23 Water Purification: Treatments requiring electricity: Ozone:
Description
This article is from the Water Treatment FAQ, by Patton Turner with numerous contributions by others.
23 Water Purification: Treatments requiring electricity: Ozone:
Ozone is used extensively in Europe to purify water. Ozone, a
molecule composed of 3 atoms of oxygen rather than the two, is formed
by exposing air or oxygen to a high voltage electric arc. Ozone is
much more effective as a disinfectant than
chlorine, but no residual levels of disinfectant exist after ozone
turns back into O2. (one source quotes a half life of only 120 minutes
in distilled water at 20 deg C). Ozone is expected to see increased
use in the US as a way to avoid the production of
Trihallomethanes. While ozone does break down organic molecules,
sometimes this can be a disadvantage as ozone treatment can produce
higher levels of smaller molecules that provide and energy source for
microorganisms. If no residual disinfectant is present (as would
happen if ozone were used as the only treatment method), these
microorganisms will cause the water quality to deteriorate in storage.
Ozone also changes the surface charges of dissolved organics and
colloidally suspended particles. This causes microflocculation of the
dissolved organics and coagulation of the colloidal particles
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