A fixed film bioreactor for the denitrification of the effluent from an anaerobic membrane bioreactor (AnMBR) treating domestic wastewater was designed, built and investigated. After anaerobic treatment, the wastewater usually has a low C/N ratio (similar to 1.3), and a remaining chemical oxygen demand of around 117 mg O-2/L, which is not enough to make conventional heterotrophic denitrification possible. That effluent also holds methane and sulfide dissolved and oversaturated after leaving the AnMBR. This paper demonstrates the feasibility of using these reduced compounds as electron donors in order to remove 80 mg NOx-N/L at 18 degrees C and 2 h of hydraulic retention time. In addition, the influence of the NO2/NO3 ratios in the feed was studied. Total nitrogen removal was achieved in all the cases studied, except for a feed with 100% NO3. Methane was the main electron donor used to remove the nitrites and nitrates, with a participation rate of over 70%. (C) 2017 Elsevier Ltd. All rights reserved.