Ammonium recovery from residual aqueous streams

This report contains the main findings of studies carried out by different partners in the context of the TKI project: Valorization of Biomass (Biovalor). The studies were focused on evaluating and testing state-of-the-art technologies for ammonium (NH4+) removal and recovery from different streams: organic residual flows and industrial wastewater. These streams consisted of digester supernatants, i.e., the liquid fraction of digestates, with and without pretreatment, produced at Attero, Loonwerkersbedrijf, van Amstel, Groot Zevert, and Cosun Beet Company. One of the evaluated technologies was transmembrane chemisorption (TMCS), which is used for the recovery of NH4+ in the form of high-purity ammonium salts, e.g., (NH4)2SO4. During TMCS ammonia (NH3) is stripped from the feed stream and recovered in an acid solution as fertilizer. The complexity of the digestates’ matrix—the presence of organic compounds and dissolved salts, among other compounds—in which NH3 is dissolved greatly influences the recovery efficiency of the TMCS process. Therefore, often pretreatment processes are required to efficiently recover NH4+. The application of pressure and electrically driven technologies as pretreatment for TMCS were evaluated. Electrocoagulation was evaluated to improve the quality of digester supernatants by removing COD before membrane filtration processes. Additionally, microfiltration, high-pressure nanofiltration, conventional electrodialysis, and electrodialysis with bipolar membranes were evaluated for the removal of NH4+.