Development of a novel bioreactor system for treatment of gaseous benzene

A novel, continuous bioreactor system combining a bubble column (absorption section) and a two-phase bioreactor (degradation section) has been designe d to treat a gas stream containing benzene. The bubble column contained hex adecane as an absorbent for benzene, and was systemically chosen considerin g physical, biological, environmental, operational, and economic factors. T his solvent has infinite solubility for benzene and very low volatility. Af ter absorbing benzene in the bubble column, the hexadecane served as the or ganic phase of the two-phase partitioning bioreactor, transferring benzene into the aqueous phase where it was degraded by Alcaligenes xylosoxidans Y2 34. The hexadecane was then continuously recirculated back to the absorber section for the removal of additional benzene. All mass transfer and biodeg radation characteristics in this system were investigated prior to operatio n of the integrated unit, and these included: the mass transfer rate of ben zene in the absorption column; the mass transfer rate of benzene from the o rganic phase into the aqueous phase in the two-phase bioreactor; the stripp ing rate of benzene out of the two-phase bioreactor, etc. All of these para meters were incorporated into model equations, which were used to investiga te the effects of operating conditions on the performance of the system. Fi nally, two experiments were conducted to show the feasibility of this syste m. Based on an aqueous bioreactor volume of 1 L, when the inlet gas flow an d gaseous benzene concentration were 120 L/h and 4.2 mg/L, respectively, th e benzene removal efficiency was 75% at steady state. This process is belie ved to be very practical for the treatment of high concentrations of gaseou s pollutants, and represents an alternative to the use of biofilters. (C) 2 000 John Wiley & Sons, Inc.