Hemodialysis, a critical treatment for end-stage renal disease, generates substantial volumes of spent dialysate, a wastewater stream traditionally managed as a disposal challenge. Recent research has shifted focus toward its potential as a resource within a circular economy framework, emphasizing water, nutrient, and energy recovery to enhance sustainability in healthcare.1 Spent dialysate's distinct properties make it a promising candidate for valorization,1,2 but contaminants like antibiotic resistance genes (ARGs),3 per- and polyfluoroalkyl substances (PFAS),4 and microplastics5 raise environmental concerns. This review synthesizes the literature on spent dialysate's characteristics, ecotoxicological risks, possible treatment technologies, and resource recovery potential, highlighting opportunities and challenges for sustainable hemodialysis practices.

A systematic review of the literature was conducted to synthesize current knowledge on the resource recovery potential of spent dialysate from hemodialysis. The primary objective was to identify and evaluate technological strategies for its valorization within a circular economy framework, and to assess their environmental and economic impacts.

The search was executed across three major scholarly databases: Scopus, PubMed, and Web of Science. The investigation targeted English-language articles published between January 2000 and June 2024 to capture the evolution of relevant technologies and policies. The search strategy utilized a combination of keywords and Boolean operators to maximize coverage: (“spent dialysate” OR “dialysis wastewater” OR “hemodialysis effluent”) AND (“circular economy” OR “resource recovery” OR “valorization” OR “water reclamation” OR “nutrient recovery” OR “energy recovery”).

Following duplicate removal, 46 unique articles were retained for screening. The titles and abstracts of these articles were screened for relevance based on predefined criteria. Studies were included if they focused on the composition, management, treatment, environmental impact, or resource recovery pathways of spent dialysate. Articles that focused exclusively on clinical dialysis techniques without addressing effluent management were excluded.

The full text of the remaining relevant articles was assessed for eligibility. To ensure a comprehensive analysis, the reference lists of these key publications were hand-searched for additional pertinent sources, a process known as snowballing. This rigorous selection process resulted in the final inclusion of 15 references that form the core evidence base for this review.

The quantitative data presented in this manuscript, including figures on energy consumption, cost estimates, and potential savings, are derived from the data reported in this compiled literature. Where specific calculations are presented, for example struvite production or CO2 savings, they are based on applying these literature-derived figures to standardized scenarios, as noted in the text.

Spent dialysate is characterized by high salinity, moderate levels of ammonia nitrogen and orthophosphates, low BOD, and minimal bacterial contamination.1,2 However, its environmental impact is complicated by emerging contaminants. ARGs, such as erm (36) and mtrD-02, along with antibiotics like betalactams, fluoroquinolones, and aminoglycosides, have been detected in dialysis sewage, highlighting potential risks for the spread of antimicrobial resistance in wastewater ecosystems.6–8 Similarly, PFAS compounds such as PFOA and PFOS have been detected at levels that necessitate stringent management to mitigate their environmental persistence.4 Micro- and nanoplastics, resulting from equipment wear (e.g., membrane rupture, bloodline abrasion), further complicate disposal,5 acting as vectors for ARGs and resistant bacteria9 (Figs. 1 and 2). Ecotoxicological studies underscore moderate ecological risks. Tests on Daphnia magna and Euglena gracilis reveal acute EC50 values of 86.91% and 76.90%, respectively, dropping to 25% under chronic exposure, indicating cumulative toxicity.7 High nutrient concentrations risk eutrophication if untreated, with potential to disrupt aquatic ecosystems. These findings highlight the need for advanced treatment to mitigate environmental impacts while enabling resource recovery.

Fig. 1.

Sources of micro and nanoplastics in dialysis.

Fig. 2.

The role of microplastics in antibiotic resistance.

The literature identifies two primary treatment approaches for spent dialysate: membrane-based technologies (RO and nanofiltration) and electrochemical oxidation. RO and nanofiltration achieve >95% removal of salinity, pathogens, PFAS, and ARGs, with energy consumption of 0.5–1.2kWh/m3.2,10,11 Their cost-effectiveness (OPEX: $0.7–0.75/m3) and scalability make them preferred for large-scale hemodialysis facilities.2 In contrast, electrochemical oxidation removes 60–70% of salinity and nitrogen but incurs higher costs (OPEX: $1.13–1.31/m3) and is less efficient for demineralization.12–14 The choice of technology depends on dialysate composition and facility priorities, with membrane-based methods favored for their proven performance and lower operational costs.

Adopting a circular economy model for spent dialysate can reduce environmental impacts by an estimated 30–50% compared to conventional linear disposal, as illustrated in Fig. 3.17–19 This reduction is achieved through multiple pathways: water reclamation (saving ∼0.28kg CO2/m3), energy recovery (avoiding ∼0.6kg CO2/kWh), and nutrient recycling via struvite production (saving ∼0.35kg CO2/kg)1 (Fig. 4). A significant additional benefit is the mitigation of potent methane emissions that would otherwise result from the anaerobic digestion of organic matter in wastewater, preventing an estimated 0.48kg CH4/kg BOD.20,21 Economically, these strategies translate to net cost reductions of 15–25% for facilities, stemming from lower utility and waste management expenses and potential revenue from struvite sales. While the precise figures are literature-based estimates subject to variation based on local conditions and technological scale, the compelling synergy of environmental and economic benefits firmly positions spent dialysate management as a pioneering model for sustainable healthcare.

Fig. 3.

Comparative evaluation of recovered resources use versus new resources use on carbon emissions saving in hemodialysis.

Fig. 4.

Impact of resources recovery from spent dialysate in carbon emission minimization of hemodialysis treatment.

Despite its potential, several challenges persist. High initial capital costs for RO, NF, and energy recovery systems limit adoption, particularly in smaller facilities and satellite units which lack the space and capital budgets of large hospital-based centers. Recent analyses suggest that next-generation polymeric membranes with antifouling properties could improve the long-term economic feasibility of closed-loop systems.23 Regulatory frameworks often fail to address spent dialysate's unique composition, creating uncertainty around the classification of reclaimed water and recovered products like struvite, and necessitating tailored policies. The environmental impact of dialysis-derived microplastics and ARGs remains underexplored, requiring long-term ecotoxicological studies. Scaling up resource recovery demands specialized infrastructure, staff training for new operational protocols, and supply chains for struvite and energy markets. Future research should prioritize: (1) Techno-economic assessments for different facility sizes and settings; (2) Long-term ecotoxicological studies on microplastics and ARGs; (3) Development of standardized regulatory guidelines for spent dialysate valorization; and (4) Pilot-scale demonstrations to validate operational feasibility and real-world benefits.

The literature underscores the transformative potential of spent dialysate as a resource within a circular economy framework. Advanced treatment technologies like RO and nanofiltration, coupled with struvite crystallization and energy recovery, enable the valorization of water, nutrients, and energy, reducing environmental impacts by 30–50% and generating economic benefits. However, challenges such as high costs, regulatory gaps, logistical barriers, and emerging contaminants like microplastics and ARGs highlight the need for further research and policy support. By addressing these barriers through targeted research, pilot projects, and collaborative policy development, spent dialysate can serve as a model for sustainable healthcare, aligning environmental, economic, and clinical goals.

Authors declare any interest, financial support or relationship that may pose a conflict of interest.

The authors declare that they have no conflict of interest.