Reverse Osmosis
Reverse osmosis pressurizes and
passes impure water through a semi-permeable membrane
and removes many of the impurities (approximately 90 percent
free of mineral and biological contaminants). The quality
of the membrane and the pressure of the water help determine
how effectively the water separates the contaminants.
Reverse osmosis (RO) units remove substantial
amounts of most inorganic chemicals (such as salts, metals and minerals), most
microorganisms and many organic chemicals. They do not effectively remove some
organic compounds such as nitrate; they will reduce levels somewhat.
Mechanical filters and activated
carbon filters are most always used with an RO unit. First, the mechanical
filter removes dirt, sediment and other impurities that clog the reverse osmosis
membrane. The RO unit is installed next. An activated carbon filter then removes
some organic compounds which pass through the RO unit. Nitrates, however, will
pass through carbon filters.
Reverse osmosis units use large amounts of water. Typically,
about 75 percent or more of the water put into RO units is discarded with the
contaminants. These systems may not be appropriate for households with a limited
water supply. These units are expensive to purchase and require regular maintenance.
Usually they are connected to a cooking and drinking line only and installed
under the kitchen sink. Regular testing of the water supply is necessary to
make sure the membrane is intact.
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