Investigation of Ozone-Reactive Precursors That Form NDMA: A Potable Reuse Contaminant

Nitrosamine formation may be a significant barrier to ozonation in water reuse applications, particularly for direct or indirect potable reuse. Only a few studies have identified precursors for N-nitrosodimethylamine (NDMA) formation due to ozone. Model precursor compounds were added to ultrapure water and reclaimed water samples and spiked with excess ozone. Additional experiments were performed to evaluate the effects of the bromide ion, ozone dose, and addition of hydrogen peroxide, as well as compare NDMA formation due to chloramination and ozonation. Several model compounds resulted in NDMA formation upon ozonation. Bromide concentration enhanced NDMA formation for three compounds, but not all precursors. This suggests that different pathways may be involved in NDMA formation. Molar conversion yields were higher for several precursors in wastewater compared to deionized water and when hydroxyl radicals were scavenged. NDMA formation due to chloramination was minimal compared to formation due to ozonation for these precursors.