Which of the following statements about prechlorination is true?

Prepare for the American Water Works Water Treatment Plant Operator Test. Study with multiple choice questions, each with hints and explanations. Get ready to excel!

Prechlorination means adding chlorine to raw water at the plant’s headworks before any filtration. The idea is to establish a disinfectant residual early in the treatment process, which helps suppress microbial growth and pathogens as the water moves through the system. It also helps control taste and odor compounds and aquatic growth, such as algae, that can develop in the source water or in intake structures. In addition, a small amount of chlorine can aid coagulation and flocculation by oxidizing certain natural organic matter, making it easier to remove during treatment. That combination—disinfection, odor/taste control, algae growth suppression, and aiding coagulation—matches the statement about prechlorination, which is why it is the correct choice. It’s not correct to say it’s used after filtration or that it exists only to affect taste and odor, and it is indeed used in water treatment.