Vinyl chloride biodegradation with methanotrophic attached films

Methanotrophic degradation of vinyl chloride (VC) is investigated using a laboratory-scale methanotrophic attached-film expanded-bed (MAFEB) bioreactor. This study provides a basis for applying a microbial cometabolizing reaction to practical treatment of toxic chlorinated compounds. The MAFEB reactor was operated at 20 °C with influent VC concentrations ranging from 1,800 to 9,600 μg/L and bed hydraulic retention times ranging from 3.7 to 7.6 h. VC effluent concentrations during steady continuous operation ranged from 3 to 140 μg/L, with most values less than 26 μg/L, resulting in removal efficiencies of 96.3% to 99.8%. The maximum continuous-flow VC degradation rate observed at 20 °C was 2.5 mg VC per gram volatile solids (VS) per day [2.5 mg VC/(g VS d)] or 30 mg VC per liter expanded bed per day 30 mg VC/Leb d), under substrate-limited conditions. During semibatch runs at 35 °C, vinyl chloride degradation rates up to 60 mg VC/(g VS d) or 1 g/(Lebd) were observed. Degradation rates increased with temperature between 20 °C and 35 °C, approximately doubling every 10 °C. Dissolved methane concentrations above 0.5 mg/L inhibited VC degradation, with no VC degradation observed with 8 mg/L dissolved methane. The methane consumed during VC degradation was about 40 g CH4/g VC. Toxic effects were observed after prolonged exposure of the methanotrophic culture to high concentrations of VC.