Occurrence of N-nitrosodimethylamine precursors in wastewater treatment plant effluent and their fate during ultrafiltration-reverse osmosis membrane treatment

The formation of N-nitrosodimethylamine (NDMA) is of major concern among wastewater recycling utilities practicing disinfection with chloramines. The NDMA formation potential (FP) test is a simple and straightforward method to evaluate NDMA precursor concentrations in waters. In this paper we show the NDMA FP results of a range of tertiary wastewater treatment plants that are also the source for production of recycled water using an Ultrafiltration - Reverse Osmosis (UF-RO) membrane process. The results indicate that the NDMA FP of different source waters range from 350 to 1020 +/- 20 ng/L. The fate of these NDMA precursors was also studied across the different stages of two Advanced Water Treatment Plants (AWTP) producing recycled water. These results show that more than 98.5 +/- 0.5% of NDMA precursors are effectively removed by the Reverse Osmosis (RO) membranes used at the AWTPs. This drastically reduces any potential for re-formation of NDMA after the RO stage even if chloramines may be present (or added) there.