Foreword: Pathogens and Fecal Indicators in Groundwater

Abstract

Introduction Groundwater usually has lower concentrations of pathogens and other fecal microorganisms than surface water, because of the natural tendency for these organisms to be removed by straining through small pore throats, attachment to mineral surfaces, or inactivation/die-off during transport (McDowell-Boyer et al. 1986). However, the degree of microbial removal in soils and aquifers can vary greatly, depending on factors such as material type, depth to water table, presence or absence of confining layers, flow rate, proximity to fecal sources, fecal concentration in recharge water, and the types of fecal microorganisms present (viruses, bacteria, and protozoa). As a result, in some geologic settings groundwater often contains fecal microorganisms including pathogens. For example, a report from the U.S. Geological Survey on water quality in the upper Tennessee River Basin, where karst is the dominant aquifer type, indicated that all the springs and about one-third of the wells surveyed contained Escherichia coli, presumably from fecal sources (Hampson et al. 2000). Contaminated groundwater was implicated as the cause of just over half of the disease outbreaks related to drinking water in the United States over the period 1971 to 2006 (Craun et al. 2010). Approximately 30% of the outbreaks were related to untreated groundwater and an additional 22% were related to inadequate or interrupted treatment of groundwater. Surveys by various federal and state agencies in the United States indicate that microbial water quality of aquifers is widely variable, which was a motivating factor behind the development of the “Ground Water Rule” that set new regulations and guidelines for monitoring and treatment of groundwater (USEPA 2006a, 2006b). Many