U.S. EPA Contaminated Site Cleanup Information (CLU-IN)


U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

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 BioremediationAdobe PDF Logo. 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.


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General Resources | Performance Monitoring for Bioremediation

General Resources

4.2 Enhanced Bioremediation (In Situ Soil Remediation Technology)
Remediation Technologies Screening Matrix and Reference Guide, Version 4.0.
Federal Remediation Technologies Roundtable, 2003

3.9 In Situ Biological Treatment for Ground Water, Surface Water, and Leachate
Remediation Technologies Screening Matrix and Reference Guide, Version 3.0.
Federal Remediation Technologies Roundtable, 1997

Adobe PDF LogoBiodegradability of Chlorinated Solvents and Related Chlorinated Aliphatic Compounds
Field, J.A. and R. Sierra-Alvarez.
Euro Chlor, 98 pp, 2004

Development of Assessment Tools for Evaluation of the Benefits of DNAPL Source Zone Treatment
L.M. Abriola, P. Goovaerts, K.D. Pennell, and F.E. Loeffler.
SERDP Project ER-1293, 173 pp, 2008

This report details the results of work that has enhanced the understanding of significant mechanisms controlling DNAPL source zone behavior and describes lessons learned that can provide improved DNAPL site management strategies. It discusses 4 important concepts: (1) partial source-zone mass removal can result in substantial local concentration and mass flux reductions; (2) potential remediation efficiency is closely linked to source-zone architecture (ganglia-to-pool ratios); (3) biostimulation and bioaugmentation approaches are feasible for treatment of DNAPL source zones; and (4) the uncertainty in mass discharge ([M/T]) estimates can be quantified through application of geostatistical methods to field measurements.

Adobe PDF LogoEngineering 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.

Adobe PDF LogoEnhanced 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.

Adobe PDF LogoFinal 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.

Adobe PDF LogoGround 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.

Adobe PDF LogoGround 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.

Adobe PDF LogoGuidance Protocol: Application of Nucleic Acid-Based Tools for Monitoring Monitored Natural Attenuation (MNA), Biostimulation, and Bioaugmentation at Chlorinated Solvent Sites
ESTCP Project ER-0518, 34 pp, 2011

This protocol summarizes the current state of the practice of molecular biological tools (MBTs), specifically nucleic-acid based tools commercially available to identify relevant Dehalococcoides bacteria. It is intended to provide a technically sound and practical approach to MBT use. This document provides recommendations regarding sampling approaches and criteria in evaluation of data for use in bioremediation decision making. See also the Project ER-0518 Final ReportAdobe PDF Logo and the ESTCP Cost and Performance ReportAdobe PDF Logo.

Adobe PDF LogoIn 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.

Adobe PDF LogoLoading Rates and Impacts of Substrate Delivery for Enhanced Anaerobic Bioremediation
B. Henry.
ESTCP Project ER-0627, 476 pp, 2010

The author evaluated 15 case studies of different substrates used to stimulate biodegradation of chlorinated compounds: Hydrogen Release Compounds (HRC and HRC-X), vegetable oil (neat and emulsified), whey, molasses, ethanol and lactate, and mulch in permeable biowalls. This report discusses the factors that limit enhanced in situ bioremediation and describes (in Appendix B) a Substrate Design Tool developed in Microsoft Excel to assist the practitioner in evaluating a site for an application of enhanced in situ bioremediation. Substrate Design Tool; ESTCP Cost & Performance ReportAdobe PDF Logo; 2010 AddendumAdobe PDF Logo

Adobe PDF LogoA Low-Cost, Passive Approach for Bacterial Growth and Distribution for Large-Scale Implementation of Bioaugmentation
Trotsky, J., R.A. Wymore, M.R. Lamar, and K.S. Sorenson.
ESTCP Project ER-200513, TR-2354-ENV, 585 pp, 2010

The relative pros and cons of active recirculation and low-cost, passive inject-and-drift strategies for large-scale bioaugmentation of TCE in groundwater were evaluated in a side-by-side comparison at the Seal Beach Naval Weapons Station, Seal Beach Site 70, CA. The active and passive approaches were compared in a full-scale TCE source area application. Electron donor was added weekly for the active cell and monthly for the passive cell. After several months of pre-conditioning, a commercially available culture was added. Overall, bacterial growth and dechlorination performance was similar using both approaches, but the active system was more costly. ESTCP Cost and Performance ReportAdobe PDF Logo

Adobe PDF LogoMethodology 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.

