Abstract
This study investigated the removal characteristics of N-Nitrosamines and their precursors at three pilot-scale water reclamation plants. These plants applies different integrated membrane systems: (1) microfiltration (MF)/nanofiltration (NF)/reverse osmosis (RO) membrane; (2) sand filtration/three-stage RO; and (3) ultrafiltration (UF)/NF and UF/RO. Variable removal of N-Nitrosodimethylamine (NDMA) by the RO processes could be attributed to membrane fouling and the feed water temperature. The effect of membrane fouling on N-Nitrosamine removal was extensively evaluated at one of the plants by conducting one month of operation and chemical cleaning of the RO element. Membrane fouling enhanced N-Nitrosamine removal by the pilot-scale RO process. This finding contributes to better understanding of the variable removal of NDMA by RO processes. This study also investigated the removal characteristics of N-Nitrosamine precursors. The NF and RO processes greatly reduced NDMA formation potential (FP), but the UF process had little effect. The contributions of MF, NF, and RO processes for reducing FPs of NDMA, N-Nitrosopyrrolidine and N-Nitrosodiethylamine were different, suggesting different size distributions of their precursors.
Highlights
In response to increasing indirect and direct potable reuse of reclaimed water, the monitoring and control of micropollutant concentrations are increasingly important
This study investigated the removal characteristics of N-Nitrosamines and their precursors at three pilot-scale membrane systems for water reclamation
The extensive evaluation at a plant revealed that membrane fouling enhanced N-Nitrosamines removal by the pilot-scale reverse osmosis (RO) process
Summary
In response to increasing indirect and direct potable reuse of reclaimed water, the monitoring and control of micropollutant concentrations are increasingly important. N-Nitrosamines are of key concern for potable reuse, and further research and monitoring of them are recommended [4,7,8] These N-Nitrosamines include N-Nitrosodimethylamine (NDMA), N-Nitrosomethylethylamine (NMEA), N-Nitrosopyrrolidine (NPYR), N-Nitrosodiethylamine (NDEA), N-Nitrosopiperidine (NPIP), N-Nitrosomorpholine (NMOR), N-Nitrosodipropylamine (NDPA), and N-Nitrosodi-n-butylamine (NDBA). Most of these N-Nitrosamines are probable carcinogens [9], and their frequent occurrence in raw and secondary-treated wastewater [10,11,12] and reclaimed water [7,13,14,15,16,17] has been reported.
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