Varazdin Wastewater Treatment Plant, Trnovec, Croatia

The Varazdin wastewater treatment plant is located in Trnovec, near the city of Varazdin in northern Croatia. It serves the surrounding agglomeration as a key municipal facility, with a designed capacity of 140,000 cubic meters per day, indicating it handles a substantial population equivalent. The plant provides secondary treatment, which is the standard biological treatment stage required under the EU Urban Waste Water Treatment Directive (91/271/EEC) for agglomerations of this scale. This level of treatment removes organic matter and suspended solids, reducing pollution loads before discharge. Treated effluent from the plant is discharged into the Drava River, a major tributary of the Danube. The Drava flows eastward through Croatia and into the Danube, ultimately reaching the Black Sea. The plant plays a crucial role in protecting the Drava's water quality and the downstream ecosystems it supports.

The plant discharges into the Drava River, which flows into the Danube and then the Black Sea. The Drava is an ecologically significant river supporting diverse aquatic life and serving as a migratory corridor for fish. The plant's secondary treatment helps reduce nutrient and organic loads, mitigating eutrophication risks in downstream waters.