Ozone

Ozone is a gas that is produced from the dissociation of an oxygen based feed gas that reacts with other oxygen molecules to form ozone.

Ozone treatment for cooling tower water offers an alternative to the conventional applications of chemical biocides and corrosion/scale inhibitors. However, for it to be an effective alternative for use in cooling water systems, any treatment program must be able to control three main factors:

  • Corrosion of pipes and chillers
  • Scaling in pipes and chillers
  • Microbial growth (bacteria, Legionella, algae)

Ozone as a biological agent

Ozone is a powerful biocide and viricide that will oxidize many organic and inorganic substances. This strong oxidising property has made ozone an effective chemical for water treatment for nearly a century.

Due to its unstable nature, ozone has a high oxidation potential which allows it to interact with microbiological species to great effect. It outperforms common chlorine/bromine based disinfection systems in the treatment of bacteria, viruses and legionella.

Ozone and Corrosion Protection

Due to its strong oxidising potential there is often a concern that the use of ozone will lead to an increase in corrosion within the water system. However, due to the low concentrations of ozone required for microbiological control coupled with its short half-life, its oxidative corrosion effects are minimized.

Moreover, the effectiveness as a biocide minimizes significant corrosion effects induced by microbiological activity. As well as this, ozone treatment has been shown to increase the corrosion protection by forming a passive film covering and protecting the exposed surface.

Ozone and Scaling Protection

Another major concern requiring focus is the prevention of mineral build-up on equipment surfaces during operation. Most commonly dissolved calcium and magnesium will be deposited onto equipment surfaces forming a solid scale that can decrease equipment performance and/or life-span.

This ion deposition is aided by the presence of a biofilm that forms on walls and other components of the system. Essentially, this biofilm acts as an adherent for these dissolved solids. Over time, deposition of organic and inorganic matter atop this biofilm will see increases in scale thickness. Ozone can loosen and remove the scale if the biofilm is present as it oxidises and breaks down this adherent material.

Advantages of Ozone

  • During the last 20 years technological improvements have made smaller-scale, stand-alone commercial ozone generators both economically feasible and reliable.
  • As ozone is made of oxygen and reverts to pure oxygen, it vanishes without a trace once it has been used. Compare this with other disinfectants.
  • When ozone disinfects or breaks down harmful bacteria or pollutants, there are generally no by-products, unlike most disinfecting agents.
  • Ozone can be used as a singular microbiological treatment whilst chlorine based treatment systems often require a primary and secondary biocide to treat both bacteria and legionella.
  • Ozone is generated onsite, and thus, there are fewer safety problems associated with shipping and handling.

Ozone Generation and Injection

Ozone is generated by disassociating oxygen molecules from each other. This is done either by passing clean air across a high voltage plain or over a UV light.

In order to ensure this feed air is ‘clean’ the generator unit (Figure 1) is housed in a sealed, air-conditioned room to protect the generator from high temperature, particulate contamination and humidity.

For the generator to produce ozone, a vacuum must be present on the ozone output line to force gaseous flow of air/ozone through the system. This is typically done with the use of a circulation pump and venturi-injection system (Figure 3).

When pressurized water enters this venturi-injector system (Figure 2), it is constricted toward the injection nozzle resulting in a high-velocity jet stream. This increase in velocity across the injection nozzle results in a decrease in the absolute pressure of the system, which creates a vacuum, enabling the generated ozone to be drawn through the suction port and injected into the water stream. As the jet stream is diffused toward the injector outlet, its velocity reduces and it is returned to the cooling tower.

ozone1Figure 1. Ozone Generation Unitozone2Figure 2 Ozone Injection Pointsozone3Figure 3 Venturi-Injection with circulation pumps

 

Hydro Flow is capable of providing a number of services regarding the use of ozone water treatment systems. We can design, install and commission new systems that will meet all your water treatment requirements. We can also conduct servicing, repairs and optimize current ozone systems to ensure that you are well protected against scale, corrosion, and biological activity. With years of expertise and experience working with ozone, coupled with its proven economic and environmental advantages, ozone could be the perfect solution to your water treatment problems.