Mechanisms of PAC in Organic Removal

As a high-efficiency coagulant, PAC removes organic matter through three primary mechanisms:

Charge Neutralization
Hydrolyzed Al³⁴⁺ ions neutralize negative charges on organic molecules

Adsorption Bridging
Forms “organic matter-PAC-organic matter” aggregates

Sweep Flocculation
Al(OH)₃ precipitates encapsulate organic molecules

Typical Treatment Efficiency:

-COD removal: 40-85%

-Color removal: 60-95%

-BOD/COD ratio improvement: 0.2→0.5 (enhanced biodegradability)

In-Depth Analysis of 5 Key Influence Factors

1.PAC Characteristic Parameters

2.Water Quality Factors

pH (Critical Factor)

-Optimal range: 6.0-7.5

-pH<4: Dominant Al³⁴⁴ form, suitable for small organic molecules

-pH>8: Al(OH)₄⁻ dominant, reduced efficiency

Temperature

-Reaction rate increases 1.5-2× per 10°C rise

-40°C causes floc structure deterioration

Organic Matter Properties

-Molecular weight: 500-5000Da most removable

-Polarity: Non-polar > polar organics

PAC Treatment Solutions for Different Wastewater Types

1.Textile Dyeing Wastewater

-Characteristics: High color, dye molecules

-Special PAC: High-basicity composite PAC

-Performance:

   *Color removal >90%

   *COD removal 50-70%

2.Paper Mill Wastewater

-Challenge: Hard-to-degrade lignin

-Process:

   *PAC (200mg/L) + PAM (1mg/L)

   *pH adjustment to 6.5-7.0

3.Food Processing Wastewater

-Feature: High BOD/COD ratio

-Optimization:

   *Staged PAC dosing

   *Combined biological treatment

4.Petrochemical Wastewater

-Difficulty: Oil-containing organics

-Solution:

   *Demulsification pretreatment

   *Hydrophobic-modified PAC

5 Practical Techniques to Enhance PAC Efficiency

1.Oxidant Combination
PAC + H₂O₂ (Fenton effect) → 15-25% COD removal increase

2.Dual Coagulant System
PAC (primary) + PAM (aid) → 50% faster settling

3.Precision pH Control
Online pH monitoring + automated dosing

4.Sludge Recirculation
10-15% return flow → 20% PAC reduction

5.Gradient Dosing Strategy
60% initial dose + 40% after 10 minutes → Adapts to quality fluctuations

Troubleshooting Poor PAC Performance

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