Aerobic PCE Cometabolism

Pilot Study Confirms Aerobic Cometabolism of PCE at Kentucky Site

A CL-Out bioremediation pilot study confirmed the PCE could be removed from ground water by aerobic cometabolism.  The pilot study was at the former location of a dry cleaners where PCE wasfound in ground water at 27 parts per billion (ppb).  CL-Out micorbes and dextrose as the metabolic substrate were injected into the ground water upgradient 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 1.07 mg/L to 0.71 mg/l and the ORP decreased from 99 to 45 mv.

CL-Out cometabolism used 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.



Compatible Technologies to Improve In-Situ Remediation of Chlorinated Solvents: A Case Study

A chlorinated solvent plume (perchloroethylene or PCE) was discovered
in the shallow ground water as a result of historical operating practices surrounding a
Houston area dry cleaning facility. 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 ongoing 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.

Click here for a link to the full report from the 2007 Battelle Conference on Bioremediation


In-Situ Aerobic Soil and Ground Water Bioremediation of PCE and TCE

CL-Out bioremediation of chlorinated solvents like PCE and TCE is an aerobic cometabolic process.  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 enzymes mono- and dioxygenase that bridge the carbon bond to destabilize the compound.  The solvent is converted to an organic acid that the organism can metabolize.  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 513-284-9540.

Case Study of In-Situ Bioremediation of Recalcitrant Organics

A history of spills and/or releases at two adjacent dry cleaning facilities near Houston, TX, resulted in significant soil and shallow groundwater contamination with PCE and daughter products. Soil was relatively permeable, with rapid groundwater flow beneath the site. A long, narrow, off-site plume extended beneath a residential neighborhood. Chemical oxidation was employed initially with only limited success in the areas of highest contamination. To take advantage of the soil permeability and other site conditions, the response action was amended to include enhanced aerobic bioremediation by cometabolism. Specialty microbes were introduced into the plume in several injections over a 15-month period. This approach achieved total contaminant level reductions in the source area from 1,600 to less than 40 µg/L, and at the front edge of the plume, levels decreased from 500 to 5 µg/L.

For the full case study click here:

Brusenhan, J.D., M.F. Marcon, and M.T. Saul, CL-Solutions, LLC. A&WMA’s 98th Annual Conference and Exhibition, 21-24 June 2005, Minneapolis, Minnesota, Paper 1069, 10 pp, 2005

Dry Cleaner Bioremediation and Brownfield Redevelopment

Site Description

Dry cleaning solvent spills in a storage area lead to the contamination of soil and ground water on the property of a 50-year-old dry cleaners in the middle of a hot brownfield redevelopment.   After the contaminated soil was excavated for off site disposal to the most practical extent, residual perched ground water contamination impacted the redevelopment of the property.

The soil excavation was used as an infiltration gallery as part of a recirculating ground water recovery and treatment system.  The flushing reduced contaminant concentrations, but the levels were still far above the levels required to achieve no further action status.  CL-Out was added to the recirculating ground water and the cleanup goals were achieved in less than two years and were maintained through two years of  post treatment monitoring.

Site Characteristics

Geology and Hydrogeology

The site is on a fluvial terrace adjacent to the Ohio River.  The shallow soils are clayey silts to sit to eight feet deep.  An interbedded sandy zone that formed the first water-bearing zone was encountered from 8 to 12 feet deep.  Perched ground water occurred in the sandy zone at 12 feet below grade.

Ground Water Contamination

 The size of ground water plume that resulted from the spills was estimated to be 3,500 square feet.    The ground water contamination was mainly PCE with a maximum concentration of 11,000 ug/l prior to soil removal or ground water treatment.  The daughter compounds TCE and DCE were detected up to 17 and 12 ug/l respectively.  After three years of recirculation and flushing, the maximum PCE concentration was reduced to 2.3 ug/l and the daughter compounds were below detection limits.


CL-Out bioaugmentation was implemented to supplement the flushing system.  By adding CL-Out on two occasions over two years, the contaminant concentrations were reduced to below drinking water standards.  During two years of post treatment monitoring the DCE concentrations rebounded to above the MCLs.  CL-Out bioaugmentation was implemented again and within three months the contaminant levels were below drinking water standards and remained below drinking water standards for nine months.  After post closure monitoring verified the cleanup goals would be maintained, the KDEP issued a “No Further Action” letter for the site.

The following chart shows the PCE contaminant trend in one of the key monitoring wells during the remediation and post closure monitoring.


The CL-Out cost during this remediation project was less than $10,000.