Perchlorate removal from water by pyrite-autotrophic and acetate-heterotrophic reduction process

In this paper， a combination of pyrite autotrophic and sodium acetate-based heterotrophic reduction process was used for removing perchlorate from water， and the removal performance was investigated in a pyrite-packed reactor. Results showed that perchlorate ［Cl（Ⅶ）］ was effectively reduced into chloride ions （Cl-） using pyrite and acetate as electron donors. In the early stage of reactor operation （from day 0 to day 15）， the perchlorate removal efficiency was over 85%； as the temperature decreased， the removal efficiency decreased and ultimately stabilized at 60% above. As the temperature increased and the hydraulic retention time increased， the removal performance improved， and the final removal efficiency of perchlorate stabilized at over 95%. Pyrite-based autotrophic reduction was dominant （from 0 to day 35） first， while acetate-based heterotrophic reduction was dominant in the later stage for perchlorate removal. Kinetic analysis indicated that the degradation process of perchlorate followed a zero-order kinetic model， and the perchlorate removal rate was 0.48 mg/（L·h） to 0.70 mg/（L·h）. The characterization of pyrite by X-ray photoelectron spectroscopy （XPS） technology showed that S2- and Fe（Ⅱ） in the pyrite were oxidized into SO42- and Fe（Ⅲ）， respectively. The dominant bacterial genera for the removal of perchlorate in the reactor were Romboutsia， Ferruginibacter， and Dokdonellai. This study provides a potential approach for the remediation of perchlorate-contaminated wastewater.