Effect of SO-S addition on Anammox coupling sulfur autotrophic denitrification and mechanism analysis using N and O dual isotope effects.

Anaerobic ammonia oxidation (Anammox) coupling sulfur autotrophic denitrification is an effective method for the advanced nitrogen removal from the wastewater with limited carbon source. The influence of SO-S addition on Anammox coupling sulfur autotrophic denitrification was investigated by adding different concentrations of SO-S (0, 39, 78, 156 and 312 mg/L) to the Anammox system. The contribution of sulfur autotrophic denitrification and Anammox to nitrogen removal at SO-S concentrations of 156 mg/L was 75% ∼83% and 17%∼25%, respectively, and the mixed system achieved completely nitrogen removal. However, Anammox bioactivity was completely inhibited at SO-S concentrations up to 312 mg/L, and only sulfur autotrophic denitrification occurred. The isotopic effects of NO-N (δN and δO) and NO-N (δN and δO) during Anammox coupling sulfur autotrophic denitrification showed a gradual decrease trend with the increase of SO-S addition. The ratios of δN:δO and δN:δO was maintained at 1.30-2.41 and 1.36-2.52, respectively, which revealed that Anammox was dominant nitrogen removal pathway at SO-S concentrations less than 156 mg/L. Microbial diversity gradually decreased with the increase of SO-S. The SO-S addition enhanced the SO-driven autotrophic denitrification and weakened the Anammox, leading to a gradually decreasing trend of the proportion of Candidatus Brocadia as Anammox bacteria from the initial 27% to 4% (SO-S of 156 mg/L). Yet Norank-f-Hydrogenophilaceae (more than 50%) and Thiobacillus (54%) as functional bacteria of autotrophic denitrification obviously increased. The appropriate amount of SO-S addition promoted the performance of Anammox coupling sulfur autotrophic denitrification achieved completely nitrogen removal.