Removal of dimethyl sulfide from waste air in a membrane bioreactor

Long-term experiments with a membrane bioreactor to remove dimethyl sulfide (Me2S) from waste air are reported for the first time. The membrane bioreactor contained a polydimethylsiloxane/Zirfon composite membrane and was inoculated with Hyphomicrobium VS, a methylotrophic micro-organism. The optimal conditions of pH (67) and sulfate contents (< 8 g SO42–-S.L–1) for maximum Me2S-degradation were determined in batch studies and applied during membrane biofiltration. Dimethyl sulfide conversion depended both on gas residence time and inlet concentration. The removal efficiency of air contaminated with 38 mg Me2S.m–3 was found to be 99% at 24 s, 90% at 12 s and 85% at 8 s gas residence time. At a gas residence time of 24 s, removal efficiencies of 99%, 93% and maximum 87% were observed for Me2S concentrations of 33 mg.m–3, 116 mg.m–3 and 375 mg.m–3, respectively. The maximum elimination capacity was 4.82 kg Me2S.mr–3.d–1 (efficiency of 74%) which is higher than ever obtained with the conventional biofilters and biotrickling filters.

A membrane bioreactor appears to be a promising biotechnique for the treatment of waste gases containing Me2S. Dimethyl sulfide conversion depended both on gas residence time and inlet concentration. At higher residence times and lower Me2S concentrations, better removal efficiencies were observed. A maximum elimination capacity of 4.82 kg Me2S.mr–3.d–1 was obtained (efficiency of 74%), which is higher than any reported ECv during biofiltration or use of biotrickling filters. The rapid and stable response of the bioreactor on changing parameters demonstrates the application of this reactor for treatment of variable VOSC emissions. The incorporation of a composite membrane was investigated for the first time and proves, after 80 d of operation, to maintain stable reactor performance. This new type of bioreactors can be successful for treatment of emissions containing poorly-water-soluble pollutants, acidifying compounds or pollutants which need specific micro-organisms because of lack of biodegradability.