Data-Informed Enhanced Bioremediation

Enhanced in situ bioremediation (EISB) is a treatment technology that creates physical, chemical, and biological changes at a site to accelerate the biological degradation of contaminants of concern. A common EISB approach is to inject a remedial product, such as an electron donor, electron acceptor, nutrient blend, or colloidal activated carbon, to stimulate the desired microbial activity. If native contaminant-degrading microorganisms are absent or limited at a site, a bioaugmentation culture may also be introduced. A well-managed EISB project can benefit from collecting chemical, geochemical, and microbial lines of evidence at every stage of a bioremediation project.

SITE ASSESSMENT: Baseline data can help delineate the contaminant source zone and plume, identify potential limitations in electron acceptors or donors, and determine the presence and abundance of indigenous contaminant-degrading microorganisms.

REMEDY SELECTION: Whether a pilot test or in situ microcosm study is used to assess the feasibility of a biostimulation or bioaugmentation treatment option, a sampling program that includes microbial data can verify that the remedy performed as expected or identify any issues prior to investing in a full-scale application.

PERFORMANCE MONITORING: After a treatment has been applied, analyzing spatial and/or temporal trends in chemical, geochemical, and microbial data can confirm whether the remedy was effective and help explain unexpected datapoints.

Molecular Biological Tools for ENHANCED BIOREMEDIATION

QuantArray®-Chlor
CENSUS® (qPCR) DHC
In Situ Microcosm Study

MBTs for Electron Donor Addition

Biostimulation with the addition of an electron donor such as an emulsified vegetable oil enhances the growth of halorespiring bacteria (e.g., Dehalococcoides, Dehalogenimonas, Dehalobacter). This practice is an established treatment strategy for remediating sites impacted by chlorinated solvents, including chlorinated ethenes (PCE, TCE, DCE, VC) and chlorinated ethanes (TCA, DCA, etc.).

Quantification of the contaminant-degrading microorganisms (e.g., Dehalococcoides) and their responsible genes (e.g., vinyl chloride reductase) is accomplished using CENSUS® qPCR or QuantArray®‐Chlor.  An In Situ Microcosm Study can also be used to cost-effectively screen different amendments and bioaugmentation cultures under actual site conditions.

QuantArray®-Petro
CENSUS® (qPCR) ER
Stable Isotope Probing
In Situ Microcosm Study

MBTs for Electron Acceptor Addition

The biodegradation of petroleum hydrocarbons, including BTEX, PAHs, and alkanes, can be limited by low concentrations of electron acceptors, such as dissolved oxygen, nitrate, and sulfate. Therefore, an electron acceptor is often added through biosparging, oxygen infusion, or remediation product injection to promote the growth of contaminant-degrading bacteria and enhance bioremediation.

Pre- and post-treatment, molecular biological tools (MBTs) like CENSUS® qPCR or QuantArray®‐Petro can be used to detect and quantify existing bacteria and their functional genes capable of degrading petroleum hydrocarbons, Complementing these analyses, Stable Isotope Probing is an innovative MBT that can be used to conclusively demonstrate the biodegradation of a specific contaminant (e.g., benzene or naphthalene) under current site conditions. When selecting an electron acceptor, an In Situ Microcosm Study can be used to collect the microbial, chemical, and geochemical evidence needed to cost-effectively evaluate both aerobic and anaerobic biostimulation products.

Frequently asked questions

How many samples should I collect to characterize a site?

For most sites, we recommend at a minimum collecting samples across a gradient (e.g., upgradient, source, mid-plume, downgradient, etc.) Sample locations can also be selected based upon changes in contaminant concentrations. For example, select sampling locations in which the primary contaminant concentration varies by an order of magnitude. Unfortunately, collecting just one qPCR sample will not provide a lot of information about the microbial community at a given site.

What does the concentration of Dehalococcoides mean?

The abundance of Dehalococcoides within a given sample is often used as an indicator of the potential for reductive dechlorination to occur. Lu et al. (2006) have proposed using a Dehalococcoides concentration of 1.0E+04 cells/mL as a screening criterion to identify sites where biological reductive dechlorination will proceed at “generally useful” rates.

