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In wastewater treatment, Poly Aluminum Chloride (PAC) and Poly Ferric Sulfate (PFS) are top coagulants for purifying water and removing phosphorus. But how do you pick the right one? Let’s compare their strengths.
Basic features of PAC and PFS
| Speciality | Polyaluminium Chloride（PAC） | Polyferric Sulfate（PFS） |
| Chemical Type | Aluminum salt coagulants | Iron salt coagulants |
| pH application range | 5~8 | 4~11（More） |
| Main Application | Pretreatment coagulation, reduction of turbidity, removal of organic matter | Remove phosphorus, remove heavy metals, reduce turbidity and decolorization |
| Sedimentation Rate | Forming alum quickly, settling faster | The formation of floc is small, but the adsorption capacity is strong |
| Dosage | The dosage is small | Relatively large dosage |
| Influence on pH | Small impact, suitable for neutral water quality | Reduce pH value, suitable for more acidic wastewater |
| Treatment Effect | The removal effect of organic matter is better | It has better effect on phosphate removal |
pH Range: PFS Wins Flexibility
- PFS: Works at pH 4–11. Suitable for a wide range of wastewater treatment, such as acidic, alkaline and industrial wastewater.
- PAC: Best in pH 5–8, It is suitable for municipal sewage or water with relatively stable pH value.
Tip: Use PFS if your wastewater pH swings widely.
Phosphorus Removal: PFS Performs Better
Both bind phosphate (PO₄³⁻) into insoluble solids, but PFS edges ahead:
- PFS: The iron-phosphorus precipitates (FePO₄) produced by PFS are more stable and have a higher removal rate of over 90%.
- PFS: The colloid formed after hydrolysis of PFS has stronger adsorption capacity and can efficiently remove residual phosphorus in water.
- PAC: PAC is slightly less effective than PFS in phosphorus removal, but can be used in combination with polyacrylamide (PAM) to increase sedimentation rate.
Key Takeaway: For high-phosphorus wastewater (industrial, farming), choose PFS.
When to Choose Which?
✔️ Pick PFS If:
- Wastewater treatment requiring efficient phosphorus removal (e.g. industrial wastewater, aquaculture wastewater, etc).
- The pH value of wastewater fluctuates greatly, and coagulants with a wider pH adaptation range are needed.
- Allow pH to be reduced during the treatment process, or follow up with alkaline regulation measures.
✔️ Pick PAC If:
- Municipal wastewater treatment, drinking water purification or processes that require less impact on pH
- It needs to be combined with PAM to improve the coagulation sedimentation rate.
- Need to form alum more quickly, reduce sludge volume, improve effluent transparency.
Final Decision Guide
- Clear murky water? PAC is simpler.
- Target phosphorus? PFS delivers.
- Unpredictable pH? PFS adapts.
Different sewage treatment needs, need to choose the most suitable coagulant, reasonable combination of PAC or PFS, can improve treatment efficiency, reduce costs, improve effluent quality, and ultimately achieve efficient, environmental protection, economic sewage treatment goals.
