A district in the Swedish city of Helsingborg is using a wastewater separation system to recover water, energy and nutrients offering a model for improving water security amid rising climate pressures.
In the Oceanhamnen district, wastewater is divided into three separate streams. Toilet waste, or blackwater is collected through one pipeline while greywater from showers, sinks, laundry and dishwashers travels through another. Food waste from kitchen sinks is sent separately for biogas production.
The source separation system allows different waste streams to be treated according to their properties. Greywater contains fewer contaminants than blackwater and can be treated for uses such as toilet flushing and irrigation. Helsingborg is also considering using recycled greywater in a new public swimming pool if it meets the required quality standards.
The system also recovers energy and nutrients. Blackwater and food waste can generate biogas while blackwater contains nitrogen and phosphorus that can be recovered for fertiliser production. Researchers say separating these waste streams can also improve nutrient recovery compared with conventional mixed sewage treatment.
However, wastewater reuse still faces challenges, including contamination from pharmaceuticals and personal care products, regulatory gaps, treatment costs and public concerns about safety. At Oceanhamnen, treated greywater passes through fine membrane filtration to reduce unwanted residues.
The approach does not eliminate water scarcity on its own but researchers say separating wastewater at the source could make water reuse and resource recovery more efficient and help cities adapt to increasing pressure on freshwater supplies.