Kastl Wastewater Treatment Plant, Bavaria, Germany

The Kastl wastewater treatment plant is located in the municipality of Kastl, in the Landkreis Amberg-Sulzbach district of Bavaria, Germany. It served a population of 1,792 and is now closed. The plant was designed with a capacity of 4,500 cubic meters per day and discharged an average volume of 453.51 cubic meters per day. As a secondary treatment facility, the plant provided biological treatment to reduce organic matter and suspended solids. Under the EU Urban Waste Water Treatment Directive (91/271/EEC), secondary treatment is the standard requirement for inland freshwater discharges. The plant's closure may reflect consolidation of wastewater services in the region. The treated effluent was discharged to a local watercourse, which ultimately drains into the Danube River basin via the Vils and Naab rivers. The Danube flows into the Black Sea, making this plant part of a large transboundary watershed. The surrounding area is rural with agricultural land use.

The plant's discharge entered a small tributary of the Vils River, which flows into the Naab and then the Danube River. The Danube is one of Europe's major rivers, supporting diverse aquatic ecosystems and providing water for millions of people. The downstream environment includes ecologically sensitive floodplains and wetlands that rely on good water quality. The plant's secondary treatment helped protect these habitats from excessive nutrient and organic pollution.