SuNha or later…

The plant nutrient nitrogen, which is found in municipal wastewater, is not extensively recycled to farmland. The project SuNha or later aims to study how recycling of urban nitrogen can be improved on the basis of the existing handling of wastewater.

In Sweden, the economic value of nitrogen in wastewater from toilets is around five times more worth compared to the phosphorus content, but less than 20 percent of the nitrogen ends up in the wastewater sludge at municipal wastewater treatment plants. The Swedish EPA has proposed that at least 10 percent of the nitrogen in Swedish wastewater should be recovered, which, together with the aim of at least 40 percent phosphorus recovery, means that sludge from wastewater treatment plants will not contain enough nitrogen to fulfil the proposal. Source separation of toilet wastes can lead to almost closed nutrient loops and the dependency of imported mineral fertilisers will decrease.

In Sweden, the amount of nitrogen in the toilet waste corresponds to 20 percent of the sold nitrogen mineral fertilisers. The conventional production of nitrogen mineral fertilisers uses two percent of the world’s energy usage, and the production is heavily dependent on fossil fuels. The nitrogen removal processes at wastewater treatment plants are also very energy-demanding. Increased protein consumption in Sweden has led to increased nitrogen content in the wastewater.

SuNha stands for Sustainable Urban Nitrogen Handling.

Project members from Sweden Water Research