Comparative analysis of sulfur-driven autotrophic denitrification for pilot-scale application: Pollutant removal...

Two parallel pilot-scale reactors were operated to investigate pollutant removal performance and metabolic pathways in elemental sulfur-driven autotrophic denitrification (SDAD) process under low temperature and after addition of external electron donors. The results showed that low temperature slightly inhibited SDAD (average total nitrogen removal of ∼4.7 mg L^-1) while supplement of sodium thiosulfate (stage 2) and sodium acetate (stage 3) enhanced denitrification and secretion of extracellular polymeric substances (EPS), leading to the average removal rate of 0.75 and 1.01 kg N m^-3 d^-1, respectively with over twice higher total EPS. Correspondingly, nitrogen and sulfur related microbial metabolisms especially nitrite reductase and nitric oxide reductase encoding were promoted by genera including Thermomonas and Thiobacillus. The variations revealed that extra sodium acetate improved denitrification and enriched more SDAD-related microorganisms compared with sodium thiosulfate, which potentially catalyzed the refinement of practical strategies for optimizing denitrification in low carbon to nitrogen ratio wastewater treatment.