Case Studies: Full-Scale Operations and Delivery Systems - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 337

problems in waste treatment: (1) differences between the laboratory sample and the
actual material to be treated in the field, and (2) failure to consider the differences
in scale between handling waste in the field and in the laboratory.
The first problem is all too common in remediation projects of all types and can
be especially difficult in radioactive and mixed-waste situations where sampling is
difficult and dangerous. The irony is that very detailed and careful sampling of the
waste is generally done in the feasibility phase of a remedial project to characterize
the waste, but these samples are typically too small, too old, or otherwise inadequate
to be used in the treatability study phase. Resampling for the treatability study is
seldom anywhere near as careful and complete as for the initial waste characteriza-
tion. The obvious solution is better planning at the time of the feasibility study or
better resampling for the treatability study.
The second problem can usually be eliminated or minimized by early involvement
and cooperation of all persons involved in the project, including laboratory scientists,
engineers, operations people, and regulatory personnel. The area of greatest difficulty
is mixing. In the laboratory, the test samples are usually hand mixed in small containers
or with typical laboratory mixers. These methods seldom replicate the mixing action
that takes place at large scale. When intimate mixing is not required, the order of addition
and the timing are not critical, and the waste-reagent mixture has desirable rheology,
field implementation typically proceeds with no major problems. Chemical reactions
that cause excessive temperature increases, gas evolution, and odor problems create
problems during field implementation that go unnoticed at the laboratory scale. Another
common problem is the development of undesirable rheology (high viscosity, stickiness,
and non-newtonian flow) that requires special equipment or undesirable operational
restrictions at field scale. Expensive re-formulation or engineering modifications are
often required for any of these problem situations.
13.3 DELIVERY SYSTEMS
Delivery systems are the means by which S/S processes are implemented, including
the equipment and the complete process of developing, designing, planning, permitting,
operating, controlling, and financing an S/S project. 1 The project may be remedial or
continuing; the equipment may be mobile/portable or fixed; the regulatory structure
may be under the U.S. Environmental Protection Agency (Resource Conservation and
Recovery Act, Comprehensive Environmental Response Compensation, and Recovery
Act), or the Nuclear Regulatory Commission/Department of Energy or both. The equip-
ment may be designed, built, owned, and operated by an S/S vendor; a generator; a
central RCRA treatment, storage, and disposal facility (TSDF); or even a public entity,
or any combination of these elements. The ultimate disposal of the S/S product may be
part of the delivery system, or it may be totally separate. Many of these elements are
outside the scope of this chapter. They are, however, considerations that affect every
phase of S/S technology. Limitations in any of these areas may prevent implementation
of the chosen delivery system and S/S process.
Most commercial S/S processes are quite simple conceptually and utilize stan-
dard mechanical equipment. The nature of the equipment depends on whether the
method is “ in situ ” or “ ex situ .” “ Ex situ ” means excavating the waste, treating it,
and landfilling it, either in the same excavation or another location. Ex situ systems