10    STABILIZATION OF A THERMALLY SENSITIVE
NLTRO-COMPOUND WASTE
Keith B. Adams, Principal Process Engineer
Environmental Technology Department
Chemicals Division
Air Products and Chemicals, Inc.
Allentown, Pennsylvania 18105
INTRODUCTION
The manufacture of dinitrotoluene (DNT) and toluenediamine (TDA) generates wastewater specifically listed in April 1986 as RCRA hazardous wastes, EPA waste numbers Kill and Kl 12.' A clay-
lined surface impoundment was used for wastewater prior to biological treatment. Impending RCRA
requirements for surface impoundments2 dictated modification of the manufacturing process to
eliminate this impoundment. To satisfy RCRA closure standards, approximately 1,500 yd3 of sludge
had to be removed from the impoundment bottom and disposed of in accordance with hazardous
waste regulations. Preliminary samples of this sludge failed the EPA standard free-liquid test, disqualifying the waste from bulk landfill disposal.3 A technique was sought to stabilize the free-liquid
content of this waste to allow disposal in a Class 1 hazardous waste landfill. This objective was
complicated by the potential thermal and friction sensitivities of the nitroaromatic components in the
sludge's organic phase. As such, the stabilization process development proceeded through several
phases and used unique methodology to assess and mitigate the organic decomposition sensitivity risk.
STABILIZATION PROCESS CRITERIA
The large volume of sludge necessitated a bulk disposal method. The approach undertaken was
development of a stabilization process capable of eliminating free-liquids and thereby allowing bulk
landfill disposal.
The principal performance criteria for the process were:
• Free liquid stabilization must be a chemical reaction, not a physical attraction (i.e., not
absorption or adsorption) and stabilizing agent must be non-biodegradable.4
• Stabilization must be performed using conventional solid mixing technology, minimize
the volume increase of waste product, and minimize fugitive dust and volatile emissions
during processing.
• The stabilization process and stabilized waste product must receive appropriate approval
from state regulatory agencies.
WASTE CHARACTERIZATION
The first step in identifying suitable waste treatment processes is a characterization of the physical
and chemical properties of the waste. Due to the known nitro-compound content, the characterization
of thermal sensitivity was warranted in this case as well.
The physical properties of the waste which impact stabilization process development are: 1) free
liquid content; 2) consistency and thixotropic nature; 3) bulk density; and 4) maximum solids size.5
Chemical characterization of the waste addressed both the generic and specific waste constituent
concentrations. Analysis for percent ash and percent total moisture estimated by difference, the
percent total organics. Acidity was estimated by aqueous extract pH. Solvent extraction and subsequent gas and liquid chromatographic analyses were used to determine the concentrations of specific
nitroaromatic species. In this manner, the organic fraction could be described by the composite
chemical and thermal characteristics of the pure constituent compounds. Non-proprietary results of
the physical and chemical characterization of the surface impoundment sludge is summarized in
Table I.