Ramin Yazdani. Quantifying Factors Limiting Aerobic Degradation During Aerobic Bioreactor ...

127 Pages·2010·0.86 MB·English

Quantifying Factors Limiting Aerobic Degradation During Aerobic Bioreactor Landfilling
and Performance Evaluation of a Landfill-Based Anaerobic Composting Digester for
Energy Recovery and Compost Production

By
RAMIN YAZDANI
B.S. (California Polytechnic State University) 1986
M.S. (University of California-Davis) 1988

DISSERTATION
Submitted in partial satisfaction of the requirements for the degree of
DOCTOR OF PHILOSOPHY
in
Civil & Environmental Engineering
in the
OFFICE OF GRADUATE STUDIES
of the
UNIVERSITY OF CALIFORNIA
DAVIS
Approved:
__________________________________________
George Tchobanoglous, Chair

__________________________________________
Masoud Kayhanian

__________________________________________
Jeannie Darby

Committee in Charge
2010
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To my wife and children

To my parents, sister, and grandparents

“From cane reeds, sugar.
From a worm's cocoon, silk.
Be patient if you can, and from sour
grapes will come something sweet.”
By Jalaluddin Rumi

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ABSTRACT

In the first part of the study, a bioreactor landfill cell was operated
aerobically for six months to quantify the extent of aerobic degradation and
mechanisms limiting aerobic activity during air injection and liquid addition. From
an analysis of in situ aerobic respiration and gas tracer data, it was found that a
large fraction of the gas filled pore space was in immobile zones where it was
difficult to maintain aerobic conditions, even at relatively moderate landfill cell-
average moisture contents of 33-36%. Even with the intentional injection of air,
anaerobic activity was never less than 13%, and sometimes exceeded 65%.
Analyses of gas tracer and respiration data were used to quantify rates of
respiration and rates of mass transfer to immobile gas zones. The similarity of
these rates indicated that waste degradation was influenced significantly by rates
of oxygen transfer to immobile gas zones, which comprised 32 to 92% of the
gas-filled pore space.

In the second part of the study, a landfilled-based two-stage
(anaerobic/aerobic) batch digester cell was constructed, operated, and monitored
for treatment of source separated green waste while recovering energy and
compost. The performance of this unique two-stage batch digester was
evaluated in terms of cell operating temperature, leachate quality, methane
generation rate, air emissions, waste decomposition indicators, energy
production, and compost quality. The overall average temperatures of the cell
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during the anaerobic and aerobic phases were desirably high, in the thermophilic
range. Although concentration of ammonia reached a high value of 2,400 mg/L,
the volatile fatty acids concentrations and pH values were consistent with a
healthy digester with no inhibition of methane production throughout the
operating period. The decay rate observed in the landfill digester (k = 0.82/yr)
thus represents about a 20-fold acceleration of methane generation compared to
the U.S. EPA default for solid waste. The biofilter’s removal of volatile organic
compounds and total gaseous non-methane organic compounds varied from 99
to 96% and 99 to 68%, respectively. The biochemical methane potential
decreased by 83% during the entire operation, indicating compost feedstock
contents were well decomposed. Compost removed and tested passed all of the
U.S. Composting Council’s Seal of Testing Approval Standards.

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ACKNOWLEDGMENTS

I would like to thank all of the people who guided and supported me
through this long journey. First, I would like to express my sincere appreciation to
my major professor, Dr. George Tchobanoglous, for his contributions and advice.
He has been an inspiration and a source of encouragement and support during
my graduate research work. I am grateful to Dr. Masoud Kayhanian for his
support, technical review and valuable suggestions. My heartfelt thanks to Dr.
Jeannie Darby, for her guidance and advice.

Second, I am grateful to Mr. Don Augenstein for helping fund portion of
the aerobic bioreactor landfill research work through funds from DOE-NETL. I
am grateful for all of our lengthy creative discussions, from which I received
diligent advice on improving my research work.

Third, I would also like to thank Dr. Paul Imhoff and Dr. Pei Chiu at the
University of Delaware for their valuable and creative contributions towards the
aerobic bioreactor research. I would also like to thank Dr. Byunghyun Han and
M. Erfan Mostafid for their valuable contributions.

Fourth, I am also grateful to Dr. Morton Barlaz at the North Carolina State
University for his contributions towards the anaerobic composting digester
project. His collaboration in laboratory testing, insightful observation during
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operations and monitoring, and many other constructive ideas improved the
results of this research project. It was a pleasure working with him and I continue
to appreciate his valuable input.

Fifth, I am grateful to the funding agencies that made it possible to
conduct this research, namely: California Department of Resources Recycling
and Recovery (CalRecyle); U.S. Department of Energy-NETL; and the Yolo
County. I would like to give a sincere thanks to Scott Walker with CalRecycle
who was instrumental in funding these projects. I would also like to thank my
employer, Yolo County, for their continued support during my graduate studies.
The generous support of Environmental Research and Education Foundation
scholarship for my doctorate degree is acknowledged and gratefully appreciated.

Finally, I would like to thank my parents and other family members that
have supported me through the many years I have been working on this degree.
I would like to thank my wife, Becca for her love and support and our son, Dara,
and daughter, Eilis, who have endured my many hours and years of graduate
work and have encouraged me to finish. I dedicate this work to everyone in my
family for being by my side and supporting and loving me unconditionally. I could
have not done this without the love and support of everyone. I dedicate this to
work to you all.

