Background At present, around 25% of the total amount of municipal wastewater in Croatia is treated (mostly through mechanical treatment 76%). About 18% undergoes secondary treatment, which represents only around 4.4% of the total amount of municipal wastewater. Some industrial entities, connected to public sewerage systems, possess plants for preliminary treatment of wastewater, which should reduce the quality of industrial water to the quality level of municipal wastewater before treatment. Unfortunately, some wastewater is still being discharged into natural recipients without undergoing necessary treatment. A systematic programme for monitoring the quality of surface water and groundwater has been set up and is supervised by Croatian Waters, the national water management agency. The programme is implemented by 15 authorised laboratories at 454 measuring stations, with the involvement of the Central Water Management Laboratory of Croatian Waters. Objectives The CROWATER project aimed to complete national water and wastewater management procedures by supporting Croatian Waters in creating a new laboratory for analysis of biodegradable components in wastewater. Project outputs aimed to contribute to the national water protection strategy and to the country's ultimate compliance with the EU Water Framework Directive (2000/60/EC). Results The CROWATER project presented Best Available Technologies (BATs) to plant operators and managers in several hot-spot sites where high pollution risks existed from inappropriate waste water treatment (WWT) systems. BATs were proposed as solutions to problems noted in the operation of the WWT plants. In total, 19 WWT plant were visited (13 communal and 6 industrial) during the project. Samples were taken and analysed and detailed recommendations were prepared for seven of these plants. The remaining 12 sites were not considered suitable for further inclusion in the LIFE project since they were not fully operational. Conclusions from the visits and results of the analyses showed that the existing Croatian WWT system could be optimised and this would require upgrading of facilities. Upgrading was considered to be dependent on the availability of financial resources, as well as the capacity of on-site expertise for managing the upgraded WWT plants. Knowledge gained during the LIFE project will be used to help justify new WWT investments and the project’s methodology offers scope for strengthening a wider range of WWT plant capacities in Croatia. Further information on the project can be found in the project's layman report (see "Read more" section).