Abstract

The objective of this study was to develop a rural domestic defluoridation technology for the removal of fluoride from groundwater using locally available raw bauxite. Drinking groundwater sample of high fluoride concentration (6.17 mg/L) was collected from a borehole in Machinga district of Southern Malawi where dental fluorosis is prevalent due to the high fluoride. Defluoridation of the water sample was done in a model domestic defluoridation unit in batch mode to optimize raw bauxite dosage and contact time. Sand and charcoal were used for water clarification. Optimum bauxite dosage and optimum contact time were determined as 0.150 kg/L and 15.0 min respectively. An optimum combined dosage of sand and charcoal for water clarification was found to be 0.720 kg/L. The specific safe water yield for this system was found to be 36.0 L/kg adsorbent. An empirical model of the form  where Y is the specific safe water yield, x is the height/cross sectional area ratio of a defluoridator is developed to show the significance of defluoridator design in defluoridation.

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