ASSESSMENT OF MICROPLASTIC POLLUTION AND ITS POTENTIAL ROLE IN THE ENVIRONMENTAL DISSEMINATION OF ANTIBIOTIC RESISTANCE GENES IN WASTEWATER

Abstract

The Wastewater Treatment Plant (WWTP) is an important location where anthropogenic contaminants, microplastics (MPs) and antibiotic resistance genes (ARGs) meet, where microplastics, as vector surfaces, provide bacterial colonization and horizontal gene transfer of resistance genes. This research has assessed microplastic counts, morphologies and statistical relationship with important ARGs (tetA, sul1, blaTEM) as well as the Class 1 integron integrase gene (intI1) in various wastewater treatment stages. A data set of 100 samples (n=50 Influent, n=50 Effluent) were analysed by non-parametric comparison tests, Spearman rank correlation and multivariable ordinary least squares regression models. The mean MP concentration in the effluent showed significant reduction from the influent water from 234.43±82.57 particles/L to 50.58±26.28 particles/L (p<0.001) representing a removal efficiency of 78.42%. Total ARG abundance decreased from 620,879.90±822,954.64 to 25,267.86±14,997.97 copies/mL (p<0.001, 95.93% reduction). Spearman analysis revealed strong positive correlations between MP abundance and total ARGs (ρ=0.791, p<0.001), sul1 (ρ=0.802, p<0.001), intI1 (ρ=0.762, p<0.001), tetA (ρ=0.753, p<0.001), and blaTEM (ρ=0.751, p<0.001). A moderate positive correlation between abundance of MP and total ARGs (ρ=0.474, p<0.001) was only found within influent samples. Log-transformed MP abundance (β=0.468, p=0.013) and treatment stage (β=0.955, p<0.001) were the two independent variables that were found to predict total ARG load (R²=0.813), with multivariable OLS regression. Conventional WWT processes significantly decrease absolute MP and ARG loads, but existing effluent discharge still carry persistent MP carriers containing class 1 integrons and ARG into receiving aquatic environments, thus the necessity of developing and implementing new and improved technologies that are capable of simultaneous removal of particulate MPs and genetic pollutants.