The Occurrence and Removal Possibilities of Fluoride in ArushaArea

Abstract

The main problem of the quality of water in Arusha and Arumeruareas is the high fluoride concentration both in surface and groundwaters. Water samples collected earlier and during this study indicated fluoride values exceeding the WHO limit of 1,5 mk/l though many of them were within the Tanzanian rural water standard, less than 8,0 mg/l. In these areas average fluoride values ranged from 0,9 to 6,8mg/l in the water sources now used for water supply. In Arusha town, out of the 8 spring sources investigated, 4 (50%) had average fluoride values exceeding 1,5 mg/l and out of the 25 boreholes investigated, 23 (92 %) had fluoride levelexceeding this limit. The rivers had average fluoride values ranging from 1,4 to 3,9 mg/l. In the distribution system at certain points in Arusha town fluoride values in water supply ranged from 2,6 to 4,0 mg/l as a result of dilution caused by mixing different water sources. The investigation for fluoride level in various water sources of Arumeru area showed the highest fluoride level in lakes. In Momela lakes the fluoride level was up to 690 mg/l. The average fluoride level in rivers ranged from 1,1 to 6,8mg/l and the exceptional cases were the Maji ya Chai and Engarenanyuki rivers which had high fluoride concentrations of up to 23 mg/l and 76 mg/l respectively. This is due to the formation of magadi salts at the riverbasins. Out of the 99 spring sources investigated in this area, 80 (81%) had average fluoride values above 1,5 mg/l and out of the 49 boreholes investigated, 33 (70 %) had the fluoride level above this value. Apart from the effects caused by fluoride in water, the foodstuffs taken by the people in the study area contribute to the addition of fluoride in the human body. This has given rise to serious diseases caused by excessfluoride in various parts of the area. These include knock knee, bow legs, severe pitting of the teeth, sober shin and fixed kyphosis of stiffness of the spine. There is an immediate need to find locally available materials for fluoride removal because there are problems of getting the imported chemicals for the purpose. Experiments conducted during the thesis period indicated a possibility of using locally available materials like limestoneas filter media for fluoride removal. /Kir09