Degradation of Tertiary Alkylamines during Chlorination/Chloramination: Implications for Formation of Aldehydes, Nitriles, Halonitroalkanes, and Nitrosamines

Abstract

Drinking water utilities are exploring the use of waters impacted by wastewater effluents and agricultural runoff to meet the demands of growing populations. Due to the elevated organic nitrogen concentrations in these waters, the pathways responsible for transformation of organic nitrogen into toxic nitrogenous disinfection byproducts during chlorine and chloramine disinfection are of current concern. Tertiary alkylamines are important functional groups in human waste products and various consumer products that can be released to drinking water supplies via wastewater effluents. We investigated degradation pathways for model tertiary alkylamines during chlorination and chloramination. Our results indicate that tertiary alkylamines degrade nearly instantaneously during chlorination to form aldehydes and secondary alkylamines quantitatively, with no significant regioselectivity. Similar results were observed during chloramination, but the observed degradation rates were much slower, with lower yields of aldehydes. As these major products were fairly stable, these results explain why tertiary amines are significant precursors of secondary nitrosamines during chloramination. Trichloronitromethane formed at very low yields during chlorination, but was not observed during chloramination; monochloronitromethane and dichloronitromethane were never detected. Despite the significant yields of aldehydes during chloramination, our results indicated low nitrile yields bythe reaction between chloramines and aldehydes.