Characteristic wastes

One common practice is to treat the desulfurization slag with water (Stolzenburg, ec al., 1985). This is done to generate and release acetylene gas from the unreacted calcium carbide. The other major reaction product is solid calcium hydroxide or lime. 

Calcium carbide desulfurization slag has a distinctive odor. Since pure acetylene is odorless, the odor must be produced by other trace constituents in the off-gases. A calcium carbide desulfurization slag sample from one ductile foundry was treated with water at a 1 1 solid-to-liquid ratio, and the gas was collected in a Tedlar bag for analysis by GC-MS. Several trace gases were identified, including arsine, divinyl sulfide (CHj-CH S, ethanethiol (ethyl mercaptan), methane, phosphine, and carbon monoxide. 

The sum of measured volumes of these gases represented less than 1 percent of the total gas volume generated. However, the solubility of these gases in the reaction water was not accounted for. Any one of these gases (except methane and carbon monoxide), or a combination of them, could contribute to the observed odor. Furthermore, the reaction of the slag with water may give rise to potential health hazards if workers are exposed to excessive concentrations of these gases. 

All three gases are of particular concern for human health reasons. The TLV (8-hour average) for carbon monoxide is 5.5 mg/M, and the National Ambient Air Quality Standard (NAAQS) is 10 mg/M. No standard for divinyl sulfide has been established in the United States. However, in the Soviet Union, where toxicological research on laboratory animals indicates that divinyl sulfide is a central nervous system depressant (Trofimov and Amosova, 1984), a maximum allowable concentration (MAC) of 0.2 mg/M has been recommended (Glukharev, et al., 1980).  

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A sohd waste is considered hazardous if it is either a Hsted waste or a characteristic waste. Listed wastes include a Hst of specific processes that generate a waste and a Hst of discarded commercial chemical products. There are four hazardous waste characteristics ignitabiHty, corrosivity, reactivity, and toxicity. The last refers to the leachabiHty of a waste and the resultant toxicity in the groundwater using the analytical method referred to as toxicity characteristic leaching procedure (TCLP). A Hst of substances included under TCLP is shown in Table 1. 

Factors Affecting Performance. There are many factors that affect both the choice of a particular thermal treatment and its performance. Chief among these are waste characteristics, temperature, residence time, mixing or turbulence, and air supply. 

Much of the experience and data from wastewater treatment has been gained from municipal treatment plants. Industrial liquid wastes are similar to wastewater but differ in significant ways. Thus, typical design parameters and standards developed for municipal wastewater operations must not be blindly utilized for industrial wastewater. It is best to run laboratory and small pilot tests with the specific industrial wastewater as part of the design process. It is most important to understand the temporal variations in industrial wastewater strength, flow, and waste components and their effect on the performance of various treatment processes. Industry personnel in an effort to reduce cost often neglect laboratory and pilot studies and depend on waste characteristics from similar plants. This strategy often results in failure, delay, and increased costs. Careful studies on the actual waste at a plant site cannot be overemphasized. 

In the United States, the Resource Conservation and Recovery Act of 1976 (RCRA) is the major legislation covering the disposal of solid and hazardous wastes (2). This act provides a multifaceted approach to solving the problems associated with the generation of approximately 5 billion metric tons of solid waste each year in the United States. It places particular emphasis on the regulation of hazardous wastes. This law established the Office of Solid Waste within the Environmental Protection Agency and directed the agency to publish hazardous waste characteristics and criteria. 

Bench- or pilot-scale studies are necessary to demonstrate the ability of a technology to effectively treat a specific waste. Waste characteristics vary from site to site and because of this, the effect of a treatment technology with that particular waste may not be known, given the site-specific factors and conditions. Also, the proposed treatment technology may be new or unproven. 

Identification of waste characteristics that limit the effectiveness or feasibility of technologies is an important part of the screening process. Technologies clearly limited by these waste characteristics should be eliminated from consideration. Waste characteristics particularly affect the feasibility of on-site methods, direct treatment methods, and land disposal (on/off-site). 

As a first step in the selection process, the applicability of the various solidification/ stabilization processes for specific contaminants can be determined using Table 12. Since these waste treatment systems vary widely in their applicability, cost, and pretreatment requirements, many are limited as to the types of waste that can be economically processed. Waste characteristics such as organic content, inorganic content, viscosity and... 

A variation for one vendor is shown in Figure 26. The design and control of the system takes into consideration the following parameters flow rate, water temperature, waste characteristics, chemical pretreatment options, solids loading, hydraulic loading, the air to solids ratio. Units are designed on the basis of peak flow rate expected. 

Table 9.2 lists the unit operations associated with each of the seven industry subcategories (raw waste characteristics). Common metals are found in the raw waste of all 44 unit operations. Precious metals are found in only seven unit operations complexed metals are found in three unit operations hexavalent chromium is found in seven unit operations and cyanide is found in eight unit operations. Within the organics, oils are found in 22 unit operations and solvents are found in nine unit operations. A unit operation will often be found in more than one subcategory. 

