PAC vs. ACH: Which Coagulant is Best for Drinking Water Treatment?

Introduction

In municipal water treatment, coagulants are the unsung heroes—and often the single largest chemical expense. They aggregate colloidal impurities, clearing obstacles for sedimentation and filtration. While Polyaluminum Chloride (PAC) has dominated the market due to its economic advantages, Aluminum Chlorohydrate (ACH) is gaining traction despite a 20%-30% price premium.
For water plant operators and procurement managers, the question remains: Is ACH worth the extra cost?

Overview: PAC vs. ACH

1. Polyaluminum Chloride (PAC) – The Cost-Effective Standard

• Key Advantages: Mature production process, highly cost-effective, effective for a wide range of common water qualities.
• Ideal Scenarios: Municipal projects with strict budget controls, treating raw water with moderate turbidity and typical organic content.
• Key Specs: AL₂O₃ content (10%-30%), Basicity (40%-90%).

2. Aluminum Chlorohydrate (ACH) – The High-Performance Specialist

• Key Advantages: Highest aluminum content, excellent charge neutralization, minimal effect on pH, and superior performance in cold water.
• Ideal Scenarios: Low-temperature water, high color/organic matter (humic acid), and plants with strict residual aluminum limits.
• Key Specs: High AL₂O₃ content (>23% liquid, >46% powder), High Basicity (>80%). Contains the highest percentage of AL₂O₃ species (the most effective form for coagulation).

Parameter	PAC (Standard Grade)	ACH (Premium Grade)
Turbidity Removal	Good (Target 1 NTU at 18 mg/L)	Excellent (Target 0.5 NTU at 14 mg/L)
Organics Removal (UV254)	~65% removal	~82% removal
Sludge Production	Standard baseline	25% Less Sludge (Lower disposal costs)
pH Tolerance	6.0 – 9.0	5.5 – 8.5 (Little pH adjustment needed)
Reaction Speed	Moderate	Fast (Rapid floc formation)

How to Choose? A Global Case Study Approach

The choice between PAC and ACH isn’t about “better or worse,” but “fit for purpose.”

1. The Cold Water Challenge (Russia & Northern Europe Model)

• Challenge: Water temperatures <5°C slow down hydrolysis. Standard PAC reacts slowly, forming loose flocs.
• Why ACH Wins: ACH is pre-hydrolyzed. Its high basicity allows it to work efficiently even in near-freezing water.
• Case Study: A plant in Siberia switched to ACH, reducing effluent turbidity from 2.5 NTU to 0.8 NTU. Despite the higher unit price, total chemical costs remained flat due to a 25% reduction in dosage.

2. High Organics & Algae (Brazil & South Africa Model)

• Challenge: Tropical reservoirs often have high humic acid (TOC > 5 mg/L). Incomplete removal leads to Disinfection Byproducts (DBPs) like Trihalomethanes.
• Why ACH Wins: The high charge density of ACH neutralizes organic colloids more effectively than PAC.
• Case Study: A São Paulo plant reduced trihalomethane precursors by 52% after switching to ACH, meeting strict EU/WHO standards.

3. High Turbidity & Monsoon Waters (China & India Model)

• Challenge: River turbidity can spike >500 NTU during rainy seasons.
• Why PAC Wins: In high-turbidity scenarios, the sheer volume of suspended solids requires a “sweeping” effect. High-molecular-weight PAC forms large, heavy flocs quickly.
• Economic Benefit: For treating massive volumes of muddy water, PAC offers a significantly lower cost per ton ($/m³) while maintaining compliance.

4.Strict Residual Aluminum Limits (EU & Japan Model)

• Challenge: Regulations (e.g., EU 2020/2184) demand residual aluminum ≤0.1 mg/L.
• Why ACH Wins: ACH’s stable chemical structure minimizes the release of dissolved aluminum compared to lower-basicity PAC.
• Case Study: A Berlin utility reduced residual aluminum from 0.15 mg/L to 0.07 mg/L by upgrading to ACH, ensuring regulatory compliance.

Decision Tree: 4 Steps to Lock in the Best Solution

1. Temperature Check: Is water <10°C? → ACH Preferred.
2. Organics Check: Is TOC > 4 mg/L? → ACH Preferred.
3. Turbidity Check: Is Turbidity >200 NTU? → PAC Preferred (Cost advantage).
4. Compliance Check: Is Aluminum Limit ≤0.1 mg/L? → ACH Mandatory.

Conclusion & HOO CHEMTEC Solution

PAC remains the pragmatic king for standard municipal water treatment, offering unbeatable economy. However, for specialized challenges—cold climates, high organics, or strict environmental standards—ACH transforms its premium price into operational savings and peace of mind.

Why Partner with HOO CHEMTEC?
As a dedicated manufacturer and exporter, HOO CHEMTEC understands that chemicals are not “one size fits all.”

• Global Standard: We supply both Industrial and Drinking Water Grade PAC & ACH (NSF/ANSI 60 standard compliant).
• Customization: We can adjust Basicity and Alumina content to match your specific raw water profile.
• Logistics: Efficient export handling to ensure product stability upon arrival.

Contact us today for a free consultation based on your water quality report.