Difference between revisions of "User:Debra Tabron/sandbox"

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Nitroaromatic and nitroamine compounds in munitions constituents are susceptible to rapid degradation under alkaline (i.e., basic, high pH) environmental conditions. Alkaline degradation of the secondary explosives TNT and RDX have been examined in laboratory-scale studies and field-scale demonstrations. Both topical and deeper soil-mixed applications of alkaline substances, such as hydrated lime and caustic soda, have successfully degraded munitions constituents in highly contaminated soils on training ranges and at formerly used defense sites (FUDS).
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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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'''CONTRIBUTOR(S):''' [[Jared Johnson]]
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'''CONTRIBUTOR(S):''' [[Harry Craig]]
  
  
 
'''Key Resource(s)''':
 
'''Key Resource(s)''':
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*[[media:2011_-_Johnson_-_Management_of_Munitions_Constituents_in_Soil.pdf | Management of Munitions Constituents in Soil Using Alkaline Hydrolysis: A Guide for Practitioners]]<ref name= "Johnson2011">Johnson, J.L., Felt, D.R., Martin, W.A., Britto, R., Nestler, C.C. and Larson, S.L., 2011. Management of munitions constituents in soil using alkaline hydrolysis: A guide for practitioners (No. ERDC/EL-TR-11-16). Vicksburg, MS: U.S. Army Engineer Research and Development Center.[[media:2011_-_Johnson_-_Management_of_Munitions_Constituents_in_Soil.pdf | Report.pdf]]</ref>
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*[[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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==Principal of Operation==
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==Overview==
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Alkaline hydrolysis reactions involve the aqueous interaction of added OH- ions with dissolved organic compounds. Degradation of nitroaromatics (i.e., TNT and DNT) is hypothesized to occur through formation of a Meisenheimer complex or TNT anion<ref>Saupe, A., Garvens, H.J. and Heinze, L., 1998. Alkaline hydrolysis of TNT and TNT in soil followed by thermal treatment of the hydrolysates. Chemosphere, 36(8), pp.1725-1744. [https://doi.org/10.1016/S0045-6535(97)10063-7 doi: 10.1016/S0045-6535(97)10063-7]</ref><ref>Salter-Blanc, A.J., Bylaska, E.J., Ritchie, J.J. and Tratnyek, P.G., 2013. Mechanisms and kinetics of alkaline hydrolysis of the energetic nitroaromatic compounds 2, 4, 6-trinitrotoluene (TNT) and 2, 4-dinitroanisole (DNAN). Environmental science & technology, 47(13), pp.6790-6798. [https://doi.org/10.1021/es304461t doi:10.1021/es304461t]</ref>. Initial denitration of nitroamines (i.e., RDX, HMX, and CL-20) by OH- is thought to cause molecular instability leading to ring cleavage, followed by spontaneous decomposition <ref>Jones, W.H., 1954. Mechanism of the Homogeneous Alkaline Decomposition of Cyclotrimethylenetrinitramine: Kinetics of Consecutive Second-and First-order Reactions. A Polarographic Analysis for Cyclotrimethylenetrinitramine1. Journal of the American Chemical Society, 76(3), pp.829-835. [https://doi.org/10.1021/ja01632a058 doi: 10.1021/ja01632a058]</ref><ref name= "Balakrishnan2003">Balakrishnan, V.K., Halasz, A. and Hawari, J., 2003. Alkaline hydrolysis of the cyclic nitramine explosives RDX, HMX, and CL-20: New insights into degradation pathways obtained by the observation of novel intermediates. Environmental Science & Technology, 37(9), pp.1838-1843. [https://doi.org/10.1021/es020959h doi: 10.1021/es020959h]</ref>. This degradation pathway is supported by observations of nitrite and formate production during the alkaline decomposition of nitramines<ref name= "Hwang2006">Hwang, S., Felt, D.R., Bouwer, E.J., Brooks, M.C., Larson, S.L. and Davis, J.L., 2006. Remediation of RDX-contaminated water using alkaline hydrolysis. Journal of Environmental Engineering, 132(2), pp.256-262. [https://doi.org/10.1061/(ASCE)0733-9372(2006)132:2(256) doi: 10.1061/(ASCE)0733-9372(2006)132:2(256)]</ref><ref name= ''Heilmann1996''>Heilmann, H.M., Wiesmann, U. and Stenstrom, M.K., 1996. Kinetics of the alkaline hydrolysis of high explosives RDX and HMX in aqueous solution and adsorbed to activated carbon. Environmental Science & Technology, 30(5), pp.1485-1492. [https://doi.org/10.1021/es9504101 doi: 10.1021/es9504101]</ref>.  
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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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The terminal degradation products of alkaline hydrolysis are commonly formate, formaldehyde, nitrate, nitrite, and nitrous oxide. At pH greater than 11, TNT degrades readily to formate and nitrate, but at lower pH it tends to polymerize<ref>Felt, D.R., Nestler, C.C., Davis, J.L. and Larson, S.L., 2007. Potential for biodegradation of the alkaline hydrolysis end products of TNT and RDX (No. ERDC/EL-TR-07-25). Engineer Research and Development Center Vicksburg, MS. [[media:2001-Felt-_Potential_for_biodegradatio_of_the_alkaline_hydrolysis.pdf| Report.pdf]]</ref>.  
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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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Propellant residues have been studied less than secondary explosives, but studies have shown the insoluble nitrocellulose matrix in some propellants to be rendered biodegradable under alkaline conditions<ref>Kenyon, W.O. and Gray, H.L., 1936. The Alkaline Decomposition of Cellulose Nitrate. I. Quantitative Studies1. Journal of The American Chemical Society, 58(8), pp.1422-1427. [https://doi.org/10.1021/ja01299a034 doi: 10.1021/ja01299a034]</ref><ref>Kim, B.J., Alleman, J.E. and Quivey, D.M., 1998. Alkaline hydrolysis/biodegradation of nitrocellulose fines (No. CERL-TR-98/65). Consstruction Engineering Researcg Lab (ARMY) Champaign, IL.[[media:1998-Kim-Alkline_Hydrolysis_Biodegradation_of_Nitrocellulose_Fines.pdf| Report.pdf]]</ref>. Ultimately, alkaline material is neutralized over time by the natural buffering capacity of soil.
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==Principle of Operation==
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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>.  
  
