Co-reduction of nitrate and perchlorate in a pressurized hydrogenotrophic reactor with complete H-2 utilization

Abstract A novel pressurized hydrogenotrophic reactor operating at high rates was recently developed specifically for the removal of nitrate (NO 3 − ) from drinking water. The reactor is characterized by safe and economical operation since hydrogen (H 2 ) purging intrinsic to conventional H 2 -based denitrifying systems is not required and H 2 loss occurs only through the effluent, resulting in H 2 utilization efficiency above 90%. In this research, a new treatment scheme to remove NO 3 − and perchlorate (ClO 4 − ) combining the pressurized reactor with a following open-to-atmosphere polishing unit is presented. In the pressurized reactor, NO 3 − and ClO 4 − are simultaneously removed. In the polishing unit, the residual dissolved H 2 from the pressurized reactor serves to further reduce ClO 4 − to trace concentrations below recommended levels. First, ClO 4 − reduction together with denitrification was demonstrated in the pressurized reactor without special inoculation and a maximal ClO 4 − volumetric removal rate of 1.83 g/(L reactor ·d) was achieved. Microbial population analyses before and after the addition of ClO 4 − were similar with a large fraction of the genus Dechloromonas . Results show that the combined treatment scheme consisting of the pressurized reactor and the polishing unit allowed for the reduction of ClO 4 − concentration down to a minimal value of 2 µg/L with a simultaneous increase of the H 2 utilization efficiency from 95% up to almost 100%.