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Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents

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Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents FINAL Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents August 2004 This page intentionally left blank PRINCIPLES AND PRACTICES OF ENHANCED ANAEROBIC BIOREMEDIATION OF CHLORINATED SOLVENTS August 2004 Prepared for: Air Force Center for Environmental Excellence Brooks City-Base, Texas Naval Facilities Engineering Service Center Port Hueneme, California and Environmental Security Technology Certification Program Arlington, Virginia This page intentionally left blank ACKNOWLEDGEMENTS The Parsons Corporation (Parsons) prepared this Principles and Practices document under contract to the Air Force Center for Environmental Excellence (AFCEE, Contract F41624-00- D-8024) and the Naval Facilities Engineering Service Center (NFESC, Contract N47408-98- D-7527). The NFESC contract was funded by the Environmental Security Technology Certification Program (ESTCP). The United States Army Corp of Engineers (USACE) assisted with technical review. This document is intended to assist AFCEE, NFESC, ESTCP, USACE and their United States (US) Department of Defense (DoD) technology-transition partners in evaluating and applying enhanced in situ anaerobic bioremediation for restoration of groundwater contaminated with chlorinated solvents. The authors acknowledge the assistance of numerous individuals who provided review services, and to several environmental contractors that provided case studies and information regarding respective areas of expertise. These individuals and their affiliations are listed in Appendix A. - i - 022/738863/28.doc DISCLAIMER In no event shall either the United States Government or Parsons have any responsibility or liability for any consequences of any use, misuse, inability to use, or reliance on the information contained herein; nor does either warrant or otherwise represent in any way the accuracy, adequacy, efficacy, or applicability of the contents hereof. Mention of trade names in this report is for information purposes only; no endorsement is implied. - ii - 022/738863/28.doc TABLE OF CONTENTS Page ACKNOWLEGEMENTS ....................................................................................................i DISCLAIMER.....................................................................................................................ii SECTION 1 - STATE OF THE PRACTICE ...................................................................1-1 1.1 Problem Statement................................................................................................1-1 1.2 Objective...............................................................................................................1-2 1.2.1 Intended Audience....................................................................................1-3 1.2.2 Using the Principles and Practices Document..........................................1-3 1.3 Roadmap to Enhanced In Situ Anaerobic Bioremediation...................................1-4 1.4 Technology Description.......................................................................................1-6 1.4.1 Remedial Objectives and Regulatory Acceptance .....................................1-7 1.4.2 Applicable Contaminants (Chlorinated Solvents)....................................1-7 1.4.3 Degradation Processes..............................................................................1-8 1.4.4 Anaerobic Reductive Dechlorination .......................................................1-9 1.4.5 Molecular Hydrogen as a Direct Electron Donor...................................1-11 1.4.6 Microbiology of Anaerobic Reductive Dechlorination..........................1-12 1.5 Application of Enhanced Anaerobic Bioremediation.........................................1-12 1.5.1 Technology Screening............................................................................1-13 1.5.2 Substrate (Electron Donor) Alternatives ................................................1-14 1.5.3 System Configurations...........................................................................1-16 1.5.4 Delivery Options....................................................................................1-19 1.6 Alternative Remedial Strategies.........................................................................1-20 1.7 Advantages and Limitations of Enhanced Anaerobic Bioremediation ..............1-21 1.7.1 Advantages of Enhanced Anaerobic Bioremediation.............................1-21 1.7.2 Potential Limitations of Enhanced Anaerobic Bioremediation..............1-22 1.8 Summary.............................................................................................................1-23 SECTION 2 - MICROBIOLOGICAL AND GEOCHEMICAL CONSIDERATIONS ..2-1 2.1 Microbial Processes and Degradation Pathways..................................................2-2 2.1.1 Degradation Processes for Chlorinated Solvents .....................................2-2 2.1.2 Anaerobic Reductive Dechlorination .......................................................2-2 2.1.3 Native Electron Acceptors and Oxidation-Reduction Conditions ...........2-5 2.1.4 Fermentation Reactions and Molecular Hydrogen...................................2-6 2.1.4.1 Fermentation............................................................................2-7 - iii - 022/738863/28.doc TABLE OF CONTENTS (Continued) Page 2.1.4.2 Donor-Specific Fermentation Reactions .................................2-7 2.1.4.3 Molecular Hydrogen as an Electron Donor.............................2-8 2.1.4.4 Stoichiometric Relationships.................................................2-11 2.1.5 Alternate Degradation Processes............................................................2-12 2.1.5.1 Oxidative Pathways...............................................................2-12 2.1.5.2 Abiotic Pathways...................................................................2-13 2.1.6 Relative Rates of Degradation................................................................2-14 2.2 Microbial Communities Required for Anaerobic Reductive Dechlorination ....2-16 2.2.1 The Role and Occurrence of Dehalococcoides Microorganisms...........2-17 2.2.2 Microbial Ecology..................................................................................2-19 2.2.3 Occurrence and Site-Specific Variability...............................................2-19 2.2.4 Environmental Requirements .................................................................2-20 2.2.5 Reasons for Apparent/Actual DCE Stall or Slowdown........................2-21 2.2.6 Bioaugmentation.....................................................................................2-22 2.3 Effects of Substrate Addition on DNAPL and Sorbed Contaminant Mass........2-23 SECTION 3 - PRELIMINARY SCREENING ................................................................3-1 3.1 Remedial Objectives and Regulatory Considerations For Enhanced Anaerobic Bioremediation....................................................................................3-2 3.1.1 Remedial Objectives...................................................................................3-2 3.1.2 Regulatory Considerations .........................................................................3-3 3.2 Conceptual Site Models........................................................................................3-4 3.2.1 Classification System for Chlorinated Solvent Plumes............................3-6 3.2.1.1 Type 1 Environment: Groundwater Systems that are Highly Anaerobic due to High Levels of Organic Carbon ..................3-6 3.2.1.2 Type 2 Environment: Systems that are Mildly Anaerobic due to Moderate Levels of Organic Carbon ............................3-7 3.2.1.3 Type 3 Environment: Aerobic Systems with Low Levels of Organic Carbon........................................................................3-8 3.2.1.4 Mixed Environments and Sequential Anaerobic/Aerobic Degradation..............................................................................3-8 3.3 Site Screening Technical Considerations.............................................................3-9 3.3.1 Contaminant Distribution.......................................................................3-10 3.3.2 Microbiology ..........................................................................................3-11 3.3.3 Hydrogeology.........................................................................................3-12 3.3.4 Groundwater Geochemistry....................................................................3-13 3.4 Potential Adverse Impacts..................................................................................3-15 3.4.1 Water Quality.........................................................................................3-15 3.4.1.1 Mobilization of CAHs ...........................................................3-15 3.4.1.2 Secondary Water Quality Issues............................................3-16 3.4.2 Generation of Volatile Byproducts and Noxious Gases.........................3-18 3.5 Proceeding with Enhanced Anaerobic Bioremediation......................................3-18 - iv - 022/738863/28.doc TABLE OF CONTENTS (Continued) Page SECTION 4 - PRE-DESIGN............................................................................................4-1 4.1 Evaluating Existing Data......................................................................................4-3 4.1.1 Reviewing Field Data for Anaerobic Biodegradation Potential...............4-4 4.1.2 Geochemical
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