EFFECTS OF PHENOL FEEDING PATTERN ON MICROBIAL COMMUNITY STRUCTURE AND COMETABOLISM OF TRICHLOROETHYLENE

Cometabolism of trichloroethylene (TCE) by phenol-fed enrichments was evaluated in four reactors with distinct phenol feeding patterns, The reactors were inoculated from the same source, operated at the same av erage dilution rate, and received the same mass of phenol over time, O nly the timing of phenol addition differed, Reactor C received phenol continuously; reactor SC5 received phenol semicontinuously-alternating between 5 h of feed and 3 h without feed; reactor SC2 alternated betw een 2 h of feed and 6 h without feed; and reactor P received a single pulse every 24 h. The structure of the enrichments and their capacity for TCE transformation were analyzed, In long-term operation, reactors C and SC5 were dominated by fungi, had higher levels of predators, we re more susceptible to biomass fluctuations, and exhibited reduced cap acity for TCE transformation, Reactors P and SC2 were characterized by lower levels of fungi, higher bacterial biomass, higher concentration s of TCE-degrading organisms, and higher rates of TCE transformation, After 200 days of operation, rates of TCE transformation increased 10- fold in reactor P, resulting in TCE transformation rates that were 20 to 100 times higher than the rates of the other reactor communities, T he cause of this shift is unknown, Isolates capable of the highest rat es of TCE transformation were obtained from reactor P. We conclude tha t cometabolic activity depends upon microbial community structure and that the community structure can be manipulated by altering the growth substrate feeding pattern.