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Composting is an ''ex situ'' technology for treatment of excavated soils impacted by recalcitrant contaminants, including nitroaromatic and nitramine explosives. The process involves mixing contaminated soil with bulking agents (wood chips, straw, hay or alfalfa), and organic amendments (cattle and/or chicken manure, other vegetative wastes). Ingredient selection depends on the contaminants to be treated, soil characteristics, and availability of low-cost organic amendments. Advantages of windrow composting include more rapid degradation of explosive compounds, end-product reuse, applicability to a wide range of soils, self-heating treatment process, and year round operation without external heating. Cost drivers include land requirements, treatment batch size, venting requirements, soil characteristics, nutrient and bulking agent addition, and turnover frequency.  
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N-Nitr2017osodimethylamine (NDMA) is a suspected human carcinogen that can enter water supplies from some military and industrial sources. NDMA is mobile in water, does not strongly sorb to solids or volatilize, and does not easily biodegrade.  However, recent work has shown that NDMA can be effectively treated in both above ground and ''in situ'' cometabolic biological treatment systems.
  
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
  
 
'''Related Article(s):'''
 
'''Related Article(s):'''
*[[Munitions Constituents]]
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*[[In Situ Anaerobic Bioremediation]]
*[[Munitions Constituents - Alkaline Degradation]]
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*[[In Situ Anaerobic Bioremediation Design Considerations]]
 +
*[[Chlorinated Solvents]]
  
'''CONTRIBUTOR(S):''' [[Harry Craig]]
 
  
 +
'''CONTRIBUTOR(S):''' [[Paul Hatzinger]]
  
 
'''Key Resource(s)''':
 
'''Key Resource(s)''':
*[[media:2011-ACOE-pwtb_200_1_95.pdf| ACOE (2011) Soil Composting for Explosives Remediation: Case Studies and Lessons Learned.]]<ref name= "ACOE2011">ACOE, 2011. Soil Composting for Explosives Remediation: Case Studies and Lessons Learned, U.S. Army Corps of Engineers, Public Works Technical Bulletin 200-1-95. [[media:2011-ACOE-pwtb_200_1_95.pdf| Report.pdf]]</ref>  
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*[[media:2015-Hatzinger-Field_Demonstration_of_Propane_Biosparging.pdf| Field Demonstration of Propane Biosparging for "In Situ" Remediation of NDMA]]<ref name= "Hatzinger2015">Hatzinger, P.B. and Lippincott, D., 2015. Field Demonstration of Propane Biosparging for In Situ Remediation of N-Nitrosodimethylamine (NDMA) in Groundwater. ESTCP Project ER-200828 [[media:2015-Hatzinger-Field_Demonstration_of_Propane_Biosparging.pdf| Report.pdf]]</ref>
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*[https://doi.org/10.1089/109287503768335896 N-nitrosodimethylamine (NDMA) as a drinking water contaminant: a review]<ref name= "Mitch2003">Mitch, W.A., Sharp, J.O., Trussell, R.R., Valentine, R.L., Alvarez-Cohen, L. and Sedlak, D.L., 2003. N-nitrosodimethylamine (NDMA) as a drinking water contaminant: a review. Environmental Engineering Science, 20(5), pp.389-404. [https://doi.org/10.1089/109287503768335896 doi: 10.1089/109287503768335896]</ref>
  
==Overview==
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==Introduction==
Composting is an ''ex situ'' technology designed to treat excavated soils impacted by a range of recalcitrant contaminants, including nitroaromatic and nitramine explosive compounds. The process involves mixing contaminated soil with bulking agents such as wood chips, straw, hay or alfalfa, and organic amendments such as cattle and/or chicken manure, or other vegetative wastes.  
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N-Nitrosodimethylamine (NDMA) is a suspected human carcinogen that has traditionally been detected in specific food products, such as cured meats (e.g., cold cuts preserved with nitrite), smoked fish, and some cheeses as well as chewing and smoking tobacco. NDMA is not commercially manufactured, but potential industrial sources include byproducts from rubber tire manufacturing, tanneries, some pesticide and dye plants, and fish processing facilities. NDMA has also been detected in groundwater at several military and aerospace sites involved in the production, testing, and/or disposal of liquid rocket propellants formulated with 1,1-dimethylhydrazine (1,1-DMH or UDMH). It is also frequently reported at ng/L concentrations in water and wastewater that has been disinfected with chloramine<ref name= "Mitch2003"/>.  
  
