Ammonia recovery from urine in a scaled-up Microbial Electrolysis Cell

A two-step treatment system for nutrient and energy recovery from urine was successfully operated for six months. In the first step, phosphorus (P) was recovered as struvite (magnesium ammonium phosphate or MAP) in a MAP reactor. The effluent of this MAP reactor was used for total ammonia-nitrogen (TAN) recovery and hydrogen production in a Microbial Electrolysis Cell (MEC). This MEC was coupled to a Transmembranechemisorption (TMCS) module, in which the TAN was recovered as an ammonium sulphate solution. The MEC had a projected surface area of 0.5 m(2) and was operated at different urine dilutions. The system was stable during the operation on 2 times diluted and undiluted urine at an applied voltage of 0.5 V with an average current density of 1.7 +/- 0.2 A m(-2). During stable current production, the TAN transport efficiency over the CEM was 92 +/- 25% and the TAN recovery was 31 +/- 59%. In terms of energy efficiency, the electrical energy required for the TAN recovery was 4.9 +/- 1.0 MJ kg(N)(-1), which is lower than competing electrochemical nitrogen removal/recovery technologies. Overall, this study shows, for the first time, the application of a scaled-up MEC for nutrient recovery from urine. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.