Impact of nutrients supply and pH changes on the elimination of hydrogen sulfide, dimethyl disulfide and ethanethiol by biofiltration

The treatment of sulfur odorous compounds in mixture, Hydrogen sulfide (H2S), dimethyl disulfide (DMDS) and ethanethiol (EtSH), by biofiltration was examined. A significant effort was focused on the impact of nutrients supply, without forgetting the effect of other parameters such as the pH, on the process performances. Removal efficiencies of three biofilters packed with pine bark and composted wood mulch and sprinkled by different nutritive solutions were compared. Owing to the biodegradability of H2S, its removal was not affected by the lack of nutrients in the biofilter. However, for EtSH and DMDS, considered as more recalcitrant, the influence of nutrients on biodegradation was clearly observed; it was enhanced when the supplementation in the watering solution was increased. Furthermore, EtSH removal yield increased from 80% in the absence of supplementation to an almost total removal in the presence of nutrients in the watering solution. The degradation of the three compounds decreased as follows: H2S > DMDS > EtSH. The impact of the pH of the packing materials was also underlined. The decrease in pH caused by the accumulation of sulfuric acid in the packing material, the most abundant product of the biological oxidation of sulfur compounds, led to a reduction of the elimination efficiencies of EtSH and DMDS; while the microorganisms involved in H2S degradation appeared active in a large pH range, from less than 3 to close to 9.