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 $30\mathrm{mg}\mathrm{VC}/L_{\mathrm{eb}}d$), under substrate‐limited conditions. During semibatch runs at 35°C, vinyl chloride degradation rates up to 60 mg VC/ (g VS d) or $1g/\left(L\mathrm{eb}d\right)$ 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 $40g{\mathrm{CH}}_4/g\mathrm{VC}$. Toxic effects were observed after prolonged exposure of the methanotrophic culture to high concentrations of VC.