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Anaerobic co-digestion of fruit juice and municipal bio-waste in the Okanagan Valley Barrantes Leiva, Mariel 2013

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Anaerobic Co-digestion of Fruit Juice and Municipal Bio-waste in the Okanagan Valley by Mariel Barrantes Leiva  B.Sc. National University of Costa Rica, 2010  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE  in  THE COLLEGE OF GRADUATE STUDIES  (Civil Engineering)  THE UNIVERSITY OF BRITISH COLUMBIA  (Okanagan)  May 2013 © Mariel Barrantes Leiva, 2013  Abstract Fruit harvesting and juice making is one of the most important sectors in the Okanagan Valley. Fruit- juice production generates industrial wastewater with high organic strength that needs to be treated, generally on-site, prior to being discharged to the municipal wastewater treatment system. In the Okanagan Valley, the organic residuals of fruit-juice wastewater treatment, such as screen cake and thickened waste activated sludge, are currently being sent to local landfills or composting facilities, which is not desirable. Given the growing interest in utilizing industrial, agricultural and municipal waste streams in centralized bioreactors for optimized energy (biogas) recovery, this study evaluated the anaerobic co-digestion performance of industrial organic streams from Sun-Rype Products Ltd. wastewater treatment facility with municipal waste sludge cake from Kelowna’s municipal wastewater treatment plant. Excess landfill leachate source at the Glenmore Landfill was also utilized to dilute some of the concentrated streams and provided additional buffering capacity. Both single and co-digestion scenarios were tested in laboratory-scale mesophilic and thermophilic semi-continuous flow digesters at sludge retention times of 20 and 10 days, corresponding to organic digester loading rates of 1.414.80 g chemical oxygen demand /L/day. Digestion studies demonstrated that co-digestion of fruit-juice streams with municipal sludge cake and leachate resulted in more stable operation even at the higher loading due to additional buffering capacity available compare to single scenarios. In addition, organic removal efficiencies were higher for the codigestion scenarios. Furthermore, dewaterability of municipal sludge cake was enhanced by the addition of industrial secondary sludge. Thermophilic digestates could qualify under Class A biosolids according to Organic Matter Recycling Regulation (OMRR) of BC in terms of coliform presence; however presence of higher coliforms at mesophilic digestion temperatires downgraded the mesophilic digestates to Class B biosolids. Finally, ppreliminary cost analysis indicated an overall saving of $10.52 million ($2 million in capital and $8.52 million in operational) over 25-year period for a co-digestion scenario utilizing all waste streams over building/operating two separate digesters for municipal and industrial waste streams.  ii  Preface Some parts of this study were presented in 2013 British Columbia Water and Waste Association (BCWWA) Annual Conference (April 20-24, Kelowna, BC, Canada). An abstract has been accepted for presentation at the International Water Association (IWA) 13th World Congress on Anaerobic Digestion: Recovering (bio) Resources for the World (June 25-28, Santiago de Compostela, Spain). A poster will be presented in 2013 II Tall Buildings and Sustainable Cities Congress (June 22-24, San José, Costa Rica).  iii  Table of Contents Abstract ................................................................................................................................ ii Table of Contents ................................................................................................................iv List of Tables ..................................................................................................................... vii List of Figures ......................................................................................................................xi List of Symbols and Abbreviations ................................................................................... xv Acknowledgements ............................................................................................................xvi Chapter 1: Introduction .................................................................................................. 1 1.1 Background and motivation................................................................................... 1 1.2 Objectives .............................................................................................................. 5 1.3 Thesis organization ................................................................................................ 6 Chapter 2: Literature review .......................................................................................... 7 2.1 Fruit juice industry in the Okanagan Valley .......................................................... 7 2.2 Treatment processes for wastewaters .................................................................. 10 2.2.1 Treatment processes for fruit juice wastewaters ........................................... 10 2.2.2 Treatment processes for raw sewage ............................................................. 13 2.3 Landfill sites ........................................................................................................ 14 2.4 Anaerobic digestion as proposed treatment ......................................................... 15 2.4.1 Hydrolysis phase ........................................................................................... 17 2.4.2 Acidogenesis.................................................................................................. 18 2.4.3 Acetogenesis .................................................................................................. 19 2.4.4 Methanogenesis ............................................................................................. 20 2.5 Control parameters of anaerobic process ............................................................. 20 2.5.1 Physical factors .............................................................................................. 20 2.5.1.1 Temperature ............................................................................................ 21 2.5.1.2 Hydraulic and solids retention time ........................................................ 21 2.5.1.3 Volumetric organic loading rate (OLR) .................................................. 22 2.5.1.4 Continuous feed ...................................................................................... 22 iv  2.5.1.5 Mixing ..................................................................................................... 23 2.5.1.6 Characteristics of the substrate ............................................................... 23 2.5.2 Chemical factors ............................................................................................ 23 2.5.2.1 pH ............................................................................................................ 23 2.5.2.2 Toxicity ................................................................................................... 24 2.5.2.3 Nutrients .................................................................................................. 24 2.6 Anaerobic co-digestion ........................................................................................ 25 2.7 Biogas as a global renewable energy ................................................................... 28 2.8 Summary.............................................................................................................. 30 Chapter 3: Materials and methods ............................................................................... 32 3.1 Industrial and municipal waste samples .............................................................. 32 3.1.1 Municipal (sewage) sludge cake ................................................................... 32 3.1.2 Industrial (fruit-juice) waste streams ............................................................. 35 3.1.3 Landfill leachate ............................................................................................ 39 3.2 Inocula samples used as digester seed and acclimation ...................................... 40 3.3 Anaerobic co-digestion studies ............................................................................ 41 3.4 Volumetric ratios for co-substrates in digester feed streams ............................... 43 3.5 Characterization of samples................................................................................. 44 3.5.1 Total solids and volatile solids ...................................................................... 45 3.5.2 Chemical oxygen demand (COD) ................................................................. 45 3.5.3 Alkalinity ....................................................................................................... 46 3.5.4 Ammonia ....................................................................................................... 46 3.5.5 Gas Chromatography for volatile fatty acids (VFAs) and biogas composition .............................................................................................................. 46 3.5.6 Dewaterability ............................................................................................... 47 3.5.7 Total coliforms .............................................................................................. 47 Chapter 4: Results and discussion ................................................................................ 48 4.1 Characterization of raw industrial and municipal waste streams ........................ 48 4.2 Characterization of diluted industrial and municipal waste streams ................... 49 4.3 Inoculum acclimation to waste streams studied .................................................. 51 v  4.4 Effect of addition of co-digestion materials on digester performance ................ 53 4.5 Effect of addition of co-digestion materials on digester supernatant characterization ............................................................................................................ 66 4.6 Land application of digested biosolids according to regulations ........................ 69 4.6.1 Dewaterability ............................................................................................... 70 4.6.2 Pathogens ....................................................................................................... 73 4.7 Approximate cost functions for single and co-digestion treatment facilities ........................................................................................................................ 76 Chapter 5: Conclusions and recommendations ........................................................... 81 5.1 Conclusions ......................................................................................................... 81 5.2 Recommendations for future work ...................................................................... 82 References ........................................................................................................................... 84 Appendices .......................................................................................................................... 95 Appendix A: Calibration curves ................................................................... 95 Appendix B: Results summary of digesters fed with leachate ..................... 97 Appendix C: ANOVA Analyses .................................................................. 98 Appendix D: Heavy metals in substrates ................................................... 114  vi  List of Tables Table 2.1  Summary of typical results of anaerobic co-digestion ...................................... 26  Table 3.1  Experimental plan for acclimation and anaerobic single and codigestion stages ................................................................................................ 42  Table 3.2  Characterization of samples and frequency of analysisª ................................... 45  Table 4.1  Characterizations of raw municipal and industrial waste streams studiedª .............................................................................................................. 48  Table 4.2  Characterizations of diluted waste streams as digester feedª ............................ 50  Table 4.3  Steady state results for acclimation semi-continuous digestersª ....................... 52  Table 4.4  Inocula characteristics before and after acclimation ......................................... 52  Table 4.5  Results for semi-continuous digesters at 20 d SRT during steady state* ................................................................................................................. 58  Table 4.6  Results for semi-continuous digesters at 10 d SRT during steady state* ................................................................................................................. 59  Table 4.7  Characterization of industrial TWAS on sampling date and after 3 week of storage in fridge................................................................................... 65  Table 4.8  Biogas composition of single and co-digesters during steady state ................... 66  Table 4.9  Relationship between theoretical and experimental CO2 content (%) in digester headspace ........................................................................................ 67  Table 4.10 Comparison between theoretical total ammonia toxicity limit with measured total ammonia concentrations ........................................................... 69 Table 4.11 Summary of different substrates and digestion techniques with their total fecal MB-poster-AD-2013-May 22-CEcoliform presence ....................... 74 Table 4.12 Approximate cost functions for solid waste treatment facilities: single and co-digestion reactors. Based on Tsilemou and Panagiotakopoulus, (2006) ............................................................................... 79 vii  Table B.1  Results for semi-continuous digesters at 20d SRT ........................................... 97  Table C.1.1 TS% removal ANOVA analyses results for temperature and sludge retention time .................................................................................................... 98 Table C.1.2 ANOVA: two-factor with replication TS% removal results for temperature and sludge retention time .............................................................. 98 Table C.1.3 ANOVA analysis TS% removal results for temperature and sludge retention time .................................................................................................... 99 Table C.1.4 TS% removal ANOVA analyses results for sludge retention time and temperature ................................................................................................. 99 Table C.1.5 ANOVA: two-factor with replication TS% removal results for sludge retention time and temperature .............................................................. 99 Table C.1.6 ANOVA analysis removal results for sludge retention time and temperature ..................................................................................................... 100 Table C.1.7 TS% removal ANOVA analyses results for single to co-digestion, and sludge retention time ................................................................................ 100 Table C.1.8 ANOVA: two-factor with replication TS% removal results for single to co-digestion, and sludge retention time ...................................................... 100 Table C.1.9 ANOVA analysis removal results for single to co-digestion, and sludge retention time ....................................................................................... 101 Table C.2.1 VS% removal ANOVA analyses results for temperature and sludge retention time .................................................................................................. 102 Table C.2.2 ANOVA: two-factor with replication VS% removal results for temperature and sludge retention time ............................................................ 102 Table C.2.3 ANOVA analysis VS% removal results for temperature and sludge retention time .................................................................................................. 103 Table C.2.4 VS% removal ANOVA analyses results for sludge retention time and temperature ............................................................................................... 103 viii  Table C.2.5 ANOVA: two-factor with replication VS% removal results for sludge retention time and temperature ............................................................ 103 Table C.2.6 ANOVA analysis removal results for sludge retention time and temperature ..................................................................................................... 104 Table C.2.7 VS% removal ANOVA analyses results for single to co-digestion, and sludge retention time ................................................................................ 104 Table C.2.8 ANOVA: two-factor with replication VS% removal results for single to co-digestion, and sludge retention time............................................ 104 Table C.2.9 ANOVA analysis removal results for single to co-digestion, and sludge retention time ...................................................................................... 105 Table C.3.1 TCOD% removal ANOVA analyses results for temperature and sludge retention time ....................................................................................... 106 Table C.3.2 ANOVA: two-factor with replication TCOD% removal results for temperature and sludge retention time ............................................................ 106 Table C.3.3 ANOVA analysis TCOD% removal results for temperature and sludge retention time ....................................................................................... 107 Table C.3.4 TCOD% removal ANOVA analyses results for sludge retention time and temperature ............................................................................................... 107 Table C.3.5 ANOVA: two-factor with replication TCOD% removal results for sludge retention time and temperature ............................................................ 107 Table C.3.6 ANOVA analysis removal results for sludge retention time and temperature ..................................................................................................... 108 Table C.3.7 TCOD% removal ANOVA analyses results for single to codigestion, and sludge retention time ............................................................... 108 Table C.3.8 ANOVA: two-factor with replication TCOD% removal results for single to co-digestion, and sludge retention time............................................ 108  ix  Table C.3.9 ANOVA analysis removal results for single to co-digestion, and sludge retention time ....................................................................................... 109 Table C.4.1 CH4% ANOVA analyses results for temperature and sludge retention time .................................................................................................. 110 Table C.4.2 ANOVA: two-factor with replication CH4% results for temperature and sludge retention time ................................................................................ 110 Table C.4.3 ANOVA analysis CH4% results for temperature and sludge retention time ................................................................................................................. 111 Table C.4.4 CH4% ANOVA analyses results for sludge retention time and temperature ..................................................................................................... 111 Table C.4.5 ANOVA: two-factor with replication CH4% results for sludge retention time and temperature ....................................................................... 111 Table C.4.6 ANOVA analysis removal results for sludge retention time and temperature ..................................................................................................... 112 Table C.4.7 CH4% ANOVA analyses results for single to co-digestion, and sludge retention time ....................................................................................... 112 Table C.4.8 ANOVA: two-factor with replication CH4% results for single to codigestion, and sludge retention time ............................................................... 112 Table C.4.9 ANOVA analysis removal results for single to co-digestion, and sludge retention time ....................................................................................... 113 Table D.1 Comparison of OMRR heavy metals criteria with calculated concentration for single and co-digested thermophilic effluents at 10d SRT .............................................................................................................. 114 Table D.2 Comparison of OMRR heavy metals criteria with calculated concentration for single and co-digested mesophilic effluents at 10-d SRT ................................................................................................................. 116  x  List of Figures Figure 1.1 Waste streams of the present study case and their respective treatment plant source (SC: screen cake; TWAS: thickened waste activated sludge) ................. 2 Figure 1.2 Anaerobic digestion schema process ................................................................... 3 Figure 1.3 Glenmore Landfill proposed scenario.................................................................. 5 Figure 2.1 Fruit juice line production (UF: ultra-filtration). Based on Sanchez et al. (2009); Fellows and Dillon (1995); ..................................................................... 9 Figure 2.2 Typical biological wastewater treatment plant flow diagram. Adapted from: Droste (1997), Davis and Cornwell (2008), and Tchonobaglous et al. (2004) ................................................................................................................ 11 Figure 2.3 Main processes for anaerobic digestion of sludge, ending in methane production (adapted from Droste, 1997) ........................................................... 16 Figure 2.4 Hydrolysis of the different biopolymers presents in organic matter (adapted from Droste, 1997) ............................................................................. 17 Figure 2.5 Acidogenesis general chemical reactions (adapted from Droste, 1997) ........... 18 Figure 2.6 Different reactions involved during acetogenesis phase (adapted from Droste, 1997) ..................................................................................................... 19 Figure 2.7 Methanogenesis main chemical reactions (adapted from Droste, 1997) .......... 