Ostrow Mazowiecka Wastewater Treatment Plant, Żabieniec | Poland

The Ostrow Mazowiecka wastewater treatment plant is located in Żabieniec, within the powiat piaseczyński of województwo mazowieckie, Poland. It serves a population of around 29,500 people, classifying it as a medium-sized agglomeration under EU definitions. As a Polish facility, the plant operates under the EU Urban Waste Water Treatment Directive 91/271/EEC, which requires secondary treatment for agglomerations of this size. The directive also mandates more advanced treatment if the receiving waters are designated as sensitive areas, which is common in the Vistula basin. The plant's treated effluent is discharged into local watercourses that ultimately drain into the Vistula River, Poland's longest river, which flows into the Baltic Sea. This makes the plant's performance important for both local water quality and the broader Baltic Sea ecosystem, which is sensitive to nutrient pollution.

The plant discharges into tributaries of the Vistula River, which flows northward through central Poland and empties into the Baltic Sea via the Gdańsk Bay. The Baltic Sea is a semi-enclosed, brackish sea highly sensitive to eutrophication from nutrient inputs. Effective treatment at this plant helps reduce nitrogen and phosphorus loads, supporting the health of downstream aquatic habitats and the coastal marine environment.