Loughborough University Institutional Repository Combined anaerobic respiration (CAD) of sewage sludge and other urban solid wastes ThisitemwassubmittedtoLoughboroughUniversity’sInstitutionalRepository by the/an author. Additional Information: • A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University. Metadata Record: https://dspace.lboro.ac.uk/2134/8025 Publisher: (cid:13)c Hong Deng Please cite the published version. This item is held in Loughborough University’s Institutional Repository (https://dspace.lboro.ac.uk/) and was harvested from the British Library’s EThOS service (http://www.ethos.bl.uk/). It is made available under the following Creative Commons Licence conditions. For the full text of this licence, please go to: http://creativecommons.org/licenses/by-nc-nd/2.5/ COMBINED ANAEROBIC DIGESTION (CAD) OF SEWAGE SLUDGE AND OTHER URBAN SOLID WASTES by Hong Deng A Doctoral Thesis Submitted in Partial Fulfilment the Requirements of for the Award Doctor Philosophy Loughborough University of of of 29th November 2006 © by Hong Deng 2006 Abstract The UK buries about 100 million tonnes of waste a year, of which 25% is municipal (refuse). The impacts from leachate solid waste environmental gas and releases known direct to health from landfill Europe has are and risks are reported. agreed to a Landfill Directive which has set targets for the stepwise reduction in biodegradable municipal waste going to landfill. The anaerobic digestion of in bioreactors is that municipal solid waste controlled an area could play an important role in overall evolution towards sustainability by recovering biogas and organic matter. Separated hydrolysis demonstrated and subsequent anaerobic codigestion was from the literature to have the best for biodegradable review potential municipal waste diverted from landfill. The rate of hydrolysis of solids wastes remains an outstanding problem. In this research, firstly the codigestion of industrial effluent (coffee wastewater), food wastes and garden wastes were investigated for their impact on hydrolysis and for digestion. The results show that there were no treatability problems coffee wastes up to 37.5% of volume feed per day at the HRT of 9 days. The results supported the view that dilute biodegradable streams such as coffee waste may improve digestion by promoting mixing. Fruit and vegetable wastes were highly biodegradable and can have a major improvement in biogas production of the whole codigestion process, whereas garden waste was not as successful as a co- lignocelluloses substrate, probably because of the predominant celluloses and with low biodegradability. a The literature review also revealed that washing or elutriation can remove organic from This is important hydrolytic in matter municipal waste. an process which a is The hydrolysate solubilised acidic organic matter obtained. codigestion of refuse A digester treating with sewage sludge was therefore studied. control sewage fed sludge only was compared with an experimental reactor mixed refuse hydrolysate with sewage sludge. It was possible to add the solubilised hydrolysate to digesters designed loading existing anaerobic at a standard sludge solids rate The without causing overloading. experimental reactor was also more effective, e. g. total 17.4% higher than that for the organic carbon removal was control reactor, and dewaterability 35.8% better than that for the These was control. parameters indicated that degradation degradable combined of sewage sludge with an easily hydrolysate to digestion domestic was preferable with un-hydrolysed waste or This digesters sewage sludge solely. approach makes use of existing and disposal The agricultural routes after post-treatment an alternative. potential toxic elements were monitored as part of this experiment and there was no extra effect from the