STEP LAJOUX Wastewater Treatment Plant, Lajoux, Jura, Switzerland

STEP LAJOUX is a municipal wastewater treatment plant located in Lajoux, a small village in the Jura canton of Switzerland. Serving a population of 406, the plant is part of the region's decentralized wastewater infrastructure, typical for rural alpine communities. The plant provides secondary treatment, which is the standard biological treatment level required under Swiss water protection law (Gewässerschutzgesetz). With a designed capacity of 950 m³/day, it operates well below its maximum, reflecting the low population density of the area. The actual discharge volume is 184.29 m³/day, indicating efficient use of the infrastructure. The treated effluent is released into the local stream system, which drains into the Sorne River, a tributary of the Birs River, ultimately flowing into the Rhine River and the North Sea. The plant plays a key role in protecting the sensitive Jura mountain streams and the downstream aquatic ecosystems.

The plant discharges into a small stream in the Franches-Montagnes region, part of the Jura mountain watershed. This stream flows into the Sorne River, then the Birs, and eventually the Rhine River, which drains into the North Sea. The Jura region features karstic geology, making groundwater particularly vulnerable to contamination, so the secondary treatment helps protect local springs and the diverse aquatic life in these cold, oxygen-rich streams.