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==Aqueous Kinetics==
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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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Degradation rates by alkaline hydrolysis for major secondary explosive compounds in aqueous systems have been measured under a range of pHs and temperatures (Table 1). Reported half-lives of TNT ranged from about 2-6 hours at pH 12 to up to six days at pH 11 in stirred aqueous reactors<ref name= ''Emmrich1999''>Emmrich, M., 1999. Kinetics of the alkaline hydrolysis of 2, 4, 6-trinitrotoluene in aqueous solution and highly contaminated soils. Environmental Science & Technology, 33(21), pp.3802-3805. [https://doi.org/10.1021/es9903227  doi: 10.1021/es9903227]</ref><ref name= "Hwang2005">Hwang, S., Ruff, T.J., Bouwer, E.J., Larson, S.L. and Davis, J.L., 2005. Applicability of alkaline hydrolysis for remediation of TNT-contaminated water. Water research, 39(18), pp.4503-4511. [https://doi.org/10.1016/j.watres.2005.09.008 doi: 10.1016/j.watres.2005.09.008]</ref>. Hydrolysis of RDX is reported to also occur with half-lives on the order of hours, with a strong dependence on temperature<ref name= ''Heilmann1996''/><ref name= "Hwang2006"/>. HMX reacted more slowly with a reaction rate two orders of magnitude slower than that observed for RDX<ref name= ''Heilmann1996''/>. Alkaline hydrolysis of the caged nitroamine CL-20 had an observed half-life of roughly one hour in pH 10 solution and on the order of minutes at higher pH<ref name= "Balakrishnan2003"/>.  
 
