Background Two of the main environmental problems caused by water pollution are eutrophication (excessive nutrients) and hypoxia (oxygen starvation), which result from nutrient pollution of water bodies. They promote excessive plant growth and decay, favouring certain weedy species, and cause severe reductions in water quality. The EU Water Framework Directive (WFD) requires EU Member States to take measures to combat such pollution, but implementation is lagging in some countries. Many southern European countries have not taken sufficient measures to achieve good water status in their water bodies. In the countries of southern Europe with warm climates, and in non-EU countries with similar climates, conventional waste water treatment systems could be implemented and/or upgraded to tackle water pollution problems. However, these conventional systems are currently characterised by high energy consumption. Objectives The CELSIUS project will develop and demonstrate a low energy consumption waste water treatment system for warm climates. The system combines two innovative treatment processes: an anaerobic membrane bioreactor (AnMBR) and partial nitrification/Anammox (anaerobic ammonium oxidation) treatment. The first process removes organic matter, while the second eliminates nitrogen. The project will assess the effectiveness of a pilot plant that will be suitable for treatment of waste water from warm-climate areas where energy resources are low or access to energy is limited. The project's specific objectives are: 1. To make organic matter removal more energy efficient through the optimisation of the AnMBR; 2. To make nitrogen removal more energy efficient through the development of advanced control systems and operational strategies for the partial nitrification/Anammox process; 3. To optimise the system as a whole in order to contribute to the removal of organic matter and nitrogen from the waste water; and 4. To evaluate the feasibility of full-scale deployment of the optimised system in warm-climate areas such as South America, India, Africa and EU Mediterranean basin countries (Spain, Portugal, Italy and Greece). Expected results: A 60% reduction in the energy consumed in the organic matter removal process, compared to conventional treatment; A 60% reduction in the energy consumed for nitrogen removal, compared to conventional treatment. This would also result in lower greenhouse gas emissions from lower energy consumption. The carbon dioxide saving is estimated to be 0.163kg/CO2 per cubic metre of treated waste water; Elimination of 90% of the organic matter and 90% of the nitrogen from incoming waste water, resulting in a significant impact in terms of prevention of eutrophication and hypoxia in the areas where the treatment system is implemented; and A full technical evaluation of the system will be carried out, and an economic analysis will be done taking into account the capital and operational costs of the technology. Following on from this, a list of locations where the system could be implemented successfully will be produced.