The objective of this study was to validate and optimize a promising method that is fast and relatively inexpensive for the analysis of N-nitrosodimethylamine (NDMA) and other nitrosamines in water via trialing at a large wastewater reclamation facility operated by the Orange County Water District (OCWD). OCWD’s Advanced Water Purification Facility (AWPF) produces highly treated water for indirect potable reuse as part of the Groundwater Replenishment System (GWRS). OCWD routinely monitors occurrence of NDMA in the AWPF, for example as an indicator of treatment performance for removal of wastewater-derived organic compounds. NDMA belongs to the N-nitrosamines family and is of particular concern due to its U.S. EPA-determined 10-6 lifetime excess cancer risk corresponding to 0.7 ng/L in drinking water (USEPA 2014). Current methods of quantifying NDMA are time consuming and expensive. This study validated a rapid benchtop method that, unlike conventional methods, does not require sample pre-concentration nor mass spectrometry, yet achieves the same or better detection limits at the low nanogram per liter (ng/L) level. This method uses high performance liquid chromatography (HPLC) combined with a photochemical reactor and a chemiluminescence detection system (HPLC-PR-CL). The project team performed split sample analysis comparing the HPLC-PR-CL method with a conventional method (sample pre-concentration followed by GC-MS/MS) for water collected from the OCWD AWPF on a weekly basis. The HPLC-PR-CL method precision for different matrices was determined in AWPF waters. The project team also evaluated the potential for matrix interference which may be unique to advanced treated wastewater (e.g., wastewater-derived organics that may occur prior to reverse osmosis treatment, finished product water containing residual oxidants, etc.). Additionally, the project team evaluated the method for its ability to measure a range of N-nitrosamines in AWPF water beyond NDMA. This included N-nitrosomorpholine (NMOR), which has been detected in AWPF water by OCWD previously, as well as N-nitrosomethylethylamine (NMEA) and N-nitrosopyrrolidine (NPYR).

Validation and optimization of an alternative method for NDMA analysis requiring less time, cost, and sample volume

253rd National Meeting (2017)

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