Water Treatment Chemicals Selection Guide
Choosing the right water treatment chemicals is critical for both performance and cost-efficiency. This comprehensive guide helps you select the optimal coagulant, flocculant, and specialty chemical for your specific application.
1. Coagulant Selection Guide
Coagulants Comparison Table
| Property | PAC (Polyaluminium Chloride) | Aluminum Sulfate (Alum) | PFS (Polyferric Sulfate) | PAFC (Polyaluminium Ferric Chloride) |
|---|---|---|---|---|
| Al₂O₃ / Fe₂O₃ Content | 28-30% Al₂O₃ | 14-16% Al₂O₃ | 18-22% Fe³⁺ | 27-29% Al₂O₃ + 1-3% Fe |
| Effective pH Range | 5.0-9.0 | 6.5-8.0 | 6.0-9.0 | 5.5-9.0 |
| Cold Water Performance | Good | Poor | Moderate | Good |
| Floc Formation Speed | Fast | Slow | Very Fast | Fast |
| Floc Density | Medium | Light | Dense | Medium-Dense |
| Sludge Volume | Low | High | Medium | Low |
| Color Removal | Good | Fair | Excellent | Good |
| Phosphorus Removal | Moderate | Low | Excellent | Good |
| COD Removal | Moderate | Low | Good | Good |
| Residual Metal Risk | Low | Moderate | High (iron color) | Low |
| Corrosivity | Low | Moderate | High | Low-Moderate |
| Cost per Treated Volume | $-$$ | $$ | $-$$ | $-$$ |
| Best Applications | General purpose, drinking water, industrial wastewater | Budget-sensitive, warm climate | High-color, high-phosphorus, industrial | Wide-range applications needing both Al & Fe |
Quick Coagulant Selection by Application
| Application | Recommended Coagulant | Typical Dosage (mg/L) | Notes |
|---|---|---|---|
| Drinking Water | PAC (drinking water grade, basicity 60-75%) | 10-30 | NSF/ANSI 60 certified |
| Municipal Wastewater | PAC + PAM combination | 30-100 PAC + 1-3 PAM | TCost-effective for large volumes |
| Industrial Wastewater (General) | PAC (industrial grade, basicity 70-85%) | 50-200 | Higher basicity for better performance |
| Textile/Dyeing Wastewater | PAC + Cationic PAM | 200-500 PAC + 2-5 CPAM | Pre-treat with COD remover for high COD |
| Paper Making Wastewater | PAC or PAFC | 100-300 | PAFC offers better color removal |
| Mining Wastewater | PFS + Anionic PAM | 100-500 PFS + 1-3 APAM | PFS handles heavy metals well |
| Oil & Gas Produced Water | PAC + CPAM + PAC | 100-300 + 2-5 | May need demulsifier pre-treatment |
| Food Processing Wastewater | PAC (drinking water grade) | 50-150 | Iron-free to avoid color issues |
| Swimming Pool | PAC or Aluminum Sulfate | 5-15 | Alum preferred for budget pools |
2. Polyacrylamide (PAM) Flocculant Selection Guide
PAM Types Comparison
| Property | Anionic PAM (APAM) | Cationic PAM (CPAM) | Nonionic PAM (NPAM) |
|---|---|---|---|
| Ionic Charge | Negative (-) | Positive (+) | Neutral (0) |
| Molecular Weight Range | 8-25 million | 5-15 million | 5-15 million |
| Optimal pH Range | 7-14 (alkaline) | 4-8 (acidic to neutral) | 4-9 (wide range) |
| Best Paired With | PAC, PFS, PAFC | PAC, PAFC | PAC, PFS |
| Typical Dosage | 1-5 mg/L | 2-5 mg/L | 1-5 mg/L |
| Best For | Mining, mineral processing, alkaline industrial wastewater | Sludge dewatering, organic-rich wastewater, municipal sewage | Acidic wastewater, special industrial processes |
| Water Solubility | Good | Moderate (needs longer mixing) | Good |
| Cost | $ | $$ | $ |
PAM Selection Decision Flow
- Determine wastewater pH: Alkaline → APAM; Acidic → CPAM or NPAM; Neutral → Test all three
- Analyze suspended solids charge: Negative charge (most common) → CPAM; Positive charge → APAM
- Identify primary goal: Sludge dewatering → CPAM; Clarification → APAM or NPAM
- Run jar tests: Test 2-3 types at 1, 2, 3, 5 mg/L each
- Optimize: Select type and dosage giving clearest supernatant and fastest settling
3. Activated Carbon Selection Guide
| Property | Coconut Shell Activated Carbon | Coal-Based Activated Carbon | Powdered Activated Carbon (PAC) |
|---|---|---|---|
| Iodine Number (mg/g) | 900-1200 | 800-1000 | 700-1000 |
| Surface Area (m²/g) | 1000-1300 | 800-1100 | 700-1200 |
| Hardness (%) | ≥98 | ≥95 | N/A (powder) |
| Ash Content (%) | ≤3 | ≤10 | ≤5 |
| Best For | Drinking water, food & beverage, pharmaceutical | Industrial wastewater, municipal water | Emergency treatment, seasonal applications |
| Regeneration | Multiple cycles | Multiple cycles | Single use |
| Cost | $$ | $ | $-$$ |
4. Filter Media Selection Guide
| Filter Media | Effective Size (mm) | Primary Function | Typical Filter Depth | Replacement Cycle |
|---|---|---|---|---|
| Quartz Sand | 0.4-1.2 | Turbidity removal, general filtration | 400-700mm | 3-5 years |
| Anthracite | 0.8-2.0 | Organics removal, dual-media top layer | 300-500mm | 5-8 years |
| Manganese Sand | 0.6-2.0 | Iron & manganese removal | 800-1200mm | 5-10 years |
| Activated Carbon | 0.5-2.0 | Organics, chlorine, taste & odor | 500-1500mm | 1-3 years |
5. Specialty Chemicals Selection
| Problem | Recommended Product | Typical Dosage | Expected Performance |
|---|---|---|---|
| High COD | COD Remover | 100-1000 mg/L | 60-85% COD reduction |
| High Ammonia Nitrogen | Ammonia Nitrogen Remover | 50-500 mg/L | 70-95% NH₃-N removal |
| Heavy Metal Contamination | Heavy Metal Capture Agent (DTC type) | 10-100 mg/L per mg/L metal | Cu, Ni, Zn, Cr, Pb to below 0.5 mg/L |
| High Phosphorus | Phosphorus Removal Agent (Fe/Al salt) | 50-300 mg/L | Total P to below 0.5 mg/L |
Need Help Selecting?
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