title: Investigating Haloacetonitrile (Han) Formation Potential from Nitrogenous Antibiotics and Agrochemicals
Creators: name: Haider, Kazi Shafayet
Publisher: name: University of Nevada, Las Vegas
Year: 2023

description: Disinfection can promote safe drinking water. Chlorine and chloramines are the two most used disinfectants. While these disinfectants are effective in inactivating disease-causing pathogens, they also produce hazardous byproducts when they react with organic compounds (precursors). Nitrogenous disinfection byproducts (N-DBPs) are more toxic than their counterparts. The increased use of nitrogen-based agrochemicals and antibitics has led to their detection in different water sources. The presence of secondary amine and aniline in these compounds can act as a source of reactive nitrogen to form N-DBPs. In addition, the increased concentration of bromide in water systems due to anthropogenic activities can enhance the formation of extremely toxic Br-DBPs. In this study, nitrogenous agrochemicals with a secondary amine (atrazine, carbaryl, and simazine) and pharmaceuticals containing aniline (sulfanilamide, sulfisoxazole, and sulfacetamide) were investigated for the first time as precursors to generate disinfection byproducts, specifically trihalomethanes (THMs) and haloacetonitriles (HANs). The effect of elevated concentration of bromide was also studied.During the chlorination and chloramination of water containing the selected agrochemicals and pharmaceuticals, THMs and HANs were formed. HAAs were formed only through chloramination. Among different THMs, the formation of trichloromethane was highest for both disinfection processes. Among different HANs, the formation of dichloroacetonitrile was highest for both disinfection processes. Sulfonamide antibiotics formed more HANs compared to aniline, and aromatic secondary amines formed more HANs than the alkyl secondary amine.
The speciation of THMs and HANs when treated with chlorine and monochloramine is influenced by the presence of bromide at both low and high concentrations. The THM speciation changes from chlorinated species to mono- and di-bromo substituted species when the bromide content in the aqueous matrix rises from 0 to 50 ppb. However, at a higher bromide concentration (500 ppb), the tri-bromo substituted species might have formed or both formed and decomposed as they are not above the method reporting limit (MRL) values. Upon reaction with free chlorine or monochloramine, nitrogenous precursors do not yield N-nitrosamines or the concentration of any N-nitrosamines formed are below the limit of detection. Finally, nitrogenous precursors considered in this study have the potential to form HAAs only for monochloramination.
This is the first study to demonstrate the formation of HAAs, HANs and THMs from nitrogenous agrochemicals (atrazine, carbaryl, and simazine) and pharmaceuticals (sulfanilamide, sulfisoxazole, and sulfacetamide) during disinfection. This study also investigated the effect of bromide on the formation of DBPs. Finally, the concentration of DBPs generated after the disinfection of water containing environmentally significant quantities of the studied precursors was predicted. There is very little concern about reaching regulated DBP levels with these compounds unless the environmental concentrations increase substantially.