1. Product Overview

Polyaluminum Chloride (PAC) is a new-type inorganic polymer coagulant with the general chemical formula [Al] ₂(OH)ₙCl₆₋ₙ]ₘ. It is a water-soluble inorganic polymer compound positioned between AlCl ₃ et Al(OH) ₃. As a widely used coagulant in the water treatment industry, PAC plays a significant role in sludge dewatering conditioning.

Henan SECCO Environmental Protection Technology Co., Ltd. est provincial-level innovative SME specializing in the R&D; D, productio, et venditio aquarum chemicalorum, inclusive polyacrylamide et polyaluminium chloridum. Water Treatment Materials Emergency Industrial Park in Gongyi City, Henan Province, the company possesses comprehensive production and R&E. D capabilitates, committed to providing high-quality PAC products and professional technical services.

2. Mechanism of PAC in Sludge Dewatering

PAC improvit dewatering pigmenta per sequentes mechanismos:

1. Charge Neutralizatione: Particulae Sludge normale portant cargas negativas superficie, creant systemam colloidalem stabilem per repulsionem mutuam. PAC hydrolyzat in aqua ut iunctura aluminium positiva cargatur et complexa polynuclear hydroxy-aluminium, quas negativa carga super superficies particularum pulveris neutralizat, potentialem zetae reducit et aggregationem particularum in maxima floribus positiva facit.

2. Adsorption Bridging: Como polymer, catenae moleculae PAC continet grupos active, qui possunt adsorbere multiplicas particulas pulcherrimas, particulas pulcherrimas connectere in maxima aggregata flora per effectos "bridging", accelerantes pulcherrimas et densitatem.

3. Self-Skeletonization: Recent studies reveal that inorganic coagulants not only perform traditional charge neutralization and flocculation during sludge conditioning but also form micro-scale "skeleton-like" networks through in-situ hydrolysis during the early stage of filter cake formation. This structure increases pore coordination numbers by 80%, raises effective porosity by two orders of magnitude, improves absolute permeability by 3.5–4.4 times, and reduces compressibility coefficient by 63%–69%. PAC conditioning can reduce sludge cake moisture content to 63.92%.

Research also shows that 8% PAC pretreatment combined with dialysis dehydration can reduce residual moisture content to 36.2%, with sludge porosity reaching as low as 0.29.

3. Core Advantages of PAC for Sludge Dewatering

1. Minimum Impact on Effluent pH: Compared to traditional aluminum salts (such as aluminum sulfate), PAC hydrolysis is milder and does not cause significant pH reduction in the effluent.

2. Low Dosage and Low Sludge Production: PAC has high active ingredient content, requiring relatively low dosage while producing less chemical sludge, reducing subsequent disposal costs.

3. High Turbidity Removal Efficiency: PAC exhibit excellent coagulation performance, effectively removing suspended solids and colloidal substances, improving supernatant quality.

4. High Floc Strength and Pressure Resistance: PAC forms dense, high-strength flocs particularly suitable for high-pressure dewatering equipment such as vacuum filters and plate-and-frame filter presses.

5. Wide pH Application Range: PAC maintains good coagulation performance across a broad pH range, with optimal performance at pH 5–7.

6. Compatibility with Other Chemicals: PAC can be used in combination with organic polymer flocculants such as polyacrylamide (PAM) for synergistic effects.

4. Selection Guide for PAC

(A) Selection Based on Sludge Characteristics

Different sources of sludge have different physicochemical properties. Considere sequentes factores:

1. Sludge Type

Municipal WWTP Excess Activated Sludge: High organic content and strong colloidal stability—recommend PAC combined with cationic PAM (CPAM). Studies show that sequential addition of PAC followed by CPAM at optimal concentrations of 4% and 0.1% achieves minimum sludge specific resistance of 1.47×10 ⁸ s ²/g, with filtered moisture content reduced to 70.9%.

Industrial Wastewater Sludge: Select appropriate PAC specifications based on wastewater characteristics. Pro exemplo, paper making sludge can be treated with 10% Al ₂O₃ PAC coniunctus cum CPAM.

Water Treatment Plant Sludge: PAC effectively improves thickening and dewater performance.

2. Organic Content of Sludge

High organic content: Select PAC with higher basicity, combined with cationic organic polymers.

Predominantis inorganic sludge: Standard PAC products are suitable.

