Ozone as a disinfectant
Ozone Chemical Characteristics
Ozone is an extremely potent oxidising agent in a gaseous form, capable of breaking apart aromatic and alkene functional groups in chemical compounds. This makes it an effective agent for use in wastewater treatment plants, as it can functional as both, a potent antimicrobial agent, as well as a way to mineralise micro-pollutants such as drugs, antibiotics and dyes. Chemical mineralisation is when a chemical compound such as, a dye, is chemically broken apart typically through aggressive oxidation processes to: H2O, CO2, NH3 and NO3-2. This oxidation process is referred to as ozonation or ozonolysis.
The main problem with the use of ozone is that it is toxic upon inhalation; Occupational Safety and Health Administration (OSHA) require that ‘workers not be exposed to an average concentration of more than 0.10 ppm for 8 hours’ and National Institute of Occupational Safety and Health (NIOSH) recommend that ‘an upper limit of 0.10 ppm, not to be exceeded at any time’.
How Ozone is Industrially Formed
Ozone is formed by exposing a stream of air to electricity, the electricity supplies enough energy to split a number of oxygen molecules into their atoms, which then subsequently collide and react with other oxygen molecules resulting in the formation of ozone. This stream of ozone is then injected into water, which is then used for disinfection purposes. This is a typical set-up for wastewater treatment plants.
Industries Where Ozone is Being Utilised
The use of ozone is found in multiple different sectors, with two main principle purposes:
- Sterilisation; clean in place for food & drink industries & wastewater treatment plants.
- Mineralisation of dyes and drugs; in wastewater treatment plants.
Drawbacks of Ozone Use
There are a few drawbacks when it comes to using ozone as a steriliser in food industries, it requires specialist equipment to produce the ozone being used; whether this is through high voltage electricity or use of UV-C lamps to generate the ozone on site. It also requires, in some applications, the storage of oxygen gas. The potential of exposure to the gas is also a major safety concern for users, which requires routine checks for exposure limits in the workplace. This risk can be reduced for applications where the use is in sealed environments away from the users, for example wastewater treatments plants. It is not, however, appropriate when the use of ozone in aqueous solutions is in open-air environments; for example, in applications where submersion of items is common, such as salad washing.
