A study of a urine separation system in an ecological village in Northern Sweden

The development of a sustainable sewerage system includes the utilisation of nutrients from human urine and faeces in agriculture. One strategy for developing a sustainable sewerage system is to handle urine separately and use it as a fertiliser. One important reason for this strategy is the fact that urine is the source of around 70% of phosphorus and around 90% of nitrogen in black wastewater (wastewater from water closets). However, experience from systems with urine separation is limited. In this study a urine separation system in an “ecological” village in northern Sweden has been investigated. The village consists of 17 self-contained houses and the number of inhabitants have varied around 55 persons. The sewerage system is equipped with urine separation toilets. Thus, the urine is intended to be collected separately and led through a sewer system to a collection tank for urine. However, the collected urine was found to be relatively diluted. This could to some extent be explained by errors in the construction of the toilet. However, the main reason for the dilution is probably leakage of water into the urine sewer system. The study also showed that less than about half of the nitrogen and phosphorus from human urine disposed of through the toilets of the village was successfully collected. Thus, the study shows that the successful operation of a urine separation system is very dependent on well-designed toilets and a user behaviour that promotes a high degree of separation.