TREATMENT OF GROUNDWATER CONTAMINATED WITH NNITROSODIMETHYLAMINE (NDMA) USING A FLUIDIZED BED BIOREACTOR

摘要

N-Nitrosodimethylamine (NDMA) is a known carcinogen and an emerging groundwaterrncontaminant that is present at numerous Department of Defense installations. For military andrnNASA installations involved in the production, testing, and/or disposal of liquid rocketrnpropellants containing 1,1-dimethylhydrazine, NDMA is often present in groundwater. Due tornits carcinogenicity, the State of California recently established a public health goal (PHG) forrnNDMA in drinking water of 3 ng/L. Currently, the only effective treatment technology forrnNDMA in groundwater is pump-and-treat with ultraviolet irradiation (UV). However, thisrnapproach is energy intensive and expensive. With the increase in the cost of electricity, it isrnimportant to evaluate potentially less expensive treatment options for this compound. Thernobjective of this study is to demonstrate and validate the use, performance, and cost of arnbiological fluidized bed reactor (FBR) for the treatment of NDMA in groundwater (Webster etrnal., 2009). The FBR is an efficient fixed-film bioreactor in which a high concentration ofrnbiomass is attached onto fluidized medium where biological treatment of the NDMArncontaminated water occurs. This technology has previously been implemented at full-scale forrnthe treatment of perchlorate at DoD and DoD contractor sites, but this design has not beenrnevaluated for treatment of NDMA.rnThis Environmental Security Technology Certification Program (ESTCP) project builds upon thernsuccessful results from the Strategic Environmental Research and Development Programrn(SERDP) Project ER-1456, the objective of which was to examine the potential for in situ and exrnsitu biodegradation of NDMA in groundwater (Hatzinger et al., 2008). During this SERDPrnproject, the propanotroph, Rhodococcus ruber ENV425, was found to effectively degradernNDMA during growth on propane. Results from batch experiments and a laboratory bioreactorrnstudy with R. ruber ENV425 revealed that NDMA biological treatment of typical groundwaterrnconcentrations (e.g., 1-80 μg/L) to levels below 10 ng/L was readily achievable. Hence, the usernof ENV425 within an FBR system to treat NDMA may be technically feasible and cost effective.rnIn conjunction with ESTCP and NASA White Sands Test Facility (WSTF), EnvirogenrnTechnologies, Inc. and Shaw Environmental, Inc. are testing the feasibility of utilizing an FBRrnfor the cost-effective treatment of NDMA. The Phase 1 treatability study entailed initial batchrnmicrocosm studies to evaluate the ability of ENV425 to mineralize the NDMA in the WSTFrnwater, followed by extensive FBR bench-scale testing to assess reactor performance and tornevaluate different operating conditions (i.e., hydraulic residence time, propane, and oxygenrnaddition rates, etc.). Based on the success of the laboratory and bench-scale studies, the nextrnphases of this project are the design, fabrication, installation and operation of a pilot-scale FBRrnat the WSTF site.rnFor the initial bench-scale microcosm study, ENV425 rapidly mineralized 55-60% of the NDMArnin a sample of WSTF water. Based on the extent of mineralization and evidence of cell growth,