Direct potable reuse: NDMA control strategies

N-nitrosodimethylamine (NDMA), a nitrosamine, is a toxic carcinogen and is considered a key contaminant of emerging concern (CEC) for direct potable reuse (DPR). It has been reported in foods, beverages, drugs, and tobacco smoke and to be an air and water contaminant. NDMA is also used as an industrial solvent, an anti-oxidant, a rubber accelerator, and in the preparation of polymers, where it may be used as an initiator or a plasticizer, in the production of rocket fuel, as a biocide for nematodes, and an intermediate for 1,1-dimethylhydrazine to inhibit nitrification of soils, therefore it is present in raw wastewater and may be formed during disinfection at water treatment plants. Given the NDMA detections associated with drinking water and recycled water sources and treatment, NDMA is a good candidate for future regulation (i.e., establishment of a drinking water standard, also known as a maximum contaminant level or MCL). An MCL for NDMA will likely not be available for several years, so the 10-ng/L notification level established by the California State Water Resources Control Board Division of Drinking Water (DDW) will continue to be used to provide information to local governing agencies and consumers. The City of Los Angeles, Bureau of Sanitation (LASAN) is implementing the Donald C Tillman Water Reclamation Plant (DCTWRP) Groundwater Replenishment (GWR) Advanced Water Purification Facility Pilot Project to evaluate and compare performance of the full advanced treatment (FAT) train and alternative DPR treatment trains. In parallel, the WRRF Tailored Collaboration project [NDMA Precursor Control Strategies for Direct Potable Reuse (WRRF-15-13)] will characterize NDMA precursor sources, optimize NDMA and NDMA precursor removal in the DCTWRP Modified Ludzack-Ettinger (MLE) Activated Sludge Process, across FAT and alternative DPR treatment trains and evaluate NDMA formation post-advanced treatment. The paper will present fact sheets on a wide range of individual water quality characteristics, arranged by treatment process category tested at full scale and through candidate FAT and DPR pilot trains being tested and the application of a considered NDMA/Nitrosamine Precursors Control Strategies approach.