  
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{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none; text-align: center;"
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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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|+ <div style="text-align: center;"> Table 1.  Observed Batch Kinetics for the Alkaline Destruction of Secondary Explosive Compounds in Aqueous Systems</div>
 
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! Compound
 
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! pH
 
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! Temp<br />(&deg;C)
 
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! Pseudo 1<sup>st</sup> Order<br />Decay Constant<br />(min<sup>-1</sup>)(10<sup>-3</sup>)
 
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! Observed<br />Half-Life<br />(min)
 
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! Reference
 
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|-
 
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! rowspan="6" | TNT
 
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| 10 || 20 ||0.0 || n/a || Emmrich, 1999<ref name= ''Emmrich1999''/>
 
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|-
 
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| 11 || 20 || 0.43 || 1,600 || Emmrich, 1999<ref name= ''Emmrich1999''/>
 
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|-
 
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| 12 || 20 || 6.1 || 115 || Emmrich, 1999<ref name= ''Emmrich1999''/>
 
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|-
 
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| 11 || 25 || 0.15 || 4,621 || Hwang, et al., 2005<ref name= "Hwang2005"/>
 
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|-
 
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| 11.5 || 25 || 0.34 || 2,039 || Hwang, et al., 2005<ref name= "Hwang2005"/>
 
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|-
 
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| 11.9 || 25 || 1.1 || 630 || Hwang, et al., 2005<ref name= "Hwang2005"/>
 
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|-
 
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! rowspan="14" | RDX
 
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| 11.18 || 50 || 9.3 || 75 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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|-
 
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| 11.32 || 50 || 13 || 53 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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|-
 
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| 12 || 50 || 58.2 || 12 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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|-
 
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| 12.3 || 50 || 127.2 || 5.5 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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|-
 
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| 11 || 25 || 0.8 || 866 || Hwang, et al., 2006<ref name= "Hwang2006"/>
 
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|-
 
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| 11.5 || 25 || 1.7 || 408 || Hwang, et al., 2006<ref name= "Hwang2006"/>
 
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|-
 
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| 12 || 25 || 2.3 || 301 || Hwang, et al., 2006<ref name= "Hwang2006"/>
 
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|-
 
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| 12.2 || 25 || 7.9 || 88 || Hwang, et al., 2006<ref name= "Hwang2006"/>
 
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| 12.6 || 25 || 22.3 || 31 || Hwang, et al., 2006<ref name= "Hwang2006"/>
 
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|-
 
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| 13 || 25 || 27.7 || 25 || Hwang, et al., 2006<ref name= "Hwang2006"/>
 
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| 12 || 25 || 2.7 || 260 || Gent, et al., 2010<ref name= '' Gent2010''>Gent, D.B., Johnson, J.L., Felt, D.R., O'Connor, G., Holland, E., May, S. and Larson, S.L., 2010. Laboratory demonstration of abiotic technologies for removal of RDX from a process waste stream (No. ERDC/EL-TR-10-8). Engineer Research and Development Center Vicksburg MS Environmental Lab. [[media:2010-Gent-laboratory_Demostration_of_abiotic_tech_for_removal_of_RDX.pdf| Report.pdf]]</ref>
 
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|-
 
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| 12.5 || 25 || 8.3 || 83 || Gent, et al., 2010<ref name= '' Gent2010''/>
 
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|-
 
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| 13 || 25 || 26.8 || 26 || Gent, et al., 2010<ref name= '' Gent2010''/>
 
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|-
 
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| 13.3 || 25 || 52.3 || 13 || Gent, et al., 2010<ref name= '' Gent2010''/>
 
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|-
 
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! rowspan="3" | HMX
 
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| 10.34 || 50 || 0.09 || 7,788 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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|-
 
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| 11.32 || 50 || 0.99 || 700 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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|-
 
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| 12.36 || 50 || 1.1 || 641 || Heilmann, et al., 1996<ref name= ''Heilmann1996''/>
 
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! rowspan="4" | CL-20
 
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| 10 || 25 || 8 || 87 || Santiago, et al., 2007<ref name= "Santigo2007">Santiago, L., Felt, D.R. and Davis, J.L., 2007. Chemical Remediation of an Ordnance-Related Compound: The Alkaline Hydrolysis of CL-20. Environmental Quality Technology Program (No. ERDC/EL-TR-07-18). Engineer Research and Development Center, Vicksburg, MS Environmental Lab. [[media:2007-Santiago-chemical_remediation_of_an_ordnance_related_compound.pdf| Report.pdf]]</ref>
 