The selection of specific compost ingredients depends on the contaminants to be treated, the physical/chemical characteristics of the soil, and the availability of low-cost organic amendments. The goal is to achieve the desired bulk density, porosity, and organic amendments that can provide the proper balance of carbon and nitrogen (C/N ratio) to promote biological activity in the compost. For most composting applications, it is necessary to provide amendments that will support mesophilic ([https://en.wikipedia.org/wiki/Mesophile Mesophile]) or thermophilic ([https://en.wikipedia.org/wiki/Thermophile Thermophile]) microbial activity<ref name= "USEPA2002APC">U.S. Environmental Protection Agency (USEPA), 2002. Application, performance, and costs of biotreatment technologies for contaminated soils. EPA/600/R-03/037 (NTIS PB2003-104482). [[media:2002-EPA-Application%2C_Performance%2C_and_Costs_for_Biotreatment_Tech_for_Cont_Soils.pdf| Report.pdf]]</ref>.
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[[File:Hatzinger1w2 Fig1.png|thumb|Figure 1. NDMA chemical structure]]
  
==Principle of Operation==
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No Federal Maximum Contaminant Level (MCL) has been promulgated for NDMA in drinking water because it was historically thought to be an issue associated primarily with foods and tobacco, but NDMA and other nitrosamines were added by USEPA to both the Unregulated Contaminant Monitoring Rule-2 (UCMR-2) and Contaminant Candidate List-3 (CCL3). UCMR-2 requires many large water utilities to sample for the compound, and CCL3 provides a potential basis for contaminant regulation under the Safe Drinking Water Act (SDWA) based on occurrence and potential risk to the public.  
Composting is a biological remediation technology that exploits the activity of a diverse range of microorganisms to degrade target contaminants. The biological activity is enhanced through the addition of readily degradable amendments to provide a sufficient supply of nutrients. As biological activity increases, compost temperatures reach mesophilic (<45°C) and potentially thermophilic (45° to 80°C) conditions, the latter of which experiences the greatest degradation<ref name= "Bruns2000">Bruns-Nagel, D., Steinbach, K., Gemsa, D. and von Löw, E., 2000. Composting (humification) of nitroaromatic compounds. Biodegradation of nitroaromatic compounds and explosives. Lewis Publishers, Boca Raton, Fla, pp.357-393. [https://doi.org/10.1201/9781420032673 doi: 10.1201/9781420032673]</ref>.  
 
  
Turning, mixing, and/or aeration of the compost provides oxygen for extracellular hydrolysis and aerobic catabolic reactions to take place. However, a high level of microbial activity can deplete oxygen between turning or aeration sequences, creating anoxic conditions in portions of the compost material that allow anaerobic catabolic reactions to occur.
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Among the states, California has established a public health goal of 3 ng/L and Massachusetts has set a regulatory standard of 10 ng/L in drinking water. These stringent requirements reflect the carcinogenicity of NDMA which, based on USEPA risk assessments, poses an increased cancer risk of one cancer per million at a drinking water concentration of only 0.7 ng/L<ref name= "USEPA2014TFS">USEPA. 2014. Technical Fact Sheet - N-Nitroso-dimethylamine. USEPA Office of Solid Waste and Emergency Response. EPA 505-F-14-005 [[media:2014-USEPA-N-Nitrosodimethylamine_fact_sheet.pdf| Report.pdf]]</ref>.
  
Formation of anoxic zones in the compost can be beneficial for promoting degradation of contaminants such as explosives that are recalcitrant or only partially degrade under strict oxic conditions. For contaminants that are readily mineralized under oxic conditions, the development of anoxic conditions is not desired, and turning, mixing, and/or aeration frequencies are adjusted to minimize oxygen depletion.  
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==Physical and Chemical Properties==
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NDMA, in its pure form, is a yellow liquid with a density of 1.0059 g/ml and molecular weight of 74.1 g/mol<ref name= "USEPA2014TFS"/>. It is miscible in water, relatively non-volatile and sorbs poorly to organic carbon, allowing it to readily migrate with groundwater. While NDMA is susceptible to photolysis, it is relatively recalcitrant in groundwater under both oxic and anoxic conditions, and forms large plumes at sites with concentrated sources (e.g., rocket motor test sites).  
  
