Background Urban water activities ensure both a reliable supply of drinking water and compliance with regulations for discharging water into water bodies. However, the processes involved in the urban water cycle also have environmental impacts, as they consume electricity, use chemicals and generate waste. There is, therefore, a need to improve understanding of the existing balance between environmental and health benefits of different urban water cycle activities and their environmental impacts. A life-cycle approach is needed to ensure that the overall environmental cost-benefits of urban water activities is positive. However, it is not sufficient to consider just one environmental indicator, such as the carbon footprint. Environmental performance assessments should include all significant impacts throughout the urban water system. This knowledge can help decision-makers assess, for example, whether it is worth improving water quality at the expense of increasing the consumption of energy and chemicals. Objectives The main objective of the AQUAENVEC project was to provide decision-making tools to optimise eco-efficiency in the urban water cycle, through environmental and economic life-cycle analysis. The project aimed to provide for more sustainable management of the urban water cycle, by assessing the major environmental impacts of urban water activities, including global warming, water toxicity, eutrophication, acidification, and depletion of resources. It aimed to assess the potential for reducing these impacts, and also to assess the economic impacts of the different operations, in terms of operating costs, capital costs and other indirect costs throughout the water life cycle, and to identify possible cost savings. Results The AQUAENVEC project developed decision-making tools for optimising the urban water cycle to achieve environmental and economic benefits, using Life Cycle Analysis (LCA) and Life Cycle Cost analysis (LCC). In the first phase of the project, the LCA/LCC methodology was defined (e.g. functional units and boundaries) for each stage of the urban water cycle. This was published as the ‘Methodology guidelines for urban water cycle LCA and LCC assessment’, the basis document for the correct and effective implementation of the subsequent project actions. The project team collected data and information to carry out complete and rigorous LCA and LCC from varied sources, including the technical literature, CETaqua and other databases, information provided directly by stakeholders and water companies, and the project’s questionnaire. Two case studies, in Catalonia and Galicia, were carried out to test the LCA/LCC methodology under different conditions (climate, water quality and water use patterns), so increasing its representativeness for small and medium-sized cities of the Mediterranean and Atlantic Spanish coast. The project team created a database for data gathered from the case studies, covering the construction, operation and maintenance phases of water facilities. This sampling data was integrated with the other sources of data. The project conducted LCA for all stages of the urban water cycle, and published their reviews and recommendations for best practice to reduce environmental impacts in a series of documents. A detailed LCA of the different water activities (water extraction and treatment, transport and distribution, sewer networks and waste water treatment) was carried out separately. The LCA for water extraction and drinking water treatment looked at around 30 types of treatment and quality parameters. The project team concluding that more use of renewable energy, and the use of alternative chemicals to substitute for FeCl3, could significantly reduce environmental impacts. The LCA for transport, distribution and sewage assessed factors such as construction activities, materials used in pipes and other infrastructure, and maintenance; the project found that the main environmental impact was associated with the construction phase of the supply and sewer networks (whereas in the treatment plant, the main impact was linked to plant operation). The LCA for wastewater treatment inventoried the chemical compounds present and their toxicity. The main group of chemical compounds with possible toxicity in wastewater were pharmaceutical products. The project’s LCC identified the main cost drivers and cost items for each urban water cycle stage, with cost profiles of the different processes involved. The results showed that, in both case studies, networks (particularly construction costs) represented a higher economic impact than treatment plants in terms of life cycle costs. A literature study showed that, although plenty of information exists for single stages, there are few previous studies concerning the costs of the entire water cycle – this is one of the project’s main innovative aspects. The project produced an in-depth review of the state-of-the-art regarding methodologies for analysing the cost of the different water cycle stages, and a publication on LCC for the integrated urban water cycle with recommendations for best practices. The project integrated all its results, through a common methodology, and defined a set of eco-efficiency indicators for drinking water treatment plants and supply networks. Environmental impact indicators were quantified through LCA, relating to global warming potential, eutrophication potential, ozone layer depletion potential and cumulative energy demand; while LCC indicators covered construction, operation and maintenance costs. The project documented its eco-efficiency indicators and also published guidelines on best practices to improve eco-efficiency throughout the urban water cycle. The project’s eco-indicators and other outputs were incorporated into the user-friendly AQUAENVEC tool, for use by non-experts to monitor water parameters. This tool enables policy-makers, and public and private water managers, to make better decisions and produce overall eco-efficiency gains. This supports the implementation of the Water Framework Directive, the Priority Substances Directive and other European initiatives and legislation. Environmental benefits derive from the LCA approach providing a broader perspective, by considering controllable processes, raw materials, supply chains, waste disposal and re-use possibilities. This permits a better understanding of the balance between environmental benefits of urban water activities (from extraction to wastewater treatment) and their environmental burdens. Optimisation of processes can bring economic benefits, from improved infrastructure construction to day-to-day cost-effective water management using the AQUAENVEC tool. From the social point of view, the project also helped inform local communities about several issues relating to water in general (e.g. consumption behaviour, savings and water quality), and the urban water cycle in particular. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).