SEZ - Qualified well construction
In cooperation with the Institute of Geosciences at Heidelberg University and the local Department of Public Health Engineering (DPHE), existing wells in the vicinity of the city of Nabiganj (northeastern Bangladesh) were sampled as part of a comprehensive survey and analyzed using simple methods (arsenic field test, electrical conductivity measurement, and collection of a water sample for determining iron content). At the same time, samples from the same wells were collected for professional analysis at Heidelberg University.
By comparing four sites, we concluded that electrical conductivity is a suitable tool for assessing groundwater quality, as it is positively correlated with arsenic concentration. Some exceptions were extremely high conductivity values, which indicated interaction with wastewater or generally poor water quality. For the bottle tests, a plastic bottle was filled with water and left undisturbed for 24 hours in order to examine iron precipitation in terms of color and consistency. We found that iron precipitates in water from Bangladesh react differently and that, in some cases, the flocs formed settle again quickly after shaking.
This creates sustainable opportunities for arsenic filtration in sand filters at these sites, as offered and maintained by AGAPE e.V. as an alternative to deep wells.
The project was funded by the Stiftung Entwicklungszusammenarbeit (SEZ) through state funds provided by Baden-Württemberg.
In a second step, deep wells in the same area were investigated using geophysical methods (gamma logging). Since no sediment logs are prepared during drilling, this depth profile can provide important insights into the subsurface layers. We also found that wells located outside settlement areas tend to have lower arsenic concentrations than those situated near houses or ponds. The reasons for this are still being investigated, and the research will continue shortly.
The project was carried out in cooperation with the Institute of Geosciences at Heidelberg University and was funded by the State of Baden-Württemberg through the Foundation for Development Cooperation (SEZ).
