Oczyszczalnia Miejska Grajewo - Municipal Wastewater Treatment Plant in Gardoty, Poland

Oczyszczalnia Miejska Grajewo is a municipal wastewater treatment plant located in Gardoty, within the podlaskie voivodeship of Poland. It serves a population of around 20,459, classifying it as a medium agglomeration under EU regulations. The plant is situated inland, away from coastal areas, and its operations are part of the regional wastewater infrastructure for the Łomża county area. As a Polish facility serving over 10,000 people, the plant is subject to the EU Urban Waste Water Treatment Directive (91/271/EEC), which requires secondary treatment as a minimum for such agglomerations. Poland has implemented this directive through national regulations, and plants of this scale typically employ biological treatment processes to meet effluent quality standards. The regulatory framework ensures compliance with EU norms. The treated effluent from the plant is discharged into local water bodies within the Narew River basin, which ultimately flows into the Baltic Sea. The plant plays a key role in protecting the region's water quality, supporting aquatic life in the downstream rivers and contributing to the ecological health of the broader Vistula River catchment area.

The plant discharges into the Narew River basin, a major tributary of the Vistula River, which flows into the Baltic Sea. This watershed supports diverse aquatic habitats and is important for migratory fish species. The region's inland location means the plant's effluent affects freshwater ecosystems rather than coastal marine environments, with downstream areas relying on good water quality for biodiversity and human use.