Rojas c NAI Wastewater Treatment Plant, Roja, Latvia

Rojas c NAI is a wastewater treatment plant located in Roja, a coastal settlement in Talsu novads, Latvia. The plant serves a population of around 2,981, placing it in the small agglomeration category under EU regulations. It operates secondary treatment, which is the minimum standard required by the EU Urban Waste Water Treatment Directive for freshwater discharges from settlements of this size. The plant has a designed capacity of 6,250 cubic meters per day and currently discharges an average daily volume of 308 cubic meters, indicating significant spare capacity. As a coastal facility within 10 km of the Baltic Sea, the plant's effluent may be subject to additional nutrient removal requirements under the EU directive, particularly if the receiving waters are designated as sensitive areas. The treated wastewater from Rojas c NAI ultimately reaches the Baltic Sea, a brackish inland sea with limited water exchange. The Baltic Sea is ecologically sensitive, facing challenges such as eutrophication from nutrient inputs. The plant's secondary treatment helps reduce organic pollution, but nutrient removal may be needed to protect the marine environment.

The plant discharges into the Baltic Sea via local drainage, likely through the Roja River or direct coastal outfall. The Baltic Sea is a semi-enclosed brackish sea with slow water renewal, making it vulnerable to nutrient enrichment. Eutrophication from nitrogen and phosphorus inputs is a major concern, affecting water quality and marine biodiversity. The plant's secondary treatment reduces biochemical oxygen demand but may not fully address nutrient loads, which is a key consideration for coastal plants in this region.