Background Small wastewater plants can present problems due to poor performance arising from inadequate design, treatment and control; uncontrolled discharge of pollutants into public water systems; lack of training for operators; unmanned nocturnal plant operations; plant locations in inappropriate sites; and lack of information for water consumers. However, demand for good wastewater treatment technologies is high due to increased environmental awareness and the need to comply with EU legislation. Objectives The aims of the project included: Analysis of existing technology and systems in wastewater treatment plants (WWTP) Development of a WWTP auditing models to improve efficiency Demonstration of the advantages of using renewable wind energy in WWTPs The use of best available technologies for process control and equipment operation Implementation of an integrated online monitoring system for better performance and increased rapid response to emergency situations Development of a Lab Pilot Plan (8m³/h) connected with the Sintra municipal WWTP online network. Results The WWTreat LIFE project demonstrated a new perspective for wastewater treatment in small communities up to 35 000 inhabitants. It was based on the development and implementation of an integrated online monitoring system in three Portuguese WWTP, located in the area of Sintra (Magoito, Almoçageme and Vila Verde). The aim was to achieve the best performance and reliability of treatment and equipment and, if applicable, to increase the emergency responses, avoiding pollution incidents in small communities. Combining existing technologies in an integrated control system was an important solution in terms of increasing treatment efficiency and economic viability, saving water, diminishing pollution, recovering water and sludge. The project built a portable laboratory pilot plant, connected online to the full-scale WWTPs in Sintra. It records and controls all critical parameters of the process and equipment operation and generates alarms when abnormality occurs. These online alarms result in a quick response of checking and testing the process, including collecting wastewater samples to be analysed in the lab plant (in order to later on correct/adjust the treatment process) and repairing or changing broken, defective or inadequate parts and systems. The portable Lab Plant WWTP system is based on the activated sludge biodegradation technology. The remote control and monitoring system allows the monitoring of important parameters of effluent wastewater and of the treated effluent. It also interacts (locally and remotely) with the WWTP components in order to change operational parameters. The online system adopted BAT's for process control and equipment operation, including efficiency monitoring, predictive maintenance, failure diagnoses and optimising of equipment lifecycle decisions. The project also developed a specific methodology for WWTPs auditing. It demonstrated the advantages of clean and renewable energy uses such as small wind turbines in WWTP, as well as the energy valorisation of sewage sludge by gasification, depending on the plant site and energy source. The implementation of the integrated online monitoring system reduces operation labour costs, optimises maintenance action and cuts maintenance costs. For example, the project’s cost-benefit studies on the Magoito and Almoçageme WWTPs show that significant savings could be made annually by using the system.