Background Currently, urban wastewater treatment plants (WWTPs) consume at least 8-15 kilowatt hours/inhabitant/year of energy in order to meet legal requirements on discharges of organic matter, nitrogen and phosphorus. This means a significant economic cost and is associated with substantial greenhouse gas emissions. Objectives The SAVING-E project will demonstrate how urban WWTPs can be redesigned so that they become energy producers rather than energy consumers. The performance of the redesigned WWTP will compare favourably to current standards. SAVING-E technology works by using most of the organic matter that enters the WWTP for biogas production. Waste water passes through a biological treatment step with low oxygen consumption and high biomass production. The biomass produced in this step has very favourable methane production potential, greater than that achieved by the current generation of urban WWTPs. In a second step, SAVING-E technology biologically removes nitrogen from waste water without the need for organic matter. SAVING-E uses the autotrophic biological nitrogen removal (BNR) process for this, but with a novel two-step approach. This consists of two reactors: an aerobic partial nitritation reactor followed by an Anammox (anaerobic ammonium oxidation) reactor. The application of autotrophic BNR significantly cuts aeration costs compared with current urban WWTPs. The novel two-step approach to autotrophic BNR represents an improvement compared to one-step autotrophic BNR because it can work stably at very low temperatures (10 ºC). The SAVING-E technology will be tested at pilot scale. The pilot plant will be installed in the Rubí (Barcelona) urban WWTP. The pilot plant will operate for 30 months at different temperatures, including 10 ºC to demonstrate the stability of the process. A technical and economic analysis of the impact of the implementation of the technology in different types of urban WWTPs will also be carried out. Expected results: The project will demonstrate that the use of SAVING-E technology compared to current WWTP technologies will result in: (i) energy savings, (ii) reduced carbon dioxide emissions, and (iii) reduced operational costs. Compared to current WWTP technologies, SAVING-E will generate the following benefits: A 50% increase in biogas production; A 10% reduction of nitrogen discharges; Some 30% energy savings in the nitrogen removal process; Some 40% energy savings in the overall treatment process; and A 20% reduction in greenhouse gas emissions.