Unlocking the circular economy potential of spent dialysate in hemodialysis.

Spent dialysate, a byproduct of hemodialysis, is traditionally discarded but holds significant potential for resource recovery within a circular economy framework. This literature review synthesizes research on the composition, ecotoxicological risks, treatment technologies, and resource recovery opportunities of spent dialysate. Characterized by high salinity, nitrogenous compounds, and contaminants like antibiotic resistance genes (ARGs), per- and polyfluoroalkyl substances (PFAS), and microplastics, spent dialysate poses moderate environmental risks, including eutrophication and antimicrobial resistance dissemination. Advanced treatment methods, such as reverse osmosis (RO) and nanofiltration (NF), effectively remove contaminants, while struvite crystallization and energy recovery via heat exchangers and microbial fuel cells (MFCs) enable the valorization of water, nutrients, and energy. These approaches reduce carbon emissions by 30-50% and offer economic benefits through cost savings and revenue generation. However, regulatory gaps, high infrastructure costs, and limited research on microplastics highlight the need for further investigation to fully realize the circular potential of spent dialysate. This review synthesizes these challenges, identifies key implementation barriers, and outlines critical research priorities to translate this promising concept into sustainable practice.