Stromiec Wastewater Treatment Plant, Koszary, Poland

The Stromiec wastewater treatment plant is located in Koszary, within the gmina Zwoleń, powiat zwoleński, województwo mazowieckie, Poland. It serves a population of 1,225, classifying it as a small agglomeration under Polish and EU regulations. The plant operates under the EU Urban Waste Water Treatment Directive 91/271/EEC, which requires secondary treatment for agglomerations of this size in inland areas. Poland's national implementation of the directive ensures compliance with discharge standards for biological oxygen demand and suspended solids. The plant provides secondary treatment, which is the minimum required for small inland communities under the EU directive. Its designed capacity is 5,166 m³, and the actual discharge volume is 174.67 thousand m³ per year, indicating a utilization rate well below capacity. This suggests the plant is sized for future growth or seasonal variations. Secondary treatment typically involves biological processes such as activated sludge or trickling filters. The treated effluent is discharged into a local watercourse that ultimately drains into the Vistula River basin, which flows northward into the Baltic Sea. The Vistula is Poland's largest river and supports diverse aquatic ecosystems, including important fish spawning grounds. The plant's operation helps protect downstream water quality in the Vistula and the Baltic Sea from nutrient pollution.

The plant discharges into a local tributary of the Vistula River, Poland's longest river, which flows into the Baltic Sea. The Vistula basin supports diverse aquatic life, including migratory fish species. The Baltic Sea is a semi-enclosed sea sensitive to eutrophication from nutrient inputs, making effective wastewater treatment crucial for reducing nitrogen and phosphorus loads.