The proposed Disinfectants/Disinfection By-products (D/DBP) Rule estab
lishes a maximum contaminant level (MCL) for haloacetic acids (HAAs) o
f 60 mu g/L and revises the MCL for trihalomethanes (THMs) to 80 mu g/
L. In anticipation of the proposed rule, researchers obtained finished
drinking water from six North Carolina utilities and analyzed for THM
s, HAAs, and total organic halides. Samples from representative locati
ons within the distribution system were collected three times over 12
months to discern seasonal patterns in DBP formation. Relationships am
ong the different by-products were explored, as was their relationship
to raw water quality. The results suggest that HAA concentrations can
be as much as 50 percent greater than THM concentrations and that the
occurrence of HAAs in finished drinking water may be much higher than
was anticipated when the D/DBP Rule was proposed.