Operational parameters in H2S biofiltration under extreme acid conditions: performance, biomass control, and CO2 consumption.

This paper reports the treatment of gaseous hydrogen sulfide, H2S, in a biotrickling filter (BTF) under extreme acidic pH conditions (≈ 1.2). The effect of adding thiosulfate (Na2S2O3.5H2O) to promote biomass growth, feeding low concentrations of ozone to control excess biomass, and the carbon dioxide, CO2, consumption by the chemolithoautotrophic consortium were evaluated. The results showed a global removal efficiency over 98.0% with loads of H2S > 50 g m-3 h-1 (at 639 ppmv) and a linear relation between H2S elimination capacity with the CO2 consumption rate of around 0.1 gCO2/gH2S. Supplementing sulfur in the medium with 2 g L-1 thiosulfate resulted in negative effect performance. Respirometry tests proved that the consortium could not utilize this sulfur form at this pH. Additionally, continuous and intermittent O3 feeding to the BTF in gaseous concentrations of 98 ± 5.4 mg m-3 caused a slight decreased in the performance but the biomass activity in the BTF was only slightly affected allowing a quick performance recovery once O3 addition was suspended.