Many water treatment dealers make false claims about removing fluoride from drinking water. It’s possible that these dealers are unaware of the complexity of issues involved in fluoride removal. Either that or they’re misleading you.
Fluoride is most often removed (in kitchen filters or whole house applications) using activated alumina (aka alumina oxide or Al203). The fluoride ion attaches to the surface of the alumina and is thereby removed from the drinking water. The other media that is sometimes used is bone char.
The issues that affect removal include the flow rate of the water, pH, and the presence of competing ions. In other words the faster the water flows through the filter the less fluoride will be removed. And the more ions present in the water that also have an affinity for the media you are using the less fluoride will be removed.
Removal of fluoride is also affected by the pH of the water. Activated Alumina is more effective at a low pH and testing has suggested that the use of AA may lower the pH of your water.
The optimum flow rate for removal of fluoride is about .75 gallons per minute for every 1 cubic foot of activated alumina media. Therefore if you wanted to shower in water that was fluoride free and your shower flows at 4 gpm then you would need a whole house fluoride system that consists of 5.3 cubic feet of activated alumina. Perhaps you’ll begin to see my point. Most water treatment dealers provide whole house water purification systems that are substantially smaller than this and yet claim to be removing fluoride. Contact time is also important with the ideal being twenty minutes, meaning that the water and the media spend twenty minutes together. The only time this happens is in between uses in the house.
The flow rate scenario assumes optimum water chemistry for fluoride removal. The presence of naturally occurring bicarbonate in water will interfere with fluoride removal, reducing the capacity of the AA by up to 80 per cent. Other ions either compete with fluoride or are also removed by activated alumina, thus reducing overall capacity. To accurately determine the capacity of the filter you are using you would have to add all of these together and divide into the rated capacity of the filter you are using. That would provide you with the number of gallons you can treat before you need a new filter.
If you want to be certain of removing fluoride from you water you should use a reverse osmosis system at the kitchen sink. If you wish to retain the natural minerals in water then a reduction of fluoride may be achieved using an activated alumina filter in a system such as my Kitchen Defender but results will vary substantially from place to place, depending on local water chemistry.
I have begun to experiment with the use of bone char to remove fluoride and competing ions. At this point there’s not much data on its effectiveness. Bone char is known to remove fluoride but the type of research on flow rates, pH, and competing ions has not been performed to date. My suspicion is that bone char removal rates for fluoride are similar to that of AA but that it functions at a higher pH. I’ll write more as I learn more.