Sediment color tool for targeting arsenic-safe aquifers for the installation of shallow drinking water tubewells

• Published in: The Science of the total environment 2014-09, Vol.493, p.615-625
• Main Authors: Hossain, Mohammed, Bhattacharya, Prosun, Frape, Shaun K., Jacks, Gunnar, Islam, M. Mainul, Rahman, M. Moklesur, von Brömssen, Mattias, Hasan, M. Aziz, Ahmed, Kazi Matin
• Format: Article
• Language: English
• Subjects: Analysis methods; Applied sciences; Arsenic; Arsenic - analysis; Bangladesh; Color; Drinking Water - chemistry; Drinking water and swimming-pool water. Desalination; Environmental Monitoring - methods; Exact sciences and technology; Geologic Sediments - chemistry; Geologic Sediments - classification; Groundwater - chemistry; Groundwaters; Local driller; Natural water pollution; Pollution; Sediment color tool; Sustainable mitigation; Tubewell; Water Pollutants, Chemical - analysis; Water treatment and pollution; Water Wells
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2014.05.064

In rural Bangladesh, drinking water supply mostly comes from shallow hand tubewells installed manually by the local drillers, the main driving force in tubewell installation. This study was aimed at developing a sediment color tool on the basis of local driller's perception of sediment color, arsenic (As) concentration of tubewell waters and respective color of aquifer sediments. Laboratory analysis of 521 groundwater samples collected from 144 wells during 2009 to 2011 indicate that As concentrations in groundwater were generally higher in the black colored sediments with an average of 239μg/L. All 39 wells producing water from red sediments provide safe water following the Bangladesh drinking water standard for As (50μg/L) where mean and median values were less than the WHO guideline value of 10μg/L. Observations for off-white sediments were also quite similar. White sediments were rare and seemed to be less important for well installations at shallow depths. A total of 2240 sediment samples were collected at intervals of 1.5m down to depths of 100m at 15 locations spread over a 410km2 area in Matlab, Bangladesh and compared with the Munsell Color Chart with the purpose of direct comparison of sediment color in a consistent manner. All samples were assigned with Munsell Color and Munsell Code, which eventually led to identify 60 color shade varieties which were narrowed to four colors (black, white, off-white and red) as perceived and used by the local drillers. During the process of color grouping, participatory approach was considered taking the opinions of local drillers, technicians, and geologists into account. This simplified sediment color tool can be used conveniently during shallow tubewell installation and thus shows the potential for educating local drillers to target safe aquifers on the basis of the color characteristics of the sediments. [Display omitted] •More than 90% tubewells in Bangladesh are installed privately by the community.•Local drillers are the main driving force in tubewell installations.•Long term monitoring validated arsenic in water with respect to sediment color.•A sediment color tool is developed based on local driller’s color perception.•This tool would play a significant role to scale-up safe water access.