Adobe PDF LogoPerformance 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.

Adobe PDF LogoTechnology 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.

Adobe PDF LogoUse 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.

The Use of Molecular and Genomic Techniques Applied to Microbial Diversity, Community Structure, and Activities at DNAPL and Metal-Contaminated Sites: Environmental Research Brief
Azadpour-Keeley, A., M.J. Barcelona, K. Duncan, and J.M. Suflita.
EPA 600-R-09-103, 19 pp, Sep 2009

Subsurface microbial communities will respond both to the presence of contaminants, which can be detected during characterization, and to the engineered manipulation of subsurface conditions, which can be monitored during remediation. This Brief provides a background on classic molecular and genomic sciences and discusses the results and interpretation of their application to field-scale subsurface remediation activities.

Performance Monitoring for Bioremediation

There are three broad types of bioremediation actions:

  • Monitored natural attenuation (MNA), where natural conditions are sufficient to degrade the contaminants of concern (COCs);
  • Addition of nutrients (biostimulation) where the bacteria necessary to degrade the COCs are present but conditions do not favor their growth (e.g., anaerobic bacteria in an aerobic aquifer, aerobic bacteria in an anaerobic aquifer, lack of appropriate nutrients); and
  • Addition of microorganisms (bioaugmentation) where the bacteria necessary to degrade the COCs do not occur naturally at the site or occur at too low a population density to be effective.

Additional information on these processes is available at the beginning of this Bioremediation page.

Table 1 provides a menu of performance monitoring parameters for chlorinated aliphatics, most of which degrade best under anaerobic conditions. The table describes what each parameter is used for and a recommended frequency of analysis. To promote biodegradation of these DNAPLs in groundwater, it often is necessary to provide an amendment that first enhances aerobic growth, which depletes the oxygen supply, and then acts as an electron donor to stimulate anaerobic activity and the destruction of the chlorinated aliphatics (ITRC 2008). For the amendment to be completely effective, it needs to permeate the entire affected subsurface area. Downgradient pumping can be used to assist in spreading the amendment, but it is subject to preferential flow patterns. Performance monitoring with geophysical techniques, such as cross-borehole radar and electrical resistivity tomography, have been used to identify potential amendment bypass areas that might need special attention. Electron donor tracers will not be needed for MNA.

Table 2 provides a menu of performance parameters for DNAPLs that preferentially degrade under aerobic conditions. Typically in aerobic degradation involving a source zone, the area around the source quickly becomes anaerobic, and a series of different redox areas is established downgradient from the source, with aerobic degradation occurring at the perimeter of the dissolved contaminant plume (EPA 2000). If the contaminant is not very amenable to anaerobic degradation and bioremediation is chosen as the remedial technology, the addition of an oxidant (e.g., air, oxygen) generally will be needed to keep the aquifer/source zone aerobic, and dispersion of the oxidant should be monitored. The references used to develop Table 2 are directed at the remediation of petroleum hydrocarbons, which degrade preferentially under aerobic conditions. The use of these references was deemed appropriate because the approaches used to monitor natural attenuation or degradation progress when chemical oxidants are employed are very similar for LNAPL and DNAPL source zones and dissolved plumes. DNAPLs that can be degraded aerobically include coal tars, creosote, No. 6 fuel oil (bunker C), hexachlorobutadiene, methylene chloride, and nitrobenzene.

Remedial progress or success with DNAPL mass removal also can be estimated using flux techniques and tracers. For nonspecific performance monitoring techniques that might be useful, see Remediation Measurement Tools.

Note that both of the tables provide a comprehensive listing of parameters that can be used to understand the type of biodegradation that is taking place and under what kind of geochemical conditions, as well as whether degradation is occurring. The types of information needed and their associated parameters should be determined in the site-specific data quality objectives process. A bare-bones approach to anaerobic biodegradation in groundwater might be to monitor for parameters that can be obtained with flow-through cells (e.g., oxidation reduction potential, pH, dissolved oxygen, specific conductance, and chloride) plus total organic carbon. The main problem with this approach is that it does not provide diagnostic information should the indicator parameters show that the remediation is not proceeding favorably.

