Cometabolic treatment of chlorinated solvents: influence of operational conditions on the adaptation of indigenous biomasses

The effect of several operational conditions on the adaptation of indigenous biomasses was investigated in a microcosms study of chloroform (CF) cometabolic degradation with butane. The objective was to minimize the duration of the adaptation phase and the amount of growth substrate to provide in field applications. The adaptation to butane and CF was monitored at 5 concentrations of butane (1.50, 1.00, 0.50, 0.25 and 0.10 mg/L), at 3 concentrations of CF (1, 5 and 10 mg/L), at 4 temporal sequences of exposition to butane (continuous, 5 h/d, 7 h/d, 24 h every other day) and at 3 temperatures (15, 25 and 30°C). The results indicate that the most favorable condition for the adaptation of indigenous biomasses consists in the continuous exposition to a very low concentration of growth substrate (0.1 mg/L). In all the tests the degradation of CF started within 48 days. The microbiological characterization of the consortia indicated that the prolonged degradation of CF led to the selection of 3 specific butane-utilizing strains.