The fluoride which enters the hydrological system may, to a large extent, be traced back to volcanic activities
associated with rift formation and chemical weathering of volcanic rocks. The African Rift System is
dominated by alkaline base-rocks, and high-fluoride groundwater is a rule in the rift valley and the
surrounding areas. One of the areas exposed to high fluoride in water is Kitengela and as a result dental and
skeletal fluorosis are endemic in the town. There is an acute need for a simple and inexpensive methods for
defluoridation of water in the town.
The project evaluated the defluoridation of drinking water from Kitengela using clay soil. Seven borehole
water samples were obtained from Kitengela town for the defluoridation test. Fluoride sorbent clays from
Syokimau, Chepsion and Mwea were studied and used for batch defluoridation. The effect of pH, contact
time, particle size and fluoride concentration were examined. It was found that fluoride concentration
increased with borehole depths. Sun drying the clays reduced erosion during deflouridation and eased flow
of water in the defluoridation column. It was established that the pH of the soil was indicative of its fluoride
removal capacity. An increased pH value translated to an increase in the fluoride removal capacity.
Fluoride adsorption comparisons were made and the study revealed that Syokimau clay has a superior
capacity than others. Its average fluoride removal efficiency was 61% compared to 59% for Mwea clay and
40% for Chepsion clay. Syokimau clay emerged the suitable defluoridation medium.


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