Alkalinity is defined as:

• A. Measure of dissolved oxygen
• B. Ability of water to buffer acids
• C. pH value
• D. Rate of photosynthesis

Answer: (B)

Alkalinity is the water's ability to neutralize acids, its buffering capacity. This buffering keeps pH from changing dramatically when acids are added or produced in the treatment process. In wastewater operations, alkalinity buffers the acidity formed during microbial processes like nitrification; if alkalinity is too low, the pH can drop and disrupt treatment efficiency. Alkalinity is typically reported as mg/L as CaCO3, reflecting how much acid the water can neutralize before a significant pH change occurs. The other options describe different concepts: dissolved oxygen measures oxygen content, pH is the current level of acidity or basicity, and rate of photosynthesis is not related to water’s buffering capacity.