20 Figure 3.1 Kelowna Water Pollution Prevention Center process flow diagram (DAF: dissolved air flotation) ....................................................................................... 33 Figure 3.2 Brandt’s Creek Tradewaste Treatment Plant process diagram (MLSS: Mixed liquor suspended solids)......................................................................... 37 Figure 3.3 Glenmore Landfill process flow ....................................................................... 39 Figure 4.1 Daily biogas productions (@STP) of anaerobic digesters fed with diluted sewage sludge cake (1), Thickened waste activated sludge (2), 1+2+L xi  (leachate), and 1+2+SC+L (screen cake). A) Mesophilic digesters, B) Thermophilic digesters ...................................................................................... 55 Figure 4.2 Specific daily biogas productions (@STP) of anaerobic digesters fed with diluted sewage sludge cake (1), Thickened waste activated sludge (2), 1+2+L (leachate), and 1+2+SC+L (screen cake). A) Mesophilic digesters, B) Thermophilic digesters ................................................................................. 56 Figure 4.3 A) Total solids removal efficiencies at sludge retention times (SRTs) of 20 and 10 days. B) Comparison of TS removal between 20d SRT mesophilic digesters (data represent the arithmetic mean of duplicates and error bars represent standard deviations, SRT: sludge retention time, TS: total solids) ... 61 Figure 4.4 A) Volatile solids removal efficiencies at sludge retention times (SRTs) of 20 and 10 days. B) Comparison of VS removal between 20d SRT mesophilic digesters (data represent the arithmetic mean of duplicates and error bars represent standard deviations SRT: sludge retention time, VS: volatile solids) ................................................................................................... 62 Figure 4.5 A) Total chemical oxygen demand removal efficiencies at sludge retention times (SRTs) of 20 and 10 days. B) Comparison of TCOD removal between 20d SRT mesophilic digesters (data represent the arithmetic mean of duplicates and error bars represent standard deviations SRT: sludge retention time, TCOD: total chemical oxygen demand) ................................... 64 Figure 4.6 Dewaterability analysis results of single and co-digested samples (data represent the mean and error bars represent the standard deviation of 9 replicates, SRT: sludge retention time, TS: total solids) ................................... 72 Figure 4.7 SCOD analysis results of single and co-digested samples (data represent the mean and error bars represent the standard deviation of 74 and 38 replicates for 20 and 10 days SRT, respectively, SRT: sludge retention time, SCOD: soluble chemical oxygen demand) .............................................. 72  xii  Figure 4.8 Coliform content of effluents from anaerobic digesters, at 20 d and 10 d SRT with Class A limit regulation (data represent the mean and error bars represent the standard deviation of 8 replicates, SRT: sludge retention time, MPN: most probable number, TS: total solids) ....................................... 76 Figure 4.9 A) Initial and B) operating cost functions of anaerobic digestion facilities (adapted from Tsilemou and Panagiotakopoulus, 2006) ................................... 77 Figure A.1 Calibration curve for biogas measurement via manometer (STP) .................... 95 Figure A.2 Calibration curve for COD determination ........................................................ 95 Figure A.3 Calibration curve for ammonia (NH3-N) determination ................................... 96 Figure A.4 Calibration curve for total nitrogen (TN) determination ................................... 96  xiii  List of Illustrations Illustration 3.1 Sewage sludge cake before and after dilution ............................................. 35 Illustration 3.2 A)Screen cake obtained from the Salsnes screen. B) Thickened waste activated sludge obtained from the top of the dissolved air flotation tank at the Brandts Creek Tradewaste Treatment Plant .............. 38 Illustration 3.3 A) Eight semi-continuous digesters (four thermophilic and four mesophilic). B) Digester configuration 1: Effluent port, 2: Biogas exit, 3: Influent port, and 4: tedlar bag ....................................................... 43  xiv  List of Symbols and Abbreviations BCTTP Brandt’s Creek Tradewaste Treatment Plant COD Chemical oxygen demand CST Capillary suction time DAF  Dissolved air flotation  L Leachate M Mesophilic MLSS Mixed liquor suspended solids OMRR Organic Matter Recycling Regulation OLR Organic loading rate SC Screen cake SRT Sludge retention time T Thermophilic TS Total solids TWAS Thickened waste activated sludge UASB Upflow anaerobic sludge blanket VFA Volatile fatty acids VS Volatile solids WWTP Wastewater treatment plant  xv  Acknowledgements  I would like to express my sincere gratitude to my supervisor, and my friend, Dr. Cigdem Eskicioglu. Without her guidance and encouragement, the completion of this degree would not have been possible. I have been touched by her kindness as she guided me through my academic journey, as well as many everyday life experiences. The amazing staff and faculty at UBCO made my academic life experience full of special memories. I am deeply indebted to Ms. Teija Wakeman, Ms. Karen Seddon, Dr. Steven O’Leary, Dr. Richard Klukas, Dr. Solomon Tesfamariam and Dr. Kasun Hewage. You surely made my academic experience unforgettable. Moreover, I am thankful to my research group, especially to those with whom I spent most of my time: Hanna Hamid, Kafi Wahidunnabi, Piero Galvagno, and Tim Abbot. My fellow schoolmates and friends for life: Jessica Buriticá, Arnaud Houriet, Weronika Michalska, Haibo Feng, Renee Leboe (and family), Courtney Dean, Karen Robles, and Atul Porwal. Thank you for your continuous help, love, and encouragement I cannot finish without thanking Fabricio Bianchini, the person who changed my life forever. You came along and filled my world with love and dreams. This chapter of my life would not be the same without you. Friends are the family that you choose: Shani Bishop, Molly, Matt and Angus Thurston you truly are my family. Your love and kindness made my stay in Canada extraordinary. My friends from Costa Rica: Maureen and Kattia. Your constant care and love from far away has a special place in my heart. My infinitive gratitude goes to my family, specially my mom, my grandparents and Aunty Yen. You are my everyday source of inspiration that helps me reach my greatest dreams. You are my world, my happiness, and my life. Lastly, I would not have made this far without God being the head of my life. Thank you God for all these blessings.  xvi  Dedication  To my parents Quintín, Ana & Denise  xvii  Chapter 1: Introduction 1.1  Background and motivation  Fruit harvesting is one of the most important agricultural activities in the Okanagan Valley. Within the City of Kelowna, 22,095 acres of land is zoned for agricultural land use (Planning and Development Services, 1998). As the City of Kelowna population grows, food and juice businesses are rapidly expanding to meet the increasing demand. Juice production generates a relatively low volume of wastewater compared to domestic wastewater but has high organic content (El-Kamah et al., 2010). Fruit juice production residues consist of bagasse, marc and lees from decanting steps (Devesa-Rey et al., 2011). The mixed waste stream is characterized by low pH and high macronutrient (i.e., sugars, cellulose) concentration (Point, 2008). In addition to fruit juice industrial wastewater, municipal wastewater also needs to be treated according to provincial and federal regulations before it is discharged to surface water (i.e., lake or river). Brandt’s Creek Tradewaste Treatment Plant (BCTTP) was built to process the wastewater coming from the local fruit juice industry. The three major effluents from treatment site are: screen cake (SC), thickened waste activated sludge (TWAS), and treated wastewater; which is discharged to the domestic wastewater treatment plant (WWTP) for further treatment. Sewage treatment generally is subject to local, provincial and federal regulations and standards. The City of Kelowna, with a population of 150,000, operates a WWTP, called Kelowna Water Pollution Control Center, that daily produces high volumes of dewatered sewage sludge cake (60,000 L/d, with 17.5% total solids), also called “biosolids” after stabilization via composting. Due to the large production of biosolids, environmental policies encourage the practice of biosolids disposal via addition to soil as final disposal (Furlong et al., 2010). Figure 1.1 shows the different treatment sites and the waste streams (substrates) coming from these sites, studied in this research.  1  The City of Kelowna  Kelowna Water Pollution Control Center  Sewage sludge cake  Brandt's Creek Tradewaste Treatment Plant  Fruit juice TWAS  Fruit juice SC  Glenmore Landfill  Leachate  Figure 1.1 Waste streams of the present study case and their respective treatment plant source (SC: screen cake; TWAS: thickened waste activated sludge)  Current disposal of waste sludge (from municipal and fruit juice wastewater treatment) is via composting at the Regional Compost Facility in Vernon, BC. Composting can have a large number of adverse impacts. Composting can pollute the local environment and cause an uncontrolled release of methane that is generated by the decay of organic waste (Ni et al., 1993). Leaching is an important factor of nutrient losses from compost. For instance, it is estimated that 20 to 40% of the loss of the nitrogen (N) and 42 to 62% of loss of carbon (C) present in the waste occurs during composting (Tiquia et al., 2002). If the run-off from the composting facility is not controlled, the organometallic compounds present in the compost leachate have been shown to affect the groundwater. The water run-off from Glenmore Landfill is controlled at the Kelowna Water Pollution Control Center. Anaerobic systems can be used as part of the process to treat bio-waste and sewage sludge. Anaerobic digestion is an enclosed waste treatment system, reducing biogas emissions into the atmosphere. Figure 1.2 shows anaerobic digestion life cycle: from organic waste to biogas production, water recycling in the system, and the utilization of digestate as 2  fertilizer. It has been shown that the biogas can be generated at a much faster rate in engineered bioreactor systems. Biogas production can be converted into reusable energy either for heating or electricity generation. The digester remaining content (digestate) will have a reduced organic strength and will be less odorous (Moody et al., 2009). Digestate comes from acidogenesis and methanogenesis of anaerobic digestion. From acidogenesis, digestate could contain lignin and cellulose. From methanogesis phase, digestate would be high in nutrient content, i.e., nitrates and phosphates (Evans et al., 2009). Moreover, digestate will have a higher nutrient content than undigested solids, which makes it particularly desirable for use as fertilizer or soil amendment.  Figure 1.2  Anaerobic digestion schema process  The Regional Compost Facility is approaching its maximum capacity. Expanding the different facilities could be an easy way to fix this problem. However, the City of Kelowna is trying to reach a goal of becoming carbon neutral by the year of 2020. Therefore, the purpose of this research was to find a sustainable disposal method that combines all organic waste streams coming from the facilities operated by the City of Kelowna in a potential anaerobic co-digestion system.  3  There is plenty of information about aerobic and anaerobic reactor systems for treating wastewater generated from WWTPs of juice, brewery and distillery industries (Ozbas et al., 2006; Ahn et al., 2001; El-Kamah et al., 2010). Studies of anaerobic co-digestion systems are limited, especially for waste sludge and other organic residues from juice production with municipal waste. Recent studies indicate that co-digestion (simultaneous digestion of a mixture of substrates) improves both the biogas yield, and stability of a digester. Positive synergistic effects are mainly due to supply of missing nutrients by different substrates to anaerobic co-digester (Ni et al., 1993). Anaerobic co-digestion has a lower cost to benefit ratio compared to the single digestion (Ozbas et al., 2006). Sharing equipment and utilizing free volume capabilities in existing digesters are the main reason for a lower cost to benefit scenario. Moreover, co-digestion achieves balancing nutrient content. Since both of the organic residues from juice production (i.e. SC and TWAS) are high in carbohydrate (carbon) content, both substrates would be good candidates for co-digestion with other substrates having much lower carbon to nitrogen (C:N) ratios, such as domestic (municipal) sewage sludge. The main motivation for this research was to reduce the environmental impact due to the disposal of waste solids by combining domestic and industrial wastewater by-products to produce methane. Compared to the single-substrate traditional methods (anaerobic single digestion), the combination of different sources of waste would not negatively impact methane production. Moreover, the combination of domestic and industrial waste solids increases the methane production capacity, which can be used as a source of renewable energy. Hence, this approach to sludge treatment process has potentially positive impacts. A prospective place to build an anaerobic co-digester is at the Glenmore Landfill, located in Kelowna, BC, due to reasons explained in Chapter 3 in detail. Figure 1.3 shows a proposed scenario for the Glenmore Landfill incorporating an anaerobic co-digester that uses the excess landfill leachate as dilution water for the dewatered sludge cake, and connects the biogas generated from the co-digester to the biogas utilization system already on-site. This landfill produces leachate, part of which is currently re-circulated in Phase 1 of the site to enhance the generation of methane-rich landfill gas. Currently, the landfill gas is either flared or converted to electricity, enough to power 70 homes (City of Kelowna, 2013). 4  Excess leachate is currently being pumped to the Kelowna WWTP. This excess of leachate could be used as a source of dilution water and alkalinity for the future anaerobic codigester.  Figure 1.3 Glenmore Landfill proposed scenario  With the background information presented, the scope of this project was to assess the single, as well as co-digestion potential of four organic waste streams (fruit juice SC, fruit juice wastewater TWAS, sewage sludge cake and landfill leachate) in laboratory-scale anaerobic digesters operated for 7 months. Analysis of centrifuge system of digestate material for soil amendment preparation and phosphorous recovery (shown in Figure 1.3) were not part of this study.  1.2  Objectives  The main objective of this project was to evaluate the potential yield of an anaerobic codigester utilizing four waste streams coming from the municipal and industrial (fruit juice) WWTPs in the City of Kelowna. In addition, the effect of the C:N present in co-digestion 5  was also investigated. Laboratory-scale mesophilic and thermophilic single and cosubstrate anaerobic digesters were operated at sludge retention times of 20 and 10 days to assess the specific performance criteria listed below: Specific biogas (methane) yield, digestibility, and co-digestibility of each waste Organic removal efficiencies Volatile fatty acids accumulation and ammonia inhibition Coliform content of digested biosolids (digestate) and dewaterability to assess fertilizer reuse Upon completion of laboratory work, the data obtained were used to determine the organic loading rate, retention time and reactor volume requirement values that would later be used in the design of an anaerobic co-digester.  1.3  Thesis organization  This thesis has been organized into five chapters. In the first chapter, the background and motivation of this study case are provided. Objectives of the research are also presented in Chapter 1. The second chapter provides a summary of relevant literature, including WWTPs treating raw sewage and fruit juice wastewater, sludge features, and anaerobic codigestion. In Chapter 3, the materials and methods for this research are documented, including a description of each substrate, and equipment and instrumentation used. Characterization methods and experimental procedures are described in Chapter 3 as well. Chapter 4 presents the results and discussion of the experimentation. The experimental summary data from the lab-scale digesters are presented and compared with literature results. Lastly, Chapter 5 concludes the thesis by compiling a summary of the results obtained in this study and presents recommendations for future work.  6  Chapter 2: Literature review 2.1  Fruit juice industry in the Okanagan Valley  In the Okanagan Valley, many different types of fruits such as grapes, apples, cherries and pears are produced. A growing agricultural sector in the Okanagan Valley has allowed juice and wine production companies to become established in the area. One of the largest fruit juice processors in Western Canada is located in the Okanagan Valley. Fruit juice production generates industrial wastewater that needs to be treated, generally on-site, prior to being discharged to the municipal wastewater collection and treatment system. Understanding the fruit juice production line can provide context to characterization of fruit juice residues. Fruit-juice process begins after fruit harvest and finishes in the storage and transport of the fruit juice. A typical fruit juice production line is shown in Figure 2.1 as a process diagram. Fruit harvest is the first step of the process flow. After the fruit is collected, it is transported to an industrial plant. The fruit juice process begins once all of the fruit is received at the process plant. This stage consists of several phases. The first phase for factory procurement is inspection. All good fruit is separated for quality control. Fruits with good color and size are selected, while fruits with bruising and/or mold are discarded. The next stage is fruit sorting. Contaminants and substandard fruit are removed in this stage. The following step is washing and preparation. The rinse water for washing apples is collected, and it is connected to the wastewater effluent system. Depending on the final product, slicing and pre-filtering is also required (Food and Organization of the United Nations, 2001). The second phase consists of grinding and mashing the fruit. More rinse water is used as well as some enzymes. Enzymes added to fruit juice are necessary for pressing. These enzymes will increase the breakdown of cellulose, making an efficient pressing system (Ribeiro et al., 2010; Food and Organization of the United Nations, 2001). Whole fruits are milled and treated with enzymes prior to pressing to loosen cell walls and promote the free running of the juice. After pressing, the juice is transferred to clarification tanks where an additional enzyme is added to the juice to depectinize and hydrolyze starch prior to 7  filtration. Enzymes added are inactivated during pasteurization of the juice (Ribeiro et al., 2010). The majority of the liquid coming from fruit pressing is used for the juice-batch preparation. The leftover pulp is sent to a centrifuge. The centrifuge is used to extract more juice from the pulp and the rest of the fruit (Fellows and Dillon, 1995). The centrifuge and pressing stages produce two effluent streams: raw leachate and raw juice (waste effluent). Later on the process, raw leachate will be connected with the main waste stream system. The third phase is the batch preparation. By rotary screenings, this phase involves mixing the fruit juice with the additives. Additives will vary depending on the final product. The batch preparation produces another waste stream. After the additives addition, the line production is divided into two. One line is connected to the refining system. The second line from additives-batch preparation is connected to ultra-filtration. After these processes are completed, the filtered liquid from both processes (ultra-filtration and refining system) are combined in the pasteurization batch. Pasteurization is a mandatory process specified by Canadian Food Inspection Agency regulations (Canadian Food Inspection Agency, 2012). Each procedure (ultra-filtration and pasteurization) produces waste that contains a high amount of solids. Waste residues coming from ultra-filtration are highly contained with macronutrients such as cellulose and lignin. From pasteurization procedures, the proteins are expected to be present in the waste stream (Ribeiro et al., 2010). The final phases of the procedure are the aseptic filling of the juice into the proper containers and storage of the final product (Sanchez et al., 2009).  8  Figure 2.1 Fruit juice line production (UF: ultra-filtration). Based on Sanchez et al. (2009); Fellows and Dillon (1995); and Food and Organization of the United Nations (2001)  9  Approximately 70% of fruit juice industry raw materials are fruit. The other 30% of raw materials are water, enzymes, sugar, and specific chemical toppings. Therefore, the juice production generates waste streams with high organic concentration. Wastewater that comes from fruit juice industries has high concentrations of sugars and carbohydrates, among other organic compounds. Due to the presence of a high organic content in the wastewater, a biological treatment process in the WWTP is preferred.  2.2 2.2.1  Treatment processes for wastewaters Treatment processes for fruit juice wastewaters  A biological treatment is preferred if the influent wastewater composition has biodegradable pollutants such as sugars, proteins, yeast, filter-aid, and soluble starch. US Environmental Protection Agency (EPA) and Canadian Department of the Environment declare that organic wastewater effluents need to be treated under physical or biological systems (U.S. Environmental Protection Agency, 2004; Environment Canada, 2010). For fruit juice biological wastewater treatment, processes are based on the microorganisms’ metabolic activity. Biological metabolisms occur in the secondary phase of the WWTP, following preliminary (screening, equalization) and primary treatment (primary sedimentation). In addition to pollutants listed above (section 2.1), wastewaters produced from fruit juice production consist of the following: wastewater from cleaning containers, rinsing and washing water, exhaust vapor condensate, wastewater from production facilities, wastewater from surface cleaning and from cleaning conveyor facilities (Rosenwinkel et al., 2005). Different biological treatment processes can be used to achieve a higher removal of biological oxygen demand. These treatments can be applied directly or can be combined with each other. Figure 2.2 shows a typical fruit juice industry WWTP system.  