CARMA: Constructed wetlands for mitigating Antimicrobial Resistance in reclaiMed water used for the irrigAtion of food crops

National AMR context

Antimicrobial resistance (AMR) poses a significant public health and environmental challenge in Tunisia. Antibiotic consumption in the country ranked second globally between 2000 and 2015, reflecting a high usage rate. Contributing factors to rising AMR in Tunisia include inappropriate antibiotic use in human and veterinary medicine, limited public awareness about responsible antibiotic consumption, and a lack of robust environmental detection and surveillance systems. The environmental dimensions of AMR are exacerbated by water scarcity, the reuse of treated wastewater in agriculture, and inadequate removal of antimicrobial residues during wastewater treatment. Efforts to combat AMR are ongoing, with Tunisia’s National Action Plan emphasizing surveillance, awareness, and infection prevention, yet gaps in addressing the environmental aspects remain critical.

Problem

In Tunisia, wastewater treatment plants (WWTPs) are a significant source of environmental contamination, with 69.4% of water samples from WWTPs found to contain extended-spectrum beta-lactamase (ESBL)-producing E. coli or K. pneumoniae. The incomplete metabolism of antibiotics (ATBs) in humans and animals, combined with improper use and discharge, contributes to antibiotic residues entering wastewater, creating selection pressure for antimicrobial resistance gene (ARG) acquisition in environmental bacteria. While treated wastewater is reused for agricultural irrigation, current treatment processes are insufficient to remove antibiotic residues, antimicrobial-resistant bacteria (ARB), and ARGs. There is also a lack of integration of environmental dimensions into Tunisia’s National Action Plan on AMR. Therefore, innovative and sustainable approaches, such as nature-based solutions like constructed wetlands, are needed to improve wastewater treatment and mitigate the spread of antimicrobial resistance.

Project overview

In Tunisia, the reuse of reclaimed water for irrigation presents environmental and health risks due to the transfer of ATBs, ARB, and ARGs into the food chain. The CARMA project aims to mitigate these risks by implementing nature-based solutions, specifically CWL, to improve effluent quality and reduce the spread of antimicrobial resistance. The project will generate evidence of CWL effectiveness, develop strategies for national-scale implementation, and foster stakeholder engagement through awareness and capacity-building initiatives.

Project objectives

1. Assess the efficiency of constructed wetland, used as a polishing treatment process, in removing ATBs, ARB, and ARGs in reclaimed water and in reducing the risk of transfer to food chain.
2. Conduct a comprehensive analysis of barriers and opportunities and provide a roadmap for progressive scale up of the CWL at the national level, to im-prove the quality of reclaimed water used for irrigation.
3. Raise awareness and build capacities among stakeholders, potential end-users and beneficiaries to encourage broader stakeholder engagement, cross-sectoral partnerships and sustainable practices against the EDAR.

Solutions and outcomes

• Quantitative and qualitative data on ATBs, ARBs, and ARGs in water resources and agricultural products collected, with AMR transfer pathways in wastewater reuse comprehensively analyzed.
• Monitoring protocols for water sampling established and optimized, and a feasibility study integrating technical, economic, health, environmental, and social dimensions completed to guide decision-making.
• Reports and policy briefs produced to inform farm-level implementation, national scale-up, and regulatory changes, with policymakers mobilized to support nature-based solutions.
• Local communities and the public mobilized to adopt responsible antimicrobial practices, increasing awareness and acceptance of AMR mitigation measures.
• A post-doctoral course on EDAR launched in Tunisia, fostering One Health professional training, with academic collaboration and research around EDAR enhanced to inform future strategies.