TP 375 of Lahden kt Wastewater Treatment Plant, Lahti, Finland

TP 375 of Lahden kt is a municipal wastewater treatment plant located in Lahti, in the Päijät-Häme region of southern Finland. The plant serves a population of around 90,000, classifying it as a large agglomeration under EU regulations. It is situated inland, approximately 50 km from the coast, and its operations are integral to the region's water management infrastructure. As a facility serving over 10,000 population equivalents, TP 375 of Lahden kt is subject to the EU Urban Waste Water Treatment Directive (91/271/EEC), which mandates secondary treatment as a minimum standard. For larger agglomerations in sensitive areas, tertiary treatment may be required to reduce nutrient loads, particularly phosphorus and nitrogen, which are key concerns in the Baltic Sea catchment. The plant's designed capacity is 1.00 (likely in thousands of cubic meters per day), indicating a substantial treatment capability. The treated effluent from the plant is discharged into local water bodies that ultimately drain into the Gulf of Finland, part of the Baltic Sea. The Baltic Sea is a brackish, semi-enclosed sea with limited water exchange, making it highly sensitive to nutrient pollution. Effective wastewater treatment at plants like TP 375 of Lahden kt is crucial for reducing eutrophication and protecting the marine ecosystem, which supports diverse aquatic life and important fisheries.

The plant's treated wastewater flows into the local river network, which drains into the Gulf of Finland, a sub-basin of the Baltic Sea. The Baltic Sea is ecologically sensitive due to its brackish waters, limited circulation, and vulnerability to eutrophication from nutrient inputs. Effective nutrient removal at this plant helps protect downstream habitats, including coastal wetlands and spawning grounds for fish species such as pike and perch.