Pervaporation-biological oxidation hybrid process for removal of volatile organic compounds from wastewaters

A new pervaporation-biological oxidation hybrid process for the treatment o f wastewaters containing volatile organic compounds (VOCs) has been investi gated. The process combines pervaporation using a sweep gas with absorption and biological degradation of the permeate VOCs. A model system with monoc hlorobenzene (MCB) as the VOC and Pseudomonas JS150 as the degrading microo rganism was used for the study. Relatively high temperatures for the pervap oration operation were used, allowing the use of lower membrane area and lo wer sweep gas flowrate. The resulting higher concentration of VOC in the sw eep gas and the difference in temperatures between pervaporation unit and b ioreactor, were expected to improve the mass transfer of VOC from the gas i nto the biomedium, leading to a better VOC removal from the gas stream. The performance of this system, working at a constant gas flowrate and a biore actor temperature of 30 degreesC, was studied for step increases in pervapo ration temperature. Raising the temperature was shown to increase the mass transfer flux in the membrane module. Bioreactor removal efficiencies close to 100% were obtained throughout, and an elimination capacity of 84 g (MCB ) m(-3) h(-1) was attained. The system was then run with a lower bioreactor temperature (15 degreesC), in order to accurately quantify changes in remo val efficiency with varying pervaporation temperature. In this case, a cons tant VOC load was fed to the bioreactor, with reductions in gas flowrates c oncomitant with increasing pervaporation temperatures. It was shown that us ing lower gas flowrates with higher VOC concentrations, at higher temperatu res, resulted in significantly improved removal efficiencies. Concentration s of 17 g m(-3) of MCB1 were treated in the bioreactor working at 15 degree sC, with removals of 95%. (C) 2002 Elsevier Science B.V. Ail rights reserve d.