Precautions for the Use of Non‑Oxidizing Biocides

Precautions for the Use of Non‑Oxidizing Biocides

Non‑oxidizing biocides effectively inhibit or kill microorganisms through non‑oxidative mechanisms and are widely used in industrial water treatment, medical disinfection, food processing, and other fields. However, their use must follow strict protocols to avoid safety risks, environmental hazards, and equipment damage. The key precautions for using non‑oxidizing biocides are as follows:

I. Concentration Control and Accurate Dosage

Strictly Follow the Recommended Concentration

The bactericidal effect of non‑oxidizing biocides is closely related to concentration, but excessive use may lead to:

Equipment corrosion: Corrosivity of chlorophenols to metals (e.g., carbon steel, copper) increases with concentration.

Ecological risks: High concentrations may poison aquatic organisms and damage the ecological balance.

Cost waste: Increased operating costs without additional benefits.

Recommendation: Determine the optimal dosage through laboratory tests according to water quality, microbial species, and equipment materials. The general concentration is controlled at 5–10 ppm (subject to the product manual).

Staged Dosing

For stubborn microorganisms (e.g., biofilms), a shock dosing strategy can be adopted:

high concentration at the initial stage for rapid killing, and low concentration later to maintain efficacy.

II. Compatibility Testing and Chemical Matching

Avoid Mixing with Cationic Agents

Non‑oxidizing biocides such as chlorophenols and quaternary ammonium salts may react with cationic scale inhibitors (e.g., polyacrylates), causing precipitation or reduced efficacy.

Recommendation: Conduct compatibility tests before use, or select anionic or non‑ionic water treatment chemicals.

Alternate Use with Oxidizing Biocides

Long‑term single use of non‑oxidizing biocides may lead to microbial drug resistance.

Recommendation: Alternate with oxidizing biocides (e.g., chlorine, ozone) to enhance long‑term bactericidal effect and delay resistance development.

III. Water Quality Conditions and pH Adaptation

Adapt to Water Quality Characteristics

The stability of non‑oxidizing biocides is significantly affected by water quality:

High turbidity water: Remove suspended solids by filtration or sedimentation in advance to avoid adsorption and inactivation of chemicals.

High temperature water: Select heat‑resistant biocides (e.g., isothiazolinones) to avoid decomposition and failure.

Water containing reducing substances: Avoid using biocides easily reduced (e.g., some organic amines).

Control the pH Range

Sensitivity to pH varies greatly among different biocides:

Quaternary ammonium salts: Applicable at pH 6–10; easy to precipitate under acidic conditions.

Isothiazolinones: Applicable at pH 3–9; may decompose under strong alkaline conditions.

Recommendation: Adjust the system pH according to the chemical instructions, or select products with a wide pH adaptation range.

IV. Safety Protection and Operating Procedures

Personal Protective Measures

Non‑oxidizing biocides may irritate the skin, eyes, or respiratory tract:

Operators: Wear protective gloves, goggles, and a gas mask to avoid direct contact.

Emergency treatment: In case of skin contact, rinse immediately with plenty of water; if ingested, seek medical attention immediately with the product label.

Storage and Transportation Requirements

Keep away from light: Some biocides (e.g., isothiazolinones) decompose easily under light and should be stored in a cool and dry place.

Keep away from fire sources: Some organic solvent‑based biocides (e.g., alcohol‑containing) are flammable and must be kept away from open flames.

Separate storage: Avoid mixing with oxidizers, acids, etc., to prevent chemical reactions.

V. Environmental Impact and Emission Control

Biodegradability Assessment

Prioritize biodegradable non‑oxidizing biocides (e.g., isothiazolinones) to reduce long‑term environmental pollution.

Avoid using persistent organic pollutants (e.g., some chlorophenols), whose degradation products may be toxic.

Pre‑Discharge Treatment

Wastewater containing biocides must be treated to meet standards before discharge:

Biological treatment: Use microorganisms to degrade organic matter (ensure biocide concentration does not inhibit microbial activity).

Chemical oxidation: Decompose residual chemicals through advanced oxidation technologies (e.g., ozone, Fenton’s reagent).

VI. Equipment Maintenance and Monitoring Management

Regular Equipment Cleaning

Biocides may remain on equipment surfaces or pipelines, forming secondary pollution sources:

Cleaning cycle: Perform chemical cleaning every 3–6 months according to system operation.

Cleaning agent selection: Avoid cleaning agents that react with biocides (e.g., acidic cleaners with quaternary ammonium salts).

Microbial Monitoring and Drug Resistance Management

Regular testing: Monitor microbial quantity via colony counting or ATP bioluminescence to evaluate bactericidal effect.

Resistance warning: If microbial quantity rebounds or species change, adjust biocide type or concentration in time.

VII. Precautions for Special Scenarios

Food Processing Field

Only food‑grade non‑oxidizing biocides (e.g., isothiazolinones) that comply with GB 2760 National Food Safety Standard – Standards for the Use of Food Additives must be used.

Residue control: Strictly follow the flushing process to ensure biocide residues are below safety limits.

Medical Disinfection Field

Prioritize biocides with low skin irritation (e.g., quaternary ammonium salts) and avoid mixing with disinfectants (e.g., alcohol).

Sterilization verification: Verify sterilization effect using biological indicators (e.g., Bacillus stearothermophilus).

VIII. Case Warnings and Experience Summary

Case 1: Cooling Tower Corrosion Accident in a Petrochemical Enterprise

Cause: Excessive dosing of chlorophenol biocides without compatibility testing, resulting in corrosion and perforation of copper pipes.

Lesson: Strict dosage control, advance testing, and use of corrosion‑resistant equipment.

Case 2: Product Deterioration Incident in a Food Factory

Cause: Incomplete flushing of non‑oxidizing biocide residues, leading to microbial resistance under low‑concentration chemicals.

Lesson: Strengthen flushing process management and regularly rotate biocide types.