Browsing by Author "Mjengera, Hassani Juma"

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    Optimisation of bone char filter column for defluoridating drinking water at household level in Tanzania.
    (University of Dar es Salaam, 2002) Mjengera, Hassani Juma
    Excessive fluoride concentration in drinking water is a major problem in many regions of the world, especially in developing countries, which are facing financial constraints and the technology to treat the water to acceptable fluoride levels. Excessive fluoride in potable water has been found to be the cause of dental, skeletal and crippling fluorosis. With these facts in mind water with excessive fluoride should be treated, although simplicity applicability, acceptability and affordability of these are yet to be verified. This project therefore is aimed at developing an efficient and affordable method of producing drinking water with acceptable fluoride concentrations. The use of bone char media has been considered and tested. In this research charring temperatures, contact time and fluoride binding capacity were investigated. A series of raw cattle bones were charred at different durations for a temperature of 600°C, followed by charring for 20 minutes within temperature range of 300°C to 800°C. All the bone samples prepared were crushed and sieved to different sieve sizes. Natural water with initial fluoride concentration in the range of 3.2 to 22 mg/L was used in the investigations since this is a common range of fluoride concentration in Tanzania. Make up water was prepared using sodium fluoride with concentration levels in the range of 10 to 100 mg/L. Using these waters various relationships were observed and established. This study therefore, reveals that thermally activated bone at temperatures of 400 - 600 °C, produce bones of good quality required for defluoridating water for drinking and cooking. Two systems for defluoridation of water have been developed and set for practical tests in Kitefu and Ngurdoto Villages in Arumeru District Arusha Region in Tanzania. Initial tests have shown that the media produced water of acceptable quality with 0.3-mg/L residue fluorides. The units have operated well for a period of 12 months with residual fluoride contents of 0.3 mg/L from initial fluoride levels in the range of 2.8, 10 and 15.6 mg/L. The beneficiaries have accepted the technology without any difficulty.