Transformations, Inhibition and Inhibition Control Methods of Sulfur in Sludge Anaerobic Digestion: A Review

Sulfur compounds play a significant role in low treatment efficiency, production of corrosive gases and unpleasant odors during sludge anaerobic digestion, which limits its environment and economic benefits. Better understanding of sulfur transformations, inhibitions and inhibition control methods is deemed necessary for enhancing the wider application of sludge anaerobic digestion. This review presented a detailed summary of research on the pathways and properties of sulfur transformations (dissimilation, assimilation and desulfurization), sulfur inhibitors (e.g. sulfide and sulfate reducing bacteria) and their inhibition mechanisms in sludge anaerobic digestion. The effects and mechanisms of various physical (e.g. thermal and ultrasound pretreatments), chemical (e.g. oxidative pretreatments and adding metal salts) and biological control methods (microaerobic desulfuration) on sulfur inhibition were also evaluated in sludge anaerobic digestion. Besides, a proper method was proposed to control sulfur inhibition in sludge anaerobic digestion according to existing studies.