Control of Nitrosamines, THMs, and HAAs in Heavily Impacted Water With O3-BAC

Comprehensive control of regulated trihalomethanes (THMs) and haloacetic acids (HAAs), as well as nitrosamines, is needed to address forthcoming regulations. The formation potentials (FPs) of these disinfection by-products (DBPs) with chlorination (Cl-2) and chloramination (NH2Cl) were investigated along the treatment train of a conventional and ozone-biologically active carbon (O-3-BAC) process. The nitrosamines FP-NH2Cl, THM FP-Cl-2, and HAA FP-Cl-2 in heavily impacted source water in China were as high as 333 ng/L, 307 mu g/L, and 247 mu g/L, respectively, indicating that there was a high risk of DBP formation in the finished water. A combination of conventional and O-3-BAC processes reduced nitrosamine FP-NH2Cl to 39 ng/L, achieving an 88% removal. This process also reduced THM FP-Cl2 and HAA FP-Cl2 to 197 and 174 mu g/L, with fairly low removals of 36 and 29.5%, respectively. The strategy for this water was to apply conventional and O-3-BAC processes to substantially eliminate nitrosamine precursors and then apply chloramination to control THMs and HAAs.