Concentrating nitrogen waste with electrodialysis for fertilizer production

Recovery of nitrogen from wastewater presents a unique opportunity to valorize waste and contribute to a more circular nitrogen economy. However, dilute solution separations are challenging for most state-of-the-art separations technologies. This often results in technologies having low concentration factors that result in low-value products (e. g. < 1 wt\% N). Here, we demonstrate how a cascading electrodialysis system combined with a hollow fiber membrane contactor (ED+HFMC) system can achieve efficient recovery of ammonia from simulated centralized animal feeding operations (CAFO) wastewater. The integrated system achieved an overall concentration factor of ~200x (~ 40 x in ED and a further ~5x in HFMC) and produced a ~10 wt\% NH4-N fertilizer product. The specific energy consumption (SEC) for the three stages of the ED was 1. 89--6. 14 kWh/kg NH4-N, which is significantly lower than the Haber--Bosch process (8. 9--19. 3 kWh/kg N). Operating costs were calculated to be <50 ¢/ kg NH4+-N for each of the ED stages and NH₃ stripping. This integrated ED+HFMC system holds promise for the recovery of ammonia from wastewater as it achieves high concentration factors and has low energy demand.