Experimental study on N-nitrosamine disinfection by-products produced by four pharmaceuticals and personal care products during chlorination disinfection

Objective  To investigate the effect of pharmaceuticals and personal care products (PPCPs) on the formation potential of the nitrogen-containing disinfection by-products N-nitrosamines (NAs) after entering the water environment and being oxidized by chlorination.

Methods  Four commonly used pharmaceuticals, i.e., ranitidine, nizatidine, chlorpheniramine, and doxylamine, were selected as precursors, and sodium hypochlorite, monochloramine, and dichloramine were used as disinfectants to simulate the chlorination procedure in water treatment process. The formation potential of eight NAs was analyzed, namely N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosomethylethylamine (NMEA), N-nitrosodi-n-propylamine, N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMOR), N-nitrosopiperidine (NPIP), and N-nitrosopyrrolidine.

Results  NDMA was the main substance produced by the four pharmaceuticals during chlorination disinfection, accompanied by the production of NMEA, NDEA, NMOR, and NPIP, and NDMA showed the highest formation potential after monochloramine disinfection. Ranitidine showed the highest formation potential of NDMA potential regardless of sodium hypochlorite disinfection or chloramine disinfection. Ranitidine could also produce NPIP after oxidation with sodium hypochlorite, and it became a precursor with relatively high formation potential of NAs due to its structural characteristics.

Conclusion  All four PPCPs are precursors for the production of NAs during chlorination disinfection, and controlling the emission of PPCPs into the environment at source or optimizing the disinfection process can effectively control the production of NAs.