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Continuous sulfur biotransformation in an anaerobic-anoxic sequential batch reactor involving sulfate reduction and denitrifying sulfide oxidization

Yuan, Ye, Bian, Aiqin, Chen, Fan, Xu, Xijun, Huang, Cong, Chen, Chuan, Liu, Wenzong, Cheng, Haoyi, Chen, Tianming, Ding, Cheng, Li, Zhaoxia, Wang, Aijie
Chemosphere 2019 v.234 pp. 568-578
Desulfomicrobium, Desulfuromonas, Thermothrix, bacteria, biotransformation, denitrification, microbial communities, models, nitrates, oxidation, sludge, sulfates, sulfur, wastewater
The pathways and intermediates of continuous sulfur biotransformation in an anaerobic and anoxic sequential batch reactor (AA-SBR) involving sulfate reduction (SR) and denitrifying sulfide oxidization (DSO) were investigated. In the anoxic phase, DSO occurred in two sequential steps, the oxidation of sulfide (S2−) to elemental sulfur (S0) and the oxidation of S0 to sulfate (SO42−). The oxidation rate of S2− to S0 was 3.31 times faster than that of S0 to SO42−, resulting in the accumulation of S0 as a desired intermediate under S2−-S/NO3−-N ratio (molar ratio) of 0.9:1. Although, approximately 60% of generated S0 suspended in the effluent, about 40% of S0 retained in the sludge, which could be further oxidized or reduced in anoxic or anaerobic phase. In anoxic, S0 was subsequently oxidized to SO42− under S2−-S/NO3−-N ratio of 0.5:1. In anaerobic, S0 coexist with SO42− (in fresh wastewater) were simultaneously reduced to S2−, and the reduction rate of SO42− to S2− was 3.17 times faster than that of S0 to S2−, resulting in a higher production of S0 in subsequent anoxic phase. Microbial community analysis indicated that SO42−/S0-reducing bacteria (e.g. Desulfomicrobium and Desulfuromonas) and S2−/S0-oxidizing bacteria (e.g. Paracoccus and Thermothrix) co-participated in continuous sulfur biotransformation in the AA-SBR. A conceptual model was established to describe these main processes and key intermediates. The research offers a new insight into the reaction processes optimization for S0 recovery and simultaneous removal of SO42− and NO3− in an AA-SBR.