Last Updated: August 2026 | Reading Time: 12 minutes
Introduction
PAC vs PFS comparison—poly aluminium chloride versus poly ferric sulfate—examines two of the most widely used inorganic coagulants in modern water treatment. Both are pre-hydrolyzed coagulants offering superior performance to traditional alum and ferric chloride. PACs aluminum-based chemistry provides excellent turbidity removal across pH 5 to 9, low residual aluminum, and minimal pH depression. PFS (polymeric ferric sulfate) excels in phosphorus removal, heavy metal co-precipitation, and low-temperature water treatment, with higher floc density and faster settling. PAC generates less chemical sludge and is less corrosive, while PFS demonstrates superior performance on high-organic-content wastewater. The PAC vs PFS comparison requires evaluating target contaminants, water temperature, pH, sludge disposal costs, and equipment compatibility. This detailed guide provides comparative performance data, molecular structure analysis, application recommendations, and economic evaluation to optimize coagulant selection.
Head-to-Head Comparison
| Parameter | Option A | Option B |
|---|---|---|
| Active Ingredient | Aluminum | Iron |
| Optimal pH | 5.5-8.0 | 4.5-8.0 |
| COD Removal | 30-55% | 40-60% |
| Sludge Volume | Low | Medium |
| Cost | Medium | Medium-High |
Decision Guide
- PAC: Balanced, lower sludge, minimal pH change
- PFS: Higher COD removal, faster settling
- Alum: Lower cost, moderate performance
Chemical Dosing Guide
| Stage | Chemical | Dosage | pH | Efficiency |
|---|---|---|---|---|
| Coagulation | PAC 30% | 50-300 mg/L | 5.5-8.0 | 30-55% COD |
| Coagulation | PFS | 30-200 mg/L | 4.5-8.0 | 40-60% COD |
| Flocculation | PAM | 0.5-5 mg/L | 6-9 | Improves settling |
| Adsorption | Carbon | 50-500 mg/L | 5-9 | 20-80% COD |
Cost Analysis
| Method | Capital | Operating | Best For |
|---|---|---|---|
| Coagulation | $50-150 | $0.10-0.30 | Suspended solids |
| Biological | $100-250 | $0.05-0.20 | Biodegradable COD |
| Fenton AOP | $80-200 | $0.30-1.00 | Refractory COD |
| Activated Carbon | $50-150 | $0.20-0.80 | Polishing |
FAQ
Main difference?
Differences in active ingredient, optimal pH range, removal efficiency, sludge production, and cost.
Which is more cost-effective?
Depends on water quality. PAC is balanced for most uses. PFS may be more cost-effective for higher COD removal.
Can I switch between options?
Yes, but requires jar testing for new dosages. Consider pH impact, sludge handling, equipment compatibility.
How to test which is best?
Conduct comparative jar test with different coagulants at varying dosages. Request free samples for testing.
Need Expert Help?
HydroChemix provides free technical consultation, jar testing support, and free samples. Our engineers help you select the right chemical and optimize treatment.
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