Isolation of sulfide oxidisers for desulfurising biogas produced from anaerobic piggery wastewater treatment in Taiwan.

This study aimed to improve the utilisation of biogas in pig farms, the promotion of biogas use and the reduction of greenhouse gas (i.e. methane, carbon dioxide, and nitrous oxide) emissions to the atmosphere. Sulfur oxidisers can convert sulfide (S2–) to sulfur (S0) and even sulfate (SO42–). Strains of CYAS-1, CYAS-2, SW-1, SW-2, and SW-3 were isolated from environmental samples and proven to have capabilities of sulfide oxidation by growing them in 150 mL liquid media with 1.5 g sulfur powder. An increase in sulfate concentration was used to select sulfide oxidisers. Strains CYAS-1 and CYAS-2, which both had significant sulfide oxidation capability, were isolated from the sludge of piggery wastewater treatment facilities. Moreover, strains SW-1, SW-2, and SW-3 were isolated from a pilot-scale biogas bio-filter (BBF) reactor. The experimental results showed that strain CYAS-1 (identified as Acinetobacter spp.), grown in diluted trypticase soy broth (TSB) with sulfur powder, increased the concentrations of SO42– from 17.2 ± 0.5 to 23.8 ± 1.0 mg/L (38.4% increase). Strain CYAS-2 (identified as Corynebacterium spp.), grown in diluted TSB with sulfur powder, increased concentrations of SO42– from 17.7 ± 0.1 to 25.9 ± 0.9 mg/L (47.0% increase). Concentrations of SO42– were increased 40.5, 33.6, and 29.7% in the presence of strains SW-1 (Candida kruse/inconspicua; 96.2% identity), SW-2 (Candida parapsilosis; 93.2% identity), and SW-3 (Trichosporon mucoides; 95.7% identity), respectively.