CALVIA Wastewater Treatment Plant, Calvià, Illes Balears, Spain

The CALVIA wastewater treatment plant is located in Calvià, on the island of Mallorca in the Illes Balears, Spain. It serves a small population of 1,996 residents and operates with secondary treatment, which is the standard for coastal communities under the EU Urban Waste Water Treatment Directive (91/271/EEC). The plant has a designed capacity of 15,000 m³/day, indicating it is sized to handle seasonal tourist flows common to the Balearic Islands. As a secondary treatment facility, CALVIA removes organic matter and suspended solids before discharging treated effluent. The plant's discharge volume of 473.88 m³/day is well below its design capacity, suggesting it operates with significant reserve. Under EU regulations, coastal discharges from agglomerations of this size require secondary treatment to protect marine environments. The treated wastewater is discharged into the Mediterranean Sea, as the plant is situated less than 10 km from the coast. The receiving waters are part of the Balearic Sea, an ecologically sensitive area supporting seagrass meadows and diverse marine life. Proper treatment is essential to prevent nutrient enrichment and protect coastal water quality.

The plant discharges into the Mediterranean Sea via the Balearic Sea, a semi-enclosed basin with limited water exchange. The coastal waters near Calvià support Posidonia oceanica seagrass meadows, which are critical for biodiversity and carbon sequestration. Secondary treatment reduces organic load and suspended solids, helping to prevent eutrophication and maintain the ecological health of this sensitive marine environment.