Water Treatment > Quality Water Solutions > PACl in Brief

The performance of PACl products varies with how they are manufactured. This basically involves dissolving aluminum, as either aluminum metal or aluminum hydroxide, in hydrochloric acid. Products will vary according to heat, time of reaction, raw materials, pressure and mixing intensity. Some processes produce a specific product, while others make an array of chemistries. Four qualities are often used describe them:

• Basicity concerns the amount of hydroxide present. Higher basicity products tend to have a higher positive charge and are more efficient in coagulating negatively charged contaminants. (Basicity in commercial PACls ranges from below 10% to above 80%.
• Aluminum content typically varies from 3% to 12.5% by weight.
• Additives are chemicals that enhance performance. Cationic polyelectrolytes, the most common additive, enhance performance at low feed levels. They broaden the effective dosage range, which can cut chemical residue by up to 90%.
• Polynuclear content, or the amount of highly aggregated forms of aluminum present, is analogous to molecular weight and charge density in organic polyelectrolytes. It can define reaction rate, turbidity/color destabilization and aluminum solubility. Monomeric aluminum is often preferred for highly colored waters and phosphorus removal.

PACl is most often sold on a neat, liquid, 100% or "as is" basis, terms that are synonymous. Purchasers should ask for typical analyses from suppliers showing percent aluminum, percent basicity, heavy metals, additives, specific gravity and the NSF or UL listings. They also should perform routine load analyses for product strength, basicity and additive content. In evaluating PACls, the only way to find the best product at the best overall cost is to evaluate how well each one functions in the plant environment.

Press here to receive the following information:

• Recommendations for the Storage and Handling of Polyaluminum Hydroxychloride Products, General Chemical Technical Service Report No. 1.90
• Clar+Ion® and Hyper+Ion® Enhanced Cationic Coagulants, General Chemical brochure
• AWWA Standard for Liquid Polyaluminum Chloride
• A Coagulant Road Map, Public Works