Different fates of the coexisting Sb(V) and nitrate in sulfur autotrophic bioreactor mediated by internal circulation: Performance and mechanism

Abstract

The sulfur autotrophic bioreactor with internal circulation was established for the simultaneous and effective removal of antimonate (Sb(V)) and nitrate (NO3−) in water for the first time. At the hydraulic retention time (HRT) of 8 h and the recycle ratio (R) of 5, the removal efficiency of Sb(V) and TSb reached up to 98.14 % and 96.89 % with a concentration of 10 mg/L Sb(V) in the influent. Although the shortening of HRT and the increase of R inhibited the removal of Sb(V) and TSb, there was little effect on the NO3− removal (> 97.08 % with the influent of 20 mg-N/L). Meanwhile, the measured concentration of sulfate (SO42−) and alkalinity consumption in effluent were both greater than theoretical value, indicating the occurrence of S0 disproportionation in bioreactor. The shortened HRT and declined R reduced alkalinity consumption, which hindered S0 disproportionation. The precipitates were collected at end of bioreactor operation period, which was confirmed to be Sb2S3 by SEM-EDS, Raman, XRD and XPS analysis. High-throughput sequencing results indicated that Proteobacteria and Bacteroidetes were the dominant bacteria at phylum level for denitrification. Besides, Sulfuriferula, Thiovirga and Sulfuricurvum (at genus level) might be accountable for bio-reduction of NO3− and Sb(V), as well as S0 disproportionation.