Volatile Sulfur Compounds Removal In Biogas Using Thermo-Oxidative Pretreatment

Biological treatment of municipal wastewater produces large amount of Sludge. Although anaerobic (AD) digestion is a widely accepted and popular sludge stabilization process, conventional anaerobic digestion has some limitations. Anaerobic digestibility of municipal waste activated sludge (WAS) is very poor compared to primary sludge due to the rate-limiting hydrolysis step. Presence of volatile sulfur compounds (VSCs) such as hydrogen sulfide (H₂S), mercaptans in biogas is another major concern, because they may contribute to corrosion in combustion engines and create unpleasant environment in wastewater treatment plants. Pretreatment of sludge prior to AD is a common approach to increase the solid reduction and biogas production in anaerobic digestion. This study investigated the impact of thermo-oxidative pretreatment on VSCs removal during anaerobic digestion. Thermo-oxidative pretreatment of municipal waste activated sludge was conducted using thermal pretreatment in presence of H₂O₂ and FeCl₂ as oxidants with an objective to sludge disintegration for enhancing anaerobic digestion as well as to remove volatile sulfur compounds generation potential in biogas. For pretreated feed digester, the hydrogen sulfide (H₂S) and dimethyl sulfide (DMS) concentrations in biogas significantly decreased by average 75%, and 40%, respectively; while methanethiol (MT) removal efficiency was statistically insignificant compared to control digester. Compared to the control, overall total suspended solids (TSS) and volatile suspended solids (VSS) removal efficiency were 10% and 11% higher for pretreated digester operated at 10 days solid residence time (SRT), and methane production rate increased by ~20%.