Purpose
This work aims to provide insights on the application of social life cycle assessment (S-LCA) in evaluating the social impacts associated with municipal wastewater treatment (WWT). The study assesses the social risks and social performance of two municipal WWT systems in Catalonia, Spain: a conventional wastewater treatment plant (WWTP) (Reference System) and a novel system that recovers water and other valuable resources (Novel System).

Methods
S-LCA was conducted at Generic and Site-Specific levels using 1 m3 of wastewater treatment as the functional unit (FU). The Generic assessment was conducted via the Product Social Impact Life Cycle Assessment (PSILCA) database, while the Site-Specific assessment employed the Subcategory Assessment Method (SAM) with four-level reference scales to assess the social performance of the WWTP operator and its first-tier suppliers. Furthermore, activity variables were calculated based on organizations’ shares in the total costs per FU, and the Novel System’s multifunctionality was solved through economic allocation. Results were aggregated by (i) assigning equal weights to organizations and (ii) factoring in organizations’ weights and the allocation factor, leading to results per FU.

Results and discussion
The Generic analysis results indicated that the Novel System entailed fewer social risks than the Reference System. Most social risks in both systems occurred in the subcategories “Access to material resources,” “Fair salary,” “Freedom of association and collective bargaining,” “Contribution to economic development,” and “Corruption.” In the Site-Specific assessment, the Novel System presented better social performance than the Reference System per 1 m3 of wastewater treatment. The latter’s performance per FU did not meet the basic requirement in four out of eleven subcategories, mainly due to the performance and weight of a chemical supplier. Allocation greatly benefitted the Novel System’s results per FU compared to the results obtained when equal weights were applied.

Conclusions
Activity variables were used to connect organizations’ conduct with particular WWT systems, and multifunctionality was solved. This approach allowed for obtaining results per FU at both assessment levels. However, social performance was also evaluated by calculating the average social performance of each system without considering activity variables and the FU, leading to different results. The social performance of the Novel System per FU was satisfactory across all subcategories but required improvement in four subcategories based on the average results. Given the limitations of using activity variables and allocation in S-LCA, further research is necessary to appropriately evaluate and compare the social effects of novel resource recovery systems.@en

The production of capital goods is often ignored in the life cycle inventory phase of life cycle assessment studies. In this study, we investigated whether capital goods production, i.e., manufacturing of capital equipment and construction of infrastructure, and operation affect the results of the social life cycle assessment (S-LCA), using a case study of a desalination plant with multiple co-products in Lampedusa, Italy. The assessment was conducted using the PSILCA database to evaluate 20 impact subcategories and four stakeholder categories: Workers, Value chain actors, Society and Local community. Monetary data were collected for the manufacturing of equipment, labor and miscellaneous work during plant construction, working hours of employees during operation, consumed electricity and chemicals, and recovered materials during operation. Furthermore, multi-functionality was addressed through substitution, system expansion, and economic allocation to examine how these approaches affected the results. The functional unit was 1 m³ industrial water. Equipment manufacturing and plant construction contributed up to 15% to stakeholder categories and between 2% and 75% to impact subcategories of the substitution approach, and up to 51% for impact subcategories of system expansion and economic allocation. Equipment manufacturing and plant construction contributed to a high extent to “Health and safety” (of Workers), “Discrimination” and “Local employment” due to the construction and electrical sectors. Credits in substitution lead to a lower contribution of the operational stage and negative societal impact values. If S-LCA practitioners must limit the considered impact subcategories, for generic or site-specific analysis, the “Health and safety” (Workers), “Local employment”, and “Fair salary” should be investigated.

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