Long-Term Performance of Enhanced Anaerobic Bioremediation and the Occurrence of Sustained

348 Pages·2013·3.63 MB·English

by  Michael Burcham

ABSTRACT
Long-Term Performance of Enhanced Anaerobic
Bioremediation and the Occurrence of Sustained Treatment at
Chlorinated Solvent Sites
by
Michael Burcham
The objective of this research was to evaluate the long-term performance of enhanced
anaerobic bioremediation (EAB) at chlorinated solvent sites and the occurrence of
sustained treatment following EAB. A database of groundwater concentration versus
time records was compiled for 25 sites with at least three years of post-treatment data.
The median post-treatment monitoring period for these sites was 5.2 years, with a
maximum of 11.7 years. Long-term performance was evaluated based on concentration
changes from before treatment to the final year of post-treatment monitoring. Results
indicate that the median concentration reduction for all 25 sites was approximately 80%,
just under 1 order of magnitude. Sustained treatment, where concentrations remain
suppressed after ceasing active treatment, was evaluated using a lines-of-evidence
approach including analysis of rebound, statistical concentration trends after treatment,
and decay rates from before and after treatment. Results indicate that sustained treatment
is occurring at a majority of the sites.
Acknowledgments
I want to send my sincerest thanks to anyone who has supported me through the
Master of Science thesis process. It has given me some bumps and bruises, but the
support and encouragement from those people allowed me to successfully navigate these
sometimes treacherous waters.

Special thanks to:
Dr. Philip Bedient, for his mentorship and guidance, and for supporting the
continuation of my education and the exploration of my academic interests.
Travis McGuire and Dr. David Adamson, for their countless hours of help, seemingly
limitless supply of knowledge and insight, and deft touch with a red pen.
Dr. Loren Raun, for her many hours spent with me teaching me environmental
statistics first-hand.
Dr. Mason Tomson for serving on my committee.
GSI Environmental, Inc. and all of the wonderful people I had the pleasure of meeting
and working with on this project.
The great people in the Bedient lab group who have made these two years educational
and enjoyable.
This project was funded by ESTCP through Project ER-1120 “Development of an
Expanded, High-Reliability Cost and Performance Database for In-Situ Remediation
Technologies,” Lead Organization: GSI Environmental Inc., Houston, Texas
Contents
Acknowledgments ............................................................................................................ iii
Contents ............................................................................................................................ iv
List of Figures .................................................................................................................. vii
List of Tables .................................................................................................................... ix
List of Equations .............................................................................................................. xi
Nomenclature .................................................................................................................. xii
Introduction ....................................................................................................................... 1
1.1. Chlorinated Solvents ................................................................................................ 1
1.1.1. Overview ............................................................................................................ 1
1.1.2. Chlorinated Solvent Remediation ...................................................................... 3
1.1.2.1. Health Issues ............................................................................................... 3
1.1.2.2. Chemical and Physical Properties Affecting Remediation ......................... 3
1.1.2.3. Biodegradation of CVOCs .......................................................................... 6
1.1.2.4. Matrix Diffusion ......................................................................................... 7
1.2. CVOC Site Remediation Technologies .................................................................... 8
1.2.1. Pump and Treat .................................................................................................. 8
1.2.2. In-Situ Remediation Technologies .................................................................... 9
1.3. Treatment Performance and Sustained Treatment ................................................. 10
Motivation and Objectives ............................................................................................. 12
2.1. Research Motivation .............................................................................................. 12
2.2. Research Objectives ............................................................................................... 13
Literature Review ........................................................................................................... 17
3.1. Introduction ............................................................................................................ 17
3.2. Chlorinated Solvent Biodegradation and the Processes Involved .......................... 18
3.2.1. Fermentation of the Carbon Substrate ............................................................. 18
3.2.2. Anaerobic Reductive Dechlorination .............................................................. 18
3.2.2.1. Process and Pathways ............................................................................... 18
3.2.2.2. Microorganisms Capable of Reductive Dechlorination ............................ 20
3.2.2.3. Effects on Aqueous CVOCs and DNAPL Mass ....................................... 22
3.2.2.4. Influence of Hydrogen in Reductive Dechlorination ................................ 23
3.2.3. Other Degradation Pathways ........................................................................... 23
v

