REMEDIATION SECTION

Bioremediation of Chlorinated
Solvents in Ground Water:
Low Cost and Fast Closure

BIOREMEDIATION OF CHLORINATED SOLVENTS
Tetrachloroethylene (PCE) and other chlorinated solvents are common soil and ground water contaminants found at many industrial sites. Their widespread occurrence is the combined result of their use in industries ranging from dry cleaning to microelectronics manufacturing and the persistence of the chemicals in the natural environment. Traditional mass-transfer remediation systems such as pump-and-treat and soil vapor extraction have limited success in achieving the low cleanup standards for these suspected human carcinogens. Recent advances in bioremediation have provided an alternative remediation technology that has proved cost-effective and rapid in reaching drinking water standards in ground water.

Cl-out is a patented consortium of naturally occurring microbes selected for their ability to both cometabolize PCE and trichloroethylene (TCE) and directly metabolize their breakdown products. The Cl-out microbes are aerobic so
Cl-out bioremediation is possible in most soil and aquifer conditions.

CL-OUT BIOREMEDIATION
The Payne Firm has used Cl-out bioremediation at several industrial and dry cleaning sites contaminated by PCE. These sites have generally shown contaminant concentration reductions of 60% to 90% in 90 days. Drinking water standards were achieved at two sites in less than one year. At one of these sites, Cl-out bioremediation was implemented at a former printing facility where a drum storage pad was removed and shallow soil was excavated
for off-site disposal. The residual concentrations of PCE in soil were greater than 1.0 mg/kg and ground water concentrations in the source area were as much as 11 mg/l. Pump-and-treat removal reduced the PCE concentrations to 1.0 mg/l in six months, but the concentrations remained at that level. Cl-out bioremediation originally augmented and ultimately replaced the pump and treat system. After one year of Cl-out bioremediation the PCE concentration in ground water has been reduced to less than 10 mg/l. The bioremediation of the site cost less than $25,000.

APPLICABILITY
The effectiveness of Cl-out bioremediation is most dependent on subsurface permeability and dissolved oxygen levels. Sites having permeable soils that allow good distribution of microbes and dissolved oxygen recharge are ideal for Cl-out bioremediation. Sites having less than ideal conditions may take longer to remediate or may be inappropriate for Cl-out bioremediation. In all cases, site-specific conditions determine whether applicable cleanup goals are attainable in a short timeframe and the project cost.

SUMMARY
Bioremediation is a cost-effective remediation alternative for chlorinated compounds in soil or ground water. If you wish to discuss whether bioremediation may be applicable at your site, please contact Mike Saul or Mike Woodruff toll free at 800.229.1443 or through e-mail at mts@paynefirm.com or mlw@paynefirm.com.