Detection of Aluminum Waste Reactions and Waste Fires Jeffrey W. Martin, P.G. 1 ; Timothy D. Stark, Ph.D., P.E., F.ASCE 2 ; Todd Thalhamer, P.E. 3 ; Gina T. Gerbasi-Graf 4 ; and R. Edwin Gortner 5 Abstract: Aluminum production wastes (APW) placed in Subtitle D regulated landfills may react exothermically and cause uncontrolled temperature increases, large volumes of explosive and toxic gasses, increases in landfill gas pressure and flow, intense odors, undesirable changes in leachate composition, increased leachate production, and most importantly, smoldering combustion of the surrounding solid waste. The landfill liner and explosive gas extraction and leachate collection systems can be damaged by heat from the reaction and/or accompanying combustion. Slope failure also may result from increased gas and liquid pressures and the reduction of waste mass shear strength attributable to subsurface combustion compounding existing or initiating damage to engineered components. Therefore, landfills that have received APW need early detection of a potential exothermic reaction to respond promptly to prevent subsequent subsurface combustion. This paper presents techniques to quickly evaluate landfill gas and temperature data to determine if an APW reaction is occur- ring, discusses operational indicator criteria that can be used to differentiate an APW reaction from subsurface combustion or combined reaction/combustion, and provides recommendations for APW disposal that minimize potential for a reaction to occur. DOI: 10.1061/ (ASCE)HZ.2153-5515.0000171. © 2013 American Society of Civil Engineers. CE Database subject headings: Aluminum (chemical); Combustion; Fires; Landfills; Leaching; Slope stability; Solid wastes; Waste disposal; Waste management. Author keywords: Aluminum; Combustion; Dross; Exothermic reaction; Fire; Landfill; Leachate; Leachate recirculation; Salt cake; Slope stability; Smoldering; Solid waste; Subtitle D; Waste disposal. Introduction The U.S. Department of Energy (U.S. DOE) (1999) estimated that at least one million tons (approximately 1.1 million short tons) of aluminum production wastes (APW) are placed annually in Resource Conservation and Recovery Act (R.C.R.A.) Subtitle D landfills. These waste materials contain variable amounts of alumi- num metal and aluminum compounds, such as aluminum carbide, aluminum nitride, and aluminum oxides mixed with sodium and potassium salts and other substances. Aluminum production wastes include materials commonly referred to as dross, white dross, skim dross, rich dross, black dross, and salt cake within the aluminum production industry (Graczyk et al. 1997). These terms are used to describe the aluminum metal content and morphology of the vari- ous wastes removed from the surface of molten aluminum during processing and purification (Manfredi et al. 1997; Shinzato and Hypolito 2005; Szczygielski 2008). Although APW can remain relatively dormant for years in a landfill, it may react exothermically with liquids present in or introduced into a Subtitle D landfill (Szczygielski 2008). If landfill leachate (or other water-based fluid) contacts APW for a sufficient period of time and dissolves soluble salts from the APW matrix, exothermic chemical reactions can occur. As the dissolution of salts progresses, the pH of the leachate gradually increases as it begins to react with carbides, nitrides, and metal oxides contained in the APW. Some of these reactions generate heat and toxic or flamma- ble gasses such as ammonia and acetylene. When the pH rises to approximately 9.0 or higher, hydroxyl ions in the leachate begin to react with the aluminum metal particles of the APW. This reaction is highly exothermic, rapidly releasing large amounts of heat and hydrogen gas. Internal temperatures of landfill waste masses experiencing this reaction of 88°C (170°F) to 110°C (230°F) have been observed, at which desirable microbial activity is terminated and methane production severely curtailed. These exothermic reactions and associated changes in gas composition and increased gas pressure also may cause intense odors. The sustained heat generated from this exothermic reaction can cause a subsurface waste fire by igniting the surrounding solid waste through the processes of glowing (contact) or smoldering combustion. The high temperatures generated by the exothermic reaction and exacerbated by smoldering combustion of waste materials also can cause damage to the engineered components of the landfill, e.g., gas collection, leachate collection, and liner systems (Lewicki 1999; Øygard et al. 2005), and even negatively impact slope stability (Stark et al. 2010). Additionally, landfill combustion emits air pollutants, including but not limited to 1 Environmental Specialist, Division of Environmental Response and Site Revitalization, Ohio Environmental Protection Agency, 50 West Town St., Suite 700, P.O. Box 1049, Columbus, OH 43216-1049. E-mail: jeff .martin@epa.state.oh.us 2 Professor of Civil Engineering, Univ. of Illinois–Urbana Champaign, 205 N. Mathews Ave., Urbana, IL 61801 (corresponding author). E-mail: tstark@illinois.edu 3 Lieutenant, El Dorado Hills Fire Dept. and Waste Management Engi- neer, Dept. of Resources Recycling and Recovery (CalRecycle), California Environmental Protection Agency, Sacramento, CA 95814. E-mail: todd .thalhamer@calrecycle.ca.gov 4 Enforcement Specialist, Cincinnati Health Dept., 3845 William P. Dooley By-Pass, Cincinnati, OH 45223. E-mail: gina.graf@cincinnati -oh.gov 5 Environmental Supervisor, Division of Emergency and Remedial Response, Ohio Environmental Protection Agency, Columbus, OH 43215. Note. This manuscript was submitted on May 30, 2011; approved on November 8, 2012; published online on November 10, 2012. Discussion period open until December 1, 2013; separate discussions must be submitted for individual papers. This paper is part of the Journal of Hazardous, Toxic, and Radioactive Waste, Vol. 17, No. 3, July 1, 2013. © ASCE, ISSN 2153- 5493/2013/3-164-174/$25.00. 164 / JOURNAL OF HAZARDOUS, TOXIC, AND RADIOACTIVE WASTE © ASCE / JULY 2013 J. Hazard. Toxic Radioact. Waste 2013.17:164-174. Downloaded from ascelibrary.org by GRAINGER ENGINEERING LIB E on 06/25/13. Copyright ASCE. For personal use only; all rights reserved.