The U.S. Environmental Protection Agency’s (EPA) Water Infrastructure Resiliency and Finance Center, in collaboration with the...
The following is the first of 11 articles addressing ozone's
applications, installation, sales, service, basics and more. The 12th and final
installment will be a quiz to test your ozone knowledge—so make sure you
come back each month to brush up. Details and instructions will be given in the
What oxidizer can kill bacteria, impart no adverse taste or
odor, be tested and verified that it is present and have no residual when
consumed? Chlorine and hydrogen peroxide cannot work without
filtration/destruction. Ultraviolet cannot. Ozone is the only choice left.
The main objective when using ozone for bottled water is to
maintain ozone residual in the water as it is bottled. Ozone is required by
public health agencies in many locations around the world.
The main purpose of ozonating bottled water is to improve
the taste, increase shelf life, maintain a bacteria-free environment and comply
with federal and local health regulations.
Sizing the ozone equipment is based on several parameters.
gpm of the water being bottled.
water usage hours per day.
quality to be ozonated.
users (bottler) objective for using ozone.
There are two ranges that are to be achieved. We call these
ozone residual ranges. The ozone production from the ozonator is represented in
grams per hour (gr/hr). The ozone residual in the water is measured as ppm-O3.
(See "Ozone Residuals.")
Mid-Range is the most common. It will maintain ozone
residual, a bacteria-free environment and will pass inspection. The high-range
will kill bacteria that is present. Care must be taken with the high range
because if misapplied, too much ozone could impart a burnt plastic taste and
odor to the water.
Along with dosage comes contact time. There are no
regulations as to the time required, but generally the mid-range does not
necessarily need contact time. The high range will require additional contact
time. This is accomplished with the use of a contact/off gas tank.
The bottling ozone installation consists of an ozonator,
ozone injector, air dryer, contact tank (optional) and an automatic actuation
Ozone typically is installed at the end of the line
immediately before bottling or prior to the pressure tank after
repressurization. Ozone saturation and mixing is immediate due to "Henry's
Law" of physics. This method is far more efficient than injecting ozone
into an atmospheric storage tank. Ozone will not escape or be wasted as with
The ozonator is electrically connected to a control circuit
that activates when bottling occurs or when an existing pressure switch is
The ozone injects, mixes and treats the water immediately
when the circuit activates.
Once you know the gpm and the water quality you can select the
(See "Ozonator Sizing Example.")
The ozone injector is the device used to get the ozone into
the water. There are two methods-venturi and ozone pump.
Venturis are low-cost items, have no moving parts and
require little or no maintenance. It is critical to size the venturi correctly
according to the gpm and psi. Incorrect sizing will result in insufficient
ozone injection. The venturi must be installed in specific locations or it will
not create the proper suction. Pressure and water volume loss is typical.
Ozone pumps can accomplish injection in any location. They
inject high concentrations of micro-bubbles (Henry's Law). They have moving
parts and require periodic service.
The benefit is the ease of installation, sizing, higher
volume of gas injected and no restriction of flow or pressure.
Air dryers remove all of the humidity and moisture from the
air prior to the ozonator. The air is dried to a minimum of -40° F dew
point. Dry air greatly increases ozone production (two to three times) compared
to atmospheric conditions.
Extending contact time (CT) is accomplished by pressurized
storage. CT is only important when bacteria are present. Once bottled, the
ozone quickly dissipates due to the lack of pressure. The purpose of the
contact tank is to maintain the ozone in contact with the water for a
set/extended time prior to bottling. The tank design is basic with no moving
parts or media. (Three to five minute CT is sufficient for bacteria elimination.)
Ozone residual must be verified in the bottles. Assuming you
have adequate ozone going into the bottles can give you a false sense of
security. Dissolved ozone gas is difficult to measure.
It requires sophisticated equipment, and a simple color
comparator test kit is inadequate. The best test kit for this purpose is a
hand-held electro-photometer. Testing will not become a standard practice until
it becomes mandatory by the local health departments.
Ozone systems can be used as the pretreatment to remove
iron, sulfur, manganese, color, bacteria, taste and odor. This will keep
polishing systems such as RO, softeners and carbon filters from fouling. Look
for more information in future articles.