Cooling Towers

Ozone has Major Advantages

Cooling Tower Water Treatment

We also focus on cooling tower water treatment, because - amongst other bacteria - Legionella (the cause of Legionnaires Disease) is still a problem in cooling towers (see below).

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.

Ozone advantages for Cooling Tower water treatment include:

  • Eliminates the use of chemicals except for pH balancing
  • Ozone is produced on-site and requires no storage of dangerous chemicals; Ends discharge liabilities and chemical storage record keeping
  • Destroys all types of microorganisms instantly; decomposes organic waste by oxidation
  • Micro-organisms cannot get resistant to ozone after prolonged use of ozone
  • Removes existing calcium carbonate scale by destroying the biomass glue bonding agent
  • 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
  • Due to good bio-film removal capacities very effective against Legionella
  • No chlorinated compounds. Very low corrosion rates in the system
  • Environmentally friendly

Plus, Ozone reduces energy costs by:

  • Increasing the heat transfer efficiency of the chiller
  • Reducing makeup water to the cooling tower by permitting more cycles between blow-downs
  • Eliminating the cost and problems in ordering, shipping, handling, storage, and disposal of regular chemicals
  • Reducing power consumption by keeping the chiller heat transfer efficiency high through cleaner condenser tubes

NOTE: 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-life of ozone is normally less than 15 minutes in cooling systems. To assure 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 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 too much 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.

Legionella Microbes and Bio-Film in Cooling Towers:

In the prevention and control of Legionella causing microbes, ozone has taken an eminent roll. The specific characteristics of the Ozone disinfectant make sure it gets the job done where others fail. Bio-film in the piping can protect legionella from most of the disinfectants. An environmentally friendly solution for this problem is the use of ozone disinfection for new and existing cooling towers.

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

Bio-films 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.

Case Studies:

Ozone use at the Kennedy Space Center Cooling Tower  [PDF - 115 KB]
Application of Ozone in Cooling Water Systems  [PDF - 197 KB]