ATOKA Bioremediation Project
ATOKA provided conventional remediation and in-situ bioremediation services for a confidential client in Bentonville, Arkansas during 2014 - 2015. The primary contaminant was tetrachloroethylene (PCE), a solvent used in dry cleaning fluids. The contaminant was found from the ground surface to the water table at approximately 27 feet below ground surface. ATOKA provided all site characterization services, remediation design and remediation oversight. Actual remediation was subcontracted under the supervision of ATOKA. Conventional remediation included the excavation of contaminated soils to approximately 15 feet below ground surface. The remaining depth to bedrock, including the perched groundwater aquifer was treated in-situ using a commercial mixture of bioremediation and oxidizing agents.
This bioremediation project utilized injected microbial organisms that accelerated the natural breakdown of PCE to ethene, a simple hydrocarbon with low toxicity that biodegrades quickly in the presence of oxygen and sunlight and is unlikely to adversely affect terrestrial life (DOW, 2014). The chemical breakdown occurs by the transformation of the PCE molecule to trichloroethylene (TCE), then to dichloroethylene (DCE), then to Vinyl Chloride (VC), and finally to ethene.
The chemical concentrations of the breakdown process were monitored on a weekly basis and then monitoring was reduced to a monthly basis. The core area of concern had PCE concentrations reduced by more than 90 percent within only a few weeks. Each of the breakdown chemicals expected was identified and graphed to assure that the remediation process was taking place as expected. This particular method of remediation is highly effective, and commonly used, for chlorinated solvents, such as PCE, select toxic metals, nitrated explosives, perchlorate and nitrate.
Dow, 2014. Product Safety Assessment Ethylene Form No. 233-00280-MM-0714X, The Dow Chemical Company, revised July 1, 2014.





