Removal of dimethyl sulphide from off-gas mixtures containing hydrogen sulphide and methanethiol by a biotrickling filter

Long-term laboratory-scale experiments with a biotrickling filter were cond ucted to study a process capable of removing mixtures of odorous reduced su lphur compounds from off-gases. The biotrickling filter was inoculated with a consortium of microorganisms enriched from the sludge water of a Finnish refinery. Its liquid phase contained from 4 to 6 microorganisms at a densi ty of 9x10(5)-3x10(8) cells ml(-1). Two of the strains were isolated in pur e cultures. The gas volumetric load was 53-178 m(3) m(-3) h(-1) and the sup erficial liquid flow rate was between 25-871 m(-2) d(-1). The sulphate toxi city level in the liquid phase was observed to be 15-20 g l(-1). The effici ency of dimethyl sulphide (Me2S) removal with a concentration of 77 (+/-13) mg m(-3) Me2S-S was found to be 78 (+/-9) % when the concentration of meth anethiol-sulphur (MeSH-S) in the gas mixture was below 21 mg m(-3) (removal efficiency over 97 %) and that of hydrogen sulphide-sulphur (H2S-S) below 200 mg m(-3) (removal efficiency over 99 %). The maximum Me2S-S removal cap acity of the gas mixture was 959 g m(-3) d(-1) (removal efficiency 79 %), w hich is higher than any previously reported figure. Saddle-shaped ceramics and plastic grits were also tested as potential packing materials. The biof ilm in a biotrickling filter filled with plastics was not so resistant towa rds changes in pH or liquid circulation rate than that of one filter filled with ceramics.