Rejection of pharmaceutically-based N-nitrosodimethylamine precursors using nanofiltration

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Analytical Chemistry

Background:

• N-Nitrosodimethylamine (NDMA) is a harmful disinfection by-product (DBP) originating from precursors like pharmaceuticals in wastewater.
• Conventional tight nanofiltration and reverse osmosis membranes remove many contaminants but are energy-intensive.
• Looser membranes present a potential for cost-effective contaminant removal.

Purpose of the Study:

• To evaluate the efficacy of looser nanofiltration membranes (MW cutoff ~350 Da) in rejecting NDMA precursors.
• To compare precursor rejection across different water matrices (MQ water, raw surface waters).
• To assess the impact of natural organic matter, colloids, and ions on membrane performance.

Main Methods:

• Utilized nanofiltration membranes with a molecular weight cutoff of approximately 350 Da.
• Tested rejection of amine-containing pharmaceuticals (NDMA precursors, ~300 Da) in various water types.
• Employed NDMA formation potential testing to quantify precursor removal.
• Compared rejection rates using single pharmaceutical compounds versus mixtures.

Main Results:

• Nanofiltration membranes demonstrated high rejection rates (>84%) for NDMA precursors across all tested water matrices.
• The presence of natural organic matter, colloids, and inorganic ions did not significantly affect precursor rejection.
• Pharmaceutical mixtures showed similar rejection rates to single-spiked compounds.

Conclusions:

• Looser nanofiltration membranes are effective in removing NDMA precursors from diverse water sources, including those with complex matrices.
• NDMA formation potential testing is a reliable method for assessing precursor removal in challenging samples like wastewater.
• This technology offers an energy-efficient approach to mitigating NDMA formation in water treatment.