Construction begins on Croatia’s second largest wastewater treatment plant near Split

(Photo: Grad Split)

SPLIT, 29 July 2026 – Construction has officially begun on the Stupe Wastewater Treatment Plant (UPOV Stupe), one of Croatia’s largest environmental infrastructure projects and a key part of the Split–Solin Water and Wastewater Infrastructure Improvement Project.

The design and expansion contract is worth €99 million (including VAT), while the wider Split–Solin project has a total value of more than €321 million.

Once completed, Stupe will become Croatia’s second largest wastewater treatment plant, with the capacity to serve 275,000 population equivalents, covering residents as well as seasonal tourism and industry.

The upgraded facility will form the central hub of a unified wastewater system linking Split, including the eastern neighbourhoods of Žrnovnica, Korešnica, Stobreč and Kamen, together with Solin, Klis, Podstrana and Dugopolje.

(Photo: Grad Split)

A major milestone is that wastewater from the area will, for the first time, undergo secondary biological treatment before being discharged into the Adriatic Sea, significantly improving environmental protection.

Construction is expected to take 28 months, while the overall contract, including testing and obtaining operating permits, is scheduled to last 43 months.

The project also includes more than 125 kilometres of new sewer collectors, 65 kilometres of new water supply and sewer pipelines, 32 pumping stations, retention basins and a new submarine outfall into the Brač Channel.

(Photo: Grad Split)

In addition to the treatment facility, new infrastructure will include sludge treatment and drying systems, a new administration building and a cogeneration plant that will generate part of the facility’s electricity and heat from biogas produced during the treatment process.

Officials said the project will help Croatia meet European Union environmental standards while improving the quality of coastal waters and drinking water supplies.

(Photo: Grad Split)

The wider investment is also expected to increase public sewer network coverage in the Split area from 86% to 97%, allowing the gradual removal of around 8,500 septic tanks.

Around 4,000 residents will gain new water supply connections as part of the project.

(Photo: Grad Split)

The second phase of the Split–Solin project has eligible costs of €243.1 million, with 68.01% (€165.4 million) financed through the EU Cohesion Fund, while the remaining 31.99% is funded from Croatian national sources.

(Photo: Grad Split)

Authorities say the investment will provide long-term benefits through cleaner coastal waters, reduced carbon emissions, improved wastewater management and stronger protection of the Adriatic marine environment.