Spent solvent wastes

Because chlorobenzene is listed as a hazardous substance, disposal of waste chlorobenzene is controlled by a number of federal regulations (see Chapter 7). Spent solvent wastes, which may... 

MEK is burned in a chemical incinerator equipped with an afterburner and scrubber. Land disposal concentration of MEK in wastewater should not exceed 0.05 ppm, and that in TCLP extract of spent solvent wastes,... 

Land disposal concentration in waste-water should be less than 0.05 ppm, and that in the TCLP extract of spent solvent waste should be less than 0.33 ppm waste treatment is by steam stripping (U.S. EPA 1988). 

Finally, factories must collect and segregate spent solvent waste as a separate waste stream and thus incur additional cost. These cost of ownership issues are substantially decreased through the use of aqueous, metal-ion free developers based on tetramethylammonium hydroxide which are the semiconductor industry standard for developing positive photoresists. 

Batch distillation (see Fig. 3) typically is used for small amounts of solvent wastes that are concentrated and consist of very volatile components that are easily separated from the nonvolatile fraction. Batch distillation is amenable to small quantities of spent solvents which allows these wastes to be recovered onsite. With batch distillation, the waste is placed in the unit and volatile components are vaporized by applying heat through a steam jacket or boiler. The vapor stream is collected overhead, cooled, and condensed. As the waste s more volatile, high vapor pressure components are driven off, the boiling point temperature of the remaining material increases. Less volatile components begin to vaporize and once their concentration in the overhead vapors becomes excessive, the batch process is terrninated. Alternatively, the process can be terrninated when the boiling point temperature reaches a certain level. The residual materials that are not vaporized are called still bottoms. 

Chlorinated solvent vapor degreasers can be replaced with high pressure power washers which do not generate spent solvent hazardous wastes or toxic fugitive emissions. 

Service company wastes such as empty drums, drum rinsate, vacuum truck rinsate, sandblast media, spent solvents, spilled chemicals, and waste acids... 

When used as a spent solvent, listed as a hazardous waste from nonspecific sources Yes EPA 1981c (40 CFR 261.13) EPA 1981e... 

Paint wastes Ignitable wastes Spent solvents Acids and bases... 

Photography waste with heavy metals Heavy metal solutions Waste inks Spent solvents... 

Ignitable wastes Spent solvents Paint wastes... 

On April 8, 2003, U.S. EPA proposed to add benzene and 2-ethoxyethanol to the list of solvents whose mixtures with wastewater are exempted from the definition of hazardous waste.23 U.S. EPA is proposing to provide flexibility in the way compliance with the rule is determined by adding the option of directly measuring solvent chemical levels at the headworks of the wastewater treatment system. In addition, U.S. EPA is proposing to include scrubber waters derived from the combustion of spent solvents to the headworks exemption. Finally, U.S. EPA is finalizing the Headworks Rule, as follows24 ... 

Printing industry Heavy-metal solutions Waste ink Spent solvents Spent electroplating wastes Ink sludge containing heavy metals... 

The Resource Conservation and Recovery Act (RCRA) was enacted in 1976 and was revised substantially by the Hazardous and Solid Waste Amendment (HSWA) of 1984 (40 CFR pts. 260-280). The RCRA regulates the management of solid wastes that are hazardous. The definition of solid wastes in these regulations generally encompasses all discarded materials (including solid, liquid, semisolid, and contained gaseous materials) and many secondary materials (e.g., spent solvents, byproducts) that are recycled or reused rather than discarded [3]. Products such as commercial pesticides are not ordinarily solid wastes, but they become solid wastes if and when they are discarded or stored, treated, or transported prior to such disposal. 

Good engineering prachce is to design chemical processes with an emphasis on recovering and reusing spent solvents [8]. However, not aU solvents will be recovered, and these will eventually need to be disposed. When disposing of solvent waste, there are several factors which must be considered to determine the appropriate waste heatment or disposal method. Some of these factors include the cost of disposal methods, overall toxicity of the waste, and environmental impact in the case of accidental and intenhonal releases. 

Although several methods are used to reduce or ehminate solvent consumption within a pharmaceutical process, solvents are often used in excess in order to carry out reachons in a dilute environment because of solubihty and product selectivity issues [2]. As solvents still have a great influence on the quality of the final products, it can be very difficult to find suitable replacements [43]. It is therefore desirable to find solvents for a process that can be easily recovered, separated, and purified for reuse. Spent solvents that are not recovered must be disposed of as wastes, which can be quite costly and add to the environmental burden. 

If a hazardous waste such as a spent solvent can be recycled and used on-site, it might be exempt from many of the above listed requirements, as well as from DHS permit requirements. The recycling must generally be done continuously without storing the waste prior to reclamation. The recycled material is not considered a waste. Other conditional exemptions for recycling of hazardous waste also exist (Section 25143.2, California Health and Safety Code [CH SC]). 

The use of sc-C02 as a solvent and reagent represents an application that reduce not only the amount of waste organic solvents, but also the emission of C02 derived from the combustion of spent solvents. 

Secondary waste produced by the implementation of the separation process should be as low as possible. Some current strategies rely on the development of extraction systems based on only four atoms, C, H, O, and N, to convert the spent solvent into environmentally friendly gases. 

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