Mazsalacas NAI Wastewater Treatment Plant, Mazsalaca, Latvia

Mazsalacas NAI is a wastewater treatment plant located at 35 Parka iela in Mazsalaca, Valmieras novads, Latvia. The plant serves a small population of 447 residents and is classified as a secondary treatment facility. It is currently closed, though it previously operated as part of the municipal wastewater infrastructure. The plant's designed capacity is 3,810 cubic meters per day, with a recorded discharge volume of 85.31 cubic meters per day. As a secondary treatment plant, it would have provided biological treatment to reduce organic matter and suspended solids. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), small agglomerations like Mazsalaca (under 2,000 population equivalent) are typically required to provide appropriate treatment, though secondary treatment is common for this scale. The plant's discharge likely flows into local watercourses within the Salaca River basin, which drains into the Baltic Sea. The Salaca River is an important ecological corridor supporting diverse aquatic life and migratory fish species. Possibly to a newer or consolidated facility.

The plant is located inland, over 50 km from the coast, and its treated effluent would have discharged into the Salaca River basin. The Salaca River flows into the Gulf of Riga, part of the Baltic Sea, a brackish water body with sensitive ecosystems. The river supports diverse aquatic life, including salmonids and other migratory fish, and its watershed is ecologically significant for the region.