Nitrosamines are considered as probable human carcinogens by the U.S. Environmental Protection Agency (USEPA), and they are listed in the USEPA's Contaminant Candidate List 3. The most studied nitrosamine is N-Nitrosodimethylamine (NDMA) which is mutagenic with a life time cancer risk of 10-6 for a concentration of 0.7 ng L-1 in drinking water. Even more stringent regulations and advisories are enforced in various states across the United States for NDMA removal and control. Thus, studies on technologies able to eliminate NDMA and related precursors are crucial as well as the identification of possible precursor source. Full-scale experiments were performed at a wastewater reclamation plant that through advanced technologies, including microfiltration (MF), reverse osmosis (RO), UV/advanced oxidation process (UV/H2O2), is able to produce recycled water of qualities necessary for potable applications. Further ozonation tests were accomplished at bench scale. Results of the study showed that RO treatment was able to remove the most NDMA precursors present in the investigated wastewater and the NDMA concentration in the chloraminated RO permeate remained stable over time. The UV/H2O2 system following the RO membrane was able to degrade NDMA but the process effectiveness depended on applied UV dose and hydrogen peroxide addition. Particularly, hydrogen peroxide and a lower UV dose decreased the photo-degradation of NDMA due to a competition between H2O2 and NDMA for photons. Finally, ozone produced relevant levels of NDMA that raised further whit higher ozone dose. NDMA formation depended on the applied ozone dose before reaching a plateau when all the precursors were consumed. On the contrary, chloramination or chloramination post ozonation has always resulted in a slight increase of NDMA. Investigation of precursor source in wastewater and evaluation of possible NDMA formation pathways upon ozonation was also accomplished.

Formation and control of NDMA during wastewater reclamation: The role of advanced treatments

248th National Meeting (2014)

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