What is the main purpose of carbon dioxide addition during recarbonation?

• A. To reduce the chlorine concentration
• B. To ensure effective disinfection
• C. To lower pH and stabilize treatment parameters
• D. To eliminate hardness

Answer: (C)

The main purpose of adding carbon dioxide during recarbonation is to lower pH and stabilize treatment parameters. When carbon dioxide is introduced into water, it reacts with the water to form carbonic acid, which decreases the pH of the water. This process is essential for controlling pH levels, particularly in water treatment systems where maintaining appropriate chemical balance is crucial for efficient operation and effectiveness of subsequent treatment processes.

By lowering the pH, carbon dioxide can help produce a more favorable environment for other treatment processes, such as coagulation and flocculation, where the efficiency of these processes is often pH-dependent. Moreover, stabilizing the pH is vital for preventing scaling in pipelines and treatment equipment, and it improves overall water quality by enhancing the solubility of certain minerals and chemicals that might otherwise precipitate out at higher pH levels.

Understanding this aspect of water treatment is essential for operators, as it plays a significant role in ensuring water quality while optimizing the treatment process.