GERMICIDAL ULTRA VIOLET (UV)
This technology is often confused with Vacuum Ultra Violet
Ozone Generator systems. They are in fact two very different technologies.
Both technologies use lamps that operate in the UV light spectrum.
Germicidal lamps produce output nearer the upper end of the UV-C spectrum at
253.7 nanometers. Ozone generating lamps operate just below the UV-C spectrum at
the 185 nanometer range.
Germicidal UV lamps are used in water treatment and in air
treatment such as HVAC air intake ducts, and in smoke lounges, etc.
For purposes of this discussion, we will discuss water
Germicidal UV is used in many water purification systems
such as ponds, swimming pools, water treatment plants, home drinking water
The application consists of placing a Germicidal UV lamp in
a clear housing. This housing is then directly installed into the water flow
plumbing. Water and many contaminants contained in the water are exposed to the
glow from the lamp. Many manufacturers of this technology state a microorganism
kill rate of 91% with some as high as 99% of the organisms actually exposed to
There are several issues with this technology. One is
initial cost, another is ongoing maintenance and lamp replacement costs, and
another is clarity of water being purified.
Initial product cost and installation cost is greater than
Lamp replacement is another issue. Manufacturers state the
lamp life requires the lamps to be replaced as often as every six months. Some
allow ten to eleven months. While the lamp cost is one concern, the actual
process of replacement cost is another as it is invasive to the plumbing.
Depending upon water clarity, not all contaminants will be
exposed to the actual glow. This is due to light blockage from other
contaminants, so kill rates will be lower. Remember, only contaminants visible
to the lamp glow are affected.
One issue that exists is the accumulation of debris or
chemicals on the surface of the lamp cartridge hindering exposure to the glow.
This requires a periodic cleaning to obtain the full benefit of the system. Some
manufacturers have addressed this by installing an actual wiper that transverses
the light column automatically, which is additional initial and ongoing cost,
and may not totally correct this issue.
Ozone technology for swimming pools has been in regular use
for over 50 years in places like France, Germany and other European nations as
they realize the consequences of chlorine gas.
Ozone has also been in use in Europe since the 1890’s for
drinking water purification. Some large cities in the United States such as Los
Angeles and Milwaukee now boast the best drinking water in America since they
began using Ozone as a purification method. It is difficult to find bottled
water that has does not use Ozone as a purification method.
Ozone, although a disinfectant or sanitizer and oxidizer,
it is normally referred to as the primary oxidizer and alternative sanitizer
when referring to its use in swimming pools in the United States.
Ozone destroys viruses and bacteria such as e-coli and
legionaries, and others.
Ozone is over one thousand times faster acting than
chlorine at oxidizing and destroying bather load in a swimming pool. This
drastically reduces chlorine requirements.
The advantages of using ozone in a swimming are many. To
name a few:
- Decreased chemical usage—significant savings considering the cost of
- Better water clarity
- Reduction or total elimination of chloramines
- Reduction or total elimination of odors-particularly valuable in indoor
- Smoother water feel
- No red itching eyes normally caused by chloramines
- Very effective at destroying viruses and organisms
- pH neutral
Ozone is a gas which consists of three oxygen atoms and is
referred to as O3. Ozone has a very short life cycle and must be produced on
site at the pool location. Ozone is created by a process where O2 Molecules are
divided into two 01 atoms. Oxygen diatom or O1 does not exist alone naturally.
What occurs after the splitting of the O2 molecule is the newly created O1
immediately loosely bond to available O2’s forming O3 molecules.
The loosely bonded O1 departs the O3 and attaches to any
organic which results in oxidation of the organic (basically very rapidly
disrupts the DNA/RNA structures). The O2 is released as O2 and the contaminate
that was oxidized by the O1 is destroyed.
Ozone gas is introduced into water by means of either a
venturi injector creating a vacuum to suck ozone gas into the water or with
direct injection or diffusers by pushing the air into the water with an air
pump. The Ozone gas mixes with the water. The best saturation of Ozone in water
is obtained when many fine bubbles of Ozone is introduced which provide more
total surface area of Ozone contact.
