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How much Oxygen in Needed for Aerobic Cometabolism of PCE?

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Aerobic Cometabolism of PCE

CL-Out bioremediation degrades PCE without the production of vinyl chloride under a wide aerobic range.  The degradation pathway is via organic acids. The following compilation of data from 14 locations shows PCE removal with ORP levels in ground water ranging from -150 to 250 standard units.  The concentration removed PCE concentrations ranging from 10 to nearly 1,000 ug/L.  The amount removed does not appear to be dependent on the ORP level.  The amount of PCE removed is probably a function of the initial concentration, with higher mass removal correlating with higher initial concentrations.

The relationship between the starting mass and amount of PCE removed appears to be unrelated to the ORP levels.  The following chart shows nearly 100% of the PCE concentration is removed at all ORP levels, even at less than -50.  The  PCE removal rate appears to decrease at ORP levels above +200, but sites with that level of ORP are rare.

The following chart shows the vinyl chloride concentrations at the same 14 sites.  As the PCE is degraded the vinyl chloride concentrations increased slightly at some locations.  The increase in vinyl chloride was 10 ug/L or less at most locations.  A high increase in vinyl chloride was observed at a location where the ORP was less than -50.  This result suggests that there may be a threshold relationship between a low ORP less than -50 and a significant increase in vinyl chloride.

As a percentage of the amount of PCE removed, the increase in vinyl chloride is much less than 10% except when the starting ORP was less than -50.

This compilation of data from different sites shows that with a starting ORP above -50, CL-Out bioremediation will be effective in PCE removal without the production of vinyl chloride.  These results should be significant in selecting a remediation option to prevent vinyl chloride vapor intrusion risk by source removal.

Contact us for more information and potential applicability to your situation.

CL-Out Bioremediation of Ground Water in Clay Soils

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Successful In Situ Remediation in Low Permeability

CL-Out bioremediation of groundwater in clay soils reduced concentrations of PCE and TCE at a former dry cleaners in Moline, Illinois.  In just over 2 weeks after injection, CL-Out microbes cut the contaminant concentrations in half.

  • PCE from 62.2 to 25.6 mg/L
  • TCE from 11.2 to 6.0 mg/L
  • Cis 1,2-DCE from 3.8 to 1.2 mg/L
  • Vinyl chloride less than 0.001 mg/L before and after treatment

The remediation continues as the microbes grow and cometabolize the residual contamination.  Even in tight clay soils the aerobic cometabolism remediates dry cleaning solvents without producing vinyl chloride or other dangerous by products.

Contact us for a free assessment of your site for bioremediation.

How Aerobic PCE Bioremediation Works

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How CL-Out Aerobic PCE Bioremediation Works

A CL-Out bioremediation pilot study confirmed that aerobic PCE cometabolism removed dry cleaning solvent contamination from ground water.  The pilot study was located at a former dry cleaners, where the PCE in ground water was 27 parts per billion (ppb).  Bioaugmentation introduced CL-Out microbes and dextrose as the metabolic substrate by injected into the ground water up gradient from the sentinal monitoring well.  After 30 days the PCE concentration decreased to 20 ppb.  After 6 months the PCE concentration decreased to 16 ppb.

As the PCE was decreasing, the site conditions stayed aerobic.  The dissolved oxygen level in ground water decreased from 1.07 to 0.71 mg/l.  Meanwhile,  the ORP decreased from 99 to 45 mv.  These aerobic aquifer conditions support the conclusion that the PCE removal was through aerobic bioremediation.

CL-Out cometabolism uses a dioxygenase enzyme that is produced constituatively as the metabolic substrate is consumed.  The dioxygenase enzyme destabilizes the carbon bond in the PCE to convert the molecule to an organic acid that leads to complete mineralization. Click here to view the PCE and TCE cometabolic degradation pathways.

CL-Out is a consortium of naturally-occurring microbes.  The microbes have the benefits of metabolic diversity and environmental stability.  They are non-pathogenic and safe for human health and the environment. Click here to find out more about CL-Out bioremediation.

 

 

Bioremediation of a Dry Cleaners

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Cost-effective Bioremediation of a Dry Cleaners Quickly Removed Contamination

Historical operations at a Houston area dry cleaners resulted in a chlorinated solvent plume (perchloroethylene or PCE) in the shallow ground water. Permeable shallow soil at the site allowed rapid vertical migration at the source and lateral migration in the shallow ground water. This migration resulted in an off-site migration of the plume beneath an apartment complex causing concern for potential vapor intrusion hazards; as well as, a decrease in property value.

A ground-water extraction and treatment system was installed to address the
dissolved phase concentrations. The system reduced the total volatile organic compound
(VOC) concentration in the source area from 115,400 to 36,500 µg/l. However, over
time, operating maintenance and cost escalations were exceeding the on-going remedial
benefit. The system was shut down after nine years of operation.

A review of available remedial technologies that could be implemented within the physical constraints of the
site was conducted. In-situ enhanced aerobic bioremediation was selected to address the
remaining ground-water concentrations because of the permeability of the formation, the
relatively aerobic conditions, and the benefit of reducing the risk of VC accumulation.

 

What enzymes Are Involved in Aerobic Bioremediation of PCE and TCE?

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CL-Out aerobic bioremediation PCE and TCE is a sustainable process for soil and ground water remediation.  As these compounds are not directly metabolized under aerobic conditions, the competitive advantage goes to the CL-Out organisms that cometabolize them.  While utilizing a sugar substrate, the CL-Out organisms produce  mono- and dioxygenase  enzymes that bridge the carbon bond to destabilize the compound.   The solvent is converted to an organic acid that the organism can metabolize.  View the degradation pathway.  The benefit is that CL-Out bioremediation can be applied to soils both in situ and ex situ.  Click here for to download a case study.  For further explanation call CL Solutions at 513-284-5940.