The effects of thiosulfinates on methane production from anaerobic co-digestion of waste activated sludge and food waste and mitigate method

[Display omitted] •Thiosulfinate reduced methane yield from anaerobic co-digestion of WAS and FW.•Thiosulfinate inactivate functional coenzyme for methane production.•Thiosulfinate damaged the cell membrane structure of anaerobic microbes.•Thiosulfinate induced fermentation cell apoptosis.•Pretreatment could mitigate the inhibition of thiosulfiante on methane production. Thiosulfinates, a natural antibiotic, existed in all parts of Allium, therefore might be accumulated in large amounts in food waste (FW). FW was often added into waste activated sludge (WAS) anaerobic digestion process as a kind of supplement for nutrition balance. However, the impact of thiosulfinates on methane production and the possible approach to mitigate its inhibition on the co-digestion process could be available in few literatures. This work was carried out in a series of batch experiment at pH 7.0 ± 0.2 and 35 ± 1.0 ℃ to promote the further understanding of this process. The experimental results showed that the methane accumulation decreased from 270.6 ± 13.4 to 16.7 ± 7.0 mL/g VSS (volatile suspended solids) when the initial concentration of thiosulfinates increased from 0 to 2.5 μg/g VSS. The activities of functional enzymes (F420 and CoM) were inhibited by 99.06% and 99.82% compared with control group when reactor contained 2.5 μg/g VSS thiosulfinates. Furthermore, different temperature, pH, and combination pretreat were applied to impair the inhibition of thiosulfinate. Compared with no pretreatment group, methane yield was increased by 2.26, 32.18 and 42.2-fold, respectively which group was under pretreatment method of heat (100 ℃), alkali (pH 9) and combination.