Module 3 · Treatment Steps

Coagulation

Coagulation is the first step in removing the particles that make water cloudy.

Key: = particles= coagulant chemical

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Many fine particles stay suspended in raw water and do not settle on their own. A coagulant is a chemical that helps those particles come together so the next steps can remove them. It must enter at the right point and mix quickly with the moving water. This fast mixing step is often called rapid mix. Too little coagulant leaves fine particles that never form floc, so the settled and filtered water stay cloudy. Too much can also leave cloudy water, waste chemical, and add to the sludge. Plants pick the dose with a jar test, which page 53 covers, not by the color of the water. Operators check source quality, chemical supply, pump condition, feed rate, and how the water responds downstream.