10  Figure 2.2  Typical biological wastewater treatment plant flow diagram. Adapted from:  Droste (1997), Davis and Cornwell (2008), and Tchonobaglous et al. (2004)  In addition to high organic strength, another challenge with treating this industrial stream is high fluctuations. Naturally, fruit juice production waste changes depending on the process and products that are being used (Trnovec and Britz, 1998). Furthermore, significant variations in daily/weekly/seasonally effluent discharge load and concentration in biological or chemical oxygen demand (COD) are typical as well (Ozbas et al., 2006). All these pollutants are capable of disrupting the ecological equilibrium in water bodies causing eutrophication and increasing turbidity (Droste, 1997). Moreover, the growing concern over the quality of water enforced a higher pollution reduction on treatment facilities. Therefore, biological treatment is preferred as the most optimal solution for treating wastewaters and solid by-products coming from fruit juice factories (Koevoets et al., 2002; Trnovec and Britz, 1998). The use of product and product additives (like sugar which is often added) contributes to a significant amount of the wastewater pollution from the fruit juice industry. The COD of fruit juices ranges from about 50 g/L (tomato juice) to about 200 g/L (apricot juice). Moreover, 1 kg of glucose (or of fructose) is equivalent to 1066 g COD. Besides the wastewater, the fruit juice industry also produces cooler sludge, filtration residues, sludge from clarifying agents, and pomace (Rosenwinkel et al., 2005). In order to meet the discharge limits of the municipal sewer system, it is often necessary to equalize the pH peaks and sometimes to reduce the temperature. Requirements of treated 11  wastewater disposal in terms of pH and temperature are 6.5-9, and 15oC, respectively (Ministry of Environment, 2012). Thus, a fruit juice wastewater pretreatment plant starts with a neutralization stage. Because of the high cost of chemicals, biological neutralization is usually recommended (e.g., in an aerated mixing and equalizing tank). Equalization tanks can achieve biological oxygen demand elimination between approximately 35% in daily basis, and greater than 50% weekly equalization basis (Rosenwinkel et al., 2005). Furthermore, equalization tanks overcome the operational problems, and flow rate variations, to improve the processes and to reduce the size and cost of downstream facilities. Aerobic and anaerobic biological processes are used worldwide to treat sewage and wastewater coming from fruit juice industry. To achieve a good performance, use of biota is necessary (Kadam et al., 2008). Microorganisms like eukaryota and protozoa are mostly used to consume all of the organic matter present in the wastewater (U.S. EPA: Primer for Municipal Wastewater Treatment Systems). Ideally, biota requires a minimum specific ratio of nutrients of 20:1 (C:N) to achieve full removal of COD in a biological treatment system (Grady et al., 1999). The main role of the microorganisms is to transform the dissolved and particulate biodegradable matter into acceptable end-products by capturing and incorporating suspended and non-settleable colloidal solids into the biological floc (biosolids). Additionally, these microorganisms transform and remove nutrients by removing specific trace organic constituents and compounds (Tchobanoglous et al., 2004). According to Rosenwinkel et al. (2005), for direct discharge into waterways, the activated sludge system with cascade design has proved to be viable for the fruit juice industry. Cascade sludge system was operated at sludge loads of greater than 0.1 kg biochemical oxygen demand / mixed liquor suspended solids (MLSS) kg × day. Due to low nitrogen and phosphorous amounts in the raw wastewater, it was necessary to add nutrients. In general, fruit juice industrial wastewaters have such low nitrogen and phosphorous concentrations that it is often necessary to add urea and phosphoric acid as a nutrient supplement. The nutrient addition helps to achieve the minimum nutrient ratio for growth of the microorganisms that are required for the biodegradation of waste (Rosenwinkel et al., 2005; Ozbas et al., 2006). 12  Another alternative treatment system is the upflow anaerobic sludge blanket reactor (UASB). Upflow systems are high-rate anaerobic reactors developed and successfully applied in recent years for the biological treatment of effluents, and in particular those from the food processing industries (Lettinga et al., 1997). An example of UASB is the Biothane® UASB/ Biobed® expended granular sludge bed anaerobic pre-treatment process in combination with an Aerothane Flash-Aeration purification (Rosenwinkel et al., 2005). This biological treatment achieved 70 – 90% COD removal from fruit juice effluents. Tawfik and El-Kamah (2011) studied the performance of anaerobic hybrid reactor followed by sequencing batch reactors in order to treat fruit juice industry wastewater. The anaerobic hybrid reactor achieved up to 42% COD removal, and 56% total suspended solids removal. The sequencing batch reactors achieved up to 67% COD reduction.  2.2.2  Treatment processes for raw sewage  Similar to industrial wastewater treatment, the municipal wastewater (sewage) treatment is also subject to local, state and federal regulations and standards. The process for removing pollutants in municipal wastewater has physical, chemical, and biological stages. Preliminary (physical) treatments are screening and grit removal. Screenings are used to retain solids found in the raw sewage. Moreover, grit removal is another preliminary treatment and aims to remove grit, sand, gravel, sanders, or heavy materials (Droste, 1997). The following stage is sedimentation (primary) stage. In this stage, the wastewater is held in static basin, called primary setting tank, which allows solids to settle to the bottom while the oil, grease, and lighter solids remain floating. The secondary stage removes dissolved and suspended biological matter that is typically performed by indigenous, water-borne microorganisms in a managed habitat. Tertiary treatment, a phase in addition to primary and secondary treatment, allows for disposal into a highly sensitive ecosystem (Kadam et al., 2008). Primary settling tanks are usually equipped with mechanically driven scrapers. Mechanical systems drive the collected sludge towards a hopper in the base of the tank where it is pumped to sludge treatment facilities (Tchobanoglous et al., 2004). Microorganisms are the 13  biological engines to minimize the organic matter in activated sludge processes. A variety of microorganisms helps to convert colloidal and dissolved carbonaceous organic matter into various gasses as well into protoplasm (Droste, 1997). This stage is designed to be effective in reducing the amount of biodegradable soluble organic contaminants present (i.e. sugars, fats, organic short-chain carbon molecules). Biosolids (stabilized waste sludge) are the largest by-product resulting from wastewater treatment processes. Biosolids production amount and total solids (TS) concentrations may vary based on the treatment used, source of the wastewaters, and the method of dewatering (if used). As an example: domestic biosolids generated from two-phase centrifugation system, in Castilla, La Mancha (Spain) has approximately 17.9% TS (Fernandez et al., 2010). Annual productions may vary according to the city population and WWTP capacity. Another example is, the Annacis Island WWTP (Greater Vancouver Regional District), with a population of 1,000,000, is producing 39,000 tonnes/year dehydrated (30%) waste sludge (Metro Vancouver, 2008). Because of the large production volumes of biosolids, environmental policies, such as BC Ministry of Environment Organic Matter Recycling Regulation (OMRR), encourage the practice of biosolids disposal via addition to soil. However, disposal policies for soil and water conservation have not been well implemented in many countries. The City of Kelowna relies on biological treatment as an integral part of its municipal wastewater treatment system. Excess solids residuals (or biosolids) are produced as part of the primary and secondary treatment. Currently, the biosolids are dewatered and hauled to the Kelowna-Vernon District Compost Facility.  2.3  Landfill sites  A landfill is a disposal site for solid waste materials, i.e. household waste, construction/demolition waste, waste from streets. Landfills are based on several sprayedon layers of wastes and biosolids, which are blankets. Generally, these layers of waste are covered with soil layers. This cure site confines, compacts and covers the waste (Borongan and Okumura, 2010). This waste disposal method has many negative impacts, some of 14  which include the release of odour and gasses, the production of leachate, bacteria and fungi growth, and the potential to convey heavy metals to the soil (Aggelides and Londra, 2000). A major waste stream coming from Glenmore landfill operation in the Okanagan Valley is the leachate. Currently, part of the leachate is being re-circulated to provide moisture to the solid waste pile through the landfill gas collector pipes. The remaining leachate is pumped to the Kelowna WWTP. The future goal is to recirculate 100% of the leachate in the Glenmore Landfill, avoiding the pumping of leachate off-site to the WWTP. This procedure enhances decomposition, creating more methane for electrical generation and more space for future landfilling. The Glenmore Landfill is currently operating according to a plan called the Landfill Gas Management Program. This program aims to collect the methane gas produced by the landfill to run three microturbines to generate electricity (Glenmore Landfill: City of Kelowna, 2012). All regulated landfills are required to design and install a gas collection system from the landfill site. In addition, Ministry of Environment under Landfill Gas Management Facilities Design Guidelines, declares that all landfill gas captured must undergo into reduction, whether by flaring, gas utilization for electricity generation, fuel, etc. (Conestoga-Rovers, 2010). The population growth in the Okanagan Valley may necessitate future upgrades at the Glenmore landfill. The alternatives to these upgrades are waste reduction, recycling/reusing strategies, or aerobic or anaerobic biological treatment of organic waste streams currently being sent to the landfill, such as organic portion of kitchen waste. Anaerobic digestion can be a good candidate for biogas generation from the waste streams with high organic strength, such kitchen waste and municipal and industrial waste sludge. This treatment can be applied after a sorting process in order to remove the unwanted materials (Fruteau de Laclos et al., 2008).  2.4  Anaerobic digestion as proposed treatment  Anaerobic digestion processes are used for turning high-strength organic waste, such as manure, food scraps, sewage and industrial treatment sludge (biosolids), into usable energy 15  in the form of biogas (methane and carbon dioxide). Additional benefits of the process include diverting waste from landfills and reducing pathogens, odour and greenhouse gas emissions. The anaerobic digestion of complex organic waste is composed of four bio-chemical reactions, performed in the following order: hydrolysis, acidogenesis, acetogenesis and methanogenesis. This process is summarized in Figure 2.3. Each process is discussed in the following sub-section.  Figure 2.3 Main processes for anaerobic digestion of sludge, ending in methane production (adapted from Droste, 1997)  16  2.4.1  Hydrolysis phase  The first process in anaerobic digestion is hydrolysis where the complex organic matter is broken down to simpler organics by different communities of microorganisms (Powrie, 2011). These microbial communities will break down the polymeric chains of organic matter by using their extracellular enzymes. The major microbial group for this stage will be hydrolytic fermentative bacteria (Powrie, 2011; Demirel and Scherer, 2008). Hydrolysis will produce sugars, fatty acids, and volatile fatty acids (VFAs), amino acids, and some other organic monomers as shown in Figure 2.4. The rate of hydrolysis stage will determine the whole anaerobic process as it is the slowest process especially for the highly complex waste (Neyes and Baeyens, 2003).  Figure 2.4 Hydrolysis of the different biopolymers presents in organic matter (adapted from Droste, 1997)  17  2.4.2  Acidogenesis  Acidogenic fermentative bacteria will turn the monomers that were broken down in the previous stage, into their respective acids (Figure 2.5). In this stage, VFAs are produced along with ammonia, carbon dioxide, hydrogen sulfide, and other products (Demirel and Scherer, 2008).  Figure 2.5 Acidogenesis general chemical reactions (adapted from Droste, 1997)  The VFAs present in the system will increase the acid concentrations, which can lead to poor sludge degradation performance. Furthermore, acid production will lead to acetogenesis, which is a key part of the anaerobic system. The acetogenesis process will decrease the VFAs concentration, which allows for pH neutralization and keeps the microorganisms alive in the digesters (Grady et al., 1999).  18  2.4.3  Acetogenesis  Acetogenesis is the third stage of sludge digestion. The reaction digests the acid molecules through acetogens. The process will produce acetic acid, carbon dioxide, and hydrogen. The acetogenic bacteria will perform several reactions only in the presence of alcohols and acids monomers (Figure 2.6). Therefore, the acetogens need syntrophic bacteria. Also, acetogens depend on an effective inter-species hydrogen transfer (Demirel and Scherer, 2008). It is expected that, after acetogenesis, there will be minimum of acids in the system. The final step for the digestion of organic matter is methanogenesis.  Figure 2.6 Different reactions involved during acetogenesis phase (adapted from Droste, 1997)  19  2.4.4  Methanogenesis  Methanogenic bacteria are physiologically identified by their methane production capability. Additionally, other substances such as carbon dioxide, water, hydrogen sulfide, and other less complex organic matter are produced. In this process, acetate will be converted into methane while the hydrogen and carbon dioxide are consumed, as presented in Figure 2.7. Many physical-chemical parameters such as pH and nutrients are required to achieve an optimal performance (Grady et al., 1999).  Figure 2.7 Methanogenesis main chemical reactions (adapted from Droste, 1997)  2.5  Control parameters of anaerobic process  Efficient digester performance depends on maintaining healthy bacteria populations. The inactivity of any bacteria population can inhibit the activity of the other groups. The performance and activity of methanogens are particularly important for methane (CH4) production. This is because methanogenic microorganisms are more sensitive to changes in the environmental conditions as discussed below (Demirel and Scherer, 2008).  2.5.1  Physical factors  From process loading to operational factors, there are many factors that affect the performance of anaerobic treatment systems. Sludge retention time (SRT), hydraulic retention time, organic loading rate (OLR), and hydraulic loading rate represent the main process loading factors. Operational factors can be mixing regime (complete-mixed or plug  20  flow) and the characteristics of the substrate. To successfully design and operate an anaerobic treatment system, it is critical that these factors are understood and managed.  2.5.1.1  Temperature  Anaerobic processes strongly depend on temperature. The anaerobic conversion of organic matter has its highest efficiency at a temperature 35-40°C and about 55°C for mesophilic and thermophilic conditions, respectively. However, anaerobic processes can still operate in a temperature range of 20-45°C without major changes in the microbial ecosystem (Cuetos et al., 2011). Enzymatic activity is enhanced at higher temperatures.  2.5.1.2  Hydraulic and solids retention time  Hydraulic retention time and SRT are two other important design parameters in biological treatment processes. Hydraulic retention time indicates the time the waste remains in the reactor in contact with the biomass. The time required to achieve a given degree of treatment depends on the rate of microbial metabolism. Wastes containing simple compounds such as sugar are readily degradable and require low retention times, whereas complex wastes are slowly degradable and need longer hydraulic retention time to be metabolized (Khanal, 2008). SRT, on the other hand, controls the performance of anaerobic processes. SRT represents the time that the biomass (acid and methane forming microorganisms) spends in the reactor. Therefore, maintaining a high SRT produces a more stable operation, better toxic or shock load tolerance, and a quick recovery from toxicity. The permissible organic loading rate in the anaerobic process is also determined by the SRT (Khanal, 2008; Grady et al., 1999). Hydraulic retention time is a deciding factor in process design for complex and slowly degradable organic pollutants. Furthermore, SRT is the controlling design parameter for easily degradable organics. For slow-growing microorganisms such as methanogens, longer SRTs are required to prevent them from being washed out from the reactor. Determination 21  of SRT for an anaerobic system is equal to the hydraulic retention time for simple calculation. Continuous stirred tank reactors without solid separation and recycling are often prone to failure due to excessive biomass washout unless long SRTs are maintained. Elevated hydraulic retention times require a bigger reactor volume (volume = flow rate × hydraulic retention time), which is costly (Khanal, 2008; Grady et al., 1999).  2.5.1.3  Volumetric organic loading rate (OLR)  Anaerobic processes are characterized by volumetric OLRs. This physical parameter is a measure of the biological conversion capacity of the anaerobic digestion system. OLR is particularly important control parameter in a continuous system. Many plants have reported system failure due to overloading. OLR is expressed in kg COD or volatile solids (VS) per m3 of reactor. It is linked with retention time for any particular feedstock and anaerobic reactor volume (Verma, 2002). High-rate anaerobic reactors, such UASBs, are capable of treating wastewater at volumetric OLRs of 10 – 40 kg COD/m3 × day. A high volumetric OLR indicates that more wastewater can be treated per unit of reactor volume (Demirel and Scherer, 2008).  2.5.1.4  Continuous feed  In order to prevent endogenous respiration among the bacteria community, daily feedstock is required. Overfeed can asphyxiate the microorganisms. However, if the microorganisms are not regularly fed, the bacteria will enter the starvation phase. As the rate of incoming food decreased, the energy generation rate decreases as well. No energy present means nonnew growth of microorganisms and thus the net growth yield will decline (Grady et al., 1999). As a result of endogenous metabolism, bacteria will use other bacteria communities present in their enzymatic system to sustain themselves, which will decrease the treatment efficiency of the bioreactor.  22  2.5.1.5  Mixing  An effective mixing system is critical to the successful operation of an anaerobic reactor or digester. Mixing provides four advantages for an optimal methane yield in anaerobic digestion. These advantages are: intimate contact between the microorganisms and their substrate, resistant to mass transfer reduction, minimization of inhibitory reaction intermediate build-up, and stable environmental conditions (Demirel and Scherer, 2008).  2.5.1.6  Characteristics of the substrate  Different substrates with different level of molecular complexity will have different methane yield in an anaerobic reactor system (Lei and Rundong, 2010). The complex substrates with higher molecular weight, such as municipal or industrial biosolids, animal manure, will require long hydrolysis times before methane conversion. Counteraction of inhibitors (such as ammonia or xenophobic compounds) can be achieved by adding certain nutrients or by dilution of the waste.  2.5.2  Chemical factors  It has been pointed out earlier that anaerobic processes are severely affected by changes in environmental conditions. The effect of environmental factors on treatment efficiency is usually evaluated by the methane yield; because, methane forming bacteria are more sensitive to environmental changes than the acid forming bacteria in anaerobic treatment of wastewater/ sludge. The following is a brief summary of several chemical factors.  2.5.2.1  pH  The general optimum pH for anaerobic digesters has been found to vary from 6.8 to 7.2 (Gunnerson and Stuckey, 1986). Digester pH is governed by the interaction of various acids and bases present in the reactor. These compounds can produce buffer systems in the reactor. Insufficient buffer capacity in single stage digesters, where acid and methane 23  formation co-exist, may inhibit methanogenesis as a result of the pH decrease. Under the high OLRs, the decline in pH value and the minimal or zero biogas (methane) produced could probably be explained by the accumulation of VFAs during anaerobic digestion (Monou et al., 2008). In such cases, external buffer addition may be beneficial/necessary to neutralize the VFAs and subsequently lessen the adverse effect on methane formers.  2.5.2.2  Toxicity  The wastewater may contain compounds that are anaerobically difficult to degrade, such as aromatic compounds, ammonia, heavy metals, halogenated compounds, cyanide, sulfide, and some VFAs. Although, some anaerobic microorganisms are also capable of degrading refractory organics that otherwise might be considered toxic (Monou et al., 2008).  2.5.2.3  Nutrients  All microbial-mediated processes require macro-nutrients and some trace elements (micronutrients) during waste stabilization. Nutrients and trace elements are not directly involved in waste stabilization. Nevertheless, they are the essential components of a microbial cell and thus are required for the growth of an existing microbial cell and synthesis of a new cell (Riaño et al., 2011). Nutrients and trace elements also provide a suitable physicochemical condition for optimum growth of microorganisms. It is important to note that if the waste stream in question does not have one or more of the important nutrients and trace elements, the waste degradability can be severely affected. This is because of inability of microbial cell to grow at an optimum rate and to produce new cells (Demirel and Scherer, 2008). The key to balancing the anaerobic digestion process lies in balancing the C:N ratio in the substrate or co-substrate mixture, as well as other macro- and micro-nutrients. Nitrogen requirement is governed mainly by the quantity of cells. The higher the overall cell yield, the higher is the nitrogen requirement. For anaerobic digestion, the C:N ratio should be close to 35:1 (Droste, 1997). The microorganisms require as well, the presence of some 24  micro-nutrients, in order to achieve their synthesis reactions. Some of these micro-nutrients are potassium, calcium, magnesium, sulfur, sodium, chloride, iron, zinc, manganese, copper, among other metals (Grady et al., 1999).  