l l y i f completely mixed, should possess good s e t t l i n g properties, besides having a removal per-formance comparable to that of a batch system. Recommendations A l l of the metal removed i s associated with the sludge s o l i d s . The treatment and f i n a l disposal of t h i s sludge mass i s of v i t a l importance to successful treatment of l a n d f i l l leachates and should be studied further. Studies to determine the minimum requirements of nitrogen and phosphorus for aerobic s t a b i l i z a t i o n of leachate may reduce or completely eliminate the need for d a i l y nutrient addition. A study should be undertaken to determine the e f f e c t of "reduced time" between feedings on operational and s e t t l i n g performance of bioreactors t r e a t i n g leachate. Due to the high cost of a separate treatment system, as well as the annual and l i f e t i m e changes i n volume and strength of leachate, the impact of leachate addition to domestic sewage needs further i n v e s t i g a t i o n . -53-REFERENCES 1. Zanoni, A.E., "Ground Water 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, Wis. U.S.A., 1971. 2. Chian, E.S.K. and DeWalle, F.B., "Sanitary L a n d f i l l s and Their Treatment", Journal of the Environmental Engineering D i v i s i o n , ASCE, Vol.102, No. EE2, A p r i l 1976, pp. 411-431. 3. Chian, E.S.K. and DeWalle, F.B., "Evaluation of Leachate Treatment: B i o l o g i c a l and Physical-Chemical Processes", O f f i c e of Research and Development, U.S. Environmental Protection Agency, EPA-600/2-77-186b, Vol . I I , November 1977. 4. " P o l l u t i o n Control Objectives f o r Municipal Type Waste Discharges i n B r i t i s h Columbia", Dept. of Lands, Forests, and Water Resources, Water Resource Service, V i c t o r i a , B.C., Sept. 1975. 5. 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 Receiving Waters", 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. 6. Metcalf and Eddy, Inc., "Wastewater Engineering: C o l l e c t i o n , Treatment, Disposal", McGraw H i l l , New York, 1972. 7. 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", Jour, of Water P o l l u t i o n Control Federation, Vol. 46, No. 5, May 1974, pp. 860-872. 8. Cook, E.N. and Foree, E.G., "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, Vol. 46, No. 2, February 1974, pp. 380-392. 9. Uloth, V.C. and Mavinic, D.S., "Aerobic B i o s t a b i l i z a t i o n of a High Strength L a n d f i l l Leachate", B.C. Dept. of Environment, S o l i d Waste Technical Report No. 7, V i c t o r i a , B.C., Canada, February 1976, 110 pages. 10. Uloth, V.C. and Mavinic, D.S., "Aerobic Biotreatment of a High-Strength Leachate", Jour, of the Environmental Engineering D i v i s i o n , ASCE, Vo l . 103, No. EE4, Proc. Paper 13130, August 1977, pp. 647-661. 11. Cheng, M.H., Patterson, J.W. and Minear, R.A., "Heavy Metals Uptake by Activated Sludge", Jour, of Water P o l l u t i o n Control Federation, Vol.47, No.2, February 1975, pp. 362-376. 12. Neufeld, R.D. and Hermann, E.R., "Heavy Metal Removal by Acclimated Activated Sludge", Jour, of Water P o l l u t i o n Control Federation, V o l . 47, No. 2, February 1975, pp. 210-329. 13. Eckenfelder, W.W., J r . , "Theory of B i o l o g i c a l Treatment of Trade Wastes", Jour, of Water P o l l u t i o n Control Federation, Vol. 39, No. 2, February 1967, pp. 240-250. -54-14. Sayigh, B.A. and Malina, J.F., J r . , "Temperature E f f e c t s on the Activated Sludge Process", Jour, of Water P o l l u t i o n Control Federa-t i o n , V o l . 50, No. 4, A p r i l 1978, pp. 678-687. 15. Friedmann, A.A. and Schroeder, E.D., "Temperature E f f e c t s on Growth and Y i e l d of Activated Sludge", Jour, of Water P o l l u t i o n Control Federation, V o l . 44, No. , 1972, pp. 1433-16. Benedict, A.H. and Carlson, D.A., "Temperature Acclimation i n Aerobic Bio-Oxidation Systems", Jour, of Water P o l l u t i o n Control Federation, V o l . 45, No.l, January 1973, pp. 10-24. 