Two-phase biodegradation of phenol in a hollow fiber membrane bioreactor

Abstract

A hollow fiber membrane bioreactor (HFMB) was employed for aqueous-organic two-phase biodegradation of phenol using Pseudomonas putida ATCC 11172, and the results were compared with that in a two-phase partitioning bioreactor (TPPB). Phenol containing 2-undecanone was nondispersively contacted with mineral medium that was inoculated with the bacteria. P. putida in suspension was able to biodegrade inhibitory phenol concentrations at 600-2,000 mg/L without experiencing severe substrate inhibition. For example, 1,000 mg/L phenol was completely biodegraded in 46 h at a maximum specific growth rate of 0.49 h-1, whereas the biomass yield and average biodegradation rate were 0.36 g/g and 62 mg/L·h, respectively. Biomass yield and maximum specific growth rate decreased concomitantly with increasing phenol concentration. Phenol removal started at an exponential rate, and subsequently attained a linear profile in nutrient-limited conditions. Unlike conventional two-phase biodegradation systems, HFMB offered a better growth environment for the cells, as evident from the absence of the lag phase. The HFMB was more environmentally friendly and offered ease of operation and analysis that could mitigate the problems of foaming and emulsification that are associated with conventional TPPBs. In evaluating the effects of membrane area on biodegradation rate, the writers found that by doubling the interfacial area, 2,000 mg/L phenol could be mineralized within 43 h with improved growth and removal rates. For comparable mass transfer flux across the aqueous-organic interface, biodegradation was faster in the HFMB relative to that in TPPB. © 2013 American Society of Civil Engineers.