2.6  Anaerobic co-digestion  Application of co-digestion as an intelligent raw material management offers many advantages (Lei and Rudong, 2010). Anaerobic co-digestion is defined as a treatment that combines at least two different types of waste. The primarily goal of co-digestion is to enhance biodegradation and to increase biogas production (Li et al., 2011). Co-digestion also aims to reduce the potential negative effects, such as nutrient/alkalinity deficiency, and toxicity on biogas production. Based on the physical and chemical characteristics of each substrate, anaerobic co-digestion can yield its highest efficiency by making the “perfect” co-substrate. Depending of the wastes, a co-substrate can generate higher buffering capacity, protecting the digestion process from the accumulation of VFAs (Cuetos et al., 2011). Furthermore, co-digestion can allow for higher nitrogen content substrates be codiluted with a higher concentration of COD substrate: achieving an appropriate nutrient content (C:N). In addition, dilution of inhibitors (i.e., ammonia compounds and heavy metals) is achieved. Thus, co-digestion reduces negative effects of specific substrates by adding more of other substrate (Cuetos et al., 2011). Furthermore, co-digestion provides higher efficiency in terms of land and equipment use. Additionally, cost can be shared among the different waste producers (Cuetos et al., 2011; Riaño et al., 2011). Most importantly, as a result of higher degradation efficiency, the co-digestion process will reduce the amount of solid waste (dewatered digestate) that must be disposed of. Industrial and municipal biosolids can be treated in an anaerobic co-digestion system (Bajgain and Kellner, 2005). These processes will minimize industry’s carbon footprint, and minimize solid disposal. Furthermore, the processes increase biogas production. Over the past ten years, anaerobic co-digestion of biosolids with other substrates has been studied mostly at lab-scale. Table 2.1 shows a summary of the results obtained with different substrate combinations. 25  Table 2.1 Summary of typical results of anaerobic co-digestion Author Álvarez et al., 2010  Substrates  Type of digestion  Pig manure  Biochemical  Fish waste  methane potential  Biodiesel waste  assays  Abattoir Bouallagui et al.,  wastewater  2009  Fruit and vegetable waste  % TS removal*  Biogas yield*  Methane yield*  N/A  N/A  86.2  0.85 L/g VSremoved  0.53 L/g VSremoved  51  N/A  4370 m3/d  N/A  0.71 L/g VSadded  0.43 L/g VSadded  N/A  1 L/d  0.22 L/g VSadded  3.4 L CH4/kg TS×d  Lab-scale semicontinuous digesters  Organic fraction Dereli et al., 2010  municipal waste  Full-scale digester  Primary sludge Lei and Rundong, 2010  Cow manure  Biochemical  Bioorganic  methane potential  municipal waste  assays Biochemical  Herbal extraction Li et al., 2011  residues Swine manure  methane potential assays, and lab-scale semicontinuous digesters⌘  26  Author  Substrates  Type of digestion  % TS removal*  Biogas yield*  Methane yield*  72.1  1.56 L/gVS added  0.41 L/g VSadded  Potato processing Monou et al., 2008  wastewater  Biochemical  Pig slurry  methane potential  Abattoir  assays  wastewater *Optimum results (VS: volatile solids, TS: total solids)  27  Studies showed improvements due to addition of agricultural residues as co-substrates in anaerobic treatments (Cuetos et al., 2011). Likewise, Lei and Rundong (2010) showed that co-digestion of cow-manure and a municipal waste mixture had the highest biogas production potential. In other studies, single digestion of agronomy residues presented poor buffering capacity and higher accumulation of VFA through anaerobic digestion. However, co-digestion of potato wastewater and pig slurry (pig waste) presented most efficient process than single cases. For this case, manure had a high buffering capacity, plus a wide range of nutrients needed for methanogens (Monou et al., 2008). Currently there is not enough information available about co-digesting fruit juice and sewage sludge, nor is there sufficient information about the correct nutrient ratio present for each co-substrate studied so far. The closest study was on the co-digestion of winery wastewater and sewage waste activated sludge. This particular research showed an increase of anaerobic biodegradability, confirming that co-digestion neutralized negative effects of some of the substrates (Rodriguez et al., 2007) Overall, anaerobic co-digestion has more advantages than disadvantages. This technology has the benefit of mitigating the presence of toxic compounds by diluting them, and would help to balance the C:N ratios. As an important limitation with the existing literature, the majority of the previous co-digestion results are based on biochemical methane potential assays, which are conducted under batch conditions in very small vessels. These assays are used only for preliminary screening and do not necessary represent the performance of continuously-fed co-digesters used at the full-scale. In addition, not all the previous studies used co-substrate volumetric ratios which were based on production rates of each waste stream. Moreover, C:N:P ratios were not reported all the time for each single and/or codigestion scenarios.  2.7  Biogas as a global renewable energy  Biogas is a mixture of different gases produced from an anaerobic treatment system including digester or co-digester. The biogas composition is mainly methane (40-75%), carbon dioxide (25-55%), hydrogen sulfide (0-3%) and vapor water (0-10%) (Bothi, 2007). 28  Biogas produced from organic waste is a renewable source, therefore, will support both environmental and energy sustainability. In US, the use of biogas production could generate enough electricity to meet up to 3% of all electricity expenditures (Omer, 2008). Furthermore, biogas production/recovery from organic waste in an enclosed digestion system will reduce the greenhouse gas emissions that may be released from the waste if decomposed in an uncontrolled environment, such as a landfill without gas recovery system or composting piles. Also, biogas production does not have any geographical and climate limitations. In terms of the energy equivalency, 1 m3 of biogas will generate approximately 0.57 m3 of methane, which can replace 0.57 L of oil. Similarly, 1 m3 of biogas will generate 2 kWh of electricity (Balat and Balat, 2009; EPA: Inventory of U.S. greenhouse gas emissions and sinks, 2011). Biogas energy could supply domestic needs, and could be used in electrification, irrigation and water supply, among other processes (Bhutto et al., 2011; Omer, 2008). The shift to alternative energy sources still requires much more investment in infrastructure, equipment and research development. Currently, there are six major types of bio-power systems. For anaerobic digestion, the main types are direct-fired, co-firing, gasification, pyrolysis, and modular systems. These bio-power technologies are easy to install in small or modular systems, achieving up to 5 MW of energy (Bhutto et al., 2011). Nevertheless, it is important to emphasize that the presence of other gasses and impurities in the biogas may affect the performance and efficiency of these bio-power systems. Therefore, prior to selection of a bio-power system, it is necessary to analyze the biogas composition, in order to minimize any harmful impact or deterioration of the complete system. Gasses, such as hydrogen sulfide, can be present in the biogas. Hydrogen sulfide (H2S) is generated by sulfate-reducing bacteria in anaerobic digestion. Hydrogen sulfide is colorless, highly toxic and flammable gas at concentration limits of 4.3-46% with an odor of rotten eggs. In most of the cases, if there is presence of hydrogen sulfide in the biogas, biogas cogeneration systems for electricity or heat generation cannot be operated without maintenance problems. Oxidation of this gas in the presence of moisture produces sulfuric acid, a highly corrosive compound (Ahammad et al., 2008). 29  Another major challenge of burning biogas to generate electricity is the presence of siloxanes. Siloxanes are volatile cyclic organic gasses. Generally, they are present in the biogas streams mostly from landfill sites. If siloxanes are fired, their combustion product will be silica deposits. These silica forms would decrease the lifetime of engine and turbines (Clark et al., 2012). The presence of both siloxanes and H2S were the main reasons behind the operational problems experienced for the microturbines used to generate electricity from the Glenmore landfill gas (Kelowna, BC) in the last couple of years. Moreover, some other gasses present in the biogas are part of greenhouse gasses (i.e. carbon dioxide, nitrous oxide, ozone, water vapor, etc.). Therefore, a pretreatment to purity and to clean to the biogas prior to usage is necessary in order to give a longer lifetime and warranty to the equipment. This will also reduce the greenhouse gas emissions from the biogas burning. Intensifying biogas research may lead to better ways to maximize the energy potential from waste; the implementation of which may also lead to significant waste reductions. Either of these would decrease the environmental footprint.  2.8  Summary  Fruit juice industries and domestic households both produce large volumes of waste daily. Waste production is an everyday disposal concern for any city. The combination of already known process, such as anaerobic digestion with co-digestion improves the performance of current disposal methods. Anaerobic co-digestion is an environmentally friendly disposal method that can reduce the overall carbon footprint. In addition, the development of this system would produce enhanced biogas that can be used as renewable energy source for the residents of the City of Kelowna. By combining municipal and industrial wastewater byproducts in anaerobic co-digestion, the environmental impacts from the disposal of waste solids can be significantly reduced, especially when compared to traditional single-source solid waste treatment methods. The previous lab- and full-scale studies indicate that combining different waste streams in an anaerobic digester could increase the methane production capacity to produce renewable 30  energy. However, co-digestion of fruit-juice and municipal waste streams has not been implemented at the lab- or full-scale yet. Therefore, this study aims to assess the biodegradation efficiency of these streams under mesophilic and thermophilic digester conditions at volumetric ratios representing their productions rates at the treatment facilities. The biogas produced in this process could be captured and use as a possible alternative source of energy for the City of Kelowna. If the technology is proven to be feasible, the benefits, for the City of Kelowna, are potentially enormous.  31  Chapter 3: Materials and methods 3.1  Industrial and municipal waste samples  Grab waste samples were collected from two different WWTPs and a landfill site in Kelowna (BC, Canada). Both treatment plants and the landfill site are operated by the City of Kelowna; therefore, co-digestion of these various streams in a single bioreactor (anaerobic digester) were expected to be feasible from waste management point of view. The samples were collected bi-weekly, and their respective characterizations were made the same day of sampling. Upon characterization, the samples were stored in a fridge at 4oC. Four different waste samples used for this study included sewage sludge cake, industrial (fruit-juice) thickened waste activated sludge (TWAS), fruit-juice screen cake (SC), and landfill leachate.  3.1.1  Municipal (sewage) sludge cake  The sewage sludge cake was taken from the municipal WWTP (Kelowna Pollution Prevention Center). By 2010, the City of Kelowna WWTP treated 37 million liters of sewage on a daily basis. In order to meet the population demand, the Kelowna Pollution Prevention Center upgraded its facility’s capacity from 40 to 70 million liters per day. The treatment facility bases its treatment on biological processes, targeting organic fractions of municipal, and pretreated industrial and agricultural streams from the Valley. The overall treatment plant consists of eight stages: 1) screening, 2) grit removal, 3) primary clarifiers and fermenters, 4) bioreactor, 5) secondary clarifier, 7) disc filters, and 8) ultraviolet disinfection (Figure 3.1).  32  Figure 3.1  Kelowna Water Pollution Prevention Center process flow diagram (DAF: dissolved air flotation)  33  The screen and grit removal are used to protect pumps, valves, pipelines from damage or clogging by removing rags and large objects. The following primary sedimentation removes readily settleable solids and floating material under gravitation forces. The settled “primary sludge” is sent to fermenters to generate VFAs. The clear supernatant is passed to the bioreactor for biological C, N and P removal. The bioreactor in Figure 3.1 is a modified Bardenpho® (barnard denitrification phosphate) or “Phoredox” system. Phoredox reactors consist of an anaerobic fermentation zone followed by two stages of anoxic and aerobic complete-mix activated sludge. The hydraulic retention time of the Phoredox system is 9.3 hrs. SRTs are 6 d and 13 d during summer and winter months, respectively. Nitrogen removal is reached by sequential nitrification-denitrification in a single-sludge system: majority of total N is lost through as nitrogen gas (Oldham and Stevens, 1984; Sattayatewa et al., 2009). The removal of phosphorous is achieved by phosphorus accumulating organisms. The VFAs generated in the fermenters are used as a carbon source by the denitrifying bacteria. The excess sludge generated in the bioreactor or “secondary sludge” is settled in the secondary sedimentation tank and thickened via dissolved air flotation (DAF) unit. Finally, fermented primary and thickened secondary sludge streams are mixed at a volumetric ratio of 40:60 and are dewatered to a final solids concentration of 17.5 ± 1% TS by a centrifuge. The centrifuged mixed sludge stream is called “dewatered sludge cake” and is currently hauled to the Vernon Composting Facility at a rate of 2.5 truckloads (~60 wet tonnes) per day. The dewatered sludge cake was the first waste stream evaluated in this study as a potential substrate for anaerobic co-digestion. The dewatered sludge cake at 17.5% TS is too concentrated to digest by itself. Therefore, samples of sludge cake were diluted to 4.5 ± 0.5% TS with tap water to lower the solids loading to a level of a typical anaerobic digester. Illustration 3.1 shows the sewage sludge cake before and after it has been diluted.  34  Illustration 3.1 Sewage sludge cake before and after dilution  3.1.2  Industrial (fruit-juice) waste streams  Two industrial waste streams, taken from Brandt’s Creek Tradewaste Treatment Plant (BCTTP), were evaluated for their potential of anaerobic co-digestion. Daily, BCTTP treats approximately 1100 m3/day of wastewater. The wastewater stream is a combination of fruit juice industry wastewater generated from Sun-Rype Products Ltd. and winery wastewater from Calona Wines Ltd. with volumetric flow rates of 775 m3 and 333 m3 per day, respectively. The combined wastewater stream entering BCTTP (Figure 3.2) is pumped to an 85 µm Salsnes screen, which collects large solids such as apple seeds and skins (Illustration 3.2a). This waste stream is referred to as “screen cake” and used in this study as one of the two industrial streams. Upon screening, wastewater enters to an equalization tank for flow/load equalization. Before entering the aerobic basin for biological treatment, an anaerobic selector adds ammonia and phosphorus nutrients to the wastewater. The biological treatment is achieved in an activated sludge unit consisting of an aeration basin and two clarifiers. Operation sludge and hydraulic retention times are 25 days, and 72 hrs, at winter/summer production rate, respectively. The aeration basin contains two 35  aerators that transfer air to its content. The excess of ‘waste activated sludge’ generated in the aeration tank is first settled in the secondary clarifiers and then is sent to a DAF tank to increase the sludge concentration to a range in 3% to 5% TS. The solid effluent from DAF results in the form of thickened waste activated sludge (TWAS). This stream (Illustration 3.2b) is referred to as “industrial TWAS” and used in this study as the second industrial waste. The treated industrial wastewater from the secondary clarifiers is sent to the City of Kelowna’s sewage system for further treatment. Currently, there is a weekly production of 1 m3 of screen cake, which is disposed in the Glenmore Landfill. The industrial TWAS is produced at a rate of ~25 wet tonnes per day and is then shipped to a farmland in Vernon (BC), where it is used as fertilizer. Farmland may change ownership in the near future, and there is a possibility that a future owner might not want to use this industrial stream. Therefore, this study incorporated both screen cake and industrial TWAS streams as potential substrates for the anaerobic co-digester.  36  Figure 3.2 Brandt’s Creek Tradewaste Treatment Plant process diagram (MLSS: Mixed liquor suspended solids)  37  A  B  Illustration 3.2 A) Screen cake obtained from the Salsnes screen. B) Thickened waste activated sludge obtained from the top of the dissolved air flotation tank at the Brandts Creek Tradewaste Treatment Plant  38  3.1.3  Landfill leachate  Glenmore Landfill is a site for the disposal of inorganic and organic solid waste materials including kitchen waste: as it is presented in Figure 3.3. Glenmore Landfill has various waste management stages, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling). The leachate (liquid that drains from the landfill) has been collected and pumped to the City sewer system for several years. In recent years, the City has been installing perforated piping in the landfill pile to allow for circulation of leachate back to increase the moisture content of the pile and to accelerate the decomposition of organic solid waste. The same perforated pipes are used to collect/capture biogas (50-52% methane) generated within the landfill. The City has added three microturbines (90 kW total capacity) to allow for electricity generation from the methane. However, due to high impurities in the landfill gas, such as corrosive H2S and siloxanes, the performance of microturbines were compromised. Very recently, Fortis BC has received approval from the BC Utilities Commission for design/construction of a landfill gas purification plant at the Glenmore Landfill by 2014. The purified gas will then be injected to Fortis BC’s natural gas system for use by customers.  Figure 3.3 Glenmore Landfill process flow  39  This study used the Glenmore Landfill leachate as the 4th substrate for the following reasons. Although, among the four waste streams studied, the highest volume is generated by the Kelowna’s municipal WWTP, this plant has a limited footprint and is constrained by adjacent development. Therefore, a potential anaerobic co-digester may not be located at the Kelowna's WWTP. Furthermore, there is a concern that the potential odour from the codigester will affect nearby residents. Therefore, the purpose of using landfill leachate in this study was to evaluate whether a potential co-digester located near the Glenmore Landfill instead can utilize the excess leachate stream along with other municipal and industrial waste to provide moisture for dilution, as well as alkalinity, without having any inhibitory effect (due to the potential presence of heavy metals) on the acid and methane formers in the digester. As the final advantage, methane recovered from anaerobic co-digester can be connected and utilized as part of the existing landfill biogas system for electricity generation. 3.2  Inocula samples used as digester seed and acclimation  Mesophilic (35oC) inoculum (mixed culture of acid and methane forming bacteria) was taken from the effluent line of a bench-scale (6 L) automated anaerobic sludge digester in the Environmental Engineering Laboratory at the UBC Okanagan. The digester had been treating a mixture of TWAS and fermented primary sludge from Kelowna’s municipal WWTP, with a volumetric ratio of 60:40 at a sludge retention time (SRT) of 20 days. Thermophilic (55oC) inoculum was taken from the effluent line of the full-scale thermophilic sludge digesters at Annacis Island WWTP in Vancouver (BC, Canada). Annacis Island plant contains physical, biological, and chemical treatment units. Preliminary phase (screening and grit removal) and primary sedimentation were followed by trickling filters and secondary clarifiers. The full-scale digesters are fed with a mixture of primary sludge and WAS, and undergoes an extended (approximately 20-d SRT) thermophilic anaerobic process to ensure pathogen reduction. Sludge dewatering is done with centrifuges to 30% TS before disposal. Before setting up the actual bench-scale digesters with inocula, four digesters (2 mesophilic and 2 thermophilic with 1.2 L wet volumes each) were run for 85 days to acclimatize mesophilic and thermophilic inocula to a mixture of Kelowna sewage sludge cake, industrial TWAS and screen cake at the 40  volumetric ratios corresponding to their daily generation rates, diluted with leachate. Acclimation phase, or the first phase of the experiments, was done in order to prevent severe initial inhibition or lag-phase during anaerobic digestion. All four acclimation digesters were run at an approximately 20 d-SRT. Organic loading rates of the acclimation digesters fed with the mixture of co-substrates were 1.42 ± 0.89 g TCOD/L × d. The digester feed concentrations were 4.6% TS (w/w), which can be considered as typical sludge concentrations in full-scale sludge digesters. 