OS w Cielczy Wastewater Treatment Plant, Cielcza, Poland

OS w Cielczy is a wastewater treatment plant located in Cielcza, a village in the Jarocin district of Wielkopolskie province, Poland. The plant serves a population of approximately 257,000, classifying it as a large agglomeration under EU regulations. Its location in the Warta River basin places it within the broader Oder River catchment, which drains into the Baltic Sea. As a large agglomeration in Poland, the plant is subject to the EU Urban Waste Water Treatment Directive 91/271/EEC, which requires secondary biological treatment as a minimum. For sensitive areas, such as those draining into the Baltic Sea, more stringent tertiary treatment may be required to reduce nutrient loads. The plant's treatment processes are designed to meet these regulatory standards, ensuring compliance with Polish and EU water quality objectives. The treated effluent from OS w Cielczy is discharged into local watercourses that flow into the Warta River, a major tributary of the Oder. The Oder River ultimately reaches the Baltic Sea, a semi-enclosed sea sensitive to eutrophication from nutrient pollution. The plant plays a critical role in protecting downstream aquatic ecosystems, including the Oder estuary and Baltic coastal waters, by reducing organic and nutrient loads.

The plant discharges into the Warta River basin, part of the Oder River catchment that flows into the Baltic Sea. The Baltic Sea is a brackish water body highly sensitive to eutrophication, driven by nitrogen and phosphorus inputs from wastewater and agriculture. The plant's nutrient removal performance is therefore ecologically significant for maintaining water quality in downstream rivers and the coastal marine environment.