Removal of N-nitrosamines by an aerobic membrane bioreactor

This study investigated the fate of eight N-nitrosamines during membrane bioreactor (MBR) treatment. The results suggest that biodegradation is mainly responsible for the removal of N-nitrosamines during MBR treatment. Other removal mechanisms were insignificant (e.g. adsorption to sludge) or not expected (e.g. photolysis and volatilization) given the experimental conditions and physicochemical properties of the N-nitrosamines studied here. N-nitrosamine removal efficiencies were from 24% to 94%, depending on their molecular properties. High removal of N-nitrosamines such as N-nitrosodimethylamine and N-nitrosodiethylamine could be explained by the presence of strong electron donating functional groups (EDG) in their structure. In contrast, N-nitrosomorpholine possessing the weak EDG morpholine was persistent to biodegradation. The removal efficiency of N-nitrosomorpholine was 24% and was the lowest amongst all N-nitrosamines investigated in this study.

► Fate and transport of eight N-nitrosamines during MBR treatment were examined. ► Biodegradation was solely responsible for the removal of all N-nitrosamines. ► Biodegradation of N-nitrosamines could be explained by their molecular structure. ► Removal efficiencies of acyclic N-nitrosamines by MBR treatment were moderate/high. ► NMOR was persistent to MBR treatment due to the presence of the morpholine group.