Ozone

What is ozone, and where is it found?

The ozone molecule (O₃) is composed of three oxygen atoms (O). In nature, it is found in the atmosphere, where it is gaseous and colorless, and at different concentrations between 10 and 40 kilometers in altitude above sea level.

The highest concentrations of ozone are found in the stratosphere, at 15 kilometers in altitude, where it is formed by the dissociation of oxygen molecules due to ultraviolet radiation. The area of the stratosphere with the highest concentrations of ozone is called the ozone layer or ozonosphere.

In industrial contexts, ozone is also known as activated oxygen.

What types of ozone are there?

There are three main types of ozone:

• Atmospheric ozone: what is found in the air naturally, with a variable but very low density.
• Stratospheric ozone: what makes up the ozone layer. This layer contains 90% of the ozone that exists in the Earth’s atmosphere, and it is about 40 kilometers thick. The ozone layer absorbs almost 100% of the high-frequency ultraviolet radiation from the sun, enabling terrestrial life as we know it.
  During the ’70s, the ozone layer suffered significant density losses due to chlorofluorocarbon compounds (CFCs) generated by various human activities. This phenomenon is called the hole in the ozone layer, and it has been a cause for concern ever since. Thanks to a set of measures introduced during the ’80s, ozone levels stabilized during the following decade, and in the 2000s, the process began to reverse. Now, the ozone layer is almost restored, and scientific studies suggest that it will be completely regenerated in a couple of decades.

• Tropospheric ozone or ground-level ozone: released by photochemical reactions between volatile organic compounds (VOCs) released from combustion and nitrogen oxides (NOx). It is part of the so-called photochemical smog, which can be seen as a haze over polluted areas, especially in hot times of the year. This type of ozone is also known as bad ozone, and it is harmful to our health.

What are the main applications of ozone?

The primary practical application for ozone is air and water purification. According to the World Health Organization (WHO), it is the most efficient disinfectant. The advantages of ozone purification processes over others are many:

• It effectively eliminates viruses, bacteria, algae, spores, and fungi.
• It reduces the Total Dissolved Solids (TDS) and the Total Suspended Solids (TSS) in water.
• It reduces the Total Suspended Particulate (TPS) in the air.
• It leaves no residue.
• It does not affect pH.
• It eliminates odors.
• The reactions only produce oxygen, so the processes are non-polluting.

Thanks to all this, ozone has wide applications for:

• Water treatment plants.
• Disinfection at swimming pools, spas, water parks, and other forms of water-related entertainment.
• Maintenance at aquariums and drinking troughs in zoos and other structures related to animal protection.

Industrially, ozone is used for:

• Manufacturing various health and hygiene products.
• Disinfecting fruits and vegetables in agro-industrial processes.
• Bleaching paper pulp without using chlorine derivatives.
• Carrying out various treatments related to health and aesthetics.
• Fish farming.

What are the disadvantages of using ozone in an industrial setting?

Due to its high instability and reactivity, ozone cannot be stored and transported for application; instead, it must be produced in situ, so the industrial processes that involve it have to include its production.

The industrial production of ozone is usually carried out using a relatively pure source of oxygen and an ozone generator, which produces a high electrical voltage known as the corona effect. It is an electrical phenomenon that is produced by the ionization of a gas.