HAA5 and TTHM are examples of which drinking water concern?

• A. Disinfection by-products
• B. Chlorine residuals
• C. pH indicators
• D. Turbidity measures

Answer: (A)

HAA5 and TTHM are disinfection by-products formed when chlorine-based disinfectants react with natural organic matter in the water. These compounds are monitored because they indicate DBP formation during disinfection, which has health implications if levels are too high. HAA5 refers to five haloacetic acids, while TTHM stands for total trihalomethanes (including compounds like chloroform). They’re not chlorine residuals, pH indicators, or turbidity measures—those are different aspects of water quality. The concept here is that disinfection can create secondary chemicals, and HAA5 and TTHM are typical examples of those by-products; utilities manage them by treating source water to reduce organic matter and by optimizing disinfection practices to minimize DBP formation.