Exploring Coupled Physical, Biological and Chemical Processes that Control Lead Fate and Transport through Plastic Plumbing Materials

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Lead contamination in drinking water is a serious public health concern in the United States. Because even low levels of lead exposure can cause neurological damage and learning disabilities in children, the U.S. EPA has set the maximum contaminant level goal for lead in drinking water at zero. Lead in drinking water originates predominantly from the corrosion of lead-bearing pipes and plumbing fixtures. Plastic pipes are increasingly being utilized to replace aging water pipes to minimize and eliminate lead contamination. Despite the commonly held assumption that plastic water distribution pipes are inert, recent research has established that plastic pipes can react with lead in water. However, the mechanisms of lead sorption onto and release from plastic pipes are poorly understood. The goal of this research is to advance our understanding of the sorption and release of lead by plastic water distribution pipes. To achieve this goal, the research team will characterize the extent, rate, and mechanisms of lead sorption and release from high-density polyethylene (HDPE) and crosslinked polyethylene (PEX) pipes into drinking water. Successful completion of this project will further our understanding of the risk posed by lead and help minimize the release of lead in drinking water. Further benefits to society will be achieved through STEM education and training at the college level and through outreach to K-12 students, thus increasing the scientific literacy of the nation.The formation and growth of bacterial biofilms in drinking water distribution systems is a major health concern. While significant research has been devoted to the effect of biofilms on the release of lead via corrosion of metallic water pipes, the impact of biofilms on lead sorption and release by plastic water pipes has largely been overlooked. This issue is concerning in light of the fact that plastic pipes may be more susceptible to biofilm development than metallic pipes. The goal of this research is to investigate the physical, chemical, and biological mechanisms of lead sorption and release by HDPE and PEX plastic water distribution systems. To achieve this goal, the research team will: i) investigate the role of biofilm structure and water flow on lead sorption extent and kinetics onto HDPE and PEX pipes; ii) examine the role of biofilm structure on lead desorption and release from plastic pipes under varying water chemical composition and flow conditions; and iii) combine genomic assays with bioinformatics and machine learning to identify biomarker genes that could be used to detect lead contamination signatures via the evaluation of microbial gene expression profiles in water pipe biofilms. Successful completion of this research will address significant gaps in our knowledge on the role plastic pipes play in lead sorption. This new knowledge will help inform efforts to control lead deposition onto and release from drinking water distribution pipes.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.