Effects of Biofilm Colonization on the Dynamics of Microplastics in Turbulent Flow

Utah State University, Logan UT

Investigators

Abstract

Millions of tons of plastic waste are produced annually, creating a significant global challenge. Small pieces of plastic, called microplastics, have emerged as the most significant environmental threat resulting from this trend. Microplastics come from the breakdown of larger plastic items such as bottles and bags, as well as from the production of everyday products. The small size of microplastics makes it difficult for wastewater treatment plants to remove them from the water. This results in microplastics eventually finding their way to rivers, lakes, oceans, and even groundwater. While these problems have been recognized for several years, it is less well-known what role microplastics play in the mobilization of microbes in water. Small microbes form sticky coatings called biofilms on the plastic surfaces. These biofilms can harbor harmful bacteria that may lead to the spread of disease, thus creating a hazard to human health. Moreover, biofilms can alter the weight, shape, and size of microplastics. This influences their movement in water and makes it difficult to predict where microplastics will end up. This study aims to investigate how different types of biofilms impact the movement of microplastics. Results will be used to build computer models to more accurately predict the environmental movement of microplastics. Successful completion of this research will enhance our understanding of how biofilm-coated microplastics navigate through water. Society will benefit from information that can inform strategies to remove microplastics from water systems to protect human and ecological health. Microplastics (MPs), plastic particles smaller than 5 microns, have become a significant environmental concern. This is due to their widespread presence in aquatic environments and adverse effects on human and ecological health. Wastewater treatment plants are a critical process in removing MPs to prevent their release into the environment. However, the properties of MPs make them challenging to remove using conventional wastewater treatment processes, resulting in their release to receiving waters. MPs can also serve as substrates for microbial colonization, leading to the formation of biofilms on their surfaces. These biofilms may contain pathogens and bacteria resistant to conventional disinfection methods, posing risks to public health if released into the environment. Common MP particles found in water systems include fibers and films. For such thin particles, biofilm colonization can significantly increase MP thickness. The transport dynamics of biofilm-coated MPs are an under-researched topic. The goals of this multidisciplinary study are to (1) assess differences in the characteristics of biofilms of different microorganisms grown on MPs; (2) quantify the dispersion and settling dynamics for biofilm-coated MPs under turbulent conditions; and (3) develop a machine learning model to predict biofilm-coated MP transport in field-scale situations. Measurements will include biofilm thickness, topography, and adhesive strength, as well as other metrics generated from both pure strains and mixed cultures, across diverse MP materials and colonization periods. Results will be used to predict the transport of various biofilm-coated MPs in turbulent treatment systems and aquatic environments. Results will benefit society by enabling better design to remove MPs from water treatment systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.