Reverse Osmosis Filters in the Home Waste our Precious Water Resources

When reverse osmosis water filters were first developed in the late fifties, it made some sense to apply that technology in individual homes.  Now, however, we need to do everything we can to conserve water. And reverse osmosis filters waste most of the water put through the system.  Even the very best systems flush four gallons of water for every one gallon of drinking water produced.  Why would anyone pay to flush water down the drain?

In 1959 researchers at UCLA were the first to show that the process of reverse osmosis  could be used  for the removal of salt to obtain pure water. There was a big push for this technology during the Kennedy years.  The slogan was “to to the moon and make the desert bloom".  With the support of government, the breakthrough came with the production of reverse osmosis water filters with a membrane made from cellulose acetate polymer.

The next step was to put these new reverse osmosis water filters into practice.  The town of Coalinga in California was chosen for the first commercial plant, where the improvements to the process continued.  The plant began operations in 1965, producing 6,000 gallons per day from the local brackish groundwater.  This was a great improvement for the residents, as the drinking water had to be trucked in before the plant was built.  Ocean water is about ten times saltier than brackish groundwater.  A plant was next built in La Jolla to work out the problems of converting sea water into fresh water.

The discovery of reverse osmosis filters has impacted the entire world.  In the Middle East and North Africa desalination plants produce trillions of gallons of purified water each day.  The process has also been applied to in home demineralization.

There are two types of membranes for household reverse osmosis water filters.  They are the Cellulose Triacetate(CTA) membrane and the Thin Film Composite (TFC) membrane.  When deciding which to use, you must consider the filtration ability and the tolerance to chlorine.  The CTA membrane tolerates chlorine better, but only rejects 93% of contaminants. The TFC/TFM membranes reject 98% of the contaminants, but it can only be used with chlorine free water.  Most public water supplies are chlorinated.  The membrane for the reverse osmosis filters can be made in a number of different geometric configurations.  Water pressure forces the water molecules through the membrane leaving the contaminants behind.  These, now more concentrated, contaminants are flushed down the drain.

The average reverse osmosis system is a unit consisting of a pre-filter to remove chlorine and sediment, the reverse osmosis membrane, a storage tank, and an activated-carbon post filter.

Better membranes continue to be researched for desalination, as well as membranes for water reclamation and hazardous waste remediation systems.  There is definitely a need for this technology.

But for individual home systems a better choice would be system that does not waste any water at all.  Advances in water filtration technology have made the use of reverse osmosis water filters obsolete.  Do your research, there are much more economical and earth friendly choices.