The Concept of Circular Economy in Wastewater Management along the Slovenian Coast

The current concept of wastewater management and treatment in the European Union complies with the requirements of Directive 91/271/EEC on urban wastewater treatment, established in 1991 with a primary focus on limiting excessive organic carbon, nitrogen, and phosphorus in treated water. At that time, the reuse of treated water was not considered. Not surprisingly, attempts were made to remove as much carbon as possible in the form of CO2. The removal of nitrogen compounds by denitrification results in the formation of N2, which is then released into the atmosphere. When removing phosphorus compounds, the aim is to incorporate as much phosphorus as possible from the water into the sludge of the wastewater. This also ignores the fact that treated water can be a very valuable resource. In regions, particularly those with advanced agriculture, where wastewater from treatment plants pollutes the environment, adopting an appropriate approach could address summer water shortages, reduce CO2 emissions into the air, and reduce reliance on artificial fertilisers. The key prerequisite for any use of treated wastewater is adequate microbiological purification and the absence of hazardous substances. This paper analyses the effluent characteristics of some examples of wastewater treatment plants along the Slovenian Adriatic coast, and evaluates the possibilities of reusing the treated water. The results are correlated with the wastewater treatment efficiency data from the town of Rovinj (Croatia), which provides the reuse of treated wastewater for municipal purposes.