How Does PAC Influence Sludge Settling?

As a leading Chinese manufacturer of water treatment chemicals, we supply high-quality Polyaluminum Chloride (PAC) worldwide. In sludge settling, PAC significantly improves solid-liquid separation and effluent quality. 

Three Key Mechanisms of PAC in Sludge Settling

1) Charge Neutralization

    ● PAC hydrolyzes to form cationic polymeric ions

    ● Neutralizes negative charges on sludge colloids

    ● Reduces electrostatic repulsion

2) Adsorption Bridging

    ● PAC active sites adsorb multiple sludge particles

    ● Forms a “particle-PAC-particle” network

    ● Increases floc size and density

3) Sweep Flocculation

    ● PAC forms aluminum hydroxide precipitate networks

    ● Captures fine suspended solids

    ● Effective for micron-sized particles

Five Critical Factors Affecting PAC Settling Efficiency

Tips to Optimize PAC Performance

1. Determine optimal dosage via jar tests and floc observation

2. Select appropriate PAC type: high-basicity (70–80%) for organic sludge, low-basicity (40–50%) for inorganic

3. Optimize dosing points: post-primary sedimentation, multi-point dosing, fast then slow mixing

4. Combine with other chemicals: PAC + cationic PAM, PAC + lime, PAC + activated carbon

Troubleshooting Common PAC Settling Issues

    ● Small, loose flocs → Increase dosage or adjust pH 6.5–7.5

    ● Turbid supernatant → Optimize mixing, extend settling time

    ● Sludge bulking → Switch to high-basicity PAC or add oxidant

How to Choose Quality PAC

    ● Basicity: 65–75% recommended

    ● Settling speed: 10–15 minutes

    ● Residual aluminum: <0.2 mg/L for drinking water

    ● Complete solubility without residue

For more information or assistance in selecting PAC, contact us for free testing and technical support.

FAQ

Q1: Which sludge types are suitable for PAC?
A1: Organic, inorganic, or mixed sludge; choose PAC basicity based on water quality.

Q2: What is the benefit of PAC + PAM?
A2: PAC initiates flocculation; PAM strengthens flocs for better dewatering.

Q3: How to determine PAC dosage?
A3: Through jar tests and sludge zeta potential measurements.

Q4: PAC residual aluminum limit in drinking water?
A4: <0.2 mg/L to ensure safe water quality.