Cation Impact on N-Nitrosodimethylamine (NDMA) Formation from Ranitidine in Different Water Matrices

In previous research, ranitidine has formed high yields of the disinfection by-product N-Nitrosodimethylamine (NDMA) upon chloramination. In the current research, bench-scale experiments were conducted to investigate the impact of cations (i.e., Ca2+, Mg2+, and Na+) on NDMA formation from ranitidine in three water matrices (Milli-Q® water, Lake Ontario water, and Otonabee River water) under practical chloramine disinfection conditions. In Milli-Q® water, excess cations did not change the yields of NDMA. NDMA formation kinetic profiles monitored in the lake and river water also indicated that elevating the cation concentrations did not affect the ultimate NDMA formation from ranitidine, but then did affect the observed rates of NDMA formation; the rates underwent an initial decrease and a subsequent increase as the cation concentrations were increased. The lowest reaction rates were observed in the lake and river water samples when they have a hardness level of 240 and 203 mg/L as CaCO3, respectively.MAS