Ranitidine – A Potential Significant NDMA Precursor for Potable Reuse

N-nitrosodimethylamine (NDMA) is an unregulated disinfection byproduct, but it is a top concern for potable water reuse. Treated wastewater is known to contain many different precursors that form NDMA upon chloramination or ozonation. This study focuses on the fate of one chloramine-reactive NDMA precursor, ranitidine (an antacid drug commonly consumed by humans), through two wastewater treatment plants (WWTPs) and along an urban wash that is dominated by the WWTP effluents. The urban wash feeds directly into the reservoir that supplies drinking water for the same community that produced the wastewater. Samples were collected after various wastewater treatment processes at two wastewater treatment plants and at well-studied locations along the urban wash. The samples were analyzed for ranitidine and NDMA formation potential. Ranitidine was present at significant concentrations in the primary effluent (2.2 µg/L), the UV-disinfected final effluent (0.66 µg/L), and throughout the urban wash (0.084-0.12 µg/L). Ranitidine accounted for 12-24% of the NDMA formation potential in the wastewater samples (722-3222 ng/L) and 5-6% of the NDMA formation potential in the urban wash (256-356 ng/L). Considering the substantial number of known NDMA precursors, this single compound accounts for a sizeable fraction of the NDMA formation potential at this site. Ranitidine was not present in the treated wastewater effluent for two other wastewater treatment plants (chlorination disinfection) located along the same urban wash. An implication of this study is that changing from UV to chlorination or ozonation would result in removing this high-yield precursor from the urban wash, which would reduce the potential for NDMA in the community’s drinking water.