Transmembrane chemical absorption technology for ammonia recovery from wastewater: A critical review

Technologies for resource recovery from wastewater have drawn the world's attention. Recovering nitrogen contained in wastewater offers an opportunity to produce alternative fertilizers for agriculture instead of conventional treatment. Transmembrane chemical absorption is a promising process based on hydrophobic membrane contactors to recover ammonia from wastewater to produce an ammonium-based product. This review critically explores the process principle, modelling approaches, membrane materials and system configurations, mass transfer characterization, elucidation of the undesired phenomenon of water vapour transport and a particular focus on influencing operating conditions. Ammonia could be recovered from a wide range of waste, including digestate, urine, manure or industrial effluents. The pretreatment of the wastewater, as well as membrane fouling and wetting, are identified as major challenges facing this technology. Operating experience with full and pilot-scale plants is analyzed to assess present and future research questions regarding this emerging technology.