17. Selna, M.W. and.Schroeder, E.D., "Response of Activated Sludge Processes to Organic Transient I - K i n e t i c s " , Jour, of Water P o l l u t i o n Control Federation, V o l . 50, No. 5, May 1978, pp. 944-956. 18. Selna, M.W. and Schroeder, E.D., "Response of Activated Sludge Processes to Organic Transient II - Stoichiometry", Jour, of Water P o l l u t i o n Control Federation, V o l . 51, No. 1, January 1979, pp. 150-157. 19. Pipes, W.O., "Types of Activated Sludge Which Separate Poorly", Jour, of Water P o l l u t i o n Control Federation, Vol. 41, No. 5, Part 1, May 1969, pp. 714-724. 2.0. Pipes, W.O., "Bulking, Def l o c c u l a t i o n , and Pinpoint Floe", Jour. of Water P o l l u t i o n Control Federation, V o l . 51, No. 1, January 1979, pp. 62-70. 21. Sezgin, M., Jenkins, D., and Parker, D.S., "A United Theory of Filamentous Activated Sludge Bulking", Jour, of Water P o l l u t i o n Control Federation, V o l . 50, No. 2, February 1978, pp. 362-381. 22. Hoepker, E.C. and Schroeder, E.D., "The E f f e c t s of Loading Rate on Batch-Activated Sludge E f f l u e n t Quality", Jour, of Water P o l l u t i o n Control Federation, Vol. 51, No. 2, February 1979, pp. 264-273. 23. APHA, AWWA, and WPCF, "Standard Methods f o r the Examination of Water and Wastewater", American Public Health Association, Inc., 14th e d i t i o n , 1975. 24. APHA, AWWA, and WPCF, "Standard Methods f o r the Examination of Water and Wastewater", American Public Health Association, Inc., 12th e d i t i o n . 25. "Methods f o r Chemical Analysis of Water and Wastes", U.S. Environ-mental Protection Agency, Water Quality Laboratory, C i n c i n n a t i , Ohio, 1971. 26. Cameron, R.D., Phelps, D.H., and McDonald, E.C., "Investigation of Leaching from Simulated L a n d f i l l s - Progress Report No. 1", Dept. of C i v i l Engineering, Faculty of Applied Science, U n i v e r s i t y of B r i t i s h Columbia, July 1975. -55-APPENDICES -56-APPENDIX A: KINETICS An e m p i r i c a l l y developed r e l a t i o n s h i p between b i o l o g i c a l growth and substrate u t i l i z a t i o n that i s commonly used f o r b i o l o g i c a l systems s t a b i l i z i n g organic and/or inorganic wastes i s : 6 dt = Y dt " V (A-1} dX where — = net growth rate of microorganisms, mass/volume-time Y = growth y i e l d c o e f f i c i e n t , mass of organisms/mass of substrate u t i l i z e d dF dt rate of substrate u t i l i z a t i o n by microorganisms, mass/volume-time (A.2) k^ = microorganisms - decay c o e f f i c i e n t , time X = concentration of microorganisms, mass/volume The rate of substrate u t i l i z a t i o n by microorganisms may be approximated by: dF _ k XS dt K +S s where k = maximum rate of waste u t i l i z a t i o n per u n i t weight of microorganisms, time--*-K = waste concentration a t which rate of waste u t i l i z a t i o n 3 per u n i t weight of microorganisms i s one-half the maximum rate, mass/volume S = concentration of waste surrounding the microorganisms, mass/volume. The mean c e l l residence time (MCRT), 0 , and the food-to-microorganisms (F/M) , are inv e r s e l y r e l a t e d as shown i n Equation A (A.3). Tbe desired treatment e f f i c i e n c y can be obtained by c o n t r o l l i n g e i t h e r MCRT or F/M. The MCRT i s easier to measure and was hence used i n t h i s i n v e s t i g a t i o n as a design and operating parameter. -57-1 = Y ^ - - k d = ^ | - k d (A.3) 6 X d - K +S a The k i n e t i c s of b i o l o g i c a l wastewater treatment also depend on the type of reactor used and i t s mode of operation. The completely mixed, semi-continuous reactor used i n t h i s study may be approximated by a series of continuous-flow, completely mixed reactors without c e l l u l a r r e c y c l e . The nth time i n t e r v a l of one fill-and-draw cycle represents the nth complete-mix reactor r e c e i v i n g i t s i n f l u e n t from reactor (n-1) and discharging to reactor (n+1). At steady-state, the f i r s t - o r d e r substrate removal for one fill-and-draw