Defluoridation of Drinking Water Using Appropriate Sorption Technologies

Fluorine is an element commonly found in the atmosphere, soil and water as the fluoride ion. Many sources of water around the world, particularly ground water, face high levels of fluoride due to natural weathering of fluoride laden rocks, and increasingly from industrial pollution. In most cases, the main exposure that people have to fluoride is through drinking water, but it also can come from food or other sources. The level of exposure will depend on the concentration of fluoride in the water as well as other factors such as climatic conditions which inform drinking habits. As children develop, they require fluoride to support tissue growth, especially with respect to teeth and bones, and to prevent dental caries. The World Health Organization recommends that fluoride levels be 1.5 mg/L in drinking water sources, to be adjusted depending on the region. In excess amounts, fluoride can cause dental fluorosis or debilitating skeletal fluorosis, along with other health concerns. In over 20 countries fluoride is encountered in high concentrations, resulting in millions of people suffering from fluorosis.Several defluoridation technologies have been developed and researched. Some are suited for centralized water supply schemes permissive to higher capital costs and continuous high flows of water, while others can be suited for use at the community or household level. The categories of defluoridation technologies include sorption, flocculation and precipitation, ion exchange and filtration. When considering appropriate defluoridation technologies for fluoride plagued communities in developing countries, one must consider criteria such as affordability, ease of use, and local availability materials. The use of adsorbents for the removal of fluoride can be effective as there are a variety of materials which can be used, the most popular of which are activated alumina and activated carbon. There are also earthen materials, plant based materials and bone char materials. Each has its own optimal performance conditions, and may have drawbacks in terms of availability, regeneration of adsorbent or sludge production. More field research into the practicability and efficacy of each technology will help inform the options communities have to prevent fluorosis and protect teeth from caries.