Dense Nonaqueous Phase Liquids (DNAPLs)Chromium VI
Dense Nonaqueous Phase Liquids (DNAPLs)
1,4-Dioxane
Mercury
MTBE
Perchlorate
POPs
PCBs
TCE
Other Contaminants
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Treatment Technologies
Bioremediation
Biological treatment involves the use of microorganisms to degrade or facilitate the degradation of chemicals. Many naturally occurring microorganisms (typically, heterotrophic bacteria and fungi) can transform hazardous chemicals to substances that may be less hazardous than the original compounds. A layman's discussion of these processes can be found in A Citizens Guide to Bioremediation
. Additional information on different bioremediation approaches for a wide range of contaminants can be found in Technology Focus.
Contaminant breakdown by microbes occurs under both aerobic and anaerobic conditions and is accomplished in two ways at contaminated sites: intrinsic biodegradation and enhanced bioremediation. Intrinsic biodegradation depends on indigenous microorganisms to degrade contaminants without any amendments. In enhanced bioremediation, biodegradation is facilitated by manipulating the microbial environment though addition of amendments (biostimulation), such as air, organic substrates, nutrients, and other compounds whose absence limits treatment, or by adding the microbial cultures (bioaugmentation) necessary to degrade the specific target chemicals.
For most DNAPL chemicals, biodegradation will not occur at the surface of a residual or pool. The chemicals are degraded in the vapor or dissolved state; however, many degrading microbes can exist in the presence of very high concentrations of gaseous or dissolved-phase DNAPL chemicals. The degradation activities of these microbes near the surface of the residual or pool create a much steeper concentration gradient than would exist without them and result in a higher dissolution rate of the NAPL. Although pools of DNAPL are not likely to biodegrade in a short time frame, evidence from laboratory studies indicates that dissolution rates of residual DNAPL can be increased through anaerobic bioremediation.
While not relevant to a discussion of bioremediation, natural subsurface degradation also can occur through abiotic reactions, such as hydrolysis or reaction with metal sulfides.
4.2 Enhanced Bioremediation (In Situ Soil Remediation Technology)
Remediation Technologies Screening Matrix and Reference Guide, Version 4.0.
Federal Remediation Technologies Roundtable, 2003
4.33 Co-Metabolic Processes (In Situ Ground Water Remediation Technology)
Remediation Technologies Screening Matrix and Reference Guide, Version 3.0.
Federal Remediation Technologies Roundtable, 1997
Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
U.S. EPA, Office of Research and Development.
EPA 625-R-06-015, 22 pp, 2006
Discusses in situ and ex situ biodegradation processes and provides a technology selection factors section.
Enhanced Attenuation: A Reference Guide on Approaches to Increase the Natural Treatment Capacity of a System
T. Early, B. Borden, M. Heitkamp, B.B. Looney, D. Major, W.J. Waugh, G. Wein, T. Wiedemeier, K.M. Vangelas, K.M. Adams, and C.H. Sink.
WSRC-STI-2006-00083, Rev 1, 161 pp, 2006
Covers the following EA approaches: (1) hydraulic manipulation to reduce contaminant infiltration using low-permeability barriers, diffusion barriers, covers, encapsulation, and diversion of electron acceptors; (2) passive residual source reduction (e.g., bioventing); (3) increase in system attenuation capacity via biological processes, such as bioaugmentation, biostimulation, and wetlands development and other plant-based methods; (4) abiotic and biologically mediated abiotic attenuation methods; and (5) reactive barriers.
Final Evaluation of Performance and Costs Associated with Anaerobic Dechlorination Techniques, Phase I Site Survey, Revision 02
Environmental Security Technology Certification Program (ESTCP), 135 pp, 2002
Provides an in-depth overview of substrates used to bring about anaerobic degradation of contaminants.
Ground Water Issue: Calculation and Use of First Order Rate Constants for Monitored Natural Attenuation Studies
C. Newell, et al.
EPA 540-S-02-500, 28 pp, 2002
Addresses the use of first-order rate constants to estimate plume trends and the time required for achieving remediation goals.
Ground Water Issue: Microbial Processes Affecting Monitored Natural Attenuation of Contaminants in the Subsurface
A. Azadpour-Keeley, H. Russell, and G. Sewell.
EPA 540-S-99-001, 20 pp, 1999
Presents a brief overview of bioremediation processes and the conditions needed for different contaminants to be biodegraded.
In Situ Bioremediation Technologies: Experiences in the Netherlands and Future European Challenges
A. Langenhoff.
EuroDemo, 21 pp, 2007
The author discusses five different approaches to in situ bioremediation: bioventing, biosparging, bioaugmentation, monitored natural attenuation, and enhanced bioremediation/enhanced natural attenuation. Four brief case studies describe implementation of enhanced bioremediation/enhanced natural attenuation at sites in the Netherlands. The cases cover reductive dechlorination of PCE, cis-DCE, and HCH, respectively, plus anaerobic oxidation of BTEX.
Methodology for Estimating Times of Remediation Associated with Monitored Natural Attenuation
F.H. Chapelle, M.A. Widdowson , J.S. Brauner, E. Mendez III, and C.C. Casey.
U.S. Geological Survey Water-Resources Investigations Report 03-4057, 58 pp, 2003
Outlines a method for estimating timeframes required for natural attenuation processes, such as dispersion, sorption, and biodegradation, to lower contaminant concentrations and mass to predetermined regulatory goals in groundwater systems.
Performance Monitoring of MNA Remedies for VOCs in Ground Water
D. Pope, S. Acree, H. Levine, S. Mangion, J. van Ee, K. Hurt, and B. Wilson.
EPA 600-R-04-027, 92 pp, 2004
Designed to be used during preparation and review of long-term monitoring plans for sites where MNA has been or may be selected as part of the remedy. Performance monitoring system design depends on site conditions and site-specific remedial objectives; this document provides information on technical issues to consider during the design process.
Technology Overview Report: In Situ Bioremediation
L. van Cauwenberghe and D. Roote.
Ground-Water Remediation Technologies Analysis Center, 24 pp, 1998
Summarizes the general principles and techniques of bioremediation, discusses the applicability of the technology, and reports advantages and limitations.
Use of Bioremediation at Superfund Sites
U.S. EPA, Office of Solid Waste and Emergency Response.
EPA 542-R-01-019, 60 pp, 2001
Focuses on the use of enhanced bioremediation technologies at 104 Superfund remedial action sites and other contaminated sites. Provides a snapshot of current applications of bioremediation and presents trends over time concerning selection and use of the technology, contaminants and site types treated, and cost and performance.
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Last updated on Thursday, July 24, 2008