What is PAC?
Poly Aluminium Chloride (PAC) is a high-performance inorganic polymer coagulant widely used in water and wastewater treatment. Compared with traditional coagulants like aluminum sulfate and ferric chloride, PAC offers faster floc formation, larger floc size, lower dosage requirements, and wider pH tolerance. It is available in both liquid and powder forms, with varying Al₂O₃ content and basicity levels to suit different applications.
PAC Grades and Specifications
| Grade | Al₂O₃ Content | Basicity | Form | Primary Application |
|---|---|---|---|---|
| Drinking Water Grade | 30% minimum | 40-60% | Spray dry powder | Potable water, food & beverage, pharmaceutical |
| Industrial Grade (Standard) | 28-30% | 40-90% | Spray / drum dry powder | Municipal wastewater, industrial effluent |
| Industrial Grade (Liquid) | 10%, 17%, 18% | 40-90% | Liquid solution | Large-scale municipal, easy dosing |
| High Basicity PAC | 28-30% | 70-90% | Powder or liquid | Low-temperature water, high turbidity |
| Low Heavy Metal Grade | 30% | 45-65% | Spray dry powder | Drinking water, strict discharge standards |
How to Choose the Right PAC Grade
1. Define Your Application
The first step in selecting PAC is identifying your specific application, as this determines the required grade and quality standards:
- Drinking water treatment: Use drinking water grade with low heavy metals (As, Pb, Cd, Hg). Must meet NSF, WHO, or national drinking water standards.
- Municipal wastewater: Industrial grade 28% Al₂O₃ is usually sufficient. Choose based on inlet water quality and discharge limits.
- Industrial wastewater: Match the grade to effluent characteristics. High-COD or high-color water may need higher basicity or combined use with PFS.
- Process water (paper, textile, mining): Industrial grade is standard, but verify compatibility with process chemistry.
2. Consider Water Quality Parameters
PAC performance varies with raw water characteristics. Key factors include:
| Parameter | Effect on PAC Performance | Recommendation |
|---|---|---|
| pH | PAC works best at pH 5.0-9.0; optimal is 6.5-7.5 | Adjust pH before dosing if outside range |
| Turbidity | Higher turbidity generally improves coagulation | Very low turbidity may need coagulant aid (PAM) |
| Temperature | Low temperature reduces floc formation speed | Use high-basicity PAC; increase dosage 20-30% |
| Alkalinity | Insufficient alkalinity reduces coagulation efficiency | Add lime or soda ash if alkalinity <50 mg/L |
| Organic matter (COD/BOD) | High organic load increases PAC demand | Consider PAC+PFS blend or biological pretreatment |
| Color | Dissolved color compounds are harder to remove | Higher dosage; consider decolorizing agent as supplement |
3. Select the Right Basicity
Basicity (also called alkalization degree) is the percentage of hydroxyl groups relative to total aluminum. It is one of the most important quality parameters for PAC:
- Low basicity (40-50%): Strong charge neutralization, better for low-turbidity and low-temperature water. Slightly higher dosage required.
- Medium basicity (50-70%): Balanced performance for most applications. The most commonly used grade.
- High basicity (70-90%): Larger flocs, faster settling, lower sludge volume. Better for high-turbidity water and low-temperature conditions.
As a general rule, higher basicity PAC produces larger, denser flocs that settle faster, while lower basicity PAC provides stronger charge neutralization for finer particles.
4. Choose the Right Form: Powder vs Liquid
| Factor | Powder PAC | Liquid PAC |
|---|---|---|
| Al₂O₃ content | 28-30% (high concentration) | 10-18% (lower concentration) |
| Shipping cost | Lower (higher value density) | Higher (mostly water weight) |
| Storage | Dry storage, 24-month shelf life | Tank storage, 6-12 month shelf life |
| Dosing | Requires dissolution tank | Direct dosing, easier automation |
| Handling | Dust generation possible | Cleaner, less dust |
| Best for | Long-distance transport, on-site mixing | Nearby production, large volume use |
For most buyers importing from China, spray-dry powder PAC is the most cost-effective choice due to lower freight costs per unit of active ingredient.
