Plants and microbes pair up to remove pollutants from wastewater in human-made wetlands

As global water resources come under increasing pressure, more efficient and sustainable ways of treating wastewater are needed. Constructed wetlands (CWs) offer a nature-based solution (NBS) that benefits biodiversity. These engineered ecosystems use vegetation, soil and microbes to remove pollutants from wastewater, while also providing habitats, absorbing carbon from the atmosphere, and boosting resilience to flooding. NBS are key to addressing a number of key EU policy priorities, and are supported by the European Green Deal, EU Biodiversity Strategy for 2030 and EU Adaptation Strategy. Several projects funded by Horizon Europe also promote research into NBS.

CWs remove pollutants including nitrogen, phosphorus, heavy metals and medications through a variety of physical, chemical, and biological mechanisms. One key biological process is microbial remediation, in which microorganisms (e.g. bacteria) break down or transform pollutants into less harmful substances. Research has explored the best ways to optimise this process, but the synergistic ways in which plants and microbes interact to improve remediation remains poorly understood, say the researchers behind a new review.

Their study aims to fill this gap by presenting a review of microbial remediation mechanisms in CWs, based on findings from 539 relevant studies published globally between January 2000 and May 2025. They look at key genes, enzymes, and pathways of transformation, in particular focusing on the role of plant-microbe interactions in removing conventional and emerging pollutants, especially antibiotics and polycyclic aromatic hydrocarbons (PAH). They also consider ‘bioaugmentation’ strategies, where specific microbial strains with favourable metabolic traits are added to a CW to enhance pollutant breakdown.