ONNENS Wastewater Treatment Plant, Onnens (VD), Vaud, Switzerland

ONNENS is a wastewater treatment plant located in Onnens (VD), in the District du Jura-Nord vaudois, Vaud, Switzerland. It serves a small community of 599 people, reflecting its role in a rural or peri-urban setting within the Swiss wastewater infrastructure. The plant employs advanced treatment processes, which go beyond secondary treatment to remove nutrients and other pollutants. With a designed capacity of 1000 m³/day and a current discharge volume of 271.90 m³/day, the facility operates well within its capacity. Under Swiss regulations, which align with the EU Urban Waste Water Treatment Directive, advanced treatment is typical for sensitive areas to protect water quality. The treated effluent is discharged into the local watershed, which ultimately drains into Lake Neuchâtel, one of the largest lakes in Switzerland. This lake is part of the Rhine basin and supports diverse aquatic life, making the plant's advanced treatment crucial for maintaining ecological balance in the region.

The plant discharges into a watercourse that flows into Lake Neuchâtel, a large lake in western Switzerland. Lake Neuchâtel is part of the Rhine basin and ultimately drains into the North Sea. The lake supports a rich ecosystem, including fish species such as perch and pike, and is an important migratory corridor for birds. Advanced treatment at ONNENS helps protect this sensitive lacustrine environment from nutrient pollution.