At which pH range does alum work best?

Alum, or aluminum sulfate, is commonly used as a coagulant in water treatment processes. Its effectiveness is highly influenced by the pH of the water being treated. The optimal pH range for alum to function effectively is typically between 5.8 and 7.5. Within this range, alum dissociates properly to release aluminum ions, which are essential for forming stable flocs that can effectively capture and remove suspended particles from the water.

At pH levels lower than 5.8, the solubility of aluminum can reduce its efficacy as a coagulant, while at higher pH levels, above 7.5, the aluminum ions may precipitate out of solution rather than forming the necessary floc. Therefore, maintaining water within the 5.8 to 7.5 pH range is crucial for optimal coagulation, making this the best choice for alum's effective operation in treatment processes.