3.3  Anaerobic co-digestion studies  Upon inocula acclimation, second phase of the experiments, with an aim of assessing the co-digestion performance of the co-substrates, was started. For the second stage, eight labscale anaerobic digesters (total and wet volumes of 1 and 0.5 L, respectively), were set-up with acclimated inocula to optimize the performance with single and co-substrate digester feeding scenarios displayed in Table 3.1. In mesophilic (35 ± 2oC) and thermophilic (55 ± 2oC) temperature controlled shakers (at 90 rpm), digesters were evaluated on waste minimization (total or organic solids removal efficiencies), biogas (methane) production quantity/quality, coliform destruction and dewaterability performance of the digested material (digestate). The single and co-digesters were started with a safe SRT of 20 days corresponding to an organic loading rate of 2.97 ± 0.89 g TCOD/L × d. Once the steadystate was achieved (< ±10% variation in daily gas production), digesters were operated under identical loading conditions for the duration of 3 × SRT (i.e. 60 days for the SRT of 20 days [Eskicioglu et al., 2007]). Upon data collection during the steady state performance, the SRT was reduced to 10 days (organic loading rate of 4.52 ± 0.86 g TCOD/L × d) and similar operational procedure was repeated for the new SRT. Erlenmeyer flasks with 1 L volume, shown in Illustration 3.3 A, were used as anaerobic single and codigesters. The flasks were sealed with two-hole rubber stoppers, one hole for effluent port, and the second for biogas expulsion. Effluents were withdrawn and digesters were fed (once every 24 hours including weekends) through the side arm of the flask by syringes. Biogas was collected in 2 L tedlar bags, and measured by a manometer. Figure A.1 (Appendix A) shows the calibration curve for the manometer.  41  Table 3.1 Experimental plan for acclimation and anaerobic single and co-digestion stagesª Total (wet) Stage  Goal  Digester code  Substrate flowrate contributions for digester feed  Sludge  digester  Sludge cake  TWAS  Screen cake  Leachate  retention  volume  (1)  (2)  (SC)  (L)  time  M/AC 1  Acclimation  M/AC/d  o  2 (1.2) L  9.7 mL/d  3.7 mL/d  0.6 mL/d  36 mL/d  20 d 55oC  T/AC/d  (diluted with T/1 1 (0.5) L  0  0  20 d, 10 d  o  55 C 35oC  M/2 25 (50) mL/d  0  0  20 d, 10 d  o  T/2  55 C  M/1+2+L  35oC 5 (10) mL/d  Co-digestion  0  tap water) 0  2  35oC  25 (50)† mL/d  M/1  digestion  temp. 35 C  T/AC  Single  Digester  T/1+2+L  2 (4) mL/d  0  18 (36) mL/d  20 d, 10 d  1 (0.5) L  55oC 35oC  M/1+2+SC+L 4.8 (9.6) mL/d  1.9 (3.8) mL/d  0.3 (0.6) mL/d  18 (36) mL/d  T/1+2+SC+L  20 d, 10 d  55oC  ªTWAS: thickened waste activated sludge; M: mesophilic; T: thermophilic; AC: acclimation; SC: screen cake; L: leachate †Flowrate contributions with and without parenthesis are for sludge retention times of 20 and 10 days, respectively  42  A  B 1  2 3  4  Illustration 3.3 A) Eight semi-continuous digesters (four thermophilic and four mesophilic). B) Digester configuration 1: Effluent port, 2: Biogas exit, 3: Influent port, and 4: Tedlar bag  3.4  Volumetric ratios for co-substrates in digester feed streams  Kelowna municipal WWTP currently treats wastewater from about 80% of the population. Treatment plant load is constant throughout the whole year. Daily sludge cake production for 2012 was 60 wet tones /d (~17-20% TS by weight). Slight changes may occur during the different seasons throughout the year. Fruit juice and wine industry production rates depend on harvest season of fruit. Hence, Brandt’s Creek’s wastewater treatment volume is not constant throughout the whole year. Major wastewater volumes are expected during winter (at the end of the harvesting in Kelowna), and lower by summer. Industrial TWAS normalized production rate is 26,000 43  L/d (~3-4.5% TS by weight). Screen cake amounts are 1 m3 per week during high season production. Due to the significant differences in production rates, it was decided to test the co-digestion of these waste streams based on their production rate. For simple references, single digesters fed with sewage sludge cake were labeled as “1”. Industrial TWAS was identified as “2”. Co-digestion of sewage sludge cake, TWAS and leachate for dilution was identified as “1+2+L”, and co-digestion of the four waste streams including screen cake was labeled as “1+2+SC+L”. According to temperature ranges, mesophilic digesters are “M” and thermophilic: “T” as indicated in Table 3.1. It is also necessary to emphasize that, in addition to digester scenarios displayed in Table 3.1, one additional single digestion scenario with leachate only was studied in order to quantify biogas (methane) contribution from leachate in the co-digesters. The leachate digester was operated for a period of 20 days. Due to very small amount of daily biogas production, it was decided to not to monitor this digester any further. Results are summarized in Appendix B.  3.5  Characterization of samples  Samples were characterized at room temperature (20 ± 2oC). Sample characterization consisted of pH, alkalinity, total and volatile solid contents (TS/VS), total and soluble chemical oxygen demands (TCOD/SCOD), volatile fatty acids (VFAs), total sugars and ammonia measurements. To separate soluble from total solid fractions, sludge samples were centrifuged at 8000 rpm for 20 minutes using a Fisher Scientific Sorvall Legend XT automatic centrifuge and pre-filtered and then filtered through membrane filters with 1.2 μm and 0.45 μm pore sizes, respectively. In addition to parameters mentioned above, dewaterability, total coliform concentrations were measured in digester effluents at the end of each SRT to assess digestate quality for land application as fertilizer. Analytical tests and frequency of sample characterization are shown in Table 3.2.  44  Table 3.2 Characterization of samples and frequency of analysisª Samples  Parameters  Frequency  Raw waste streams  TS, VS, TCOD, SCOD, pH,  After each sampling from  (substrate)  alkalinity, ammonia, TVFAs  treatment plants (bi-weekly)  TS, VS, TCOD, SCOD, pH,  Upon preparation of feed with  alkalinity, ammonia, TVFAs  fresh substrates  pH  Daily  TS, VS, TCOD  Every three days  Alkalinity, ammonia, total,  Once a week  Digester feed  Digester effluents  TVFAs Coliform test (total coliform  Minimum two sets of data for  and Escherichia.coli) and  each SRT at steady state  dewaterability  Digester biogas  Biogas volume  Daily  Biogas composition (CH4,  Every three days  CO2, N2, O2 percentages) ªTS: total solids, VS: volatile solids, TCOD, SCOD: total, and soluble chemical oxygen demands, respectively, TVFA: total volatile fatty acids, SRT: sludge retention time  3.5.1  Total solids and volatile solids  Total and volatile solids procedures were based on Standard Methods 2540 B and 2540 E (APHA, 2005), respectively. A well-mixed sample was evaporated in a weighed porcelain dish and dried to constant weight in the oven overnight, at 103 to 105oC. Subsequently, the dishes were weighted, TS was increased in weight over that of the empty dish. The residue of the TS was ignited to constant weight at 550oC. The weight lost during ignition was the VS fraction.  3.5.2  Chemical oxygen demand (COD)  The closed reflux colorimetric COD measurements were performed based on Standard Methods procedure 5220D (APHA, 2005). The dichromate ion oxidizes the COD materials in the sample. This results in the change of chromium ion from hexavalent to trivalent state. 45  In this method, samples were digested for 3 hours at 150oC. Samples were pre-diluted and diluted before addition of reagents and digestion. With Spectronic 20D+ (Thermo-Electron Corporation) spectrophotometer and 600 nm wavelength, the absorbance were read. A standard curve (refer to Appendix A, Figure A.2) corresponding to 100-700 mg COD/L was generated using potassium hydrogen phthalate solution as standard.  3.5.3  Alkalinity  Alkalinity of samples were determined according to Standard Method 2320B (APHA, 2005). In this method, 15 mL of supernatant of sample (centrifuged for 20 minutes at 8,000 rpm) were titrated with 0.1 N sulfuric acid to reach a pH value of 4.6. Alkalinity measurements were carried out using a pH/ion electrode connected to the accumet excell XL25 dual channel pH meter.  3.5.4  Ammonia  Dissolved ammonia concentration measurements were done on supernatant of samples. An ammonia selective electrode connected to the accumet excell XL25 dual channel pH/ ion meter was used for analyses. Measurements were done according to Standard Methods 4500-NH3 D procedures (APHA, 2005). In this method, dissolved ammonia (NH3(aq) and NH4+) is converted to NH3(aq) at pH above 11. Ammonia-N calibration curve is presented in Figure A.3 (Appendix A).  3.5.5  Gas Chromatography for volatile fatty acids (VFAs) and biogas composition  Total VFAs: acetic, propionic and butyric acids, were measured by injecting sample supernatants (filtered through a membrane with 0.2 µm pore size) into the Agilent 7890A Gas Chromatograph with a capillary column (Agilent 19091F-112, HP-FFAP polyethylene glycol TPA column length x ID: 25 m, 320 µm). Detector was a flame ionization system (oven, inlet and outlet temperatures: 200, 220 and 300oC, respectively, carrier gas flow rate: 25 mL helium/min) equipped with an autosampler. According to Ackman (1972), iso46  butyric acid was used as the internal standard. Biogas composition in the headspace of labscale anaerobic digesters and co-digesters was determined with an Agilent 7820A Gas Chromatograph with a packed column (Agilent G3591-8003/80002). The detector of this system was thermal conductivity (oven, inlet and outlet temperatures: 70, 100 and 150oC, respectively) using helium as the carrier gas (flow rate: 25 mL/min). The method was developed by van Huyssteen (1967).  3.5.6  Dewaterability  Dewaterability of digestate samples were tested by a Capillary Suction Timer (CST, Model 440, Fann Instrument Company, TX, USA) based on Standard Methods Procedure 2710G (APHA, 2005). According to this method, a sample volume of 5 mL was injected into a small cylinder placed on a sheet of chromatography paper. While the paper extracts liquid from the sludge by capillary suction, water released from sludge travels between two contact points. A digital timer attached to the electrodes records the capillary suction time. In this work, sludge temperature was constant (21 ± 1oC); also TS were tested in the digestate samples, to normalize the data in units of sec/g TS.  3.5.7  Total coliforms  Total coliforms were tested with a semi-automated system, measuring presence and quantification of pathogens in terms of total coliforms and Escherichia coli (E.coli). Using a most probable number (MPN) method, Colilert test, after 24 h incubation, will count total coliforms present (IDEXX Colilert Quanti-tray 2000). The procedure was developed by IDEXX Laboratories and was previously tested by other researchers (Coelho et al., 2011) on digestate samples with similar solid concentrations. The method provides 95% confidence limits comparable to the membrane filtration method and can count up to 2142 colony forming units (CFU)/mL without dilution. Dilutions were done prior to testing.  47  Chapter 4: Results and discussion 4.1  Characterization of raw industrial and municipal waste streams  The results for characterization of the four different waste streams are summarized in Table 4.1. Both sewage sludge cake and screen cake (SC) had slightly acidic (less than 6) pH values, compared to neutral pH levels of industrial TWAS (2) and leachate. Furthermore, sludge cake had a high concentration of TVFA, which could be due to natural decomposition of this high-strength waste during storages on site or in the fridge. From June 7th, till December 13th, 2012 there were 10 sampling times, with a variation of ± 33% for industrial TWAS and SC, variations for characterization of leachate and sewage sludge cake were below ± 10%. The higher variation in the industrial waste streams were due to changes in the fruit-juice production. Glenmore landfill is a mature landfill, therefore the leachate contains low TS, VS concentrations and VS/TS ratios (Table 4.1). Table 4.1 Characterizations of raw municipal and industrial waste streams studiedª Parameter  Sludge cake  2 (TWAS)  SC (Screen cake)*  Leachate  pH (-)  5.52 ± 0.17†  6.54 ± 0.25  5.54 ± 0.96  7.13 ± 0.10  TS (% w/w)  17.44 ± 0.66  2.43 ± 0.22  21 ± 3  0.53 ± 0.02  VS (% w/w)  14.96 ± 0.69  2.06 ± 0.21  19 ± 4  0.09 ± 0.01  85.78  84.61 ± 2.99  90.48  0.18 ± 0.02  TCOD (mg/L)  196,024 ± 31488  21,904 ± 155  91,728 ± 36318  703 ± 349  SCOD (mg/L)  10,609 ± 4360  1,403 ± 41  --  446 ± 106  733 ± 208  370 ± 141  --  3,489 ± 222  427 ± 38  8.33 ± 3.21  --  84 ± 2  1,679 ± 102  36.29 ± 3.34  --  21.17 ± 14.95  VS/TS*100 (%)  Alkalinity (mg CaCO3/L) Ammonia (mg NH3-N/L) TVFA (mg/L)  ªTS: total solids, VS: volatile solids, TCOD, SCOD: total, and soluble chemical oxygen demands, respectively, TVFA: total volatile fatty acids, TWAS: thickened waste activated sludge *Due to high solid concentration, there was no supernatant volume for SCOD, alkalinity, ammonia and TVFA analyses †Data represent the arithmetic mean of triplicates ± standard deviation  48  Among the substrates characterized (Table 4.1), the leachate had the highest alkalinity, a neutral pH, and lower ammonia concentration. Alkalinity presence is necessary in order to get a stable first stage of anaerobic digestion: hydrolysis and acidogenesis (Demirel and Scherer, 2008). Alkalinity is the buffering system necessary to a potential high VFA accumulation during digestion (Monou et al., 2008). Also, methanogenic bacteria are most likely to cease their growth due to ammonia inhibition (Cuetos et al., 2011). Consequently, low ammonia concentrations in the digester feed are preferred in order to have a stable anaerobic environment. Hence, leachate with all these advantages makes it a valuable cosubstrate to dilute concentrated waste streams (i.e., sludge and screen cakes) fed to an anaerobic digester. Industrial TWAS was the only substrate that could be fed to a digester (without dilution) as single substrate due to its sludge concentration (2.43% TS). Finally, VS/TS × 100 ratios reported in Table 4.1 indicated high organic fractions (> 84%) with significant biodegradation potential; and, this was further assessed by bioreactor studies within this project.  4.2  Characterization of diluted industrial and municipal waste streams  Characterization of raw and diluted waste mixtures, after each sampling from the WWTPs (Kelowna WWTP and BCTTP), was essential in order to understand seasonal variations. For co-digestion scenarios, waste streams were mixed according to their daily production rates and also utilized landfill leachate to bring (dilute) the solids concentrations down to typical digester influent concentrations. Table 4.2 displays the feed characterization for both single as well as co-digestion scenarios after dilution/mixing according to Table 3.1. As it can be seen from Table 4.2, although waste streams of 1, L and 1+2+SC+L had similar TS, VS and COD concentrations, VS/TS ratios of the 1+2+SC+L was the lowest. Furthermore, the co-digester feeds had higher alkalinity due to addition of landfill leachate, which provided an advantage/additional buffering capacity. Overall, the characterization results indicated that the mixture of the four substrates (waste streams) produced safe pH, ammonia, alkalinity, VFA levels.  49  Table 4.2 Characterizations of diluted waste streams as digester feedª Anaerobic single digestion Parameter  Anaerobic co-digestion  (1)  (2)  1+2+L  1+2+SC+L  pH (-)  5.72 ± 0.26†  6.54 ± 0.25  6.61 ± 0.24  6.72 ± 0.11  TS (% w/w)  4.48 ± 0.05  2.43 ± 0.22  4.33 ± 0.28  4.39 ± 0.29  VS (% w/w)  3.81 ± 0.04  2.06 ± 0.21  3.65 ± 0.31  3.38 ± 0.17  VS/TS × 100 (%)  85.16 ± 1.42  84.77 ± 2.91  84.27 ± 5.10  77.20 ± 5.01  TCOD (mg/L)  41,620 ± 166  21,904 ± 155  41,049 ± 1813  43,874 ± 385  SCOD (mg/L)  5,336 ± 109  1,403 ± 41  5,929 ± 148  6,371 ± 89  728 ± 396  370 ± 141  2,572 ± 702  2,416 ± 617  287.38 ± 142.82  8.33 ± 3.21  268.79 ± 88.16  251.84 ± 65.66  Alkalinity (mg CaCO3/L) Ammonia (mg NH3N/L)  Volatile Fatty Acids (VFAs) Acetic acid (mg/L) Propionic acid (mg/L) Butyric acid (mg/L)  862 ± 456  17 ± 9  649 ± 61  668 ± 72  558 ± 127  17 ± 11  383 ± 36  401 ± 35  264 ± 24  2±1  162 ± 24  162 ± 22  7.5:1  n/a*  Nutrient availability C:N ratio²  7.4:1  12.1:1  ª(1): diluted sewage sludge, (2): industrial TWAS, SC: screen cake, L: leachate, TS: total solids, VS: volatile solids, TCOD, SCOD: total, and soluble chemical oxygen demands, respectively, TVFA: total volatile fatty acids †Data represent the arithmetic mean of triplicates ± standard deviation) *Could not be estimated due to absence of data for total nitrogen and phosphorus in screen cake. However screen cake, comprised of fruit seed and skin, is expected to contain total nitrogen and phosphorous, therefore this substrate mixture should contain C:N:P values as minimum as 1+2+L ²C:N ratios in municipal sludge cake and leachate were reported by City of Kelowna and in industrial TWAS by Sun-Rype Beverage Inc.  As it was emphasized earlier, the ideal C:N ratio for anaerobic digestion ranges from approximately 30:1 to 35:1 (Droste, 1997). Higher ratios will produce a slower digestion rate. The addition of co-digestion materials can improve the C:N ratio, thereby increasing methane production. In this study, C:N ratios were reported in Table 4.2 for the feed 50  streams for both single and co-digestion scenarios. In general, fruit juice wastewaters are well known for poor nutrient contents (Ozbas et al., 2006). Therefore, BCTTP adds nutrients to its wastewater before it enters into the biological treatment process. On the other hand, in general municipal waste streams do not need external nutrient addition due to high urea content. Due to these reasons, after characterization, both municipal and industrial streams indicated adequate nutrient content in Table 4.2.  4.3  Inoculum acclimation to waste streams studied  As it was described in Chapter 3, both mesophilic and thermophilic inocula were acclimated to a mixture of waste streams comprised of municipal sludge cake, industrial TWAS and screen cake at volumetric ratios representing their daily production rates. As the initial inocula were taken from anaerobic digesters treating only municipal sludge, acclimation phase was necessary for both acid and methane forming bacteria to adapt themselves to industrial waste streams. The adequate acclimation period minimizes inhibition risk on methanogenic bacteria, sensitive to environmental changes and inhibitory substances and improves the biodegradation rate (Droste, 1997). When the mesophilic and thermophilic inocula were being acclimatized in four semicontinuously fed digesters, daily biogas productions reached a stable value. Steady state was defined as the period of time in which less that 10% variation was observed from data related to biogas production, organic (solids or COD) removal efficiencies, or digester pH readings (Schimel and Boone, 2010). Table 4.3 summarizes the loading conditions as well as steady state biogas and methane yields achieved from the acclimation reactors, fed in a semi-continuous mode. The four digesters were acclimatized to industrial sludge without any indication of acute or chronic toxicity. Table 4.4 summarizes thermophilic and mesophilic inocula characterization before and after acclimation phase. After acclimation, lab-scale anaerobic digesters were set-up with these acclimatized inocula.  51  Table 4.3 Steady state results for acclimation semi-continuous digestersª Mesophilic (35oC)  Thermophilic (55oC)  digesters  digesters  20  20  4.0 ± 3†  3.8 ± 5  Daily biogas production (mL/d)  1,221 ± 50  1,172 ± 9  Specific biogas yield (L/g VS removed × d)  0.92 ± 0.09  1.08 ± 0.07  Methane (CH4) composition in biogas (%)  66.28 ± 1.00  66.39 ± 1.43  Specific methane yield (L/g VS removed × d)  0.61 ± 0.02  0.72 ± 0.01  Parameter Sludge retention time (SRT) (d) Organic loading rate (OLR) (g TCOD/L × d)  ªVS: volatile solids, TCOD total chemical oxygen demands †Data represent the arithmetic mean of 30 data points, duplicates ± standard deviation Table 4.4 Inocula characteristics before and after acclimation Mesophilic (35oC) inoculum Parameter  Thermophilic (55oC) inoculum  Before acclim.  After acclim.  Before acclim.  After acclim.  pH (-)  7.52 ± 0.05†  7.65 ± 0.07  8.01 ± 0.01  7.95 ± 0.02  TS (% w/w)  2.68 ± 0.15  3.28 ± 0.02  1.93 ± 0.00  2.91 ± 0.07  VS (% w/w)  1.79 ± 0.02  2.38 ± 0.01  1.40 ± 0.01  2.06 ± 0.05  TCOD (mg/L)  17,857 ± 3030  25,847 ± 2549  18,714 ± 202  28,124 ± 983  SCOD (mg/L)  7,936 ± 768  1,211 ± 82  1,236 ± 10  3,216 ± 122  5,325 ± 35  3,342 ± 63  8,967 ± 210  5,737 ± 210  799 ± 37  1,124 ± 101  252 ± 19  1,610 ± 194  52.29 ± 0.03  104.3 ± 0.19  2.81 ± 0.01  56.78 ± 12.78  Alkalinity (mg CaCO3/L) Ammonia (mg NH3-N/L) TVFA (mg/L)  ªTS: total solids, VS: volatile solids, TCOD, SCOD: total, and soluble chemical oxygen demands, respectively, TVFA: total volatile fatty acids †Data represent arithmetic mean of triplicates ± standard deviation  52  4.4  Effect of addition of co-digestion materials on digester performance  Upon acclimation, the actual single and co-digesters were continuously operated for another 4 months, achieving steady states at two different SRTs. Digestion operation started at a safe SRT of 20 d (Khanal, 2008), OLR starting from 1.41 ± 0.77 g TCOD/L/d (Table 4.5). Long SRTs with a lower organic loading are always used first in lab-scale digesters in order to avoid instability until microbial culture is fully acclimatized (Schimel and Boone, 2010). Steady state was accomplished after a week of digestion and digesters were kept under the same loading for another 74 days. After completion of the 20-d SRT, the SRT was reduced to 10 d (OLR of 3.02 ± 0.12 g TCOD/L/d (Table 4.6)). Under this 10-d SRT period, steady state conditions were achieved after 3 days of operation (based on biogas production) and data were collected for another 38 days under the same loading. The data collected during the un-steady state were not presented in this thesis. Figure 4.1 shows daily biogas productions at standard temperature and pressure (STP; 0oC, 1 atm). This figure is an example of a digester operational pattern during steady state conditions. Additionally, Figure 4.1 shows the transition between the changes of SRTs from 20 d to 10 d. From Figure 4.1, at the 20-d SRT, mesophilic digesters with higher average biogas production were 1 (digester M-1: 433 ± 15 mL/d) and 1+2+L (digester M1+2+L: 411 ± 23 mL/d). During the 10-d SRT, the digesters that generated the highest daily average biogas volume were: 1+2+SC+L (M-1+2+SC+L with 731 ± 18 mL/d) and 1 (M-1 with 715 ± 14 mL/d). On the other hand, at both SRTs, digester M-2 was the lowest in producing biogas. For thermophilic digesters, through the 20-d SRT, daily average biogas productions were up to 418 ± 11 mL/d, with the digester T-1+2+SC+L being the highest producer. While thermophilic digesters were running with 10-d SRT loadings, higher biogas producers were T-1+2+L (T-1+2+L with 702 ± 17 mL/d) and T-1 (T-1 with 701 ± 20 mL/d). From these results, no significant differences were observed in the biogas production pattern of digesters fed with 1, 1+2+L and 1+2+SC+L. The addition of industrial co-substrates to municipal sludge cake did not improve or deteriorate biogas production from the municipal waste stream. 