Adsorption of iron and manganese by locally available filter media in water treatment

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Groundwater is the most important source of water supply for rural communities in Ghana. However, in some localities, the quality of groundwater is affected by the occurrence of manganese and iron above acceptable levels. The presence of iron and manganese is therefore a limiting factor in the selection of groundwater resources. The locally available filter media namely coated sand; charcoal and laterite were investigated for removal of iron and manganese from water in this study. The adsorption of iron and manganese were carried out under anaerobic condition and pH was also varied between 6 and 7. Freundlich adsorption isotherm was use to determine the adsorption capacity and adsorption bond of iron by coated sand and charcoal. The results of the study show that charcoal has higher adsorption capacity of iron and manganese than that of coated sand within a period of 3 hours. However beyond 3 hours, the charcoal showed seemingly adsorption-desorption trend, which may be due to the presence of calcium oxide on its surface while this latter trend was not shown by coated sand. Laterite was however, also relatively good adsorbent for iron and manganese. For a unit mass of adsorbent, 0.0775mg and 0.0836mg of iron and manganese were adsorbed respectively. The laterite however, disintegrated in solution forming suspension. This phenomenon was traced to presence of clay materials in the laterite hence; it cannot be use as a filter media to treat groundwater in its raw state. The variation of pH however, had slight influence on the adsorption of iron and manganese by charcoal but pH of 6.5 is best for the removal of iron by charcoal. The adsorption was found to conform to Freundlich isotherm for charcoal and coated sand. The result further revealed that charcoal has a higher adsorption capacity and adsorption bond compared to coated sand.
A Thesis submitted to The Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, In Partial Fulfillment of the Requirement for the Award of the Degree of Master of Science in Water Supply and Environmental Sanitation, 2003