Extremely acidic condition (pH<1.0) as a novel strategy to achieve high-efficient hydrogen sulfide removal in biotrickling filter: Biomass accumulation, sulfur oxidation pathway and microbial analysis

Extremely acidic conditions (pH < 1.0) during hydrogen sulfide (H2S) biotreatment significantly reduce the cost of pH regulation; however, there remain challenges to its applications. The present study investigated the H2S removal and biomass variations in biotrickling filter (BTF) under long-term highly acidic conditions. A BTF operated for 144 days at pH 0.5-1.0 achieved an H2S elimination capacity (EC) of 109.9 g/(m(3).h) (removal efficiency = 97.0%) at an empty bed retention time of 20 s, with an average biomass concentration at 20.6 g/LBTF. The biomass concentration at neutral pH increased from 22.3 to 49.5 g/L-BTF within 28 days. In this case, elemental sulfur (S-0) accumulated due to insufficient oxygen transfer in biofilm, which aggravated the BTF blockage problem. After long-term domestication under extremely acidic conditions, a mixotrophic acidophilic sulfur-oxidizing bacteria (SOB) Alicyclobacillus (abundance 55.4%) were enriched in the extremely acidic biofilm, while non-aciduric bacteria were eliminated, which maintained the balance of biofilm thickness. Biofilm with optimum thickness ensured oxygen transfer and H2S oxidation, avoiding the accumulation of S-0. The BTF performance improved due to the enrichment of active mixotrophic SOB with high abundance under extremely acidic conditions. The mixotrophic SOB is expected to be further enriched under extremely acidic conditions by adding carbohydrates to enhance H2S removal.

Automated summary

This study investigated H2S removal and biomass variations in a biotrickling filter (BTF) under highly acidic conditions. The results showed that the BTF achieved efficient H2S removal at pH 0.5-1.0, and the enrichment of acidophilic sulfur-oxidizing bacteria (SOB) in the acidic biofilm maintained the balance of the biofilm thickness, ensuring oxygen transfer and H2S oxidation.