Environmental Projects

Successful Full Scale Bioremediation of a 500 ppm 1,1,1 TCA Source
(Massachusetts)

INNOVATIVE ENGINEERING SOLUTIONS, INC. is implementing a highly successful full scale enhanced anaerobic dechlorination (EAD) of 1,1,1 TCA (TCA) bioremediation project. 1,1,1 TCA bioremediation is significantly more challenging than bioremediation of tetrachloroethene (PCE) and trichloroethene (TCE) series compounds. TCA transformation often occurs under complex methanogenic and sulfate reducing conditions by the dehalobacter microorghanism. The source area at the project site (moderately permeable medium sand w/ a low hydraulic gradient) is approximately 1 acre and several wells contained 300 to 600 ppm of TCA prior to bioremediation (current post remediation concentrations are in the small single digits). The area of treatment also contained 2-30 ppm of TCE from an upgradient source. Initial site groundwater conditions indicated minimal biotic dechlorination and the presence of up to 20 ppm nitrate and 90 ppm sulfate. Our microcosm testing indicated that TCA dechlorination is inhibited by the site's relatively low pH (5 to 5.5) and high TCA concentration. Once pH was adjusted and TCA concentrations were reduced to less than 100-200 ppm (by dilution with site water, emulsified vegetable oil addition), dechlorination proceeded rapidly using whey/ alcohol and vegetable oil as electron donors.

The bioremediation program has been extremely successful to date and has reduced VOC concentrations in all wells and generated significant concentrations of chloroethane (CA). Even in the most contaminated wells molar concentrations of CA far exceed TCA molar concentrations, whereas at the beginning of site remediation negligible CA and 1,1 DCA concentrations were observed. To date, we have added approximately 60,000 lbs. of carbon source electron donor. The project demonstrates techniques to cost effectively remove inhibition and the value of whey/alcohol/vegetable oil mixtures (IESI proprietary) as an electron donor for TCA dechlorination.

To the best of our knowledge this project represents the first demonstrated full scale EAD application for inhibitory concentrations of 1,1,1 TCA.