Abiotic and Biotic Mechanisms Controlling In Situ Remediation of NDMA

Abstract

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. REPORT DATE MAY 20092. REPORT iii Executive SummaryThis project was initiated to investigate whether in situ coupled abiotic/biotic degradation of N-nitrosodimethylamine (NDMA, an emerging contaminant) could be used as a permeable reactive barrier for remediation at the Aerojet, California site, where groundwater contains up to 36-ppb NDMA. The sediment mainly used in experiments is from the Aerojet groundwater aquifer (260-ft depth), with additional sediments from other groundwater aquifers (i.e., not shallow soils, Ft. Lewis, Washington, 60-ft depth, Puchack, New Jersey, 273-ft depth). Different in situ remediation processes were compared in this study: a) biostimulation (oxic, anaerobic, iron-reducing, sulfate-reducing), b) abiotic iron-reducing environment (by dithionite reduction of sediment or zero valent iron addition), c) coupled abiotic/biotic remediation (iron-reducing environment), and d) sequential iron-reducing, then oxic, biostimulation. The overall goal was to understand and optimize the combined effects of abiotic and biotic processes to degrade NDMA to nontoxic products. Iron-reducing conditions were created by chemical reduction of a sediment using sodium dithionite, and in a few cases, a natural reduced aquifer sediment or sediment with zero valent iron addition.When subsurface sediments are chemically or naturally reduced, abiotic surface phase(s) rapidly degraded NDMA (8-hour half-life for high reduction, slower for low reduction) to nontoxic dimethylamine (DMA). Experiments showed up to 80% conversion of NDMA to DMA, with further degradation to nitrate (up to 40% molar conversion), formate (trace concentration) and carbon dioxide (up to 82% molar conversion). Methylamine and formaldehyde (likely intermediates) were not detected. Experiments with 100 and 10 ng/L NDMA starting concentration had a rapid degradation half-life (4.7 hours), and NDMA was degraded to <3 ng/L (detection limit). Although degradation to DMA is sufficient for remediation (DMA is not toxic at <5 mg/L), because NDMA mass was degraded further to more toxic intermediates, NDMA mineralization (i.e., to CO 2 ) was considered the lowest risk product, and was the main focus of this study. NDMA degradation was most rap...

Differential Microbial Transformation of Nitrosamines by an Inducible Propane Monooxygenase

“…35,40−45 The discrepancy in rates between propane-and LB-grown RHA1 indicates that induction of the PrMO enzyme leads to enhanced biotransformation potential of multiple nitrosamines. Propane, which stimulates a number of monooxygenase enzymes with potential applications in trace organic bioattenuation, 29,31,46−49 has been employed to enhance NDMA mineralization in aquifer sediments 50 and in field settings to promote subsurface TCE 51 and MTBE 52 bioremediation. A propane-fed membrane bioreactor seeded with another Rhodococcus strain removed NDMA from 8 μg/L to concentrations of <2 ng/L.…”

“…Abiotic NDMA degradation has been documented in chemically reduced subsurface sediment although NDMA was mineralized to a greater extent (30−81%) in oxic sediments treated with propane to stimulate monooxygenase activity. 50 Passive abiotic attenuation of larger nitrosamines in the subsurface seems unlikely.…”

Loading Rates and Impacts of Substrate Delivery for Enhanced Anaerobic Bioremediation

“…N-nitrosodimethylamine (NDMA) is used with propellants and is a carcinogen and emerging groundwater contaminant at a number of DoD and DOE facilities. NDMA may be amendable to enhanced in situ bioremediation (Szecsody et al, 2009;Hatzinger et al, 2008;Finneran et al, 2007). The ESTCP is currently demonstrating an alternative degradation process for NDMA using injection (biosparging) of propane gas and oxygen to stimulate degradation by propanotrophs, a class of indigenous microorganisms that have been shown to rapidly degrade NDMA to innocuous products (ER-200828).…”