The EU4Green initiative continues strengthening the capacity of wastewater operators across Western Balkans to improve effluent quality and protect regional water resources.

The training for urban wastewater treatment plant (UWWTP) operators held in Belgrade on 16–17 April 2026 attracted strong interest from the UWWTP operator community across the Western Balkans, bringing together nearly 60 operators and experts on site and online—more than twice the attendance of the first online session in June 2024. The two‑day program focused on strengthening core competencies needed for operation of activated sludge process and compliance with effluent standards. Sessions covered the fundamentals of activated sludge microbiology, practical process control, and microscopic assessment of activated sludge brought by participants. Special attention was given as well to the impact of industrial discharges on operation of municipal wastewater treatment plants, including typical operational challenges and available mitigation strategies. The agenda featured case studies from UWWTP Leskovac in Serbia and the UWWTP Welser Haide plant in Austria, offering real‑world insights into troubleshooting and process optimization.

Highlights of the two-day program included:

• Reviewing essential control variables that influence activated sludge operation

• Practical exercises and microscopy helped participants better understand activated sludge condition and its link to plant performance.
• Discharges of industrial wastewaters and its impacts on UWWTP operation, including challenges from variable influent quality and strategies for maintaining stable biological treatment.
• Case studies from Serbia and Austria provided real‑world examples of troubleshooting and optimizing processes on UWWTP.