Ilza Wastewater Treatment Plant, Koszary, Mazowieckie, Poland

The Ilza wastewater treatment plant is located in Koszary, within the gmina Iłża, powiat radomski, in the Mazowieckie voivodeship of Poland. It serves a population of approximately 6,300 people, making it a medium-sized agglomeration under Polish and EU classification. The plant operates at the secondary treatment level, which is the minimum standard required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. The designed capacity is 5,600 m³/day, and the current discharge volume is 898.28 m³/day, indicating operational capacity well within design limits. The treated effluent is discharged into local watercourses that ultimately drain into the Vistula River basin, the largest river in Poland. The Vistula flows northward into the Baltic Sea, supporting diverse aquatic ecosystems and providing water for agriculture and industry along its course.

The plant discharges into the Vistula River basin, which flows through central Poland and empties into the Baltic Sea via the Gulf of Gdańsk. The Vistula supports a variety of fish species, including salmon and sturgeon, and its delta is an important wetland area for migratory birds. Secondary treatment helps reduce nutrient loads, protecting downstream water quality and marine ecosystems.