Cooling Tower Water Treatment


For almost 30 years, ozone has been used to remove and prevent the growth of these organisms while reducing contaminant levels (e.g. AOX and COD) through direct oxidation. Contrary to conventional halogen-based biocides, ozone does not produce unwanted by-products such as halocarbons (AOX).

Cooling Tower Ozone

Cooling systems operations entails extensive treatment as it provides an idyllic growth environment for bacteria, Legionella, algae, fungi and molluscs which can adhere to the pipeline, heat exchanger and cooling tower surfaces. Three main areas of concern are identified:

  1. Scaling in heat exchanger units and pipes
  2. Corrosion of pipes and heat exchanger units
  3. Bacterial and Microbial growth

Malpractices in these areas can lead to reduced heat efficiency and potential overall system failure. Important to note that these facets must be addressed together as fixing one aspect might lead to augmented failure in the other one, an example of higher corrosion level of metals by lowering water Ph levels to inhibit scaling.

Ozone acts as one solution to all these aspects without the need to keep experimenting with different chemicals.

Why using ozone in cooling towers?

Ozone is produced on-site from oxygen gas and is introduced directly into the cooling water via sidestream injection. Ozone may also be injected directly into the cooling tower reservoir. Once it is dissolved in water, ozone proceeds to oxidise organic contaminants and microorganisms. The ozone dosing is regulated automatically by the control system of the ozone generator and varies with the water demand. Ozone, combined with suitable corrosion and scale inhibitors, provides the optimum treatment solution for cooling water.

Some of the advantages with ozone:

  • The most powerful disinfectant
  • Very effective control of Legionella
  • Blowdown water complies with the strictest standards for AOX and COD
  • Microorganism growth is prevented
  • Cleaning downtime reduced
  • No harmful by-product formation
  • No storage/handling of hazardous chemicals or biocides
  • Easy integration in existing plants

Ozone Benefits for Cooling Towers

  • Safe and easy to use
  • Effective for mussel growth
  • Very effective in removing biofilms
  • Ozone is effective in a wide pH range
  • Destroys all types of micro-organisms instantly
  • Ozone decomposes organic waste through oxidation
  • Ozone is 3,125 times more germicidal than chlorine
  • Reduced permit costs for discharge of treated water to the environment
  • Environmentally friendly treatment, facilitating regulatory compliance
  • Very effective against Legionella, due to good biofilm removal capacities
  • Ozone requires no additional disinfectants, micro-organisms cannot get resistant to ozone after prolonged use of ozone
  • Low corrosion rates in the system. Reduces the corrosion rate of metals, including copper heat exchangers, because there are no chlorinated compounds
  • Disinfectant with a high-efficiency level (a residual ozone concentration of 0.1 to 0.2t ppm is, in most cases, very effective to keep the cooling tower and the cooling circuit clean)
  • The insignificant buildup of disinfectant or disinfectant byproducts. Ozone does not leave any chemical residues or disinfectants, at the end of its cycle, ozone decomposes again into oxygen
Industrial Ozone Generators UK

Operational Savings

The use of an ozone system in free cooling towers entails in addition to the benefits comprising, represent significant savings to the levels of:

  • Reduction of water consumption

  • Reduction of consumables

  • Reduction of anti-scaling and anti-corrosion agents

  • Reduced maintenance costs

  • Remove the costs of chemical biocides storage and transport

  • Reduction of energy consumption due to the increased efficiency of the cooling operation

Related Case Studies

Why Ozcon ozone?

Robust and reliable ozone technology

The key reason why Ozcon ozone solution is exceptional for cooling water towers is its robustness and reliability.  It should not be acceptable any longer for operators and users to have stops in operations because the cooling system is unsafe (Legionella) or inefficient (biofouling formation). 

  • Compliance with Strict safety regulations of the cooling tower environments

Cooling towers environment is famous to have strict safety rules and regulations, so leakage of flammable gas into power plant environments should be avoided at all cost, here is where Primozone’s patented way of distributing the gas into the enclosure, through the gas-tight anodized aluminium framework, is a guarantee against leakages in the ozone generator.

  • Reduced maintenance costs

Cooling towers are usually installed in remote locations, unless there is full-time personnel on-site dedicated to the water treatment system (which is an extra expense), sending someone to the site for maintenance, repair and regulation is not optimal as it takes time and involves additional costs. The Primozone system has no preventive maintenance need, and it is fully automated, hence remote monitoring and regulation is possible.

  • Full automation

Full automation makes things easier in environments where not all the personnel is experienced in the operation of water treatment equipment. Plus, the Primozone Human-Machine Interface is so user-friendly that operation and diagnostics are straightforward, even if done manually.

  • Smallest footprint

In the cooling towers case, the ozone system is usually to be installed in its building, so the compact footprint of Primozone technology comes in very handy. The system is so small that it might be containerised.

  • Long-distance ozone distribution

This building/container often has to be placed quite far from the injection point. In these conditions, the naturally high outlet pressure of the Primozone ozone gas is fundamental to be able to distribute the ozone on a long distance.

High pressure is useful also because recirculating water in cooling towers is pressurised. Unless you choose Primozone, it’s most likely not possible injecting the ozone directly into the water – you must use a Venturi injector. If the water pressure is above 3 bar(g) and a Venturi injector is needed in any case, with Primozone high concentration the injection system will be much smaller, much cheaper and much less energy-consuming than with traditional low concentration.

  • OPEX savings from day one

Last but not least, power plants pay a low cost for electricity. Oxygen instead won’t likely be available in the immediate surroundings of the plant and might be very expensive. That’s when powering up the generator and running at high concentration can lead to significant OPEX savings.



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