A novel pressurized hydrogenotrophic reactor operating at high rates was recently developed specifically for the removal of nitrate (NO3) 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 H2 loss occurs only through the effluent, resulting in H-2 utilization efficiency above 90%. In this research, a new treatment scheme to remove NO3 and perchlorate (ClO4)combining the pressurized reactor with a following open-to-atmosphere polishing unit is presented. In the pressurized reactor, NO3 and ClO4 are simultaneously removed. In the polishing unit, the residual dissolved H-2 from the pressurized reactor serves to further reduce ClO4 to trace concentrations below recommended levels. First, ClO4 reduction together with denitrification was demonstrated in the pressurized reactor without special inoculation and a maximal ClO4 volumetric removal rate of 1.83 g/(L-reactor d) was achieved. Microbial population analyses before and after the addition of ClO4 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 ClO4 concentration down to a minimal value of 2 mu g/L with a simultaneous increase of the H-2 utilization efficiency from 95% up to almost 100%. (c) 2017 Elsevier B.V. All rights reserved.