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Assessment of Biofilm Growth on Microplastics in Freshwaters Using a Passive Flow-Through System
Chengyang Jiang1, Husein Almuhtaram1, Michael J McKie1
1Department of Civil and Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada.
Abstract:
Biofilms that colonize on the surface of microplastics (MPs) in freshwaters may pose a potential health risk. This study examined factors that influence MP-associated biofilm growth, including polymer type, degree of weathering, and source water quality. Weathered MPs produced in-lab were employed in biofilm trials conducted on site using a passive flow-through system with raw water at drinking water treatment facility intakes. Adenosine triphosphate (ATP) was used to quantify biofilm abundance; biofilm composition was assessed via metagenomic sequencing. Biofilm growth was observed on all polymer types examined and most prevalent on polyvinyl chloride (PVC), where ATP levels were 6 to 12 times higher when compared to other polymers. Pathogen-containing species including Salmonella enterica and Escherichia coli were present on all polymers with relative abundance up to 13.7%. S. enterica was selectively enriched on weathered MPs in specific water matrices. These findings support the need to research the potential accumulation of pathogenic organisms on microplastic surfaces.
Insights
Microplastics (MPs) in freshwater can host biofilms, including pathogens like Salmonella enterica and Escherichia coli. Polyvinyl chloride (PVC) MPs showed the highest biofilm growth, indicating a potential health risk.
Area of Science:
- Environmental Science
- Microbiology
- Polymer Science
Background:
- Microplastics (MPs) are prevalent environmental contaminants.
- Biofilm formation on MPs can alter their properties and ecological impact.
- Freshwater biofilms on MPs may pose health risks due to pathogen colonization.
Purpose of the Study:
- To investigate factors influencing microplastic-associated biofilm growth.
- To assess the impact of polymer type, weathering, and water quality on biofilm development.
- To identify microbial communities, including potential pathogens, colonizing weathered MPs.
Main Methods:
- Field-based biofilm trials using a flow-through system with raw water from drinking water treatment intakes.
- Utilized weathered microplastics of various polymer types.
- Quantified biofilm abundance using adenosine triphosphate (ATP) assays.
- Assessed biofilm composition through metagenomic sequencing.
Main Results:
- Biofilm growth occurred on all tested polymer types.
- Polyvinyl chloride (PVC) exhibited significantly higher biofilm abundance (6-12 times more ATP) compared to other polymers.
- Pathogenic species, including Salmonella enterica and Escherichia coli, were detected on all polymers.
- Salmonella enterica showed selective enrichment on weathered MPs in certain water conditions.
Conclusions:
- Microplastic biofilms are a common occurrence in freshwater environments.
- Weathered PVC microplastics are particularly prone to substantial biofilm accumulation.
- The presence and enrichment of pathogens like S. enterica on microplastics highlight potential risks to water safety.
- Further research is crucial to understand the public health implications of pathogenic organisms on microplastic surfaces.
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