Innovative solutions, like safe reuse, are required in water and sludge managementto achieve circular economy and to address the challenges of global waterscarcityand soil nutrient loss. In the research project “REASSURE”, the overall aimwas to enhance the understanding of the potentiality and sustainability of usingdomesticwastewater as a resource in Sweden and abroad, with a focus on hazardouspollutants,metals and microplastics. The project had the following specificobjectives:

1. Determine factors that influence or determine the reuse of wastewater and sludgeacross countries;

2. Characterize the current state of wastewater reuse in Sweden and the occurrenceof hazardous pollutants as obstacles to its reuse;

3. Evaluate the effectiveness of different advanced treatment techniques againsthazardous pollutants for a better effluent water quality;

4. Assess the risks of hazardous pollutants to environmental and health impactsassociated with wastewater as a resource.

This literature synthesis project presents insights into the influencing factors forcross-national differences in the reuse of wastewater and sludge. Data on nationalwastewater and sludge reuse was compiled along with relevant national statistics.Sludge data is compiled in this report for cross-national comparison only. Wastewaterreuse showed a positive correlation with fraction of wastewater treated, degreeof urbanization, level of water stress, and GDP per capita. The project also discussesthe situation of wastewater reuse in selected countries of interest, indicating thatreuse practices, policies, and applications vary across these countries.

A comprehensive compilation of hazardous contaminants in effluent water forSwedish domestic and municipal wastewater, greywater, and blackwater was performedfrom literature. A workflow for literature review, meta-analysis and risk andhazard evaluation of contaminants (based on 14 parameters) in effluent wastewaterwas established. In addition, criteria for risk-based scoring, ranking, and prioritizationof contaminants is also presented. This resulted in a priority list of 119 specificchemical contaminants of emerging concern (CECs) that can hinder sustainablewastewater reuse. Among the priority chemicals identified, 30 (primarily pharmaceuticals)had a risk quotient ≥ 1, indicating ecological risk. Additionally, 16 chemicalswere flagged as environmental hazards due to their persistence and mobility,while approximately 60 chemicals were associated with positive predictions for atleast four human health hazards. The 10 highest-priority chemicals were venlafaxine,bicalutamide, desvenlafaxine, diclofenac, amoxicillin, clarithromycin, diethyltoluamide,genistein, azithromycin, and fexofenadine. Although there can be a numberof different potential options for wastewater reuse, this report has primary focuson agricultural irrigation for wastewater reuse, given that agriculture is the largestconsumerof freshwater globally (United Nations, 2024). In Sweden, the reuse oftreatedmunicipal wastewater for irrigation could be especially advantageous forfarmersin areas that experience significant water shortages during the growingseason(Swedish Environmental Protection Agency, 2022)

The project also looks into available treatment technologies and their combinationsfor removal of these priority chemicals. Information on available advanced treatmenttechnologies and their targeted chemical contaminants are compiled from theSwedish literature, and removal efficiencies of five selected technologies (granularactivated carbon (GAC), ozonation, membrane bioreactor (MBR), nano-filtration(NF), and reverse osmosis (RO) for 38 priority chemicals, from international literature,were used to rank these technologies. Furthermore, it explores the link betweenadvanced treatment technologies and the pollutant properties, and provides a costanalysis of these selected technologies. Considering its effectiveness to remove CECsand the lower cost, GAC, or a combination of technologies, may be used for safewastewater reclamation.

The driving factors of wastewater and sludge reuse are useful for evaluating thepotential of reusing such resources and development of new water managementplans on recycling wastewater as sustainable water resource. Chemical pollutantsidentified as impediments to treated wastewater reuse can help in establishingcriteria for the risk management plans under the EU regulation on wastewater reuse(Regulation (EU) 2020/741). The risk characterization and policy support, are greatlyrelevant to the Swedish Environmental Protection Agency for providing guidelineson reducing the spread of hazardous pollutants to the environment due to wastewaterreuse. Advanced treatment options and strategies presented here will facilitatethe municipalities’ responsible for wastewater treatment facilities to considermodernizing their existing treatment facilities and even facilities on future planto purify the wastewaters for reuse to a greater extent. Future policy briefs shouldconsider to focus on reducing the presence of priority chemicals in effluent water byestablishing concentration limits and mandating advanced treatment technologies,based on removal efficiency and ecological risk assessments. These should be integralto future regulations. As the dataset is derived from available literature, furtherstudies and reanalysis using the meta-analysis workflow will be necessary to addresspotential unknown chemicals.