Leaching Processes and Evaluation Tests for Inorganic Constituent Release from Cement-Based Matrices - Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes - page 245

In recognition of similar, albeit slightly varying, leaching protocols throughout
the European community, Comité Européen de Normalisation (CEN) has commis-
sioned the Characterization of Waste Technical Committee TC-292 with the task of
harmonization of leach characterization approaches. 173 One focus of the committee
is to define a limited set of leaching protocols that may be used to describe inorganic
release from a wide variety of materials (e.g., building materials, incinerator residues,
solidified wastes) in a broad range of beneficial reuse or disposal scenarios.
The classification system adopted by CEN/TC-292 segregates leaching protocols
into three groups: characterization tests, compliance tests, and on-site verification
tests based on the level of detail and purpose of the leaching protocol. 174 On-site
protocols tend to be simple tests providing the least level of detail, such that the
output test information affords only a “pass/fail” comparison to a regulatory limit
or a material acceptance parameter. Compliance testing allows for incorporation of
regulatory or permissible release limits for specific release scenarios, while highly
specific characterization tests are used to determine intrinsic leaching parameters or
release mechanisms. Increasing the detail and complexity level of the leaching tests
and interpretation protocols allows for elucidation of leaching potentials, retention
and release mechanisms, sensitivity analyses, and calculation of systems failure and
environmental risk.
A similar effort (i.e., to define leaching tests, optimize leaching test selection,
and develop interpretation methods) is ongoing in the United States in coordination
with the USEPA Office of Solid Waste. In the proposed assessment framework, 5 the
benefits of the more detailed characterization above a basic “pass/fail” of regulatory
or compliance level assessment come in terms of a reduced requirement on the detail
of subsequent testing (e.g., on-site verification) for large volume producers, more
accurate predictions of long-term environmental impact, flexibility for the selection
of appropriate waste management solutions, and lower liability associated with
accidental release from test materials.

10.4.2 L EACHING T EST C LASSIFICATION BY A PPLICATION

Chapter 11 summarizes commonly used standardized leaching (and other) tests in
North America and Europe. These leaching tests may be used to (i) screen materials
(e.g., classify waste materials as “hazardous“ or “non-hazardous”), (ii) mimic field
leaching (e.g., to produce a representative field leachate), and (iii) determine intrinsic
properties of the waste material. This section describes the applications of these
leaching tests. Both this chapter and Chapter 11 are “stand alone” chapters. Although
there is some overlap and redundancy on the subject of leach testing between this
section and Chapter 11, the objectives are different for the two chapters and they
complement each other on this topic.

10.4.2.1 Screening Tests

Screening tests are relatively quick (~24 hours), low-cost evaluations designed to
classify a waste material or to ensure that the material meets certain acceptability
criteria. Usually, these tests consist of a single-batch extraction using size-reduced