Spatial Distribution of Fluoride Concentration in Drinking Water Sources in Northern Tanzania

摘要

Study on Fluoride concentration levels and spatial distribution was carried out in a total of 366 drinking water sources in Arusha city, Ngorongoro, Arumeru, Monduli, Karatu, Meru, and Longido districts in Arusha Region, Northern Tanzania. The main objective of the study was to map occurrence and level of Fluoride concentrations in the existing and potential sources of drinking water supply in the case study areas. Determination of Fluoride concentration was analysed by electrochemical methods using a Fluoride ion selective electrode. The obtained results indicate that out of the 22 water sources assessedin Arusha city, only 14 (63%) meets the recommended Fluoride concentration level (4 mg/L) for drinking water standards of Tanzania. In Karatu district out of the 22 water sources assessed, 9 sources (41%) do not meet the Tanzania standards of Fluoride concentration levels in drinking water sources, while in Longido all 18 boreholes had Fluoride concentration levels above the recommended Tanzania standards. Out of the 11 assessed spring water sources, 6 (55%) had concentration above the recommend levels. However, Fluoride concentrations in all rivers in Longido district were found to be within the allowable standards. In Monduli district 2 dug wells had Fluoride concentration between 0.34 and 1.0 mg/L, respectively. Fluoride concentration in Lake Manyara was found to be as high as 18 mg/L, which is far beyond the recommended concentration level in Tanzania as well as by World Health Organization (WHO). Fluoride concentrations in almost all spring water sources in Monduli district have Fluoride concentrations allowable both by Tanzania and WHO standards. In Meru district the percentage of water sources with Fluoride concentration within the allowable levels in Tanzania and can thus can be tapped for safe water supply are boreholes 64.3%, springs 66.7%, shallow wells 25.7% and rivers 71.5%. In Arusha District springs constitute the main water source. Out of these 77% have Fluoride concentration within Tanzania allowable standards. As for Ngorongoro out of 51 water sources assessed only 4 have Fluoride concentration above 4.0 mg/L, suggesting a major leeway and flexibility in terms of selection of water supply sources in this district. Results of this study indicate a challenging situation in terms of selection of source of safe water supply in Arusha city and Meru district as many of their water sources have Fluoride concentration above the permissible levels in Tanzania. However, the situation is different in Karatu, Longido and Monduli, Arumeru and Ngorongoro districts where substantial water sources have Fluoride concentration within levels acceptable for drinking water supply in Tanzania.