AWWA WQTC55168

According to data gathered by the Information Collection Rule, surface water treatment plants (SWTPs) can expect treated-water total haloacetic acid concentrations to be less than total trihalomethane (TTHM) concentrations. However, many SWTPs are plagued with distribution system haloacetic acid (HAA5) concentrations that are higher than TTHM concentrations. The 10 million gallons per day (MGD) Coldiron Watkins Memorial Water Treatment Plant in Danville, Kentucky, is one of these utilities. Distribution system HAA5 concentrations are up to two times higher than TTHM concentrations. To comply with the Disinfectant/Disinfection Byproduct Rule (DBPR), the Danville Water Treatment Plant (WTP), like many surface water utilities, has tried to reduce disinfection byproduct formation through enhanced coagulation and minimal chlorination. This technique has made only a small difference in TTHM and HAA5 concentrations. Because of lack of contact time at this facility, disinfection must be applied at the rapid mix to maintain adequate CT (concentration X time) credits. The current distribution system four-quarter running annual average (4QRAA) for TTHMs is 0.06 mg/L while the HAA5 4QRAA is 0.08 mg/L. Even though the annual average total organic carbon (TOC) removal ratio is 1.7, this utility will not comply with the Stage 1 DBPR total haloacetic acid maximum contaminant level (MCL) of 0.06 mg/L without additional treatment measures. Includes 13 references, tables, figures.