Background Effective treatment of wastewater, that guards against the pollution of bodies of water and the phenomenon of eutrophication, is a worldwide challenge. The extent of the challenge is illustrated by the high number of bathing waters in EU countries that do not comply with EU regulations. Development of new and cost-effective processes is necessary to improve existing wastewater treatment systems. Objectives The ENREM project aimed to carry out the first full-scale assessment of an innovative wastewater treatment process that combines enhanced biological phosphorous and nitrogen removal with post-denitrification together with a membrane bioreactor. This combination would improve removal of nutrients and pollutants in comparison with conventional plant performance. A demonstration plant using this process would be built, collecting local area sewage in the proximity of Berlin without any industrial or run-off water. Collected sewage would be treated so that it meets EU sensitive area and bathing water regulations. Results The ENREM project implemented a wastewater treatment process based on membrane bioreactor technology for biological advanced nutrients removal. The process is an economical solution for remote and small wastewater schemes where high treatment performances are required for bathing areas and areas of sensitivity (disinfection and low nutrients concentration in the treated water). The technology of membrane bioreactor offers the following advantages over conventional systems: Reliable and improved treatment quality, including complete disinfection. Possibility of remote/central control of a decentralised system. Compactness and therefore reduced nuisance levels (odours, visual disturbance etc.). The biological process combines enhanced biological phosphorus removal (EBPR) through the presence of an anaerobic zone and advanced nutrients removal with post-denitrification. The previous research project identified this process as most appropriate for advanced nutrients removal in small to medium-size MBR plants as it saves on equipment and energy (sludge recirculation pumps) compared with conventional processes. The project validated the biological process and design/operation criteria, achieving the expected treatment targets of up to 99% phosphorus elimination and 90% nitrogen elimination. The ENREM project showed also that a combination of a separated collection sewer together with a puffer reactor enables the optimisation of the size of the reactor volume and membrane surface. The use of a low-pressure sewer is seen as an additional advantage: first it ensures that the wastewater is devoid of storm water; second, it may enhance the presence of volatile fatty acids required for the biological nutrients removal through the one to two-day residence time in the shafts and sewer. While the project demonstrated the process’ technically viability, a cost analysis highlighted that the operation costs are high – 2.88 €/m3 (without depreciation of infrastructure) – and can be justified only in case of advanced treatment requirements. The costs are mainly attributable to the power consumption, the servicing contract and the analysis costs. Real full-scale costs are lower as the entire small wastewater treatment plant costs only €382 000, or approx. € 1500/p.e. A scale up to an MBR-plant for 1000 residents providing the same standards (with regard to target parameters, monitoring technology and equipment) would give total costs of €1 059 000 or specific costs of approx. € 1 000 /p.e. Further information on the project can be found in the project's layman report (see "Read more" section).