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.