Tuesday, 1 January 2008

Investigation of Defluoridation Options for Rural and Remote Communities by Amy Dysart

Fluoride primarily produces effects on skeletal tissues (bones and teeth) and has a narrow range between intakes that cause beneficial and detrimental health effects. Elevated levels of fluoride (>1.5 mg/L) in thedrinking water occur in a number of parts of the world and often have significant adverse impacts on public health. In the Northern Territory elevated levels occur in a limited number of groundwater supplies, resulting in an increase in the prevalence of dental fluorosis in the affected population. The investigation focused on the identification of a cost effective, robust and low maintenance defluoridation system that may be implemented in these rural and remote communities. Batch adsorption experiments utilising activated alumina, bauxite and hydrotalcite were carried out, resulting in the successful removal of fluoride from natural water samples. Activated alumina displayed the highest removal rate, greatest capacity for fluoride and the smallest impact on the other water quality characteristics, of the three media and was utilised for further equilibrium isotherms and column studies. Activated alumina equilibrium isotherms were correlated to the Langmuir and Freundlich equations indicating appropriate levels of fluoride adsorption from natural waters could be achieved. Water from two communities in the Northern Territory, Tennant Creek and Ali Curung, was successfully treated through column studies, achieving adsorption capacities for fluoride of 875 mg/kg and 1268 mg/kg respectively. The regeneration (and reactivation) of the column was carried out using 0.1 M NaOH and 0.1 M HCl, which resulted in a decrease in adsorption capacity of the activated alumina with each regeneration.

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