Which coagulant is commonly used in wastewater treatment?

Aluminum sulfate is a widely used coagulant in wastewater treatment due to its effectiveness in removing suspended solids and colloidal particles from water. When added to the wastewater, aluminum sulfate forms aluminum hydroxide through a hydrolysis reaction. This reaction produces a gelatinous precipitate that creates a larger mass with the suspended particles, which enhances the settling process during sedimentation.

The reason for aluminum sulfate's popularity stems from its ability to function effectively over a range of pH levels, making it versatile for different wastewater compositions. Additionally, it is relatively cost-effective and readily available, which makes it a practical choice for many municipal water treatment facilities.

In comparison, the other options, while they have their roles in various water treatment processes, do not serve as primary coagulants. Calcium carbonate is primarily used for pH adjustment and alkalinity, sodium hydroxide is also utilized for pH modification and removing specific contaminants but not as a coagulant, and iron chloride can function as a coagulant but is less frequently employed in certain treatment processes compared to aluminum sulfate. Thus, aluminum sulfate stands out as the most common coagulant in wastewater treatment applications.