The effect of inoculation and the type of carrier material used on the biofiltration of methyl sulphides

Low elimination capacities (less than 10 g m(-3) day(-1)) were observed for the odorant dimethyl sulphide (Me(2)S) when either wood bark or compost was used as the carrier material in a laboratory-scale biofilter. Enrichment experiments were set up by incubation of garden soil samples during 4 weeks with 100 ppm (v/v) headspace concentrations of both Me(2)S and dimethyl disulphide (Me(2)S(2)). After transfer to a mineral medium, Me(2)S- and Me(2)S(2)-degrading enrichment cultures were obtained for all five soil samples tested, both compounds being converted stoichiometrically to sulphuric acid. Upon inoculation of the laboratory-scale biofilter with one of these enrichment cultures( +/- 120 g cell dry weight m(-3) reactor), the elimination capacity for Me(2)S increased in a 3-week period to 35 g m(-3) day(-1) and 680 g m(-3) day(-1) when wood bark and compost were used as the respective carrier materials. Both inoculated biofilters were able to degrade Me(2)S(2), however the elimination capacities obtained for Me(2)S(2) were lower (e.g. 24 g m(-3) day(-1) for the wood bark filter) compared to those for Me(2)S. For both inoculated biofilters, a gradual decrease of the elimination capacity for the methyl sulphides was observed as a result of acidification of the carrier material, suggesting that pH regulation is necessary if long-term biofiltration experiments are to be performed.