3.2.4. Daughter Product Accumulation ..................................................................... 24
3.3. Enhanced Anaerobic Bioremediation Implementation .......................................... 25
3.3.1. Overview of EAB ............................................................................................ 25
3.3.2. Biostimulation .................................................................................................. 26
3.3.2.1. Biostimulation Process .............................................................................. 26
3.3.2.2. Biostimulation Purpose ............................................................................. 27
3.3.3. Bioaugmentation .............................................................................................. 29
3.3.4. EAB Remediation Performance ...................................................................... 30
3.4. Sustained Treatment of Chlorinated Solvents ........................................................ 32
3.4.1. Sustained Treatment ........................................................................................ 32
3.4.2. Rebound ........................................................................................................... 34
3.4.3. Sustained Treatment and EAB ......................................................................... 36
3.4.3.1. Major Pathways for Sustained Treatment ................................................. 36
3.4.3.2. Endogenous Decay and Cryptic Growth ................................................... 36
Methodology .................................................................................................................... 40
4.1. Data Collection ....................................................................................................... 40
4.2. Data Set Description ............................................................................................... 44
4.3. EAB Performance Calculations: Percent Reduction and OoMs ............................ 47
4.4. Statistical Methods for Evaluating Sustained Treatment ....................................... 50
4.4.1. Hypothesis Tests .............................................................................................. 50
4.4.2. Mann-Kendall Trend Analysis ........................................................................ 51
4.4.3. Decay Rate Calculations .................................................................................. 52
4.4.4. Association Tests ............................................................................................. 53
Results and Discussion .................................................................................................... 54
5.1. EAB Performance and Evidence of Sustained Treatment ..................................... 54
5.1.1. Parent CVOC Concentrations .......................................................................... 54
5.1.2. Long-Term Performance Evaluation based on OoM Reduction ..................... 55
5.1.3. OoM Reduction Comparison During Post-Treatment ..................................... 59
5.1.4. OoM Reduction over Time .............................................................................. 63
5.2. Investigation of Parent CVOC Rebound ................................................................ 69
5.2.1. Parent CVOC Rebound in Wells ..................................................................... 69
5.2.2. Statistical Analysis of Parent CVOC Rebound ............................................... 75
5.3. Other Tests of Sustained Treatment of CVOCs ..................................................... 78
vi

5.3.1. Mann-Kendall Test .......................................................................................... 78
5.3.2. Decay Rate Comparison .................................................................................. 80
5.4. Association Tests for Sustained Treatment and Site Characteristics ..................... 82
5.4.1. Comparative Association ................................................................................. 82
5.4.2. SAS Association Tests ..................................................................................... 89
5.5. Total CVOCs .......................................................................................................... 91
5.6. Vinyl Chloride ........................................................................................................ 93
Conclusion and Future Work ........................................................................................ 95
6.1. Conclusions and Future Work ................................................................................ 95
References ...................................................................................................................... 100
Appendix A .................................................................................................................... 109
Appendix B .................................................................................................................... 110
List of Figures
Figure 1.1. - Hypothetical DNAPL contaminated site and the movement through the
subsurface ........................................................................................................................... 5
Figure 1.1.2- Pathway of degradation for PCE via reductive dechlorination ..................... 7
Figure 2.1 – Hypothetical case of rebound and sustained treatment. ............................... 16
Figure 3.1 - Pathway of degradation for PCE via reductive dechlorination ..................... 19
Figure 3.2 – Example of the sustained treatment potential from EAB treatment ............. 33
Figure 3.3 – Normalized temporal concentration records for chemical oxidation sites (a)
and EAB sites (b) with to the initial concentration measurement and time of initial
treatment ........................................................................................................................... 35
Figure 3.4 – Illustrative example of endogenous decay, starting with the injection of an
organic substrate for biomass growth) .............................................................................. 37
Figure 5.1 - Parent CVOC OoM reduction to the end of post-treatment .......................... 57
Figure 5.2 – Site-wide parent CVOC OoM reduction with respect to the drinking water
MCL for PCE and TCE..................................................................................................... 58
Figure 5.3 – Comparison of the distribution of site-wide CVOC OoM reduction to the
beginning and the end of post-treatment. .......................................................................... 60
Figure 5.4 – Change in site-wide parent CVOC OoM reduction during post-treatment
with respect to the drinking water MCL. .......................................................................... 62
Figure 5.5 - Comparison of site-wide parent CVOC OoM reduction throughout the whole
post-treatment monitoring period. .................................................................................... 64
Figure 5.6 – Distribution of site-wide CVOC OoM reduction separated by post-treatment
time frame ......................................................................................................................... 66
Figure 5.7 – Comparison of parent CVOC reduction thoughout the whole post-treatment
monitoring period, separated by post-treatment time frame. ............................................ 68
Figure 5.8 – Individual well response to EAB, normalized to the first measurement post-
treatment. .......................................................................................................................... 71
viii