Step-by-Step Selection Process
- Analyze your water: Test pH, turbidity, COD, color, alkalinity, and temperature.
- Determine treatment targets: Define required effluent standards (turbidity, COD, color, heavy metals).
- Conduct jar tests: Test 2-3 PAC grades with your actual water to find the optimal product and dosage.
- Verify certifications: For drinking water, ensure the product meets relevant standards (NSF/ANSI 60, GB 15892, etc.).
- Request samples: Get 500g-1kg samples from 2-3 suppliers for comparative testing.
- Calculate total cost: Include product cost, shipping, storage, and dosage efficiency (not just per-MT price).
- Pilot test: For large systems, run a 1-4 week pilot before full-scale commitment.
Dosage Guidelines by Application
| Application | Typical PAC Dosage (mg/L) | Notes |
|---|---|---|
| Drinking water (surface water) | 5 – 30 | Use drinking water grade; depends on turbidity |
| Drinking water (low turbidity) | 10 – 40 | May need PAM as coagulant aid |
| Municipal wastewater (primary) | 30 – 100 | Enhanced primary treatment |
| Municipal wastewater (tertiary) | 10 – 50 | Phosphorus removal and polishing |
| Industrial wastewater (general) | 50 – 200 | Varies widely by industry |
| Textile dyeing wastewater | 100 – 300 | Often combined with PFS and decolorant |
| Paper mill wastewater | 50 – 150 | Primary clarification |
| Mining wastewater | 30 – 200 | SS and heavy metal removal |
| Laundry / car wash | 30 – 100 | Oil, grease, and turbidity removal |
Note: Dosages are general guidelines. Always conduct jar tests with your specific water to determine optimal dosage.
Common Mistakes to Avoid
- Choosing based only on price: Cheaper PAC with lower Al₂O₃ content may cost more per kg of active ingredient.
- Ignoring basicity: Basicity significantly affects performance; match it to your water conditions.
- Skipping jar tests: Water composition varies widely; always test before committing to large orders.
- Over-dosing: Excessive PAC can cause restabilization of particles and increase sludge volume.
- Under-dosing: Insufficient PAC leads to poor floc formation and inadequate treatment.
- Ignoring pH: PAC performance drops sharply outside the optimal pH range of 6.5-7.5.
- Poor storage: PAC absorbs moisture; keep powder in sealed bags in dry storage.
PAC vs Other Coagulants
| Coagulant | Dosage | Sludge Volume | pH Range | Cost |
|---|---|---|---|---|
| PAC | Low | Low | 5.0-9.0 | Medium |
| Aluminum Sulfate (Alum) | High | High | 5.5-7.5 | Low |
| Poly Ferric Sulfate (PFS) | Low-Medium | Medium | 4.0-11.0 | Low-Medium |
| Ferric Chloride | Medium | Medium | 4.0-7.0 | Medium |
In many cases, combining PAC with PFS or adding a small amount of anionic PAM as a flocculant aid produces better results than using any single product alone.
Quality Verification Checklist
Before finalizing a PAC supplier, verify:
- Al₂O₃ content (third-party lab test report)
- Basicity level (matches your required specification)
- Water insoluble content (<0.5% for good quality)
- Heavy metal limits (As, Pb, Cd, Hg, Cr — especially for drinking water grade)
- ISO 9001 certification
- COA (Certificate of Analysis) for each batch
- Production capacity and lead time
- Packaging options (25kg bags, 1MT jumbo bags, etc.)
Conclusion
Selecting the right PAC grade requires matching product specifications to your specific water quality and treatment objectives. Start with jar testing, compare multiple suppliers, and consider total cost of ownership rather than just per-ton price. For most water treatment applications, a medium-basicity (50-70%) industrial grade PAC with 28-30% Al₂O₃ provides the best balance of performance and cost-effectiveness.
Need help selecting the right PAC for your application? Contact our technical team for a free water analysis and personalized recommendation.