As part of the project, nearly 2 kilometres of sewers collecting the wastewater from homes or businesses in the settlement of Prnek will be laid, the wastewater treatment plant Rogaška Slatina will be expanded to accommodate an additional basin and to ensure the deployment of waste dehydration system to optimize performance and drive improvements in effluent quality.

During periods of heavy rainfall, the wastewater volume in the existing combined sewer system can exceed the capacity of the sewer system or treatment plant. For this reason, combined sewer system overflows occasionally and discharges excess wastewater directly to the nearby Sotla River.

The planned wastewater treatment plant expansion and the improvements made to its operation will contribute to the revitalization of the nearby Vonarsko jezero lake and its surroundings; the lake was completely emptied a couple of years ago because of eutrophication.