[[File:Craig1w2 Fig1.png|thumb|400 px|Figure 1. Compound reductions for different composting techniques using soils from contaminated ammunition production sites. Error bars are ± 1 standard deviation. IVSP = in-vessel static pile; MAIV = mechanically agitated in-vessel. Data compiled by Bruns-Nagel et al. (2000)<ref name= "Bruns2000"/>.]]
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==Remediation==
==Early Development and Demonstration==
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[[File:Hatzinger1w2 Fig2.png|thumb|Figure 2. Field-Scale Propane-Fed FBR.]]
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[[File:Hatzinger1w2 Fig3.png|thumb|Figure 3. Layout of biosparging system<ref name= "Hatzinger2015"/>.]]
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[[File:Hatzinger1w2 Fig4.png|thumb|Figure 4. Field-Scale "In Situ" Propane Biosparging System]]
  
The initial proof of concept and scale up from laboratory to pilot scale tests for composting explosives contaminated soils and lagoon sediments began in the 1980s. Early data had promising degradation results (92% to 97%) for a range of explosives including TNT, RDX, HMX, and tetryl, but soil loading rates were low, generally 10% or less in the compost mixtures<ref>Isbister, J.D., Doyle, R.C. and Kitchens, J.F., 1982. Engineering and development support of general decon technology for the US Army's Installation Restoration Program. Task 2. Composting of Explosives. Atlantic Research Corp, Alexandria, Va. [[media:1982-Isbister-Engineering_and_development_Support_of_general_Decon_Tech.pdf| Report.pdf]]</ref><ref>Doyle, R.C., Isbister, J.D., Anspach, G.L. and Kitchens, J.F., 1986. Composting explosives/organics contaminated soils. Atlantic Research Corporation. [[media:1986-Doyle-Composting_Explosives_Organics_Contaminated_Soils.pdf| Report.pdf]]</ref>.  
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NDMA is typically removed from groundwater by extracting the contaminated groundwater followed by surface treatment with ultraviolet radiation (UV). NDMA decomposes in UV light in the 225 - 250 nm wavelength range. The primary products are dimethylamine and nitrite<ref>Stefan, M.I. and Bolton, J.R., 2002. UV direct photolysis of N‐nitrosodimethylamine (NDMA): Kinetic and product study. Helvetica Chimica Acta, 85(5), pp.1416-1426. [https://doi.org/10.1002/1522-2675(200205)85:5<1416::AID-HLCA1416>3.0.CO;2-I doi: 10.1002/1522-2675(200205)85:5<1416::AID-HLCA1416>3.0.CO;2-I]</ref>. UV treatment can reduce NDMA concentrations to low ng/L levels, but is expensive due to the high energy input required.  In potable water treatment systems, the UV dosage for NDMA removal can be a factor of ten greater than the dosage required to achieve equivalent virus removal<ref name= "Mitch2003"/>. 
  
