Nutrient management in sewerage systems : investigations of components and exergy analysis

Abstract: The aim of this thesis is to present results from different experiments dealing with components that may be useful to improve nutrient management within sewerage systems. Further, exergy analysis is used to compare the utilisation of physical resources within different alternatives for sewerage nutrient management. A full-scale pilot plant for natural sludge dewatering, combining freezing/thawing and drying, was evaluated. Complementary studies were performed in laboratory experiments and pilot tests. A satisfactory dewatering result was achieved, the losses of phosphorus were neglible and the losses of nitrogen were small during the dewatering process. An urine separation system in a village in northern Sweden was investigated. About half of the nutrients in the urine disposed to the toilets were successfully collected. A potential drawback to urine handling systems is the risk of ammonia evaporation during handling and treatment. The results from laboratory experiments performed indicate a possibility to use acid to prevent decomposition of urea during storage of urine and thus reduce the risk of ammonia evaporation. The exergy analyses show that urine separation technology may be an interesting alternative to conventional wastewater systems.