Scenarios for reduction of nutrient load from point sources in Estonia

摘要

This study aimed to develop scenarios for a further decrease of point source nutrient load in Estonia to achieve the nutrient reduction target levels set up by the HELCOM Baltic Sea Action Plan produced in 2007. A possible reduction in the total phosphorus (TP) and total nitrogen (TN) load has been assessed based on the requirements set up by Estonian and EU legislation as well as the HELCOM recommendations. Scenarios were developed for four urban pollution load classes with different requirements for waste water quality at the outlet of the wastewater treatment plant (WWTP). The results revealed that the load of TP and TN to the sea and to inland surface water bodies can be reduced by 68 and 352 tonnes, respectively, when following the most stringent HELCOM recommendation for the quality of sewerage outlets. These possibly reduced loads form only about 30% of required TP and 40% of TN annual reduction levels in Estonia which are 220 tons of phosphorus and 900 tons of nitrogen. Therefore, further decrease can mostly be made possible by lowering the diffuse load and that can also be problematic.