Hand-pump subsurface arsenic removal (SAR) has been investigated in rural Bangladesh with different groundwater conditions and intermittent operation modes. Multiple injection-abstraction cycles were performed after injection of 1 m3 of aerated water. From these experiments it can be concluded that hand-pump SAR, in the traditional injection-abstraction design, does not provide drinking water below the WHO arsenic guideline of 10 μg/L. Results show that arsenic removal was not enhanced by: (i) injection of O2-rich water, (ii) higher Fe:As ratios in the groundwater, or by (iii) multiple injection-abstraction cycles, i.e. at location 1, the breakthrough occurred at abstraction-injection ratios of Va/Vi = 2, for cycle 23. It is proposed that dissolved organic carbon (DOC), bicarbonate and phosphate have a significant effect on the arsenic adsorption process. However, iron removal was very efficient and abstraction-injection ratios increased within successive cycles, with Va/Vi > 8 for cycle 23. Furthermore, intermittent operation reduced arsenic concentrations after stop and restart, suggesting insufficient contact time between soluble arsenic and oxidized iron surfaces around the tube well.
Hand-pump subsurface arsenic removal: the effect of groundwater conditions and intermittent operation
S. C. Borges Freitas, D. van Halem, M. M. Rahman, J. Q. J. C. Verberk, A. B. M. Badruzzaman, W. G. J. van der Meer; Hand-pump subsurface arsenic removal: the effect of groundwater conditions and intermittent operation. Water Supply 1 February 2014; 14 (1): 119–126. doi: https://doi.org/10.2166/ws.2013.180
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