Återvinning av renat avloppsvatten för dricksvattenproduktion – erfarenheter från internationella fallstudier

With climate change causing more intense rainfall events and prolonged droughts, freshwa-ter resources are increasingly under pressure worldwide, including in regions such as Sweden where water scarcity was previously unexpected. While water conservation can reduce de-mand to some extent, long-term water security requires alternative and resilient water sources. Wastewater represents a reliable source, as it is continuously generated in populated areas. With adequate treatment, reclaimed water can be used for irrigation and industrial purposes, and with advanced treatment it can meet potable water standards. Potable reuse can be im-plemented either as indirect potable reuse (IPR), where treated water is recharged into an environmental buffer such as an aquifer, or as direct potable reuse (DPR), where water is treated and directly introduced into the drinking water supply. Potable reuse has been successfully applied for decades, notably in Orange County, USA, and Windhoek, Namibia, and more recently in Europe. Regulatory frameworks have gradual-ly developed since the early 1900s, with major guidance provided by the World Health Or-ganization and regulations such as California Title 22. To ensure drinking water safety, potable reuse systems rely on multiple treatment barriers, commonly including microfiltration or ultrafiltration, reverse osmosis, and UV disinfection, combined with continuous monitoring. This report investigates the potential of using reclaimed wastewater as drinking water through direct potable reuse (DPR) and indirect potable reuse (IPR). The study is based on a literature review and interviews with representatives responsible for five existing facilities in Europe and the United States: Orange County (USA), Torreele (Belgium), Barcelona (Spain), Aalst (Belgium), and Mörbylånga (Sweden). The studied facilities apply multi-stage treatment with several independent microbiological barriers, in which ultrafiltration, reverse osmosis, and UV disinfection constitute the core processes. The results show that both IPR and DPR can produce drinking water of high and stable quality, provided that the treatment processes are combined with continuous monitor-ing, robust operational strategies, and clear regulatory frameworks. The comparison of the case studies indicates that indirect reuse offers advantages in terms of natural remineralization and buffering capacity, while direct reuse provides greater flexibil-ity and faster access to water, particularly in areas where infiltration is not feasible. The study also demonstrates that upstream source control, pilot testing at a sufficient scale and duration, and early and transparent communication with the public are crucial for successful implementation. This work serves as a knowledge base for Kalmar Vatten’s continued planning of a pilot pro-ject for potable water reuse and demonstrates that reclaimed wastewater can be a robust and climate-resilient water source for future water supply systems.