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Arsenic (As) is a naturally occurring contaminant found in many ground waters.
Arsenic in water has no color, taste or odor. It must be measured by an arsenic test kit
or lab test.
Public water utilities must have their water tested for arsenic. You can obtain the
results from your water utility contained with in your consumer confidence report. If
you have your own well, you will need to have the water evaluated. The local health
department or the state environmental health agency can provide a list of test kits or
certified labs.
There are two forms of arsenic: pentavalent arsenic (also called As (V), As (+5))
and trivalent arsenic (also called As (III), As (+3)). In well water, arsenic may be
pentavalent, trivalent, or a combination of both. Although both forms of arsenic are
potentially hazardous to your health, trivalent arsenic is considered more harmful than
pentavalent arsenic.
RO systems are very effective at removing pentavalent arsenic. A free chlorine residual
will rapidly convert trivalent arsenic to pentavalent arsenic. Other water treatment
chemicals such as ozone and potassium permanganate will also change trivalent
arsenic to pentavalent arsenic. A combined chlorine residual (also called chloramine)
where it does convert trivalent arsenic to pentavalent arsenic, may not convert all the
trivalent arsenic in to pentavalent arsenic. If you get your water from a public water
utility, contact the utility to find out if free chlorine or combined chlorine is used in
the water system.
This Watts Water Quality reverse osmosis system is designed to remove up to 98% of
pentavalent arsenic. It will not convert trivalent arsenic to pentavalent arsenic. Under
laboratory standard testing conditions, this system reduced 0.30 mg/L (ppm) pentavalent
arsenic to under 0.010 mg/L (ppm) (the USEPA standard for drinking water). Actual
performance of the system may vary depending on specific water quality conditions at
the consumer’s installation. In addition to the independent laboratory standard testing
conditions Watts has conducted additional field testing on our reverse osmosis units
to determine trivalent arsenic reduction capabilities. Based upon Watts field testing, it
has been determined that the RO units are capable of reducing up to 67% of trivalent
arsenic from the drinking water.
ARSENIC FACT SHEET
