Predicting N-Nitrosamines: N-Nitrosodiethanolamine as a Significant Component of Total N-Nitrosamines in Recycled Wastewater

N -Nitrosamines are key contaminants of concern for wastewater reuse. Although research has focused on N -nitrosodimethylamine (NDMA), measurements indicate that NDMA accounts for only ∼9% of total N -nitrosamines in wastewaters, similar to previous findings in drinking and recreational waters. Recognizing the limited time scale for biological transformation during wastewater treatment, we targeted N -nitrosodiethanolamine (NDELA) as a component of total N -nitrosamines based upon the widespread usage of its triethanolamine precursor in consumer products. NDELA accounted for ∼6% of total N -nitrosamines, exceeding NDMA concentrations in some cases, and those of all other specific N -nitrosamines measured. While ozone and chloramines increased NDMA concentrations by up to an order of magnitude, and chloramines increased NDELA concentrations in some cases, other N -nitrosamine concentrations did not increase. Total N -nitrosamine concentrations increased by only 38–89% during ozonation and 23–65% during chloramination, suggesting that, in wastewaters, the occurrence of N -nitrosamines upstream of disinfection may be more significant than their formation as disinfection byproducts. In three advanced treatment trains, reverse osmosis and UV/hydrogen peroxide advanced oxidation reduced the levels of specific N -nitrosamines below their quantification limits, although 13–30 ng/L as NDMA of uncharacterized total N -nitrosamines remained.