Identification of Antiyellowing Agents as Precursors of N-Nitrosodimethylamine Production on Ozonation from Sewage Treatment Plant Influent

In Japan, N-nitrosodimethylamine (NDMA)formation associated with ozonation at a relatively high concentration as been reported only at a small number of water treatment plants (WTPs) in the western part of Japan for which the source water is the Yodo River. In the present study, the formation of relatively high concentrations of NOMA was found upon ozonation of water samples taken from sewage treatment plants (STPs) located upstream of the water intake points of the WTPs in the Yodo River basin. NOMA concentrations before and after ozonation were 16-290 and 14-280 ng/L, respectively. At least some of the STPs investigated receive industrial effluents. Atone STP in this area, an extremely high concentration of NOMA (10 000 ng/L) was found in one influent water sample after ozonation. To identify potential NOMA precursors upon ozonation in the influent at this STP, the concentrated extracts of the influent were fractionated by high-performance liquid chromatography (HPLC). Ultraperformance liquid chromatography coupled with tandem mass spectrometry (UPLC/MS/MS) identified 4,4'-hexamethylenebis(1,1-dimethylsemicarbazide) (HDMS) and 1,1,1'1'-tetramethyl-4,4'-(methylene-di-p-phenylene)disemicarbazide (TMDS) as precursors of NOMA on ozonation of the influent Both HDMS and TMDS are used as antiyellowing agents in polyurethane fibers and as light stabilizers in polyamide resins. Their contributions to NOMA production on ozonation of water samples at STPs were up to 17%. The remaining unidentified NOMA precursors may be hydrophilic compounds that were not trapped by the cartridges used for extraction of the water samples. HDMS and TMDS were frequently present in surface waters and STP effluents in the Yodo River basin and were also detected in surface waters from several other areas in Japan.