Concentrating Nitrogen Waste with Electrodialysis for Fertilizer Production.

Abstract

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 operation (CAFO) wastewater. The integrated system achieved an overall concentration factor of ∼200× (∼40× in ED and ∼5× in HFMC). This resulted in 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 lower than that of the Haber-Bosch process (8.9-19.3 kWh/kg N). Operating costs were <$0.90/kg NH₄ ⁺-N for each of the electrodialysis stages and NH₃ stripping. This integrated ED+HFMC system holds promise for the recovery of ammonia from dilute feedstreams as the ED+HFMC achieves high concentration factors and has low energy demand.