The study goal was to determine if on-site wastewater systems (OSWWS) installed in coastal areas were effective at reducing indicator bacteria densities before discharge to groundwater. Groundwater Escherichia coli (E. coli) densities and groundwater levels adjacent to 16 OSWWS in three different soil groups (sand, sandy loam, and sandy clay loam) were monitored and compared to background groundwater conditions on four occasions between March 2007 and February 2008 in coastal North Carolina. Groundwater beneath OSWWS had significantly (p≤0.05) lower densities of E. coli than septic tank effluent, but significantly higher densities of E. coli than background conditions for each soil type. Twenty three percent of all groundwater samples near OSWWS had E. coli densities that exceeded the EPA freshwater contact standards (single sample 235 cfu/100 mL) for surface waters. Groundwater E. coli densities near OSWWS were highest during shallow water table periods. The results indicate that increasing the required vertical separation distance from drainfield trenches to seasonal high water table could improve shallow groundwater quality.
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Research Article|
February 01 2011
Evaluation of on-site wastewater system Escherichia coli contributions to shallow groundwater in coastal North Carolina
C. P. Humphrey, Jr;
1Environmental Health Sciences Program, East Carolina University, 3408 Carol Belk Bldg., Greenville, NC 27858-4353. E-mail: [email protected]
E-mail: [email protected]
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M. A. O’Driscoll;
M. A. O’Driscoll
2Department of Geological Sciences, East Carolina University, 204 Graham Bldg., Greenville, NC 27858-4353. E-mail: [email protected]
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M. A. Zarate
M. A. Zarate
3Environmental Health Sciences Program, East Carolina University, Greenville, NC 27858-4353; currently with the Centers for Disease Control and Prevention, Atlanta, GA. 30341 USA E-mail: [email protected]
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Water Sci Technol (2011) 63 (4): 789–795.
Citation
C. P. Humphrey, M. A. O’Driscoll, M. A. Zarate; Evaluation of on-site wastewater system Escherichia coli contributions to shallow groundwater in coastal North Carolina. Water Sci Technol 1 February 2011; 63 (4): 789–795. doi: https://doi.org/10.2166/wst.2011.310
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