MULTIPLE-COMPARTMENT ANAEROBIC BIOREACTORS FOR THE GENERATION OF ENERGY ...

310 Pages·2017·5.63 MB·English

by  Carissa Homme

MULTIPLE-COMPARTMENT ANAEROBIC BIOREACTORS FOR THE GENERATION
OF ENERGY: EXPLORING ENERGY-POSITIVE WASTEWATER TREATMENT

by
Andrew R. Pfluger
Copyright by Andrew Ross Pfluger 2018
All Rights Reserved
A thesis submitted to the Faculty and Board of Trustees of the Colorado School of Mines
in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Civil and
Environmental Engineering).

Golden, Colorado

Date: __________________________

Signed: __________________________
Andrew R. Pfluger

Signed: __________________________
Dr. Junko Munakata-Marr
Thesis Advisor

Signed: __________________________
Dr. Linda A. Figueroa
Thesis Advisor

Golden, Colorado

Date: __________________________

Signed: __________________________
Dr. Terri S. Hogue
Professor and Head
Department of Civil and Environmental Engineering

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ABSTRACT
Wastewater contains resources such as energy, clean water, and nutrients. Under the
current wastewater treatment paradigm (i.e., activated sludge), resources are consumed rather
than recovered. Anaerobic bioreactors are a potentially viable alternative to traditional aerobic
wastewater treatment for several reasons, to include their ability to generate methane-rich
biogas while simultaneously reducing volumes of waste sludge and decreasing waste disposal
burden. Multiple-compartment anaerobic bioreactors, such as the anaerobic baffled reactor
(ABR), are particularly attractive due to the reactor’s low complexity and its ability to generate
methane with little to no energy input. Despite these advantages, pilot-scale demonstrations of
ABRs, or variations of the ABR, operated under colder wastewater temperatures (11 – 24 C)
are extremely limited. Prior to widespread implementation, ABRs treating domestic wastewater
require additional pilot-scale demonstration, study of the lifecycle impacts relative to
conventional wastewater treatment technologies, and a more complete understanding of the
microbial community dynamics for modeling and performance prediction.
To address these research needs, this dissertation examines the performance of two
low-complexity pilot-scale multiple-compartment anaerobic bioreactors in three different areas:
(1) characterizing bioreactor performance over varying temperatures for organic removal,
suspended solids removal, and methane generation; (2) modeling lifecycle impacts and energy
generating potential relative to conventional wastewater treatment approaches; and (3)
characterizing methanogenic community structure over time and space within both bioreactor
systems. The pilot-scale anaerobic bioreactors characterized in this study were: (1) an existing
four-compartment ABR located at the Plum Creek Water Reclamation Authority in Castle Rock,
CO, and (2) a three-compartment ABR coupled with an anaerobic fixed film reactor (AFFR),
which was constructed at the Mines Park Wastewater Test Bed. Modeling methods include full
treatment train modeling in BioWin 5.2, environmental impact modeling in SimaPro (version
8.0.3.14), lifecycle cost modeling in CAPDETWorks (version 2.5, Hydromantis, Inc.), and
uncertainty modeling (Monte Carlo simulation) in Oracle Crystal Ball. Microbial community
structure was examined using 16S rRNA gene sequencing.
Key findings of this study are numerous, and include: (1) both ABRs studied remove
higher levels of organics and suspended solids relative to conventional primary treatment while
generating near stoichiometric volumes of methane; (2) ABRs have high chemical energy
conversion efficiencies relative to other wastewater treatment reactors, recovering 52% of the
chemical energy available in the influent wastewater organics; (3) modeling suggests that
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energy generated by ABRs coupled with combined heat and power (CHP) with heat recovery is
sufficient to power many typical conventional activated sludge systems; (4) lifecycle
environmental impacts for treatment trains including ABRs are lower in most impact categories
(e.g., fossil fuel emissions, acidification, etc.), but dissolved methane capture is required to
reduce greenhouse gas emissions and enhance potential energy generation; (5) lifecycle costs
and net energy balances for modeled configurations with ABRs are lower relative to
conventional treatment configurations; and (6) both ABRs developed similar methanogen-rich
microbial communities dominated by Methanosaeta, an acetate-utilizing methanogen.
Additional study is needed in several areas, to include the treatment of residual
contaminants in the effluent of ABRs and long-term characterization of the microbial community
structure for accurate modeling. However, this study concludes that multiple-compartment
anaerobic bioreactors, such as the ABR, are a viable energy-generating alternative to
conventional primary treatment. Full-scale demonstrations should be implemented near-term.

