Fluoride in African groundwater: occurrence and mitigation

Fluoride in groundwater has both natural and anthropogenic sources. Fluoride bearing minerals, volcanic gases and various industrial and agricultural activities can contribute to high concentrations. High intake of fluoride from drinking water is the main cause of fluorosis and may lead to many other health problems. Problems usually start with intake of water containing more that 1,5 mg/l of fluoride (WHO guideline). Many water supplies in Africa are contaminated by much higher concentrations of fluoride. Alternative water sources, improvement of the nutritional status of population at risks and appropriate defluoridation methods are the potential options for mitigation of high fluoride effects. Regarding the defluoridation, there is not a universal method which is appropriate under all social, financial, environmental and technical conditions.
This paper assesses the probability of occurrence of excessive fluoride concentrations in African groundwater. The assessment combines available information from reported cases with knowledge on geochemical behavior of fluorine in different geographical settings, defined by geological and climatic conditions. Better understanding of the distribution pattern can provide valuable information for design of new water supplies, articularly those located in Precambrian Basement regions or volcanic areas of the African Rift system. For benefit of existing water supplies already affected by high fluoride concentrations, an overview of available defluoridation techniques is presented in terms of efficiency, required technology and costs. Simple decision trees are used to provide guidelines for selection of an appropriate Guidelines for Community Groundwater Supply and Protection in Africa removal method. Such guidelines are easily understandable to a “problem owner” seeking practical solution for improvement of his/her groundwater resource.