Hydrogen production and ammonium recovery from urine by a Microbial Electrolysis Cell

We investigated the use of a Microbial Electrolysis Cell (MEC) for the ammonium removal, COD removal and hydrogen production from five times diluted urine. During operation with a batch cathode, a current density of 23.07 ± 1.15 A m−2 was achieved corresponding to a hydrogen production rate of 48.6 ± 7.47 m3 H2 m−3 MEC d−1, an ammonium removal rate of 173.4 ± 18.1 g N m−2 d−1 and a COD removal rate of 171.0 ± 16.9 g COD m−2 d−1. Ammonia stripping was not possible in the applied MEC and ammonia diffusion from cathode to anode compartment led to a relatively short stable operation period. The stable operation period was prolonged by addition of new cathode media (HRT 6 h), but this resulted in a lower current density (14.64 ± 1.65 A m−2), hydrogen production rate (32.0 ± 0.89 m3 H2 m−3 MEC d−1), ammonium removal rate (162.18 ± 10.37 g N m−2 d−1) and COD removal rate (130.56 ± 4.45 g COD m−2 d−1).