Electrochemical recovery of H 2 and nutrients (N, P) from synthetic source separate urine water

This study examined an electrochemical method of H production and nutrient recovery from synthetic source separated urine (SSU). The efficacy of H production was examined through hydrogen recovery experiments (HRE) using Ni foam electrodes. Similarly, nutrient (N and P) recovery was also examined in post-nutrient recovery experiments (NRE) with sacrificial Mg electrodes. To achieve higher nutrient recovery in the post-nutrient recovery process, the most important operating parameters (initial solution pH (pH ) and current density) were optimized. Optimization of NRE revealed that > 90% NH -N and PO -P could be recovered at 8 mA cm with a pH of 6-8. Notable NH -N and PO -P reduction were observed at an equimolar Mg dissolution ratio (1:1) of Mg :NH and a 1.1:1 ratio of Mg :PO respectively. However, poor total Kjeldahl nitrogen (TKN) reduction was observed. Thus, we anticipate that direct electrochemical conversion of urea to N at the anode followed by H generation at the cathode is a more sustainable way to reduce TKN. Batch HRE showed that the initial TKN, 1094 mg L (934 mg L from urea-N and 160 mg L from NH Cl), was significantly reduced to 360 mg L by Ni-Ni electrolysis, whereas around 53.8 g H gas was received from this Ni-Ni electrolysis system with a flow rate of 5-5.8 g mol day . Overall, this work produced a 68% reduction in TKN due to electrochemical conversion of urea into H .