Testing the incorporation of bioassays into life cycle assessment: A case study on advanced wastewater treatment

Artikel i vetenskaplig tidskrift, 2025

Purpose: Advanced wastewater treatment (AWT) methods, such as the use of ozone (O3) and granular activated carbon (GAC), have been shown to mitigate toxic impacts on receiving waters. However, life cycle assessments (LCAs) on AWT technologies commonly evaluate toxicity through chemical analysis and conclude that the increased toxicity caused by operational inputs exceeds the reduction in toxicity via micropollutant removal from effluent. Here, a novel approach of incorporating bioassays for assessing the toxicity of wastewater effluent within the LCA framework was tested. Methods: To evaluate this recently developed method in a Swedish context, an LCA case study was performed comparing two treatment trains with ozonation and post-treatment—ozonation followed by either a moving bed biofilm reactor (O3-MBBR) or GAC (O₃-GAC)—using data derived from Swedish pilot studies. A suite of in vitro bioassays was utilised to detect estrogenicity, activation of the aryl hydrocarbon receptor, and oxidative stress. Reference substances were employed to calculate the bioequivalent concentration of the samples for each bioassay. Characterisation factors for the reference substances were taken from USEtox2.14 and used to convert the assay results into LCIA results with the rest of the system modelled in LCA for Experts using EF3.1. Results and discussion: The results revealed a markedly disparate outcome compared with the traditional approach of using chemical analysis data as LCA input: the AWT benefits outweighed other toxicological impacts. Notably, oxidative stress emerged as the primary contributor to freshwater ecotoxicity, whereas aryl hydrocarbon receptor activation was the predominant contributor to human toxicity, including cancer risks. The normalised and weighted results showed the same pattern—the benefits of AWT, when based on bioassays, outweighed the environmental impacts considerably. Using different reference substances altered the magnitude of the AWT benefit, although still resulting in a net reduction of toxicological impacts. Regarding the case study, technological considerations, such as ozone source and GAC-filter lifespan, showed to be as important for the result as the choice of AWT technology. Conclusions and recommendations: The coupling of bioassays and LCA thus shows promise as a complementary evaluation to conventional toxicity assessment within LCA, and future research should help establish guidelines on which biological endpoints, bioassays, reference substances, and characterisation factors should be incorporated.