ARA Birsig Wastewater Treatment Plant, Therwil, Basel-Landschaft, Switzerland

ARA Birsig is a municipal wastewater treatment plant located in Therwil, within the canton of Basel-Landschaft, Switzerland. The plant serves a population of around 27,242 people, making it a medium-sized facility in the region. Switzerland's wastewater treatment plants operate under the Swiss Water Protection Act (Gewässerschutzgesetz), which mandates advanced treatment standards. For agglomerations of this scale, secondary treatment with nutrient removal is typically required to protect sensitive water bodies. The plant's treated effluent is discharged into the Birsig River, a tributary of the Rhine River. The Rhine ultimately flows into the North Sea, making this plant part of a large international river basin. The Birsig River supports diverse aquatic life and is an important ecological corridor in the Basel region.

ARA Birsig discharges into the Birsig River, which flows into the Rhine River near Basel. The Rhine is a major European waterway that drains into the North Sea. The local watershed supports diverse aquatic ecosystems, including fish species such as brown trout and grayling. The plant's operations help maintain water quality in this ecologically sensitive river system.