Elimination of hydrogen sulfide from biogas by a two-stage trickling filter system using effluent from anaerobic-aerobic wastewater treatment

This study presents a two-stage desulfurization system based on two trickling filters (TFs): a first-stage closed type TF (1st TF) and an open-type second-stage TF without aeration (2nd TF). The effluent from an anaerobic aerobic wastewater treatment system served as the water source, and coconut chips were used as the packing media for both the TFs. The concentration of hydrogen sulfide in the biogas ranged from 80 to 2300 ppm (v/v) with an average concentration of 737 ppm. The 1st TF eliminated more than 99% of the hydrogen sulfide at a loading rate of 5.24 gS-H-2 m(-3)h(-1). Subsequently, 50.0% of the eliminated hydrogen sulfide was oxidized to sulfate in the 2nd TF without aeration. The two-stage TF system additionally eliminated 53.1% of ammonia from among which 52.6% was detected as nitrate in the effluent of the 2nd TF. Additionally, 9.2% of the total nitrogen was eliminated by the 2 nd TF. These results indicate that some of the dissolved sulfide was oxidized to elemental sulfur and/or thiosulfate; further, and sulfur-based autotrophic denitrification was observed to occur in the 2 nd TF. Therefore, this two-stage TF system can be employed as a low-cost desulfurization system to perform biogas purification and nitrogen elimination.