Ozone for Water Treatment
Ozone units are usually installed as point-of-use (POU) at the kitchen faucet and used to
process water intended for
drinking and cooking purposes only. Larger whole-house-units (WHU) are
available and are placed at the incoming water supply to process all incoming water.
Ozone
is the second most powerful oxidizer, falling only behind Fluorine and is an
extremely reactive chemical form of pure oxygen. Like
chlorine, ozone is a strong oxidizing agent and is used in much the same manner.
Ozone can be recognized as the product smelled near an electric spark or
lightning strike. Ozone has been used by municipal systems in
Europe to disinfect water for years.
Ozone is effective for:
- most amoebic cysts
- viruses and
bacteria
-
phenols
- removal through precipitation
of iron and manganese which can then be removed through filtration
- aid in turbidity removal
- eliminating or controlling
many
color, taste, and odor problems
Most
home ozone generated is through corona discharge or from a lamp which creates
light at a slightly shorter wavelength than ultraviolet. ( 185 nM) The ozone is injected into the raw water whenever the there is a
demand on the water supply.
Considerations:
Ozone may not kill large cysts and some other
large organisms, so these should be eliminated by filtration or other procedures
prior to treatment.
ozone is
extremely active as a disinfectant
over a wide pH and temperature range vs chlorine
contact time is so short that
it is not a consideration in the system design.
benefit of ozone
treatment is the lack of potentially harmful by-products like trihalomethanes (THMs),
which chlorination can produce when it oxidizes organic matter.
Most home systems use dry air to
produce the ozone therefore the ozone is injected into the water through a pump
and also includes a mechanism to clean and remove the humidity from the air must be
included, and such a system requires routine maintenance.
Residual amounts of ozone can
be removed from the water prior to consumption by passing the water through a UV
chamber, and/or an activated charcoal filter.
The
rate that Coliform bacteria is killed when exposed to ozone has been published
to be 3125 times faster than by chlorine. Therefore, contact time between water
and ozone is reduced to the time necessary to achieve a concentration of 2 to 3
PPM (Parts Per million) in the treated water. Ozone is a recognized weapon
against Cryptosporidium.
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