A Social life cycle assessment of Urban Wastewater Treatment Systems with Resources Recovery

Abstract

Global water-related impacts are in constant aggravation due to climate change, increased water demand, intensive human activities, and deterioration of the quality of water bodies.
Under this paradigm, humanity must adapt and implement measures to ensure both the quality of water bodies and the sustainable management of resources.
As a result, unexploited water resources, such as wastewater, have been a focus of attention among researchers. Wastewater Treatment (WWT) technologies stand as an important step to promote water reuse and potentially recover raw materials with added value.
While WWT technologies have been assessed at the environmental and economic levels, their social repercussions are not extensively studied. Hence, the present master thesis project resorts to the Social Life Cycle Assessment (S-LCA) framework to execute an evaluation of the social performance of an innovative WWT system for resource recovery in Portugal. S-LCA was conducted at the organizational level, assessing the social performance of organizations in the value chain through the evaluation of the social effects on Workers, Consumers, Local Community, Society, and value chain actors. In addition, a generic assessment was performed to identify hotspot areas of the Portuguese water sector, following the S-LCA framework.
The systems under analysis integrate a Water Mining (WM) project case study, where an innovative urban WWT technology is implemented. In the two systems defined, the wastewater is treated with the Nereda technology and safely discharged into the environment. Nevertheless, while in the reference system the sludge generated from the treatment is stored or forwarded to landfill, in the novel system a new biobased raw material is recovered.
Regarding the generic assessment, a total of eleven impact subcategories were listed as critical areas regarding the operation of companies in the WWT sector. These were further investigated in the site-specific assessment conducted at the plant level. The results of the site-specific assessment indicate that the organisations included in the assessment performed well for both
systems under analysis. However, organizations’ individual performances reflect that improvements are necessary mainly in the subcategories “equal opportunities/discrimination” and “community engagement”. Other subcategories where organizations need to improve are “promoting social responsibility”, “social benefits/social security”, “local employment”, “health and safety of consumers”, “safe and healthy living conditions” and “public commitment to sustainability issues”. For each organization that did not reach a satisfactory performance
level in a certain subcategory, improvement recommendations were proposed.
In general, the novel system performs better in all impact subcategories when compared to the reference system. Nonetheless, this result is intrinsically connected to system characteristics and model decisions such as weighting factors definition and multifunctionality matters, which remain as rather abstract concepts that do not completely reflect reality.
The main challenges faced during the study concern the accessibility and availability of site-specific and generic data. In terms of site-specific assessment, the high similarity of the reference and novel systems in terms of organizations involved hindered the comparison of the two systems.
To conclude, the S-LCA methodology allowed the identification of social hotpots areas as well as the evaluation of the reference and novel systems' social performance, contributing to the elaboration of strategies to improve social sustainability along the value chain of innovative WWT technologies.