Polyaluminium chloride (PAC, CAS 1327-41-9) is an inorganic polymer coagulant widely used in water treatment for drinking water clarification, municipal wastewater treatment, and industrial effluent purification. Compared to conventional coagulants such as aluminum sulfate or ferric chloride, PAC offers higher charge density and faster floc formation across a wide pH range (5–9).
Flocculation Performance at Low Temperatures
During winter conditions (5–10°C), conventional coagulants often show reduced flocculation efficiency. The performance of PAC at low temperatures can be assessed using the following parameters:
Aluminum oxide (Al₂O₃) content: 28–30% (typical drinking water grade)
Basicity: 45–70% (affects floc formation rate and residual aluminum levels)
pH application range: 5–9 (recommend 6.5–7.5 at low temperatures)
Floc formation time: 2–5 minutes (at 20°C); 4–6 minutes at 5°C
Effluent turbidity after sedimentation: ≤1 NTU (with raw water turbidity 50–100 NTU)
Operational Parameter Recommendations
For low-temperature, low-turbidity water sources (water temperature ≤10°C, turbidity ≤20 NTU), the following operating ranges are recommended:
Parameter Recommended Range
Dosage 5–20 mg/L (adjust based on raw water turbidity)
Mixing velocity (G value) 300–500 s⁻¹ (rapid mixing, 10–30 seconds)
Flocculation velocity (G value) 30–70 s⁻¹ (slow stirring, 10–15 minutes)
Sedimentation time ≥30 minutes
For residual aluminum control, at dosages ≤20 mg/L, total aluminum residual in settled effluent can be maintained at ≤0.2 mg/L, meeting drinking water standards. If raw water pH is below 6.5, pre-dosing of alkali (e.g., sodium hydroxide or lime slurry) to adjust to 6.8–7.2 is recommended for optimal flocculation.
Product Specifications and Storage
PAC is available in the following forms:
Form Specification Packaging
Solid powder Al₂O₃ 28–30%, basicity 45–70% 25kg bag with PE liner; 1000kg jumbo bag
Liquid Al₂O₃ 10–12%, density ≥1.2 g/cm³ (20°C) IBC tote (1000L), liquid bag (1500kg)
For storage, keep in a dry area away from strong alkalis. Solid products remain stable for 12 months when stored at relative humidity ≤70%. Liquid products are recommended for use within 6 months, with storage temperature maintained above 0°C to prevent crystallization.
Market Observations
In recent years, water treatment plants and industrial water treatment facilities have focused on the following aspects of PAC: stability of flocculation efficiency under low-temperature conditions, compliance with residual aluminum limits (Chinese national standard GB 15892-2020 requires ≤0.2 mg/L), and the suitability of different basicity grades for specific water qualities. Suppliers should provide a Certificate of Analysis (COA) per batch, including test items such as Al₂O₃ content, basicity, pH (1% solution, 3.5–5.0), and heavy metal content (arsenic ≤0.0002%, lead ≤0.001%).
