Trichloroethylene degradation by Methylosinus trichosporium OB3b mutants in a sequencing biofilm reactor

Abstract

Methylosinus trichosporium OB3b was used in a sequencing biofilm reactor to degrade trichloroethylene (TCE) in water at approximately 100 μg/l influent concentration. The reactor consisted of biofilms grown on diatomaceous earth pellets or glass beads, and was sequenced between growth cycle, in which methane and air were fed in a gas phase, and degradation cycle, in which the column was completely liquid-filled. Biomass loading on the support media was only 10 mg cell dry weight/g support media, giving a calculated biofilm thickness of 0.04 cm. Apparent psuedo-first order degradation rate constants in the system were improved by more than an order of magnitude, from 0.008 l/mg d to 0.1 l/mg d, through the use of antibiotic-resistant strains of copper-resistant organisms that express only the soluble methane monooxygenase, the enzyme responsible for trichloroethylene degradation. Also, biomass accumulation was improved through the use of a cationic coagulating polymer. However, TCE degradation was sustained only for short times, and cycling back to growth mode did not completely regenerate TCE degradation ability. Thus, biofilms of Methylosinus trichosporium OB3b did not give rise to sustained high degradation rates.