Continuous Cometabolic Transformation of 4-Chlorophenol in the Presence of Phenol in a Hollow Fiber Membrane Bioreactor

An immobilized cell hollow fiber membrane bioreactor was operated continuously for the cometabolic transformation of 4-cp in the presence of phenol. In contrast to the batch operation of the bioreactor in which the immobilized cells were exposed to decreasing substrate concentrations, at high substrate concentrations, under continuous operation, dissolved oxygen was found to be a limiting nutrient. It was found that substrate degradation was enhanced by aerating the feed with pure oxygen. It was also found that the optimum number of hollow fibers in the bioreactor was 25, ca. 30% bioreactor volume. This occurred due to a balance of the pore space available for cell immobilization in the fibers against the extracapillary space available for suspension cell growth. During continuous operation, regardless of feed rate (21–60 mL·h^-1), the maximum substrate loading was found to be 9 mg·h^-1 each of phenol and 4-cp in order that both substrates were completely transformed. In anticipation of reduced provision of phenol as a specific growth substrate for 4-cp cometabolic transformation, it was concluded that complete transformation of 4-cp could be effected through a minimum substrate concentration ratio of phenol:4-cp of 1:1.8.