Biodegradation of tetrachloroethylene in upflow anaerobic sludge blanket reactor

The laboratory study using upflow anaerobic sludge blanket (UASB) reactor in high strength wastewater containing tetrachloroethylene (PCE) was carried out to develop granular sludge in the presence of PCE (2 mg/l) and to assess the potential of UASB reactor in treating PCE containing wastewater. The granules of 0.25-4 mm size were observed after 82 days having mostly Methanothrix and Methanosarcina bacteria. Influent PCE concentration of 5-50 mg/l decreased to less than 0.23 mg/l (98.5 +/- 1% removal) in most cases. The trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), vinyl chloride (VC) and ethylene were formed on dehalogenation of PCE. Under steady state operation conditions the COD removal of 94 +/- 2% and biogas production of 0.559-0.508 m(3)/kg CODrem with methane content of 64 +/- 2% was achieved. The maximum PCE dechlorination rate (q(max)), was 14.28 mg PCE/g VSS d and the half velocity coefficient, (K-s), was 0.417 mg PCE/l under steady state conditions. The UASB reactor may prove to be a potential wastewater treatment process for PCE containing wastewater. (C) 1999 Elsevier Science Ltd. All rights reserved.