Identification of new ozone disinfection byproducts in drinking water

Using a combination of spectral identification techniques-gas chromatograph- y coupled with low- and high-resolution electron-impact mass spectrometry (GC/EI-MS), low- and high-resolution chemical ionization mass spectrometry (GC/CI-MS), and infrared spectroscopy (GC/ IR)-we identified many drinking water disinfection byproducts (DBPs) formed by ozone and combinations of ozone with chlorine and chloramine. Many of these DBPs have not been previously reported. In addition to conventional XAD resin extraction, both pentafluorobenzylhydroxylamine (PFBHA) and methylation derivatizations were used to aid in identifying some of the more polar DBPs. Many of the byproducts identified were not present in spectral library databases. The vast majority of the ozone DBPs identified contained oxygen in their structures, with no halogenated DBPs observed except when chlorine or chloramine was applied as a secondary disinfectant. In comparing byproducts formed by secondary treatment of chlorine or chloramine, chloramine appeared to form the same types of halogenated DBPs as chlorine, but they were generally fewer in number and lower in concentration. Most of the halogenated DBPs that were formed by ozone-chlorine and ozone-chloramine treatments were also observed in samples treated with chlorine or chloramine only. A few DBPs, however, were formed at higher levels in the ozone-chlorine and ozone-chloramine samples, indicating that the combination of ozone and chlorine or chloramine is important in their formation. These DBPs included dichloroacetaldehyde and 1,1-dichlo- ropropanone.