Background Across the EU, there are around 16 000 waste water treatment plants (WWTPs). Treatment of waste water is necessary to prevent pollution from being discharged into water courses. It can also provide water that is clean enough for re-use in certain contexts, which can be particularly useful in areas suffering from water stress. However, re-use of treated water is currently restricted by the fact that it is often more expensive than drinking water. This is largely due to the high energetic demand of WWTPs. WWTPs in the EU consume around 10 000 GWh/year of mains electricity. Furthermore, the volume of waste water being treated in the EU is increasing by around 7% each year. As well as the financial cost, this energy consumption creates an additional environmental burden. Mains energy in Europe is typically produced from the burning of fossil fuels, with its associated environmental costs. Energy consumption from WWTPs creates emissions of more than 27 M tonnes/year of CO2 in the EU. In Spain alone, WWTPs consume 2 213 GWh/year, emitting more than 6 M tonnes/year of CO2. Objectives The LIFE RENEWAT project aims to demonstrate the use of sustainable technologies for reducing the mains energy demand of Waste Water Treatment Plants (WWTPs). The project thus seeks to reduce both greenhouse gas (GHG) emissions associated with the treatment of waste water and the costs of water treatment, making treated water a more viable option for a range of uses. Specifically, RENEWAT plans to demonstrate an intelligent system for applying a renewable energy mix in WWTPs. The project will follow three main stages, involving: 1. Adapting the WWTP process to a new energy input from a renewable mix, including, small-scale (less than 10MW) photovoltaic (PV) and wind energy sources; 2. Using the renewable sources (PV and wind) in the WWTP; 3. Developing an intelligent system capable of managing the input of energy from the different sources. The intelligent system will discriminate between the energy input sources – PV, wind or grid - aiming to provide the optimum energy mix, depending on the environmental and weather conditions. It will also regulate the overall energy input according to the precise demand of the WWTP at every stage of the process. The project thus expects to reduce the consumption of electricity from the grid as much as possible. This will reduce the carbon emissions associated with wastewater treatment. It will also reduce the price of treated water and represent a first step in terms of boosting the re-use of treated water, for example in agricultural and landscape irrigation. Expected results: An intelligent system allowing for the optimal use of renewable energy sources in WWTPs; A 30% decrease in consumption of electricity from the grid by WWTPs; A 24% reduction in the cost of treated water - from 0.4 €/m3 to 0.3 €/m3; A reduced carbon footprint of WWTPs, by about 45 tonnes CO2/yr for every 100 kW obtained from renewable sources; The potential to apply the intelligent system in 99% of the EU’s WWTPs, saving millions of tonnes of CO2 emissions and promoting the re-use of treated water.