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|-
 
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| 11 || 25 || 50.3 || 14 || Santiago, et al., 2007<ref name= "Santigo2007"/>
 
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|-
 
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| 11.5 || 25 || 147.7 || 4.7 || Santiago, et al., 2007<ref name= "Santigo2007"/>
 
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|-
 
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| 12 || 25 || 858 || 0.8 || Santiago, et al., 2007<ref name= "Santigo2007"/>
 
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|}
 
  
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==Performance in Soil Systems==
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[[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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[[File:Johnson1w2 Fig1.png|thumb|right|Figure 1: RDX concentrations in leachate by rain event for meso-scale lysimeters containing hand grenade range soils as reported by Larson et al. (2007)<ref name= "Larson2007"/>]]
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==Early Development and Demonstration==
  
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Alkaline material is neutralized over time by the natural buffering capacity of the soil. Protons (H<sup>+</sup>) exchanged from low pH soils and metal cations interact with hydroxide (OH<sup>-</sup>) ions to mitigate the alkaline degradation of munitions constituents. Furthermore, hydrogen ions associated with various functional groups in humic matter may also dissociate under elevated pH conditions and likewise inhibit alkaline hydrolysis of the explosive contaminants. Soil chemistry therefore plays an important role in energetics remediation through alkaline hydrolysis.
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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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Soil microcosm studies with 5% w/w calcium hydroxide and 50% w/w water observed half-lives for TNT, RDX, and HMX on the order of a day to a week, with degradation rates following the sequence of TNT > RDX > HMX, similar to the aqueous studies. Soil slurries using 2,4-DNT and the single amino substituted TNT degradation products (4A-2,6-DNT and 2A-4,6-DNT) also exhibited day to week-long half-lives at pH 11 and 12<ref name= ''Emmrich1999''/><ref>Emmrich, M., 2001. Kinetics of the alkaline hydrolysis of important nitroaromatic co-contaminants of 2, 4, 6-trinitrotoluene in highly contaminated soils. Environmental Science & Technology, 35(5), pp.874-877. [https://doi.org/10.1021/es0014990 doi: 10.1021/es0014990 doi: 10.1021/es0014990 ]</ref>.
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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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A meso-scale soil treatability study was conducted using soils collected from two different hand grenade ranges<ref name= "Larson2007">Larson, S.L., Davis, J.L., Martin, W.A., Felt, D.R., Nestler, C.C., Brandon, D.L., Fabian, G. and O'Connor, G., 2007. Grenade Range Management Using Lime for Metals Immobilization and Explosives Transformation Treatability Study (No. ERDC/EL-TR-07-5). Vicksburg, MS: U.S. Army Engineer Research and Development Center. [[media:2007-Larson-grenade_Range_Management_Using_Lime_for_Metals_Immobilization.pdf| Report.pdf]]</ref>. These soils were treated with a well-mixed application of hydrated lime, and migration of RDX was monitored by analyzing porewater concentrations in installed lysimeters over time (Figure 1). Overall, the reduction in RDX leaving the mesocosms as both leachate and runoff was greater than 90% with application of hydrated lime. The study authors also observed that alkaline amendments were able to fix metals contamination in place on hand grenade range soils.
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==Windrow Composting==
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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"/>.
  
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==Field-Scale Performance Examples==
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[[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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===Hand Grenade Range===
 
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[[File:Johnson1w2 Fig2.png|thumb|Figure 2: Mean pore water RDX concentrations by hand grenade bay and lysimeter with maximum and  minimum concentration profiles (avg, n ranges from 7 to 10; modified from Larson et al., 2007)<ref name= "Larson2007"/>.]]
 
