New Chlorinated Solvent Results

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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

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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.

Can Aerobic Bioremediation Remove PCE?

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CL-Out microbes using aerobic bioremediation can remove PCE contamination from ground water.  One of the easiest ways to remove a large mass of residual PCE from ground water is to treat the ground water following source soil excavation. Because CL-Out microbes cometabolize PCE under aerobic conditions,  the microbes can be applied to the ground water in the base of the excavation to treat residual contamination in the soil and ground water.  The open pitprovides oxygenand aerobic conditions to support the aerobic bioremediaion of PCE.  The excavation also serves as an easy access route into a large area of ground water in lieu of multiple injection points.

This method has been used at many dry cleaner locations with a variety of soil types and geologic settings.  Recently this method has been used at a former dry cleaners near Dayton, Ohio.  At this site the PCE concentrations were reduced from 570 ug/L to 43 ug/L with one application into the source soil excavation cavity.

 

 

Soil Mixing to Improve Distribution of Microbial Solution

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Bioaugmentation results can be accelerated and amplified by soil mixing to improve distribution and contact.  The equipment shown in this example was used to blend Petrox with contaminated soil to a depth of 10 feet.

Soil Mixing Equipment to Improve Microbial Solution Distribution

Soil Mixing Equipment to Improve Microbial Solution Distribution

Click here to view a short video of soil mixing.

Can Bioremediation by Cometabolism Take Care of 1,1,1-TCA in a Mixed Solvent Plume?

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CL-Out makes bioremediation by cometabolism of 1,1,1-TCA and other chemicals in a mixed solvent plume possible.  One of the benefits of CL-Out cometabolism is that the enzymes produced by the Pseudomonas sp. organisms convert a wide range of organic chemicals into organic acids that can be metabolized.  The aggressive application of CL-Out organisms to soil and ground water at a chemical mixing company removed the source of ground water contamination by chloroethanes and chloroethenes,  including PCE and 1,1,1-TCA.  The aerobic cometabolism of these compounds achieved MCLs in less than 6 months.

Site Summary

CL-Out® bioaugmentation was implemented to remediate a mixture of chlorinated solvents in soil and ground water at a former chemical packaging company.  The contamination resulted from incidental spills over many years of operations.  After the extent of contamination was determined, a pump and dispose containment system was installed in 1993 to mitigate further off-property contaminant migration.  CL-Out bioaugmentation was initiated in 2001 to remove the source of contamination.  After six months of monthly treatment the contamination levels met the applicable drinking water standards.

 

Geology and Hydrogeology

The site is set in a complex fluvial and glacial region where tills and fluvial channel deposits are interbedded.  The surface material is mainly industrial fill over silty clay till.  Perched ground water is present in a sandy gravel deposit in a former fluvial channel at the base of the fill and top of the till.

 

The perched ground water zone is the main conduit for contaminant migration. The perched ground water zone is approximately 4 feet thick.  The hydraulic conductivity of the deposits was measured as 10-4 cm/sec.  The flow direction was irregular and controlled by the former channel boundaries.

 

Contamination

 

The volume of soil contamination in the vadose zone source area was estimated to be 2,200 tons.  The main contaminants were 1,1,1-TCA, PCE and TCE.  The maximum soil concentrations were: PCE 1.1 mg/kg, TCE 2.2 mg/kg, 1,1,1-TCA 1.2 mg/kg, and 1,1-DCE 0.003 mg/kg.

 

The ground water plume containing the solvents was estimated to be 12,000 square feet.  The main contaminants and maximum concentrations were: 1,1,1-TCA 2.7 mg/L, PCE 0.11 mg/L, and TCE 0.58 mg/L, with some daughter products including 1,2-DCE 2.9 mg/L, vinyl chloride 0.17 mg/L and 1,1-DCA 0.12 mg/L.

 

 

Remediation

CL-Out® was applied by injecting a concentrated microbial solution into the soil and ground water in the source. Six pairs of  on-inch diameter injection points were installed with one injection point competed in the shallow soil and one penetrating to the perched ground water. The CL-Out® was allowed to flush through the soil and aquifer and follow the migration path of the contaminants.

 

The six injections were completed between February and November 2001.  The volume injected ranged between 275 and 385 gallons of CL-Out solution per event.

 

Results

Following CL-Out® bioaugmentation, ground water monitoring in an untreated monitoring well was used to track the remediation results.  The concentration of all contaminants decreased quickly and steadily after the first application. In six months, all contaminants except vinyl chloride were remediated to the drinking water standard.  There was an unexplained rebound in vinyl chloride concentrations, but the concentration was reduced to acceptable levels that were maintained during quarterly post treatment monitoring.  The following table summarizes the ground water sampling results.

 

Contaminant Pre-treatment Sampling Progress Sampling Post-Treatment Sampling
2/20/01 2/9/01 3/22/01 6/1/01 8/21/01 10/16/01 12/11/01 2/28/01
1,1,1-TCA 2.7 1.3 1.4 0.62 0.086 0.015 0.015 0.007
PCE 0.11 0.19 0.92 0.010 BDL BDL BDL BDL
TCE 0.58 0.26 0.068 0.012 BDL BDL BDL BDL
c-1,2-DCE 2.9 5.9 4.7 2.8 0.19 0.010 0.091 BDL
1,1-DCA 0.12 0.38 0.28 0.19 0.15 0.066 0.059 0.038
VC 0.17 0.34 0.11 0.57 0.10 0.008 0.1 BDL

The treatment was successful in reducing the concentrations of a range of chlorinated solvents in the source area and down gradient plume.  Overall, the application of bioremediation achieved the remediation goals quickly and cost effectively making the property redevelopment possible.