Subsequent pilot scale treatability studies were conducted to evaluate mesophilic vs. thermophilic conditions<ref>Williams, R.T., Ziegenfuss, P.S. and Sisk, W.E., 1992. Composting of explosives and propellant contaminated soils under thermophilic and mesophilic conditions. Journal of Industrial Microbiology, 9(2), pp.137-144. [https://doi.org/10.1007/BF01569746 doi: 10.1007/BF01569746]</ref><ref>Garg, R., Grasso, D. and Hoag G., 1991. Treatment of explosives contaminated lagoon sludge. Hazardous Waste and Hazardous Materials, 8(4), pp.319-340. [https://doi.org/10.1089/hwm.1991.8.319 doi: 10.1089/hwm.1991.8.319]</ref>. A range of materials handling approaches including static piles, mechanically agitated in-vessel reactors (MAIV), and mixed aerated and nonaerated windrows<ref>Weston, R.F. , 1988. Field demonstration - composting explosives-contaminated sediments at the Louisiana Army Ammunition Plant (LAAP). [[media:1988-Weston-field_Demonstration_-_Composting_Explosives_at_LAAP.pdf| Report.pdf]]</ref><ref>Weston, R. F., 1991. Optimization of composting explosives contaminated soils at Umatilla, U.S. Army Toxic and Hazardous Materials Agency, Report No. CETHA-TS-CR-91053. [[media:1991-Weston-Optimization_of_Composting_Explosives_Contaminated_soils.pdf| Report.pdf]]</ref> <ref name= "Weston1993">Weston, R. F., 1993. Windrow composting demonstration for explosives-contaminated soils at the Umatilla Depot Activity Hermiston, Oregon. U.S. Army Environmental Center Report No. CETHA-TS-CR-93043. [[media:1993-Weston-Windrow_Composting_Demo_for_Explosives.pdf| Report.pdf]]</ref> were tested at Louisiana AAP (LAAP) and Umatilla Army Depot (UMDA) (see Figure 1). TNT degradation was similar in aerated and nonaerated windrows, but RDX and HMX degradation were greater in mixed unaerated windrows at 30% soil loading rates<ref name= "Weston1993"/><ref>Craig, H.D., Sisk, W.E., Nelson, M.D. and Dana, W.H., 1995. Bioremediation of explosives-contaminated soils: A status review. In Proceedings of the 10th Annual Conference on Hazardous Waste Research (pp. 164-179). Manhattan, NY, USA: Kansas State University. [[media:1995-Craig-Bioremediation_of_explosives-Contaminated_Soils.pdf| Report.pdf]]</ref>.
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Cometabolic biological treatment is an emerging technology for above ground and ''in situ'' treatment of NDMA. A variety of propane-oxidizing bacteria (propanotrophs) are capable of degrading NDMA<ref>Sharp, J.O., Sales, C.M., LeBlanc, J.C., Liu, J., Wood, T.K., Eltis, L.D., Mohn, W.W. and Alvarez-Cohen, L., 2007. An inducible propane monooxygenase is responsible for N-nitrosodimethylamine degradation by Rhodococcus sp. strain RHA1. Applied and Environmental Microbiology, 73(21), pp.6930-6938. [https://doi.org/10.1128/aem.01697-07 doi: 10.1128/AEM.01697-07]</ref><ref name= "Fournier2009">Fournier, D., Hawari, J., Halasz, A., Streger, S.H., McClay, K.R., Masuda, H. and Hatzinger, P.B., 2009. Aerobic biodegradation of N-nitrosodimethylamine by the propanotroph Rhodococcus ruber ENV425. Applied and environmental microbiology, 75(15), pp.5088-5093. [https://doi.org/10.1128/aem.00418-09 doi: 10.1128/AEM.00418-09]</ref><ref name= "Weidhaas2012">Weidhaas, J.L., Zigmond, M.J. and Dupont, R.R., 2012. Aerobic biotransformation of N-nitrosodimethylamine and N-nitrodimethylamine by benzene-, butane-, methane-, propane-, and toluene-fed cultures. Bioremediation Journal, 16(2), pp.74-85. [https://doi.org/10.1080/10889868.2012.665961 doi: 10.1080/10889868.2012.665961]</ref>.  When fed propane, these organisms produce a broad specificity monooxygenase enzyme (propane monooxygenase; PrMO) that cometabolically transforms NDMA producing methylamine, nitric oxide, nitrite, nitrate, and formate.  A major advantage of cometabolic degradation is that the microorganisms grow on the primary substrate (propane) allowing NDMA to be reduced to ultra-low concentrations. For example, the bacterium ''Rhodococcus ruber'' ENV425 degraded NDMA from concentrations as high as 80 g/L to < 10 ng/L in batch culture<ref name= "Fournier2009"/>, and in a membrane bioreactor<ref>Hatzinger, P.B., Condee, C., McClay, K.R. and Togna, A.P., 2011. Aerobic treatment of N-nitrosodimethylamine in a propane-fed membrane bioreactor. Water research, 45(1), pp.254-262. [https://doi.org/10.1016/j.watres.2010.07.056 doi: 10.1016/j.watres.2010.07.056]</ref>. A mixed culture grown on propane also degraded NDMA to < 10 ng/L<ref name= "Weidhaas2012"/>.
  