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Alkaline hydrolysis was successfully employed at a hand grenade range that experiences ~55,000 hand grenade detonations each year<ref name= "Larson2007"/><ref>Martin, W.A., Felt, D.R., Nestler, C.C., Fabian, G., O’Connor, G. and Larson, S.L., 2012. Hydrated Lime for Metal Immobilization and Explosives Transformation: Field Demonstration. Journal of Hazardous, Toxic, and Radioactive Waste, 17(3), pp.237-244. [https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000176 doi: 10.1061/(ASCE)HZ.2153-5515.0000176]</ref>. During this demonstration, initial soil samples were collected from individual grenade bays and lysimeters were installed to a depth of 5 feet below ground surface. Lime was applied in December, 2005, April, 2006, and January, 2007, with nine discrete sampling events occurring between December, 2005, and March, 2007. Lysimeter concentrations are shown in Figure 2 for one treated grenade bay and another untreated control bay. Based on the average pore water concentration in the treated and untreated bays over the demonstration period, there was a 77% reduction in RDX concentration in pore water from the treated bay. There is a statistically significant difference between the explosives concentration in the pore water from the untreated vs. the limed bays (P < 0.001).
 
  
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A project has been funded beginning in FY19 to re-examine liming practices at this hand grenade range and produce a report on the long term efficacy of this management technique for an active training range.
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[[File:Craig1w2 Fig3.png|thumb|400 px|Figure 3. Windrow Turner at Plum Brook Ordinance Works<ref name= "ACOE2011"/>.]]
  
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===Ammunition Plant===
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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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''Ex-situ'' alkaline hydrolysis was used at an ammunition plant to remediate surface soil (0 to 20 feet below ground surface) that had high concentrations of DNT and TNT<ref name= "Johnson2011"/>. Laboratory experiments on this soil demonstrated that target nitroaromatic compounds could be reduced to less than 10 mg/kg within a week. The only final product of note was nitrite, which could be destroyed via a denitrification process if necessary. Over a two-year period, approximately 150,000 tons of impacted soils were treated and approximately 148,000 lbs of nitroaromatic compounds destroyed, with an average contaminant mass reduction of 96 percent. Subsequent ''in-situ'' treatment was used to remediate over 15,000 additional tons of soil.
 
  
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[[File:Johnson1w2 Fig3.png|thumb|right|Figure 3: Soil mixing during ex situ alkaline treatment of soils  at an ammunition plant.]]
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[[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"/>). ]]
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The basic ''ex-situ'' treatment process involved the excavation of contaminated soil to a lined basin onsite. A typical excavation is shown in Figure 3. Caustic reagents in pellet form were added at a one to two percent weight by weight basis (depending on the starting concentrations, starting pH, and the buffering capacity) along with small quantities of metal catalyst, if needed. The soil was treated in 300 cubic yard batches, with amended chemicals thoroughly mixed into the soil using conventional equipment.  Water was added as needed to increase the moisture content to near saturation. Mixing was repeated two to three times a week and samples were collected for moisture content and pH, which are critical field monitoring and effectiveness parameters. 
 
  
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After one week, soil sampling was performed per site specific sampling protocol and analyzed for contaminants of concern, daughter products, and breakdown products.  If needed for soil with higher concentrations of explosives, caustic reagent was supplemented to maintain the pH at the 13.0 unit level.  Soil continued to be treated until TNT and DNT concentrations were below cleanup levels (57 mg/kg for TNT and 25.4 mg/kg for total DNTs).  Metals were also analyzed periodically and TCLP tests were performed per site treatment goals.  When needed on a small percentage of batches, denitrification of soil was performed to lower the nitrite end-product using citric acid as the pH reducer and carbon substrate. After complete treatment, the soil was transported back to the excavation.  ''In-situ'' treatment is performed in a similar way to ''ex-situ'' treatment using conventional equipment and prescribed quantities of chemical reagents.
+
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.
  
