title: Safe distances between groundwater-based water wells and pit latrines at different hydrogeological conditions in the Ganges Atrai floodplains of Bangladesh.
abstract: Groundwater drawn from shallow tubewells in Bangladesh is often polluted by nearby pit latrines, which are commonly used toilets in rural and sub-urban areas of the country.
  
  
  
  To determine the minimum safe distance of a tubewell from a pit latrine in different hydrogeological conditions of Bangladesh, 20 monitoring wells were installed at three study sites (Manda, Mohanpur and Bagmara) with the vertical and horizontal distances ranging from 18-47 to 2-15 m, respectively. Water samples were collected three times in three seasons and tested for faecal coliforms (FC) and faecal streptococci (FS) as indicators of contamination. Soil samples were analysed for texture, bulk density and hydraulic conductivity following standard procedures. Sediment samples were collected to prepare lithological logs.
  
  
  
  When the shallow aquifers at one of the three sites (Mohanpur) were overlained by 18-23-m-thick aquitards, the groundwater of the monitoring wells was found contaminated with a lateral and vertical distances of 2 and 31 m, respectively. However, where the aquitard was only 9 m thick, contamination was found up to lateral and vertical distances of 4.5 and 40.5 m, respectively. The soil textures of all the sites were mainly composed of loam and sandy loam. The hydraulic conductivities in the first aquifer at Manda, Mohanpur and Bagmara were 5.2-7.3, 8.2 and 1.4-15.7 m/h, respectively.
  
  
  
  The results showed that the safe distance from the tubewell to the pit latrine varied from site to site depending on the horizontal and vertical distances of the tubewell as well as hydrogeological conditions of a particular area.
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh. sislam@icddrb.org.|Environmental Microbiology Laboratory, Laboratory Sciences and Services Division, icddr,b, GPO Box-128, Dhaka, 1000, Bangladesh. sislam@icddrb.org.
authors.forename: M Sirajul
authors.initials: MS
authors.lastname: Islam
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
authors.forename: Zahid Hayat
authors.initials: ZH
authors.lastname: Mahmud
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
authors.forename: M Shafiqul
authors.initials: MS
authors.lastname: Islam
authors.affiliation: Dhaka University of Engineering and Technology, Gazipur, Bangladesh.
authors.forename: Ganesh Chandra
authors.initials: GC
authors.lastname: Saha
authors.affiliation: Hydrogeology and Environmental Geology Section, Department of Geology, University of Dhaka, Dhaka, 1000, Bangladesh.|Directorate of Groundwater Hydrology, Bangladesh Water Development Board, Dhaka, 1205, Bangladesh.
authors.forename: Anwar
authors.initials: A
authors.lastname: Zahid
authors.affiliation: Department of Soil, Water and Environment, University of Dhaka, Dhaka, 1000, Bangladesh.
authors.forename: Ahm Zulfiquar
authors.initials: AZ
authors.lastname: Ali
authors.affiliation: Hydrogeology and Environmental Geology Section, Department of Geology, University of Dhaka, Dhaka, 1000, Bangladesh.
authors.forename: M Qumrul
authors.initials: MQ
authors.lastname: Hassan
authors.affiliation: WaterAid Bangladesh, Banani, Dhaka, 1213, Bangladesh.
authors.forename: Khairul
authors.initials: K
authors.lastname: Islam
authors.affiliation: WaterAid Bangladesh, Banani, Dhaka, 1213, Bangladesh.
authors.forename: Hasin
authors.initials: H
authors.lastname: Jahan
authors.affiliation: Village Education Resource Center, Savar, Dhaka, 1340, Bangladesh.
authors.forename: Yakub
authors.initials: Y
authors.lastname: Hossain
authors.affiliation: Village Education Resource Center, Savar, Dhaka, 1340, Bangladesh.
authors.forename: M Masud
authors.initials: MM
authors.lastname: Hasan
authors.affiliation: London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Sandy
authors.initials: S
authors.lastname: Cairncross
authors.affiliation: WaterAid, London, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Carter
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Luby
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Cravioto
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.|Department of Medical Microbiology and Infectious Diseases, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Hubert Ph
authors.initials: HP
authors.lastname: Endtz
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
authors.forename: Shah M
authors.initials: SM
authors.lastname: Faruque
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, 1212, Bangladesh.
authors.forename: John D
authors.initials: JD
authors.lastname: Clemens
mesh_terms: D001459:Bangladesh; D004784:Environmental Monitoring; D055593:Geological Phenomena; D060587:Groundwater; D006801:Humans; D014038:Toilet Facilities; D014881:Water Supply; D060986:Water Wells; D053833:Wetlands
keywords: Bacterial contamination; Hydrogeological condition; Pit latrine; Safe distance; Tubewells