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QuantArray

Microbial Insights

QuantArray is a hybrid technology combining the highly parallel detection of DNA microarrays with the accurate and precise quantification of qPCR into a single platform. For more comprehensive evaluation of biodegradation, use QuantArray to simultaneously and cost-effectively quantify an entire suite of key contaminant degrading microorganisms and functional genes.

QuantArray-Chlor provides not only quantification of a variety of halorespiring bacteria (Dehalococcoides, Dehalobacter, Dehalogenimonas, etc.) to assess the potential for reductive dechlorination but also includes functional genes involved in aerobic biodegradation pathways and even competing microbial processes.

QuantArray-Petro provides the simultaneous quantification of the functional genes responsible for aerobic and anaerobic biodegradation of BTEX, PAHs and a variety of short and long chain alkanes.

 

Case study: using QuantArray® to confirm the efficacy of remediation strategies to save money and time

The purpose of an amendment such as an electron donor is to stimulate growth of specific microorganisms capable of biodegrading the contaminants of concern.  Therefore, quantifying the concentrations of those contaminant degrading microorganisms is a direct and valuable line of evidence when evaluating the feasibility and performance of bioremediation.

QuantArray® is a DNA based analysis that provides simultaneous quantification of a broad spectrum of target microorganisms (e.g. Dehalococcoides) and functional genes (e.g. vinyl chloride reductase) for comprehensive and cost-effective assessment of biodegradation.

Baseline Sampling/Remedy Selection

At a chlorinated solvent site, QuantArray®-Chlor aided in remedy selection by quantifying key microorganisms and functional genes involved in reductive dechlorination, aerobic cometabolism, and competing electron accepting processes. 

① Dehalococcoides (DHC) and vinyl chloride reductase genes were detected indicating the presence of microorganisms capable of complete reductive dechlorination of PCE and TCE to ethene.  However, Dehalococcoides concentrations were substantially lower than the 104 cells/mL recommended by Lu et al (2006) for generally effective reductive dechlorination.

② Dehalobacter (DHBt), capable of partial reductive dechlorination of PCE and TCE to cis-DCE, were detected but also at low concentrations.

③ Sulfate reducing bacteria, known to compete with Dehalococcoides and other halorespiring bacteria for hydrogen, were detected at noteworthy concentrations.

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Performance Monitoring

Based on low concentrations of Dehalococcoides, electron donor injection was performed to promote growth of halorespiring bacteria and enhance reductive dechlorination.  Groundwater samples collected 3 months after electron donor injection were submitted for QuantArray-Chlor analysis to evaluate the effectiveness of the remedy.

① Concentrationsof Dehalobacter (DHBt), Dehalogenimonas (DHG) and Desulfitobacterium spp. (DSB) increased by several orders of magnitude demonstrating growth of halorespiring bacteria in response to electron donor injection.

② Dehalococcoides (DHC) concentrations also increased substantially following electron donor injection but were still slightly lower than 104 cells/mL.  Likewise, vinyl chloride reductase genes were detected but at low concentrations.

③ Concentrations of methanogens increased by four orders of magnitude after injection.  Combined with high concentrations of sulfate reducing bacteria, competing electron accepting processes may have hindered growth of Dehalococcoides to a limited degree during the first three months.  Continued microbial monitoring was recommended to confirm that Dehalococcoides concentrations continued to increase after depletion of available sulfate.

Overall, the QuantArray®-Chlor results conclusively demonstrated that electron donor injection promoted growth of known halorespiring bacteria including Dehalococcoides and provided a strong line of evidence indicating that biostimulation would be an effective treatment strategy.

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