Benzo(a)pyrene Bioremediation Using Custom Blend Microbes

Benzo(a)pyrene is a difficult remediation challenge. It is resistant to biological and chemical destruction and extraction from soil.  CL Solutions Custom Blend microbes, however, have successfully remediated benzo(a)pyrene and other PAHs in soil during ex situ land farming treatment.  By placing the contaminated  material in windrows, controlling the temperature and moisture, the addition of Custom Blend microbes has reduced the benzo(a)pyrene concentration by as much as 330 ug/kg/day.

The same approach works on high as well as low concentrations.  At a site in Oregon, the benzo(a)pyrene concentration was reduced from 140 ug/Kg to below detection limits in 7 days.  At a site in Ohio, the benzo(a)pyrene concentration was reduced from 28,000 ug/kg to 3.8 ug/Kg in 60 days.  At both sites, Custom Blend microbes effectively treated the full suite of PAHs along with the benzo(a)pyrene.

New Chlorinated Solvent Results

CL-Out bioremediation continued to show outstanding results in bioremediation of PCE, TCE and other chlorinated solvents at three recent applications. Results show more than 90% PCE removal with a single application of CL-Out for in situ ground water treatment. The PCE remediation did not cause an increase in vinyl chloride showing that the breakdown pathway was by dioxygenase cometabolism and not by reductive dechlorination.

A site in Massachusetts showed the following ground water results:
PCE 1,100 ug/L reduced to 30 ug/L, 97% removed
TCE 39 ug/L reduced to 5.6 ug/L, 85% removed
No other daughter products were detected.

Ground water remediation in Florida showed these results:
PCE 182 ug/L reduced to 16.1 ug/L, 91% removed
TCE 9.82 ug/L reduced to 2.77 ug/L, 71% removed
cis 1,2 DCE 3.26 ug/L reduced to 0.282 ug/L, 91% removed
vinyl chloride was not detected before or after bioremediation.

Ground Water contamination at a site in New Jersey followed the same trend:
PCE 690 ug/L reduced to less than 5 ug/L, 99% removed
TCE 7,980 ug/L reduced to less than 810 ug/L, 89% removed
No breakdown products were detected.

These sites join the hundreds of sites remediated by CL-Out aerobic cometabolism.

Perchlorate Remediation Receives Greener Cleanup Leadership Award

The Massachusetts Department of Environmental Protection awarded Irwin Engineering of Natick, Massachusetts the 2016 Greener Cleanup Leadership Award for the innovative in situ bioremediation of perchorate contamination of soil and ground water at the Concord Road Site in Billerica, Massachusetts. The award honors LSPs and their clients for promoting greener cleanup principles and practices to reduce the overall net environmental footprint of hazardous waste site cleanup response actions under the Massachusetts Contingency Plan.

In addition to implementing best practices, Irwin Engineers was able to close the site at least 5 years sooner and saving their client over $5 million. The site cleanup achieved residential soil standards without site use limitations and achieved ground water levels protective of drinking water.

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

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

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.