53  Furthermore, between the single digestion scenarios, the scenario of 2 with industrial TWAS only, had the lower performance. At both mesophilic and thermophilic temperatures and SRTs, digester 2 was the lowest biogas producer. In addition, as it can be seen from Figure 4.1, at the SRT of 10 days, digester 2 could not achieve steady state with biogas production gradually declining at both mesophilic and thermophilic digester temperatures. It is also necessary to emphasize that Brandt’s Creek juice production rate is seasonal; therefore, significant changes have been found in their waste characterization according to the time of the year. Furthermore, the average daily biogas productions are directly linked to total and organic (volatile) solids fed to digesters with incoming streams. The higher solids present in digester feed should yield more biogas volumes. Therefore to be able to compare biogas yields for different digestion scenarios with varying solids concentration as in this study (Table 4.2), normalizations should be made. Figure 4.2 shows the specific daily biogas volumes normalized per g volatile solids (VS) removed during digestion.  54  A  1  800  2  1+2+L  1+2+SC+L  Sludge retention time = 20-d  Daily biogas production (mL/d)  600 400 200 0 0  20  40  60  B  80  100  120  Sludge retention time = 10-d  800 600 400 200 0 0  20  40  60  80  100  120  Digestion time (days)  Figure 4.1 Daily biogas productions (@STP) of anaerobic digesters fed with diluted sewage sludge cake (1), Thickened waste activated sludge (2), 1+2+L (leachate), and 1+2+SC+L (screen cake). A) Mesophilic digesters, B) Thermophilic digesters  55  1  Specific daily biogas production (L/g VSremoved)  A  2  1+2+L  1+2+SC+L  1,4 1,2 1 0,8 0,6 0,4 0,2 0  Sludge retention time = 10-d  0 B  20  40  60  80  100  120  60  80  100  120  Sludge retention time = 20-d 1,4 1,2 1 0,8 0,6 0,4 0,2  0 0  20  40  Digestion time (days)  Figure 4.2 Specific daily biogas productions (@STP) of anaerobic digesters fed with diluted sewage sludge cake (1), Thickened waste activated sludge (2), 1+2+L (leachate), and 1+2+SC+L (screen cake). A) Mesophilic digesters, B) Thermophilic digesters  56  The averages of specific biogas yields from 8 digesters were similar or above of the expected biogas yield, reported by Droste (1997) as 1 L/g VSremoved × d for municipal mixed (primary + secondary) sludge. For mesophilic conditions through the 20-d SRT, single substrate digester (2) utilizing industrial TWAS only had the highest yields numbers. However, for the 10-d SRT, co-substrate digesters had a better performance as it is shown in Figure 4.2.B. Thermophilic digesters during the 20-d SRT had a different pattern: codigested substrates had a higher specific biogas yield compared to single digestion. Same behavior as mesophilic digesters, while 10-d SRT was running, thermophilic co-digesters had the highest specific biogas yields. Similar to responses analyzed for Figure 4.1, single and co-digested digesters did not indicate any instability problems at the 20-d SRT in terms of specific daily biogas volumes normalized based on solids removal (Figure 4.2). However, digesters M-2 and T-2 at 10-d SRTs started to reduce their specific biogas productions (Figure 4.2), which is in agreement with the patterns observed in Figure 4.1. This biogas generation decline started after 20 days of running at 10-d SRT. Summarized steady state values of the monitored parameters during 20-d SRT and 10-d SRT are shown in Table 4.5 and Table 4.6, respectively.  57  Table 4.5 Results for semi-continuous digesters at 20 d SRT during steady state* SRT = 20 d Mesophilic Parameter  1  2  Thermophilic  1+2+L  1+2+SC+L  1  2  1+2+L  1+2+SC+L  Loading rates for digesters OLR (gTCOD/L × d) OLR (gsubstrate/d) Specific CH4 yield (L/g VSremoved × d) Specific CH4 yield (L/g VSadded × d) Removal efficiencies TS (%)  2.73(0.79)†  1.41(0.77)  2.84(0.92)  2.97(0.89)  2.73(0.79)  1.41(0.77)  2.84(0.92)  2.97(0.89)  3.77(0.12)  2.19(0.23)  3.81(0.26)  3.73(0.36)  3.77(0.12)  2.19(0.23)  3.81(0.26)  3.73(0.36)  0.53(0.07)  0.35(0.05)  0.45(0.09)  0.55(0.04)  0.48(0.04)  0.38(0.05)  0.45(0.06)  0.50(0.04)  0.23(0.03)  0.13(0.03)  0.24(0.03)  0.24(0.02)  0.22(0.01)  0.16(0.05)  0.23(0.02)  0.25(0.01)  36.75(4.17)  27.66(3.94)  40.42(6.71)  40.03(3.66)  39.06(5.78)  33.25(5.77)  40.95(4.28)  43.21(3.16)  43.01(2.57) 36.81(6.80) 50.21(2.64) 44.20(4.41) 46.62(3.65) 41.04(5.25) 51.02(4.12) 49.22(2.60) VS (%) 54.89(4.57) 50.49(14.13) 56.58(7.58) 58.54(10.22) 58.06(4.93) 55.57(10.79) 58.51(6.81) 61.27(7.94) TCOD (%) 7.37(0.16) 7.26(0.16) 7.48(0.16) 7.50(0.17) 7.92(0.15) 7.83(0.13) 7.98(0.24) 8.12(0.12) Reactor pH (-) Effluent supernatant characterization Alkalinity 3,936(230) 2,535(412) 4,503(839) 5,032(462) 4,816(258) 3,536(373) 4,901(1077) 5,596(751) (mg CaCO3/L) Ammonia 1,476(392) 772(184) 1,161(258) 1,235(342) 1,588(542) 1,057(355) 1,475(465) 1,406(422) (mg NH3-N/L) 117(20) 4(3) 58(16) 166(57) 86(16) 25(3) 343(39) 144(102) TVFA (mg/L) *SRT: sludge retention time, OLR: organic loading rate, TS: total solids, VS: volatile solids, TCOD: total chemical oxygen demands, respectively, TVFA: total volatile fatty acids †Data represent the arithmetic mean of minimum of duplicates for loading rates and 74 replicates for the remaining parameters collected during steady state (standard deviation)  58  Table 4.6 Results for semi-continuous digesters at 10 d SRT during steady state* SRT = 10 d Mesophilic Parameter  1  2  1+2+L  Thermophilic 1+2+SC+L  1  2  1+2+L  1+2+SC+L  Loading rates for digesters OLR 4.02(0.22) 3.02(0.12) 3.98(0.21) 4.38(0.23) 4.02(0.22) 3.02(0.12) 3.98 (0.21) 4.38(0.23) (gTCOD/L × d) OLR 7.80(0.38) 4.52(0.86) 7.76(0.12) 7.66(0.86) 7.80(0.38) 4.52(0.86) 7.76(0.12) 7.66(0.86) (g substrate/d) Specific CH4 yield 0.40(0.04) 0.22(0.20) 0.39(0.05) 0.45(0.03) 0.37(0.04) 0.32(0.15) 0.40 (0.04) 0.42(0.04) (L/g VSremoved × d) Specific CH4 yield 0.19(0.03) 0.08(0.05) 0.19(0.03) 0.21(0.01) 0.18(0.03) 0.13(0.05) 0.19(0.02) 0.20(0.02) (L/g VSadded × d) Removal efficiencies 38.56(4.12) 29.67(4.13) 42.28(5.01) 43.71(6.80) 42.02(4.38) 39.78(4.58) 40.56(3.59) 40.69(3.55) TS (%) 47.39(3.67) 39.05(6.34) 47.32(3.00) 46.28(2.82) 49.07(4.29) 40.96(5.57) 48.25(2.27) 47.24(4.32) VS (%) 45.95(7.21) 31.62(7.29) 50.34(3.43) 57.43(4.38) 42.67(5.01) 40.45(10.07) 46.90(9.14) 50.76(5.84) TCOD (%) 7.48(0.09) 6.99(0.27) 7.59(0.09) 7.68(0.10) 7.93(0.09) 7.71(0.17) 8.17(0.07) 8.20(0.15) Reactor pH Effluent supernatant characterization Alkalinity 3,810(390) 2,097(292) 4,967(354) 5,257(301) 4,633(1019) 3,512(418) 5,958(302) 5,908(319) (mg CaCO3/L) Ammonia 1,764(342) 849(102) 1,485(262) 1,641(194) 2,368(413) 1,475(196) 2,178(261) 2,171(260) (mg NH3-N/L) 109(20) 985(287) 144(53) 65(26) 1,074(498) 1,067(254) 798(260) 738(33) TVFA (mg/L) *SRT: sludge retention time, OLR: organic loading rate, TS: total solids, VS: volatile solids, TCOD: total chemical oxygen demands, respectively, TVFA: total volatile fatty acids † Data represent the arithmetic mean of minimum of duplicates for loading rates and 38 replicates for the remaining parameters collected during steady state (standard deviation)  59  As shown in Tables 4.5 and 4.6, specific methane yields for the 20-d SRTs varied from 0.35 to 0.55 L/g VSremoved × d. Mesophilic digesters had the highest methane yields compared to digesters ran at thermophilic temperatures. For both digesters, in general, single digesters had lower specific methane yields than the co-digestion scenarios. This effect was possibly due to good buffering capacity provided by addition of the leachate (Table 4.5) for the co-digestion scenarios. For 10-d SRT digesters, specific methane yields had the same pattern, however, values were lower compared to the 20-d SRT results due to two times higher organic loading rates, challenging acid and methane formers. Organic removal efficiency can be quantified by VS and TCOD removals (Droste, 1997). In general, mesophilic and thermophilic digesters at 20-d SRT had TS removals up to 40-43%, respectively. As it is shown in Figure 4.3A, co-digesters had higher organic removals (40%43%) compared to single-substrate digesters. Figure 4.3B showed a close-up removal comparison between single and co-substrate digesters. For the 10-d SRT, mesophilic codigestion scenarios had also the higher removal efficiencies compared to single digestion scenarios. Furthermore, from Figure 4.4, it can be seen that VS removal performances of digesters did not have a significant change between 20-d and 10-d SRT. In order to understand whether the differences were statistically significant, ANOVA with two variables has been performed. Statistical analysis results for solid removal efficiencies in terms of both TS and VS removals, indicated that, with 95% of confidence, the effects of digestion temperature (mesophilic or thermophilic) and SRT (20-d or 10-d) were not significantly different. However, single and co-digestion scenarios presented statistically significant differences (p < 0.05 for TS and p ≤ 0.05 for VS removals, respectively), suggesting that co-digestion has a better performance than the single digestion in terms of solid removal efficiencies. The ANOVA analyses are shown in Appendix C.1 and C.2.  60  Mesophilic  Thermophilic  60 A Total solids removal (%)  50 40 30 20 10 0 1  2  1+2  Single digestion  1+2+SC  Co-digestion  Sludge retention time = 20 d  1  2  Single digestion  1+2  1+2+SC  Co-digestion  Sludge retention time = 10 d  60 Total solids removal (%)  B 50 40 30 20 10 0 1  1+2  Single digestion  Co-digestion  SRT = 20 d  Figure 4.3 A) Total solids removal efficiencies at sludge retention times (SRTs) of 20 and 10 days. B) Comparison of TS removal between 20d SRT mesophilic digesters (data represent the arithmetic mean of duplicates and error bars represent standard deviations, SRT: sludge retention time, TS: total solids)  61  Mesophilic A  Thermophilic  60  Volatile solids removal (%)  50  40  30  20  10  0 1  2  Single digestion  1+2  1+2+SC  Co-digestion  Sludge retention time = 20 d  Volatile solids removal (%)  B  1  2  Single digestion  1+2  1+2+SC  Co-digestion  Sludge retention time = 10 d  60 50 40 30 20 10 0 1  1+2  Single digestion  Co-digestion  SRT = 20 d  Figure 4.4 A) Volatile solids removal efficiencies at sludge retention times (SRTs) of 20 and 10 days. B) Comparison of VS removal between 20d SRT mesophilic digesters (data represent the arithmetic mean of duplicates and error bars represent standard deviations SRT: sludge retention time, VS: volatile solids)  62  Figure 4.5 shows the TCOD removal efficiencies. Values for TCOD removals in mesophilic digesters through 20-d SRT were among 58% (1+2+SC+L) and 50% (2- digesters). For 10-d SRT, removal values dropped to 57% (1+2+SC+L) and 31% (2-digesters). It is clear that both single and co-digestion scenarios were negatively affected by the higher organic loading rates at the shorter SRT, indicating reduced TCOD removals and the difference was statistically significant (p < 0.05). Furthermore, between the single and co-digesters, single digesters experienced higher level of decline in their TCOD removal performances, however the effect was statistically significant only at a confidence limit of 92% (Appendix C.3). These results once again confirmed that adding municipal waste and landfill leachate to fruitjuice waste increased the stability of anaerobic digesters. Among all the digester scenarios studies, single digestion of industrial TWAS (2) had the lowest performance in terms of TS, VS and TCOD removal efficiencies. Since industrial TWAS is purely a secondary sludge with higher amount of microbial cells creating resistance to biodegradation than those in municipal cake (60:40% secondary: primary by weight), lower biodegradation efficiencies were somewhat expected for TWAS. Furthermore, the extended HRT (72 hrs) and SRT (25 days) operational parameters used for treating fruit-juice wastewater in the activated sludge tank must have created a relatively old TWAS with highly refractory content limiting biodegradation/ methane potential. Although both mesophilic and thermophilic digesters achieved relatively stable performance at an SRT of 20 days, the daily biogas production started declining gradually at an SRT of 10 days (Figure 4.1). To be able understand the reason behind this decline observed under both mesophilic and thermophilic digestion, the feed characterization was repeated once again to account for any change that may have occurred during storage in the fridge. Due to the seasonal production in Brandt’s Creek Tradewaste Treatment Plant, the same feed was used for the last SRT (10 days) for three weeks after sampling from Brandt’s Creek WWTP. The feed characterization results, displayed in Table 4.7, indicated signs of acidification (pH drop from 6.4 to 5.6 and TVFA increase from 138 to 3259 mg/L) that occurred during storage in the fridge. It is highly probable that high VFAs being fed to the single digesters at an SRT of 10 days contributed consumption of alkalinity which eventually led to drop in reactor pH and biogas production. The co-digestion digesters, on the other hand, took advantage of the additional alkalinity  63  provided by the landfill leachate and remained stable in terms of both organic removals as well as biogas production. Mesophilic  Thermophilic  80 A  70  TCOD removal (%)  60 50 40 30 20 10 0 1  2  1+2  Single digestion  1+2+SC  Co-digestion  SRT = 20 d  1  2  1+2  Single digestion  1+2+SC  Co-digestion  SRT = 10 d  80  B TCOD removal (%)  70 60 50 40 30 20 10 0 1  1+2+SC  Single digestion  Co-digestion  SRT = 20 d  Figure 4.5 A) Total chemical oxygen demand removal efficiencies at sludge retention times (SRTs) of 20 and 10 days. B) Comparison of TCOD removal between 20d SRT mesophilic digesters (data represent the arithmetic mean of duplicates and error bars represent standard deviations SRT: sludge retention time, TCOD: total chemical oxygen demand)  64  Table 4.7 Characterization of industrial TWAS on sampling date and after 3 weeks of storage in fridge Parameter  TWAS @ sampling date  TWAS after 3 weeks  pH (-)  6.41 ± 0.01†  5.55 ± 0.02  TCOD (mg/L)  22,571 ± 51  21,400 ± 485  SCOD (mg/L)  152 ± 20  142 ± 1  TS (% w/w)  2.44 ± 0.01  2.37 ± 0.01  VS (% w/w)  2.14 ± 0.01  2.06 ± 0.01  Alkalinity (mg CaCO3/L)  533 ± 94  367 ± 0  Ammonia (mg NH3-N/L)  7±2  266 ± 5  Volatile fatty acids Acetic acid (mg/L)  24 ± 12  572 ± 48  Propionic acid (mg/L)  41 ± 10  711 ± 6  Butyric acid (mg/L)  73 ± 6  1,976 ± 11  *TWAS: thickened waste activates sludge, TCOD, SCOD: total and soluble chemical oxygen demand, TS: total solids, VS: volatile solids †Data represent the arithmetic mean of triplicates ± standard deviation  Biogas composition of each single and co-digester was measured in order to assess whether substrate type has an impact on methane content of biogas accumulated in headspace. During 20-d and 10-d SRTs, all digesters had methane productions above 62%. Table 4.8 depicts the biogas composition through steady state period of the digesters. Results indicated that the methane percentage was not affected by the substrate type (single or co-digestion of different substrates). Statistical analyses results indicated that with 95% of confidence, the effect of changing digestion temperature (35 or 55oC) or substrate type (single or co-substrate) on methane percentage in biogas composition were not statistically significant (Appendix C.4). On the other hand, there was a statistically significant (p < 0.05) increase in methane percentage from the 20-d to the 10-d SRT, for both the mesophilic and thermophilic digesters. As an example of this percentage increase, methane content in digester fed with 1+2+SC+L went from 66 ± 5% to 69 ± 1% as SRT was reduced from 20 to 10 days.  65  Table 4.8 Biogas composition of single and co-digesters during steady state 20-d SRT* Mesophilic  Thermophilic  (%)  1  2  1+2+L  1+2+SC+L  1  2  1+2+L  1+2+SC+L  CH4  68 ± 2†  63 ± 3  66 ± 4  66 ± 5  62 ± 2  67 ± 3  63 ± 11  66 ± 0  CO2  29 ± 1  20 ± 1  27 ± 4  27 ± 3  23 ± 1  25 ± 1  24 ± 4  24 ± 1  O2  1±0  2±0  1±0  1±0  4±0  1±3  5±2  2±1  N2  2±1  15 ± 3  6±1  6±2  11 ± 2  8±2  8±5  8±1  10-d SRT CH4  69 ± 2  65 ± 2  68 ± 1  69 ± 1  70 ± 5  68 ± 4  68 ± 1  66 ± 2  CO2  28 ± 1  23 ± 2  26 ± 1  26 ± 1  25 ± 3  19 ± 3  26 ± 1  26 ± 1  O2  0±0  2±1  1±0  1±0  1±1  4±3  1±0  2±0  N2  3±1  10 ± 2  5±1  4±1  4±2  9±2  5±1  6±2  *SRT: sludge retention time †Data represent the arithmetic mean of 22 replicates collected during steady state ± standard deviation  4.5  Effect  of  addition  of  co-digestion  materials  on  digester  supernatant  characterization Digester stabilization was also monitored with respect to pH, as well as TVFA, alkalinity, ammonia concentrations that were measured from supernatants of the digester effluents. Methanogens are sensitive to acidic or basic environments; a safe pH range is between 6.5 and 8.5 (Tchobanoglous et al., 2004). Table 4.5 showed that, at 20-d SRT, pH values were not affected by TVFA presence. For all digesters, both mesophilic and thermophilic, TVFA values were under 250 mg/L, which is considered a safe range for anaerobic respiration (Tchobanoglous et al., 2004). However, for 10-d SRT, TVFA values were above 250 mg/L (Table 4.6). At the same time, for the majority of the digesters, alkalinity values were high enough to keep the TVFA: alkalinity ratios between 0.01-0.3, less than the suggested limits for digester failure (0.3-0.4; Droste 1997), with the exception of the single substrate digester 2, which had a TVFA: alkalinity ratio of 0.5. In this study, alkalinity measurements were in the expected range of 2,097 to 5,958 mg CaCO3/L, similar to Venkateswara et al. (2011) results with their co-digested reactors (2,250-5,000 mg/L). Bouallagui et al. (2009) codigested fruit and vegetable waste obtaining alkalinity values between 850-4,400 mg/L  66  (mesophilic) and 1,200-10,500 mg/L (thermophilic). Nevertheless, the results indicated that for a full-scale digester fed with industrial TWAS, it might be necessary to add external buffer solutions to stay below the TVFA: alkalinity ratio of 0.3 for a 10-d SRT. Between the SRTs of 20 and 10 days, since the loading rate is doubled and the pH is on acidic side, the alkalinity initially present will be consumed at a much faster rate, comprising the stability. Alkalinity values in the thermophilic digesters were higher compared to the mesophilic ones. This phenomenon was partly due to higher alkalinity originally present in the thermophilic inoculum. In addition, there is equilibrium between the digester alkalinity and carbon dioxide content in headspace. A stable digester will have pH and alkalinity ranges of 6.8-7.5 and 1,000-5,000 mg/L, respectively (Grady et al., 1999). Table 4.9 shows the effect of pH on the alkalinity of the liquid and the carbon dioxide content of the gas phase in the anaerobic process. High alkalinity concentrations will decrease carbon dioxide going into gas phase as it is shown in Table 4.9 (thermophilic digesters). Table 4.9 Relationship between theoretical and experimental CO2 content (%) in digester headspace CO2 in digester gas (%) Mesophilic (35oC) pH  Thermophilic (55oC)  Theoretical† Experimental  pH  Theoretical† Experimental  *SRT of 20 days 1  7.37(0.16)  23  29(1)  7.92(0.15)  9  23(1)  2  7.26(0.16)  24  20(1)  7.83(0.13)  7  13(2)  1+2+L  7.48(0.16)  27  27(4)  7.98(0.24)  7  24(4)  1+2+SC+L 7.50(0.17)  26  27(3)  8.12(0.12)  7  24(1)  *SRT of 10 days 1  7.48(0.09)  19  28(1)  7.93(0.09)  9  25(3)  2  6.99(0.27)  29  23(2)  7.71(0.17)  9  19(3)  1+2+L  7.59(0.09)  28  26(1)  8.17(0.07)  7  26(1)  1+2+SC+L 7.68(0.10)  28  26(1)  8.20(0.15)  7  26(1)  *SRT: sludge retention time. Data represent the arithmetic mean of 74 replicates for 20-d SRT, and 38 replicates for 10-d SRT, collected during steady state (standard deviation) †Derived using effect of pH on the carbonate alkalinity of the liquid and the carbon dioxide content (Grady et al., 1999)  67  Ammonia is generated by biodegradation of nitrogenous matter (i.e. proteins and urea) during digestion and high amounts of ammonia could inhibit methanogenic bacteria (Demirel and Scherer, 2008). Due to this concern, ammonia monitoring was done during this study (Tables 4.6-4.7). Higher ammonia was generated in thermophilic digesters compared to mesophilic digesters based on the data. Anaerobic treatment ammonia toxicity limit is around 2,000 mg/L (Bouallagi et al., 2009), causing a decrease in biogas production. On the other hand, there are conflicting studies in the literature reporting that some of the methanogenic strains are able to tolerate ammonia levels higher than 10,000 mg/L (Jarrel et al., 1987). In this study, the ammonia levels in all of the digesters during the 20-d SRT were below the toxicity limit of 2,000 mg/L. On the other hand, for the 10-d SRT, the ammonia levels in all thermophilic digesters (except T-2) were slightly above the ammonia toxicity limit as concentrations ranged in 2,100-2,300 mg/L. The fact that single digesters fed with industrial TWAS (2) did not have alarming ammonia concentrations confirms that the instability of these digesters observed at an SRT of 10 days was not due to ammonia inhibition. Grady et al. (1999) explain that alkalinity, pH, and ammonia concentrations are interconnected in anaerobic digestion. Different total ammonia concentrations can result in a toxic free ammonia concentration (100 mg/L as N), depending on the pH and temperature. The influence of pH is largely due to its effect on the equilibrium between dissolved ammonia gas (free ammonia in more toxic form) and ammonium ions. Table 4.10 describes the effect of pH and temperature on total ammonia concentrations necessary to release toxic free ammonia concentration of 100 mg/L in the system. It is clear that mesophilic digesters were below the maximum total ammonia concentration limits at corresponding digester pH values, confirming stability of the system, while thermophilic digesters were above the estimated total ammonia concentration limits for stable operation. However, thermophilic digesters were able to tolerate ammonia concentrations with no negative effect on biogas or methane production. This could be due to 3 months of inocula acclimation provided for all the digesters including thermophilic digesters prior to actual digester set-up.  68  Table 4.10 Comparison between theoretical total ammonia toxicity limit with measured total ammonia concentrations Total ammonia concentration (mg/L as N) Mesophilic (35oC) pH  Thermophilic (55oC)  Maximum† Experimental  pH  Maximum†  Experimental  *SRT of 20 days 1  7.37(0.16)  4,400  1,476 ± 392  7.92(0.15)  1,800  1,588 ± 542  2  7.26(0.16)  5,900  772 ± 184  7.83(0.13)  2,000  1,057 ± 355  1+2+L  7.48(0.16)  3,600  1,161 ± 258  7.98(0.24)  1,500  1,475 ± 465  1+2+SC+L  7.50(0.17)  3,600  1,235 ± 342  8.12(0.12)  <500  1,406 ± 422  *SRT of 10 days 1  7.48(0.09)  3,600  1,764 ± 342  7.93(0.09)  1,800  2,368 ± 413  2  6.99(0.27)  11,000  849 ± 102  7.71(0.17)  900  1,475 ± 196  1+2+L  7.59(0.09)  2,950  1,485 ± 262  8.17(0.07)  <500  2,178 ± 261  1+2+SC+L  7.68(0.10)  2,500  1,641 ± 194  8.20(0.15)  <500  2,171 ± 260  *SRT: sludge retention time †Total ammonia concentration necessary to give a toxic, free ammonia concentration of 100 mg N/L This is calculated based on dissociation of ammonia as a function of digester pH and temperature (Grady et al., 1999)  4.6  Land application of digested biosolids according to regulations  Agriculture is not possible without nutrients present in the soils. As previously mentioned, digestate may have significant nutrient values that can make it an ideal fertilizer. However, agencies such as Environmental Protection Agency (EPA) or the BC Ministry of Environment continue to create strict regulations for the land application of biosolids. These regulations are selective according to the methods for processing, reuse and disposal of biosolids. In the Province of BC, waste producers and users follow the Land Application Guidelines for the Organic Matter Recycling Regulation (OMMR) and the Soil Amendment Code for Practice established by BC Ministry of Environment (OMRR, 2008). Biosolids are classified in the OMRR as either Class A or Class B, depending on the extent to which quality criteria in terms of fecal coliforms, trace heavy metals and vector attraction are met. Vector attraction represents the characteristics related to attraction of rodents, mosquitos, or other organisms capable of transporting infectious agents. Satisfactory vector attraction can 69  be demonstrated if treatment processes applied to waste sludge can reduce the VS content by a minimum of a certain percentage, i.e. 38%. In this study, digested biosolids were quantified in terms of coliforms and dewaterability characteristics, another important factor for easier handling. Although, heavy metals presences are the major restriction that prevents the agricultural use of some sludges (Wang et al., 2006; OMMR 2008), heavy metals were not tested for the digested biosolids for the following reasons. Both City of Kelowna and BCTTP monitor the heavy metals in their waste streams (dewatered sludge cake, industrial TWAS and landfill leachate) to comply with OMRR. The average metal concentrations listed for the waste streams in Appendix D allowed us to set-up mass balances for metal concentrations entering to the digesters. As metals do not undergo biodegradation during anaerobic digestion, and also are not volatile, there will not be any decrease in concentrations during biological or physiochemical reactions. As digesters showed around 40-50% volume reductions during the digestion, it is expected that the concentrations of metals will be accumulated by 40-50% in the digested biosolids samples. The calculated concentrations tabulated in Appendix D along with the Class A and Class B criteria indicated that digested biosolids are expected to meet Class A criteria in terms of metal contents (OMMR, 2008).  