The Performance of a Sequencing Batch Reactor for The
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THE PERFORMANCE OF A SEQUENCING BATCH REACTOR FOR THE TREATMENT OF WHITEWATER AT HIGH TEMPERATURES by RHIANNON JOHNSON A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Civil Engineering) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1995 ©Rhiannon Johnson, 1995 in presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Ctv/i \ Ejnc\jneOJrO The University of British Columbia Vancouver, Canada Date Qcln °J5 DE-6 (2/88) i ABSTRACT Environmental and economic pressures on pulp and paper mills have prompted the adoption of water-reducing strategies such as Whitewater system closure. Efforts to reduce water use in the Whitewater system increase the Whitewater temperature and cause operational and quality problems in the papermachine through the build-up of dissolved contaminants in the Whitewater. To control the build-up of dissolved and colloidal substances in the Whitewater, an aerobic bioreactor is proposed to treat a substream of the closed Whitewater loop. This research investigated the biological treatability of a synthetic closed-system Whitewater at high temperatures with an aerobic biological sequencing batch reactor (SBR), focusing on the removal of resin and fatty acids, one of the problem compound groups. The bioreactor was operated at a hydraulic retention time (HRT) of 2 days and a solids retention time (SRT) of over 15 days with the intention of maintaining a viable biomass at a mixed liquor volatile suspended solids (MLVSS) level between 2000 and 5000 mg/L. The performance of the bioreactor was assessed at 20, 30, 40, 45, and 50°C in terms of total dissolved solids (TDS), total organic carbon (TOC), chemical oxygen demand (COD), and resin and fatty acid (RFA) removal. The removal of conventional contaminants such as TDS, TOC, and COD was significant at temperatures up to and including 40°C while at higher temperatures, contaminant removal was reduced. Parameters describing reactor operation and performance such as the food to microorganism ratio, the specific substrate utilization rate, and growth yield indicated a reduced conventional contaminant removal capability at temperatures higher than 40°C, along with a decrease in reactor biomass inventories at the higher temperatures. The removal efficiencies of fatty acids (FA) were over 95% at all temperatures, but for resin acids (PvA), near-complete removal was observed only up to 40°C. At higher temperatures, the removal efficiencies of RA were reduced, but still significant. Measurements during the SBR react cycle indicated that FA were mainly associated with the suspended solids, while RA were associated with both the liquid and solid phases. Observed specific removal rates decreased with increasing temperature, while maximum specific removal rates were high for all temperatures studied. For FA, the maximum removal rates were about twice the observed removal rates, while for RA, the maximum removal rates were about four times the observed removal rates. The FA content in the biomass appeared to decrease with increasing temperature, while the RA content appeared to increase. The RFA removed did not accumulate on the suspended solids because the RFA content in the biomass was negligible compared to the overall mass flow through the system. A large non-RFA extractable, chromatographable component of material was removed at all temperatures, though less removal was observed at 50°C. Overall, the bioreactor performed best at temperatures below 40°C for the removal of both conventional contaminants and RFA, especially, RA. These experiments indicated that the biological portion of the membrane bioreactor device would be able to control the concentrations of dissolved and colloidal material using feed from a closed-loop Whitewater application. The problems encountered at higher temperatures such as low sludge growth, solids loss in the effluent, and substantial RA in the effluent would be reduced with the combination of an ultrafiltration unit. Thus, treatment using the membrane bioreactor would probably be effective at temperatures higher than 40°C. iii TABLE OF CONTENTS page ABSTRACT ii TABLE OF CONTENTS iv LIST OF TABLES viii LIST OF FIGURES x ABBREVIATIONS xiv ACKNOWLEDGEMENTS xv 1. INTRODUCTION 1 1.1. Motivation of Research 1 1.2. Thesis Organization 1 2. BACKGROUND AND LITERATURE REVIEW 2 2.1. Introduction 2 2.1.1. Water Use in Mechanical Newsprint Mills 2 2.1:2. Systems Closure and Water Consumption Reduction . .... 