Formation of Nitrosodipropylamine from Nitrogenous Contaminants (Amines and Amine-Based Pesticides) in Water During Chloramination

Chloramination of drinking water and wastewater can generate carcinogenic nitrosamines, among which, nitrosodipropylamine (NDPA) with large molecular weight and weak polarity has been commonly found. However, knowledge on the formation of NDPA remains highly limited. Laboratory tests were conducted to quantify NDPA formation during chloramination of nitrogenous precursors, including dipropylamine and methyldipropylamine, and pesticides such as trifluralin, oryzalin, and vernolat. Results showed that all precursors exhibited > 10.0% NDPA yields after 24 h. Oryzalin and trifluralin accomplished the highest (13.63%) and lowest (11.31%) yield, respectively. Maximal yields of all precursors were observed at pH 9.0 and temperature 288 K. Maximums of NDPA yield from oryzalin (18.27%) and vernolat (19.54%) were formed at Cl:N of 0.7:1.0, but maximal yields of dipropylamine (18.44%), methyldipropylamine (22.98%), and trifluralin (33.06%) were achieved at Cl:N of 1.2:1.0. Maximal NDPA yields of dipropylamine (37.14%), methyldipropylamine (32.84%), and vernolat (49.02%) were observed at [NH 2 Cl] 0 :[precursor] 0 = 500, but highest yields of trifluralin (30.24%) and oryzalin (25.53%) were accomplished at [NH 2 Cl] 0 :[precursor] 0 = 50. Bromide and organic contents in tap and raw water reduced NDPA due to competition for NH 2 Cl. Chloramination of water impacted by amines and pesticides should be careful of NDPA formation.