cycle ( i . e . n time i n t e r v a l s ) i s : 6 ^ = i — (A.4) o (1 + kV/Q) n where Q = flow rate C = i n f l u e n t substrate concentration o C = e f f l u e n t substrate concentration n k = substrate removal rate n = number of time i n t e r v a l s i n one fill-and-draw cycle V = reactor volume. For n=l the system becomes a continuous-flow, completely mixed reactor without c e l l u l a r r e c y c l e . However, as n increases, the treatment process k i n e t i c s approach those of a plug-flow reactor. -58-Determination of k and K s Rearranging and d i v i d i n g each side of equation (A.2) with X gives: *~— (^ r-) + r (A. 5) AF/At k S k e K X 1 s P l o t t i n g '^F'/^t vs — should y i e l d a s t r a i g h t l i n e with slope — and I i n t e r c e p t — (see Figure 9). Determination of Y and k, a Dividing each side of equation (A.l) by X y i e l d s : W A t _ AF/At ( . x " Y x k d * A* b' A p l o t of v s AF/At s n o u ] _ ^ give a s t r a i g h t l i n e with slope X X Y and inter c e p t - y i ( s e e Figure 10), For determination of the k i n e t i c parameters k, K g, Y and k^ a minimum of three data points are required. Thus, Figure 9 and 10 show the k i n e t i c s f o r the b i o l o g i c a l system at room temperature only. The two data points obtained each at 16°C and 9°C are included i n Table 19 f o r general i n t e r e s t . Soluble ( f i l t e r e d ) BOD,, concentrations were used f o r the determination of the k i n e t i c parameters. -59-TABLE 19 DATA FOR DETERMINATION OF KINETIC PARAMETERS Parameter Reactor A Reactor B Reactor C 0 , days 20 6 9 AX/At 1 ^ - 1 X " e ' d a y c 0.05 0.167 0.111 S Q, mg/L 13,640 13,640 13,640 Temperature, °C 23 25 16 9 25 16 9 X, mg/L 3930 4670 5970 5880 4390 5425 5445 S g, mg/L 6 26 34 97 20 11 27 ~ - , L/mg e 0.167 0.038 0.029 0.010 0.050 0.091 0.037 AF/At ' d a y 5.76 2.06 2.63 2.61 2.90 3.58 3.60 AF/At ^ -1 x ' d a y 0.173. 0.486 0.380 0.384 0.345 0.279 0.278 TABLE 2Q KINETIC PARAMETERS BASED ON SOLUBLE BOD5 CONCENTRATIONS AT ROOM TEMPERATURE Parameter Results k, days 0.74 K g, mg/L 19.6 Y 0.374 k d ' d a y 1 0.015 (0 >» o < 0 0 S l o p e = = 2 6 . 4 1 / . K«.= 19 .6 m g / £ k = 0 . 7 4 day 0.04 Se 0.08 • £ / m g 0.12 0.16 i cn O I FIG.9 = DETERMINATION OF k AND K s BASED ON SOLUBLE B 0 D 5 CONCENTRATION 0.1 0.2 0.3 0.4 0.5 A F / A t _, • day FIG.IO-DETERMINATION OF y A N D K d B A S E D ON S O L U B L E B O D 5 C O N C E N T R A T I O N . -62-APPENDIX B: SUPPLEMENTARY RESULTS TABLE 21-F i r s t Stage E f f l u e n t Concentrations Parameter Reactor A Reactor B Reactor C MCRT, days 20 6 6 9 9 Temperature, °C 23 25 16 25 16 TKN, mg/L 12.2 21.6 - 16.8 -NH^, mg/L as N 11.8 - - - -N0 2 + N0 3, mg/L as N 8.1 - - - -TP, mg/L 0.6 - - - -A l k a l i n i t y , mg/L (pH=3.7) - 565 - 600 -A c i d i t y , mg/L (pH=8.3) 0 0 0 0 0 TC, mg/L 260 335 315 310 262 TOC, mg/L 125 247 206 255 141 TABLE 22 Mixed-Liquor BOD,., mg/L, Versus D i l u t i o n D i l u t i o n Reactor A Reactor B Reactor C 1:1000 2460 990 740 1:750 2020 1005 604 1:600 1960 514 564 1:500 1810 - -1:429 1680 - --63-TABLE 23 Mixed-Liquor COD, TC and TOC i n mg/L Reactor MCRT, days Temperature °C COD, mg/L TC mg/L TOC, mg/L A 20 23 4980 2185 1500 25 7100 2865 2300 B 6 16 8795 - -9 9200 - -25 6420 2565 1775 C 9 16 7600 - -9 8430 - --64-APPENDIX C: ALKALINITY REMOVAL Average a l k a l i n i t y concen t r a t i ons o f l eacha te feed and f i r s t -stage e f f l u e n t were 4,110 mg/L and 600 mg/L as CaCO^ r e s p e c t i v e l y . This represen ts a removal o f about 3,500 mg/L or 70 meq/L. An approx-imate t o t a l meta l removal i n meq/L i s shown i n Table 24. TABLE 24 AVERAGE METAL REMOVALS BY FIRST-STAGE REACTORS Element Average Meta l Removals mg/L meq/L Aluminum 0.57 0.1 Cadmium 0.039 -Calc ium 700 35 Chromium 0.38 -I ron 1220 43.5-65.3* Magnesium 35 2.9 Manganese 13.9 0.5 N i c k e l 0.12 -Zinc 39 1.2 83.2-105.0 * As Fe and Fe 

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.831.1-0062564/manifest

Comment

Related Items