combined anaerobic digestion. The the to be sludge met regulation recycled to agricultural land. The data the information for were used as supportive the establishment full digestion for treating of a scale anaerobic plant municipal solid waste built in Leicester (2004). The digestion (MSW) anaerobic of municipal solid waste alone was also investigated in this A high load to 15.5%TS tested. However study. solids up was the solid load had to be reduced to 10% because the high load and the fibre content interfered then the failure the digester. The with mixing and caused of research here indicated better is The reported a characterization of solid waste needed. lignocelluloses the important influences particle size and content were most on Therefore dilution better. reactor operation. codigestion and worked much In this hydrolysis investigated. The hydrolytic research, pretreatment was also rate linked to the temperatures In link was significantly and organic contents. addition, a between the hydrolytic inoculum type, type, rate and waste enzyme and stirring was losses the explored, although of volatile organic carbon were a problem with separated hydrolysis tests. Mesophilic temperatures 30 hours hydrolysis and up were optimum. Further in the work was recommended, particular on application of adapted culture to improve lignocelluloses hydrolysis to the MSW and reduce particle sizes. Key Anaerobic digestion; Codigestion; Sewage Refuse hydrolysate; Organic words: sludge; fraction (OFMSVI); Coffee Lignocellulose; Hydrolysis; of municipal solid waste waste; Solubilisation; Specific biogas yield. Acknowledgments I like to thank Professor Andrew Wheatley to the to do this would give me chance PhD to thank his invaluable and continuously great advice and support and technical insight throughout this He has his project. given me research spirit. I particularly want to thank the technicians in the laboratory, Geoff, Stuart, water Nina Jay for and their technical throughout the advice, qualified assistance all laboratory works and dealing with any problems that occurred during the project performance. A special thank is extended to Paul Griffin of Severn Trent Water Ltd. for his helpful discussions Thanks constructive advice and suggestions, and comments. due to Peter Jones Michael Davis from Biffa for are also and providing support and for the interpretation the constantly challenging of results. I like to thank friends Water Group the would all my as well as my colleagues at of Department the for their helping their fun. over years always and Finally, I like to thank for their would also my parents continuous encouragement husband, for his love, invaluable help, and support, and especially to my encouragement throughout time in the and spirit support all my past. Published Work Deng, H. Wheatley, A. D. (2005). Hydrolysis food and and co-digestion of wastes. 4"' International Symposium Anaerobic Digestion Solid Waste (ADSK9, on of Conference Proceedings, Volume 2,383-388, August September, 2005, -2 Copenhagen, Denmark. Deng, H., Griffin, P. Wheatley, A. D. (2004). Combined digestion and anaerobic of Anaerobic Digestion 2004, Proceedings, sewage sludge and pretreated refuse. Volume 3,1711-1715,10th World Congress Anaerobic Digestion, Montreal, on Canada. Deng, H. Wheatley, A. D. (2004). Hydrolysis Food Waste. A to and of report Severn Trent Water UK. plc., Deng, H. Wheatley, A. D. (2003). Dual anaerobic co-digestion of sewage and 4t' IWA UK Young Researchers Conference 2-3 sludge and refuse. proceeding, April, 2003, Newcastle University, UK. Deng, H. Wheatley, A. D. (2002). Co-digestion of sewage sludge and and household (kitchen 3'd IWA UK Young Researchers Conference waste waste). proceeding, 17 18 April, 2002, University of Nottingham, UK - Deng, H. Wheatley, A. D. (2001). Combined digestion (CAD) of and anaerobic coffee waste and sludge. 