A single automated instrument for monitoring total trihalomethane and total haloacetic acid concentrations in near real-time

A single instrument is presented for selectively measuring the concentrations of total trihalomethanes (THM4) and total haloacetic acids (HAA9) directly from drinking water distribution systems. The method is based on the fluorescence reaction of THM4 or HAA5 species with nicotinamide. The method detection limit (MDL) for THM4 was 2.5 μg L−1 with mean % recovery of 108% and % relative standard deviation (% R.S.D.) of 4%. For HAA5, the MDL was 3.3 μg L−1 with mean % recovery and % R.S.D. of 102% and 3.5%, respectively. Side-by-side comparisons to United States Environmental Protection Agency methods (Methods 502.2 and 552.3) in chlorinated and chloraminated distribution systems exhibited reproducible biases that ranged from ∼0.2 to 5 μg L−1 for THM4 and from ∼−0.7 to −27 μg L−1 for HAA5. The device provides for automated on-line sampling and analysis of THM4 and HAA9 with hourly sample analysis rates and is effectively a real-time system for drinking water monitoring.