Electrifying biotrickling filters for the treatment of aquaponics wastewater

•Non-conductive filling material brought insufficient and uncontrollable N removal.•Polarized conductive filling material provided limited but controllable N removal.•Mix of non-conductive and polarized conductive material were the most active.•The electrified biotrickling filter met the N standards, closing aquaponics loop. This work aimed to study the electrification of biotrickling filters by means of Microbial electrochemical technologies (MET) to develop an easy-to-assemble and easy-to-use MET for nitrogen removal without external aeration nor addition of chemicals. Four different designs were tested. The highest ammonium and nitrate removal rates (94 gN·m−3·d−1 and 43 gN·m−3·d−1, respectively) were reached by combining an aerobic zone with an electrified anoxic zone. The standards of effluent quality suitable for hydroponics were met at low energy cost (8.3 × 10−2 kWh·gN−1). Electrified biotrickling filters are a promising alternative for aquaponics and a potential treatment for organic carbon-deficient ammonium-contaminated waters.