Characterization of nonpoint source microbial contamination in an urbanizing watershed serving as a municipal water supply

Abstract

Inland watersheds in the southeastern United States are transitioning from agricultural and forested land uses to urban and exurban uses at a rate greater than the national average. This study sampled creeks representing a variety of land use factors in a rapidly urbanizing watershed that also serves as a drinking water supply. Samples were collected bimonthly under dry-weather conditions and four times during each of three storm events and assessed for microbial indicators of water quality. Concentrations of fecal indicator bacteria (FIB) including fecal coliforms and Escherichia coli were measured using standard membrane filtration techniques. Results showed that FIB concentrations varied between 10(0) and 10(4) colony forming units (CFU) per 100 mL. An analysis of variance (ANOVA) showed that FIB were generally higher in more developed watersheds (p < 0.01). Concentrations were also significantly greater during storm events than during dry-weather conditions (p < 0.02), although concentrations demonstrated both intra and inter-storm variability. These results indicate that the magnitude of microbial contamination is influenced by intensity of watershed development, streamflow and antecedent precipitation. Dry-weather FIB loads showed considerable seasonal variation, but the average storm event delivered contaminant loads equivalent to months of dry-weather loading. Analysis of intra-storm loading patterns provided little evidence to support "first-flush" loading of either FIB, results that are consistent with environmental reservoirs of FIB. These findings demonstrate that single sampling monitoring efforts are inadequate to capture the variability of microbial contaminants in a watershed, particularly if sampling is conducted during dry weather. This study also helps to identify timing and conditions for public health vulnerabilities, and for effective management interventions.

WITHDRAWN: Development of EMC-based empirical model for estimating spatial distribution of pollutant loads and its application in rural areas of Korea

“…For instance, agricultural sources are responsible for impairment of more than one-half of the rivers and lakes in the United States (USEPA, 2003;Rowny and Stewart, 2012). The causes and processes involved in the problems of nonpoint Simple methods are used to provide quick and easy identification of critical pollutant sources in a watershed, which are widely used for nonpoint source pollution management in small rural watersheds due to their simplicity and practicality (Shrestha et al, 2008;Shen et al, 2012).…”

Restructuring of the Aquatic Bacterial Community by Hydric Dynamics Associated with Superstorm Sandy

“…Previous studies have linked storm events to increases in fecal indicator bacteria (FIB) concentrations and turbidity (23,24) as well as decreases in general water quality (2,25). Various microbial source-tracking methods have been used in an attempt to track and quantify sources of fecal contamination in multiuse watersheds; however, research suggests these methods are inadequate at predicting and quantifying risk (26)(27)(28).…”

The influence of industrial and agricultural waste on water quality in the Água Boa stream (Dourados, Mato Grosso do Sul, Brazil)

“…In the USA, thermotolerant coliforms are the most widely used microbial indicators for monitoring watercourses, although the presence of E. coli is becoming more common; both measures of bacterial quantification from fecal statements can be used as indicators of contamination in surface and underground water (Rowny and Stewart 2012). These measures are also being adopted by current resolutions and ordinances in Brazil, in order to control outbreaks of waterborne disease.…”

“…The microbiological analyses include coliforms, Escherichia coli, Salmonella spp., and Pseudomonas spp. (Rowny and Stewart 2012;Kittinger et al 2013), and the chlorophyll a extraction of biological parameters (Siqueira and Rodrigues 2009).…”