Cavaleira Wastewater Treatment Plant, Algueirão-Mem Martins, Portugal

Cavaleira is a wastewater treatment plant located in the Casal da Cavaleira area of Algueirão, part of the Algueirão-Mem Martins parish in Sintra, Lisbon District, Portugal. The plant serves a population of approximately 5,000 and operates with secondary treatment, which is the standard level required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this size. The plant has a designed capacity of 9,000 m³/day and currently discharges 833.65 m³/day of treated effluent. As a secondary treatment facility, Cavaleira provides biological treatment to reduce organic matter and suspended solids, meeting the effluent quality standards set by Portuguese regulations and the EU directive. The plant's capacity utilization is low, indicating it operates well below its design capacity, which may reflect the current population served or seasonal variations. The regulatory framework ensures that the treated water meets environmental standards before discharge. The plant is situated within 10 km of the Atlantic coast, making its discharge potentially influential on coastal water quality. The treated effluent likely flows into local watercourses that drain into the Atlantic Ocean near the Lisbon coast. The region's coastal ecosystems, including beaches and marine habitats, benefit from proper wastewater treatment to prevent nutrient pollution and protect biodiversity. The plant's operation supports the health of the surrounding watershed and downstream marine environment.

Cavaleira discharges treated wastewater into local streams that eventually reach the Atlantic Ocean near the Lisbon coast. The coastal zone supports diverse marine life and is important for recreation and fisheries. Proper secondary treatment reduces organic load and nutrients, helping to prevent eutrophication and maintain water quality in the nearshore environment.