Integrating persistent mobile toxic chemicals and micropollutants into life cycle assessment: a cradle-to-grave evaluation of a low-carbon, nature-based wastewater treatment technology

Persistent, mobile, and toxic chemicals (PMTs) and micropollutants (MPs) are widespread in aquatic environments, with wastewater as their primary source. As freshwater scarcity intensifies, wastewater reuse is critical for sustainable water management. However, traditional wastewater treatment processes are largely ineffective at removing PMTs and MPs. Advanced oxidation and chemical treatments, also known as tertiary treatments, can be effective, but are energy-intensive and may generate secondary pollution products. Nature-based solutions offer a promising alternative to mechano-chemical tertiary treatments, but they typically have a large land footprint and slow treatment rates limiting their scalability and economic viability. A recently developed nature-based solution leverages the filter-feeding capabilities of Daphnia (waterfleas) to capture and bioaccumulate a broad spectrum of PMTs and MPs, along with excess nutrients and suspended solids. As an emerging technology, its life cycle environmental impacts remain unassessed. This study presents the first cradle-to-grave life cycle assessment (LCA) of this emerging technology. This study explicitly and systematically integrates PMTs and MPs into a cradle-to-grave assessment of this technology. It also assesses ecotoxicity and eutrophication as both life-cycle impacts and treatment-related indicators based on changes in these chemical pollutants and phosphorus concentrations in water, addressing effects rarely considered in wastewater treatment LCAs. Results show that the technology achieves a near zero overall environmental footprint while reducing ecotoxicity and eutrophication potential with net benefits of about 28 CTUe and 3.5E-05 kg P-eq, respectively. Scenario-based analysis indicates that recycling of infrastructure materials can reduce resource depletion, further reducing the carbon footprint of the technology. This LCA sets a new benchmark for evaluating Nature-Based tertiary wastewater treatment technologies by including PMT and MP removal and highlights the strong potential of the Daphnia-based technology as a sustainable, scalable option for tertiary water treatment and reuse.