Browsing by Author "Higini, Kalista"

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    Seasonal assessment of high fluoride waters and development of defluoridation method using various soils at maji ya Chai, Arusha, Tanzania
    (Unversity of Dar es Salaam, 2007) Higini, Kalista
    The problem of excessive fluoride in water supply has been noted in the Arusha part ofTanzania especially in Maji ya Chai ward where the study was conducted. The study was carried out to develop defluoridation method using various soils, to investigate seasonal impact on fluoride concentration and to assess the influence of major ions on excessive fluoride concentration from natural water sources. Water samples were collected from rivers, springs, boreholes, tap water and few from ponds in both dry and wet seasons. However, soils used for defluoridation were collected from North eastern part of Tanzania as well as Pugu in Dar es Salaam. Water sources at the study area are found to contain fluoride concentration up to 27.3 mg/I. Study shows that, fluoride concentrations increases with Na2+ and HCO3- and vice versa for Ca2+ due to bearing minerals and precipitation process. It was observed that fluoride concentration in some parts ofthe study areas is seasonally dependent. Data show that soil rich in bauxite have higher capacity in removing excessive fluoride from water than that rich in kaolinite in both types of soils activated soil has higher fluoride removal capacity than non-activated ones. At initial fluoride concentration of 5mg/I in water, soil rich in bauxite removes fluoride by 72.60%, while the one rich in kaolinite removes by 53%. The study also revealed that activated soil rich in bauxite has highest fluoride removal capacity at initial fluoride concentration of 5 mg / I and at low pH for higher fluoride concentration levels. Furthermore, the study showed that the defluoridation process is dependent on initial concentration of fluoride in raw alter, quantity of soil used, pH of the raw water and contact time it has been concluded that soil rich in bauxite is a good defluoridation agent under pH control.