Table 1. Performance Monitoring Parameters for Biodegradation of DNAPL Chemicals: Anaerobic Route

Performance Parameter

Method

Data Use

Performance Expectation

Recommended Frequency of Analysis

Chlorinated Aliphatic Hydrocarbons (CAHs)

EPA SW-846: 8260B (laboratory)

Field gas chromatography (GC) or GC/mass spectroscopy (MS)

Regulatory compliance for COCs, the values by which success of the remediation system will be measured.

CAHs and dechlorination products typically are expected to decline to below regulatory compliance levels within the treatment zone after substrate addition.

Baseline and recommended for each groundwater sampling round.

Methane, Ethane, Ethene

EPA SW-846: 5021A

Robert S. Kerr Laboratory RSK-175 SOP followed by GC or GC/MS

Elevated levels of methane indicate fermentation is occurring in a highly anaerobic environment and that reducing conditions are appropriate for anaerobic dechlorination of CAHs. Elevated levels of ethene and ethane (at least an order of magnitude greater than background levels) can be used to infer anaerobic dechlorination of CAHs.

Methane levels >1.0 mg/L are desirable but not required for dechlorination to occur. Methane levels <1.0 mg/L and the accumulation of cis-1,2-DCE, VC, or other CAHs could indicate that additional substrate is required to shift reducing conditions into an environment suitable for reduction of these compounds. If elevated levels of ethene or ethane are not observed, potential accumulation of cis-1,2-DCE or VC should be monitored.

Recommended for each sampling round. Might require analysis by a specialty laboratory.

Total Organic

Carbon/Dissolved Organic Carbon (TOC/DOC)

EPA SW-846: 9060A

APHA et al. 1992: 5310 B, C, or D

Indicator of natural organic carbon present at site during baseline characterization and as an indicator of substrate distribution during performance monitoring. TOC/DOC concentrations >20-50 mg/L are desired in the anaerobic treatment zone.

Stable or declining TOC/DOC levels <20 mg/L in conjunction with elevated levels of VOCs and alternate electron acceptors indicate additional substrate is required to sustain the anaerobic treatment zone.

Baseline and recommended for each sampling event.

Dehalococcoides ethogenes (DHE) or other appropriate microorganism

Quantified by quantitative polymerase chain reaction.- specialist laboratory

Determine presence of DHE or other appropriate microorganism at baseline periods after bioaugmentation.

DHE or other appropriate microorganism will be detected and increase as a consequence of adding electron donor to create anaerobic conditions or increase after inoculation with DHE or other appropriate microorganism-containing culture.

Baseline prior to injection and quarterly based on the numbers achieved. Once a high titer is measured and growth is ensured, the test can be continued but is not critical

Ammonia

APHA et al. 1992: 4500-NH3 C, D, E, F

Ion-selective electrode1 (ISE) method can be used in the field

Ammonia can represent a form of biologically available nitrogen.

Indicator parameter only.

Baseline.

Nitrate

EPA Method 300.1 or SW-846: 9056A  (laboratory- based ion chromatography methods) 

ISE can be used in the field.

Nitrate is an alternate electron acceptor for microbial respiration in the absence of oxygen. Depleted levels of nitrate (relative to background) indicate that the groundwater environment is sufficiently reducing nitrate.

Indicator parameter. Nitrate level <1.0 mg/L is desirable for anaerobic ISB.

Optional and troubleshooting. Recommended for each sampling event if nitrate reduction appears to be a significant terminal electron accepting process (TEAP).

Nitrite

EPA 300.1 or SW-846: 9056A (laboratory)

In most aquifers the concentration of nitrate is naturally much higher than nitrite, and total nitrate/nitrite can be used as an estimate of nitrate.

Indicator parameter.

Optional and troubleshooting. Alternative method.

Manganese (Mn) 

EPA SW-846: 6010C (laboratory) or Hach Method 8034 (field)

Mn(IV) is an alternate electron acceptor for microbial respiration in the absence of oxygen and nitrate. An increase in dissolved Mn(II) or total manganese indicates that the groundwater environment is sufficiently reducing to sustain Mn reduction and for anaerobic dechlorination to occur.

Elevated levels of dissolved Mn could indicate a competing TEAP to anaerobic dechlorination of CAHs.

Optional. Recommended for each sampling event only if manganese reduction appears to be a significant TEAP.

Major Cations (Ca, Mg, Na, K)

EPA SW-846: 6010C

ISE can be used in the field.

