Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms

Removal of hydrogen sulfide (H2S) from biogas was investigated in a biochar column integrated with a bench-scale continuous-stirred tank reactor (CSTR) treating sulfate-laden wastewater. Synthetic wastewater containing sulfate concentrations of 200-2000 mg SO42-/L was used as substrate, and the CSTR was operated at an organic loading rate of 1.5 g chemical oxygen demand (COD)/L.day and a hydraulic retention time (HRT) of 20 days. The biochar was able to remove about 98.0 (+/- 1.2)% of H2S for the ranges of concentrations from 105-1020 ppmv, especially at high moisture content (80-85%). Very high H2S adsorption capacity (up to 273.2 +/- 1.9 mg H2S/g) of biochar is expected to enhance the H2S oxidation into S-0 and sulfate. These findings bring a potentially novel application of sulfur-rich biochar as a source of sulfur, an essential but often deficient micro-nutrient in soils. (C) 2017 Elsevier Ltd. All rights reserved.