TCE Remediation With CL-Out® Bioremediation and Dual-Phase Extraction

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Case Study: Industrial Site, Houston, Texas

Site Summary
CL-Out® bioaugmentation was implemented in combination with dual phase extraction at an industrial site near Houston, Texas to remove trichloroethylene (TCE) from ground water. The overlying contaminated soil was excavated, but perched ground water and a deeper aquifer had TCE concentrations greater than 10,000 µg/L. A dual-phase vacuum extraction system was installed to control the ground water gradient and increase distribution of the CL-Out® organisms in the aquifer. The TCE concentrations were reduced by 99.9% in one year.

Geology and Hydrogeology
The site is located on coastal plain sediments characteristically interbedded sands, silts and clays. The first impacted ground water was a thin perched layer 16 to 18 feet below ground surface. A more transmissive, water bearing zone was at 25 to 30 feet deep. Both water-bearing layers and the interbedded fine-grained layers had TCE concentrations above regulatory standards.

Contamination
High concentrations of TCE were present in perched and deeper ground water. Prior to treatment, a small area of soil less than 500 square feet had TCE concentrations greater than 20,000 µg/L. The underlying impacted perched ground water area was the same size and had TCE concentrations up to 30,000 µg/L. The TCE migrated laterally in the underlying deeper ground water where the TCE concentrations were greater than 10,000 µg/L. The area of the deeper ground water plume was approximately 30,000 square feet.

Remediation
The contaminated unsaturated soil was excavated for treatment to the perched ground water. The perched ground water was treated by a combination of potassium permanganate and vapor extraction. The deeper aquifer was treated by a combination of dual-phase extraction and CL-Out® bioremediation.

CL-Out® was applied eight times between January, 2010 and February, 2011. During each application 55 to 110 gallons of CL-Out® was injected into the ground water. The dual-phase extraction system was used to control the ground water gradient and induce greater distribution of the CL-Out® microbes. Periodic plate count analysis of the microbial population in the treated aquifer was completed to guide where and when the CL-Out® population should be supplemented. The repeat applications were on approximately 4 to 6 week intervals.

Results
Following one year of bioaugmentation, the contaminant concentrations were reduced by more than 99%. The daughter products caused by incomplete natural breakdown were removed as well as the TCE. The following table shows the contaminant concentration trends in the treatment area.

Chromium-Contaminated Ground Water Bioremediation

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A bench-scale study demonstrated the viability of bioremediation of chromium contaminated ground water. The key factor to successful bioremediation was the selection of chromium-tolerant microbes. Actual contaminated ground water samples for the test. The ground water contained total chromium of 280 mg/L, with 270 mg/L hexavalent chromium.

The original sample was split into four bottles, with one preserved as a standard. Three split samples were treated with different blends of microbes. All three of the treated samples showed a reduction in the total dissolved chromium and nearly complete conversion from hexavalent to trivalent chromium. The average total chromium concentration in the treated samples was 160 mg/L and the hexavalent chromium concentration was 0.017 mg/L in two of the three treated samples. The sediments were not isolated for testing due to the small volume of sediment in the sample bottles.

Vials Showing Chromium Bioremediation Results

The photograph shows the untreated chromium-contaminated water on the left. The three bottles to the right were treated with various microbial blends.

Petrox Bioremediation Prepares Urban Bulk Fuel Facility For Reuse

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Soil Recycling Prepares Site for Redevelopment

A 30 acre bulk fuel facility is ready for reuse after on-site bioremediation of nearly 100,000 tons of petroleum-contaminated soil in an urban setting near Los Angeles. Bulldog Green Remediation of Walnut Creek, California used a proprietary ex situ treatment process combining Petrox organisms in a custom blend to remediate the soils. All soil was treated and reused on site. This closed-loop process eliminated 8,000 truck loads of soil from the roads and landfills in southern California.

The treatment process reduced contaminant concentrations from typical levels of 1,000 to 10,000 mg/kg to less than 100 mg/kg in less than 30 days. This rapid treatment rate made possible continuous cycling from excavation, through treatment, and back filling.

The site is now ready for reuse as a park and other development.

Pesticide Bioremediation

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CL Solutions recently completed a field pilot study of bioremediation of mixed chlorinated pesticides. Under the pilot study Petrox treated several cubic yards of soil highly contaminated by a suite of related chlorinated organic pesticides.  The pilot study showed the overall impact was a reduction of the pesticide concentrations by 28% to 93% in 60 days.  The contaminant removal rate was 88 to 100 kg/kg/day.

The full scale implementation is expected to begin in the summer of 2017.

Sulfolane Bioremediation

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Sulfolane is an emerging contaminant of concern for potential environmental impact to ground water in Alberta.  CL Solutions recently completed laboratory bench-scale testing that showed the Petrox organisms can efficiently degrade sulfolane.  Under laboratory conditions Petrox organisms metabolized sulfolane at a minimum rate of 33 ug/L/day.  Further lab tests are under way and field scale implementation may proceed in the Summer of 2017.