Removal of Dimethyl Sulphide from Off-Gas Mixtures Containing Hydrogen Sulphide and Methanethiol by a Biotrickling Filter

Abstract

Long-term laboratory-scale experiments with a biotrickling filter were conducted to study a process capable of removing mixtures of odorous reduced sulphur 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 density of 9×105−3×108 cells ml−1. Two of the strains were isolated in pure cultures. The gas volumetric load was 53-178 m3 m−3 h−1 and the superficial liquid flow rate was between 25-87 l m−2 d−1. The sulphate toxicity level in the liquid phase was observed to be 15-20 g l−1. The efficiency 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 methanethiol-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 capacity of the gas mixture was 959 g m−3 d−1 (removal efficiency 79 %), which is higher than any previously reported figure. Saddle-shaped ceramics and plastic grits were also tested as potential packing materials. The biofilm in a biotrickling filter filled with plastics was not so resistant towards changes in pH or liquid circulation rate than that of one filter filled with ceramics.