The force is strong enough to hold the small, colloidal particles apart and keep them in suspension. As long as the zeta potential is stronger than the van der Waals force, then the particles will stay in suspension. The microfloc is still unsettleable. The gentle stirring action of the flocculation process brings the floc particles together to form large and relatively heavy floc particles, which can be easily settled and filtered. The jellylike floc particles are usually visible to the naked eye, and will look like small tufts of cotton or wool.
Coagulation involves the feeding and rapid mixing on one or more chemicals.
At Parleys Plant ferric chloride is used as our primary coagulant, and polymer is added to enhance the performance of the floc particle. These chemicals are added at the turbine of the flash mixer to allow rapid disbursement and mixing of the chemicals. The ferric chloride reacts with the natural alkalinity in the water to form the very small floc particle. Some of the discussion above includes excerpts from Introduction to Water Treatment-Principles and Practices of Water Supply Operations , by permission. Copyright 1984, American Water Works Association.