Simultaneous reduction of perchlorate and nitrate in a combined heterotrophic-sulfur-autotrophic system: Secondary pollution control, pH balance and microbial community analysis

Abstract

A combined heterotrophic-sulfur-autotrophic system (CHSAS) was established to simultaneously reduce perchlorate and nitrate in water. In this system, the OH^- produced by the acetate heterotrophic part (H-part) could be neutralized with the H⁺ produced by the sulfur autotrophic part (S-part); thus, the pH of the final effluent could keep neutral. In addition, the S-part could further reduce the pollutants and residual carbon from the H-part to achieve a high performance. For 19.62 ± 0.30 mg/L ClO₄^- and 21.56 ± 0.83 mg/L NO₃^--N in the influent, the operating parameters were optimal at a hydraulic retention time (HRT) of 1.0 h and an acetate concentration of 70 mg/L. The removal efficiency of ClO₄^- and NO₃^- reached 95.43% and 99.23%, without secondary pollution caused by residual organic carbon. It was also revealed that sulfur (S⁰) disproportionation can be inhibited by shortening the HRT and reducing the acetate dosage. The dominant heterotrophic and autotrophic bacteria were Thauera and Ferritrophicum, respectively, while Chlorobaculum was related to S⁰ disproportionation.

Keywords: Combined heterotrophic-sulfur-autotrophic system (CHSAS); High-throughput sequencing; Nitrate; Perchlorate; Secondary pollution control; pH balance.