Residues from the combustion of hazardous waste are also potentially subject to RCRA regulation. If a combustion unit bums a listed hazardous waste, the ash could also be considered a listed waste via the derived-from rule. The owner and operator must also determine whether this ash exhibits any hazardous waste characteristics. The same is true if a unit bums waste that only exhibits a characteristic. Ash that exhibits a characteristic must be managed as a hazardous waste. 

Mineral processing spent materials. Mineral processing generates spent materials that may exhibit hazardous waste characteristics. Common industry practice is to recycle these mineral processing wastes back into the processing operations to recover mineral value. U.S. EPA created a conditional exclusion from the definition of solid waste for these spent materials when recycled in the mineral processing industry, provided the materials are stored in certain types of units and are not accumulated speculatively. 

A hazardous waste characteristic is a property that indicates that a waste poses a sufficient threat to deserve regulation as hazardous. U.S. EPA tried to identify characteristics that, when present in a waste, can cause death or illness in humans or ecological damage. U.S. EPA also decided that the presence of any characteristic of hazardous waste should be detectable by using a standardized test... 

The mixture and derived-from rules apply differently to listed and characteristic wastes. A mixture involving characteristic wastes is hazardous only if the mixture itself exhibits a characteristic. Similarly, treatment residues and materials derived from characteristic wastes are hazardous only if they themselves exhibit a characteristic. Unlike listed hazardous wastes, characteristic wastes are hazardous because they possess one of four unique and measurable properties. U.S. EPA decided that once a characteristic waste no longer exhibits one of these four dangerous properties, it no longer deserves regulation as hazardous. Thus, a characteristic waste can be made nonhazardous by treating it to remove its hazardous property however, U.S. EPA places certain restrictions on the manner in which a waste can be treated. One can learn more about these restrictions in the U.S. EPA Land Disposal Restrictions Module Handlers who render characteristic wastes nonhazardous must consider these restrictions when treating wastes to remove their hazardous properties. 

There are eight exemptions from the mixture rule. The first exemption from the mixture rule applies to mixtures of characteristic wastes and specific mining wastes excluded under RCRA. This narrow exemption allows certain mixtures to qualify as nonhazardous wastes, even if the mixtures exhibit one or more hazardous waste characteristics. The mining waste exclusion is explained in more detail in a U.S. EPA module.9... 

The hazardous waste listings, the hazardous waste characteristics, and the mixture and derived-from rules are all essential parts of the definition of hazardous waste, but these key elements are all described in different sections of the RCRA regulations. Only one regulatory section unites all four elements to establish the formal definition of hazardous waste. This section is entitled Definition of Hazardous Waste, which states that all solid wastes exhibiting one of the four hazardous characteristics are hazardous wastes. This section also states that all solid wastes listed on one of the four hazardous waste lists are hazardous wastes. Finally, this section explains in detail the mixture and derived-from rules and the regulatory exemptions from these rules. Thus, although the section is entitled Definition of Hazardous Waste, it serves primarily as a guide to the mixture and derived-from rules. 

It was observed that the factors contributing to the variation of leachate data are solid waste characteristics, for example, the composition and size of the waste and degree of compaction, the moisture content and degree of rainwater infiltration, temperature, sampling, and analytical methods.47... 

The sources of contamination are usually those hazardous materials that are contained in drums, tanks, surface impoundments, waste piles, and landfills, as well as heavily contaminated media (such as soil) affected by the original leaking or spilling source. The purpose of defining sources of contamination is to help to identify the source location, potential releases, and engineering characteristics that are important in the evaluation of remedial actions, as well as waste characteristics, such as the type and quantity of contaminants that may be contained in or released to the environment, and the physical or chemical characteristics of the hazardous wastes present in the source. 

Waste characteristics, which may limit the effectiveness or feasibility of the remedial technologies quantity/concentration, chemical composition, acute toxicity, persistence, biodegradability, radioactivity, ignitability, reactivity/corrosivity, infectiousness, solubility, volatility, density, partition coefficient, compatibility with chemicals, and treatability... 

This technology is suitable for soils or sediments with organic contaminants. The optimal waste characteristics are as follows ... 

Table 20.19 summarizes information about each study, including the location of the well, the lithology of the injection zone, waste characteristics, and the major geochemical processes observed. Current commercial-hazardous-waste, deep-well-injection facilities can be found on the Environment, Health and Safety Online (EHSO) web site.163... 

Based on the anode material employed, eight (8) subdivisions (A-H) have been developed by the U.S. EPA.5 As may be noted (Table 32.1), the zinc anode is divided into two groups (subcategories D and G) based on the electrolyte types. This difference is also reflected in the substantial differences in the manufacture, as well as the waste generated by the two groups. Although a subcategory of nuclear batteries is indicated, hardly any data exist that describes its construction, leave alone the waste characteristics. Similar paucity in information exists on thermal batteries (such as calcium batteries), whose production and use are limited to few operations, especially in... 

Many refineries in the United States are being required to control whole-effluent toxicity as well as specific toxic constituents to meet new wastewater discharge limits. There can be a variety of toxic constituents that may need to be controlled, depending on waste characteristics and local water quality objectives. The more common constituents in refinery wastewater include cyanide and heavy metals. The treatment processes for control of whole-effluent toxicity, cyanide, and heavy metals are discussed below. 

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