==Windrow Composting==
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NDMA impacted groundwater has been successfully treated in full-scale biological fluidized bed reactors (BFBR)<ref name= "Hatzinger2017">Hatzinger, P.B., Lewis, C. and Webster, T.S., 2017. Biological treatment of N-nitrosodimethylamine (NDMA) and N-nitrodimethylamine (NTDMA) in a field-scale fluidized bed bioreactor. Water Research, 126, pp.361-371. [https://doi.org/10.1016/j.watres.2017.09.040 doi: 10.1016/j.watres.2017.09.040]</ref>. Full-scale BFBRs are currently used for treatment of nitrate, perchlorate, selenium, volatile organic compounds (VOCs), and chlorinated solvents<ref>Hatzinger, P.B., 2005.  Perchlorate biodegradation for water treatment.  Environ. Sci. Technol., 2005, 39 (11), pp 239A–247A [https://doi.org/10.1021/es053280x doi: 10.1021/es053280x]</ref><ref>Sutton, P.M. and Mishra, P.N., 1994. Activated carbon based biological fluidized beds for contaminated water and wastewater treatment: a state-of-the-art review. Water Science and Technology, 29(10-11), pp.309-317. [https://doi.org/10.2166/wst.1994.0774 doi: 10.2166/wst.1994.0774]</ref><ref name= "Webser2009">Webster, T.S., Guarini, W.J. and Wong, H.S., 2009. Fluidized bed bioreactor treatment of perchlorate–laden groundwater to potable standards. Journal‐American Water Works Association, 101(5), pp.137-151. [https://doi.org/10.1002/j.1551-8833.2009.tb09896.x doi: 10.1002/j.1551-8833.2009.tb09896.x]</ref>. Fluidized bed reactors have also been utilized in California as part of a drinking water treatment system<ref name= "Webser2009"/><ref>Webster, T.S. and Litchfield, M.H., 2017. Full‐Scale Biological Treatment of Nitrate and Perchlorate for Potable Water Production. Journal‐American Water Works Association, 109(5), pp.30-40. [https://doi.org/10.5942/jawwa.2017.109.0065 doi: 0.5942/jawwa.2017.109.0065]</ref>.  
Based on the results of these treatability studies, [https://en.wikipedia.org/wiki/Windrow windrow] composting was selected as the preferred technology for treatment of 15,000 tons of explosives contaminated soils from a washout lagoon at Umatilla Army Depot, in lieu of incineration (Figure 2<ref name= "Emery1997">Emery, D.D. and Faessler, P.C., 1997. First production‐level bioremediation of explosives‐contaminated soil in the United States. Annals of the New York Academy of Sciences, 829(1), pp.326-340. [https://doi.org/10.1111/j.1749-6632.1997.tb48586.x doi: 10.1111/j.1749-6632.1997.tb48586.x]</ref>). Composting has been used to treat explosives contaminated soils at 10 additional Army Ammunition Plants (AAPs), Army Depots, and Naval Ammunition Depots (NADs) in the U.S. for soil quantities ranging from 1,000 cubic yards to greater than 200,000 cubic yards<ref name= "Jerger2000">Jerger, D.E. and Woodhull, P., 2000. Applications and costs for biological treatment of explosives-contaminated soils in the US. Biodegradation of nitroaromatic compounds and explosives. Lewis Publishers, BocaRaton, Fla, pp.395-423. [https://doi.org/10.1201/9781420032673 doi: 10.1201/9781420032673]</ref>. Fifteen additional sites have soil explosives contamination quantities ranging from 1,000 cubic yards to 55,000 cubic yards<ref name= "Jerger2000"/>. 
 
  
[[File:Craig1w2 Fig2.png|thumb|400 px|Figure 2. Key steps of windrow composting process at UMDA including: excavation of contaminated soil to 15 feet below ground surface (left), loading windrow machine with soil and amendments (middle), and periodically turning the windrows (right).]]
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At a former rocket test site, a BFBR was operated at a fluidization flow of ~ 9 liters per minute (LPM) and received propane, oxygen, and inorganic nutrients in the feed, along with an influent concentration of ~1,000 ng/L NDMA (Fig. 2).  At an average hydraulic residence time (HRT) of 10 min, NDMA was reduced to less than 10 ng/L.  At a 20 min HRT, NDMA was reduced to below the site discharge limit of 4.2 ng/L. The BFBR system is highly resilient to upsets by trace co-contaminants such as trichloroethene (TCE) and Freon 11<ref name= "Hatzinger2017"/>.
  
[[File:Craig1w2 Fig3.png|thumb|400 px|Figure 3. Windrow Turner at Plum Brook Ordinance Works<ref name= "ACOE2011"/>.]]
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''In situ'' propane amendment (Fig. 3) was also effective for treating NDMA in groundwater at the Aerojet Superfund Site in Rancho Cordova, CA. The propane biosparging demonstration (Fig. 4) was conducted downgradient of the liquid rocket engine test area where NDMA concentrations in groundwater ranged from 2,000 to 30,000 ng/L.  The propane and air biosparging system removed 99.7 % to > 99.9 % of the initial NDMA to levels as low 3 ng/L. Propane biosparging systems are expected to be less expensive to install and operate than conventional pump-and-treat systems<ref name= "Hatzinger2015"/>.
 
