Biocide is generally referred to as any substance or mixture that has the ability to destroy or inhibit the growth of microorganisms (such as bacteria, fungi, viruses, algae, and even some larger organisms).
Scientific definition
Biocides are substances used to protect humans, animals, food, or equipment against the harmful effects of microorganisms. This word consists of two parts:
Bio = life, living organism
Cide = killer
Therefore, its literal meaning is “killer of living organisms” (of course, it refers to microscopic organisms, not humans or animals).
- Classification based on chemical nature (main composition)
This classification is based on the dominant chemical group in the active composition of the biocide:
Types of biocides:
-Based on peracetic acid (Peracetic Acid): strong oxidizing compounds.
-Based on Dimethylbenzoalkonium Chloride (DMBAQ): A type of Quaternary Ammonium Compound (Quats) that has cationic properties.
-Isothiazolines: Includes substances such as CMIT/MIT (common in cosmetics and industrial materials).
-Glutaraldehyde: An active aldehyde that has non-oxidizing properties.
-Dibromonitrilopropylamide (DBNPA): A fast-acting non-oxidizing biocide.
-Tetrakishydroxymethylphosphonium sulfate (THPS): Phosphorus compounds often used in the oil and gas industries.
-Bleach: Essentially a solution of sodium hypochlorite.
- Classification by mechanism of action
This method determines how microorganisms are killed or inhibited and often overlaps with chemical classification:
a) Oxidizing Biocides
These substances cause the loss of nutrients by taking electrons from bacteria (oxidizing them), resulting in cell death.
Examples: Sodium hypochlorite (Javel water), chlorine, bromine, ozone, hydrogen peroxide.
Note: Their high oxidizing power may cause corrosion of metals.
b) Non-oxidizing Biocides
These substances usually act by targeting specific cellular structures and do not have strong oxidizing properties.
Common mechanisms: dissolving the lipid cell membrane of microorganisms, binding to external or internal structures of the cell, or interfering with metabolic enzymes.
Examples: Isothiazolinones, glutaraldehyde, quaternary ammonium compounds (Quats), DBNPA, THPS.
Applications of Biocides:
Here are the most important applications of biocides in various industries:
- Oil & Gas Industry
This is one of the most critical areas of biocides use, as microorganisms can cause severe damage:
-Microbial Corrosion Control (MIC): Sulfate Reducing Bacteria (SRB) and other microorganisms can cause severe corrosion of pipes, tanks, and water injection equipment (the same issue raised in your previous question about natural gas erosion).
-Biofouling Prevention: The formation of biofilms that lead to reduced fluid flow, filter blockage, and reduced extraction efficiency.
-Drilling and Fracturing Fluid Protection: Preventing the breakdown of chemicals used in drilling operations by microbes.
- Water Treatment
-Drinking Water: Disinfection of water to remove pathogens and ensure safety of consumption.
-Cooling Tower Water: Control the growth of Legionella (the causative agent of Legionnaires’ disease) and prevent biofouling that reduces heat transfer efficiency.
-Industrial Process Water: Disinfection of water used in various manufacturing processes. - Wood and Building Products
-Wood Preservation: Use of wood preservatives to protect against fungi and insects that cause decay.
-Paints & Coatings: In-can biocides prevent product spoilage in liquid form, and dry-film biocides prevent mold and algae growth on painted surfaces. - Pulp and Paper Industries
-Slime Control: The formation of biofilms in papermaking machinery causes paper sheet tearing and a decrease in the quality of the final product. Biocides are used to keep the system clean. - Industrial Product Maintenance
-Cutting Fluids and Metalworking Lubricants: These emulsions are rich in water and organic matter that quickly host the growth of bacteria, causing unpleasant odors, corrosion, and reduced fluid performance.
-Adhesives, Sealants, and Caulks: To prevent the decomposition of these materials during storage and use. - Consumer and Hygiene Materials
-Cosmetics and Personal Care Products: As a preservative to prevent microbial growth in creams, lotions, shampoos, and other water-based products to ensure consumer safety throughout the product’s shelf life.
In short, wherever there is water, organic matter, or environmental conditions suitable for the growth of microorganisms and this growth leads to damage, contamination, or quality degradation, the use of biocides is essential to maintain performance and safety.