Which parameter is commonly measured to assess the buffering capacity of water?

• A. pH is commonly measured to assess buffering capacity.
• B. Chlorine residual is used to assess buffering capacity.
• C. Alkalinity is commonly measured to assess the buffering capacity of water.
• D. CBOD is used to assess buffering capacity.

Answer: (C)

Buffering capacity is a water system’s ability to resist changes in pH when acids or bases are added. Alkalinity directly measures that capacity because it reflects the amount of carbonate and bicarbonate (and some hydroxide) ions that can neutralize added hydrogen ions. This is typically determined by titrating a water sample with a strong acid and reporting the result as mg/L as CaCO3, which represents the potential acid-neutralizing capacity. pH tells you the current acidity or basicity but not how much acid the water can absorb before its pH shifts significantly. Chlorine residual and CBOD relate to disinfection and organic matter, not buffering. So alkalinity is the parameter that best indicates buffering capacity.