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Some general heuristic guidelines are summarized in Figure 4. An active firing range requires treatment technologies that have minimal soil disturbance, requiring topical application of hydrated lime for most range applications. Therefore the fate of hydroxide (OH-) ions during transport through the soil is an important aspect of this proposed remediation technology. Studies performed by the agricultural and oil industries provide evidence of the transport limitations of hydroxide ions in soils, particularly in those soils with significant clay content <ref>Breit, V.S., Mayer, E.H. and Carmichael, J.D., 1979, January. An easily applied black oil model of caustic waterflooding. In SPE California Regional Meeting. Society of Petroleum Engineers. [https://doi.org/10.2118/7999-MS doi: 10.2118/7999-MS]</ref><ref>DeZabala, E.F., Vislocky, J.M., Rubin, E. and Radke, C.J., 1982. A chemical theory for linear alkaline flooding. Society of Petroleum Engineers Journal, 22(02), pp.245-258. [https://doi.org/10.2118/8997-PA [https://doi.org/10.2118/8997-PA doi: 10.2118/8997-PA]</ref><ref>Somerton, W. H., and C. J. Radke. 1980. Roles of clays in the enhanced recovery of petroleum. Proceedings of the first joint SPE/DOE symposium on enhance oil recovery. Society of Petroleum Engineers</ref><ref>Smith, C.J., Peoples, M.B., Keerthisinghe, G., James, T.R., Garden, D.L. and Tuomi, S.S., 1994. Effect of surface applications of lime, gypsum and phosphogypsum on the alleviating of surface and subsurface acidity in a soil under pasture. Soil Research, 32(5), pp.995-1008. [https://doi.org/10.1071/SR9940995 doi: 10.1071/SR9940995]</ref>.
+
==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"/>.
  
−
[[File:Johnson1w2 Fig4.png|thumb|center|400 px|Figure 4: General heuristics for determining application of alkaline amendments for the management of munitions constituents in soil.]]
+
==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==
Line 125: Line 73:
  
 
==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 17:27, 5 February 2019

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.

Related Article(s):


CONTRIBUTOR(S): Harry Craig


Key Resource(s):

Overview

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.

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 (Mesophile) or thermophilic (Thermophile) microbial activity[2].

Principle of Operation

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[3].

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.

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.

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)[3].

Early Development and Demonstration

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[4][5].

Subsequent pilot scale treatability studies were conducted to evaluate mesophilic vs. thermophilic conditions[6][7]. A range of materials handling approaches including static piles, mechanically agitated in-vessel reactors (MAIV), and mixed aerated and nonaerated windrows[8][9] [10] 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[10][11].

Windrow Composting

Based on the results of these treatability studies, 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[12]). 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[13]. Fifteen additional sites have soil explosives contamination quantities ranging from 1,000 cubic yards to 55,000 cubic yards[13].

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).
Figure 3. Windrow Turner at Plum Brook Ordinance Works[1].

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)[14][12][1].

Figure 4. Degradation kinetics of three munitions contaminants in two UMDA windrows (modified from: Weston, 1993[10]).

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[2], 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[2].

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

  1. ^ 1.0 1.1 1.2 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. Report.pdf
  2. ^ 2.0 2.1 2.2 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). Report.pdf
  3. ^ 3.0 3.1 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. doi: 10.1201/9781420032673
  4. ^ 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. Report.pdf
  5. ^ Doyle, R.C., Isbister, J.D., Anspach, G.L. and Kitchens, J.F., 1986. Composting explosives/organics contaminated soils. Atlantic Research Corporation. Report.pdf
  6. ^ 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. doi: 10.1007/BF01569746
  7. ^ Garg, R., Grasso, D. and Hoag G., 1991. Treatment of explosives contaminated lagoon sludge. Hazardous Waste and Hazardous Materials, 8(4), pp.319-340. doi: 10.1089/hwm.1991.8.319
  8. ^ Weston, R.F. , 1988. Field demonstration - composting explosives-contaminated sediments at the Louisiana Army Ammunition Plant (LAAP). Report.pdf
  9. ^ 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. Report.pdf
  10. ^ 10.0 10.1 10.2 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. Report.pdf
  11. ^ 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. Report.pdf
  12. ^ 12.0 12.1 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. doi: 10.1111/j.1749-6632.1997.tb48586.x
  13. ^ 13.0 13.1 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. doi: 10.1201/9781420032673
  14. ^ AEC, 1993. Technology applications analysis: Windrow composting of explosives contaminated soils at Umatilla Army Depot Activity. Report.pdf

See Also

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