Simultaneous extraction and biodegradation of phenol in a hollow fiber supported liquid membrane bioreactor

Abstract

A hollow fiber supported liquid membrane bioreactor (HFSLMB) was developed for two phase biodegradation of phenol. 2-undecanone dispersed into phenolic wastewater was indirectly contacted with the cell culture through the supported liquid membranes. The semi-dispersive approach stabilized the liquid membrane and facilitated non-dispersive transport of substrate from the solvent to the cells. Pseudomonas putida could biodegrade phenol at 1000-4000mgL-1 without experiencing severe substrate inhibition. For example, 4000mgL-1 phenol was biodegraded within 76h while the specific growth rate and biomass yield were 0.31h-1and 0.26g/g, respectively. Substrate removal occurred in two sequential steps: removal during log growth phase and removal under diffusion limitation. The biodegradation rates could be enhanced by changing the phase ratio, hydrodynamic conditions and the interfacial area. Repeated batch runs were conducted for more than 400h to evaluate long term stability of the HFSLMB. Bioreactor performance deteriorated after 5 runs (approximately 100h) due to the presence of biofilms on the membrane but a proposed 5h washing cycle after every 100h of operation could restore the performance. These results suggest that the HFSLMB can be a promising alternative to conventional two-phase partitioning bioreactors. © 2012 Elsevier B.V.