Major water and wastewater infrastructure upgrade for Kaštela-Trogir, Croatia

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The project has three parts: water supply, wastewater collection, and wastewater treatment.For the former, the project will construct 59.86 km of new water supply network, reconstruct 65.4 km of existing water supply network, build four pumping stations and two 500 m3 water reservoirs. Preparatory work for installing 1 640 new water supply connections will be done.The wastewater component will involve building 215 km of new sewerage network and reconstructing 4.04 km of the existing network. Other works include constructing  6.03 km of pressure pipeline, 0.64 km of overflow structures and  13 pumping stations.Finally, the wastewater treatment plant Divulje will be upgraded from a capacity of 40 000 population equivalent (p.e.) to 100 000 p.e.  At present it only does mechanical, or primary, treatment of sewage, meaning that it fails to meet treatment requirements set out in national and EU legislation. The project will upgrade it to allow for biological treatment. In addition, a 25 000 p.e. capacity wastewater treatment plant will be constructed on Čiovo island and will allow for biological treatment of sewage, too.Both plants will reduce the water content in the resultant sludge by up to one third. It will then be channelled to the Stupe waste water treatment plant, in Split, where a system to dry the sludge will be built.The agglomeration covered by the project has a total population of around 63 000 inhabitants and 3.9 million overnight stays from tourists annually. It includes the City of Kaštela (which includes the towns of Kaštel Sućurac, Kaštel Gomilica, Kaštel Kambelovac, Kaštel Lukšić, Kaštel Stari, Kaštel Novi and Kaštel Štafilić); the City of Trogir (Trogir, Divulje, Plano, Mastrinka and Arbanija on the north-eastern part of Čiovo island) and the coastal part of the Seget municipality (Seget Donji and Seget Vranjica); the Okrug municipality on Čiovo (Okrug Gornji) and Slatine on the north-eastern part of Čiovo, which administratively belongs to the City of Split.Reducing water lossAt present, 42 % of the drinking water from the public supply system is lost. The project intends to reduce this to 36 %. A total of 87 % of the agglomeration’s population is currently connected to the public water supply network. The project intends to increase this to 99 % by providing water to 7 700 more inhabitants – residents living in the northern parts of Kaštela. This equates to 2 548 new connections.More wastewater connectionsThe connection rate to the sewerage system in the agglomeration is 45 % (28 350 people). The project aims to increase this to 97 % with an extra 8 613 connections, to benefit 32 477 additional inhabitants. The aim is to push the connection rate up to 98 % by 2028. The upgrade of the Divulje and the construction of the Čiovo wastewater treatment plants will ensure there is sufficient capacity to handle the new connections.A high volume of storm water and sea water – in the coastal areas – gets into the existing sewage collection system. A project financed by Croatian water utility ViK Split is being implemented in parallel with the project to reduce the amount of rain and seawater that gets into the sewerage system, as this negatively affects the biological treatment of sewage.Currently, some of the untreated sewage is discharged directly into the sea. By preventing this, the project will ensure compliance with the EU’s Water Framework and Bathing Water directives.The sewerage system and the wastewater treatment plants will be connected to one supervisory control and data acquisition system. A geographic information system will be used to enable better planning of maintenance and reconstruction of the networks.Total investment and EU fundingTotal investment for the project “Improvement of the water communal infrastructure – Kaštela-Trogir agglomeration” is EUR 189 314 243, with the EU’s Cohesion Fund contributing EUR 105 687 206 through the “Competitiveness and Cohesion” Operational Programme for the 2014-2020 programming period. The investment falls under the priority “Environmental Protection and Sustainability of Resources”.