Major cations along with major anions are good general groundwater chemistry parameters and are inexpensive to analyze.

Only as a check if the system is not working as planned.

Baseline and as needed in subsequent sampling events.

Ferrous Iron (Fe[II])

APHA et al. 1992: 3500-Fe D

Colorimetric Hach Method 8146 (field)

Ferric iron is an alternate electron acceptor for microbial respiration in the absence of oxygen and nitrate. Reduction of ferric iron produces ferrous iron. Elevated levels of ferrous iron indicate that the groundwater environment is sufficiently reducing to sustain iron reduction and for anaerobic dechlorination to occur.

Elevated levels of ferrous iron can indicate a competing TEAP to anaerobic dechlorination of CAHs.

Recommended for each sampling round. Typically measured at the well head to protect samples from exposure to oxygen.

Biologically Available Iron

(Fe[III])

Laboratory specialty method (laboratory)

Bioassay with quantification of bioavailable solid-phase ferric iron Fe(III), which is a competing electron acceptor. Optional method that can be used to determine competition from iron reduction. Might also affect potential abiotic reactions.

Recommended only for clastic sediments with potential for significant iron concentrations. Also can be used as a diagnostic tool if sulfate reduction or methanogenic redox conditions cannot be achieved.

Optional at initial sampling.

Sulfate (SO4)-2

EPA Method 300.1, SW-846: 9056A (ion chromatography) and SW-846 Methods 9035, 9036, and 9038 (colorimetric and turbidimetric methods) (laboratory)

Hach Method 8051 (field)

Sulfate is an alternate electron acceptor for microbial respiration in the absence of oxygen, nitrate, Mn, and ferric iron. Depleted concentrations of sulfate relative to background indicate that the groundwater environment is sufficiently reducing to sustain sulfate reduction and for anaerobic dechlorination to occur.

Sulfate levels <20 mg/L are desirable but not required for anaerobic dechlorination to occur. High levels of sulfate in conjunction with the absence of TOC/DOC indicate additional substrate might be required to promote anaerobic dechlorination.

Recommend for baseline and each sampling round.

Sulfide

Hach Method 8131 or similar (field colorimetric method)

Field determination of sulfide can also be made by ISE.

By-product of sulfate reduction. Sulfide typically precipitates with iron minerals, but elevated levels of sulfide might be toxic to dechlorinating microorganisms.

Elevated levels of sulfide in conjunction with elevated levels of CAHs can indicate that iron compounds should be added to precipitate sulfides and reduce toxicity effects.

Optional. Recommended when elevated levels of sulfate (>20 mg/L) are present.

Hydrogen Sulfide

Soil gas analyzer calibrated in the field according to the manufacturer's specifications (field)

Useful for determining biological activity in vadose zone and generation of biogenic methane.

Explosive levels of noxious levels of hydrogen sulfide accumulating in structures or utilities can pose a health risk.

Optional. Recommended when soil vapor exposure pathway exists.

Bromide or Iodide

EPA Method 300.1 (laboratory) or ISE (field).

Used as a conservative groundwater tracer.

Indicator parameter for tracer tests.

Used only with tracer testing.

Carbon Dioxide

(CO2)

APHA et al. 1992: 4500-CO2  C (titrimetric) or 4500-CO2 D (calculation requiring known values for total alkalinity and pH)

ISE for field measurement

Carbon dioxide is a by-product of both aerobic and anaerobic degradation. Elevated levels of carbon dioxide indicate microbial activity has been stimulated.

Indicator parameter.

Optional.

pH

Field probe with direct-reading meter calibrated in the field according to the manufacturer's specifications (APHA et al. 1992: 4500-H+ B)

Biological processes are pH sensitive, and the ideal range of pH for dechlorinating bacteria is 5 to 9. Outside this range, biological activity is less likely to occur.

pH levels within a range of 5 to 9 are desirable. pH <5 indicates that a buffering agent might be required to sustain high rates of anaerobic dechlorination. Desorption toward phase equilibrium is the basis of dissolved CAH "rebound," which extends treatment duration.

Baseline and recommended for each sampling event.

Oxidation Reduction Potential (ORP)

Direct-reading meter, A2580B, or USGS A6.5 (field)

ORP of groundwater provides data on whether or not anaerobic conditions are present. Reducing conditions are required for anaerobic dechlorination of CAHs. Used in conjunction with other geochemical parameters to determine whether or not groundwater conditions are optimal for anaerobic biodegradation.

