Activated alumina (AA) is the only filter material specifically designed to remove fluoride and arsenic from water. It is a ceramic compound made of aluminium 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 0.1 ppm, in other words 99% of the normal fluoridated water level.
It occurs naturally in its crystalline as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. (Wikipedia)
Activated Alumina is recommended by the Environmental Protection Agency as not only an effective means of removing fluoride but also to remove other harmful contaminates such as Thallium which can leech into the drinking water from mining sites. Activated Alumina has also been chosen for use in the United States’ largest fluoride removal plant in Andrews, Texas. The SORB 09 technology was chosen based on the performance of an on-site pilot test that demonstrated the system’s robust technology, economics and capabilities over other tested technologies.
The activated alumina cartridge that we use is made by a Company in the USA, it contains a large amount of very high grade activated alumina which will not “powder” like cheaper versions or refillable cartridge versions. The lifespan that this cartridge has been tested to is 1900 litres at a flow rate of 1.9 Litres per minute, the flow rate is extremely important as too little contact time or not enough media in the cartridge can lead to a reduced amount of fluoride being removed. Tested under the above conditions, the cartridge will remove a minimum of 90% fluoride.
For large municipal treatment systems, the use of activated alumina is probably the most commonly used fluoride removal technology. For activated alumina to operate most effectively the pH range should be held to 5.5 to 6.5 (Water quality Organization). This of course does not mean that the media will not work at pH levels that are higher than 6.5.
DOES ACTIVATED ALUMINA ADD ALUMINIUM TO THE WATER THAT IT TREATS?
The one issue that you will read when browsing the internet is that activated alumina will add aluminium to the water that it is treating. The reason that this has become so persistent is largely due to sellers of reverse osmosis systems who have a vested interest of course in selling their particular systems. The European Food Safety Authority carried out a study in 2006 to investigate these rumors
Hers is a summary of the findings:
The Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC) has been asked to evaluate the food safety aspects related to the removal of fluoride from natural mineral waters (NMWs) by filtration through a bed of activated alumina.
NMWs at source may contain levels of fluoride higher than the maximum concentration limits established for the constituents of natural mineral waters by the Commission Directive 2003/40/EEC. Removal of the fluoride is only allowed by an authorized process. Information concerning the source and treatment of activated alumina and the filtration process conditions was provided and showed that critical steps of the proposed process are the following:
Testing of activated alumina filter according to the European standard applicable for leaching tests (EN 12902)  to ensure that no impurities are leached to the water in quantities that result in concentrations exceeding the limits set in Commission Directive 2003/40/EC on the constituents of natural mineral waters, or in the absence of relevant limits in that Directive, the restrictions set in Council Directive 98/83/EC on the quality of water intended for human consumption or in national applicable legislation.
Initialization procedure with alkaline or acidic chemicals to remove any impurities and fine particles before the use of the filter.
Regeneration procedure with appropriate chemicals to renew the capacity of the filter resulting at the same time in the removal of any possibly formed biofilm.
From the information provided it was shown that under optimized process conditions the release of impurities due to the use of the activated alumina, if it occurs at all, is always lower than the relevant limits set in the Directives mentioned above.
Data on the actual content of many anions and cations in various types of NMW (natural mineral waters) were provided. An increase of the concentration after the treatment was found in some cases for aluminium (from 18 up to 86 microg/l), bromide (160 -> 280 microg/l) and boron (66 -> 550 microg/l). However, in most types of water these changes were not observed at all and the observed variations of composition before and after treatment were low.
Leaching of aluminium from the activated alumina depends on the pH of the NMW and the alumina manufacturing process . In some cases levels between 100 and 200 microg/l were reported. However, based on data provided  by optimising the pH conditions and selection of the appropriate medium the aluminium release resulting from the process would normally not exceed 40-60 µg/l. It was demonstrated that the treatment of NWM with activated alumina is suitable for the intended purpose. Under optimized conditions the release of cations or anions from the medium during treatment is negligible and will not pose a risk to human health.
It is important to note that we use a very high grade filter after the activated alumina cartridge which has been tested to remove 99% of any aluminum present in the water.