Evaluating the fate of UV filters and transformation products during managed aquifer recharge: the role of reactive barriers, biofilms and varying redox.

Ultraviolet filters (UVFs) are emerging organic contaminants that are present in personal care (sunscreens and many cosmetics) and numerous industrial products. Among UVFs, the group of benzophenone derivatives are the most used worldwide. Benzophenone-3 (PB-3, oxybenzone) is one of the most common UVF. BP-3 is considered as an endocrine disruptor with estrogenic activity, it is photo-stable, lipophilic and bioaccumulates in different organisms. The widespread use of BP-3 has led to its release into aquatic ecosystems mainly via discharge of wastewater treatment plant effluents. Common sources of water for Managed Aquifer Recharge (MAR) are affected, to some extent, by effluents of wastewater treatment plants and therefore, MAR has been proposed as a potential source of these compounds to the environment. Understanding the fate of UVFs but also of their transformation products (TPs) in MAR is relevant because some of them can be more ecotoxic than the parent compound. We evaluated the fate of selected UVFs and its TPs at different compartments (water, soil and biofilm) in two field pilot scale MAR systems; one of them operated with a permeable reactive barrier based on compost and the other with sand (without reactive barrier). We compared the temporal and spatial evolution of these UVFs before and after a slug injection of lithium acetate, as organic carbon source, in the two MAR systems. Quantification of selected UVFs and TPs showed that the two MAR systems promoted the removal of UVFs. Extended removal was enhanced by the compost reactive barrier, in which lower concentrations of all selected UVFs and TPs were measured. The fact that they were detected and quantified more often sorbed onto the biofilm and organic fraction of sediment than in the aqueous phase suggested that degradation takes place in the two solid compartments.

 

Acknowledgements

This work was financially supported by the Catalan Research Project RESTORA (ACA210/18/00040), by the Spanish Ministry of Science and Innovation through MONOPOLIOS (RTI2018-101990-B-100, MINECO/FEDER) and Project CEX2018-000794-S), as well as the EU project MARADENTRO (PCI2019-103425 and PCI2019-103603). We also thank the Consorci de la Costa Brava Girona (CCBGi) for the unlimited access to the WWTP.