Polyaluminum Chloride Lose Efficiency in Cold?

2025-11-28

As a professional Chinese manufacturer of water treatment chemicals with over 28 years of experience, we’ve worked with customers in Russia, Mongolia, Finland, and Norway, who often ask:“Why does PAC not work well in winter?”

The answer lies in temperature-dependent reaction efficiency — PAC’s flocculation ability decreases sharply when water temperature drops below 10°C.

Temperature Requirements for PAC Performance

Polyaluminum Chloride works best under moderate temperatures.
Its efficiency is closely related to temperature, pH, and mixing conditions.

⚪Optimal range: 15°C–35°C

⚪Below 10°C: Hydrolysis rate decreases

⚪Below 5°C: Floc formation becomes incomplete

This is why cold countries experience poor coagulation results in winter.

Common Problems of PAC in Cold Regions

In cold water or near-freezing conditions, PAC often faces the following issues:

1. Slow floc formation

2. Poor sedimentation performance

3. Low solubility and possible crystallization

4. Overdosing without improvement

5. Unstable effluent and higher turbidity

Why Does PAC Efficiency Drop in Cold Water?

PAC’s performance depends on four key steps — hydrolysis, charge neutralization, adsorption, and sedimentation.
Cold temperatures negatively affect each stage:

● Reduced hydrolysis rate → fewer active aluminum species (Al₁₃);

● Lower particle collision frequency → less effective floc formation;

● Slower reaction kinetics → reduced adsorption and bridging;

● Decreased PAC solubility → limited reaction with suspended solids.

How to Improve PAC Efficiency in Cold Climates

For regions like Northern Europe, Russia, and Mongolia, we recommend:

→ Use High-Basicity PAC – maintains better hydrolysis activity in low temperatures.

→ Combine with Cationic PAM – enhances floc formation and settling rate.

→ Pre-dissolve PAC with warm water (≈30°C) – accelerates activation.

→ Increase mixing and reaction time – allows full contact and reaction.

→ Prevent freezing during storage – keep liquid PAC indoors or insulated.

The reduced performance of PAC in cold water is a natural temperature effect, not a product flaw.
By selecting the right grade, optimizing dosage, and using coagulant aids, excellent results can still be achieved even in freezing conditions.

As a leading PAC supplier from China, we provide customized solutions for different climates and water characteristics — ensuring stable, clear, and efficient water treatment year-round.