What is the purpose of a chlorine contact tank or chamber?

• A. To provide sufficient contact time for disinfection before water reaches consumers.
• B. To increase water temperature.
• C. To filter solids.
• D. To remove dissolved gases.

Answer: (A)

Chlorine contact tanks are built to give chlorine enough time to disinfect the water before it goes to consumers. When chlorine is added, it needs contact with the water for a period of time so it can inactivate germs like bacteria and viruses. The tank slows the flow and, often with baffles to mix the water gently, ensures all water parts get exposed to chlorine for that needed contact time. That way a residual level of chlorine can continue downstream to keep the water disinfected as it travels through the system. The other options aren’t the purpose of this tank: heating the water isn’t the goal, filtering solids is done by filtration units, and removing dissolved gases is handled by other processes such as degassing or aeration.