What is the Difference Between Oxidizing and Non-oxidizing Biocides?

06/05/2025 • Giovanni Medeiros

The main difference between oxidizing and non-oxidizing biocides lies in their mode of action against microorganisms:

Oxidizing Biocides:

  • These biocides control microorganisms by oxidizing the cell structure and disrupting the nutrient flow across the cell wall.
  • They are fast-acting and less costly compared to non-oxidizing biocides.
  • Oxidizing biocides can induce corrosion on metals due to their redox potential, and they are often used in combination with corrosion inhibitors.
  • They are sensitive to variations in pH and temperature, making them dependent on the operational conditions of the system.

Non-Oxidizing Biocides:

  • These biocides work through various processes, such as interfering with reproduction, stopping respiration, or breaking the cell wall.
  • They are generally slow-acting and require several hours up to a day to achieve the desired effect.
  • Non-oxidizing biocides are less effective against extracellular polymeric substances (EPS) compared to oxidizing biocides.
  • The selection of a non-oxidizing biocide depends on factors such as water pH, retention time, efficacy against various bacteria, fungus, and algae, biodegradability, toxicity, and compatibility with other chemistry.

In some cases, non-oxidizing biocides are found to be more effective and convenient than oxidizing biocides, leading to their use together in various conditions, such as cooling water systems.

Comparative Table: Oxidizing vs Non-oxidizing Biocides

Here is a table comparing oxidizing and non-oxidizing biocides:

Characteristic Oxidizing Biocides Non-oxidizing Biocides
Mechanism of Action Control microorganisms by oxidizing the cell structure and disrupting cellular processes Control microorganisms by interfering with reproduction, stopping respiration, or breaking the cell wall
Examples Ammonium bromide, ammonium sulfate, chlorine gas, chlorine dioxide, hydrogen peroxide, halogenated alkylhaydantoin, peracetic acid, sodium hypochlorite, and sodium bromide 1,2-Benzisothiazolin-3-on, 2-Bromo-2-nitropropane-1,3-diol, 5-Chloro-2-methyl-4-isothiazolin-3-on, Diethyldithiocarbamate, N,N-Dimethyl-N,N-didecyl ammonium chloride, benzalkonium chloride, 2,2-Dibromo-3-nitrilopropionamide, Glutaraldehyde, Methylene bisthiocyanate, 2-Methyl-4-isothiazolin-3-on
Effectiveness Fast-acting and broad-spectrum activity against bacteria, fungi, and algae Effective against specific microorganisms and can control biofilm formation and growth
Cost Less costly compared to non-oxidizing biocides Generally more expensive than oxidizing biocides, but may offer specific advantages for certain applications
Toxicity Low toxicity and easily degradable Can have varying levels of toxicity and biodegradability, depending on the specific biocide
Water Conditions Increases the redox potential (ORP) value of the system, which can be detected by sensors May be affected by water pH, retention time, and other factors

Both oxidizing and non-oxidizing biocides are used to control the growth of microbes in various applications, such as cooling water systems and industrial processes. In some cases, a combination of both types of biocides is used to optimize microbial control, protect equipment, and increase operational efficiency.

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