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System evaluation and microbial analysis of a sulfur cycle-based wastewater treatment process for Co-treatment of simple wet flue gas desulfurization wastes with freshwater sewage

Qian, Jin, Liu, Rulong, Wei, Li, Lu, Hui, Chen, Guang-Hao
Water research 2015 v.80 pp. 189-199
bacteria, bacterial communities, biological treatment, chemical oxygen demand, denitrification, energy, flue gas desulfurization, freshwater, methane, nitrates, nitrification, nitrites, nitrogen, pH, seawater, sewage, sludge, sulfates, sulfides, sulfur, thiosulfates, wastewater treatment, China
A sulfur cycle-based wastewater treatment process, namely the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated process (SANI® process) has been recently developed for organics and nitrogen removal with 90% sludge minimization and 35% energy reduction in the biological treatment of saline sewage from seawater toilet flushing practice in Hong Kong. In this study, sulfate- and sulfite-rich wastes from simple wet flue gas desulfurization (WFGD) were considered as a potential low-cost sulfur source to achieve beneficial co-treatment with non-saline (freshwater) sewage in continental areas, through a Mixed Denitrification (MD)–SANI process trialed with synthetic mixture of simple WFGD wastes and freshwater sewage. The system showed 80% COD removal efficiency (specific COD removal rate of 0.26 kg COD/kg VSS/d) at an optimal pH of 7.5 and complete denitrification through MD (specific nitrogen removal rate of 0.33 kg N/kg VSS/d). Among the electron donors in MD, organics and thiosulfate could induce a much higher denitrifying activity than sulfide in terms of both NO3− reduction and NO2− reduction, suggesting a much higher nitrogen removal rate in organics-, thiosulfate- and sulfide-based MD in MD–SANI compared to sulfide alone-based autotrophic denitrification in conventional SANI®. Diverse sulfate/sulfite-reducing bacteria (SRB) genera dominated in the bacterial community of sulfate/sulfite-reducing up-flow sludge bed (SRUSB) sludge without methane producing bacteria detected. Desulfomicrobium-like species possibly for sulfite reduction and Desulfobulbus-like species possibly for sulfate reduction are the two dominant groups with respective abundance of 24.03 and 14.91% in the SRB genera. Diverse denitrifying genera were identified in the bacterial community of anoxic up-flow sludge bed (AnUSB) sludge and the Thauera- and Thiobacillus-like species were the major taxa. These results well explained the successful operation of the lab-scale MD–SANI process.