How to Select Non‑Oxidizing Biocides for Industrial Use

How to Select Non‑Oxidizing Biocides for Industrial Use

The selection of non‑oxidizing biocides for industrial applications requires a comprehensive evaluation of five core factors: antimicrobial spectrum, environmental adaptability, safety, cost‑effectiveness, and process compatibility, with targeted screening based on specific industrial scenarios. A detailed analysis is provided below:

I. Antimicrobial Spectrum: Cover Target Microorganism Types

Select products with corresponding antimicrobial spectra according to the dominant microorganisms in industrial water (e.g., bacteria, fungi, algae, sulfate‑reducing bacteria):

Quaternary ammonium salts (e.g., dodecyldimethylbenzylammonium chloride):

Effectively kill bacteria, fungi, and algae, with slime‑stripping properties. Suitable for circulating cooling water systems in petroleum and chemical industries.

Isothiazolinones (e.g., Kathon):

Broad‑spectrum antimicrobial activity, especially effective against stubborn bacteria such as sulfate‑reducing bacteria and iron bacteria. Commonly used in oilfield water injection and reverse osmosis membrane pretreatment.

Chlorophenols (e.g., sodium pentachlorophenate):

Strong permeability to slime and biofilms, but high toxicity. Suitable for industrial circulating water disinfection (attention to environmental restrictions required).

Organic aldehydes (e.g., glutaraldehyde):

Active aldehyde groups kill bacteria not covered by quaternary ammonium salts, but weak penetration. Often used in combination with quaternary ammonium salts.

Heterocyclic compounds (e.g., imidazoline, triazine derivatives):

Kill microorganisms by damaging DNA structure, low dosage but relatively high cost. Suitable for high‑requirement scenarios.

Case: A chemical plant circulating water system used isothiazolinones to react irreversibly with microorganisms, achieving a killing rate of over 99% against common bacteria, fungi, and algae.

II. Environmental Adaptability: Match Water Quality and Operating Conditions

pH value:

Non‑oxidizing biocides are less affected by pH, but the applicable range must be confirmed.

Example: isothiazolinones (pH 3.5–9.5), quaternary ammonium salts (pH 6–10).

Water composition:

Avoid organic sulfur biocides (e.g., methylene dithiocyanate) in water with high sulfide content, as efficacy will be reduced.

Temperature and turbidity:

Prioritize low‑volatility, high‑temperature‑resistant (≤60 °C) liquid or slow‑release agents (e.g., isothiazolinones) to reduce volatile pollution and leakage risks.

Salinity and hardness:

Select highly stable agents (e.g., quaternary ammonium salts) for high‑salinity, high‑hardness water to avoid inactivation via reaction with ions.

Case: An oil refinery circulating water system adopted a composite biocide of isothiazolinone derivatives and 1427 + glutaraldehyde, matching its water quality and achieving significant disinfection efficacy.

III. Safety: Reduce Environmental and Health Risks

Toxicity:

Prioritize low‑toxicity, biodegradable products (e.g., isothiazolinones) and avoid highly toxic chlorophenols (e.g., sodium pentachlorophenate).

Volatility:

Oxidizing biocides (e.g., sodium hypochlorite) easily release irritating gases. Non‑oxidizing biocides (e.g., isothiazolinones) have low volatility, making them more suitable for enclosed industrial environments.

Environmental certification:

Choose products labeled “biodegradable”, “low VOC”, or “industrial‑grade environmental certification” to minimize environmental pollution.

Case: A power plant circulating water system used isothiazolinone biocides, which are harmless to the environment and operators, with low volatility, meeting environmental protection requirements.

IV. Cost‑Effectiveness: Balance Cost and Performance

Unit price and dosage:

Non‑oxidizing biocides are usually more expensive than oxidizing ones, but require lower dosages (e.g., isothiazolinones >0.5 mg/L), potentially lowering long‑term overall costs.

Combined synergism:

Compounding agents with different mechanisms (e.g., quaternary ammonium salt + glutaraldehyde) reduces single‑agent dosage and improves broad‑spectrum activity.

Maintenance cost:

Low corrosiveness to equipment reduces downtime and repair costs caused by corrosion.

Case: A chemical plant alternately used oxidizing and non‑oxidizing biocides.

Oxidizing biocides (e.g., liquid chlorine) controlled daily microbes, while non‑oxidizing biocides (e.g., isothiazolinones) periodically stripped slime, reducing overall costs by 25%.

V. Process Compatibility: Optimize Dosing and Operation

Dosing method:

Prefer closed‑dosing products (liquid or slow‑release) via intelligent metering pumps or PLC‑controlled dosing systems to reduce manual errors.

Dosing location:

Dose at the circulating water pump inlet or the bottom reservoir, avoiding open areas such as cooling tower tops to reduce contact with air.

Dosing time:

Dose during nighttime shutdown or equipment maintenance periods to enhance system circulation and ventilation, reducing volatile diffusion.

Case: A steel plant optimized dosing location (bottom reservoir) and time (nighttime shutdown), reducing isothiazolinone volatilization by 40%.