Use of Activated Red Clay Soil from Kiteto District, Tanzania, as a Remedial Method for High Fluoride Levels in Drinking Water

Abstract

The fluoride levels in the water samples were determined potentiometrically using a fluoride ion selective electrode. Different experiments on remediation of fluoride containing water with activated clay soil were carried out. Studies on effect of calcination temperature on activation of clay, minimum amount of calcinated clay soil giving optimum defluoridation, effect of contact time for optimal defluoridation and reusing activated soil for defluoridation of water were performed. The best activation temperature for the red clay soil from Kiteto District was found to be 700 °C. For best results, the clay should be heated at this temperature for 3 hours, allowed to cool then used. The optimum water defluoridation contact time was found to be 8 hours. It was established that for 100 mL of fluoridated water with 4.59 mg-F L-1, a minimum of 10 g of calcinated clay soil was required to reduce the concentration of fluoride ions to ≤1.1 mg-F L-1 which is well below the WHO recommended level of 1.5 mg-F L-1 for potable drinking water. The results also showed that the activated red clay soil can be repeatedly dried and re-used for the defluoridation process for a maximum of four times. It is recommended that the local red clay soil properly activated as described be used for the defluoridation of drinking water from Kiteto district, Tanzania. Investigation of possible usage of the activated clay soil for defluoridation of drinking water of other areas in the country is advocated.