Abstract

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 S2O32−-S addition on Anammox coupling sulfur autotrophic denitrification was investigated by adding different concentrations of S2O32−-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 S2O32−-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 S2O32−-S concentrations up to 312 mg/L, and only sulfur autotrophic denitrification occurred. The isotopic effects of NO2−-N (δ15NNO2 and δ18ONO2) and NO3−-N (δ15NNO3 and δ18ONO3) during Anammox coupling sulfur autotrophic denitrification showed a gradual decrease trend with the increase of S2O32−-S addition. The ratios of δ15NNO2:δ18ONO2 and δ15NNO3:δ18ONO3 was maintained at 1.30–2.41 and 1.36–2.52, respectively, which revealed that Anammox was dominant nitrogen removal pathway at S2O32−-S concentrations less than 156 mg/L. Microbial diversity gradually decreased with the increase of S2O32−-S. The S2O32−-S addition enhanced the S2O32−-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% (S2O32−-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 S2O32−-S addition promoted the performance of Anammox coupling sulfur autotrophic denitrification achieved completely nitrogen removal.

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