"Osmosis" is
a term you may remember from biology referring to the passage of a substance
through a membrane from a solution of greater concentration to one of lesser
concentration.
Reverse osmosis is forcing water under pressure through a
membrane, which excludes substances with a molecular structure larger than the
pores of the membrane. A home reverse osmosis unit operates from the
source water pressure.
Reverse osmosis removes up to
99.9% of undesirable contaminants and filters particles as small
as 1/1000 of a micron by forcing untreated water through a
semi-permeable membrane. Pressure forces the water to flow in
the reverse direction to the direction of flow in natural
osmosis.
A unique feature of reverse osmosis, compared to standard water filter methods, is
that RO screens out the contaminants to be flushed away, rather then
attracting and holding them as filters do. The molecules of water actually pass through
the membrane leaving the contaminants behind.
The membrane also allows oxygen through, as well as
some other elements with a very small molecular size, including some tiny
molecules of colloidal
and subcolloidal minerals.
The pores are small
enough to screen out radioactive minerals and fluoride (which have large
molecules), as well as bacteria and even some viruses. Still, a reverse osmosis unit should
always include other types of media such as a sediment filter, redox media to eliminate chlorine,
biologicals and metals, and carbon to catch any organic
chemicals. Eliminating these contaminants first will prolong the life of the
RO membrane.
Since
sediment can clog a membrane, a sediment pre-filter is often included.
Chlorine
can also harm membranes. With chlorinated water, reverse osmosis requires a carbon
or redox pre-filter to protect the membrane's longevity.
Reverse osmosis units are
susceptible to the growth of bacteria and mold within them when
not in regular use. These agents can attack and ruin a membrane,
resulting in contaminated water coming through.
Redox media preceding the
membrane will help prevent these microbes from getting to it.
Frequent use of the unit will reduce the potential for bacteria
or mold to get a colony started. A low bacterial count
in the source water is also important.
Most reverse osmosis membranes
are of the Thin Film Composite (TFC) type. A Cellulose Acetate
(CA) membrane may be used in special situations.
Prices on quality RO
units run from $170 to $800, depending on style and features.
Reverse
osmosis water actually has an increased oxygen concentration, as O2
has a small enough molecule to cross the membrane. RO water also contains
small quantities of colloidal and subcolloidal minerals.
However, the reverse osmosis process
removes most of the minerals from the water.
Mineral devalued water if too
acidic will draw
minerals from the body when consumed regularly. The pH of
RO water is often too acid for the human body. If this is the case, it is
recommended that a
remineralizing alkalizer unit
be added to correct these problems.
We believe that reverse osmosis is
the best choice in home water purification. When the source
water has a pH of 7 or less, "Corrected Reverse Osmosis" is the
way to go. It is recommended that you test your water with pH
tape or strips (litmus paper) or another method to determine
if the remineralizing alkalizer is needed to correct the water.
