Drinking water distribution systems (DWDSs) store and transport treated drinking water to millions of customers across the country. Bacteria colonize and coat the inside pipe surfaces in DWDSs to form biofilms that are responsible for a multitude of problems, including corrosion, taste and odor issues, formation of carcinogenic disinfection-by-products (DBPs), loss of the chlorine residual that protects the water from pathogenic microorganisms. All of these problems have serious financial and public health ramifications for the United States. This project aims to develop a fundamental mechanistic understanding of how biofilms attach to pipes, how strong they are, and how easily they can become detached from the pipe surfaces. This research will be used to develop strategies for removal of biofilms from the DWDSs to address the national goal of ensuring safe drinking water to the citizenry. The broader impacts of this research for society include the development of new technological solutions for water utilities and water plant operators. The project also aims to engage Alaska Native undergraduate students in engineering research, with the long-term goal of increasing the number and broadening the participation of Alaska Native students and graduates in engineering.<br/><br/>The research goal of this CAREER project is to enhance the understanding of biofilm mechanical properties, with specific application to biofilms in drinking water distribution systems (DWDSs). To meet this overall goal, the proposal has three objectives: (1) investigate the correlation between the biofilm exopolymeric substance (EPS) matrix components and biofilm strength in the DWDS; (2) test novel biofilm weakening strategies and examine the impact of these weakening strategies on the contribution of biofilms to DBP formation in the DWDS; and (3) evaluate the impact of distribution system hydraulics and disinfection on biofilm detachment, biofilm cluster formation and reattachment in the DWDS. A primary educational objective of this project is to involve Alaska Native undergraduate students in engineering research. Biofilms will be grown in special bench-scale biofilm growth reactors that provide controlled and well-defined environmental conditions simulating distribution systems. Advanced microscopic and spectroscopic techniques (e.g., nuclear magnetic resonance spectroscopy, fluorescence spectroscopy, confocal scanning laser microscopy and atomic force microscopy) and biofilm-specific micro-cantilever methods will be employed for determination of EPS compositional analysis and mechanical properties. The PI will also investigate a novel strategy for biofilm weakening by targeting the biofilm EPS, instead of the traditional approach of inactivating biofilm bacteria by using biocides. For that purpose, a suite of strength modifiers and detachment promoting agents for biofilms in DWDSs will be evaluated. The mechanistic study of biofilm cohesive strength will identify the role of various EPS macromolecules in providing strength and structure to biofilms, which will be helpful in designing effective strategies for biofilm control. The insights into the mechanistic basis of biofilm strength and detachment will increase our ability to control and manipulate biofilms in various environmental systems (e.g., biofilters, wastewater treatment, DWDSs) and beyond (e.g., medical biofilms). Understanding biofilm dynamics and detachment in DWDSs will help design better strategies to provide improved drinking water quality, significantly benefitting public health.<br/><br/>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.