Influence on Desulfurization Efficiency and Interactions of Fe/S and pH During H2S in situ Depression of High Solid Anaerobic Digestion

Abstract

To evaluate the influence of Fe/S ratio and pH on sulfide removal efficiency and interactions between Fe/S and pH, anaerobic hydrogen sulfide in situ depression tests and digested sludge liquor sulfide removal tests were carried out by using dewatering sludge from a wastewater treatment plant (WWTP). Results showed that the concentration of hydrogen sulfide in biogas from the thermal pretreatment following anaerobic digestion process could be reduced from 170.4×10-6 to 14.09×10-6 at Fe/S=7.75, which means the biogas desulfurization treatment is not required. Under the condition of pH 7.00-7.50 and Fe/S 1-11, pH is the main influencing factor for sulfide removal. Improving the pH of anaerobic digestion is beneficial in reducing the dosage of Fe(Ⅲ). An Fe/S ratio of 7.0 is the minimum to meet the biogas hydrogen sulfide emission standards during high solid sludge anaerobic digestion. The concentration of hydrogen sulfide was not up to standards if pH was below 7.30.