Dechlorination of Tetrachloroethene Influence of Tetrachloroethene and Methane in Batch Cultivation under Methanotrophic Conditions in the Presence of Oxygen KLAG 1* ,P.,WELTZIN 2 ,M.,EISENTRÄGER 2 ,A.,DOTT 2 ,W.,RÜDEN 1 ,H. 1 Technische Universität Berlin Fachgebiet Hygiene Amrumer Straße 32 13353 Berlin, Germany 2 Rheinisch-Westfälische Technische Hochschule Aachen Institut für Hygiene und Umweltmedizin Pauwelsstraße 30 52057 Aachen, Germany Summary The feasibility of combining the reductive dechlorination and oxidative mineralization of tetrachloroethene (PCE) within one system was investigated in non-shaken methanotrophic batch cultivated cell suspensions. In the presence of up to 90% [v/v] methane and 10% [v/v] oxygen in the headspace, 200, 400 and 500 μmol/l PCE were completely dechlorinated over 100 days of incubation with 1% [v/v] activated sludge derived from a municipal wastewater treatment plant (equivalent to 6 mmol/l carbon). Meanwhile nearly 4 mol/l chloride were released to the medium for each mol PCE dechlorinated, indicating that the volatile chlorinated compound was completely dechlorinated in the cell suspensions. Irrespectively of the initial PCE concentration, 40 μmol/l trichloroethene were found temporarily. According to the initial PCE concentration, up to 160 μmol/l cis-dichloroethene were measured in the assays with 500 μmol/l PCE. In the presence of oxygen in the headspace, simultaneously with the dechlorination, methane was oxidized. At 7% [v/v] methane and 10% [v/v] oxygen, 500 μmol/l PCE were dechlorinated to cDCE within 145 days. At PCE concentrations of 600 μmol/l or above, substrate inhibition occurred, and then both the dechlorination and the oxidation of methane were inhibited. Introduction Tetrachloroethene (PCE), a common organic pollutant found in aquifers [1–4], is only degradable under anaerobic conditions [5]. Cometabolic [6, 7] and respiratory [8–10] transformations are known. Research with pure cultures showed that the transformation * Corresponding author E-mail: P.Klag@d2mail.de Acta Biotechnol. 21 (2001) 2, 129–139