Life cycle assessment of adsorption-based phosphorus recovery from municipal wastewater

Phosphorus (P) has a dual role as a pollutant in water and an essential nutrient in agriculture. Phosphate rock has been designated as a critical raw material by the European Union, highlighting the need for recovering P from waste streams. Urban wastewater represents a potential secondary source of P. Whereas conventional treatment primarily focuses on removal to comply with regulatory discharge limits, in recent years increasing attention has been directed toward approaches facilitating P recovery. This study evaluates the environmental performance of an innovative phosphorus removal and recovery process based on adsorption using calcined pyroaurite (Mg–Fe LDH), applied to municipal wastewater treatment in a small-scale plant. The analysis was performed through a Life Cyle Assessment (LCA) in openLCA, using foreground data from process modelling and background data from the Ecoinvent database, considering 1 m³ of treated wastewater as the functional unit. The adsorption system was compared with chemical precipitation using aluminum chloride as benchmarking process. The results show that the adsorption-based system achieves lower impacts in most of the considered impact categories, including eutrophication and global warming potential, particularly when the environmental credit associated with phosphorus recovery is included. Resource depletion is the only category where adsorption shows higher impacts than the benchmark, due to the synthesis of the adsorbent and regeneration reactants. A sensitivity analysis highlights as key areas of improvement for the adsorption process an increased adsorbent lifetime, the use of acid waste streams instead of HCl in the regeneration process, and the decarbonization of lime production. Overall, the study demonstrates the potential of adsorption followed by phosphorus recovery as a sustainable alternative, within a circular economy perspective.