TOC removal requirements increase as alkalinity decreases. Which of the following best describes this relationship?

• A. Increases
• B. Decreases
• C. Remains the same
• D. Fluctuates

Answer: (A)

Lower alkalinity means less buffering of pH and less stability during coagulation and TOC removal steps. When alkalinity is reduced, adding coagulants or oxidants can cause greater pH shifts, which makes coagulation less efficient at destabilizing and removing natural organic matter. As a result, more TOC removal is required to achieve the same target. Conversely, higher alkalinity provides buffering that helps maintain effective coagulation, reducing TOC removal needs. The other options don’t fit because they imply no change, a decrease, or an unpredictable fluctuation, which doesn’t align with how alkalinity supports treatment processes and pH control.