Removal of aqueous phase trichloroethylene using membrane air stripping contactors

This work investigates the use of membrane air-stripping (MAS) contactors containing microporous polypropylene hollow-fiber membranes to remove volatile organic compounds from water into the gas phase. Experiments using countercurrent and cross-flow flow configurations to remove trichloroethylene (TCE) from water into air were performed. The effects of influent TCE concentration, liquid and gas flow rates, and air-to-water ratio were investigated. In each case studied, it was found that mass transfer in MAS contactors is controlled by liquid-phase resistance. Maximum removal of TCE was obtained at air-to-water ratios that were significantly lower than those required for conventional packed-tower stripping. Mathematical models based on empirical correlations for the liquid-phase convective mass transfer coefficients were developed and validated with experimental data, and subsequently used to perform simulations of full-scale MAS contactors. At the operating conditions explored, full-scale cross-flow contactors were shown to be superior to countercurrent-flow contactors: for the same gas and liquid flow rates and number of fibers, cross-flow contactors removed more than 95% of the original TCE in the feed liquid whereas countercurrent-flow contactors removed less than 50%. In comparison with packed-tower stripping, MAS contactors are shown to be an alternative feasible technology.