Domestic Defluoridation of Water Using Locally Produced Activated Alumina by N V Dzung , H H Phong, N N Long, N T Quang and P Waldemar

A low-cost defluoridator for domestic use is developed, based onactivated alumina as a sorption medium. The filter column is 11.4 cm in diameter and 1 m in height. It is designed to contain about 8 L or about 3 kg of alumina. The alumina is prepared by using aluminium sulphate and sodium hydroxide to precipitate aluminium hydroxide at 60-70 oC. The precipitate is settled, washed,granulated and calcined at 550 - 600 oC for 4 hours. A column test in the laboratory revealed that the fresh alumina could remove fluoride from 5 mg/L to < 0.7 mg/L at a capacity of 1.2 g/kg. The developed filter allows for monthly regeneration of the medium by the users themselves. A quantity of 0.4 kg of aluminium sulphate is used in the regeneration. The filter operates upwards, while the regeneration operates downwards in the filter column. Field-testing data show that the filters could treat water containing about 2 mgF/L down to 0.15 - 0.46 mg/L, thus an average removal efficiency of 85 %. Monitoring of a filter through 5 operation periods shows that the regenerated alumina loaded with water containing 2.6 mgF/L could treat the water at an efficiency of 89 %. Themedium capacity is estimated to be 0.7 gF/kg regenerated alumina. Field experiences show that the villagers very well accept the filter; it is easy to operate and to maintain and the filter costs are affordable to the families, about 45 USD for purchase and 20 US Cents for the monthly regeneration.