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TABLE OF CONTENTS
ABSTRACT.................................................................................................................................. iii
LIST OF FIGURES........................................................................................................................x
LIST OF TABLES........................................................................................................................xiv
ACKNOWLEDGEMENTS..........................................................................................................xvii
DEDICATION............................................................................................................................xviii
CHAPTER 1 INTRODUCTION...................................................................................................1
1.1 Wastewater-Energy Nexus....................................................................................1
1.2 Anaerobic Wastewater Treatment.........................................................................2
1.3 Multiple-Compartment Anaerobic Bioreactors.......................................................4
1.4 Research Questions, Objectives, and Dissertation Structure................................5
1.5 Research Motivation..............................................................................................7
CHAPTER 2 METHANE GENERATION AND METHANOGENIC COMMUNITY
STRUCTURE IN AN ANAEROBIC BAFFLED REACTOR FOR
BIOLOGICALLY ENHANCED PRIMARY TREATMENT OF DOMESTIC
WASTEWATER UNDER COLD TEMPERATURES..............................................8
2.1 Abstract..................................................................................................................8
2.2 Introduction............................................................................................................9
2.3 Materials and Methods.........................................................................................11
2.3.1 Anaerobic Reactor Configuration.............................................................11
2.3.2 Data Collection and Analysis...................................................................12
2.3.3 Microbial Community Structure................................................................13
2.4 Results and Discussion........................................................................................14
2.4.1 ABR-AFFR Approached Effluent Discharge Standards Under Warmer
Temperatures...........................................................................................15
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2.4.2 Observed Methane Production Approaches the Theoretical Maximum
and Varies with Wastewater Temperatures.............................................20
2.4.3 The ABR-AFFR is an Energy-Positive Process.......................................24
2.4.4 Relative Abundance of Euryarchaeota Increased Between Warm-
and Cold-Weather Samples.....................................................................25
2.4.5 Complete Energy-Positive Wastewater Treatment Configurations..........29
2.5 Conclusions.........................................................................................................30
2.6 Acknowledgements..............................................................................................31
CHAPTER 3 ENERGY GENERATING POTENTIAL OF BIOLOGICALLY ENHANCED
PRIMARY TREATMENT OF DOMESTIC WASTEWATER USING
MULTIPLE COMPARTMENT BIOREACTORS………….....................................32
3.1 Abstract................................................................................................................32
3.2 Introduction..........................................................................................................33
3.3 Materials and Methods.........................................................................................34
3.3.1 Anaerobic Reactor Configurations...........................................................34
3.3.2 Data Collection and Analysis...................................................................35
3.3.3 Energy-Related Calculations....................................................................36
3.3.4 Uncertainty Analyses...............................................................................37
3.4 Results and Discussion........................................................................................40
3.4.1 Comparison of Observed Organic Removal and Methane Generation
to Other Sludge Blanket Bioreactor Studies.............................................40
3.4.2 Comparison of Theoretical and Observed Methane Generation..............42
3.4.3 Modeled Energy Generation from Combined Heat and Power
Technologies............................................................................................46
3.4.4 Implications for Integration of Anaerobic Primary Treatment using
ABRs into WWRFs...................................................................................47
3.4.5 Path Forward for Anaerobic Primary Treatment using ABRs .................. 48
3.5 Conclusions.........................................................................................................53
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3.6 Acknowledgements..............................................................................................53
CHAPTER 4 LIFECYCLE COMPARISON OF MAINSTREAM ANAEROBIC BAFFLED
REACTOR AND CONVENTIONAL ACTIVATED SLUDGE SYSTEMS FOR
DOMESTIC WASTEWATER TREATMENT........................................................54
4.1 Abstract................................................................................................................54
4.2 Introduction..........................................................................................................55
4.3 Materials and Methods.........................................................................................56
4.3.1 System Boundaries and Functional Unit..................................................56