3 2.1.3. Whitewater Recycling 4 2.1.4. Whitewater Treatment 6 2.2. Whitewater System 8 2.2.1. Current Whitewater System Configuration 8 2.2.2. Composition of Whitewater 9 2.2.2.1. Composition of Whitewater Under Low Volume Recycling Conditions 10 2.2.2.2. Composition of Whitewater under High Volume Recycling Conditions 10 2.2.3. Problems Associated with Whitewater Closure 16 2.2.3.1. Suspended Solids Build-up 16 2.2.3.2. Dissolved and Colloidal Substances Accumulation . 16 2.2.3.3. Effect on Paper Quality 20 2.2.4. Possible Whitewater Treatment Techniques 21 2.2.4.1. Biological Treatment 21 Aerobic 21 Anaerobic . 22 Combined Aerobic and Anaerobic Treatment 24 2.2.4.2. Membrane Treatments 26 iv page 2.2.4.3. Ultrafiltration 27 2.2 A A. Biological Treatment Combined with Ultrafiltration 28 2.2.4.5. Evaporation 29 2.2.4.6. Freeze Crystallization 31 2.2.4.7. Chemical Addition 31 2.2.4.8. Costs of Treatments 31 2.3. Potential Aerobic Treatability of a Closed Whitewater Stream 35 2.4. High Temperature Aerobic Treatment of Resin and Fatty Acids . 38 2.5. Sequencing Batch Reactor 39 2.5.1. Sequencing Batch Reactor Treatment of High-Strength Wastes 40 3. RESEARCH OBJECTIVES 43 4. MATERIALS AND EXPERIMENTAL METHODS 44 4.1. Reactor . 44 4.1.1. Water Bath for Temperature Control 45 4.1.2. Synthetic Whitewater Feed 45 4.1.3 Reactor Operation 46 4.1.4 Seed Organisms 47 4.1.5 Biomass Acclimatization 47 4.2. Experimental Design 48 4.2.1. Reactor Operating Parameters 48 4.2.1.1. Temperature 48 4.2.1.2. Solids Retention Time 51 • 4.2.2. Sampling 53 4.2.3. Sample Preservation and Storage 53 4.2.4. Analytical Techniques and Equipment 54 4.2.4.1. Resin and Fatty Acid Analysis 54 4.2.4.2. Gas Chromatography 55 4.2.4.3. Total Organic Carbon Assays 56 4.2.4.4. Chemical Oxygen Demand 56 4.2.4.5. Nutrients 57 4.2.4.6. Suspended Solids 57 5. RESULTS AND DISCUSSION 58 5.1. Influent Characteristics 58 5.1.1. Screw Pressate 58 5.1.1.1. Screw Pressate Storage Study 60 5.1.2. Evaporator Bottoms 65 v page 5.1.3. Influent. 66 5.2. Conventional Contaminants During Experimental Phase .... 68 5.2.1. Volatile Suspended Solids 68 5.2.2. Removal of Organics During Experimental Phase .... 75 5.2.2.1. Total Dissolved Solids 75 5.2.2.2. Total Organic Carbon 79 5.2.2.3. Chemical Oxygen Demand 79 5.3. Reactor Parameters 90 5.3.1. Food to Microorganism Ratios and Specific Substrate Utilization Rates 90 5.3.1.1. Food to Microorganism Ratios 91 5.3.1.2. Specific Substrate Utilization Rates 95 5.3.2. Growth Yield 98 5.3.3. Summary of Significance of Reactor Parameters 100 5.4. Resin and Fatty Acids Behaviour in the Reactor During the Experimental Period 101 5.4.1. Resin and Fatty Acids Removal 101 5.4.1.1. Resin and Fatty Acids Removal Efficiency Between the Influent and Effluent 101 5.4.1.2. Resin and Fatty Acids During the React Cycle 111 Total Resin and Fatty Acids 113 Fatty Acids in the Liquid and Solids Phases 118 Resin Acids in the Liquid and Solids Phases 123 Summary 123 5.4.1.3. Resin and Fatty Acids Removal Rates 128 Observed Removal Rates 129 Maximum Removal Rates 131 5.4.2. Fate of the Resin and Fatty Acids 134 5.4.2.1. Solids RFA Content 135 5.4.2.2. The Accumulation of Closely-Related RFA Transformation Products 138 6. CONCLUSIONS AND RECOMMENDATIONS 143 6.1. Conclusions 143 6.2. Recommendations 145 LITERATURE CITED 147 APPENDICES 154 Appendix A - Details on the Calculation of Growth Yield 155 Appendix B-Details on the Calculation of RFA Removal Rates 162 vi Appendix C - Individual RFA Removal Rates Appendix D - Raw Experimental Data vii LIST OF TABLES page Table 1. The potential problems associated with Whitewater closure listed by cause. 17 Table 2. The performances of the different treatment stages of ANAMET. 25 Table 3. Percent removal of various parameters from biologically pre-treated Whitewater by post-treatment with two types of ultrafiltration membranes. 28 Table 4. Estimated capital and operating costs for closed cycle options that do not produce effluent and conventional activated sludge secondary treatment that produces effluent for a TMP newsprint mill at different water usage rates. 33 Table 5. The capital and operating costs for the closure of an existing integrated newsprint mill at different water usage rates as compared to a conventional "end-of-the-pipe" biological treatment system. 34 Table 6.