Background A wide variety of industrial sectors need to develop long-term policies around their energy consumption and climate change impacts. Particular issues to be addressed include energy management, sustainable sources of renewable energy, and management of greenhouse gas (GHG) emissions. Wastewater treatment processes have high energy consumption. Both the aerobic treatment processes and agricultural applications of sludge from wastewater treatment are significant sources of GHG emissions. Furthermore, the number of wastewater treatment facilities in Europe is increasing to meet population growth and quality standards. This means there is a need for improved management tools, technological solutions and operational innovations that encompass both the energy balance and the associated carbon footprint of these facilities. Objectives The objective of the WW4ENVIRONMENT project was to implement an optimising tool for the management of wastewater treatment facilities, using operational data to determine and minimise energy consumption, while minimising their carbon footprints and residual sludge production. It hoped to achieve EU-defined objectives on energy efficiency and reductions in the environmental impact of wastewater facilities. To achieve this, methodology, procedures and models were designed at the laboratory scale and then implemented as a full-scale demonstration project at the Beirolas wastewater treatment facility, operated by project partner SIMTEJO, in the Lisbon-Loures industrial area. Results The WW4ENVIRONMENT project demonstrated the implementation of a tool to optimise the management of a wastewater treatment plant (WWTP). The project’s methodologies, procedures and models were designed at lab-scale and implemented at the Beirolas WWTP, which treats domestic (70%) and industrial (30%) wastewater, and serves 215 000 equivalent-inhabitants and treats 54 500 m3 of wastewater per day. The WWTP management optimisation tool simulated different scenarios using a model, with the aim of decreasing the consumption of energy in the treatment process through the exploration of different operating strategies. Improvements made to software by the project represented a step forward in terms of simulation models in this area. The model fed on the project database, which combined historical data from Beirolas WWTP with data from the monitoring programme that was conducted throughout the project. The findings showed the potential to reduce energy costs by reducing oxygen supply by 20%, which still generated an effluent fulfilling the legal requirements. Associated beneficiary INETI investigated the eco-toxicity of the WWTP process, using frequent samples of wastewater, sludge and sediments, with a wide range of tests involving up to 93 parameters. The eco-toxicological approach was demonstrated in the project as a complement to the physico-chemical approach to identify hazardous discharge situations. These contributed to an assessment of the effectiveness of the treatment process in reducing toxicity, and helped protect the biological treatment from toxic influents. The sludge has an economic use in fertilising crops. Procedures were developed to assess the carbon footprint of the WWTP, included the quantification of greenhouse gases, namely, carbon dioxide, methane and nitrous oxide, and emissions from biological treatment, sludge treatment and electricity consumption. This data served to improve treatment plant performance in terms of environmental impact and energy efficiency. Climate change mitigation strategies can be defined from the emissions' profile of the treatment facility, while the carbon footprint assessment can also be used to understand the contribution of WWTP for the global carbon budget. WW4ENVIRONMENT was the first project in Portugal to consider wastewater treatment in the context of climate change. The new paradigm was to change the way organic matter from wastewater treatment processes is handled, turning these activities into sustainable and optimised energy production processes. The integration of already know processes (e.g. co-digestion in anaerobic reactors) into an optimising model framework designed to match the demands of a wastewater treatment facility is an innovative approach that suits both energy sectors and climate change mitigation objectives. Biogas is a potentially valuable by-product of wastewater treatment. Methodology and procedures for the implementation of the WWTP co-digestion regime in anaerobic digesters were designed to reuse the grease removed from pre-treatment in the treatment facility. The co-digestion regime tested with 90% (v/v) of sludge from the facility and 10% (v/v) of grease from the pre-treatment represented an increase of 25% in specific methane production and an increase of up to 78% regarding the total production of biogas. Project methodologies, procedures and models can be implemented in other WWTPs around Europe. To facilitate this, a range of guidelines and handbooks were produced by the WW4ENVIRONMENT partners, to provide the necessary information, for example, regarding techniques for the optimisation of the anaerobic digestion process, the methodology for assessing the carbon footprint of WWTPs, and eco-toxicological survey methodologies. The project has taken into account European concerns regarding energy management, sustainable sources of renewable energy, management of GHG emissions by carbon footprint assessment and reductions in environmental costs. In this respect, it has helped in the implementation of the Urban Waste Water Treatment Directive (91/271/CEE), the Water Framework Directive (2000/60/EC), and Directive 2008/105/EC on environmental quality standards in the field of water policy. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).