Which Grade of PAC Should Be Chosen for Tap Water Purification?

Polyaluminum chloride (PAC) serves as a highly efficient water purifying agent, playing a crucial role in the purification process of tap water. Its excellent coagulation, precipitation, and bactericidal properties make it indispensable in water treatment plants. This article delves into the selection of polyaluminum chloride content and its impact on tap water purification in two parts.

Selection of Polyaluminum Chloride Content

The content of polyaluminum chloride, especially the content of aluminum oxide (Al₂O₃), is a vital indicator for measuring its water purification effectiveness. According to the national standard GB/T 15892-2020, the content of national standard PAC should not be less than 30.0%, with the Al₂O₃ content not less than 29.0%. This standard ensures that PAC has sufficient active ingredients to meet the needs of tap water purification.

In practical applications, water treatment plants often select polyaluminum chloride with appropriate content based on the raw water quality and treatment goals. For tap water with clearer water quality, PAC with a high content, specifically an Al₂O₃ content of at least 28% or higher, is recommended to ensure optimal treatment results. For tap water treatment with special requirements, such as drinking water purification, PAC with an even higher content, like food-grade PAC with an Al₂O₃ content typically exceeding 30%, may be chosen. Such products not only exhibit superior water purification efficiency but also contain virtually no impurities harmful to humans, ensuring water safety.

Furthermore, the content of PAC is also related to its production process and raw materials. PAC produced using high-quality aluminum hydroxide powder as raw material and advanced production techniques (such as plate-and-frame filter press type or spray drying type) typically has superior content and water purification effects.

Part II: Impact of Polyaluminum Chloride on Tap Water Purification

PAC plays multiple roles in the purification process of tap water. Firstly, it exhibits excellent coagulation properties, enabling the aggregation of suspended matter, particles, and other impurities in water into larger clusters, facilitating subsequent precipitation or filtration treatment. This role effectively removes turbidity from water, enhancing its transparency and clarity.

Secondly, PAC can effectively remove colloidal substances from water, including organic and inorganic colloids. These colloidal substances are often difficult to remove through traditional filtration methods, whereas PAC can coagulate them into larger particles for effective removal. This role helps reduce the organic matter content in water, enhancing its safety.

Additionally, PAC possesses certain bactericidal properties. It can disrupt the cellular structure of bacteria, viruses, and other microorganisms, thereby lowering their concentration in water. This role is crucial for ensuring that water quality meets hygiene standards.

It is worth noting that although polyaluminum chloride has numerous advantages in tap water purification, excessive use may also negatively impact water quality. Therefore, it is essential to strictly control the dosage during use and adjust it based on actual conditions. Simultaneously, regular monitoring of water quality indicators is necessary to ensure that treated water meets relevant standards and requirements.

In summary, the selection of PAC content has a significant impact on tap water purification effectiveness. Water treatment plants should choose appropriate PAC products based on raw water quality and treatment goals, strictly control their dosage and usage conditions, and ensure the safety and stability of water quality.