Selectivity control of nitrite and nitrate with the reaction of S0 and achieved nitrite accumulation in the sulfur autotrophic denitrification process

The characteristics of reaction between S0 and NO2--N or NO3--N in the sulfur autotrophic denitrification (SADN) process were studied using S0 as an electron donor and NO2--N and NO3--N as electron acceptors. The effect of changes in pH and temperature on the processes of NO2--N and NO3--N reduction were also studied to identify the optimum control parameters for strengthening the preference of S0 on NO3--N; thus, achieving the efficient accumulation of NO2--N. The results showed that the affinity of S0 for NO3--N was considerably higher than that for NO2--N. The optimum pH values for the reductions of NO2--N and NO3--N were 7.0 and 8.5, respectively, and both optimum temperatures were 35 °C. By controlling different pH, the NO3--N conversion efficiency reached 90%, at which time the accumulation of NO2--N was more than 95%. Microbial community analysis showed that Thiobacillus, Sulfurimonas, and Thioahalobacter were the main genera in the S0-SADN process.