Environmental systems analysis of wastewater systems in a river basin – case study Sävjaån
The EU framework directive states that all water bodies within the union should achieve good ecological status 2015. Reducing discharges from on-site wastewater systems is identified as an important means to ameliorate the quality of Swedish waters. This article presents a tool, VeVa River Basin, developed to assess the environmental impact from sewage systems in a river basin. Three scenarios for the year 2030 were compared with the existing systems in a case study of Sävjaån in the municipality of Uppsala, Sweden. Modelling results indicated that the phosphorus discharge to Sävjaån River from existing on-site wastewater systems could be reduced by 70 %. Consequently, existing systems in the area should be attended to, regardless of a presumptive future expansion in the area or types of wastewater systems chosen. The minimum phosphorus discharge was achieved in the scenario with connection to central systems, however the sensitivity analysis illustrates that the differences are marginal owing to variation in system performances. The modelling also included nutrient recycling, energy analysis and discharge of nitrogen, BOD7 and cadmium. The future version of VeVa River Basin, where a cost module is included, will be a very useful tool for selecting measures in river basin management plans.