Positive ORP values (>0.0 mV) in conjunction with elevated levels of DO and the absence of TOC/DOC can indicate that additional substrate is required to promote anaerobic dechlorination.

Baseline and typically measured at the well head using a flow-through cell to protect samples from exposure to oxygen.

Dissolved Oxygen (DO)

DO meter calibrated in the field according to the manufacturer's specifications (APHA et al. 1992: 4500-G) (field)

DO should be depleted in an anaerobic bioremediation system. DO <0.5 mg/L generally indicates an anaerobic pathway suitable for anaerobic dechlorination to occur.

DO concentrations >1.0 mg/L in conjunction with elevated levels of CAHs and the absence of TOC/DOC indicate additional substrate might be required to promote anaerobic dechlorination.

Baseline and recommended for each sampling event. Typically measured at the well head using a flow-through cell.

Temperature

Field probe with direct-reading meter (APHA et al. 1992: 2550 B)

General water quality parameter used as a well purging stabilization indicator. Microbial activity is slower at lower temperatures.

Indicator parameter. Typically used as a well purge stabilization parameter.

Baseline and every subsequent sampling

Specific Conductance

EPA 120.1/SW-846: 9050A, direct-reading meter (laboratory or field)

General water quality parameter used as a well purging stabilization indicator. Can correlate with and support interpretations of other geochemical analyses.

Indicator parameter. Typically used as a well purge stabilization parameter.

Baseline and every subsequent sampling event.

Fraction of Organic Carbon (foc)

SW-846: 9060A modified for soil matrix (laboratory)

Fraction of organic carbon in the aquifer matrix is used to calculate retardation factors for dissolved contaminant transport and to estimate the amount of contaminant mass sorbed to the aquifer matrix.

A large portion of contaminant mass might be sorbed to the aquifer matrix.

Recommended at baseline sampling.

Volatile Fatty Acids (VFAs)

Laboratory specialty

method, EPA

Robert S. Kerr

Laboratory (RSK)–

SOP 112

VFAs are an indicator of substrate distribution and are also degradation products of more complex substrates (e.g., vegetable oils or carbohydrates). Fermentation of VFAs produces molecular hydrogen for anaerobic dechlorination.

Measurable concentrations of VFAs (>10-20 mg/L) are desirable in the treatment zone. The presence of mg/L concentrations of propionate or butyrate is considered favorable. Absence of measurable VFAs in conjunction with elevated levels of CAHs and alternate electron acceptors indicates additional substrate might be required to sustain the anaerobic treatment zone.

Optional. Useful as a troubleshooting parameter.

Alkalinity

APHA et al. 1992: 2320 B, or Hach alkalinity test kit model AL AP MG-L or Hach Method #8203 (field or laboratory)

ISE for field measurement

Indicator of biodegradation and the buffering capacity of the aquifer (neutralization of weak acids). Used in conjunction with pH. An increase in alkalinity and stable pH indicates the buffering capacity of the aquifer is sufficient to neutralize metabolic acids produced by degradation of substrates. Can also be used as measurement of salinity.

Concentrations of alkalinity that remain at or below background in conjunction with pH <5 indicates that a buffering agent could be required to sustain high rates of anaerobic dechlorination. High salinity conditions can inhibit microbiological activity.

Baseline and recommended for each sampling event.

Dissolved Phosphate

EPA 300.1 or SW-846: 9056A (ion chromatography -laboratory)

Nutrient needed for microbial growth. Might be needed as a substrate amendment

May indicate need for phosphate amendment.

Optional.

Chloride

EPA  Method 300.1 or SW-846: 9056A (laboratory methods),

Hach chloride test kit Model 8-P, or ISE for field measurements

General water quality parameter. Chloride is produced by anaerobic dechlorination of CAHs. Elevated levels of chloride can indicate that dechlorination is occurring if observed concentrations are greater than three times background and consistent with CAH molar concentrations.

Indicator parameter only.

Baseline and every subsequent sampling event.

1 Consult ISE manufacturer to determine if a site-specific condition could limit use.

Adapted from ITRC 2008.

