Estimation of haloacetonitriles formation in water: Uniform formation conditions versus formation potential tests

Abstract

To date, several studies have used formation potential (FP) tests to examine the presence of HAN precursors in water and wastewater. However, given the decomposition of HANs with time at elevated free chlorine levels, FP test results do not provide meaningful results. We conducted side-by-side FP and uniform formation condition (UFC) experiments to demonstrate that, in order to obtain practical, meaningful, and representative information about HANs formation and their precursors during chlorination, it is important to conduct experiments and report results under UFC [or simulated distribution system (SDS)] conditions.The results confirmed higher HAN formation under UFC than FP tests during chlorination of the tested two surface water and three wastewater effluent samples, indicating HAN decomposition at high chlorine conditions of FP tests. In addition, the well reported ratio (~10%) of HAN/THM from previous studies was more consistent with the UFC results but was lower than 10% in the FP results. On the other hand, HAN formation during chloramination of the same samples were lower under the UFC than FP conditions. Furthermore, FP tests under both chlorination and chloramination resulted in lower bromine substitution factor.We concluded that reporting results of HANs FP tests are not representative, and future studies should focus on UFC or distribution system specific (SDS) experiments for chlorination. However, chloramination FP tests may still provide some information about the HAN precursors in waters.