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Fecal Contamination of Shallow Tubewells in Bangladesh Inversely Related to Arsenic

van Geen, Alexander; Ahmed, Kazi Matin; Akita, Yasuyuki; Alam, Md. Jahangir; Culligan, Patricia J.; Emch, Michael; Escamilla, Veronica; Feighery, John; Ferguson, Andrew S.; Knappett, Peter; Layton, Alice C.; Mailloux, Brian J.; McKay, Larry D.; Mey IV, Jacob L.; Serre, Marc L.; Streatfield, P. Kim; Wu, Jianyong; Yunus, Mohammad

The health risks of As exposure due to the installation of millions of shallow tubewells in the Bengal Basin are known, but fecal contamination of shallow aquifers has not systematically been examined. This could be a source of concern in densely populated areas with poor sanitation because the hydraulic travel time from surface water bodies to shallow wells that are low in As was previously shown to be considerably shorter than for shallow wells that are high in As. In this study, 125 tubewells 6-36 m deep were sampled in duplicate for 18 months to quantify the presence of the fecal indicator Escherichia coli. On any given month, E. coli was detected at levels exceeding 1 most probable number per 100 mL in 19-64% of all shallow tubewells, with a higher proportion typically following periods of heavy rainfall. The frequency of E. coli detection averaged over a year was found to increase with population surrounding a well and decrease with the As content of a well, most likely because of downward transport of E. coli associated with local recharge. The health implications of higher fecal contamination of shallow tubewells, to which millions of households in Bangladesh have switched in order to reduce their exposure to As, need to be evaluated.

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Published In
Environmental Science & Technology
Publisher DOI
https://doi.org/10.1021/es103192b
Volume
45
Issue
4
Pages
1199 - 1205
Academic Units
Civil Engineering and Engineering Mechanics

Notes

Reprinted with permission from Environmental Science & Technology. Copyright 2011 American Chemical Society.

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