Appropriate deflouridation technology for use in flourotic areas in Tanzania

High fluoride in drinking water is a problem found in both ground and surface water in various parts of Tanzania. Several defluoridation methods have been tested and detailed studies have been carried on bone-char method, alum/lime method and the combination of the two methods. In bone char method, the bones are charred in special kilns fuelled by wood charcoal. Different sizes of the kiln have been fabricated and tested. Crushing and sieving devices have been developed. The effectiveness of bone char particles sizes in fluoride removal has been studied and the results favoured small particle sizes. However, experimental conditions discouraged the use of very fine particles sizes of bone char due easy clogging. Household and institutional levels bone char defluoridation systems have been developed and tested. Filter columns packed with heat-activated bones are found to be more effective than fill and draw bucket type defluoridator. The bone char media used has the capability of producing water with a residual fluoride concentration of less than 0.1 mg/l from an initial fluoride of 12.0 mg/l. Use of alum and lime in fluoride removal from waters with excessive fluoride has been experimented upon. A plant with an automatic chemical dosing and mixing system for use at institutional levels has been developed and tested. The method was able to treat water with an initial fluoride concentration of 12 mg/l to a residual fluoride concentration ranging from 2 to 3 mg/l. During the study it was established, that the bone char method is appropriate for use in rural areas of Tanzania due its simplicity, local availability of materials and the possibility of processing the material locally. (C) 2003 Published by Elsevier Ltd.