Pathogens Survive Wastewater Treatment on Microplastics, Study Finds

New research reveals that pathogens sheltered on microplastics evade wastewater treatment, raising potential health and environmental concerns.

A recent study by the Norwegian University of Life Sciences, published in PLOS ONE, has brought attention to a potentially significant gap in wastewater treatment processes. Researchers led by Dr. Ingun Lund Witsø discovered that microplastics in wastewater systems provide refuge for human pathogens, allowing them to persist through treatment and subsequently re-enter the environment. These findings underscore the need for improved strategies in both wastewater management and microplastic control, as the persistence of harmful microbes poses challenges to environmental health and water reuse efforts.

Wastewater treatment plants are traditionally designed to remove contaminants from water before releasing it back into natural ecosystems or repurposing it for other uses. However, microplastics—tiny plastic fragments prevalent in wastewater—can resist breakdown in these facilities. More concerningly, microplastics become colonised by microbial biofilms, forming what scientists term “plastispheres.” These biofilms are sticky communities of microorganisms, including pathogenic bacteria and viruses, that attach to microplastic surfaces, enabling them to persist and potentially spread even after the wastewater has undergone treatment.

Pathogens Identified in Microplastic Biofilms

The study analysed three types of plastic in wastewater, focusing on microbial cultures and genetic analysis to determine the pathogens living within these plastispheres. The researchers identified several well-known foodborne pathogens among the plastisphere-dwelling microbes, including Listeria monocytogenes, Escherichia coli, norovirus, and adenovirus. Furthermore, they successfully cultured Klebsiella pneumoniae and Acinetobacter spp., both associated with various infections, from raw and treated wastewater. The findings suggest that these biofilms protect pathogens from the effects of standard wastewater treatment processes.

Dr. Witsø and her team’s work builds upon existing concerns about microplastics in wastewater, extending them to include not only environmental pollution but also public health risks. The presence of such harmful pathogens on microplastics challenges the existing notion that wastewater treatment fully sanitises wastewater. As the authors of the study noted, “Plastics in wastewater treatment plants are colonised by microbial biofilms, or ‘plastispheres,’ which can harbour pathogens… that persist through treatment processes.” This persistence highlights the plastisphere’s potential role as a hidden source of microbial contamination that could infiltrate the water cycle and even the food chain.

Implications for Wastewater Reuse and Microplastic Management

The implications of these findings extend beyond wastewater treatment to the broader practice of wastewater reuse. With rising global demand for recycled water, the ability to safely reuse treated wastewater is crucial, particularly for applications in agriculture, landscaping, and other non-potable needs. However, the study suggests that pathogens surviving within plastispheres may enter reused water, ultimately posing risks to food safety and public health. Wastewater reuse has previously been viewed as a sustainable solution, but this research highlights the pressing need for additional safeguards against plastisphere-associated pathogens.

Addressing these risks will require a multi-faceted approach involving not only upgrades to wastewater treatment processes but also proactive efforts to curb plastic pollution at the source. Technologies designed to filter out microplastics before or during wastewater treatment could mitigate the issue, while policies targeting plastic waste reduction would address the root cause. The researchers emphasise that ongoing innovation and research are essential to develop effective measures for removing both microplastics and the pathogens they carry from wastewater systems.

This study underscores the pressing need for the scientific and environmental communities to address the emerging public health implications of microplastics. In a world increasingly focused on sustainability and the safe reuse of water, new strategies will be essential to ensure that recycled water does not inadvertently become a vehicle for pathogenic spread.