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| Titel |
Installing arsenic-safe drinking water wells in Matlab, Bangladesh – A novel concept for sustainable mitigation |
| VerfasserIn |
Prosun Bhattacharya, Mohammed Hossain, Shaun K. Frape, Gunnar Jacks, K. Matin Uddin Ahmed, M. Aziz Hasan, Mattias von Brömssen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132952
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| Publikation (Nr.) |
 EGU/EGU2016-13507.pdf |
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| Zusammenfassung |
| Since the discovery of Arsenic (As) in Bangladesh groundwater in 1993, there has been a
limited success in mitigation and several millions of people are at health risk. Tubewell has
been recognized as widely accepted option due to its easy operation, almost no cost for
maintenance and the availability of year round water. Since a significant proportion of
shallow wells (usually < 80m) are at risk with As-contamination, deep wells are drilled to
depths of around 250 m as a mitigation option. Compared to safe water demand, the number
of deep wells is still very low, as the installation cost is beyond affordability of the local
community.
Hydrogeochemical characterization of shallow, intermediate deep and deep aquifer
systems were performed through monitoring of groundwater using depth-specific
piezometers (n=82) installed in 15 locations in Matlab area of Bangladesh. Monitoring was
done over a 3 year period (pre- and post-monsoon for 2009-2011 period). Results from
additional 87 existing drinking water supply tubewells were also considered for the
study. For the installation of shallow drinking water wells, one aim of this study was
to develop a sediment color tool on the basis of local driller’s color perception
of sediments (Black, White, Off-white and Red), As concentration of tubewell
waters and respective color of aquifer sediments. Average and median values of As,
less than the WHO guideline value of 10 μg/L observed from 39 wells installed in
red sands gave strong evidence that red sediments provide As-safe water. Arsenic
concentrations in more than 90% of the 66 shallow wells installed in black sands were
high with an average value of 239 μg/L. Therefore, it is recommended to avoid
installation of shallow wells in aquifers consisting of black sands. The use of Munsell
Color Chart for the characterization of 2240 sediment samples collected from each
of 1.5 m section up to a depth of 100 m from 15 locations spread over 410 km2
area led to identify 60 color shades. In the narrow down process, each shade was
eventually assigned with four colors through a participatory approach taking the
opinions of local drillers, technicians, and geologists into account. Comparison with
Munsell color rendered them distinctive from each other which reduce the risk for
misinterpretation of the sediment colors. This study shows the potential for educating
local drillers to identify and target safe aquifers in shallow horizons for tubewell
installation. This study also pioneered Intermediate Deep Aquifer (IDA) as a potential
source for As-safe and low Mn drinking water. Installation of 245 Intermediate Deep
Tubewells (IDTW) at a depth of 120 m provided promising results (99% As-safe and
91% low Mn) which supports the strategy of exploiting IDA as safe aquifers for
installation of drinking water wells almost at half of the deep tubewell installation
cost.
For scaling-up safe water access in a methodical way, this study also included social
mapping and this strategy is recommended for the relevant stakeholders in planning and
implementing safe tubewell installation. |
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