title: Implications of fecal bacteria input from latrine-polluted ponds for wells in sandy aquifers.
abstract: Ponds receiving latrine effluents may serve as sources of fecal contamination to shallow aquifers tapped by millions of tube-wells in Bangladesh. To test this hypothesis, transects of monitoring wells radiating away from four ponds were installed in a shallow sandy aquifer underlying a densely populated village and monitored for 14 months. Two of the ponds extended to medium sand. Another pond was sited within silty sand and the last in silt. The fecal indicator bacterium E. coli was rarely detected along the transects during the dry season and was only detected near the ponds extending to medium sand up to 7 m away during the monsoon. A log-linear decline in E. coli and Bacteroidales concentrations with distance along the transects in the early monsoon indicates that ponds excavated in medium sand were the likely source of contamination. Spatial removal rates ranged from 0.5 to 1.3 log(10)/m. After the ponds were artificially filled with groundwater to simulate the impact of a rain storm, E. coli levels increased near a pond recently excavated in medium sand, but no others. These observations show that adjacent sediment grain-size and how recently a pond was excavated influence the how much fecal contamination ponds receiving latrine effluents contribute to neighboring groundwater.
authors.affiliation: Department of Earth and Planetary Sciences, The University of Tennessee, Knoxville, Tennessee 37996-1410, United States. 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: Md R
authors.initials: MR
authors.lastname: Huq
authors.forename: Jacob
authors.initials: J
authors.lastname: Mey
authors.forename: John E
authors.initials: JE
authors.lastname: Feighery
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Culligan
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Mailloux
authors.forename: Jie
authors.initials: J
authors.lastname: Zhuang
authors.forename: Veronica
authors.initials: V
authors.lastname: Escamilla
authors.forename: Michael
authors.initials: M
authors.lastname: Emch
authors.forename: Edmund
authors.initials: E
authors.lastname: Perfect
authors.forename: Gary S
authors.initials: GS
authors.lastname: Sayler
authors.forename: Kazi M
authors.initials: KM
authors.lastname: Ahmed
authors.forename: Alexander
authors.initials: A
authors.lastname: van Geen
mesh_terms: D001459:Bangladesh; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D004926:Escherichia coli / Q000302:isolation & purification*; D019015:Geologic Sediments; D010316:Particle Size; D012722:Sewage / Q000382:microbiology*; D014038:Toilet Facilities; D014881:Water Supply; D060986:Water Wells / Q000382:microbiology*
chemical_list: D012722:Sewage