Environmental Engineering Reference
In-Depth Information
field S/S of hazardous wastes. The binder used was a sodium silicate-activated
blended cement.
Tests of hardened treated wastes evaluate product performance and establish the
process parameters for generating an acceptable product. Post-treatment testing
generally consists of both chemical and physical tests. Most projects use TCLP
testing, focusing on the site-specific contaminants of concern. Other parameters
tested vary from project to project, but often include moisture content, unconfined
compressive strength, permeability, and pH.
12.7.2
P
RE
-T
REATMENT
T
ESTING
12.7.2.1
Cements and Additives
Some physical and chemical properties of cements and additives can be obtained
from suppliers. A certificate of analyses should accompany each shipping unit of
the materials. If a blended cementing material is used, each component should be
within the acceptable range. Several different tests may have to be used to determine
the components in the blended material.
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Based on the nature and characteristics of the additive used, some test methods
or procedures may be found in relevant areas or developed for quality control
purposes. For example, measurement of solution-specific gravity by hydrometer was
an acceptable quality control technique in the field for the sodium silicate solution
concentration.
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12.7.2.2
Wastes
The formulation and treatment processes are determined according to the physical
and chemical characteristics of the wastes. Once the formulation and treatment
processes are chosen through laboratory and pilot feasibility tests, some properties
of the waste, such as moisture content, particle size distribution, and concentration
of contaminants, may be found to have the most significant effects on the properties
of the treated wastes. Thus, these properties need to be monitored before treatment.
The moisture content of the waste will affect the mixing process and the properties
of both fresh and hardened treated wastes. A significant variation of moisture content
may require the adjustment of the mixing water to be added. The moisture content
in untreated wastes can be measured by following ASTM D 2216
18
or ASTM D
4643.
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Additionally, commercially available moisture analyzers can be used as quick
measurement tools in field QA testing.
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When the waste is granular, it is important to control the particle size within
certain limits since it may have a significant effect on the physical properties and
leachability of treated wastes. In the field, granular wastes may have to be crushed
and sieved to pass a specified screen size.
A S/S formulation could be sensitive to the contaminant concentration and may
need modification if there is a large variation in contaminant concentrations. Con-
taminant concentration should be verified to ensure that the formulation meets
expected variation ranges. The USEPA publishes methods for analysis of contami-
nant concentration.
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