In brewery wastewater treatment, the selection and application of polyacrylamide (PAM) significantly impact treatment efficiency and operational costs. Below is a detailed analysis of PAM selection and performance based on brewery wastewater characteristics.

1. Characteristics of Brewery Wastewater

High organic content: Rich in sugars, proteins, and starches (high COD/BOD).

Suspended solids (SS): Yeast residues, grain fibers, and colloidal particles.

Variable水质 (pH 4–6): Fluctuations due to brewing, fermentation, and cleaning processes.

High biodegradability: Suitable for biological treatment but requires pretreatment to reduce organic load.

2. Key Factors in PAM Selection

(1) Ionic Type Selection

Cationic PAM (CPAM)

Application: Sludge dewatering (e.g., after activated sludge process).

Function: Neutralizes negatively charged colloids, improves sludge settling, and reduces moisture content (to ≤80%).

Recommended: Medium-high charge density (60–80%), molecular weight (MW) 8–12 million.

Anionic PAM (APAM)

Application: Primary sedimentation (pretreatment for SS removal).

Function: Bridges suspended particles via adsorption, forming large flocs.

Recommended: Medium-high MW (10–15 million), 10–30% hydrolysis.

Non-ionic PAM (NPAM)

Application: Neutral or fluctuating pH conditions, or when metal ions are present.

Function: Relies on hydrogen bonding; often used with coagulants (e.g., PAC).

(2) Molecular Weight (MW) Selection

High SS wastewater: High MW (≥15 million) for better bridging.

Soluble organics: Lower MW PAM may assist coagulation.

(3) Dosage & Mixing

Dissolution: 0.1–0.3% solution with gentle stirring (avoid shear degradation).

Dosage: 1–10 ppm (determined via jar testing).

3. Treatment Performance Comparison

  Parameter                                   APAM (Pretreatment)                  CPAM (Sludge Dewatering)

COD Removal                                   30–50% (with PAC)                 Indirect (sludge thickening)

SS Removal                                              70–90%                                                 –

Sludge Cake Moisture                                                   –                                           75–80%

Settling Speed                                  Significantly improved               Enhanced compressibility

4. Key Considerations

Jar Testing: Essential due to wastewater variability.

pH Adjustment: Optimal PAM performance at pH 6–8 (lime may be needed for acidic wastewater).

Safety: Ensure acrylamide monomer content ≤0.05% (regulatory compliance).

Cost-Benefit: CPAM is more expensive but improves dewatering efficiency.

5. Typical Treatment Process

Flow: Screening → Equalization (pH adjustment) → PAC + APAM coagulation → UASB/Aerobic Process → CPAM sludge dewatering.

By selecting the appropriate PAM type, breweries can enhance wastewater treatability, improve sludge handling, and reduce disposal costs.