Abstract
N-nitrosodimethylamine (NDMA) is a probable human carcinogen formed as a by-product of the chlorination and ozonation of water. It is photodegradable by UV irradiation, but its reformation is suspected when chlorine is added to UV-irradiated water. In this research, the photodegradation of NDMA by irradiation with excimer, low-pressure (LP), and medium-pressure (MP) UV lamps was investigated using NDMA solutions with an initial concentration of 100 ng·L-1. To examine the effects of coexisting matters on the photodegradation and reformation of NDMA, Suwannee River NOM and/or nitrate was added to the test solutions at concentrations below the drinking water standard in Japan. The rates of photodegradation by using the excimer, LP, and MP UV lamps were 8.7, 2.7, and 2.3 cm2·J-1, respectively. The photodegradation rate was reduced by coexisting matters at about 40-90%, 7-50%, and 20-60% for the excimer, LP, and MP UV lamp, respectively. The increase in NDMA formation potential by chloramination was 5 ng·L-1 or less, regardless of the coexisting matters.
