Using Reverse Osmosis for Removing Fluoride from Water
With concerns over fluoride exposure, more people are turning to reverse osmosis (RO) as a way to remove fluoride from drinking water. But just how effective is reverse osmosis at eliminating fluoride? And what should you know if you are considering a reverse osmosis system for fluoride removal in your home?
How Reverse Osmosis Works
Reverse osmosis uses water pressure to push water through a semi-permeable membrane with microscopic pores that block dissolved particles based on size. Water molecules pass through, while larger contaminants, including fluoride ions, are rejected and flushed away. This leaves purified water on the other side.
Effectiveness of RO for Fluoride Removal
Standard reverse osmosis offers moderate fluoride reduction, often 50–90% depending on factors like:
- Membrane quality: higher-rejection TFC membranes remove more fluoride than older CTA membranes.
- Water chemistry: Other minerals that bind with fluoride can impact removal levels.
- System age: new RO membranes remove more fluoride than older, worn ones.
While helpful for lowering fluoride, standard RO still leaves detectable amounts. For maximum removal, look for systems with added fluoride-specific media.
Optimising Reverse Osmosis for Fluoride
To enhance fluoride removal, some tips include:
- Choose high-rejection TFC membranes, not older CTA types. This improves rejection of fluoride ions.
- Add activated alumina after RO to adsorb residual fluoride. Alumina acts as a fluoride “polisher”.
- Use an in-line fluoride water filtration cartridge as a final stage on the RO water outlet.
- Replace pre-filters and membranes per the manufacturer’s schedule to maintain performance.
While requiring some modifications, reverse osmosis under sink and benchtop systems can be optimized to remove up to 90-95% of fluoride. Alternative options for fluoride filtration are under sink water purification systems with built-in fluoride removal stages, or gravity water filters designed to remove fluoride..