High-hazard waste, definition

In many respects, the system for classifying and managing hazardous chemical waste under RCRA makes no distinction between highly hazardous waste and virtually innocuous waste that contains very low levels of hazardous substances. Furthermore, many wastes that contain hazardous chemicals, as well as radionuclides not regulated under AEA, are excluded from the definition of hazardous waste based on the source of the waste, even though the excluded wastes can be just as hazardous as other wastes that are deemed hazardous under RCRA. 

The basic definitions of exempt, low-hazard, and high-hazard waste shown in Figure 6.1 are considered in the following sections. Recommendations on approaches to calculating the risk from waste disposal in the numerator of the risk index and recommendations on specifying allowable risks in the denominator of the risk index for the purpose of classifying waste are discussed in Section 6.3. 

HAZARDOUS WASTE An Unofficial class of industrial wastes which have to be disposed of with particular care. In the UK the closest definition is for special wastes . Certain toxic organic wastes, such as PCBs, have to be burned in high-temperature incinerators. 

Potential environmental hazards from wastewater sludges are associated with trace constituents (e.g., chlorinated organic compounds) that partition from the effluent into the sludge. It should be noted, however, that recent trends away from elemental chlorine bleaching have reduced these hazards. A continuing concern is the very high pH (>12.5) of most residual wastes. When these wastes are disposed of in an aqueous form, they may meet the RCRA definition of a corrosive hazardous waste.24... 

The Subpart O standards apply to units that treat or destroy hazardous waste and which meet the definition of an incinerator. An incinerator is any enclosed device that uses controlled flame combustion and does not meet the criteria for classification as a boiler, sludge dryer, carbon regeneration unit, or industrial furnace. Typical incinerators1 2 3 include rotary kilns, liquid injectors, fixed hearth units, and fluidized bed incinerators (Table 23.1). The definition of an incinerator also includes units that meet the definition of an infrared incinerator or plasma arc incinerator. An infrared incinerator is any enclosed device that uses electric-powered resistance as a source of heat and which is not listed as an industrial furnace. A plasma arc incinerator is any enclosed device that uses a high-intensity electrical discharge as a source of heat and which is not listed as an industrial furnace. 

Another important feature of the classification system for nuclear fuel-cycle wastes in the United States is the definition of low-level waste only by exclusion there is no definition of what low-level waste is, only a definition of what it is not. As a result, in contrast to the earliest descriptions of low-level waste prior to the establishment of definitions in law, this class is not restricted to waste that contains relatively low concentrations of radionuclides compared with high-level waste. Rather, low-level waste can range from virtually innocuous to highly hazardous over long time frames. 

Some wastes are defined by exclusion (i.e., by what they are not), not on the basis of their properties or associated risks. Low-level radioactive waste is defined as waste that is not high-level waste, spent fuel, transuranic waste, or uranium or thorium mill tailings. Because the excluded wastes are defined by their source, rather than their properties, the definition of low-level waste is not based on properties of the waste and wastes in this class can vary from essentially innocuous to highly hazardous over long time frames. 

Given the qualitative definitions of the three waste classes, the boundaries of the waste classes would be quantified based on explicit descriptions of how the definitions are related to risk. The boundaries would be expressed in terms of limits on amounts (concentrations) of individual hazardous substances, with specified rules for how to classify waste that contains mixtures of hazardous substances, such as the sum-of-fractions rule for mixtures of substances that induce stochastic effects. Specifically, waste would be classified as exempt if the risk that arises from disposal in a municipal/industrial landfill for nonhazardous waste does not exceed negligible (de minimis) levels. Use of a negligible risk to quantify limits on concentrations of hazardous substances in exempt waste is appropriate because the waste would be managed in all respects as if it were nonhazardous. Nonexempt waste would be classified as low-hazard if the risk that arises from disposal in a dedicated near-surface facility for hazardous wastes does not exceed acceptable (barely tolerable) levels. An essential condition of the definitions of exempt and low-hazard waste is that an acceptable (barely tolerable) risk must be substantially greater than a negligible risk. Waste would be classified as high-hazard if it would pose an unacceptable (de manifestis) risk when placed in a dedicated near-surface facility for hazardous wastes. 

Hazardous wastes from military operations represent potential contaminants of air, water, and soil. For example, groundwater was contaminated with trichloroethylene (TCE), a probable human carcinogen, and other toxins at the Otis Air Force Base in Massachusetts 125 chemicals were dumped over 30 years at the Rocky Mountain Arsenal in Colorado and benzene, a definite human carcinogen, was found in extremely high concentrations at the McChord Air Force Base in the State of Washington [20]. 

Quantities of hazardous wastes produced each year are not known with certainty and depend on the definitions used for such materials. In the United States, there are around 17,000 RCRA-regulated sites that generate approximately 30 million tons of wastes. However, most of this material is water, with only a few million tons consisting of solids. Some high-water-content wastes are generated directly by processes that require large quantities of water in waste treatment, and other aqueous wastes are produced by mixing hazardous wastes with wastewater. 

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