PROGRAMME

Throughout history, wastewater management and treatment have been critical sectors of society and civilization. The last century's rising urbanization and industrialization increased the volume of municipal wastewater generation globally, and by 2050, 62% of the global population is predicted to reside in cities (Voukkali and Zorpas, 2022). The global wastewater treatment industry is anticipated to reach 490 billion USD by 2029, up from 281 billion USD in 2021 (Statista, 2022). In recent years, efforts to enhance wastewater treatment plant performance have evolved from generating acceptable effluent to assuring sustainability and economic viability. The current work aims to determine the environmental footprint of an activated sludge process that includes appropriate measures for the energy valorization of primary solids received from raw wastewater, as well as the additional benefits expected by implementing these measures in comparison to a conventional system. Towards that objective, the assessment of the environmental impact was carried out by utilizing the Life Cycle Assessment (LCA) approach. Throughout the life cycle of a product, service or entire set of processes, from raw materials to production, use, end-of-life treatment, recycling, and final disposal (i.e., cradle-to-grave), LCA is a standard procedure that addresses the environmental aspects and potential environmental impacts of processes or services (i.e. use of resources, carbon footprint, eutrophication etc.). Over the past thirty years, it has rapidly advanced from a basic energy analysis to a full life cycle impact assessment, life cycle costing, and social-LCA, and most recently to a more thorough life cycle sustainability analysis, which broadens the scope of the conventional environmental evaluation (Dimitra C Banti et al., 2020; Tsangas et al., 2020). It is directly applicable to the creation and enhancement of products, strategic planning, the assessment of environmental performance, the formulation of public policy, and other activities. LCA has been used in the past for the improvement of the environmental performance of specific production processes and services (Dimitra C Banti et al., 2020; Hashemi et al., 2022; Litskas et al., 2022), the monitoring and assessment of CO2 emissions (Iannone, R.; Miranda, S.; Riemma, S.; De Marco, 2016), the estimation of the impact of climate change on wastewater treatment as well as strategic development planning in different sectors of interest (Dimitra C. Banti et al., 2020; Christoforou et al., 2016). Therefore, LCA was used for the representative system of an activated sludge unit, including pretreatment and primary treatment stages consisting in coarse screens and grit removal, secondary treatment involving an aeration tank followed by sedimentation, while anaerobic digestion is applied for the stabilization of excess sludge. The main environmental impact categories chosen for analysis for the three scenarios employed were the eutrophication potential (EP) (kg PO4-eq_FU−1), the acidification potential (AP) (kg SO2-eq_FU−1), the global warming potential (GWP) (kg CO2-eq_FU-1) over a 100 years period, the ozone depletion potential (ODP) (kg CFC-11-eq_FU−1) and the photochemical ozone creation potential (POCP) (kg C2H4-eq_FU−1). Throughout the life cycle of a product, service or entire set of processes, from raw materials to production, use, end-of-life treatment, recycling, and final disposal (i.e., cradle-to-grave), LCA is a standard procedure that addresses the environmental aspects and potential environmental impacts of processes or services (i.e. use of resources, carbon footprint, eutrophication etc.). Over the past thirty years, it has rapidly advanced from a basic energy analysis to a full life cycle impact assessment, life cycle costing, and social-LCA, and most recently to a more thorough life cycle sustainability analysis, which broadens the scope of the conventional environmental evaluation (Dimitra C Banti et al., 2020; Tsangas et al., 2020). It is directly applicable to the creation and enhancement of products, strategic planning, the assessment of environmental performance, the formulation of public policy, and other activities. LCA has been used in the past for the improvement of the environmental performance of specific production processes and services (Dimitra C Banti et al., 2020; Hashemi et al., 2022; Litskas et al., 2022), the monitoring and assessment of CO2 emissions (Iannone, R.; Miranda, S.; Riemma, S.; De Marco, 2016), the estimation of the impact of climate change on wastewater treatment as well as strategic development planning in different sectors of interest (Dimitra C. Banti et al., 2020; Christoforou et al., 2016). Therefore, LCA was used for the representative system of an activated sludge unit, including pretreatment and primary treatment stages consisting in coarse screens and grit removal, secondary treatment involving an aeration tank followed by sedimentation, while anaerobic digestion is applied for the stabilization of excess sludge. The main environmental impact categories chosen for analysis for the three scenarios employed were the eutrophication potential (EP) (kg PO4-eq_FU−1), the acidification potential (AP) (kg SO2-eq_FU−1), the global warming potential (GWP) (kg CO2-eq_FU-1) over a 100 years period, the ozone depletion potential (ODP) (kg CFC-11-eq_FU−1) and the photochemical ozone creation potential (POCP) (kg C2H4-eq_FU−1).