Figure 5.9 – Histogram of Parent CVOC percent reduction at individual wells .............. 72
Figure 5.10 – Histogram of site-wide parent CVOC percent reduction ........................... 73
Figure 5.11 – Distribution of the site-wide percent reduction of Parent CVOCs during the
post-treatment time period ................................................................................................ 74
Figure 5.12 – Year by year site-wide percent reduction from the first year of post-
treatment for parent CVOCs. ............................................................................................ 75
Figure 5.13 – Site-weighted Mann-Kendall Trend test results for parent CVOCs. .......... 80
Figure 5.14 – Comparison of the change of OoM reduction distribution for wells where
cis-DCE did, or did not, exceed 0.1 mg/L during Pre-treatment. ..................................... 83
Figure 5.15 – Comparison of the change of OoM reduction distribution for wells where
VC did, or did not, exceed 0.1 mg/L during Pre-treatment. ............................................. 84
Figure 5.16 – Comparison of OoM reduction distribution for five general soil types. .... 86
Figure 5.17 – Comparison of the change in distribution of well OoM reduction for five
general soil types ............................................................................................................... 88
Figure 5.18 – Comparison of the distribution of site-wide Total CVOC OoM reduction 92
Figure 5.19 – Comparison of the distribution of site-wide VC OoM reduction ............... 94
List of Tables
Table 1.1 - Characteristics of Chlorinate Volatile Organic Compounds ............................ 4
Table 3.1- Examples of CVOC Half Reactions ................................................................ 19
Table 3.2 - Potential Degradation Processesfor Chlorinated Solvents ............................. 25
Table 3.3 – Common Biostimulation Substrates .............................................................. 27
Table 4.1- Site Parameters Recorded ................................................................................ 42
Table 4.2 - Summary of Source Depletion Sites ............................................................... 45
Table 4.3 - Description of Lengths of Given Monitoring Periods (years) ........................ 46
Table 4.4 - Sites with Other CVOC Treatments Applied ................................................. 47
Table 4.5 - Example Pre- and Post-Treatment Concentrations and Equivalent Percent
Reduction and OoM Reduction ........................................................................................ 49
Table 4.6 - Mann-Kendall Weighting for Wells ............................................................... 52
Table 4.7 - Mann-Kendall Weighting for Sites ................................................................ 52
Table 5.1 – Distribution of Geometric Mean (Geomean) Parent CVOC Concentrations
(Conc.) During Different Monitoring Periods .................................................................. 55
Table 5.2 - Example Calculation of Long-Term Performance Metric .............................. 56
Table 5.3 - Evaluation of Rebound at EAB Sites ............................................................. 70
Table 5.4 - Description of Outliers Removed for Statistical Analysis ............................. 77
Table 5.5 - Hypothesis Test Results ................................................................................. 78
Table 5.6 - Mann-Kendal trend analysis for parent CVOC concentrations at individual
wells .................................................................................................................................. 79
Table 5.7 - Median Site-Wide Estimated Decay Rate for Parent CVOCs (n = 21 sites).. 81
Table 5.8 - Median Site-Wide Estimated Decay Rate for Parent CVOCs During
Monitoring Period, R2 > 0.5 (n = 7 sites) .......................................................................... 81
x

Table 5.9 - Estimated Soil Types ...................................................................................... 85
Table 5.10 – Results from SAS linear regression tests ..................................................... 90
Table 6.1 - Results and Sustained Treatment .................................................................... 97