Prechlorination at a wastewater facility helps suppress the growth of what type of organisms?

• A. Odor-producing bacteria
• B. Nitrifying bacteria
• C. Algae
• D. Pathogenic viruses

Answer: (A)

Prechlorination is used to oxidize reduced compounds and suppress odor-causing microbes early in treatment. Odor-producing bacteria, such as sulfate-reducing bacteria that generate hydrogen sulfide, are particularly affected by chlorine. By applying chlorine before downstream processes, these organisms are inhibited and odor emissions are reduced. Algae aren’t the primary concern in this context, viruses don’t “grow” in wastewater in the way living organisms do (chlorine inactivates them rather than suppressing growth), and nitrifying bacteria can also be affected by chlorine but that isn’t the purpose of prechlorination in this scenario.