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Implementation issues include amendment selection to promote thermophilic conditions, moisture control in the windrows to maintain optimal moisture levels, and frequency of windrow turning to optimize solid phase mixing, oxygen levels, temperature control, and explosives degradation kinetics  (see Figure 4)<ref>AEC, 1993. Technology applications analysis: Windrow composting of explosives contaminated soils at Umatilla Army Depot Activity. [[media:1993-AEC_Technology_Applicatons_Analysis.pdf| Report.pdf]]</ref><ref name= "Emery1997"/><ref name= "ACOE2011"/>.
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==Summary==
 
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N-Nitrosodimethylamine (NDMA) is a suspected human carcinogen often found in tobacco and in certain foods including cured meats, smoked fish and some cheeses. While not commercially manufactured, NDMA can occur when water is disinfected with chloramine or from industrial and military sources. NDMA does not readily volatilize, sorb to solid material, or biodegrade so it is mobile in groundwater. While NDMA can be degraded to low levels with ultraviolet radiation (UV), energy costs are high. Cometabolic biological treatment is an emerging technology that has been demonstrated to be effective for both above ground and ''in situ'' treatment of NDMA.  
[[File:Craig1w2 Fig4.png|thumb|400 px|Figure 4. Degradation kinetics of three munitions contaminants in two UMDA windrows (modified from: Weston, 1993<ref name= "Weston1993"/>). ]]
 
 
 
Composting consumes approximately 1 gallon of water per cubic yard per day during the active treatment phase, and water must be added throughout the treatment process to maintain optimal moisture levels.  The median degradation for explosives composting at 10 sites was 99.7% and unit cost for composting treatment was $281 per cubic yard<ref name= "USEPA2002APC"/>, which was approximately 50% lower than the estimated costs for on-site incineration treatment.
 
 
 
==Advantages and Limitations==
 
The primary advantages associated with windrow composting include:
 
*Degradation of explosive compounds is more rapid and efficient than that achieved with static piles or slurry phase biotreatment,
 
*End product can be humus-rich compost appropriate for reuse and re-vegetation,
 
*A wide range of soil types can be treated through addition and mixing of compost bulking agents and amendments, and
 
*The treatment process is self-heating, therefore can operate year round without external heating.
 
The primary limitations associated with composting include:
 
*Space requirements can be moderate based on soil staging and treatment building footprints,
 
*Volume of final material can increase due to addition of amendments and bulking agents,
 
*Process may be susceptible to heavy metal concentrations, and
 
*The contaminated soil in the compost mix is limited to approximately 30% by volume to achieve self-heating thermophilic conditions<ref name= "USEPA2002APC"/>.
 
 
 
==Technology Cost Drivers==  
 
Factors that drive the cost of composting include:
 
*Composting is less land intensive than land treatment, but still requires a moderate treatment footprint.
 
*Batch treatment size will impact the number of batches required - windrow widths and heights are limited by the size of the turning machinery and windrow lengths by the size of the buildings used.
 
*Volatile emissions, primarily ammonia, may require venting.
 
*Soils with low porosity may require bulking agents to increase the airflow through the compost pile.
 
*Soil screening may be required to remove large rocks, debris, or other oversize materials.  
 
*Composting may require nutrient amendments to optimize C/N ratios and water, in addition to bulking agents.
 
*O&M considerations include turnover frequency, moisture levels, nutrient levels, and use of bulking agents, such as wood chips or sawdust, to maintain optimum conditions for degradation.
 
*The need for containment structures also affects treatment costs. Windrow composting has typically been conducted using open windrows in arid climates (see Figure 3), but enclosed structures in temperate and northern climates.
 
  
 
==References==
 
==References==
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==See Also==
 
==See Also==
*[[media: 2018-UFGS_for_Bioremediation_of_Soils_using_Windrow_Composting.pdf| Unified Facilities Guide Specifications for Bioremediation of Soils using Windrow Composting]]
 

Revision as of 17:54, 11 February 2019

N-Nitr2017osodimethylamine (NDMA) is a suspected human carcinogen that can enter water supplies from some military and industrial sources. NDMA is mobile in water, does not strongly sorb to solids or volatilize, and does not easily biodegrade. However, recent work has shown that NDMA can be effectively treated in both above ground and in situ cometabolic biological treatment systems.

Related Article(s):


CONTRIBUTOR(S): Paul Hatzinger

Key Resource(s):

Introduction

N-Nitrosodimethylamine (NDMA) is a suspected human carcinogen that has traditionally been detected in specific food products, such as cured meats (e.g., cold cuts preserved with nitrite), smoked fish, and some cheeses as well as chewing and smoking tobacco. NDMA is not commercially manufactured, but potential industrial sources include byproducts from rubber tire manufacturing, tanneries, some pesticide and dye plants, and fish processing facilities. NDMA has also been detected in groundwater at several military and aerospace sites involved in the production, testing, and/or disposal of liquid rocket propellants formulated with 1,1-dimethylhydrazine (1,1-DMH or UDMH). It is also frequently reported at ng/L concentrations in water and wastewater that has been disinfected with chloramine[2].

