LEGIONELLA

In the prevention and control of legionnaires disease (legionella) causing microbes, ozone has taken an eminent roll. The specific characteristics of the disinfectant make sure ozone gets the job done where others fail.

Biofilm in the piping can protect legionella from most of the disinfectants.

Environmentally friendly solution for this problem is the use of ozone disinfection for new and existing cooling towers.

BIOFILM

A biofilm is a layer of microorganisms contained in a matrix (slime layer), which forms on surfaces in contact with water. Incorporation of pathogens in biofilms can protect the pathogens from concentrations of biocides that would otherwise kill or inhibit those organisms freely suspended in water.

Biofilms provide a safe haven for organisms like listeria, E. coli and legionella where they can reproduce to levels where contamination of products passing through that water becomes inevitable.

OXYGEN

Gaseous chemical element, symbol: O, atomic number: 8 and atomic weight 15,9994. It’s of great interest because it’s the essential element in the respiratory processes of most of the living cells and in combustion processes. It’s the most abundant element in The Earth’s crust. Nearly one fifth (in volume) of the air is oxygen. Non-combined gaseous oxygen normally exists in form of diatomic molecules, O2, but it also exists in triatomic form, O3, named ozone.
Oxygen can be separated from air by fractionated liquefaction and distillation. The main applications of oxygen in order of importance are: 1) melting, refining and manufacture of steel and other metals; 2) manufacture of chemicals by controlled oxidation; 3) rocket propulsion; 4) medical and biological life support; 5) mining, production and manufacture of stone and glass products.

In normal conditions oxygen is a colorless, odorless and insipid gas; it condensates in a light blue liquid. Oxygen is part of a small group of gasses literally paramagnetic, and it’s the most paramagnetic of all. Liquid oxygen is also slightly paramagnetic.
Nearly every chemical, apart from the inert gasses, bind with oxygen to form compounds. Water, H2O, and silica, SiO2, main component of the sand, are among the more abundant binary oxygen compounds. Among the compounds which contain more than two elements, the most abundant are the silicates, that form most of the rocks and soils. Other compounds which are abundant in nature are calcium carbonate (limestone and marble), calcium sulphate (gypsum, aluminium oxide (bauxite) and various iron oxides, that are used as source of the metal.
 

COOLING TOWERS

Evaporative water cooling towers for power generation, industrial, refrigeration and HVAC markets throughout the world.

We also focus on cooling tower water treatment, because - amongst other bacteria - Legionella is still a problem in cooling towers.

Ozone in cooling towers

Ozone is a strong disinfectant and an interesting alternative for the chemical biocides in cooling tower water treatment. The use of ozone in cooling towers has some great advantages. Ozone also has its limitations, which when kept in mind during the design phase, should not cause problems.

The advantages of ozone are:

• Safe and easy in use

•  Low maintenance costs

•  Ozone is produced on-site and requires no storage of dangerous chemicals

• Ozone requires no additional disinfectants

• No cocktail of disinfectants necessary. Micro-organism can not get resistant to ozone after prolonged use of ozone

• High efficiency as disinfectant. A residual ozone concentration of 0.1 to 0.2 ppm is in most cases very effective in keeping the cooling tower and the cooling circuit clean.

• Very effective in removing biofilms

• Higher efficiency of heat exchangers due to reduced biofilm formation

• Due to good biofilm removal capacities very effective against Legionella

• No chlorinated compounds. Very low corrosion rates in the system.

• No persistent chemicals or disinfectants in bleed. Ozone breaks down to oxygen.

• In some cases ozone can replace disinfectants and also dispergents and inhibitors

• In many cases a higher concentration factor is possible

• Lower operational costs and in many cases a lower overall costs

• Ozone is effective in a wide pH range

• Also effective for mussel growth

In the design of a proper ozone disinfected cooling tower, one needs to take care of the following points

• Suppletion water with high hardness and / or high COD levels is less suitable for ozone based cooling towers

• Retention time in the system. The half time of ozone is normally less than 10 minutes in cooling systems. Toassure an adequate residual ozone concentration it is necessary to start with an adequate begin concentration.

• Dead spots. Because ozone depletes to oxygen, spots with little circulation have to be prevented.

• Temperature. The solubility of ozone and the half life time of ozone decreases at higher temperatures. This limits the temperature of the cooling water in which ozone can be used. This limit is in most cases around the 45°C.

• Material. The materials used in the cooling tower need to be ozone resistant.

HEALTH EFFECTS OF OXYGEN

Every human being needs oxygen to breathe, but as in so many cases too much is not good. If one is exposed to large amounts of oxygen for a long time, lung damage can occur. Breathing 50-100% oxygen at normal pressure over a prolonged period causes lung damage. Those people who work with frequent or potentially high exposures to pure oxygen, should take lung function tests before beginning employment and after that. Oxygen is usually stored under very low temperatures and therefore one should wear special clothes to prevent the freezing of body tissues.

ENVIRONMENTAL EFFECTS OF OXYGEN

No negative environmental effects have been reported.

For specific information on your application and the use of Ozone Generators contact  Absolute Ozone®