Research on Aerobic Cometabolism of PCE

Aerobic cometabolism of PCE and other halogenated solvents by Pseudomonas sp.  has been well established for more than 20 years.  The following research articles were key in the development of this approach to bioremediation.  This academic research provided parallel support to CL Solutions’ successful application of aerobic cometabolism to bioremediation of hundreds of contaminated sites since 1999.

Vandenbergh, P. A., and Kunka, B. S., Metabolism of Volatile Chlorinated Aliphatic Hydrocarbons by Pseudomonas fluorescens, Applied and Environmental Microbiology, v. 54, no. 10, Oct. 1988. p. 2578 – 2579.

Deckard, L. A., Willis, J. C., and Rivers, D. B. , Evidence for the Aerobic Degradation of Tetrachloroethylene by a Bacterial Isolate, Biotechnology Letters, v16, no. 11, November, 1994. p 1221-1224.

Ryoo, D., Shim, H., Canada, K., Barbieri, P., and Wood, T.K., Aerobic Degradation of Tetrachloroethylene by Toluene-O-xylene Monooxygenase of Pseudomonas stutzeri OX1, Nature Biotechnology, vol 18, July, 2000. p 775 – 778.

Shim, H., Ryoo, D., Barbieri, P, and Wood, T.K., Aerobic Degradation of Mixtures of Tetrachloroethylene, Trichloroethylene, Dichloroethylenes, and Vinyl Chloride by Toluene-O-Xylene Monooxygenase of Pseudomonas stutzeri OX1, Applied Microbiol Biotechnol, v. 56, May 2001. p 265-269.

 

 

Florida Dry Cleaner Bioremediation

CL-Out bioremediation reduced PCE concentrations in ground water by more than 99% in less than 90 days to achieve GCTL standards at a dry cleaners in Florida.   The naturally aerobic aquifer conditions supported the aerobic cometabolism of PCE.

It is observed at many sites that naturally aerobic conditions prevent the natural reduction of PCE and TCE.  This is obvious when the suite of contaminants include high concentrations of PCE or TCE without daughter products.  Instead of working against the natural conditions to drive the aquifer conditions anaerobic to facilitate reductive dechlorination, a more sustainable approach is to use CL-Out aerobic cometabolism to remove the parent compounds without producing daughter products.  This approach has been used at hundreds of sites such as this example in Florida.

Contact CL Solutions for more information about this approach.

 

Fast Dry Cleaner Remediation in California

CL-Out bioremedation at a dry cleaners in Southern California reduced PCE concentrations in soil and ground water by 85% and 90%, respectively, to achieve site closure standards in less than 30 days.  Keeping the site aerobic to eliminate the reductive dechlorination product vinyl chloride was critical to the rapid site closure.

CL-Out bioremediation is by aerobic cometabolism, which breaks the carbon bond in PCE and TCE instead of converting the molecules to DCE and vinyl chloride.  In order to maintain aerobic conditions during Cl-Out bioremediation, EHC-O, an oxygen supplement, was added during bioaugmentation.

The rapid remediation facilitates property transfers and redevelopment without disruption to property use and the construction schedule.

Fast Dry Cleaner Bioremediation

Case Study: Dry Cleaners Site, Southern California

Site Summary

CL-Out® bioremediation was implemented at a dry cleaners in southern California to remove dry cleaning solvents from soil and ground water. After one application of CL-Out® bioremediation the total chlorinated solvents concentration in ground water was reduced by 90%. The contaminant concentrations in soil were also reduced by an average of 85%. The remediation provided immediate risk reduction including avoiding vapor intrusion by vinyl chloride

Project Design and Implementation

The dry cleaning solvent was found in an area around a dry cleaning machine. The solvent entered the soil below the building and percolated through the soil to a perched ground water zone and an underlying second ground water zone. The soil and sediments are interbedded alluvial and marine sediments with a high permeability. The site was close to the beach, and ground water is influenced by tidal fluctuations. The impacted soil volume was approximately 80 cubic yards. The area of ground water impact and treatment was approximately 2,000 square feet.

Based on the volumes of impacted soil and ground water, five drums of hydrated CL-Out® were used. Two drums were injected into the soil and perched ground water beneath the dry cleaning machine. Three drums were injected into the deeper ground water in the diffused area of the plume. The total injection volume was less than .1% of the pore volume of the treated soil and ground water.

CL-Out® bioremediation destroys chlorinated solvents by aerobic cometabolism. Dextrose was added to provide the carbon source to support microbial growth. EHC-OTM by Adventus was added to maintain the aerobic conditions to support cometabolism and prevent potential production of vinyl chloride by indigenous bacteria.

Results

Post –treatment soil and ground water samples were taken approximately 30 days after the injection. The post-treatment soil samples were taken from locations adjacent to pretreatment sampling locations. The shallow soil samples all showed a decrease in solvent concentrations and no vinyl chloride was generated. Post-treatment ground water samples were obtained from existing monitoring wells and compared to previous sampling results. The perched ground water showed a decrease in PCE concentrations but a slight increase in TCE and DCE concentrations. The deeper ground water showed a decrease in all concentrations. Vinyl chloride was not detected in either the perched or deep ground water. The following table shows the contaminant concentration treads.

dry_cleaner_chart 6_11

The 30-sampling results show that the site is progressing toward fast closure. Additional ground water treatment is unlikely to be necessary to achieve site closure after sufficient post-treatment monitoring.

Industrial Dry Cleaning Facility located in Western New York

Site Summary

A CL-Out bioremediation push-pull pilot study was implemented at a confidential dry cleaners site to verify the applicability of CL-Out bioremediation to the site and to determine whether the availability of oxygen to support cometabolism of the halogenated solvents would limit the bioremediations.

Geology and Hydrology

Although the impacted ground water was relatively shallow, the site geology was complicated and varied across even this small site. In general the glacial deposits at the site were mainly till with interbedded sandy and silty zones. The impacted ground water was contained within the granular deposits.

Contamination

The main ground water contaminant was PCE with lower concentrations of TCE, cis -1,2 DCE and vinyl chloride. In the pilot study area, the PCE concentration was 44,200 μg/L and the total of the daughter products was 14,750 μg/L.

Pilot Study Design

A pilot study was completed in the source area in the fall of 2009. One unit of CL-Out was injected into the affected ground water in the source area. One unit of CL-Out is a 55-gallon slurry with a microbial concentration of 109 cfu/ml. The CL-Out microbes were injected with 50 pounds of dextrose to provide a carbon source to support the energy requirements of the population. Pre- and post -treatment samples were taken on February 19 and December 10, 2009. The post-treatment sample was taken after the monitoring well was purged of the injected volume. The following table shows the contaminant concentration trends in the treatment area.

dryclean8

Results

The pilot study verified the applicability of CL-Out bioremediation to the site. The total concentration of CVOCs was reduced from 59,000 to 13,740 μg/L. The CL-Out bioremediation was most effective in the removal of PCE and TCE. There was an increase in vinyl chloride suggesting some incomplete reductive dechlorination, probably by native dehalogenating organisms. Full-scale treatment will be most effective with the addition of an oxygen supplement to limit the dehalogenation and promote the cometabolism of the daughter products. Overall the push-pull pilot study verified the effectiveness of CL-Out bioremediation and provided insights for making full-scale application more effective.