Table 2. Performance Monitoring Parameters for Biodegradation of DNAPL Chemicals: Aerobic Route

Performance Parameter

Method

Data Use

Performance Expectation

Recommended Frequency of Analysis

Contaminants of Concern (COCs)

VOCs, EPA SW-846: 8260B

SVOCs, SW-846: 8270D. Other methods might be more appropriate depending upon the COC (e.g., SW-846: 8310 for PAHs and SW-846: 8330A for Nitro Aromatics).

Field GC or GC/MS might also be appropriate.

Regulatory compliance for COCs, the values by which success of the remediation system will be measured.

Contaminants are typically expected to decline to less than regulatory compliance levels within the contaminant area or in the case of monitored natural attenuation the plume should stabilize or shrink.

Baseline and recommended for each sampling round.

Degradation products, if appropriate (e.g., nitrobenzene produces aniline)

VOCs, EPA SW-846: 8260B

SVOCs, SW-846: 8270D.

Field GC or GC/MS can also be appropriate.

Regulatory compliance when degradation products are also hazardous. Line of evidence that degradation is taking place.

Hazardous degradation products are typically expected to decline to less than regulatory compliance levels within the contaminant area or in the case of monitored natural attenuation the plume should stabilize or shrink.

Baseline and recommended for each sampling round.

Soluble Iron (Suggested by San Mateo County 1996)

Preferred method is to field filter (0.45 µm filter) and ICP 200.7 (measures total of ferric and ferrous iron); alternate field method measuring ferrous iron: Colorimetric Hach Method 8146 (ITRC 2008)

Ferric iron is an alternate electron acceptor for microbial respiration in the absence of oxygen and nitrate. Reduction of ferric iron produces ferrous iron. Elevated levels of ferrous iron indicate that the groundwater environment is sufficiently reducing to sustain iron reduction and for anaerobic degradation to occur—hence conditions are probably not conducive for aerobic degradation.

Indicator of extent of anaerobic degradation. Useful at sites where MNA is chosen (San Mateo County 1996). Not necessary at sites where active aeration is taking place.

Recommended for each sampling round. Typically measured at the well head to protect samples from exposure to oxygen. (ITRC 2008)

Chloride

EPA Method E300.1 or SW-846: 9056A (laboratory methods)

Hach chloride test kit Model 8-P, or ISE for field measurements

General water quality parameter. Chloride is produced by aerobic dechlorination of several chlorinated hydrocarbons (CH) (e.g., chlorobenzene, methylene chloride, vinyl chloride). Elevated levels of chloride can indicate that dechlorination is occurring if observed concentrations are greater than 3 times background and consistent with CH molar concentrations.

Indicator parameter only.

Baseline and every subsequent sampling event.

Nitrate

EPA Method 300.1 or SW-846: 9056A  (laboratory- based ion chromatography methods) 

ISE may be used in field

Nutrient needed for microbial growth. Determines if phosphate needs to be injected into the subsurface and whether it is being consumed or accumulated. (EPA 2004)

May indicate need for phosphate amendment.

Baseline and quarterly thereafter (EPA 2004)

Dissolved Phosphate

EPA Method 300.

EPA SW-846: 9056A  (laboratory)

Nutrient needed for microbial growth. Determines if phosphate needs to be injected into the subsurface and whether it is being consumed or accumulated. (EPA 2004)

May indicate need for phosphate amendment.

Baseline and quarterly thereafter (EPA 2004)

Dissolved Oxygen (DO)

DO meter calibrated in the field according to the manufacturer's specifications (APHA et al. 1992: 4500-O G) (field). Should be done with downhole probe or flow-through cell to avoid atmospheric contact.

If MNA, to determine where aerobic degradation is possible. If active, to determine the success of the oxygen amendment application.

Active injection of an oxygen amendment (air, oxygen, ozone, hydrogen peroxide, Oxygen Release Compound®) into a source area and somewhat down gradient should re-establish aerobic degradation.

Baseline and quarterly for MNA (Pope 2004)

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Carbon Dioxide

APHA et al. 1992: 4500-CO2  C (titrimetric) or 4500-CO2 D (calculation requiring known values for total alkalinity and  pH)

ISE for field measurement

Carbon dioxide is a by-product of both aerobic and anaerobic degradation. Elevated levels of carbon dioxide indicate microbial activity has been stimulated.

Indicator parameter.

Optional for active system (ITRC 2008).

