Ammonia removal and recovery from anaerobic digestate of livestock wastewater using a pilot-scale bipolar membrane electrodialysis with a membrane contactor

Abstract

Despite the application of ammonia stripping and struvite methods to treat ammonia contained in livestock wastewater, they remain costly, with high energy consumption and subsequent biological treatment problems. Therefore, this study aimed to apply the principles of bipolar membrane electrodialysis (BMED) and gas permeable membranes to remove and simultaneously recover ammonia from the anaerobic digestate of livestock wastewater containing a high concentration of ammonia (>5000？mg /L). Ammonium ions were converted into free ammonia by adjusting the pH based on the principle of water dissociation in a bipolar membrane (BPM) without injecting separate chemicals. Additionally, a system was constructed to recover ammonium ions by connecting them to a membrane contactor. In lab-scale BMED performance testing, a two-compartment BPM-AEM combination achieved an ammonia removal rate >？80？%, with >？90？% of the removed ammonia recovered from the MC module. Based on these results, the pilot-scale BMED-MC system was designed with the BPM-AEM configuration. At the pilot scale, the ammonia removal rate was 94？% and the recovery rate was 82？% in the high-concentration anaerobic digestion solution, and the energy consumption under optimal operating conditions was 5.67 kWh/kgN, achieving both high removal and recovery rates. This system can help reduce environmental pollution caused by high-concentration ammonia-containing wastewater and contribute to enhancing the sustainability of wastewater treatment through ammonia recovery.