Ustrzyki Dolne Wastewater Treatment Plant, Dźwiniacz Dolny, Poland

The Ustrzyki Dolne wastewater treatment plant is located in Dźwiniacz Dolny, within the gmina of Ustrzyki Dolne in the Bieszczady county of Podkarpackie Voivodeship, Poland. It serves a population of approximately 5,973, classifying it as a small to medium agglomeration under Polish and EU regulations. The plant employs advanced treatment processes, which go beyond the secondary treatment required by the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. With a designed capacity of 14,000 m³/day and an actual discharge volume of 851.66 m³/day, the facility operates well below its capacity, indicating room for future growth or seasonal variations. The treated effluent is discharged into local watercourses that ultimately drain into the San River basin, part of the Vistula River system flowing into the Baltic Sea. The advanced treatment helps protect the sensitive Carpathian ecosystem, which supports diverse aquatic life and serves as an important migratory corridor for species in the region.

The plant's discharge enters local streams that feed into the San River, a major tributary of the Vistula River, which flows into the Baltic Sea. The surrounding Bieszczady region is ecologically sensitive, with forested catchments and diverse wildlife. Advanced treatment reduces nutrient loading, protecting downstream water quality in this mountainous area.