4.3.2 System Design for Lifecycle Inventory and Modeling..............................58
4.3.3 Uncertainty and Sensitivity Analyses.......................................................60
4.4 Results and Discussion........................................................................................61
4.4.1 NEB for Configurations with AnP are Lower Than Conventional
Systems...................................................................................................61
4.4.2 Recovery of dCH is Required to Reduce Global Warming Impacts
4
and Enhance Energy Generation.............................................................62
4.4.3 AnP/AeS+AnD Configurations Have Lower Impacts Relative to
Conventional Treatment Configurations in Most Impact Categories........65
4.4.4 Lifecycle Costs of Configurations with Anaerobic Primary Treatment
are Lower than Conventional Systems....................................................67
4.4.5 AnP Coupled with Other Anaerobic Technologies May be a Path
Forward for Energy-Positive Domestic Wastewater Treatment
with Further Study....................................................................................69
4.5 Acknowledgements..............................................................................................71
CHAPTER 5 SUCCESSION OF A FOUNDING MICROBIOME AFTER SEEDING IN A
MULTIPLE-COMPARTMENT ANAEROBIC BIOREACTOR FOR
DOMESTIC WASTEWATER TREATMENT........................................................72
5.1 Abstract................................................................................................................72
5.2 Introduction..........................................................................................................73
5.3 Materials and Methods.........................................................................................75
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5.3.1 Reactor Operation and Performance Modeling........................................75
5.3.2 Sludge Sampling, DNA Extraction, and 16S rRNA Gene Sequencing....77
5.3.3 Amplicon Sequence Processing and Quality Control...............................77
5.3.4 Statistical Methods and Analyses............................................................77
5.4 Results…………………........................................................................................78
5.4.1 Wastewater Chemistry and Reactor Performance...................................78
5.4.2 Consistency of Influent Wastewater Community Structure over
Time and Location....................................................................................79
5.4.3 Community Assembly Over Time and Space in Reactor
Compartments..........................................................................................82
5.4.4 Increasing Percent Relative Abundance of Euryarchaeota......................83
5.4.5 Persistence of the Founding Microbiome.................................................87
5.5 Discussion………….............................................................................................88
5.5.1 Changes in Community Similarity Suggest Two Successional
Trajectories in ABR 2...............................................................................88
5.5.2 Increasing Percent Relative Abundance of Euryarchaeota Drove
Community Similarity...............................................................................90
5.5.3 A Founding Microbiome Persists in each ABR 2 Compartment
Over Time................................................................................................91
5.6 Conclusions.........................................................................................................92
5.7 Acknowledgements..............................................................................................92
CHAPTER 6 CONCLUSIONS AND FUTURE WORK..............................................................93
6.1 Conclusions.........................................................................................................93
6.2 Future Work.........................................................................................................95
REFERENES CITED...................................................................................................................97
APPENDIX A: SUPPLEMENTARY INFORMATION FOR CHAPTER 2...................................123
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APPENDIX B: SUPPLEMENTARY INFORMATION FOR CHAPTER 3...................................133
APPENDIX C: SUPPLEMENTARY INFORMATION FOR CHAPTER 4...................................137
APPENDIX D: SUPPLEMENTARY INFORMATION FOR CHAPTER 5...................................165
APPENDIX E: STATISTICAL EXPOSÉ OF A MULTIPLE-COMPARTMENT
ANAEROBIC REACTOR TREATING DOMESTIC WASTEWATER.................173
APPENDIX F: TECHNOLOGY DIFFUSION: ANAEROBIC DIGESTION AND BIOGAS
BENEFICIAL USE AT MUNICIPAL WASTEWATER TREATMENT
FACILITIES IN COLORADO: BARRIERS TO WIDESPREAD
IMPLEMENTATION...........................................................................................208
APPENDIX G: TECHNOLOGY APPLICATION: METHANE-GENERATION VIA
ANAEROBIC MICROBES AS A SUSTAINABLE APPROACH FOR
RESOURCE-LIMITED DEEP SPACE EXPLORATION.....................................251
APPENDIX H: TECHNOLOGY APPLICATION: BIOGAS GENERATION FROM WASTE:
OVERCOMING BARRIERS TO WIDESPREAD IMPLEMENTATION OF
ANAEROBIC TECHNOLOGIES IN THE DEPARTMENT OF DEFENSE
FOR ENERGY SECURITY................................................................................257
APPENDIX I: ENGINEERING EDUCATION: MAINTAINING STUDENT ENGAGEMENT
IN AN EVENING, THREE HOUR LONG AIR POLLUTION COURSE:
INTEGRATING ACTIVE LEARNING EXERCICES AND FLIPPED
CLASSES..........................................................................................................263
APPENDIX J: ENGINEERING EDUCATION: LEARNING BENEFITS OF INTEGRATING
SOCIO-ECONOMIC AND CULTURAL CONSIDERATIONS INTO AN
ONSITE WATER RECLAMATION COURSE PROJECT..................................276

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