3. Sludge pH

PAC optimum in pH 5–7 facit. If sludge pH deviates from this range, consider pre-adjusting pH or selecting alternative conditioners.

(B) Selection Based on Dewatering Equipment

1. Plate-and-Frame Filter Press / Vacuum Filter

Recommendatus est: PAC (solus aut combinatus cum PAM)

Reason: PAC forms high-strength, pressure-resistant flocs suitable for high-pressure filtration

Referentia Dosage: 1%–3% of sludge solid weight

2. Prissa / Centrifuge

Recommendus: PAC combined with PAM

Reason: PAC first destabilizes the colloidal system, then PAM provides bridging flocculation, forming large flocs for easy separation

(C) Selection Based on PAC Product Specifications

1. By Al ₂O₃ Contents

Industrial grade PAC: 18%–26% Al ₂O₃, suitable for general industrial wastewater sludge treatment

High-content PAC: ≥28% Al ₂O₃, For applications requiring superior performance

2. In forma physica

Solid PAC: Easy to transport and store; Requires dissolution before use; 2%–20%

Liquid PAC: Convenient to use but higher transportation costs

3. By Basicity

Basicity is a key indicator of PAC's polymerization degree. Altior basicity means higher polymerization degree and stronger charge neutralization and bridging capabilities. Select appropriate basicity based on sludge characteristics.

(D) Optimization of Dosing Parameters

1. Dosage

Dosage PAC non habet standard fixatus et per testa determinabitur. General reference range: 1%–3% of sludge solid weight. Studies indicate optimal PAC conditioning parameters: dosage 25 mL (6% concentration), pH 7 (unadjusted), rapid mixing speed 130 rpm. Jar tests are recommended to determine optimal dosage.

2. Preparation Concentration

Conditionibus aluminiorum 4%-5% concentratio optima est.

3. Sequence Dosing

When combining inorganic and organic conditioners, add inorganic conditioner (PAC) first, then organic conditioner (PAM)

Addens PAC primum neutralizet cargas particularum et destabilizet systemam colloidalem, creans conditiones favoritas subsequentibus PAM bridging flocculationis

4. Conditiones Mixing

Appropriate mixing parameters are crucial for conditioning effectiveness. Studies show optimal PAC conditioning with rapid mixing at 130 rpm and slow mixing at 50 rpm. For combined use, two-stage mixing can be used: first stage at 500 r/min (0.5 min), second stage at 150 r/min (10 min).

5. Tempus conditioni

missus est piger destructus ad vasa inundationis cito longer holding times reduce conditioning effectiveness.

5. Processus seleccionis recommendatus

Step 1: Characterizatio Sludge

Determine sludge moisture content, pH, organic content, specific resistance to filtration, and other basic parameters

Understand sludge source and treatment process

Step 2: Teste laboratorii

Conduct jar tests with different PAC specifications

Determine optimum product type, dosage, and reaction conditions

Step 3: Testa Pilota

Conduct on-site pilot testing based on laboratory results

Verify dewatering performance, treatment costs, and operational feasibility

Step 4: Finalize Program

Determine final selection program based on pilot test results

Develop operating procedures and contingency plans

6. Key Precautions

avoid overMixing: When flocks are formed after mixing sludge with conditioners, avoid powerful re-mixing as broken flocks cannot be easily restored.

Temperatura Considerations: Low temperatures slow inorganic conditioner hydrolysis; Efficientia sub 10°C diminuit, requirens extendentem temporem conditioningam.

Corrosion Protection: Although PAC is less corrosive than iron salts, appropriate corrosion protection measures should still be implemented for equipment and piping.

Monitorium et iustificationem regularum: Characteristica nupticae cum seasonalis et aquae qualitate mutantur. Regular monitoring and timely dosage adjustments are recommended.

7. Conclusion

Polyaluminium chloridum, quasi maxime efficatus et costis polymeros coagulante inorganicus, significantis advantages offeret in dewatering treatment. Selectione propria et rationala dosing sunt clave ad maximizare performance PAC. Henan SECCO Environmental Protection Technology Co., Ltd., with years of R&D. D and production experience in water treatment chemicals, provides high-quality PAC products and professional technical support to customers.

For more product information or selection assistance, please contact Henan SECCO Environmental Protection Technology Co., Ltd.