Phosphorus recovery from wastewater and sewage sludge as vivianite

Developing feasible techniques to recover phosphorous (P) from wastewater and sewage sludge is urgent work to meet the huge demand for P resources and wastewater/sludge management. Recently, recovering P as value-added vivianite (Fe3(PO4)2·8H2O) has aroused great interest due to the convenient process operation, high recovery efficiency, and wide applications of vivianite. In this review, qualitative and quantitative detection methods of vivianite have been first analyzed, providing reference to test vivianite content and purity. Advanced technologies for P enrichment and vivianite production, including ion exchange, electrodialysis, capacitive de-ionization, membrane bioreactor, anaerobic fermentation, chemical precipitation, electrochemical crystallization, biomineralization, and anaerobic digestion are then comprehensively summarized. Mechanisms and representative applications of each technique are emphasized. Also, critical parameters (e.g., pH, Fe/P molar ratio, sulfate concentration, microorganisms, supersaturation index, organic matters, and seed crystals) affecting vivianite formation have been systematically analyzed. Furthermore, perspectives regarding fast detection of vivianite, strategies optimization, seed application, and vivianite commercialization have been proposed to guide the development of next-generation techniques for P recovery. This review is expected to provide fundamental insights into cleaner technologies synchronous recovering waste P and producing valued vivianite, as well as to stimulate future studies on circular economy-driven wastewater management.