Cleaning Water Naturally: How Constructed Wetlands Combat Antibiotics and Superbugs

Redacción HC
21/09/2024

As global concern grows over antibiotic resistance, wastewater treatment has become a frontline battleground in the fight against "superbugs." While traditional water treatment plants remove pathogens and pollutants, they often fall short in tackling two emerging threats: residual antibiotics and antimicrobial resistance genes (ARGs). A recent real-world study published in Water Research explores how nature-based solutions, specifically constructed wetlands, may outperform conventional methods in eliminating these invisible dangers from our water systems.

Why Antibiotic Residues and ARGs Are a Hidden Crisis

Modern medicine relies on antibiotics, but when leftover drugs and resistance genes enter water systems, they can create hotspots for the evolution and spread of resistant bacteria. Hospitals, cities, and agricultural runoff all contribute to this growing problem. Yet, conventional tertiary treatment systems—those using UV light, filtration, and chlorination—often fail to remove these contaminants completely.

This is more than a technical oversight: unfiltered antibiotics and ARGs are reshaping aquatic ecosystems and human health risks, contributing silently to the global antimicrobial resistance (AMR) crisis.

What the Study Explored: Nature vs. Technology

A research team from Spain’s Institute of Environmental Assessment and Water Research (IDAEA-CSIC) and Germany’s Karlsruhe Institute of Technology conducted a full-scale, seasonal comparison between:

• Two types of constructed wetlands:
  • Surface Flow Constructed Wetlands (SF-CW)
  • Subsurface Horizontal Flow Wetlands (SSHF-CW)
• One conventional tertiary wastewater treatment plant (WWTP) using sand filtration, UV radiation, and chlorination.

Sampling was conducted in Catalonia (Spain) during both summer and winter, examining:

• 21 antibiotics, with concentrations ranging from 2 to 1218 ng/L
• ARGs sul1 and dfrA1, with up to 9 million copies per 100 mL
• Microbial communities before and after treatment using DNA sequencing and qPCR

Key Findings: Nature-Based Wetlands Outperform Traditional Plants

1. Antibiotic Removal Efficiency

Constructed wetlands significantly outperformed the conventional system:

• SF-CW removed up to 88% of antibiotics on average
• SSHF-CW removed 69%
• Conventional WWTP: only 36–39% efficiency

2. ARG Elimination

When it came to removing sul1 and dfrA1, both wetlands reduced gene abundance by 2 to 3 log units, far better than the limited 1–2 log reductions observed in the traditional system.

3. Microbial Community Shift

Wetlands fostered a shift toward natural, soil-like microbial communities, dominated by beneficial bacteria like Alphaproteobacteria. In contrast, conventional treatment plants showed little change in microbial composition, meaning they did not effectively disrupt antibiotic-resistant populations.

4. Lower Ecotoxicological Risk

• Wetlands reduced ecotoxicological risk (RQs) by more than 70%
• Conventional systems achieved a mere 6% risk reduction

This suggests that wetlands not only remove harmful substances but also improve the ecological health of discharged water.

Why This Matters: Global Implications for Public Health and Policy

The results are not just scientifically significant—they're politically and socially urgent.

• Public Health: Reducing ARGs in wastewater means fewer opportunities for resistance to spread through water reuse, recreational exposure, or agricultural irrigation.
• Water Regulation: The study supports revising water quality standards to include ARGs as monitoring targets.
• Sustainable Infrastructure: Constructed wetlands offer low-cost, energy-efficient alternatives especially well-suited to low- and middle-income countries.

In fact, these systems align with global strategies from the WHO, UN Sustainable Development Goals (SDG 6: Clean Water and Sanitation), and the One Health approach to integrate environmental health with human and animal health.

Real-World Applications: Where and How to Act

Recommendations from the Researchers:

1. Expand comparative studies to tropical, arid, and urban-industrial regions to understand how climate and pollutant loads affect performance.
2. Design context-specific wetlands, adapting plant species, flow types, and size to local needs.
3. Integrate constructed wetlands into existing WWTPs, using them as polishing stages for antibiotic and ARG removal.
4. Support public-private partnerships to fund long-term monitoring and maintenance, especially in vulnerable areas.

The Bottom Line: Natural Systems Are Part of the Solution

While no single solution can fully address antimicrobial resistance, constructed wetlands demonstrate real, scalable potential to address part of the problem where it begins—in wastewater. They don’t require complex machinery, high energy input, or synthetic chemicals. Instead, they harness the biological, chemical, and physical processes of nature to purify water in ways traditional systems can’t.

This is not just environmental science—it’s a blueprint for a healthier, more sustainable future. For countries battling antibiotic resistance with limited resources, nature-based systems could be the missing piece.

Topics of interest

Pollution