4.6.1  Dewaterability  In order to follow OMRR regulation, biosolids should be dewatered for land application. It is expected that biosolids could be up to 25% of dry matter (OMRR, 2008). Dewatering reduces water content in biosolids, reducing final volumes for better handling (Radaideh et al., 2010). One of the methods to measure dewaterability is CST, which provides a quantitative measure of how readily sludge releases its water. Dewaterability results provide information such as sludge conditioning, coagulation effects and settleable solids. During anaerobic digestion, there is an agglomeration of particles resulting in a disturbance in the particle size distribution. When the anaerobic digestion process is completed, particles are destroyed, with a removal of small sizes (Lin et al., 1997), leading to the presence of created biopolymer colloids (Radaideh et al., 2010). Hence, anaerobic digestion reduces the dewatering rate of sludge. In this study, the dewaterability of digestate was measured at the 70  end of each SRT period when the digesters were at the steady-state by a capillary suction timer at room temperature (21 ± 1oC). The CST results (in seconds) normalized by the TS concentrations in digested biosolids (Figure 4.6) showed that digesters fed with industrial TWAS (2) needed the lowest time in releasing its water, indicating the best dewaterability among different digester scenarios under both mesophilic and thermophilic conditions. Also, mixed sludge dewaterability was lower compared to digesters fed with dewatered municipal sludge cake only due to the presence of industrial TWAS. This could be caused by the presence of cellulose and polymers in the industrial TWAS stream. Organic polymers are widely used as sludge conditioners, improving dewaterability. These polymers generate less solid cake volume after dewatering (Lee and Liu, 2001). Furthermore, these results are in agreement with previous studies that observed better dewaterability from sludge generated in extended aerated biological treatment units, similar to one at BCTTP. Literature indicates that extended aeration sludge with low food to microorganism rations may produce better flocculated particles that result in smaller fraction of finer than anaerobically digested sludge (Radaideh et al., 2010). The SCOD results had the same pattern as dewatering. The presence of soluble inorganic materials interferes easily with the dewatering of digestates. These inorganic small particles had higher contact surface area, slowing the dewatering process. As is shown in Figure 4.7, higher SCOD content was present in the thermophilic digesters, specifically in digesters fed with diluted municipal sludge cake (1). It is well established in the literature that thermophilic digestates are harder to dewater due to the presence of small particles having a higher specific surface area (Lin et al., 1997). The results generated as part of this study were in agreement with the literature, consistently yielding in better dewaterability for the mesophilic digesters than those of thermophilic at both SRTs except the single digester fed with industrial TWAS (2) at SRT of 10 days. Overall, the results indicate that the addition of industrial TWAS to other waste streams can enhance the dewaterability by acting as a conditioner polymer.  71  Mesophilic  Thermophilic  Capillary suction time (s/g TS)  10000  1000  100  10  1 1  2  1+2  Single digestion  1+2+SC  1  Co-digestion  2  1+2  Single digestion  SRT = 20 d  1+2+SC  Co-digestion  SRT = 10 d  Figure 4.6 Dewaterability analysis results of single and co-digested samples (data represent the mean and error bars represent the standard deviation of 9 replicates, SRT: sludge retention time, TS: total solids)  SCOD present in digestate (mg/L)  Mesophilic  Thermophilic  7000 6000 5000 4000 3000 2000 1000 0 1  2  Single digestion  1+2  1+2+SC  Co-digestion  SRT = 20 d  1  2  Single digestion  1+2  1+2+SC  Co-digestion  SRT = 10 d  Figure 4.7 SCOD analysis results of single and co-digested samples (data represent the mean and error bars represent the standard deviation of 74 and 38 replicates for 20 and 10 days SRT, respectively, SRT: sludge retention time, SCOD: soluble chemical oxygen demand)  72  4.6.2  Pathogens  Biosolids are known to contain pathogens; therefore, digestates must be tested for the safety of both people and animals. According to OMRR (2008), Class A biosolids contain lower counts of fecal coliforms (<1,000 Most probable number or MPN fecal coliforms/g dry weight), meaning that they are higher quality biosolids with more liberal distribution allowance. Class B biosolids are allowed to contain more fecal coliforms (<2,000,000 MPN fecal coliforms/g dry weight). Therefore, Class B biosolids are subjected to more land application and distribution restrictions. Table 4.11 summarizes previous studies of coliform presents in different sources of digestates. Based on the source of the substrate, digestates may have higher or lower coliform content, an important factor for inactivation of pathogens. Also, temperature of treatment is another important factor for the decay rate of pathogens. Other critical factors of decay rate of pathogenic bacteria are: pH, VFA concentration, bacterial species, nutrients concentration, and treatment time (Salström, 2003). For anaerobic digestion, digester temperature and retention time are the factors that determine pathogen inactivation. The time required for pathogen inactivation is known as decimation reduction time. For many bacteria in thermophilic environment, their reduction time could be hours while for a mesophilic environment, the reduction time could be days (Salström, 2003). Since temperature helps to decrease the decimation reduction time, it is expected that the thermophilic digestates will contain lower coliforms. Table 4.11 shows that thermophilic digestions were the ones with lower coliform content in most of the previous studies. Overall the results from literature indicated that higher SRTs and elevated digester temperature lower pathogens concentrations in digested samples for land application.  73  Table 4.11 Summary of different substrates and digestion techniques with their total fecal coliform presence  Author  Aitken et al., 2005  Coelho et al., 2011  Type of feed Primary and waste activated  Type of digestion Anaerobic-  Jewell, 1982  SRT*  coliforms (MPN/g TS†)  6d  81.3-1905  Anaerobic-  20 d  >1×108  Primary sludge  mesophilic  10 d  >1×108  and activated  Anaerobic-2-  sludge  stage  20 d  <100  10 d  >1×104  sludge  thermophilic  thermophilic Kabrick &  Total fecal  Primary and waste activated sludge  Anaerobicmesophilic Aerobic-  1.1×104-2×106a 20 d 1×103-7×104a  thermophilic Anaerobic-  Rojas Oropeza  Municipal  mesophilic  et al., 2001  sludge  Anaerobic-  1×104-1×105 16 d <103  thermophilic Sahlström et al.,  Municipal  Anaerobic-  2004  sludge  mesophilic  20 d  174,463-35,258a  *SRT: Sludge retention time †MPN/100mL, SRT: sludge retention time, TS: total solids, MPN: most probable number a Total coliforms  This study had the same pattern, as it is shown in Figure 4.8, where mesophilic digesters had consistently higher total coliform content (8,838 to 37,959 MPN/g TS) compared to thermophilic digesters (41 to 1,090 MPN/g TS) at both SRT of 20 and 10 days. The lowest total coliform content (41 MPN/g TS) was in the thermophilic digester fed with the industrial TWAS (2), due to its source (free of human residuals). The coliform content in all the  74  mesophilic digestates were above the Class A biosolids; therefore, they could be classified as Class B biosolids (OMRR, 2008). For thermophilic digesters, except the digester fed with a mixture of 1+2+SC+L, all digestates could be qualified as Class A biosolids even at an SRT of 10 days. These results are in agreement with the literature indicating that an SRT of 10 days could provide adequate pathogen destruction under thermophilic temperatures (Salström, 2003). Furthermore, these coliform results confirmed that the mesophilic temperature of 35oC is not effective in pathogens reduction. Hence, a minimum of SRT for mesophilic should be 20 d (Salström et al., 2004). It is important to note that OMRR (2008) regulations are based on fecal coliform (associated with human or animal waste) and not total coliform content. However, in this study, the method used was able to quantify total coliforms as well as E. coli, part of the group of fecal coliforms. Thus, the assessment made based on the total coliforms, displayed in Figure 4.8, is conservative as fecal coliforms are expected to be lower than the total coliforms in digestate samples. If this point is taken into account, there is a higher level of confidence that regardless of the digestion scenario implemented at the full-scale, digested biosolids will be qualified either under Class A or Class B, therefore, will be suitable for land application.  75  Mesophilic  Thermophilic  2000000 MPN/g dry weight, Class B biosolids (OMRR 2008)  Total coliforms (MPN/g TS)  1000000 1000 MPN/g dry weight, Class A biosolids (OMRR 2008) 100000 10000 1000 100 10 1 1  2  Single digestion  1+2  1+2+SC  Co-digestion  SRT = 20 d  1  2  Single digestion  1+2  1+2+SC  Co-digestion  SRT = 10 d  Figure 4.8 Coliform content of effluents from anaerobic digesters, at 20 d and 10 d SRT with Class A limit regulation (data represent the mean and error bars represent the standard deviation of 8 replicates, SRT: sludge retention time, MPN: most probable number, TS: total solids)  4.7  Approximate cost functions for single and co-digestion treatment facilities  Planning municipal and industrial solid waste management systems requires quantitative estimates of capital and operational costs. Cost estimation for anaerobic digestion facility is complex and requires design by engineers from different disciplines (environmental, structural, mechanical and electrical). In order to evaluate the cost analysis, the facility is viewed as a system, consisting of components or subsystems (Tsilemou, 2002). Although cost analysis was initially not within the scope of this study, it was decided to attempt to calculate potential savings in both capital as well as long term (25 years) operational cost if City of Kelowna and Sun-Rype Beverage Ltd. decided to build a codigester utilizing all municipal and industrial streams. This was made possible by the capital  76  and operational cost functions suggested by Tsilemou and Panagiotakopoulus (2006) as a function of anaerobic digester design capacity. The cost functions are shown in Figure 4.9. A  B Operating cost (€/ton )  Initial cost (106 € )  0,5 0,4 0,3  y = 0,0342x0,55  0,2 R2= 0.92  0,1 0 0  50 100 Design capacity (103 tons/year)  10000 8000 6000 y = 16722x-0,61  4000  R2= 0.94  2000 0 0  150  50 100 150 Capacity (inflow 103 tons/yeat)  Figure 4.9 A) Initial and B) operating cost functions of anaerobic digestion facilities (adapted from Tsilemou and Panagiotakopoulus, 2006)  In this study, cost components such as facility size, inflowing waste composition, operational conditions, number of employees, quantities of recovered material, compost and energy, recovery coefficients, number and size of equipment units, land area, among other parameters, are studied for different solid waste management systems, including anaerobic digestion (Tsilemou and Panagiotakopoulus, 2006). Assumptions made by Tsilemou and Panagiotakopoulus (2006) for cost functions were as follows. Cost functions were based on thermophilic dry one-stage digestion. Digesters receive source-separated biodegradable waste (i.e. source-separated municipal solids waste, bio-waste with sludge, bio-waste mixed with garden waste or food industry waste. Initial  (capital  environmental  cost)  includes  assessment,  predevelopment  hydrogeological  costs  (site  investigation,  characterization, land  acquisition,  engineering design) + construction costs (land cleaning, excavation, buildings/other construction works), equipment and furnishing of facilities, technical equipment for waste transport and energy recovery, connecting networks (access roads, water & energy supply, sewerage system).  77  Operating cost includes expenses for raw materials, laboratory tests (reagent, chemicals, etc.), energy and other utilities, wastewater disposal, labor, supervision, maintenance, insurance, overheads, training programs. The operating cost does include capital recovery cost via biogas or fertilizer. The results are displayed in Table 4.12. Methane production was calculated based on experimental methane yield obtained in this study (L/g VSadded, Table 4.6). Preliminary cost analysis results indicated an overall saving of $10.52 million ($2 million in capital and $8.52 million in operational) over 25 years period for co-digestion scenario utilizing all waste streams over building/operating two separate digesters for municipal and industrial waste streams. In addition, the, unit operation cost ($/ton) for only industrial TWAS +SC will be almost 5 times ($272.02 to $54.29, respectively) higher than the co-digester utilizing all the waste streams due to much lower digester capacity utilizing the industrial streams. Therefore, the results from this study confirm that co-digestion has lower unit cost due to sharing of facility and operation. It is important to emphasize that due to the cost functions based on European sites, it is expected that the capital and operational costs will vary for Canada. For anaerobic digesters, the cost is influenced by the pretreatment/characteristics of waste, volume and quality (energy content) of biogas that are determined by regulations in different countries. Therefore it is difficult to estimate the uncertainty of using European cost functions in the cost analysis for the Canadian waste treatment sector.  78  Table 4.12 Estimated cost items for single and co-digestion reactors* Single digesters  Co-digesters  Two single digesters (one for municipal sludge cake and one for industrial TWAS combined with SC)  Sludge cake  Industrial TWAS*  Industrial SC  Industrial TWAS + SC  Sludge cake + TWAS  Sludge cake + TWAS + SC  60.0  25.5  0.14  25.6  85.50  85.6  17.4  2.8  21.0  2.9  13.1  13.1  10.44  0.71  0.03  0.74  11.15  11.21  15.0  2.4  19.0  2.5  11.2  11.23  9.00  0.61  0.03  0.64  9.61  9.64  (9.00) + (0.64)  3,214  218  9.5  228  3,433  3,442  (3,214) + (228)  722,700  35,741  not tested  not tested  806,927  879,522  19,053 10.24 54.29  1,303 2.34 278.83  1,357 2.39 272.02  20,356 10.62 52.14  20,410 10.63 52.06  (19,053) + (1,357) (10.24) + (2.39) = 12.63  Operating cost (million $/year)  1.03  0.36  0.37  1.06  1.06  (1.03) + (0.37) = 1.4  Total operating cost (25 years, million $)  25.85  9.08  9.23  26.53  26.56  (25.85)+ (9.23)= 35.08  Total capital & operating cost (25 years, million $)  36.10  11.42  11.62  37.15  37.19  (36.10) + (11.62) = 47.72  Gas purification (million $)² optional  1.5  1.5  1.5  1.5  1.5  Sludge production rate (wet ton/d) Total solids (%, w/w) Total solids produced (dry ton/d) Volatile solids (%, w/w) Volatile solids produced (dry ton/d) Digester volume† (m3) Annual CH4 production (m3/year)a Design capacity (ton/year) Capital cost (million $)c Unit operation cost ($/ton)c  85.6  (10.44) + (0.74)  79  Sludge cake  Industrial TWAS*  Industrial SC  Industrial TWAS + SC  Sludge cake + TWAS  Sludge cake + TWAS + SC  Two single digesters (one for municipal sludge cake and one for industrial TWAS combined with SC)  Revenue calculated from digestate to be sold as Ogogrow© fertilizer Annual Ogogrow 11,677.63 1,491.06 12,634.52 12,175.63 production (wet ton/year) Revenue gained ($/year)2 346, 479 44,240 374,870 361,255 Revenue gained (25 yrs., 8.66 1.11 9.37 9.03 million $) Revenue calculated from biogas assuming biogas is purified to bio-methane quality (96% methane) 24,692 1,221 27,570 30,049 Energy (GJ/year) 3 11 11 11 11 Energy value ($/GJ) Revenue gained ($/year) 271,610 13,432 303,265 330,548 287,378 Revenue gained (25 yrs., 6.79 0.34 7.58 8.26 7.18 million $) Revenue calculated from biogas generation assuming biogas is NOT purified to bio-methane quality (60-70% methane) 24,692 1,221 27,570 30,049 Energy (GJ/year) 2.5 2.5 2.5 2.5 Energy value ($/GJ)3 Revenue gained ($/year) 61,729 3,053 68,924 75,124 65.313 Revenue gained (25 yrs., 1.54 0.08 1.72 1.88 1.63 million $) *TWAS: thickened waste activated sludge, SC: screen cake, TS: total solids, VS: volatile solids, SRT: sludge retention time †Digester volume is calculated based on organic loading rate (OLR) of 2.80 kg VS/m3 × day a Based on the experimental specific methane yields obtained in Table 4.15 for thermophilic digesters at SRT of 20 days c Digester capital and operational cost functions are based on Tsilemou and Panagiotakopoulus (2006). Currency conversion rate: 1.3249 CAD/Euro (March 26th, 2013) 2 Ogogrow selling price of $13.5 per cubic yard at total solid concentration of 20-30% by weight (City of Kelowna, 2013) 3 Personal communication (Fortis BC, 2013)  80  Chapter 5: Conclusions and recommendations 5.1  Conclusions  This research explored the potential of using co-digestion for sewage sludge cake, fruit juice thickened waste activated sludge and screen cake, diluted with landfill leachate. The study started with acclimation of mesophilic and thermophilic inocula to a mixture of waste streams. Upon achieving steady state during acclimation phase, eight lab-scale digesters were set-up with acclimatized inocula to assess performances from different single and codigestion scenarios. Total duration of digestion studies was 7 months. Upon experimental work, organic loading rates and methane yields obtained were used to calculate full-scale digester volumes and revenue to be generated from methane recovered from waste streams. Based on the experimental data and analysis, the following conclusions were drawn: 1. Among the single digestion scenarios, fruit-juice TWAS achieved the lowest biodegradation efficiency, and therefore lowest methane yield due to higher level of refractory compounds present. This was highly likely linked to the extended aeration (long SRT & Hydraulic retention time) operation regime of the activated sludge process at BCTTP. 2. Specific biogas yields from waste streams were close or higher than literature values reported for similar substrates (~1 L/ g VS removed). All single and co-digestion scenarios achieved steady state at SRTs of 20 and 10 days, corresponding to OLRs of 1.41-4.38 g COD/L × d, except for the fruit-juice TWAS. The steady state was achieved after 15 and 5 days of operation, for 20 and 10 days SRT, respectively. SRT is fixed value for a certain operation condition. At an SRT of 10 days, the biogas production from TWAS digesters started declining after 20 days of digestion at both mesophilic and thermophilic temperatures. 3. On the other hand, addition of municipal sludge cake and particularly landfill leachate to fruit-juice waste streams enhanced the co-digestion due to additional buffering capacity and less refractory organics provided by landfill leachate and municipal sludge cake, respectively. Due to this feature, co-digestion digesters were stable even at the higher organic loadings without accumulation of VFA leading to pH drop.  81  4. Single and co-digestion scenarios presented statistically significant differences (p < 0.05 for TS and p ≤ 0.05 for VS removals, respectively), suggesting that co-digestion has a better performance than the single digestion in terms of solid removal efficiencies. However, the effects of digestion temperature (mesophilic or thermophilic) and SRT (20-d or 10-d) were not significantly different. 5. Thermophilic digesters yielded total ammonia concentrations higher than the maximum limit to release toxic free ammonia of 100 mg/L at corresponding reactor pH and temperature. However, thermophilic digester did not experience any inhibition possibly due to adequate acclimation period. 6. Despite the low biodegradability, fruit-juice TWAS indicated the fastest dewaterability, therefore enhanced the dewaterability of digestates from co-digesters utilizing mixture of municipal/industrial streams. These results are in agreement with previous studies that observed better dewaterability from sludge generated in extended aerated biological treatment units, similar to one at BCTTP. 7. According to OMRR of BC, all mesophilic digestate coliform concentrations were under Class B biosolids limits. However, all thermophilic digestates could be categorized under Class A biosolids. 