What is coagulation in water treatment and why is it important?

• A. Coagulation adds a coagulant to destabilize particles, helping them clump and settle, removing turbidity and contaminants.
• B. Coagulation heats water to kill microbes.
• C. Coagulation uses ultraviolet light to disinfect water.
• D. Coagulation increases dissolved oxygen by aeration.

Answer: (A)

Coagulation is the step where a chemical coagulant with a positive charge is added to water to neutralize the negative charges on tiny suspended particles. When these charges are neutralized, the particles no longer repel each other as strongly, so they collide and stick together to form larger clumps called flocs. Gentle mixing helps these flocs grow bigger until they’re heavy enough to settle out in sedimentation basins or be removed by filtration. This reduces turbidity and helps remove contaminants attached to those particles, making disinfection more effective and improving overall water quality. Other processes like heating to kill microbes, using UV light for disinfection, or adding air to raise dissolved oxygen are different steps in water treatment and serve other purposes.