In the southern Swedish city of Helsingborg, a new district is testing a different way of handling sewage. Instead of sending all household wastewater into one mixed system, the Oceanhamnen district separates it into three pipelines: blackwater from toilets, greywater from sinks, showers and washing machines, and kitchen food waste, which is routed to biogas production.
The approach matters because Sweden reuses only about 0.6 percent of its wastewater, and 15 of its 21 counties face water scarcity. Qatar, by comparison, reuses roughly 90 percent of its wastewater. Source separation of this kind has so far been used mainly in single homes or small neighbourhoods, which makes the Helsingborg project a notable step up in scale. The reporting describes RecoLab, which operates there, as running the world's largest source-separated sanitation plant.
Greywater is the easiest stream to recycle. Once treated, it can be used for toilet flushing or for irrigation, and the city plans to use treated greywater in a new public swimming pool, pending confirmation that its water quality is suitable. Blackwater and food waste are valuable for different reasons: together they yield about 80 percent more methane than mixed wastewater, and blackwater-derived fertiliser can replace mineral fertiliser, whose production is energy-intensive. Separating the streams also recovers about 80 percent of the nitrogen, compared with less than half from mixed sludge. Urine-diverting toilets could supply concentrated liquid or dried fertiliser.
Significant obstacles remain. Legal frameworks have not caught up with the approach, and questions of pricing, logistics and public perception still need answers. Pharmaceutical residues are also unresolved: they currently have no legal limits and are difficult to measure, which complicates the reuse of treated water and fertiliser. Whether the Helsingborg model can be replicated will depend on how these issues are settled.
We rewrote this story on 4 November 2026 after an editorial review.
Credit. Based on reporting by Ashley Hall and Isabell Fritz for The Conversation Science. Is this your work? Write to us.
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