N-nitrosodimethylamine (NDMA) formation during ozonation of N,N-dimethylhydrazine compounds: Reaction kinetics, mechanisms, and implications for NDMA formation control

Abstract

Hydrazine, hydrazides, and hydrazones with N,N-dimethyl groups, which have been identified as potent NDMA precursors during ozonation, can be a concern for drinking water and wastewater utilities using ozonation. In this study, kinetics, mechanisms, and NDMA formation during ozonation and chlorination of selected N,N-dimethyl hydrazine compounds were investigated to optimize these oxidative water treatment processes for NDMA control. The reaction of ozone with the selected N,N-dimethyl hydrazine compounds was rapid and efficiently produced NDMA. The reaction of OH radicals with N,N-dimethyl hydrazine compounds did not produce NDMA. From the rapid reaction of N,N-dimethyl hydrazine with ozone, significant NDMA formation is expected to be unavoidable during ozonation of the waters containing these precursors. Pre-chorination can be used as an option to control NDMA formation in post-ozonation process from its fast and NDMA-free reaction with selected N,N-dimethyl hydrazine compounds.