4. Suspended colloidal solids are removed.

Colloidal solids consist of very small particles that are less than 2 microns in diameter, typically consisting of clay particles. To remove these tiny particles, water enters a holding tank where a coagulant/flocculant called Alum is added to the water to neutralize the charge of the particles.

• The alum also causes the suspended solids to bind to one another. A polymer is then added, increasing the weight and size of the particles. Sedimentation then causes these larger particles to settle to the bottom of the holding tank. The “settled sludge waste” is then pumped to a nearby sewage lagoon for treatment.