Figure 1. NDMA chemical structure

No Federal Maximum Contaminant Level (MCL) has been promulgated for NDMA in drinking water because it was historically thought to be an issue associated primarily with foods and tobacco, but NDMA and other nitrosamines were added by USEPA to both the Unregulated Contaminant Monitoring Rule-2 (UCMR-2) and Contaminant Candidate List-3 (CCL3). UCMR-2 requires many large water utilities to sample for the compound, and CCL3 provides a potential basis for contaminant regulation under the Safe Drinking Water Act (SDWA) based on occurrence and potential risk to the public.

Among the states, California has established a public health goal of 3 ng/L and Massachusetts has set a regulatory standard of 10 ng/L in drinking water. These stringent requirements reflect the carcinogenicity of NDMA which, based on USEPA risk assessments, poses an increased cancer risk of one cancer per million at a drinking water concentration of only 0.7 ng/L[3].

Physical and Chemical Properties

NDMA, in its pure form, is a yellow liquid with a density of 1.0059 g/ml and molecular weight of 74.1 g/mol[3]. It is miscible in water, relatively non-volatile and sorbs poorly to organic carbon, allowing it to readily migrate with groundwater. While NDMA is susceptible to photolysis, it is relatively recalcitrant in groundwater under both oxic and anoxic conditions, and forms large plumes at sites with concentrated sources (e.g., rocket motor test sites).

Remediation

Figure 2. Field-Scale Propane-Fed FBR.
Figure 3. Layout of biosparging system[1].
Figure 4. Field-Scale "In Situ" Propane Biosparging System

NDMA is typically removed from groundwater by extracting the contaminated groundwater followed by surface treatment with ultraviolet radiation (UV). NDMA decomposes in UV light in the 225 - 250 nm wavelength range. The primary products are dimethylamine and nitrite[4]. UV treatment can reduce NDMA concentrations to low ng/L levels, but is expensive due to the high energy input required. In potable water treatment systems, the UV dosage for NDMA removal can be a factor of ten greater than the dosage required to achieve equivalent virus removal[2].

Cometabolic biological treatment is an emerging technology for above ground and in situ treatment of NDMA. A variety of propane-oxidizing bacteria (propanotrophs) are capable of degrading NDMA[5][6][7]. When fed propane, these organisms produce a broad specificity monooxygenase enzyme (propane monooxygenase; PrMO) that cometabolically transforms NDMA producing methylamine, nitric oxide, nitrite, nitrate, and formate. A major advantage of cometabolic degradation is that the microorganisms grow on the primary substrate (propane) allowing NDMA to be reduced to ultra-low concentrations. For example, the bacterium Rhodococcus ruber ENV425 degraded NDMA from concentrations as high as 80 g/L to < 10 ng/L in batch culture[6], and in a membrane bioreactor[8]. A mixed culture grown on propane also degraded NDMA to < 10 ng/L[7].

NDMA impacted groundwater has been successfully treated in full-scale biological fluidized bed reactors (BFBR)[9]. Full-scale BFBRs are currently used for treatment of nitrate, perchlorate, selenium, volatile organic compounds (VOCs), and chlorinated solvents[10][11][12]. Fluidized bed reactors have also been utilized in California as part of a drinking water treatment system[12][13].

At a former rocket test site, a BFBR was operated at a fluidization flow of ~ 9 liters per minute (LPM) and received propane, oxygen, and inorganic nutrients in the feed, along with an influent concentration of ~1,000 ng/L NDMA (Fig. 2). At an average hydraulic residence time (HRT) of 10 min, NDMA was reduced to less than 10 ng/L. At a 20 min HRT, NDMA was reduced to below the site discharge limit of 4.2 ng/L. The BFBR system is highly resilient to upsets by trace co-contaminants such as trichloroethene (TCE) and Freon 11[9].

In situ propane amendment (Fig. 3) was also effective for treating NDMA in groundwater at the Aerojet Superfund Site in Rancho Cordova, CA. The propane biosparging demonstration (Fig. 4) was conducted downgradient of the liquid rocket engine test area where NDMA concentrations in groundwater ranged from 2,000 to 30,000 ng/L. The propane and air biosparging system removed 99.7 % to > 99.9 % of the initial NDMA to levels as low 3 ng/L. Propane biosparging systems are expected to be less expensive to install and operate than conventional pump-and-treat systems[1].

Summary

N-Nitrosodimethylamine (NDMA) is a suspected human carcinogen often found in tobacco and in certain foods including cured meats, smoked fish and some cheeses. While not commercially manufactured, NDMA can occur when water is disinfected with chloramine or from industrial and military sources. NDMA does not readily volatilize, sorb to solid material, or biodegrade so it is mobile in groundwater. While NDMA can be degraded to low levels with ultraviolet radiation (UV), energy costs are high. Cometabolic biological treatment is an emerging technology that has been demonstrated to be effective for both above ground and in situ treatment of NDMA.

