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

The characteristics of reaction between S and NO-N or NO-N in the sulfur autotrophic denitrification (SADN) process were studied using S as an electron donor and NO-N and NO-N as electron acceptors. The effect of changes in pH and temperature on the processes of NO-N and NO-N reduction were also studied to identify the optimum control parameters for strengthening the preference of S on NO-N; thus, achieving the efficient accumulation of NO-N. The results showed that the affinity of S for NO-N was considerably higher than that for NO-N. The optimum pH values for the reductions of NO-N and NO-N were 7.0 and 8.5, respectively, and both optimum temperatures were 35 °C. By controlling different pH, the NO-N conversion efficiency reached 90%, at which time the accumulation of NO-N was more than 95%. Microbial community analysis showed that Thiobacillus, Sulfurimonas, and Thioahalobacter were the main genera in the S-SADN process.