Fate of N-nitrosomorpholine in an anaerobic aquifer used for managed aquifer recharge: A column study

The fate of N-nitrosomorpholine (NMOR) was evaluated at microgram and nanogram per litre concentrations. Experiments were undertaken to simulate the passage of groundwater contaminants through a deep anaerobic pyritic aquifer system, as part of a managed aquifer recharge (MAR) strategy. Sorption studies demonstrated the high mobility of NMOR in the Leederville aquifer system, with retardation coefficients between 1.2 and 1.6. Degradation studies from a 351 day column experiment and a 506 day stop-flow column experiment showed an anaerobic biologically induced reductive degradation process which followed first order kinetics. A biological lag-time of less than 3 months and a transient accumulation of morpholine (MOR) were also noted during the degradation. Comparable half-life degradation rates of 40–45 days were observed over three orders of magnitude in concentration (200 ng L−1 to 650 μg L−1). An inhibitory effect on microorganism responsible to the biodegradation of NMOR at 650 μg L−1 or a threshold effect at 200 ng L−1 was not observed during these experiments.

► Anaerobic conditions of Leederville aquifer was suitable for NMOR biodegradation. ► NMOR biodegradation half-life was 40–45 days for concentrations up to 650 μg L−1. ► Biological lag-time of NMOR was less than 3 months. ► No NMOR inhibitory effects at 650 ng L−1, or threshold effect at 200 ng L−1 were observed. ► NMOR was highly mobile in the Leederville aquifer.