Enhancing microplastic removal and nitrogen mitigation in constructed wetlands: An earthworm-centric perspective

Area of Science:

• Environmental Science
• Ecology
• Microbiology

Background:

• Microplastics (MPs) in wastewater threaten ecosystems.
• Constructed wetlands (CWs) can remove MPs, but efficiency varies.
• Environmental factors and system equilibrium limit CW performance.

Purpose of the Study:

• To investigate the use of Eisenia fetida (earthworms) to enhance constructed wetland ecological performance.
• To improve the removal efficiency of microplastics and associated pollutants in CWs.
• To understand the microbial mechanisms behind earthworm-mediated pollutant removal.

Main Methods:

• Introduction of Eisenia fetida into constructed wetland systems.
• Monitoring of polylactic acid (PLA) microplastic removal efficiency.
• Analysis of chemical oxygen demand, total nitrogen, and ammonium nitrogen levels.
• Microbial community analysis, focusing on Actinobacteria and nitrogen cycling microbes.

Main Results:

• Earthworm addition significantly increased PLA microplastic removal by 13.5%.
• Removal efficiencies for chemical oxygen demand, total nitrogen, and ammonium nitrogen improved by 8.4%, 9.7%, and 10.5%, respectively.
• Earthworm ingestion of PLA MPs increased Actinobacteria abundance, aiding degradation.
• Nitrogen-fixing and nitrifying microbes increased by 12.4% and 4.3%, respectively.

Conclusions:

• Eisenia fetida enhances microplastic removal and nutrient cycling in constructed wetlands.
• Earthworms facilitate PLA microplastic degradation via gut microbial restructuring.
• Earthworms promote nitrogen cycling by enriching specific microbial communities.
• This study presents a novel ecological approach for pollutant management and nutrient recycling in CWs.