Wastewater treatment plant decision makers face stricter regulations regarding human health protection, environmental preservation, and emissions reduction, meaning they must improve process sustainability and circularity, whilst maintaining economic performance. This creates complex multi-objective problems when operating and selecting technologies to meet these demands, resulting in the development of many decision support systems for the water sector. European Commission publications highlight their ambition for greater levels of sustainability, circularity, and environmental and human health protection, which decision support system implementation should align with to be successful in this region. Following the review of 57 wastewater treatment plant decision support systems, the main function of multi-criteria decision-making tools are technology selection and the optimisation of process operation. A large contrast regarding their aims is found, as process optimisation tools clearly define their goals and indicators used, whilst technology selection procedures often use vague language making it difficult for decision makers to connect selected indicators and resultant outcomes. Several recommendations are made to improve decision support system usage, such as more rigorous indicator selection protocols including participatory selection approaches and expansion of indicators sets, as well as more structured investigation of results including the use of sensitivity or uncertainty analysis, and error quantification.

This comprehensive review critically assesses traditional and emerging technologies for domestic wastewater treatment and reuse, focusing on the transition from conventional centralised systems to innovative decentralised approaches. Through an extensive literature search on domestic wastewater systems serving a population equivalent of less than or equal to 10, the study juxtaposes linear and circular methods and highlights their impact on urban water management and the environment. The papers reviewed were classified into five categories: Environmental studies, economic studies, social studies, technological studies, and reviews and policy papers. The analysis was carried out separately for linear and circular approaches within each category. In addition, the maturity of the technology (lab/pilot or full-scale application) was taken into account in the analysis. The research landscape is shown to be evolving towards circular methods that promise sustainability through resource recovery, despite the dominance of linear perspectives. The lack of clear progress in decentralised technologies, the scarcity of circularity assessments and the challenges of urban integration are highlighted. Operational reliability, regulatory compliance and policy support are identified as key barriers to the adoption of decentralised systems. While conventional pollutants and their environmental impacts are well addressed for linear systems, the study of emerging pollutants is in its infancy. Conclusions on the impact of these hazardous pollutants are tentative and cautious. Social and economic studies are mainly based on virtual scenarios, which are useful research tools for achieving sustainability goals. The conceptual frameworks for assessing the social dimension need further refinement to be effective. The paper argues for a balanced integration of centralisation and decentralisation, proposing a dual strategy that emphasizes the development of interoperable technologies. It calls for further research, policy development and widespread implementation to promote decentralised solutions in urban water management and pave the way for sustainable urban ecosystems.

Wastewater treatment plants (WWTPs) are evolving from pollution control facilities into resource recovery hubs, aligning with circular economy principles. However, assessing their transition requires robust methodologies that integrate environmental, economic, and circularity dimensions. This study aims to evaluate the sustainability and circularity performance of a WWTP in Cyprus upgraded with additional treatment stages to recover nutrient-rich sludge for fertilizer and treated water for irrigation. To achieve this, a combined methodological framework was applied, incorporating standardized Circularity Assessment (based on ISO 59,004), Life Cycle Assessment (LCA), and Life Cycle Costing (LCC). Circularity was assessed using a dual-indicator approach: "resource flow indicators" (covering material, energy, and economic flows) and "circular actions indicators" (capturing process optimization, repurposing, cascading, and regeneration). Environmental and economic impacts were quantified using LCA and LCC, respectively, while sensitivity analyses explored the effects of renewable energy integration and process simplification. Results show that while the upgraded WWTP enhances circularity through increased resource recovery and high-value product generation, it also incurs higher environmental impacts and operational costs due to energy-intensive technologies (distillation, reverse osmosis, and nanofiltration), increasing the impacts in values that can achieve +60 % in some impact categories. Sensitivity scenarios demonstrated that reducing energy demand and increasing renewable energy use can improve sustainability outcomes, with the higher average impact reduction achieving -20 %, though often at the expense of circularity performance. The study highlights the trade-offs between maximizing resource recovery and minimizing environmental and economic burdens, emphasizing the need for optimized process design and supportive policy frameworks to enable WWTPs to function as effective circular economy enablers. The findings show that advanced treatment technologies enhance circularity through increased resource recovery, but also entail elevated energy demands and limited economic viability. While frameworks like ISO 59,004 support multidimensional assessment, further methodological development is needed to guide sustainable decision-making.

The industrial sector’s water consumption is projected to increase by 400% by 2050, placing significant stress on freshwater reserves. To address this challenge, innovative solutions for water management are crucial. This paper proposes a comprehensive framework for Rainwater Harvesting (RWH) in industrial settings, offering a methodology to assess the potential for RWH implementation across EU industrial sites. The framework integrates internal and publicly available datasets, including EU climate change monthly average rainfall data from the Copernicus Climate Data Store, to create current and prospective scenarios for RWH. The methodology evaluates critical parameters co-created with industrial stakeholders, such as catchment area, water quality, and industrial water requirements. This approach allows for site-specific assessments, enabling industries to reduce freshwater consumption and support sustainability goals within the Horizon 2050 framework. Our findings indicate that implementing RWH systems can significantly contribute to a sustainable and circular economy by reducing annual freshwater consumption, promoting resource reuse, and lowering industrial water costs. This framework provides industries with a tool to assess RWH feasibility, supporting their efforts to prepare for increased water demands and contribute to environmental conservation.

This review explores the social impacts of electricity production by applying the framework of Social Life Cycle Assessment (S-LCA). The authors adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to select studies that were published post-2010 and used S-LCA in the context of various electricity sources, including bioelectricity, solar, wind, and hydropower. The search yielded 13 eligible studies that employed both generic and site-specific assessment strategies, primarily relying on the Social Hotspot Database and Product Social Impact Life Cycle Assessment database for generic evaluations. The findings emphasize the Workers stakeholder as the most frequently examined, with significant attention also given to the Local Community, Society, Value Chain Actors, and Consumer stakeholders when social databases are employed. The studies primarily assessed socioeconomic impact subcategories related to labor practices, health and safety, and economic contributions, as well as a tailored set of self-developed social impacts and indicators specific to the energy sources and geographical contexts examined. This review demonstrates the crucial role of S-LCA in revealing the socio-economic impacts of electricity generation and the need to consider the impacts on Local Community and Society stakeholders through site-specific assessments. Such insights are crucial for guiding policy reforms and industry practices towards more socially responsible energy production.