Comparison of low cost materials to remove fluoride from drinking water in Sri Lanka; Response to health problems associated with contiguous hydrogeochemistry

Considering medical geology, Chronic Kidney Disease (CKD), dental and skeletal fluorosis is emerging as major health problems in the dry zone of Sri Lanka. In the year of 2008, over 5,000 patients were under treatment for renal failure in the North Central Province. Large number of cases has been found with the dental fluorosis while few skeletal fluorosis is also reported. Recent research carried out in the CKD prevalent areas also demonstrated that there is a significant relationship between fluoride-rich areas and the high incidence of CKD. In some areas fluoride in drinking water reported as high as 9-10 ppm where the WHO maximum permissible limit is 1.5 ppm. Therefore, it is essential to remove excessive fluoride from water before drinking. This study was performed to investigate the effectiveness of low cost and locally available filter materials to be used easily in household filters. Batch experiments were carried out for different fluoride loadings (10, 20 and 50 ppm) and time for diverse adsorbents such as laterite, bricks, charcoal, serpentine, tile, quartz, marble and white clay balls (impure kaolinite) based on the adsorption technique. It was found that untreated charcoal and quartz have no effect on defluoridation and local bricks as well as marble demonstrated less defluoridation ability i.e. 28.83% and 12.7% respectively. White clay and laterite showed higher adsorption efficiency than tile chips and serpentinite. When consider adsorption amounts white clay, laterite and serpentinite exhibited 96.0%, 94.25% and 93.54% % respectively for 10 ppm initial concentration of fluoride. For the rest adsorbate loadings it showed similar behavior with more than 90 % adsorption. Most of the materials attend to equilibrium after 60 minutes. The presence of aluminium and iron oxides would place these materials on top of the better adsorbent list. Column experiments, effect of temperature on the adsorbents and modeling are under investigation for white clay, laterite and serpentinite.