STEP MONTIGNEZ Wastewater Treatment Plant, Basse-Allaine, Jura, Switzerland

STEP MONTIGNEZ is a municipal wastewater treatment plant located in Montignez, part of the Basse-Allaine municipality in the Jura canton of Switzerland. The plant serves a small population of 242 residents, reflecting the rural character of the area near the French border. The plant provides secondary treatment, which is the standard biological treatment required under Swiss water protection law (Gewässerschutzgesetz). This level of treatment effectively removes organic matter and suspended solids. With a design capacity of 567 m³/day and an actual discharge volume of 109.85 m³/day, the plant operates well below its capacity, indicating room for future growth or seasonal variations. The treated effluent is discharged into local watercourses that eventually drain into the Allaine River, a tributary of the Doubs River, which flows into the Saône and ultimately the Rhône River to the Mediterranean Sea. The plant plays a key role in protecting the sensitive aquatic ecosystems of the Jura region, which support diverse freshwater species and maintain water quality for downstream communities.

The plant discharges into the Allaine River basin, which flows into the Doubs River, a major tributary of the Saône River, part of the Rhône watershed that reaches the Mediterranean Sea. The Jura region features karstic geology, making groundwater and surface waters particularly vulnerable to pollution. The plant's secondary treatment helps protect downstream aquatic habitats, including fish spawning grounds and macroinvertebrate communities.