Developing a Systems and Community-based Approach for Removing Excess Fluoride from Drinking Water in Rural Northern Ghana
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Excess fluoride in drinking water is a serious health risk in many parts of the world – particularly in developing countries. Unfortunately, removing excess fluoride from drinking water can be costly and, as a result, beyond the capacity of many poor communities. The health impacts of those who consume high fluoride water over several years range from mild dental fluorosis, which is cosmetic, to crippling skeletal fluorosis, which is disabling. This research addresses the problem of dental fluorosis in an area of northern Ghana with pockets of high fluoride groundwater, which is the primary source of drinking water. It investigates the viability of using laterite collected in the study area and Ghanaian bauxite, for use in low-cost, small-scale fluoride adsorption filters. It also considers whether activated alumina would be a more appropriate sorbent, though the cost would be notably higher since it must be purchased and imported. The possibility of delivering alternative, untreated low fluoride water to fluoridic areas is evaluated as well. In addition to addressing the ongoing challenge of providing clean and reliable sources of drinking water in rural northern Ghana, this research documents the distribution of dental fluorosis in the study area and estimates daily fluoride intake from drinking water and food, in order to determine whether the World Health Organization (WHO) recommended limit of 1.5 mg L-1 for fluoride in drinking water is appropriate for Ghana, which is hot year-round and where water consumption is expected to be high.The laboratory results indicate that, at the pH of the local groundwater (~7) and equal sorbent-to-solution ratios of 6.67 g L-1, activated alumina is notably better at adsorbing fluoride than bauxite or laterite, and bauxite is slightly better than laterite. Activated alumina has the advantage of a high surface area and high fluoride adsorption at pH 6-7. Bauxite is a very good sorbent per unit area but is limited by a low surface area and adsorbs fluoride best at pH <6. Laterite has higher surface area than bauxite but, due to its mineralogy, adsorbs best at pH <4.5. The field data collected in the study area identified communities with high fluoride (3.1-4.5 mg L-1) and low fluoride (<0.5 mg L-1) groundwater. Bongo granite is the source of groundwater fluoride, and concentrations decrease with distance from granitic areas. The low fluoride areas may be good locations for collecting groundwater and piping to communities with high fluoride groundwater. Survey data indicate that the WHO recommended fluoride limit of 1.5 mg L-1 is too high for Ghana, due to high water intake. But when considering that providing low fluoride water is not cost-free, the WHO recommended limit is currently acceptable for older children and adults. However children under 6-8 years need a limit <1.0 mg L-1 (ideally 0.6 mg L-1), and even lower in the first two years of life, since they are the most vulnerable to dental fluorosis. The survey results also show that only 24% of participants understand the cause of damaged teeth. Therefore, an aggressive long-term educational program is needed along with providing low fluoride water, in order to help affected communities understand the importance of drinking treated or alternative sources of low fluoride water.