What do the routine monitoring requirements of the Stage 1 DBPR include?

• A. Carbon tetrachloride
• B. Chromium (total)
• C. TTHM/HAA5 and chlorite
• D. Elemental copper and lead

Answer: (C)

Disinfection by-products are the focus of Stage 1 DBPR monitoring because they form when disinfectants like chlorine or chloramines react with natural organic matter in the water. The major by-products tracked routinely are the total trihalomethanes (TTHMs) and the five haloacetic acids (HAA5). These two groups are monitored because they’re the most commonly formed and pose potential health concerns at typical drinking water levels. Chlorite is added to the monitoring when chlorine dioxide is used as the disinfectant, since chlorite is a by-product specific to chlorine dioxide processes. Together, monitoring for TTHMs, HAA5, and chlorite covers the main by-products produced by the common disinfection methods in distribution systems. The other substances listed—carbon tetrachloride, total chromium, and lead plus copper—are not part of the Stage 1 DBPR routine monitoring.