The removal of hydrogen sulphide by ferrihydrite during anaerobic digestion of sewage sludge

The potential of ferrihydrite (HFO) for in-situ removal of hydrogen sulphide during sewage sludge anaerobic digestion was evaluated. Within 20days, the average hydrogen sulphide concentration in biogas was successfully decreased from 219.9 (or 3263 of sulphate-rich sludge) mg/m³ to 74.61(1537), 12.84(229) and 1.06(3.3) mg/m³ in the presence of 0.05%, 0.10% and 0.25% (wt) HFO, respectively. The bioavailable fraction of the total P was decreased from 70.1% to 41.7%, 20.5% and 6.9%. The analysis of XRD and phosphorus fractionation profile confirmed the immobilization of bioavailable-P mainly as Fe₃(PO₄)₂ in HFO-dosed sludge. According to the data of volatile matters (VM), sludge stabilization might be prolonged in the presence of HFO due to soluble phosphorus limitation partly. The reduced inorganic sulphur (RIS) fractionation profile further indicated that FeS₂ and S⁰ are the main reaction products of sulphide and HFO.