Microbial Diversity and Antibiotic Resistance in Wastewater Treatment Plants of Urban Communities

Thesis Abstract

The pervasive presence of antimicrobial-resistant bacteria in wastewater treatment plants (WWTPs) poses significant threats to public health and environmental safety, particularly within densely populated urban communities where wastewater management systems are heavily utilized. This study aims to investigate the diversity of microbial communities and the prevalence of antibiotic resistance genes (ARGs) within selected WWTPs in an urban setting, with specific objectives to characterize microbial community composition using high-throughput 16S rRNA gene sequencing, quantify ARGs through quantitative PCR (qPCR), and assess the relationship between operational parameters and resistance gene abundance. Employing a comparative cross-sectional research design, the study sampled influent and effluent wastewater from five major WWTPs serving a combined population of approximately five million residents. A total of 200 wastewater samples (each comprising 1-liter grab samples from influent and effluent streams) were collected over four sampling periods across different seasons to account for temporal variability. Data collection utilized structured spectrophotometric analysis for physicochemical parameters, DNA extraction protocols for microbial and ARG detection, and next-generation sequencing (NGS) for microbial community profiling. The molecular analyses involved bioinformatics processing using QIIME2 for microbial diversity assessment and the application of a multiplexed qPCR assay targeting a panel of ARGs conferring resistance to beta-lactams, tetracyclines, sulfonamides, and quinolones. Descriptive statistics characterized microbial diversity indices, while inferential statistics, including multivariate regression analyses, explored correlations between operational factors (such as hydraulic retention time, disinfection practices, and organic load) and ARG prevalence. It is anticipated that the study will reveal a high abundance and diversity of microbial taxa, notably including pathogenic and opportunistic bacteria, with significant detection of ARGs, particularly within influent samples, but also persisting post-treatment in effluent samples. Statistical analyses are expected to demonstrate significant associations between operational inefficiencies and elevated ARG levels, underscoring treatment gaps. The findings aim to contribute novel insights into the microbiological ecology of urban WWTPs and the mechanisms underpinning antimicrobial resistance dissemination within wastewater environments. This research advances current understanding of environmental reservoirs of resistance and microbial ecology, integrating ecological and molecular frameworks—particularly the application of the "One Health" paradigm—to delineate pathways for resistance gene propagation from wastewater to human and environmental health. The study's contributions include establishing baseline data on microbial and ARG profiles in urban wastewater systems, identifying critical points of microbial and resistance gene retention or reduction, and providing evidence-based recommendations for optimizing treatment processes to mitigate antibiotic resistance spread. The main conclusion emphasizes that current treatment protocols may be insufficient to eliminate resistant microbes and ARGs, highlighting the urgent need for enhanced disinfection strategies and policy interventions. Recommendations propose the adoption of advanced oxidation processes and regular monitoring of ARGs as integral components of wastewater management policies. Future research directions include longitudinal studies to track resistance trends over time and intervention-based assessments to evaluate new treatment technologies, thereby informing integrated approaches to combat antimicrobial resistance in urban environments.