Development of a Bone Char-HAP Hybrid Filter System to Remove High Concentration of Fluoride in Groundwater and Its Application on a Field Study

More than 260 million people worldwide consume water containing fluoride concentrations exceeding 1.0 mg/L. In particular, tens of millions of residents in Ethiopia, Kenya, and Tanzania, located within the East African Rift Valley, are exposed to groundwater containing fluoride concentrations above 10 mg/L, posing serious health risks. In this study, a water treatment system integrating two adsorbents currently used in the region, bone char and hydroxyapatite (HAP), was developed to more effectively remove high concentrations of fluoride from local groundwater. Continuous-flow fixed-bed column experiments conducted at the laboratory scale demonstrated that the sequential application of bone char and HAP produced more than twice the treated water volume before reaching the World Health Organization (WHO) drinking water guideline value of 1.5 mg/L, compared with the use of either adsorbent alone. Based on these laboratory findings, the newly developed combined bone char–HAP filter was implemented in a rural village in Ethiopia. The installed system not only exhibited excellent fluoride removal performance, reducing the fluoride concentration of raw groundwater from 9.46 mg/L to 0.14 mg/L in the treated water, but also more than doubled the replacement interval of the adsorbents, thereby significantly increasing treatment capacity.In conclusion, the combined bone char–HAP filter developed in this study represents a promising and cost-effective solution for the efficient removal of high fluoride concentrations from groundwater in East Africa.