How Reverse Osmosis Filters Remove Fluoride

How Reverse Osmosis Works:

The process of how reverse osmosis works is a fairly straight forward procedure which basically involves different stages of filtration gradually leading to the reverse osmosis membrane. The main component of a reverse osmosis filter system is the membrane. Reverse osmosis (RO) membranes have the smallest pores of all filters. Using pressure to drive the process, this pressure reverses the natural osmotic pressure and drives water through the membrane and away from dissolved molecules of contaminants. Our RO membranes can remove compounds to 0.0001 micron, which is thousands of times smaller than a human hair.

The effectiveness of reverse osmosis to filter toxic fluoride from water depends on its ability at preventing fluoride molecules from passing through its microscopic pores. RO filters are manufactured to precision tolerances, but the size of the pores in the filter are what ultimately determine what can physically pass through it. The size of the fluoride molecules are generally too large to pass through the even smaller pores of the RO filter.

How Reverse Osmosis Works With Ionic Diffusion:

Although it plays a much less of a role, another factor in a contaminants ability to penetrate the RO filter is ionic diffusion. That is, to diffuse through an RO membrane, the negatively-charged fluoride ion must become associated with, or dissolved into, at least one component of that membrane.

The advanced materials used in our RO membranes do not allow fluoride compounds to bond with the atoms and molecules that make up the membrane, preventing them from passing through it in this manner. 

Reverse Osmosis Filtration Process:

The filter system uses an extensive and detailed process to effectively remove over 2000+ contaminants from the water it is filtering. The filtration process is the gradual sequence of larger to smaller micron filtration, this can be broken up into 3 steps.

1. Pre-Filtration

Before the water can go through the reverse osmosis process, it must be pre-filtered. Pre-filtration is used to remove some of the larger water contaminants and sediment so the thin reverse osmosis membrane does not get damaged. It removes larger sediments, dissolved solids, and reduces chlorine. The pre-filtration step will usually have a sediment filter and a form of carbon filtration such as a carbon block or granular activated carbon filter.

2. Reverse Osmosis Membrane

Once the water has passed through the pre-filtration stage it will reach the reverse osmosis membrane. This is when the reverse osmosis process occurs, the water is forced through a semi-permeable membrane with pressure greater than 40psi. This membrane will let water molecules pass through, but will catch almost everything else in the water to 0.0001 micron. 

3. Post-Filtration 

Finally, the water must go through a remineralization process to add the magnesium and calcium found naturally in water. This is achieved with a post-filter that contains some form of calcium or magnesium. The most common substances used are Calcite (calcium carbonate) and Corosex (a magnesium compound). Some filters use a combination of both. The reverse osmosis treated water is passed through one of these filters where it dissolves some of the filtration media immediately before being dispensed. Calcite remineralizers will bring the pH to neutral (about 7.0) while Corosex will bring the pH above 7.

Reverse Osmosis Filtering Diagram