What is the primary function of alum added to wastewater treatment?

Alum, or aluminum sulfate, is widely used in wastewater treatment primarily for its role in promoting flocculation. Flocculation is the process whereby fine particles in water clump together to form larger aggregates, known as flocs. This process is essential in the removal of suspended solids and other contaminants from wastewater.

When alum is added to wastewater, it dissociates into aluminum and sulfate ions. The aluminum ions react with the negatively charged particles, neutralizing their charges and allowing them to aggregate into larger flocs. This aggregation enables easier removal of these suspended particles during subsequent treatment processes, such as sedimentation and filtration.

By enhancing the flocculation process, alum helps to improve the overall effectiveness of wastewater treatment, leading to cleaner effluent and better compliance with environmental regulations. This makes it a vital substance in many treatment facilities.