Assessment of Fluoride Levels in Different Water Sources in Lower Region of Bomet County, Kenya and Remediation Using Moringa oleifera Seed Cake

Abstract

The use of water with high fluoride concentration poses a health threat to millions of people around the world, therefore there is need to determine the levels of fluoride in water for domestic use and to find ways of removing these ions from water. The objectives of the study were to assess the levels of fluoride in the water sources in the lower region of Bomet County and to determine remediation effectiveness of moringa oleifera seed cake. Water samples were collected in wet season in the month of April 2011 and dry season in the month of January 2012 from different water sources. The samples were analyzed for pH, Total dissolved solids, conductivity, Na+, K+, Mg2+, Ca2+, F- and HCO3-. Ion selective electrode method, Thermo-Orion 96-09 model was used for the fluoride determination in the laboratory. Flame photometer was used for analysis of Na+ and K+ ions and Flame atomic absorption spectrometry was for Mg2+ and Ca2+ respectively. Bicarbonates were analyzed by standard method 920.194 (titration) approved by the Association of Official Analytical Chemists (AOAC). Data obtained was subjected to Microsoft Excel and analysis of variance. For both dry and wet seasons, mean concentrations for all selected physico-chemical parameters were within the KEBS and WHO permissible limits except for fluorides in some sources (borehole and water pan water) were found to be above 1.5 mg/L permissible limit. Moringa oleifera seed cake was studied as an alternative adsorbent for removal of fluoride from aqueous solution. Biosorption kinetic data fitted well with pseudo-second-order kinetic model (R2, 0.9805). The biosorption isotherms for the biosorbent fitted better with the Langmuir isotherm model than Freundlich isotherm model and therefore adsorption is limited to the formation of a monolayer. In conclusion, the study revealed that Moringa oleifera seed powder is an efficient biosorbent for removal of fluoride from aqueous solution.