Arreigada Wastewater Treatment Plant, Arreigada, Portugal

Arreigada wastewater treatment plant is located in the town of Arreigada, within the municipality of Paços de Ferreira, in the Porto district of northern Portugal. The plant serves a population of approximately 14,500 people, placing it in the medium agglomeration category under EU classification. As a Portuguese facility, the plant operates under the EU Urban Waste Water Treatment Directive 91/271/EEC, which requires secondary treatment for agglomerations of this size. Portuguese wastewater infrastructure is regulated by the Portuguese Environment Agency (APA) and regional water authorities. The plant discharges into the local watershed, which is part of the Douro River basin. The Douro River flows westward through northern Portugal and into the Atlantic Ocean at Porto. The downstream environment supports diverse aquatic life and is an important ecological corridor in the region.

The plant's receiving waters are part of the Douro River basin, which drains into the Atlantic Ocean near Porto. The Douro estuary and coastal zone are ecologically sensitive areas that support diverse fish and bird species. The plant's discharge contributes to the overall water quality of the basin, which is used for agriculture, recreation, and supports downstream ecosystems.