There are basically two ways that Ozone is produced by man
or by nature. One is known as Corona Discharge (CD) and the other is
passing air across special Vacuum Ultra Violet lamps. (VUV) often times
referred to as UV Ozone or Very Ultra Violet Ozone.
Manufacturers of each of these technologies say the other
technology uses more electricity. In reality they are pretty equal. In some
applications VUV lamps use less and others Corona uses less, but in any event,
not by much and not an issue. Neither uses much electricity.
Another statement by manufacturers is ease of maintenance
between the two technologies. This is also subjective and used by who is selling
what. Corona manufacturers require replacing check valves and hoses annually,
and to wear protective gloves when doing so. Corona cell components also need
periodic maintenance. VUV Lamp Ozone manufacturers state their lamps run between
9,000 and 20,000 hours, so they may need replacing depending upon pool
filtration run time every several to seven or so years.
Both Vacuum Ultra Violet lamp Ozone systems and Corona
Discharge systems are available for use in commercial swimming pools ranging to
the millions of gallons.
Extremely large Corona Discharge systems are used for large
metropolitan municipal water treatment systems.
Although this discussion is dealing with swimming pools,
there are many applications for both Ozone technologies such as, but not limited
to, water cooling towers, laundry systems, drinking water, wells and cisterns,
wastewater treatment, aquariums, fruits and vegetables, meats, odors, medical,
ice machines, many more.
The two technologies, CD and VUV, are briefly discussed
Corona Discharge (CD) Ozone Generators
Corona discharge is a high
electrical energy field such as lightning in natural occurrences, and by man
using two highly energized metal or ceramic plates or chambers with a narrow gap
in which air flows through. The arcing of this high electrical energy called the
corona field alters the electron structure of all elements in the air passing
through the chamber.
When man made corona discharge ozone generator systems are
fed pure oxygen input and also very dry air passed through an air drier, they
produce high quantities of Ozone. When manufacturers of Corona Discharge Ozone
systems provide Ozone output production graphs, they sometimes use pure oxygen
and very low humidity or dry air in testing. At a minimum, they often use drier
air than normally found in many areas of the United States.
In reality, Oxygen concentrators and air dryers are price
prohibitive for the backyard pool so ambient air only is passed through the
cell. Pure Oxygen does not exist in ambient air, and in some areas of the
country, humidity is very high. Commercial CD systems that can afford the cost,
and do provide Oxygen concentrators require additional maintenance such as
cleaning concentrator filters, and life cycle issues. They also require Ozone
monitoring safety devices.
(Ambient air: A colorless, odorless, tasteless, gaseous
mixture, mainly nitrogen (approximately 78 percent) and oxygen (approximately 21
percent) with lesser amounts of argon, carbon dioxide, hydrogen, neon, helium,
and other gases.
b. This mixture with varying amounts of moisture and particulate matter,
enveloping the earth; the atmosphere.)
Corona Discharge systems provided with ambient air input to
the chamber such as backyard pools have certain issues that arise. Below are two
One issue is the high Nitrogen content of ambient air. As
mentioned previously, all elements passing through a Corona chamber are altered.
Nitrogen is the primary substance in air, and altering its state creates harmful
byproducts such as nitric acid (nitric acid: A clear, colorless to yellow
liquid that is very corrosive and can dissolve most metals. It is used to make
fertilizers, explosives, dyes, and rocket fuels) and Nitric oxide (nitric
oxide n. A colorless, poisonous gas), along with other Nitrous byproducts.
To top it off, Nitrates. Nitrates are Algae food.
Another issue is Humidity. Ever wonder why it is that when
you reach for something or someone in the winter time where the air is dry and
you are zapped by a bolt of static electricity? Ever wonder why in the summer
time, or when outdoors this does not occur? These answers are simple—Ambient Air
Humidity. If humidity affects electrical conductivity in ambient air, could it
not directly relate to the electrical field in a Corona Discharge cell hindering
In review: Corona Discharge systems that are supplied pure
Oxygen and dry air produce high levels of pure Ozone. Corona Discharge units
that are provided only ambient air, such as backyard pool applications, create
Nitrogen byproducts and may experience diminished outputs with increased