os3 Wastewater Treatment Plant, Żyrardów, Mazowieckie, Poland

os3 is a former wastewater treatment plant located in Żyrardów, within the Mazowieckie voivodeship of Poland. The plant provided secondary treatment for the local community before its closure, reflecting the evolving infrastructure needs of the region. As a secondary treatment facility, os3 would have met the basic requirements of the EU Urban Waste Water Treatment Directive (91/271/EEC), which mandates secondary biological treatment for agglomerations of this scale. Polish regulations transpose this directive, ensuring that treated effluent meets quality standards for discharge into surface waters. Żyrardów lies within the Vistula River basin, which drains into the Baltic Sea. The Vistula is Poland's largest river system, supporting diverse aquatic ecosystems and providing water for agriculture and industry. The closure of os3 suggests that wastewater treatment in the area has been consolidated or upgraded to meet modern environmental standards.

The plant is located inland in the Mazowieckie region, within the Vistula River basin. The Vistula flows northward into the Baltic Sea, a sensitive marine environment. The basin supports important habitats for fish and migratory birds, and nutrient management is critical to prevent eutrophication in the Baltic. The closure of os3 may reduce local discharge impacts, but the overall watershed health depends on the performance of remaining treatment facilities.