Cooling Towers

Cooling Towers

Cooling towers or heat rejection devices are used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to reject process heat and cool the working fluid to near the wet-bulb air temperature or rely solely on air to cool the working fluid to near the dry-bulb air temperature.

Common applications include cooling the circulating water used in oil refineries, chemical plants, power plants and building cooling. As industry develops more in countries like Ghana and Nigeria etc. the inherent hazards that come with these developments increase unless remedial actions are taken and preventative policy is in place. The most common hazard from cooling towers is Legionnaires Disease caused by the warming of water such as in the cooling tower. The water then evaporates as vapour or aerosol leading to a proliferation of legionella bacteria which can lead to infection if inhaled.

Environmental Hazards

Legionella have been known for some time to live within amoebae in the natural environment.
Legionella species are the causative agent of the human Legionnaires' disease and the lesser form, Pontiac fever.
Legionella transmission is via aerosols—the inhalation of mist droplets containing the bacteria.

According to recent research The Journal of Infectious Diseases provides evidence that Legionella pneumophilia, the causative agent of Legionnaires disease, can travel at least 6 km from its source by airborne spread.

Temperature Effects

70 to 80 °C (158 to 176 °F) -Disinfection range
At 66 °C (151 °F) –Legionellae die within 2 minutes
At 60 °C (140 °F) –Legionellae die within 32 minutes
At 55 °C (131 °F) –Legionellae die within 5 to 6 hours
50 to 55 °C (122 to 131 °F) -They can survive but do not multiply
20 to 50 °C (68 to 122 °F)-Legionellae growth range
35 to 46 °C (95 to 115 °F) -Ideal growth range
Below 20 °C (68 °F) –Legionellae can survive but are dormant


Chemical Treatment
1. Short term -Cl2, must be repeated every 3 to 5 weeks, corrosion factors
2. Long term -Cl2, takes up to 17 months for system saturation
Non-Chemical Treatment
1. Short term -Thermal eradication -must be repeated every 3 to 5 weeks
2. Long term -Industrial size copper silver ionisation (Ionization) technology

Advantages of using XzioX

An Oxidative Process Hygiene System based on in-situ Chlorine Dioxide generation
Designed to be competitive with other Oxidative regimes, e.g., Cl2, Bromination & O3
A unique delivery system for Chlorine Dioxide solution production
The ClO2 being the active component enabling disinfection
Generates 99.99 % pure ClO2
The residuals are sodium sulphate (Na2SO4) and sodium chloride (NaCl)
XzioX delivers a 5 Log reduction within 60 seconds at a concentration of average <50% than
other disinfectants thus XzioX could replace Chlorine at a 5-1 ratio
Complete eradication of all known micro-bacterial material