For MNA baseline and quarterly thereafter (San Mateo County 1996)

Oxidation Reduction Potential (ORP)

Direct-reading meter, A2580B, or USGS A6.5 (field)

ORP of groundwater provides data on whether or not aerobic conditions are present. Oxidizing conditions are required for aerobic degradation of contaminants. Used in conjunction with other geochemical parameters to determine whether or not groundwater conditions are optimal for aerobic biodegradation.

Positive ORP values (>0.0 mV) in conjunction with elevated levels of DO indicate aerobic conditions and the success of oxidant addition.

Optional for MNA remediation.

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004). Avoid aeration of sample during measurement.

Temperature

Field probe with direct-reading meter (APHA et al. 1992: 2550 B)

General water quality parameter used as a well purging stabilization indicator. Microbial activity is slower at lower temperatures.

Indicator parameter. Typically used as a well purge stabilization parameter.

Optional but generally done as part of well purge stabilization parameter suite.

pH

Field probe with direct-reading meter calibrated in the field according to the manufacturer�s specifications (APHA et al. 1992: 4500-H+ B)

Confirms pH conditions are stable and suitable for microbial bioremediation or identifies trends of concern. (EPA 2004)

The optimum pH for bacterial growth is approximately 7,

enhanced aerobic bioremediation can be effective over a pH range of 5 to 9 pH units (EPA 2004).

For MNA: baseline and quarterly thereafter (EPA 2004).

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Alkalinity

APHA et al. 1992: 2320 B, or Hach alkalinity test kit model AL AP MG-L, or Hach Method #8203 (field or laboratory)

ISE for field measurement

Indicator of biodegradation and aquifer buffering capacity (neutralization of weak acids). Used in conjunction with pH. An increase in alkalinity/stable pH indicate the aquifer's buffering capacity is sufficient to neutralize metabolic acids produced by degradation process (San Mateo County 1996).

Concentrations of alkalinity that remain at or below background in conjunction with pH <5 indicates that a buffering agent may be required (ITRC 2008).

Baseline and all sampling events thereafter (San Mateo County 1996).

Water Table Elevations

Water/air interface meter

Determines direction of groundwater flow and allows for estimate of flow rate.

For MNA groundwater flow direction and rate should fall within the expected range.

Determines if hydraulic conditions (groundwater flow) are consistent with design intent or if enhanced aerobic bioremediation technology application has had an unanticipated effect on these conditions (EPA 2004).

For MNA baseline and all sampling events thereafter (San Mateo County 1996).

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

SOIL VAPOR

Carbon Dioxide

Draeger Tube

Bacharach Fyrite® Gas Analyzer

Carbon dioxide is a by-product of both anaerobic and aerobic degradation. Elevated levels of carbon dioxide indicate microbial activity has been stimulated.

Indicator parameter.

For MNA at least bi-annually (Pope 2004)

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Methane

EPA Method 18 (GC)

EPA SW-846: 5021A

Robert S. Kerr Laboratory RSK-175 SOP followed by GC or GC/MS

Provides evidence that biodegradation is occurring

Methane is usually the product of anaerobic biodegradation. High levels will give an indication that biodegradation is proceeding. High levels of methane will also indicate that efforts to aerate the target area may not be succeeding.

For MNA at least biannually (EPA 2004).

Oxygen

Bacharach Fyrite� Gas Analyzer

Oxygen level in soil gas is an indication that aerobic biodegradation is occurring in MNA systems.

Oxygen level indicates the success of oxidant input in active systems.

Reduced oxygen levels are expected during aerobic biodegradation in MNA systems.

Steady state or enriched oxygen levels are one indication that soil conditions are appropriate for aerobic biodegradation

For MNA at least bi-annually (EPA 2004).

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

Volatile COCs

EPA SW-846: 8260B Laboratory

Field GC or GC/MS

Contaminant levels give indication of success of remedial effort.

Suggests residual sources in soil or fugitive emissions associated with the remedial effort

For active systems daily for the startup phase (7-10 days) and weekly to monthly thereafter (EPA 2004).

SOIL

COCs

VOCs, EPA SW-846: 8260B    SVOCs, SW-846: 8270D

Determine success of remediation.

Soil contaminant concentrations should be dropping over time.

For MNA a statistically significant number of continuous soil cores located throughout the area of contamination (Pope 2004).

For active systems quarterly to annually (EPA 2004).

Sources: EPA 2004a and San Mateo County 1996.