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Resources for Enhanced In situ bioremediation

Tech Bulletin – Preparing for Electron Acceptor Addition
Tech Bulletin - Preparing for Electron Donor Addition
Tech Bulletin - Preparing for Colloidal Carbon Injection
Top Tips – Evaluating Remediation Options – Chlorinated
Top Tips – Evaluating Remediation Options – Petroleum
In Situ Microcosms White Paper

EISB Case Studies

Characterizing Microbial Communities and Assessing Biodegradation Potential

NGS and QuantArray®-Chlor: Characterizing Microbial Communities and Assessing Biodegradation Potential

• A pilot study was conducted at a site where electron donor was injected into groundwater impacted by a mixture of chlorinated solvents.

• QuantArray®-Chlor and NGS provided complimentary evidence of both biotic and abiotic reductive dechlorination in response to the injection of the electron donor giving the client confidence in this remediation strategy expanding electron donor injection to the entire site.

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In Situ Microcosms: MNA vs Enhanced Aerobic Bioremediation

• The ISM study conducted at this site provided clear, actionable evidence that increasing the dissolved oxygen concentration at the site would stimulate hydrocarbon biodegradation. Further, this evidence was provided in a significantly more cost effective manner than a bench-scale treatability study or a pilot scale study and in a more timely manner.

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Screening MNA vs Sulfate Injection at a BTEX Impacted Site

In Situ Microcosms: Screening MNA vs Sulfate Injection at a BTEX Impacted Site

• The ISM study conducted at this site provided clear, actionable evidence that increasing the sulfate concentration at the site would stimulate hydrocarbon biodegradation. Further, this evidence was provided in a significantly more cost effective manner than a bench-scale treatability study or a pilot scale study and in a more timely manner.

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QuantArray®-Chlor: Actionable Data for Remedy Selection

• Site managers were considering monitored natural attenuation (MNA), biostimulation, and bioaugmentation as remediation strategies at a site impacted by a complex mixture of chlorinated hydrocarbons including PCE, TCE, 1,1,2-TCA, 1,2-DCA, cis-DCE, and VC along with high concentrations of sulfate.

• QuantArray®-Chlor analysis provided actionable data for remedy selection allowing timely decisions and significant cost savings in site management.

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ISM & SIP: Combining In Situ Microcosms and Stable Isotope Probing

• A site impacted by chlorobenzene was managed by MNA.

• The ISM study provided answers to site managers’ questions at a significant cost savings compared to pilot-scale studies and provided sound support for a pathway to reducing time to closure at the site.

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QuantArray®-Petro: Effectiveness of Oxygen Addition at a Former Gas Station

• Groundwater at a former gasoline service station was impacted by leaking underground storage tanks and associated piping. Although contaminant trends and geochemistry suggested that MNA could be an appropriate site management strategy, the need for more rapid site closure led to a decision to enhance biodegradation of BTEX and MTBE aerobically with injection of an oxygen releasing compound.

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QuantArray®-Chlor: Actionable Data for Performance Monitoring

• QuantArray®-Chlor analysis allowed site managers to have a comprehensive understanding of all relevant microbial processes at the site over time which allowed timely decisions and significant cost savings in site management.

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ISMs: Cost Effective Remedy Selection at a TCE Impacted Site

• The ISM study conducted at this site provided clear, actionable evidence that electron donor injection would stimulate reductive dechlorination without the need for expensive bioaugmentation. Further, this evidence was provided in a significantly more cost effective manner than a bench-scale treatability study or a pilot scale study and in a more timely manner.

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EASY STEPS TO SUPPORT ENHANCED BIOREMEDIATION

1) Call us at 865.573.8188 or email at [email protected]
2) A friendly member of our team will advise you on the right tools for the job
3) Order and receive your supplies
4) Perform sampling according to our clear and easy protocols
5) Fill out the chain of custody form
6) Send to the nearest Microbial Insights location
7) Receive your unbiased report with actionable data and insight

Corrective Action Plans

Have a different corrective action plan you are considering?  Click the button information for other plan types and how Microbial Insights can help your project.

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