Chebude, Yonas (PhD)Fidel, Kessy (PhD)Jackson, Magori2021-09-162023-11-182021-09-162023-11-182021-06-26http://etd.aau.edu.et/handle/12345678/27918The coexisting fluoride and arsenic in the groundwater sources of drinking water has been threat to the general public health worldwide and in particular to the East African Rift Valley (EARV). The use of bone char and Nalgonda technique for defluoridation face rejection by the users in the area due to cultural beliefs and foul smell they produce. New, cost-effective method for removal of fluoride and/ or arsenic is therefore required. In this study the electrocoagulation process using hybrid aluminum-iron electrode was optimized and evaluated for the removal of arsenic and fluoride from water. At the optimized operation parameter of 9.90 mAcm-2, pH 7.5; the hybrid Al-Fe EC reduced 16 mg/L fluoride and 200 μg/L arsenic to 1.12 mg/L and 9.60 μg/L, respectively in 50 minutes with an operation cost estimated to 0.99 $/m3. Moreover, the study investigated the effects of co-existing ions in water on the performance of Al-Fe EC and found that Ca2+ (0.5-100 mg/L) enhanced F- removal, while SO4 2- (> 80 mg/L) and NO3 - (> 75 mg/L) suppressed F- removal. On the other hand, NO3 - (0.5-100 mg/L), SO4 2- (> 50 mg/L), Mg2+ (> 50 mg/L), and Ca2+ (> 50 mg/L) reduced As3+ removal. The combination of Mg2+ (˂ 70 mg/L) and Ca2+ appears to increase the fluoride removal, while the combination of other ions had antagonistic effects on the removal of both F- and As3+. Carbonates showed an insignificant influence on the removal of both pollutants. The effect of co-existing ions on the performance of hybrid Al-Fe EC was found to depend on the type and concentration of individual co-ion. The last objective reports on the adsorption isotherm and kinetic of arsenic and/or fluoride. Adsorption of fluoride and arsenic followed both Freundlich and Langmuir models. The adsorption processes for fluoride and arsenic were spontaneous and physical in nature with monolayer maximum adsorption capacities of 76.36 mg/g and 1.14 mg/g, respectively in single systems. In a binary mixture adsorption capacity of arsenic was 0.40 mg/g while that of fluoride was 75.60 mg/g. Moreover, the kinetic of fluoride and or arsenic removal followed pseudo second order model. The removal of fluoride and arsenic were through ionic exchange and electrostatic attraction, respectively. Meanwhile, a real groundwater (F- = 22 mg/L) and simulated groundwater (As3+ = 0.22 mg/L and F- = 7.6 mg/L), have also been treated successfully. The optimized Al-Fe EC upon scale up can be used for the remediation of fluoride and/or arsenic from contaminated groundwater in EARV.enSimultaneous RemovalFluorideArsenic In Drinking WaterElectrocoagulationTechnology Using Hybrid Al-FeElectrodesThesis