ABSTRACT
Chemical addition at water treatment facilities is performed mainly for the purpose of removing suspended particulate matter from the water. These suspended particles, colloids, are not heavy enough to be settled out and remain stable in suspension unless chemical coagulants are added. Chemical coagulation and flocculation are complicated processes, not always easy to optimize, and even more troublesome if the influent water quality is changeable. Effectiveness depends upon type and amount of coagulant, type, length, and completeness of mixing and flocculation, temperature, pH, alkalinity of the water, other chemicals present, etc.
