Influence of Sulfur Compounds on Biogas Production from Forest Industry Wastewater

Abstract

Various inorganic sulfur compounds and lignosulfonate were studied with respect to their effect on biogas production from synthetic wastewater simulating sulfite evaporator condensate. The sulfur balance during the anaerobic degradation was also investigated. In biogas production assay tests municipal digester sludge was used as seed material. Differences in sulfur inhibition of methanogenesis between various oxidation states of inorganic sulfur were detected. Sulfate and sulfide in concentrations 100 mg S/l had no effect whereas sulfite, thiosulfate and dithionite caused a lag-period in biogas production. Reduced biogas production was observed even with the addition of 1000 mg S/l as SO=4, SO=3 and S2O=3. Dithionite was the most toxic compound investigated. Sodiumlignosulfonate in concentrations 5-15 g/l has a supplementary increase in biogas production. Inorganic sulfur compounds were partially reduced to sulfide in anaerobic conditions.