BIOFILTRATION OF AIR CONTAINING LOW CONCENTRATIONS OF PROPENE USING AMEMBRANE BIOREACTOR

Volatiles with a low water solubility are difficult to remove from air by biofiltration, especially when present in low concentrations, beca use the driving force for mass transfer into the aqueous phase is very small. We have used a microporous hydrophobic membrane as a support f or biofilms that remove the poorly soluble propene from air. Two bacte rial strains were compared, and the faster growing strain, Xanthobacte r Py2, was selected to study biofilm formation and reactor performance at propene concentrations in the range encountered in off-gas treatme nt. With a concentration of 200-350 ppm of propene in the gas phase a 20-day start-up period was required for the formation of a biofilm on the membrane. Once the biofilm had been established, continuous propen e removal was tested over a range of concentrations. The amount of act ive biomass adapted to the amount of propene available. When the membr ane bioreactor was operated with propene concentrations as low as 9-30 ppm in the gas phase, the propene removal rate was stable for several weeks, without the supply of any other source of carbon or energy to the microbial population.