SUSTAINED TRICHLOROETHYLENE COMETABOLISM BY PHENOL-DEGRADING BACTERIA IN SEQUENCING BIOFILM REACTORS

Bench-scale studies of a sequencing packed-bed bioreactor were conducted for the treatment of waters contaminated with trichloroethylene (TCE). The reactor contained a mixed-culture biofilm grown aerobically on phenol; the biofilm cometabolized TCE in the absence of phenol. These studies focused on the effect of phenol-feeding strategies in relation to sustaining high levels of TCE removal efficiency. The reactor was cycled between a rejuvenation stage, during which phenol at 5, 25, or 100 mg/L was supplied in a nutrient water, and a degradation stage, during which TCE was supplied as a contaminant at 100 mu g/L in the absence of phenol. Two to three hours of rejuvenation per 24 hours of TCE degradation were required for stable operation. Pseudo-first-order rate constants for TCE degradation between 50 and 100 L/g volatile suspended solids . d were sustained for up to 29 days. The successful feeding strategies yielded average TCE removals between 70 and 90% at a packed-bed hydraulic residence time of 14 minutes. Conceivably, a full-scale sequencing reactor could operate indefinitely with the proper feeding strategy.