Nitrosamines and haloacetamides are nitrogenous disinfection byproducts (NDBPs). Certain pharmaceuticals are known to form these NDBPs in water treatment processes. For example, metformin forms nitrosamines during chloramination. Acetaminophen forms haloacetamides during chlorination. Given that metformin and acetaminophen are the two most widely used pharmaceuticals in Taiwan, this study explored the effect of the co-presence of these pharmaceuticals on the formation of their known NDBP groups during chlorination or chloramination. Batch experiments with different concentration ratios of chlorine to pharmaceutical were carried out, followed by solid-phase extraction and analysis using gas chromatography-mass spectrometry (GC-MS). The results showed that during chlorination, nitrosamine formation was increased as the concentration ratio of chlorine to metformin was increased. A high concentration ratio of chlorine to acetaminophen inhibited the formation of haloacetamide. More importantly, when two pharmaceuticals were co-present, higher chlorine to pharmaceutical concentration ratio increased the number of the NDBP species formed and their formation yields. During chloramination, the trends of NDBP formation in the presence of individual pharmaceuticals were similar to those during chlorination. Nevertheless, only one dichloroacetamide was formed during chloramination of two pharmaceuticals co-present, with its formation yield being reduced by 75%. As metformin and acetaminophen were widely used in Taiwan and many other regions of the world and are expected to co-exist in the environments, the co-presence of metformin and acetaminophen in the environments changed their NDBP formation typically studied in the absence of other pharmaceuticals.

Effect of the co-presence of pharmaceuticals on the formation of nitrosamine and haloacetamide during chlor(am)ination of metformin and acetaminophen

ACS Spring 2022

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