Peracetic acid (C2H4O3) is a mixture of acetic acid (CH3COOH) and hydrogen peroxide (H2O2) in a watery solution. It is a bright, colorless liquid that has a piercing odor and a low pH value (2,8). Peracetic acid is produced by a reaction between hydrogen peroxide and acetic acid:
O O || || CH3-C-OH + H2O2 -> CH3C-O-OH + H2O
acetic acid + hydrogen peroxide -> peracetic acid
Peracetic acid can also be produced by oxidation of acethaldehyde. Peracetic acid is usually produced in concentrations of 5-15%. When peracetic acid dissolves in water, it disintegrates to hydrogen peroxide and acetic acid, which will fall apart to water, oxygen and carbon dioxide. Peracetic acid degradation products are non-toxic and can easily dissolve in water. Peracetic acid is a very powerful oxidant; the oxidation potential outranges that of chlorine and chlorine dioxide.
What are the applications of peracetic acid?
Peracetic acid is used mainly in the food industry, where it is applied as a cleanser and as a disinfectant. Since the early 1950’s, acetic acid was applied for bacteria and fungi removal from fruits and vegetables. It was also used for the disinfection of recicled rinsing water for foodstuffs. Nowadays peracetic acid is applied for the disinfection of medical supplies and to prevent bio film formation in pulp industries. It can be applied during water purification as a disinfectant and for plumming disinfection. Peracetic acid is suitable for cooling tower water disinfection; it affectively prevents bio film formation and controls Legionella bacteria.
How does peracetic acid disinfection work?
Peracetic acid as a disinfectant oxidizes the outer cell membranes of microorganisms. The oxidation mechanism consists of electron transfer. When a stronger oxidant is used, the electrons are transferred to the microorganism much faster, causing the microorganism to be deactivated rapidly.
Table 1: oxidation capacity of various disinfectants
EV (elektronic volts)
Peracetic acid affectivity
Peracetic acid can be applied for the deactivation of a large variety of pathogenic microorganisms. It also deactivates viruses and spores. Peracetic acid activity is hardly influenced by organic compounds that are present in the water. However, pH and temperature do influence peractetic acid activity. Peracetic acid is more effective when the pH value is 7 than at a pH range between 8 and 9. At a temperature of 15 °C and a pH value of 7, five times more peracetic acid is required to affectively deactivate pathogens than at a pH value of 7 and a temperature of 35 °C.
When cooling tower water is tapped from a river or lake, and must be discharged into the same water body after it has been used, it must meet certain discharge demands. Aditionally, the water temperature may not be too high, because warm water has a low oxygen content, which promotes algal growth. This can cause fish mortality and a decrease in water biodiversity.
Discharge demands for cooling tower water in the USA are mentioned in the Clean Water Act (CWA) and are established by the Environmental Protection Agency (EPA).