8. Preliminary cost analysis indicated an overall saving of $10.52 million ($2 million in capital and $8.52 million in operational) over 25 years period for co-digestion scenario utilizing all waste streams over building/operating two separate digesters for municipal and industrial waste streams. Therefore, the results from this study confirm that co-digestion has lower unit cost due to sharing of facility and operation.  5.2  Recommendations for future work  To verify the conclusions presented in this study, it is recommended that the following additional research be undertaken in the future: 1. Application of pretreatment methods such as ultrasound, alkaline, microwave, before anaerobic digestion can be tested to increase the degradation of waste-streams.  82  2. In this study, metal concentrations in digestate samples were calculated based on the data provided by the City of Kelowna and BCTTP for the influent waste streams. It is recommended that these concentrations are experimentally verified. 3. Due to seasonal variation in the industrial waste streams, it is recommended to verify the biogas and methane yields obtained from this study (performed during spring and fall months) with future set of digesters utilizing waste sampled during winter months. 4. Concentration of H2S in the biogas should be measured to assess the suitability of the biogas for energy utilization and risk of corrosion for the biogas recovery system. 5. 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Available  from:  http://www.epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory2011-Complete_Report.pdf [cited on 20 February 2012]  94  Appendices Appendix A: Calibration curves  Air volume in manometer (mL)  450 400 350 300  y = 0,8051x + 0,8204 R² = 0,9999  250 200  Volume  150  Lineal (Volume)  100 50 0 0  100  200 300 400 Injected air volume(mL)  500  600  Figure A.1 Calibration curve for biogas measurement via manometer (STP) 0,6  Concentration (mg/L)  0,5 0,4 y = 0,0007x R² = 0,9998  0,3  COD Lineal (COD)  0,2 0,1 0 0  200  400 600 Absorbance (600nm)  800  Figure A.2 Calibration curve for COD determination  95  NH3 probe reading (mV)  Concentration (lnC, mg/L)  0 0  2  4  6  -50  8 y = -24,038x - 26,609 R² = 0,9999 Ammonia  -100  Lineal (Ammonia)  -150 -200 -250  Figure A.3 Calibration curve for ammonia (NH3-N) determination  Absorbance at 420nm  2,5 2 1,5  y = 0,0136x R² = 0,9908  1  Series1 Lineal (Series1)  0,5 0 0  50 100 150 concentration of TN (mg/L)  200  Figure A.4 Calibration curve for total nitrogen (TN) determination  96  Appendix B: Results summary of digesters fed with leachate  Table B.1 Results for semi-continuous digesters at 20d SRT Parameter  Mesophilic  Thermophilic  25 ± 13†  23 ± 9  TS (%w/w)  99 ± 24*  97 ± 21*  VS (%w/w)  54 ± 21*  52 ± 6*  TCOD (mg/L)  6,566 ± 3105  7,041 ± 3392  SCOD (mg/L)  1,108 ± 735  1,593 ± 659  CH4 (%)  33 ± 6  32 ± 2  pH  7.8 ± 0.1  8.3 ± 0.2  Ammonia (mg/L)  588 ± 361  726 ± 430  Alkalinity (mg CaCO3/L)  3,725 ± 399  4,106 ± 563  TVFA  2.4 ± 0.3  12.5 ± 0.2  Daily biogas production (mL/d)  *Total and volatile solids majority content were coming from inoculum. TS: total solids, VS: volatile solids, TCOD: Total chemical oxygen demand, SCOD: soluble chemical oxygen demand, TVFA: total volatile fatty acids † Data represent the arithmetic mean of minimum of duplicates for loading rates and 20 replicates for the remaining parameters collected during steady state (standard deviation)  97  Appendix C: ANOVA Analyses C.1  TS % removal efficiency  Table C.1.1 TS% removal ANOVA analyses results for temperature and sludge retention time Scenarios  Mesophilic  Thermophilic  1 (20-d)  36.75 ± 4.18  39.06 ± 5.78  2 (20-d)  27.66 ± 3.94  33.25 ± 5.77  1+2+L (20-d)  40.42 ± 6.71  40.95 ± 4.28  1+2+SC+L (20-d)  40.03 ± 3.66  43.21 ± 3.16  1 (10-d)  38.56 ± 4.12  42.02 ± 4.38  2 (10-d)  29.67 ± 4.13  39.78 ± 4.58  1+2+L (10-d)  42.28 ± 5.02  40.57 ± 3.59  1+2+SC+L (10-d)  43.71 ± 6.80  40.69 ± 3.55  Table C.1.2 ANOVA: two-factor with replication TS% removal results for temperature and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 136.43 34.11 101.11  4 149.59 37.40 56.91  8 286.02 35.75 70.82  Count Sum Average Variance  4 148.09 37.02 85.65  4 163.06 40.76 0.87  8 311.14 38.89 41.08  Count Sum Average Variance  8 284.51 35.56 82.46  8 312.65 39.08 27.99  98  Table C.1.3 ANOVA analysis TS% removal results for temperature and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  39.44  1  39.44  0.65  0.44  4.75  Columns  49.48  1  49.48  0.81  0.39  4.75  Interaction  0.20  1  0.20  0.003  0.95  4.75  Within  733.59  12  61.13  Total  822.72  15  Table C.1.4 TS% removal ANOVA analyses results for sludge retention time and temperature Scenarios  20-d  10-d  M-1  36.75 ± 4.18  38.56 ± 4.12  M-2  27.66 ± 3.94  29.67 ± 4.13  M-1+2+L  40.42 ± 6.71  42.28 ± 5.02  M-1+2+SC+L  40.03 ± 3.66  43.71 ± 6.80  T-1  39.06 ± 5.78  42.02 ± 4.38  T-2  33.25 ± 5.77  39.78 ± 4.58  T-1+2+L  40.95 ± 4.28  40.57 ± 3.59  T-1+2+SC+L  43.21 ± 3.16  40.69 ± 3.55  Table C.1.5 ANOVA: two-factor with replication TS% removal results for sludge retention time and temperature Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 136.43 34.11 101.11  4 148.09 37.02 85.65  8 284.51 35.56 82.46  Count Sum Average Variance  4 149.59 37.40 56.91  4 163.06 40.76 0.87  8 312.65 39.08 28.00  Count Sum Average Variance  8 286.02 35.75 70.82  8 311.14 38.89 41.08  99  Table C.1.6 ANOVA analysis removal results for sludge retention time and temperature Source of variation  SS  df  MS  F  P-value  F-critic  Sample  49.48  1  49.48  0.81  0.39  4.75  Columns  39.44  1  39.44  0.65  0.43  4.75  Interaction  0.20  1  0.20  0.003  0.95  4.75  Within  733.59  12  Total  822.72  15  Table C.1.7 TS% removal ANOVA analyses results for single to co-digestion, and sludge retention time Scenarios  Single  Co-digestion  M-1 / M-1+2 +L (20-d)  36.75 ± 4.18  40.42 ± 6.71  M-2 / M-1+2+SC+L (20-d)  27.66 ± 3.94  40.03 ± 3.66  T-1 / T-1+2+L (20-d)  39.06 ± 5.78  40.95 ± 4.28  T-2 / T-1+2+SC+L (20-d)  33.25 ± 5.77  43.21 ± 3.16  M-1 / M-1+2 +L (10-d)  38.56 ± 4.12  42.28 ± 5.02  M-2 / M-1+2+SC+L (10-d)  29.67 ± 4.13  43.71 ± 6.80  T-1 / T-1+2+L (10-d)  42.02 ± 4.38  40.57 ± 3.59  T-2 / T-1+2+SC+L (10-d)  39.78 ± 4.58  40.69 ± 3.55  Table C.1.8 ANOVA: two-factor with replication TS% removal results for single to codigestion, and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 121.41 30.35 85.47  4 164.61 41.15 2.03  8 286.02 35.75 70.82  Count Sum Average Variance  4 143.89 35.97 70.89  4 167.25 41.81 2.22  8 311.14 38.89 41.08  Count Sum Average Variance  8 265.30 33.16 76.03  8 331.86 41.48 1.95  100  Table C.2 ANOVA analysis removal results for single to co-digestion, and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  39.44  1  39.44  0.98  0.34  4.75  Columns  276.90  1  276.90  6.90  0.02  4.75  Interaction  24.57  1  24.57  0.61  0.45  4.75  Within  481.80  12  40.15  Total  822.72  15  101  C.2  VS % removal efficiency  Table C.2.1 VS% removal ANOVA analyses results for temperature and sludge retention time Scenarios  Mesophilic  Thermophilic  1 (20-d)  43.01 ± 2.26  46.62 ± 3.64  2 (20-d)  36.81 ± 6.80  41.04 ± 5.25  1+2+L (20-d)  50.21 ± 2.64  51.02 ± 4.12  1+2+SC+L (20-d)  44.20 ± 4.41  49.22 ± 2.60  1 (10-d)  47.39 ± 3.67  49.07 ± 4.29  2 (10-d)  39.05 ± 6.35  40.96 ± 5.57  1+2+L (10-d)  47.32 ± 3.00  48.25 ± 2.27  1+2+SC+L (10-d)  46.28 ± 2.82  47.24 ± 4.31  Table C.2.2 ANOVA: two-factor with replication VS% removal results for temperature and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 159.24 39.81 153.85  4 177.90 44.47 83.46  8 337.14 42.14 107.92  Count Sum Average Variance  4 175.04 43.76 42.13  4 195.52 48.88 2.48  8 370.57 46.32 26.61  Count Sum Average Variance  8 334.28 41.78 88.45  8 373.42 46.68 42.38  102  Table C.2.3 ANOVA analysis VS% removal results for temperature and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  69.83  1  69.83  0.99  0.34  4.75  Columns  95.74  1  95.74  1.36  0.27  4.75  Interaction  0.21  1  0.21  0.003  0.95  4.75  Within  845.77  12  70.48  Total  1011.55  15  Table C.2.4 VS% removal ANOVA analyses results for sludge retention time and temperature Scenarios  20-d  10-d  M-1  43.01 ± 2.26  47.39 ± 3.67  M-2  36.81 ± 6.80  39.05 ± 6.35  M-1+2+L  50.21 ± 2.64  47.32 ± 3.00  M-1+2+SC+L  44.20 ± 4.41  46.28 ± 2.82  T-1  46.62 ± 3.64  49.07 ± 4.29  T-2  41.04 ± 5.25  40.96 ± 5.57  T-1+2+L  51.02 ± 4.12  48.25 ± 2.27  T-1+2+SC+L  49.22 ± 2.60  47.24 ± 4.31  Table C.2.5 ANOVA: two-factor with replication VS% removal results for sludge retention time and temperature Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 159.24 39.81 153.85  4 175.04 43.76 42.13  8 334.28 41.79 88.45  Count Sum Average Variance  4 177.90 44.47 83.46  4 195.52 48.88 2.48  8 373.42 46.68 42.38  Count Sum Average Variance  8 337.14 42.14 107.92  8 370.57 46.32 26.61  103  Table C.2.6 ANOVA analysis results for sludge retention time and temperature Source of variation  SS  df  MS  F  P-value  F-critic  Sample  95.74  1  95.74  1.36  0.27  4.75  Columns  69.83  1  69.83  0.99  0.34  4.75  Interaction  0.21  1  0.21  0.003  0.95  4.75  Within  845.77  12  70.48  Total  1011.55  15  Table C.2.7 VS% removal ANOVA analyses results for single to co-digestion, and sludge retention time Scenarios  Single  Co-digestion  M-1 / M-1+2 +L (20-d)  43.01 ± 2.26  50.21 ± 2.64  M-2 / M-1+2+SC+L (20-d)  36.81 ± 6.80  44.20 ± 4.41  T-1 / T-1+2+L (20-d)  46.62 ± 3.64  51.02 ± 4.12  T-2 / T-1+2+SC+L (20-d)  41.04 ± 5.25  49.22 ± 2.60  M-1 / M-1+2 +L (10-d)  47.39 ± 3.67  47.32 ± 3.00  M-2 / M-1+2+SC+L (10-d)  39.05 ± 6.35  46.28 ± 2.82  T-1 / T-1+2+L (10-d)  49.07 ± 4.29  48.25 ± 2.27  T-2 / T-1+2+SC+L (10-d)  40.96 ± 5.57  47.24 ± 4.31  Table C.2.8 ANOVA: two-factor with replication VS% removal results for single to codigestion, and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 142.49 35.62 129.06  4 188.01 47.00 6.25  8 330.50 41.31 94.99  Count Sum Average Variance  4 181.47 45.37 59.02  4 195.73 48.93 2.59  8 377.20 47.15 30.03  Count Sum Average Variance  8 323.96 40.49 107.74  8 383.74 47.97 4.85  104  Table C.2.9 ANOVA analysis results for single to co-digestion, and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  136.31  1  136.31  2.77  0.12  4.75  Columns  223.39  1  223.39  4.54  0.05  4.75  Interaction  61.07  1  61.07  1.24  0.29  4.75  Within  590.77  12  49.23  Total  1011.55  15  105  C.3  TCOD % removal efficiency  Table C.3.1 TCOD% removal ANOVA analyses results for temperature and sludge retention time Scenarios  Mesophilic  Thermophilic  1 (20-d)  54.89 ± 4.58  58.06 ± 4.93  2 (20-d)  50.49± 14.13  55.57 ± 10.79  1+2+L (20-d)  56.58 ± 7.58  58.51 ± 6.81  1+2+SC+L (20-d)  58.54 ± 10.22  61.27 ± 7.94  1 (10-d)  45.95 ± 7.21  42.67 ± 5.01  2 (10-d)  31.62 ± 7.29  40.45 ± 10.07  1+2+L (10-d)  50.34 ± 3.34  46.90 ± 9.13  1+2+SC+L (10-d)  57.43 ± 4.38  50.76 ± 5.84  Table C.3.2 ANOVA: two-factor with replication TCOD% removal results for temperature and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 220.50 55.13 11.79  4 233.41 58.35 5.45  8 453.91 56.74 10.37  Count Sum Average Variance  4 185.34 46.34 118.64  4 180.78 45.19 20.92  8 366.12 45.76 60.18  Count Sum Average Variance  8 405.84 50.73 77.98  8 414.19 51.77 60.77  106  Table C.3.3 ANOVA analysis TCOD% results for temperature and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  481.76  1  481.76  12.29  0.004  4.75  Columns  4.35  1  4.35  0.11  0.74  4.75  Interaction  19.08  1  19.08  0.49  0.49  4.75  Within  470.41  12  39.20  Total  975.61  15  Table C.3.4 TCOD% removal ANOVA analyses results for sludge retention time and temperature Scenarios  20-d  10-d  M-1  54.89 ± 4.58  45.95 ± 7.21  M-2  50.49± 14.13  31.62 ± 7.29  M-1+2+L  56.58 ± 7.58  50.34 ± 3.34  M-1+2+SC+L  58.54 ± 10.22  57.43 ± 4.38  T-1  58.06 ± 4.93  42.67 ± 5.01  T-2  55.57 ± 10.79  40.45 ± 10.07  T-1+2+L  58.51 ± 6.81  46.90 ± 9.13  T-1+2+SC+L  61.27 ± 7.94  50.76 ± 5.84  Table C.3.5 ANOVA: two-factor with replication TCOD% results for sludge retention time and temperature Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 220.50 55.13 11.79  4 185.34 46.33 118.64  8 405.84 50.73 77.98  Count Sum Average Variance  4 233.41 58.35 5.45  4 180.78 45.19 20.92  8 414.19 51.77 60.77  Count Sum Average Variance  8 453.91 56.74 10.37  8 366.12 45.76 60.18  107  Table C.3.6 ANOVA analysis results for sludge retention time and temperature Source of variation  SS  df  MS  F  P-value  F-critic  Sample  4.35  1  4.35  0.11  0.74  4.75  Columns  481.76  1  481.76  12.29  0.004  4.75  Interaction  19.08  1  19.08  0.49  0.49  4.75  Within  470.41  12  39.20  Total  975.61  15  Table C.3.7 TCOD% removal ANOVA analyses results for single to co-digestion, and sludge retention time Scenarios  Single  Co-digestion  M-1 / M-1+2 +L (20-d)  54.89 ± 4.58  56.58 ± 7.58  M-2 / M-1+2+SC+L (20-d)  50.49± 14.13  58.54 ± 10.22  T-1 / T-1+2+L (20-d)  58.06 ± 4.93  58.51 ± 6.81  T-2 / T-1+2+SC+L (20-d)  55.57 ± 10.79  61.27 ± 7.94  M-1 / M-1+2 +L (10-d)  45.95 ± 7.21  50.34 ± 3.34  M-2 / M-1+2+SC+L (10-d)  31.62 ± 7.29  57.43 ± 4.38  T-1 / T-1+2+L (10-d)  42.67 ± 5.01  46.90 ± 9.13  T-2 / T-1+2+SC+L (10-d)  40.45 ± 10.07  50.76 ± 5.84  Table C.3.8 ANOVA: two-factor with replication TCOD% results for single to co-digestion, and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 182.95 45.74 101.95  4 222.89 55.72 13.51  8 405.84 50.73 77.98  Count Sum Average Variance  4 196.75 49.19 79.44  4 217.44 54.36 44.53  8 414.19 51.77 60.77  Count Sum Average Variance  8 379.70 47.46 81.14  8 440. 55.04 25.41  108  Table C.3.9 ANOVA analysis results for single to co-digestion, and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  4.35  1  4.35  0.07  0.79  4.75  Columns  229.79  1  229.79  3.84  0.07  4.75  Interaction  23.18  1  23.18  0.39  0.54  4.75  Within  718.29  12  59.86  Total  975.61  15  109  C.4  Methane % Table C.4.1 CH4% ANOVA analyses results for temperature and sludge retention time Scenarios  Mesophilic  Thermophilic  1 (20-d)  66.82 ± 1.79  62.42 ± 2.12  2 (20-d)  63.02 ± 2.59  67.48 ± 2.59  1+2+L (20-d)  66.43 ± 3.90  62.62 ± 10.82  1+2+SC+L (20-d)  66.30 ± 4.86  66.02 ± 0.58  1 (10-d)  68.94 ± 2.36  69.82 ± 5.04  2 (10-d)  64.52 ± 1.61  67.74 ± 3.71  1+2+L (10-d)  68.00 ± 1.35  67.54 ± 1.30  1+2+SC+L (10-d)  69.09 ± 1.23  65.65 ± 1.96  Table C.4.2 ANOVA: two-factor with replication CH4%results for temperature and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 262.57 65.64 3.10  4 258.55 64.64 6.33  8 521.12 65.14 4.33  Count Sum Average Variance  4 270.54 67.64 4.55  4 270.75 67.69 2.89  8 541.29 67.66 3.19  Count Sum Average Variance  8 533.12 66.64 4.42  8 529.30 66.16 6.61  110  Table C.4.3 ANOVA analysis CH4% results for temperature and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  25.43  1  25.43  6.02  0.03  4.75  Columns  0.91  1  0.91  0.22  0.65  4.75  Interaction  1.11  1  1.11  0.26  0.62  4.75  Within  50.65  12  4.22  Total  78.10  15  Table C.4.4 CH4% ANOVA analyses results for sludge retention time and temperature Scenarios  20-d  10-d  M-1  66.82 ± 1.79  68.94 ± 2.36  M-2  63.02 ± 2.59  64.52 ± 1.61  M-1+2+L  66.43 ± 3.90  68.00 ± 1.35  M-1+2+SC+L  66.30 ± 4.86  69.09 ± 1.23  T-1  62.42 ± 2.12  69.82 ± 5.04  T-2  67.48 ± 2.59  67.74 ± 3.71  T-1+2+L  62.62 ± 10.82  67.54 ± 1.30  T-1+2+SC+L  66.02 ± 0.58  65.65 ± 1.96  Table C.4.5 ANOVA: two-factor with replication CH4% results for sludge retention time and temperature Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 262.57 65.64 3.10  4 270.54 67.64 4.55  8 533.12 66.64 4.42  Count Sum Average Variance  4 258.55 64.64 6.33  4 270.75 67.69 2.90  8 529.30 66.16 6.61  Count Sum Average Variance  8 521.12 65.14 4.33  8 541.29 67.66 3.19  111  Table C.4.6 ANOVA analysis results for sludge retention time and temperature Source of variation  SS  df  MS  F  P-value  F-critic  Sample  0.91  1  0.91  0.22  0.65  4.75  Columns  25.43  1  25.43  6.02  0.03  4.75  Interaction  1.12  1  1.12  0.26  0.62  4.75  Within  50.65  12  4.22  Total  78.10  15  Table C.4.7 CH4%ANOVA analyses results for single to co-digestion, and sludge retention time Scenarios  Single  Co-digestion  M-1 / M-1+2 +L (20-d)  66.82 ± 1.79  66.43 ± 3.90  M-2 / M-1+2+SC+L (20-d)  63.02 ± 2.59  66.30 ± 4.86  T-1 / T-1+2+L (20-d)  62.42 ± 2.12  62.62 ± 10.82  T-2 / T-1+2+SC+L (20-d)  67.48 ± 2.59  66.02 ± 0.58  M-1 / M-1+2 +L (10-d)  68.94 ± 2.36  68.00 ± 1.35  M-2 / M-1+2+SC+L (10-d)  64.52 ± 1.61  69.09 ± 1.23  T-1 / T-1+2+L (10-d)  69.82 ± 5.04  67.54 ± 1.30  T-2 / T-1+2+SC+L (10-d)  67.74 ± 3.71  65.65 ± 1.96  Table C.4.8 ANOVA: two-factor with replication CH4% results for single to co-digestion, and sludge retention time Summary  Mesophilic  Thermophilic  Total  Count Sum Average Variance  4 259.74 64.94 6.67  4 261.38 65.35 3.32  8 521.12 65.14 4.33  Count Sum Average Variance  4 271.01 67.75 5.38  4 270.28 67.57 2.05  8 541.29 67.66 3.19  Count Sum Average Variance  8 530.75 66.34 7.43  8 531.66 66.46 3.71  112  Table C.4.9 ANOVA analysis results for single to co-digestion, and sludge retention time Source of variation  SS  df  MS  F  P-value  F-critic  Sample  25.43  1  25.43  5.84  0.03  4.75  Columns  0.05  1  0.05  0.01  0.91  4.75  Interaction  0.35  1  0.35  0.08  0.78  4.75  Within  52.27  12  4.36  Total  78.10  15  113  Appendix D: Heavy metals in substrates Table D.1 Comparison of OMRR heavy metals criteria with calculated concentration for single and co-digested thermophilic effluents at 10-d SRT Influenta Class A  Class B  biosolids*  biosolids*  1  2†  1+2+L  Effluent 1+2+SC+ L  1  2  1+2+L  1+2+SC+L  Results (mg/kg dry weight) Aluminum  n/r  n/r  918.39  0  796.17  794.17  2,185.37  0  1,962.74  1,951.60  Antimony  n/r  n/r  0.38  0  0.79  0.79  0.90  0  1.94  1.94  Arsenic  75  75  0.36  0.70  2.15  2.15  0.85  1.76  5.29  5.27  Barium  n/r  n/r  31.95  0  67.31  67.26  76.02  0  165.94  165.28  Beryllium  n/r  n/r  0.01  0  0.01  0.01  0.02  0  0.03  0.03  Bismuth  n/r  n/r  4.05  0  3.62  3.61  9.63  0  8.93  8.88  Cadmium  20  20  0.20  1.10  0.29  0.28  0.47  2.76  0.70  0.70  Calcium  n/r  n/r  2250.88  0  32,325.43  32,332.89  5,356.13  0  79,692.26  79,454.66  1,060²  1,060  3.17  14.90  9.91  9.90  7.54  37.46  24.43  24.33  Cobalt  150  150  0.46  0.60  1.49  1.49  1.10  1.51  3.67  3.65  Copper  2,200²  2,200  134.22  46.40  144.16  143.87  319.39  116.65  355.41  353.56  Iron  n/r  n/r  831.16  0  781.63  779.87  1977.80  0  1,926.97  1,916.46  Lead  500  500  2.89  2  3.13  3.13  6.89  5.03  7.72  7.68  Lithium  n/r  n/r  0.49  0  5.68  5.68  1.17  0  14.00  13.96  Magnesium  n/r  n/r  1,197.75  0  32,057.58  32,067.56  2,850.12  0  79,031.93  78,802.65  Chromium  114  1  2†  1+2+L  1+2+SC+L  1  2  1+2+L  1+2+SC+L  Results (mg/kg dry weight) Manganese  n/r  n/r  23.73  0  90.99  90.97  56.47  0  224.32  223.54  Mercury  5  15  0.12  0.05  0.11  0.11  0.30  0.13  0.28  0.28  Molybdenum  20  20  1.46  4  1.82  1.82  3.48  10.06  4.51  4.48  Nickel  180  180  2.34  8.30  5.27  5.27  5.57  20.87  13.02  12.96  Phosphorus  n/r  n/r  5,019.75  0  4,537.93  4,537.93  11,944.85  0  11,213.77  11,151.48  Potassium  n/r  n/r  1,490.94  0  18,597.21  18,597.21  3,547.79  0  45,838.53  45,700.66  Selenium  14  14  0.71  1.00  1.22  1.22  1.68  2.51  3.01  3.00  Silver  n/r  n/r  0.58  0  0.50  0.50  1.38  0  1.24  1.24  Sodium  n/r  n/r  130.05  0  130,874.3  130,926.9  309.46  0  322,645.9  321,739.13  Strontium  n/r  n/r  17.57  0  849.73  850.03  41.81  0  2,094.85  2,088.86  Thallium  n/r  n/r  0  0  0  0  0.01  0  0.01  0.01  Tin  n/r  n/r  2.71  0  2.49  2.49  6.46  0  6.15  6.12  Titanium  n/r  n/r  9.91  0  13.42  13.40  23.59  0  33.09  32.94  Uranium  n/r  n/r  1.74  0  1.96  1.96  4.15  0  4.84  4.82  Vanadium  n/r  n/r  1.24  0  3.58  3.58  2.95  0  8.83  8.80  1,850  1,850  66.05  51.00  67.33  67.18  157.18  128.22  166.00  165.09  n/r  n/r  1.49  0  3.20  3.20  3.56  0  7.89  7.86  Zinc Zirconium  *OMRR (2008) a Analysis made in CARO commercial laboratories (Kelowna, BC) †SunRype internal report: Brandt’s Creek Biosolids Analysis, November 2009, TWAS: thickened waste activated sludge  ²Although not specified in OMRR (2008), should be lower than the Class B limits (BC Ministry of Environ., personal communication) 115  Table D.2 Comparison of OMRR heavy metals criteria with calculated concentration for single and co-digested mesophilic effluents at 10d SRT Influenta Class A  Class B  biosolids*  biosolids*  1  2†  1+2+L  Effluent 1+2+SC+L  1  2  1+2+L  1+2+SC+L  Results (mg/kg dry weight) Aluminum  n/r  n/r  918.39  0  796.17  794.17  2,381.70  0  1,882.87  1,816.72  Antimony  n/r  n/r  0.38  0  0.79  0.79  0.98  0  1.86  1.80  Arsenic  75  75  0.36  0.70  2.15  2.15  0.92  2.98  5.07  4.91  Barium  n/r  n/r  31.95  0  67.31  67.26  82.85  0  159.19  153.86  Beryllium  n/r  n/r  0.01  0  0.01  0.01  0.03  0  0.03  0.03  Bismuth  n/r  n/r  4.05  0  3.62  3.61  10.50  0  8.57  8.27  Cadmium  20  20  0.20  1.10  0.29  0.28  0.51  4.68  0.67  0.65  Calcium  n/r  n/r  2,250.88  0  32,325.43  32,332.89  5,837.34  0  23.44  73,963.34  0  1060  3.17  14.90  9.91  9.90  8.22  63.33  76,449.46  22.65  Cobalt  150  150  0.46  0.60  1.49  1.49  1.20  2.55  3.52  3.40  Copper  0  2200  134.22  46.40  144.16  143.87  348.09  197.22  340.95  329.12  Iron  n/r  n/r  831.16  0  781.63  779.87  2,155.49  0  1,848.56  1,784.01  Lead  500  500  2.89  2  3.13  3.13  7.51  8.50  7.41  7.15  Lithium  n/r  n/r  0.49  0  5.68  5.68  1.27  0  13.43  12.99  Magnesium  n/r  n/r  1197.75  0  32,057.58  32,067.56  3,106.18  0  75,816.00  73,356.39  Manganese  n/r  n/r  23.73  0  90.99  90.97  61.55  0  215.19  208.09  5  15  0.12  0.05  0.11  0.11  0.32  0.21  0.27  0.26  Chromium  Mercury  116  Influenta  Effluent  Class A  Class B  biosolids*  biosolids*  Molybdenum  20  20  1.46  4  1.82  1.82  Nickel  180  180  2.34  8.30  5.27  Phosphorus  n/r  n/r  5,019.75  0  Potassium  n/r  n/r  1,490.94  Selenium  14  14  Silver  n/r  Sodium  2†  2  1+2+L  1+2+SC+L  3.80  17.00  4.32  4.17  5.27  6.07  35.28  12.49  12.07  4,537.93  4,537.93  13,017.99  0  10,757.46  10,380.78  0  18,597.21  18,597.21  3,866.53  0  43,973.29  42,542.18  0.71  1.00  1.22  1.22  1.83  4.25  2.89  2.79  n/r  0.58  0  0.50  0.50  1.51  0  1.19  1.15  n/r  n/r  130.05  0  130,874.3  130,926.95  337.26  0  309,517.0  299,502.91  Strontium  n/r  n/r  17.57  0  849.73  850.03  45.56  0  2,009.61  1,944.50  Thallium  n/r  n/r  0  0  0  0  0.01  0  0.01  0.01  Tin  n/r  n/r  2.71  0  2.49  2.49  7.04  0  5.90  5.70  Titanium  n/r  n/r  9.91  0  13.42  13.40  25.70  0  31.75  30.66  Uranium  n/r  n/r  1.74  0  1.96  1.96  4.52  0  4.65  4.49  Vanadium  n/r  n/r  1.24  0  3.58  3.58  3.21  0  8.47  8.19  1,850  1,850  66.05  51.00  67.33  67.18  171.30  216.77  159.24  153.68  n/r  n/r  1.49  0  3.20  3.20  3.88  0  7.57  7.31  Zinc Zirconium  1  1+2+L  1+2+SC+L  1  Results (mg/kg dry weight)  *OMRR (2008) a Analysis made in CARO commercial laboratories (Kelowna, BC) †SunRype internal report: Brandt’s Creek Biosolids Analysis, November 2009, TWAS: thickened waste activated sludge.  117  118  

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