Pre-chlorination is the process of adding chlorine to the raw water
after screening and before flash mixing. The residual chlorine is useful
in several stages of the treatment process—aiding in coagulation, controlling
algae problems in basins, reducing odor problems, and controllingmud
ball formation. In addition, chlorine has amuch longer contact
time when added at the beginning of the treatment process, so prechlorination
increases safety in disinfecting heavily contaminated
water