Effects of different reduced sulfur forms as electron donors in the start-up process of short-cut sulfur autotrophic denitrification

In this study, two short-cut sulfur autotrophic denitrification (SSADN) reactors were initiated using different reduced sulfur forms as electron donors and their effects on the start-up speed of the SSADN process, NO2--N accumulation characteristics, and microbial community were investigated. Results revealed that during the same period, due to the relatively slow S0 dissolution rate, the NO2--N production rate realized by microorganisms in S0-SSADN (NO2--N production rate (NPR), 174 mg/(L·d)) was significantly slower than S2--SSADN (NPR, 679 mg/(L·d)). The NO2--N accumulation efficiency (NAE) was maintained > 80%, which was significantly higher than S2--SSADN. In the SSADN system using different reduced sulfur forms, the microbial community structure and abundance considerably differed. The main sulfur-oxidizing bacteria (SOB) in S0-SSADN were Sulfurimonas (6.5%) and Thiobacillus (5.3%). The main SOB species in S2--SSADN was Thiomonas (13.6%). Thermomonas played an important role in the two reactors as an important NO3--N denitrifying bacteria species.