title: Unsealed tubewells lead to increased fecal contamination of drinking water.
abstract: Bangladesh is underlain by shallow aquifers in which millions of drinking water wells are emplaced without annular seals. Fecal contamination has been widely detected in private tubewells. To evaluate the impact of well construction on microbial water quality 35 private tubewells (11 with intact cement platforms, 19 without) and 17 monitoring wells (11 with the annulus sealed with cement, six unsealed) were monitored for culturable Escherichia coli over 18 months. Additionally, two 'snapshot' sampling events were performed on a subset of wells during late-dry and early-wet seasons, wherein the fecal indicator bacteria (FIB) E. coli, Bacteroidales and the pathogenicity genes eltA (enterotoxigenic E. coli; ETEC), ipaH (Shigella) and 40/41 hexon (adenovirus) were detected using quantitative polymerase chain reaction (qPCR). No difference in E. coli detection frequency was found between tubewells with and without platforms. Unsealed private wells, however, contained culturable E. coli more frequently and higher concentrations of FIB than sealed monitoring wells (p < 0.05), suggestive of rapid downward flow along unsealed annuli. As a group the pathogens ETEC, Shigella and adenovirus were detected more frequently (10/22) during the wet season than the dry season (2/20). This suggests proper sealing of private tubewell annuli may lead to substantial improvements in microbial drinking water quality.
authors.affiliation: Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA. pknappet@utk.edu
authors.forename: Peter S K
authors.initials: PS
authors.lastname: Knappett
authors.forename: Larry D
authors.initials: LD
authors.lastname: McKay
authors.forename: Alice
authors.initials: A
authors.lastname: Layton
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Williams
authors.forename: Md J
authors.initials: MJ
authors.lastname: Alam
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Mailloux
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Ferguson
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Culligan
authors.forename: Marc L
authors.initials: ML
authors.lastname: Serre
authors.forename: Michael
authors.initials: M
authors.lastname: Emch
authors.forename: Kazi M
authors.initials: KM
authors.lastname: Ahmed
authors.forename: Gary S
authors.initials: GS
authors.lastname: Sayler
authors.forename: Alexander
authors.initials: A
authors.lastname: van Geen
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics; D001459:Bangladesh; D036022:Capsid Proteins / Q000235:genetics; D060766:Drinking Water / Q000382:microbiology; D054307:Enterotoxigenic Escherichia coli / Q000235:genetics / Q000302:isolation & purification; D004784:Environmental Monitoring / Q000379:methods*; D029968:Escherichia coli Proteins / Q000235:genetics; D005243:Feces / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012760:Shigella / Q000235:genetics / Q000302:isolation & purification; D060753:Water Quality; D060986:Water Wells / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D036022:Capsid Proteins; D060766:Drinking Water; D029968:Escherichia coli Proteins; C018315:hexon capsid protein, Adenovirus