The anaerobic digestion of cow manure produces a biogas containing hydrogen sulphide. We tested the removal of hydrogen sulphide from biogas by comparing the efficiency of oxygen and air as electron acceptors of oxidant actives. Research was performed in four 30L digester tanks under mesophilic conditions (37±0.2!) with a hydraulic retention time of 20 days. The concentration of hydrogen sulphide was successfully reduced from 8570 mg/Nm3 to less than 500 mg/Nm3 by both oxygen (flow rates of 0.5, 0.25 and 0.13 ml/min) and air (flow rates of 2.5, 1.25 and 0.63 ml/min). The removal efficiency of microaerobic supplied by oxygen and air is more than 96.0% and COD removal, VS reduction and methane productivity are not affected under microaerobic conditions. Biogas productivity increased by 27-30 mL/gVS fed and methane concentration decreased by 4-6 (v/v) % when air was added to the digester tank, as a result of nitrogen dilution. Sulphate, thiosulphate and elemental sulphur were found to be the main products of microaerobic digestive processes according O2: Sin. By decreasing the supply ratio of O2 to S we were able to decrease selectivity of sulphate, decrease thiosulphate formation, decrease the elemental sulphur in sludge and increase missing sulphur.
Biogas, Biological desulfurization, Hydrogen sulphur removal, Microaerobic, sulphur balance
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