What Is The Difference Between PAC And ACH?

In the water treatment industry, coagulants are important chemicals. Although they overlap in appearance and application fields, they have their own characteristics in terms of chemical structure, performance, application scenarios and operating costs. This article will explain the differences between poly aluminum chloride (PAC) and aluminium chlorohydrate (ACH), providing more professional and clearer references for purchasers.

Coagulants play a crucial role in the treatment of industrial wastewater, drinking water, and municipal sewage, including:

• Remove suspended solids (SS)
• Reduce turbidity
• Reduce COD and color
• Enhance sedimentation and filtration efficiency

With the upgrading of environmental protection regulations and the continuous improvement of water treatment standards, enterprises' requirements for coagulants have shifted from "usable" to "efficient, safe, highly compatible and environmentally friendly". Therefore, as common coagulant chemicals in the market, the performance differences between poly aluminum chloride and aluminium chlorohydrate have also become one of the most concerned issues for purchasers.

Choosing the appropriate coagulant not only affects the water treatment effect, but also directly influences the amount of sludge, equipment load, chemical cost and overall operating cost. Next, let's take a look at the differences between PAC and ACH.

Poly aluminum chloride (PAC) is an inorganic high-molecular coagulant widely used in municipal sewage, industrial wastewater, drinking water and other fields. As a chemical with a high degree of polymerization, it has the following characteristics:

 

• Moderate range of aluminium content
• Moderate degree of polymerization
• The fast speed of forming flocs
• Good solubility and easy to add
• Moderate cost and high cost performance
• Adapt to most water qualities and working conditions

PAC forms positively charged polyaluminum ions through hydrolysis, which neutralize charges, make suspended solids unstable and promote the formation of flocs.

 

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Aluminium chlorohydrate (ACH) is a type of high-quality coagulant with a higher degree of polymerization. Its aluminum content is generally higher than that of PAC, and it has a lower impurity content, making the product purer. It is suitable for high-standard water treatment scenarios. Its features include:

 

• Higher aluminium content (especially solid ACH)
• The lower impurity content
• Form denser and more stable flocs
• A wider pH adaptability range
• More favored by industries such as drinking water, food, and medicine

 

ACH is often used in process systems where extremely high requirements are placed on water quality safety, residual aluminum content and filtration accuracy.

 

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• All belong to inorganic polymer flocculants
• All through charge neutralization and entrapment effects to flocculate
• All can remove turbidity, suspended solids, colloids and organic matter
• Widely applied in industrial, drinking water and municipal sewage treatment

Although they share many commonalities, the two still have significant differences in structure, performance and cost.

Both poly aluminum chloride and aluminium chlorohydrate are excellent coagulants, and their key differences are mainly reflected in the following aspects:

Products
Name	Poly Aluminum Chloride (PAC)	Aluminium Chlorohydrate (ACH)
Differences in aluminum content	PAC usually comes in yellow, light yellow, white or milky white powder, with an Al2O3 content of approximately 28% to 31%. Liquids have a short shelf life and need to be used as soon as possible.	ACH usually comes in two forms: liquid and solid. The Al2O3 content of ACH liquid is 23%, and that of ACH solid is 46-48%.
	The higher the aluminium content, the more effective components there are per unit mass of the product, and the more significant the treatment effect will be.
Differences in degree of polymerization	Although the degree of polymerization of PAC is moderate, it has strong compatibility with most water qualities.	ACH has a higher degree of polymerization, so the flocs formed are tighter and more stable.
pH adaptability	The applicable pH range of PAC is 5-9.	ACH has a wider range and can operate within a pH range of 4 to 10, making it more friendly to water bodies with high acidity and alkalinity.
Impurity content	The impurity content of PAC is slightly higher, but it can still meet most industrial and municipal demands.	ACH has the lowest impurity content and is suitable for the drinking water, food processing and pharmaceutical industries.
Floc characteristics	The flocs formed by PAC are large and settle faster, making it suitable for wastewater with high turbidity.	The flocs formed by ACH are more compact and have superior filtration performance, making them more suitable for advanced treatment processes.

Industrial wastewater treatment

Industrial wastewater is of complex quality, containing turbidity, color, metals and organic matter. Due to its strong adaptability and cost advantage, PAC is the preferred coagulant for most enterprises, which can quickly form large and easily settled flocs. ACH can also be used for industrial wastewater, but it is more expensive and is mostly used in working conditions where lower residual metal is required.

Municipal sewage treatment

Most municipal sewage treatment plants prefer to use PAC, which has a smaller dosage, a faster sedimentation speed, and a stronger ability to adapt to water quality fluctuations, which is conducive to reducing the overall operating cost. ACH, on the other hand, is often used in advanced treatment processes or projects where strict control over aluminum residue in the effluent is required.

Drinking water treatment

In the drinking water treatment, the advantages of ACH are even more obvious. Due to its lower impurity content and less residual aluminum, the formed flocs are more compact, making it more suitable for processes that require high-standard purification, such as bottled water and food processing water. PAC is suitable for treating raw water with significant variations in turbidity, especially demonstrating stable performance in large-scale water supply projects.

Pool clarification

In terms of pool clarification, PAC can rapidly improve water transparency over a wide pH range and can be used in hotel and home swimming pools. ACH is more commonly found in high-end swimming pools and professional places that require strict water quality control due to its lower chemical residue and more stable clarification effect.

High-standard industries (pharmaceuticals/cosmetics/food)

For these industries, the purity and safety of water quality are crucial. High-purity ACH coagulant is highly suitable for these water-using applications. Although PAC is also available in these fields, it is more often used in situations where cost is sensitive but there are still certain water quality requirements.

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Stability of the coagulation effect

The coagulation effect of PAC is stable under most water quality conditions. ACH performs better in systems with high processing accuracy requirements.

Usage comparison

Due to the higher aluminum content, the dosage of ACH is usually lower than that of PAC.

Sludge volume

ACH usually generates less sludge, which is conducive to reducing treatment costs.

Operating cost

Overall, PAC has a lower unit price and is suitable for customers with large processing volumes and diverse demands. ACH effluent stability is higher and it is suitable for high-standard industries. Different enterprises can select appropriate coagulants based on their budgets and processing goals.

As a coagulant supplier, we usually provide the following support based on customer requirements:

• Water quality analysis (COD, turbidity, pH, metal ions)
• On-site or lab-scale tests
• Dosing system and dosage recommendations
• Cost comparison between PAC and ACH
• Customized product/packaging services
• Stable supply guarantee

PAC and ACH have their own distinct technical features and application advantages. PAC is renowned for its high cost performance, strong adaptability and fast sedimentation speed, suitable for industrial wastewater, municipal sewage and large-scale water treatment projects. ACH, with its higher purity, lower residual aluminum, denser flocs and superior filtration performance, holds an advantage in drinking water and high-standard industries.

Whether enterprises are pursuing cost optimization, improved treatment efficiency, or stricter safety standards, the correct selection of coagulants can significantly reduce operating costs, enhance system stability, and ensure that water quality meets expected standards.

If you are choosing poly aluminum chloride or aluminium chlorohydrate for your project, please feel free to contact us for product selection suggestions. We will provide you with the most suitable coagulant solution based on your industry requirements, budget and performance goals, and ensure a stable and reliable supply chain support.