References

Adobe PDF LogoEngineered Approaches to In Situ Bioremediation of Chlorinated Solvents: Fundamentals and Field Applications
U.S. EPA, Technology Innovation Office.
EPA 542-R-00-008, 144 pp, 2000

Provides an overview of in situ bioremediation to remediate chlorinated solvents in contaminated soil and groundwater and describes degradation mechanisms for chlorinated solvents, enhancements of these mechanisms by the addition of various materials and chemicals, design approaches, and factors to consider when selecting and using the technology. Contains 9 case studies of field applications.

Environmental Molecular Diagnostics: New Site Characterization and Remediation Enhancement Tools
Interstate Technology & Regulatory Council (ITRC), Environmental Molecular Diagnostics Team. EMD-2, 363 pp, Apr 2013

EMD technologies can be classified into two major categories of analytical techniques: chemical technologies (i.e., CSIA), and different molecular biological techniques. A detailed description of each major EMD is illustrated with case studies of their application and recommendations regarding appropriate uses. Frequently asked questions regarding the underlying science, including stable isotope chemistry and fundamental molecular biology, are addressed in the appendices. Also available as a PDF file Adobe PDF Logo

A Guide for Assessing Biodegradation and Source Identification of Organic Ground Water Contaminants Using Compound Specific Isotope Analysis (CSIA)
Hunkeler, D., R.U. Meckenstock, B. Sherwood-Lollar, T.C. Schmidt, and J.T. Wilson.
EPA 600-R-08-148, 82 pp, 2008

When organic contaminants are degraded in the environment, the ratio of stable isotopes often will change, and the extent of degradation can be recognized and predicted from the change in the ratio of stable isotopes. Recent advances in analytical chemistry make it possible to perform compound-specific isotope analysis (CSIA) on dissolved organic contaminants, such as chlorinated solvents, aromatic petroleum hydrocarbons, and fuel oxygenates, at concentrations in water that are near their regulatory standards. Because CSIA is a new approach, no widely accepted standards have been established for accuracy, precision, and sensitivity, nor approaches to document accuracy, precision, sensitivity and representativeness. This text provides general recommendations on good practice for sampling, measurement, data evaluation and interpretation in CSIA. This guide is intended for managers of hazardous waste sites who must design sampling plans that will include CSIA and specify data quality objectives for CSIA analyses, for analytical chemists who must carry out the analyses, and for staff of regulatory agencies who must review the sampling plans, data quality objectives, and the data provided from the analyses.

How to Evaluate Alternative Cleanup Technologies for Underground Storage Tank Sites: A Guide for Corrective Action Plan Reviewers
U.S. EPA. EPA 510-R-04-002, 2004a

This manual was written specifically for addressing petroleum hydrocarbon problems. In terms of bioremediation, most petroleum hydrocarbons degrade preferably under aerobic conditions. While DNAPL source zones and contaminant plumes are somewhat more difficult to characterize, those that degrade preferably under aerobic conditions will present many of the same problems and will have similar bioremediation approaches. These approaches also will have similar performance monitoring requirements.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies
Interstate Technology & Regulatory Council (ITRC) Bioremediation of DNAPLs Team.
BioDNAPL-2, 173 pp, 2007

Based upon the results of 6 case histories of in situ bioremediation (ISB) of DNAPLs, this report provides state and federal regulators having oversight of the cleanup of DNAPL sites with evidence supporting ISB as a viable cleanup strategy.

National Field Manual for the Collection of Water-Quality Data
U.S. Geological Survey (USGS) Techniques of Water-Resources Investigations (Book 9, Chapters A1-A9).

Natural Attenuation of Petroleum Hydrocarbons
San Mateo County, California. Appendix F in "Natural Attenuation of Petroleum Hydrocarbons: An Implementation Guidance," 1996

Adobe PDF LogoPerformance 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.

Standard Methods for the Examination of Water and Wastewater, 18th Edition
American Public Health Association (APHA), American Water Works Association, and Water Environment Federation, 1992 Standard Methods commercial Web site

SW-846 On-Line: Test Methods for Evaluating Solid Waste, Physical/Chemical Methods
U.S. EPA, Office of Resource Conservation and Recovery.

Abstracts

Geophysical Imaging for Investigating the Delivery and Distribution of Amendments in the Heterogeneous Subsurface of the F.E. Warren AFB

Geophysical Monitoring of Vegetable Oil Emulsion Biostimulation Using Cross-Hole Radar Methods



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