ARA Ergolz 2 Wastewater Treatment Plant, Füllinsdorf, Basel-Landschaft

ARA Ergolz 2 is a municipal wastewater treatment plant located in Füllinsdorf, in the canton of Basel-Landschaft, Switzerland. It serves a population of approximately 52,000, classifying it as a medium to large agglomeration under Swiss and EU frameworks. The plant is situated in the Ergolz river valley, part of the Rhine basin. As a Swiss facility, ARA Ergolz 2 is subject to the Swiss Water Protection Act (Gewässerschutzgesetz), which mandates advanced treatment to protect sensitive water bodies. For agglomerations of this size, secondary treatment with nutrient removal (nitrogen and phosphorus) is standard, often meeting tertiary-level standards. The plant's design and operation align with these requirements to minimize environmental impact. The treated effluent from ARA Ergolz 2 is discharged into the Ergolz River, a tributary of the Rhine. The Rhine ultimately flows into the North Sea. The local watershed supports diverse aquatic life, including fish species such as brown trout and grayling. The plant plays a key role in maintaining water quality in this ecologically sensitive region, which is also important for drinking water supply and recreation.

ARA Ergolz 2 discharges into the Ergolz River, which flows into the Rhine River and then the North Sea. The Ergolz watershed is ecologically sensitive, supporting diverse aquatic life including salmonid fish. The plant's nutrient removal helps prevent eutrophication in downstream waters, particularly the Rhine, which is a major European waterway.