Excessive and undesirable level of fluoride in drinking water supplies is a major problem in thernRift Valley of Ethiopia. It has been reported that people in the Rift Valley of Ethiopia arernconsuming water up to 33 mg L-1 of fluoride. The WHO has set 1.5 mg L-1 as the maximumrnpermissible limit for fluoride in potable water. Sustained intake of fluoride beyond this limit canrncause dental or skeletal fluorosis, which is a chronic disease manifested by mottling of teeth inrnmild cases, softening of bones and neurological damage in severe cases, therefore adequaternmeasures for the reduction of the level are important.rnIt is also expected that the fluoride concentration may increase mainly because of the excessivernutilization of ground water as these area are characterized by water scarcity. In areas wherernalternative water sources are not available, physical or chemical treatment of water is the bestrnoption to control fluorosis. The methods of fluoride removal used by industrialized countriesrnrequire more technical support for operation and maintenance than is possible in the rural areasrnof developing countries.rn- viii -rnIn this study, the removal of fluoride using aluminium hydroxide was studied in a fixed bedrncolumn system. The Bed Depth Service Time design model, Empty Bed Residence Time andrnThomas model were used to analyze the performance of the column and the effect of the differentrnoperating variables such as bed depth, flow rate and initial concentration were tested on thesernsimplified fixed bed design models. Desorption experiments were conducted to evaluate thernpossibilities of regeneration and reuse of the media. The effects of co-existing ions on thernadsorption capacity of aluminium hydroxide were also investigated in batch mode.rnThe breakthrough curves for the adsorption of fluoride on to aluminium hydroxide confirmed thatrnthe breakthrough volume and breakthrough time were decreased with increasing flow rate andrninitial fluoride concentration or decreasing bed depth. The data estimated from bed depth servicerntime model showed that the adsorption capacity (No) of the adsorbent were found to be 24.07,rn25.79 and 12.7 mg g-1 for 12, 23 and 40 mL min-1 flow rate, respectively. The operating linernseems flatten and no significant reduction in adsorbent exhaustion rate is gained with contactrntime greater than about 3, 6 and 7 min for 40, 23 and 12 mL min-1 flow rates, respectively, withrnthe corresponding usage rate of 2.2, 0.9 and 1.3 g L-1. The optimum dose for batch system wasrn1.6 g L-1 and it is close to the adsorbent exhaustion rate of 12 mL min-1. The application ofrnThomas model has showed that the adsorption capacity is strongly dependent on the flow rate,rninitial fluoride concentration, and bed depth and is greater under conditions of a lowerrnconcentration of fluoride, lower flow rate and higher bed depth. And the Thomas rate constantrndecreases with increasing bed depth, decreasing initial concentration, and flow rate. Resultsrnconcerning the effects of anions on the adsorption of fluoride on to the aluminium hydroxidernshowed that Cl- and SO4rn2- have very little effect on the fluoride removal capacity of adsorbent butrnHCO3rn- and PO4rn3- had a profound effect on the removal capacity of the adsorbent.rnHence it is concluded that using granular aluminium hydroxide as an adsorbent for fluoridernremoval in a fixed-bed adsorption process is feasible.rnKey words: Fluoride, Adsorption, Breakthrough, Fixed-bed column, Aluminium hydroxide, Bedrndepth service time, Empty bed residence time