This study tests a hydrogen-based membrane biofilm reactor (MBfR) to investigate simultaneous bioreduction of selected oxidized contaminants, including nitrate (<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm01.gif"/>-N), sulfate (<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm15.gif"/>), bromate (<inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm26.gif"/>), chromate (Cr(VI)) and para-chloronitrobenzene (p-CNB). The experiments demonstrate that MBfR can achieve high performance for contaminants bioreduction to harmless or immobile forms in 240 days, with a maximum reduction fluxes of 0.901 g <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm37.gif"/>-N/m2·d, 1.573 g <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm48.gif"/>/m2·d, 0.009 g <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm59.gif"/>/m2·d, 0.022 g Cr(VI)/m2·d, and 0.043 g p-CNB/m2·d. Increasing H2 pressure and decreasing influent surface loading enhanced removal efficiency of the reactor. Flux analysis indicates that nitrate and sulfate reductions competed more strongly than <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="00178-ilm70.gif"/>, Cr(VI) and p-CNB reduction. The average H2 utilization rate, H2 flux, and H2 utilization efficiency of the reactor were 0.026 to 0.052 mg H2/cm3·d, 0.024 to 0.046 mg H2/cm2·d, and 97.5% to 99.3% (nearly 100%). Results show the hydrogen-based MBfR may be suitable for removing multiple oxidized contaminants in drinking water or groundwater.