Activated alumina (AA) is the only filter material specifically designed to remove fluoride and arsenic from water. A ceramic compound made of aluminum oxide with a very high surface-area-to-weight ratio, AA has a very high capacity for fluoride adsorption. Most municipal water supplies add 2 ppm (parts per million) of fluoride. AA filters can reduce fluoride concentrations to below .1 ppm, or down to 99% of the normal fluoridated water level.
Quality water filters, especially after proper flushing, are designed to prevent filter media from escaping the filter housing. As KDF media is designed to remove aluminum and other metals from water, placing the KDF/Carbon filter after the activated alumina provides extra insurance, preventing any activated alumina particles from reaching your glass of water. This has been confirmed by the president of KDF Fluid Treatment.