2'd IWA UK Young Researchers Conference proceeding, 24 25 April, 2001, Cranfield University, UK. - iv Table Contents of List Figures ix of List Plates of xv List Tables of xvi Abbreviations & Symbols xx Chapter 1 Introduction 1 1.1 BACKGROUND OF THE RESEARCH 1 1.2 AIM OF THE RESEARCH 3 1.3 OUTLINE OF THE THESIS 5 8 Chapter 2 Literature Review 9 2.1 THE PROBLEMS 2.1.1 Municipal Waste Composition Disposal 9 and 13 2.1.2 Legal Framework for Landfill 2.1.3 The Options Diverting Organic Material from Landfill 15 of 2.1.4 Potential Anaerobic Digestion Waste 18 of of 29 2.1.5 The UK's Situation 2.1.6 Summary 34 2.2 ANAEROBIC DIGESTION PROCESS 37 2.2.1 Mechanism 37 Anaerobic Bioconversion of 2.2.2 Control Evaluation for Anaerobic Process 40 and 2.2.3 Overall Rate-Limiting Step 44 2.2.4 Technologies for Anaerobic Digestion Solid Waste 48 of 2.3 RESEARCH AND APPLICATION OF ANAEROBIC DIGESTION ON WASTES 54 2.3.1 Pretreatment Processes for MSW Digestion 55 2.3.2 Anaerobic Digestion of Organic Fraction of Solid Waste 65 Other Industrial Waste 2.3.3 Biodegradation 84 of 2.4 CHAPTER SUMMARY 86 V Chapter 3 Experimental Methodology Apparatus 89 and 3.1 EXPERIMENTS OF HYDROLYSIS 90 3.1.1 Components Food Waste 90 of 3.1.2 Mechanical Disruption for Reducing Waste Size Homogenisation 91 and 3.1.3 Hydrolysis Experiment Set-up 92 3.2 CO-DIGESTION EXPERIMENTS 96 3.2.1 Co-Digestion Pretreated Refuse Sewage Sludge 96 of and 3.2.2 Co-Digestion Other Wastes Sewage Sludge 99 of and 3.3 OFMSW DIGESTION EXPERIMENTS 100 3.4 ANALYSIS TECHNIQUES 100 3.4.1 Standard Methods 100 3.4.2 Non-Standard Methods 102 Chapter 4 Hydrolysis Experiments Results Discussion 108 and - 4.1 EFFECTS OF INDIVIDUAL FACTORS ON HYDROLYSIS PROCESS 108 4.1.1 Effect Temperature Acid-Forming Process 108 of on 4.1.2 Effect Solids Waste Contents 112 of 4.1.3 Effect Mechanical Mixing 115 of 4.2 EFFECTS OF INTEGRATED/MULTIPLE FACTORS ON HYDROLYSIS PROCESS 117 4.2.1 The their during 117 characteristics of waste and change experiments 4.2.2 Sensitivity the factors influencing 121 analysis of acid-formation 4.2.3 Investigation inoculum 125 of effects 4.3 CHAPTER SUMMARY 127 Chapter 5 Combined Anaerobic Digestion Industrial Domestic Waste of or Sewage Sludge Results Discussion 131 and and - 5.1 CODIGESTION OF COFFEE WASTE AND SEWAGE SLUDGE 132 5.1.1 Start-Up Period 132 5.1.2 Codigestion Coffee Waste Sewage Sludge 138 of and 5.2 CODIGESTION OF OTHER WASTES AND SEWAGE SLUDGE 143 5.2.1 Codigestion of Garden Waste and Sewage Sludge 143 5.2.2 Codigestion of Fruit and Vegetable Waste and Sewage Sludge 146 5.3 CHAPTER SUMMARY 148 vi Chapter 6 Combined Digestion Pretreated Refuse Sewage Sludge of and Results Discussion 152 and - 6.1 EXPERIMENTAL PROGRAMME 152 6.2 CHARACTERISATION OF HYDROLYSATE AND FEED SLUDGE 153 6.2.1 Characteristics Hydrolysate 153 of 6.2.2 Characteristics Feed Sludge 156 of 6.3 DIGETER PERFORMANCE 157 6.3.1 Organic Loading Rate 157 6.3.2 Solids Destruction the Effect HRT 159 and of 6.3.3 Specific Performance Parameters 167 6.3.4 Alkalinity 174 pH and 6.3.5 Ammonia Content 177 6.3.6 Total Organic Carbon 178 6.4 SLUDGE RESIDUES 178 6.4.1 Metals 178 6.4.2 Dewatering Characteristics 184 6.4.3 Odour Potential 185 6.4.4 Foaming 185 6.5 CHAPTER SUMMARY 186 Chapter 7 MSW Digestion 188 7.1 OBJECTIVE AND METHODS 188 7.2 CHARACTERISTICS OF WASTE 189 7.2.1 Composition Distribution After Pretreatment 190 7.2.2 Solid Waste Contents in Different Treatment Process 191 7.3 LAB-SCALE TRIALS 194 7.3.1 Performance Results Digester 1 the Control 194 and of as 7.3.2 Performance Results Digester 2 for Prehydrolysed MSW Treatment 213 and of 7.3.3 Performance Results Digester 3 for Enzyme Addition Treatment 222 and of 7.3.4 Summary 231 7.4 SCREENING ENZYME 233 7.4.1 Experiment Procedure 234 7.4.2 Results Discussion and 235 VII