Which statement best describes how pH affects disinfection efficacy and corrosion propensity in water mains?

• A. Disinfection efficacy is independent of pH, and corrosion propensity is constant.
• B. Disinfectant effectiveness is pH-dependent, with free chlorine more effective at lower pH and high pH reducing disinfection; pH also influences corrosion.
• C. pH only affects taste and color, not disinfection or corrosion.
• D. Lower pH always increases corrosion, while higher pH always reduces it.

Answer: (B)