Insights into potassium permanganate reducing H2S generation from anaerobic fermentation of sludge

Potassium permanganate, a versatile strong oxidant, has been applied as a highly effective additive to degrade pollutants and recover resources from Waste activated sludge (WAS). In addition to these benefits, it was observed in this study that KMnO4 largely reduced H2S production from WAS anaerobic fermentation. With an increase of KMnO4 dosage from 0 to 0.1 g/g TSS, the maximal H2S production reduced from 292.3 x 104 to 96.4 x 104 mg/g VSS while the maximal short-chain fatty acids production increased from 23 to 251 mg COD/g VSS. Model-based analysis showed that KMnO4 decreased the maximal H2S yield potential and H2S production rate. The mechanism explorations revealed that several oxidative substances (e.g., center dot O2 and center dot OH), Mn2+, and OH were substantially generated after KMnO4 being added into the fermenters. The generated oxidative substances resulted in intracellular substance release even cell apoptosis. This inhibited the activities of two main S2 (H2S precursor) producers, i.e., Sulfate reducing bacteria (SRBs) and anaerobes responsible for hydrolysis of sulfur-containing organics, especially that of SRBs. Experimental results showed that 0.1 g/g TSS KMnO4 inhibited sulfur-containing organics hydrolysis, amino acids degradation, and sulfate reducing process by 12.5%, 27.2%, and 61.2%, respectively. The Mn2+ released from KMnO4 and other metal ions (e.g., Fe2+) originated from metal-binding functional groups owing to KMnO4 addition caused substantial S-based precipitations, which also decreased S2 in the fermentation liquor. Besides, the generated OH increased fermentation pH, which benefited the chemical equilibrium of sulfide species from H2S to HS and S2. Microbial community and PICRUSt2 analyses further revealed that KMnO4 significantly decreased the abundances of S2 producers and functional genes responsible for sulfate reducing process.