Transformation of 1,1,1-trichloroethane in an anaerobic packed-bed reactor at various concentrations of 1,1,1-trichloroethane, acetate and sulfate deBest, JH; Jongema, H; Weijling, A; Doddema, HJ; Janssen, DB; Harder, W Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract Biotransformation of 1,1,1-trichloroethane (CH 3 CCl 3 ) was observed in an anaerobic packed-bed reactor under conditions of both sulfate reduction and methanogenesis. Acetate (1 mM) served as an electron donor. CH 3 CCl 3 was completely converted up to the highest investigated concentration of 10 lM. 1,1-Dichloroethane and chloroethane were found to be the main transformation products. A fraction of the CH 3 CCl 3 was completely dechlorinated via an unknown pathway. The rate of transformation and the transformation products formed depended on the concentrations of CH 3 CCl 3 , acetate and sulfate. With an increase in sulfate and CH 3 CCl 3 concentrations and a decrease in acetate concentration, the degree of CH 3 CCl 3 dechlorination decreased. Both packed-bed reactor studies and batch experiments with bromoethanesulfonic acid, an inhibitor of methanogenesis, demonstrated the involvement of methanogens in CH 3 CCl 3 transformation. Batch experiments with molybdate showed that sulfatereducing bacteria in the packed-bed reactor were also able to transform CH 3 CCl 3 . However, packed-bed reactor experiments indicated that sulfate reducers only had a minor contribution to the overall transformation in the packed-bed reactor.