July 1, 2008

Reverse Osmosis Water Filter Systems

Sean Massey of Aqua Systems offered a presentation to the club assembly on Reverse Osmosis or RO water filtering systems.  He has 23 years of experience in the water treatment industry.

RO technology was developed in the 1940's by the US government and is a process where water migrates across a semi-permeable membrane.  The membrane is capable of removing particulate and pollutants that are as small as 0.0005 microns but the water molecules are able to pass.  Particulates are flushed from the membrane so that it does not clog over time.  For size comparison, a human hair is about 75 microns thick and the human eye can see down to 40 microns.

A complete system would include prefiltering through a 5 micron sediment filter and then the water is passed through the RO membrane.  A final stage is carbon filtration to remove odor and undesired tastes and the water is held in a storage tank.  This is needed since the processing time is slow and sufficient flow cannot be provided to support on demand filtering.

The RO pre and post stage filters typically require replacement in 6 to 12 months.  The RO membrane lasts between 3-5 years before replacement is needed.

The effectiveness of the filtration was demonstrated using a TDS or Total Dissolved Solvents meter to compare RO filtered water (<100 TDS)  in comparison to town drinking water (~800 TDS).  Also, Sean demonstrated that water is not a conductor of electricity but it is the impurities that does so and RO filtered water does not conduct electricity.

RO does have some disadvantages in that it removes fluoride which is needed for healthy teeth.  Also, if a whole house system is used, the purified water can attack copper piping as pure water is a perfect solvent and will cause pinhole leaks in copper pipes.  PVC piping can be used to deal with this problem.

Hosting Rotarian: Dave Bertlesen