NATURE: Nature-based solutions to reduce antibiotics, pathogens and antimicrobial resistance in aquatic ecosystems
The findings of the NATURE project underscore the effectiveness of already implemented Nature-Based Solutions (NBS) in mitigating the discharge of antibiotics and antibiotic resistance genes (ARGs) at river catchment scale from wastewater to estuarine areas. Over a two-year period, we conducted a comprehensive sampling campaign across seven NBS sites in three countries to ensure a realistic assessment (Figure 1).
Results from the Danish site demonstrate that employing intensified NBS such as bioelectrochemical and areated constructed wetlands in decentralized wastewater treatments is a compelling solution for reducing aquatic pollutants. Similarly, results from the Spanish site show that NBS like horizontal flow or surface flow constructed wetlands can achieve greater removal efficiencies for antibiotics and ARGs compared to conventional tertiary wastewater treatment technologies based on UV radiation and chlorination, and therefore resulting in a high quality of reclaimed water.
Figure 1. Map illustrating the locations of the NBS evaluated across three distinct countries on a river catchment scale, spanning from wastewater treatments (1 and 2) to saltmarshes (5).
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Figure 2. Conceptional overview of the microbial community structures along the flow paths of the NBS assessed. A shift in microbiological composition is evident, transitioning from faecal bacteria at the entrance of the NBS to a prevalence of rhizosphere and river-related bacteria at the effluent.
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Studies conducted on wastewater effluent-dominated streams reveal that stream renaturalization enhances the attenuation of antibiotics (ABs) and ARGs. Additionally, restored wetlands from Denmark also contribute to the reduction of aquatic pollutants, whereas saltmarshes in Portugal seem also to contribute to the attenuation of some antibiotics in estuarine areas. Beyond the reduction of aquatic pollutants, NBS also influence the shift of microbiological communities from effluent ones to more rhizosphere or plant-related ones (Figure 2).
This shift indicates a transformation in water composition from anthropogenically impacted water to surface-related water, implying that effluent water possesses a similar chemical and biological composition as non-impacted water bodies, thereby foreseeing minimal impact. Furthermore, ecotoxicological assays conducted with green algae have observed a significant decrease in toxicity within NBS, compared to reference strategies evaluated in the project.
These promising results are inspiring and have the potential for transferability to other sites and countries. Within the framework of the NATURE project, high concentrations of antibiotics and ARGs have been identified in five different hospitals in Mali, with their wastewater being discharged into the Niger River. Transferring the knowledge gained from the NATURE project to these sites to establish NBS can effectively reduce the discharge of these pollutants into the Niger River. Stakeholder engagement has been facilitated through individual meetings and workshops with the primary objective of reintroducing nature to aquatic ecosystems to address antibiotic and ARG issues, as well as future pollutants.