Mechanisms of PAC in Organic Removal

As a professional Chinese water treatment chemical manufacturer, we produce high-quality polyaluminium chloride (PAC), polyacrylamide, activated carbon, and other chemicals widely used in industrial wastewater, drinking water, and environmental projects. Organic matter in wastewater is a major challenge, and this article explains how PAC can efficiently remove organic matter and how to select the right type.

What Organic Matter Exists in Wastewater?

Organic matter in wastewater includes:

     ● Natural organic matter (NOM): humic acid, cellulose, proteins

     ● Synthetic organics: surfactants, dyes, pesticide residues

     ● Fats and oils: common in food processing and restaurant wastewater

     ● Trace organics: pharmaceuticals, antibiotics, cosmetics residues

These cause color, odor, COD increase, and affect downstream treatment processes.

Can PAC Remove Organic Matter?

PAC is a high-performance inorganic coagulant with strong cationic properties. Its mechanisms include:

     ● Charge Neutralization – PAC hydrolyzes to multi-valent aluminum ions, neutralizing negatively charged colloids.

     ● Adsorption & Bridging – PAC molecules form “particle-PAC-particle” structures, enhancing floc formation.

     ● Sweep Flocculation – Aluminum hydroxide precipitates trap fine organic particles.

How to Choose PAC for Different Organic Matter

     ● High organic content wastewater: e.g., food processing, paper mills → high basicity PAC (70–80%)

     ● Low organic or inorganic wastewater: e.g., industrial cooling water → low basicity PAC (40–50%)

     ● Special wastewater: e.g., dye, pharmaceutical wastewater → custom PAC, possibly combined with PAM or activated carbon.

Factors Affecting PAC Organic Removal

     ● Dosage – underdose: poor floc formation; overdose: increases turbidity

     ● pH – 6.5–7.5 favors hydrolysis and coagulation

     ● Mixing intensity – fast mixing then slow mixing promotes floc formation

     ● Temperature – low temperature slows hydrolysis

     ● Wastewater composition – organic molecular weight and type affect PAC selection

PAC Tips & Precautions

     ● Conduct jar tests to find optimal dosage

     ● Use multi-point dosing for uniform floc formation

     ● Combine with PAM to improve dewatering

     ● Store in dry, sealed conditions to prevent caking and moisture absorption

FAQ

Q1: Can PAC remove all organic matter?
A1: PAC mainly removes colloidal and suspended organic matter; for dissolved organics, combine with PAM or activated carbon.

Q2: How to choose PAC for different wastewater?
A2: Select high or low basicity PAC according to organic content; special models can be customized.

Q3: What happens if dosage is incorrect?
A3: Underdose: slow floc formation; overdose: water turbidity increases.

Q4: Should PAC be combined with other chemicals?
A4: Yes, depending on water quality, PAC can be combined with PAM or activated carbon to improve organic removal efficiency.