Biological pretreatment of wastewater using Daphnia magna: implications for the removal of microplastics and emerging contaminants

Emerging contaminants (ECs) are increasingly detected in wastewater streams due to their historical exclusions from routine monitoring and regulatory frameworks. This group includes pharmaceuticals and personal care products (PPCPs), hormones, per- and polyfluoroalkyl substances (PFAS) and microplastics (MPs), many of which are only partially removed by conventional wastewater treatment plants. Therefore, these contaminants are continuously discharged into aquatic environments, posing potential ecological and human health risks. Among ECs, MPs are particularly concerning because they can disrupt aquatic food webs and act as vectors for the adsorption and transport of other pollutants such as heavy metals and pharmaceutical residues [1,2]. This study investigated the potential of Daphnia magna, a filter-feeding crustacean widely used in ecotoxicology, as a complementary biological tool for the removal of ECs and MPs from wastewater following tertiary treatment processes [3]. Wastewater samples were collected monthly over five months (May to September 2025) from a National Trust site in the United Kingdom and analysed before (inlet) and after exposure to D. magna (outlet). Chemical contaminants were extracted using solid phase extraction (SPE) and quantified by UPLC coupled to high-resolution mass spectrometry, while MPs were quantified gravimetrically and characterised by optical microscopy and µ-FTIR spectroscopy. Chemical analysis revealed the presence of multiple pharmaceuticals and lifestyle compounds, with tramadol and glyburide being the most frequently detected analytes. Only clotrimazole and hydrocortisone exhibited consistent removal across all sampling months. In contrast, MPs analysis showed a systematic decrease in MP mass in outlet samples throughout the monitoring period, indicating that D. magna may contribute to MP removal from wastewater. Temporal variation in removal efficiency was observed and were partially associated with rainfall patterns, suggesting environmental conditions influence ingestion efficiency. Overall, the findings suggest that D. magna has greater potential for reducing MP loads, particularly cellulose-based particles, than for consistently removing dissolved chemical contaminants. These results highlight the promise of employing biological filter feeders as nature-based tertiary treatment strategies in wastewater management. References: [1] Bolong, N, et al. Desalination 239, 229-246 (2009). [2] Sauve, S, Desrosiers, M. Chem. Centr. Jour. 8, 1-7 (2014). [3] Abdullahi, M, et al. Env. Sci. & Techn. 56, 14237-14248 (2022).