Novel membrane bioreactor with gas/liquid two-phase flow for high-performance degradation of phenol

The use of a membrane bioreactor with cell retention to achieve high biomas s concentrations has been examined for phenol degradation by the bacteria A lcaligenes eutrophus. This process is particularly interesting for toxic su bstrates as the hydraulic dilution rate and the growth rate are independent ly controlled. In the case of a transitory excess of phenol, this potential ly toxic situation can be overcome by modifying the substrate concentration or the dilution rate without any loss of cells. The injection of a gas pha se at the filter inlet increased both the permeate flow rate (by a factor o f 1.75) and the oxygen transfer capacity (by a factor of 1.5). This has ena bled the cell concentration to reach a maximal value of 60 g L-1 with a hyd raulic dilution rate of 0.5 h(-1) and a phenol feed concentration of 8 g L- 1. The volumetric productivity of this process corresponds to a phenol degr adation rate approaching 100 kg m(-3) day(-1) The on-line measurement of th e characteristic yellow color of 2-hydroxymuconate semialdehyde, a metaboli c intermediate of the phenol degradation pathway, in the permeate provides an interesting basis for process control of phenol supply into the reactor since the color intensity correlates directly to the specific rate of pheno l degradation.