References

  1. ^ 1.0 1.1 1.2 Hatzinger, P.B. and Lippincott, D., 2015. Field Demonstration of Propane Biosparging for In Situ Remediation of N-Nitrosodimethylamine (NDMA) in Groundwater. ESTCP Project ER-200828 Report.pdf
  2. ^ 2.0 2.1 2.2 Mitch, W.A., Sharp, J.O., Trussell, R.R., Valentine, R.L., Alvarez-Cohen, L. and Sedlak, D.L., 2003. N-nitrosodimethylamine (NDMA) as a drinking water contaminant: a review. Environmental Engineering Science, 20(5), pp.389-404. doi: 10.1089/109287503768335896
  3. ^ 3.0 3.1 USEPA. 2014. Technical Fact Sheet - N-Nitroso-dimethylamine. USEPA Office of Solid Waste and Emergency Response. EPA 505-F-14-005 Report.pdf
  4. ^ Stefan, M.I. and Bolton, J.R., 2002. UV direct photolysis of N‐nitrosodimethylamine (NDMA): Kinetic and product study. Helvetica Chimica Acta, 85(5), pp.1416-1426. <1416::AID-HLCA1416>3.0.CO;2-I doi: 10.1002/1522-2675(200205)85:5<1416::AID-HLCA1416>3.0.CO;2-I
  5. ^ Sharp, J.O., Sales, C.M., LeBlanc, J.C., Liu, J., Wood, T.K., Eltis, L.D., Mohn, W.W. and Alvarez-Cohen, L., 2007. An inducible propane monooxygenase is responsible for N-nitrosodimethylamine degradation by Rhodococcus sp. strain RHA1. Applied and Environmental Microbiology, 73(21), pp.6930-6938. doi: 10.1128/AEM.01697-07
  6. ^ 6.0 6.1 Fournier, D., Hawari, J., Halasz, A., Streger, S.H., McClay, K.R., Masuda, H. and Hatzinger, P.B., 2009. Aerobic biodegradation of N-nitrosodimethylamine by the propanotroph Rhodococcus ruber ENV425. Applied and environmental microbiology, 75(15), pp.5088-5093. doi: 10.1128/AEM.00418-09
  7. ^ 7.0 7.1 Weidhaas, J.L., Zigmond, M.J. and Dupont, R.R., 2012. Aerobic biotransformation of N-nitrosodimethylamine and N-nitrodimethylamine by benzene-, butane-, methane-, propane-, and toluene-fed cultures. Bioremediation Journal, 16(2), pp.74-85. doi: 10.1080/10889868.2012.665961
  8. ^ Hatzinger, P.B., Condee, C., McClay, K.R. and Togna, A.P., 2011. Aerobic treatment of N-nitrosodimethylamine in a propane-fed membrane bioreactor. Water research, 45(1), pp.254-262. doi: 10.1016/j.watres.2010.07.056
  9. ^ 9.0 9.1 Hatzinger, P.B., Lewis, C. and Webster, T.S., 2017. Biological treatment of N-nitrosodimethylamine (NDMA) and N-nitrodimethylamine (NTDMA) in a field-scale fluidized bed bioreactor. Water Research, 126, pp.361-371. doi: 10.1016/j.watres.2017.09.040
  10. ^ Hatzinger, P.B., 2005. Perchlorate biodegradation for water treatment. Environ. Sci. Technol., 2005, 39 (11), pp 239A–247A doi: 10.1021/es053280x
  11. ^ Sutton, P.M. and Mishra, P.N., 1994. Activated carbon based biological fluidized beds for contaminated water and wastewater treatment: a state-of-the-art review. Water Science and Technology, 29(10-11), pp.309-317. doi: 10.2166/wst.1994.0774
  12. ^ 12.0 12.1 Webster, T.S., Guarini, W.J. and Wong, H.S., 2009. Fluidized bed bioreactor treatment of perchlorate–laden groundwater to potable standards. Journal‐American Water Works Association, 101(5), pp.137-151. doi: 10.1002/j.1551-8833.2009.tb09896.x
  13. ^ Webster, T.S. and Litchfield, M.H., 2017. Full‐Scale Biological Treatment of Nitrate and Perchlorate for Potable Water Production. Journal‐American Water Works Association, 109(5), pp.30-40. doi: 0.5942/jawwa.2017.109.0065

See Also