Page 535 - Materials Chemistry, Second Edition

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506 Waste Management Practices: Municipal, Hazardous, and Industrial
The LDR program has three major components that address hazardous waste disposal, dilution,
and storage. The Disposal Prohibition states that before a hazardous waste can be land-disposed,
treatment standards specific to that waste material must be met. A facility may meet such standards
by either (U.S. EPA, 1999):
● Treating hazardous chemical constituents in the waste to meet required treatment levels.
Any method of treatment can be used to bring concentrations to the appropriate level
(except dilution); or
● Treating hazardous waste using a treatment technology specified by the U.S. EPA. Once
the waste is treated with the required technology, it can be land disposed.

The Dilution Prohibition states that waste must be properly treated and not simply diluted in
concentration by adding large volumes of water, soil, or nonhazardous waste. Dilution does not
reduce the toxicity of the hazardous constituents but only increases total volume. The Storage
Prohibition states that waste must be treated and cannot be stored indefinitely. This prohibition pre-
vents generators and treatment, storage, and disposal facilities (TSDFs) from “warehousing” haz-
ardous waste for long periods to avoid treatment. Waste may be stored, subject to the LDR, in tanks,
containers, or containment buildings, but only to accumulate quantities necessary to facilitate
proper recovery, treatment, or disposal.

16.3 WASTE TREATMENT PRIOR TO LAND DISPOSAL

Chemical treatment of a hazardous waste is carried out via the application of one or a series of
chemical reactions. Chemical processes may be applied for the treatment of soluble contaminants
(e.g., wastewaters), or mixtures of solids and liquids (sludges) containing hazardous constituents.
Table 16.1 lists the common chemical and physical processes for the treatment of hazardous wastes.

16.3.1 NEUTRALIZATION

Neutralization is used for the treatment of acidic or alkaline wastes, many of which are designated
as RCRA corrosive wastes. A waste that exhibits the characteristic of corrosivity as defined in 40
CFR Part 261.22 is aqueous with a pH of less than or equal to 2, or greater than or equal to 12.5,
or is a liquid that corrodes steel at a rate greater than a specified rate (see Chapter 11). Some listed
hazardous wastes (e.g., spent pickle liquor generated by steel finishing operations, K062) are also
corrosive wastes and must be neutralized.

TABLE 16.1
Common Chemical Treatment Processes for Hazardous Wastes

Process Specific Aapplications
Neutralization Neutralization of acidic or basic properties of a liquid waste to
reduce its corrosive properties.
Precipitation Removal from solution of dissolved hazardous inorganic
contaminants by chemical reaction.
Oxidation/reduction Changing the valence of an element via addition or removal of
electron(s). The reaction renders that element less toxic and
amenable to other treatment processes.
Sorption Physical adhesion of soluble hazardous contaminant molecules to
the surface of a solid sorbent.
Stabilization Stabilization and solidification of metal-containing waste sludges by
precipitation with Portland cement, fly ash, or similar fixative agent.