Simultaneous removal of perchlorate and nitrate in a combined reactor of sulfur autotrophy and electrochemical hydrogen autotrophy

Abstract The removal of perchlorate (ClO 4 − ) and nitrate (NO 3 − ) from drinking water was investigated in a combined reactor of sulfur autotrophy (S-compartment) and electrochemical hydrogen autotrophy (H-compartment). The removal efficiencies of NO 3 − and ClO 4 − in the S-compartment and H-compartment were affected by hydraulic retention time (HRT) and current intensity, respectively. The sulfur- and hydrogen-autotrophic denitrifying process favored over the process of sulfur- and hydrogen-autotrophic perchlorate reduction in the combined reactor. The longer HRT could lead to sulfur (S 0 ) disproportionation due to the increase of the contact time between water and S 0 particle. The H + generated from S-compartment could be reduced as H 2 by electrochemical process in H-compartment, and the generated H 2 as an electron donor was utilized to reduce NO 3 − and ClO 4 − by hydrogen autotrophic reduction. The oxidation reduction potential (ORP) in the effluent from S-compartment and H-compartment were below −180 mV, suggesting good anaerobic conditions for the reduction of NO 3 − and ClO 4 − in the combined reactor. Some sulfur- and hydrogen-autotrophic denitrifying bacteria could use both NO 3 − and ClO 4 − as electron acceptors in the combined reactor. The DGGR profile illustrated that some variations were found in the microbial community at different locations of the combined reactor.