Olhalvas Wastewater Treatment Plant, Leiria, Portugal

Olhalvas is a wastewater treatment plant located in Leiria, Portugal, serving a population of approximately 20,700. The plant is situated in the Leiria region, an inland area with a mix of urban and agricultural surroundings. As a municipal facility, it plays a key role in managing wastewater from the local community. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), agglomerations of this size (20,700 population equivalent) are required to provide secondary treatment. Portugal implements this directive through national legislation, ensuring that plants like Olhalvas meet appropriate standards for organic matter and suspended solids removal. The treated effluent from Olhalvas is discharged into the local watershed, which ultimately drains into the Atlantic Ocean via the Lis River basin. The receiving water bodies support diverse aquatic life and are important for regional ecology. Proper treatment helps protect water quality in downstream environments, including coastal areas.

Olhalvas discharges into the Lis River basin, which flows into the Atlantic Ocean near the city of Leiria. The watershed supports freshwater and estuarine habitats, providing critical ecosystem services. The plant's treatment helps maintain water quality in this ecologically sensitive area, which is important for local biodiversity and downstream coastal environments.