Evaluating Remedies for Pathogen Contamination of Urban Groundwater

This study addresses groundwater contamination in urban areas from aging sewer systems. A mounting number of studies demonstrate that urban groundwater resources, including those which are used for public water supply, are contaminated by human-specific fecal pathogens in wastewater that can cause illness. This research sought to evaluate the adequacy of federal and state drinking water regulations in the United States to protect human health from fecally-contaminated groundwater. Interviews conducted with various stakeholders were used to identify gaps in the existing regulatory framework and to identify approaches to improve the quality of supplied groundwater. Disinfection of water supplies is not mandated, but it is an effective and relatively inexpensive barrier to reduce the risk of pathogen contamination. Among avenues identified for improvement, utility committees and oversight boards should be educated about pathogens in drinking water and the consequences of waterborne illness in communities served by non-disinfected groundwater.;A second goal of this research is to increase understanding of the physical conditions in groundwater systems that promote the transport of infectious viral pathogens from leaky sanitary sewers to groundwater systems. A field study was conducted to identify conditions that lead to the episodic nature of pathogen occurrence in well water and that promote the transport of infectious pathogens from leaky sanitary sewers to groundwater systems. Findings support the hypothesis that short-term climatic conditions exert control on subsurface transport of viral pathogens to the water table. A second aspect of this work involved characterization of groundwater flow through preferential pathways, including multi-aquifer wells (wells that cross-connect layered groundwater systems). Simulations with a numerical model calibrated to the study area demonstrated that multi-aquifer wells provide rapid, advective transport pathways to the confined aquifer, but do not on their own account for the presence of pathogens in deeply cased municipal wells. An alternative hypothesis suggested by this modeling is that pumping from deeply cased wells induces vertical gradients that result in short travel times, on the order of tens of days, across a regional, confining aquitard.