Organic Polymer Processes

The major organic polymer process (including urea-formaldehyde, unsaturated polyesters) currently in use is the urea-formaldehyde process. In the process, a monomer is added to the waste or sludge and thoroughly mixed. Next, a catalyst is added to the mixture and mixing continues until the catalyst is dispersed. The mixture is transferred to another container and allowed to harden. The polymerized material does not chemically combine with the waste. Instead, a spongy mass forms, trapping the solid particles while allowing some liquid to escape. The polymer mass can be dried before disposal.

Table 11.16.2 compares the advantages and disadvantages of the above S/S processes. Table 11.16.3 illustrates the compatibility of selected waste categories with S/S processes.

Figures 11.16.1 and 11.16.2 depict generic elements of typical ex situ and in situ S/S processes for soils and sludges. Ex situ processing involves: (1) excavation to remove the contaminated waste from the subsurface; (2) classification to remove oversize debris; (3) mixing; and (4) off-gas treatment. In situ processing has only two steps: (1) mixing; and (2) off-gas treatment. Both processes require a system for delivering water, waste, and S/S agents in proper proportions; and a mixing device (e.g., rotary drum paddle or auger). Ex situ processing requires a system for delivering treated waste to molds, surface trenches, or subsurface injection. The need for off-gas treatment using vapor col-

S/S Binding Agent(s)

S/S Binding Agent(s)

FIG. 11.16.1 Generic elements of a typical ex situ S/S process. (Reprinted, from U.S. EPA, 1993.)
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