A novel electrochemical stirred-tank reactor for wastewater nutrient upcycling with efficient struvite recovery and economic viability

The imminent depletion of global phosphorus reserves underscores the urgency of nutrient recovery from phosphorus-rich wastewater such as urine. Magnesium–air fuel cell (MAFC) has recently emerged as a promising technology for simultaneous phosphorus recovery and electricity generation. However, conventional planar MAFC configurations are hindered by limited phosphorus treatment capacity and low Mg 2+ utilization efficiency. Here, we developed an electrochemical stirred-tank reactor (ESTR) integrated with an MAFC to enhance resource recovery from urine. Computational and experimental analyses demonstrated improved mass transfer within the ESTR, leading to over 99.91% removal of PO 4 3- -P within 50 min and achieving a high phosphorus treatment load of 20.22 kg/(m 3 ·d). By precisely regulating the corrosion pathways of magnesium anode, the hydrogen evolution corrosion was effectively inhibited by 20.55%. As a result, the Mg 2+ utilization efficiency reached 88.81%, approximately 30.20% higher than that of conventional MAFC systems. During 3600-min continuous operation, the system maintained an average PO 4 3- -P removal of 99.83 ± 0.13%, with struvite content in the recovered precipitates reaching 97.25%, demonstrating excellent operational stability. An economic evaluation further indicated a net profit of 21.43 RMB per cubic meter of urine treated, highlighting both environmental and economic viability. This work presents a scalable and efficient strategy for phosphorus recovery from wastewater and advances the practical implementation of MAFC-based technologies in sustainable resource recycling.