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CONTENTS

Page

ABSTRACT……………………………………………………………………….. iii
ACKNOWLEDGMENTS………………………………………………………….v
LIST OF FIGURES………………………………………………………………. x
LIST OF TABLES………………………………………………………………… xiii
DISSERTATION OVERVIEW…………………………………………………... 1

CHAPTER 1- Quantifying Factors Limiting Aerobic Degradation During Aerobic
Bioreactor Landfilling
1.0 ABSTRACT…………………………………………………………………. 6
1.1 INTRODUCTION…………………………………………………………… 7
1.2 MATERIALS AND METHODS……………………………………………. 10
1.2.1 Landfill design and instrumention………………………………… 10
1.2.2 Landfill cell operation and testing………………………………… 13
1.2.3 In-situ aerobic respiration tests…………………………………… 15
1.2.4 Partitioning gas tracer tests……………………………………….. 15
1.3 RESULTS AND DISCUSSION………………………………………….... 17
1.3.1 Fluid pressure and gas composition……………………………... 17
1.3.2 In-situ aerobic respiration test results……………………………. 24
1.3.3 Partitioning gas tracer tests (PGTTs)……………………………. 25
1.4 FINDINGS….....…………………………………………………………….. 30
1.5 REFERENCES………………………………………………………………31
1.6 APPENDIX A……………………………………………………………….. 34

CHAPTER 2 – Performance Evaluation of a Landfill-Based Anaerobic
Composting Digester for Energy Recovery and Compost
Production
2.0 ABSTRACT…………………………………………………………………. 56
2.1 INTRODUCTION…………………………………………………………… 58
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2.2 MATERIALS AND METHODS……………………………………………. 61
2.2.1 Design and operation……………………………………………… 61
2.2.2 Monitoring and data analysis……………………………………… 67
2.2.2.1 Waste temperature monitoring………………………… 67
2.2.2.2 Leachate quality data and analysis…………………….67
2.2.2.3 Gas rate and characteristics…………………………… 68
2.2.2.3.1 Anaerobic phase methane
generation rate…………………………….. 68
2.2.2.3.2 Aerobic phase gas testing
and emissions……………………………... 70
2.2.2.4 Waste decomposition and related indicators
Monitoring………………………………………………... 73
2.2.2.4.1 Biochemical methane potential,
cellulose, hemicellulose, and
moisture content………………………….. 74
2.2.2.4.2 Compost quality…………………………… 75
2.2.2.5 Net energy production measurement and calculation. 77
2.3 RESULTS AND DISCUSSION…………………………………………… 79
2.3.1 Waste temperature during filling, anaerobic phase and
aerobic phase………………………………………………………. 79
2.3.2 Leachate quality……………………………………………………. 82
2.3.3 Methane generation rate and composition………………………. 86
2.3.4 Biofilter treatment efficiency……………………………………… 88
2.3.5 Indicator parameters for waste decomposition and product
Stability……………………………………………………………… 92
2.3.6 Moisture balance during anaerobic and aerobic phase………... 95
2.3.7 Compost quality…………………………………………………….. 97
2.3.7.1 Physical characteristics of compost…………………… 97
2.3.7.2 Chemical characteristics of compost………………….. 103
2.3.7.3 Biological characteristics of compost…………………. 106
2.3.7 Overall net energy balance………………………………………...107
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2.4 FINDINGS…………………………………………………………………... 108
2.6 REFERENCES………………………………………………………………110
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LIST OF FIGURES

Figure 1.1: Cross sectional view of Yolo County aerobic bioreactor landfill cell
illustrating the location of instrumentation, gas collection and
leachate recirculation lines, respiration tests locations, and
partitioning gas tracer tests…………………………………………..11
Figure 1.2: Percent anaerobic activity and total fluid pressure in
instrumentation layers 1 and 2. Measurements reported for layer 1
and 2 are averages of all readings in each layer. Periods when the
blower was off for longer than 2 days are indicated……………….14

Figure 1.3: Contours of gas composition in layer 1 on 8/23/06. Solid lines
correspond to outline of landfill. (a) Percent anaerobic activity.
Dashed lines represent regions where P ≥ 50% and dotted lines
where P < 50%. (b). Oxygen concentration. Dashed lines represent
regions where oxygen concentration < 10%. (c) Waste temperature.
Dashed lines represent regions where landfill temperature >
70°C………………………………………………………………….... 23

Figure 1.4: Data from in-situ respiration tests in aerobic bioreactor landfill
cell……………………………………………………………………... 25

Figure A1(a): Plan view of aerobic landfill cell…………………………………….. 35

Figure A1(b): Schematic of total fluid pressure measurement and vertical cross-
section…………………………………………………………………. 35

Figure A2(a): Cumulative supplemental liquid added and leachate recirculated
during the operational periods……………………………………… 36

Figure A2(b): Cumulative gas flow exiting the landfill during the six month period
when the landfill cell was operated as an aerobic bioreactor…… 37

Figure A3: Daily moving average gas flow rate during operation of aerobic
bioreactor cell………………………………………………………….38
Figure A4: Variation of percent anaerobic activity, P, for the extreme case of
60% CH and 40%CO ……………………………………………….39
4 2

Figure A5: Variation of percent anaerobic activity, P, for the extreme case of
40% CH and 60% CO ……………………………………………... 40
4 2

Figure A6: Aerobic bioreactor cell moisture content based on EPA method (8)
and total fluid pressure determined from bubble level monitor and
LLDPE tubes in instrumentation layers 1 and 2. Measurements
reported for layer 1 and 2 are averages of all readings in each
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