Environmental Engineering Reference
In-Depth Information
12.7.2.3
Mixing Water
Mixing water for S/S operation should not contain concentrations of oils, acids,
salts, alkalis, organic matter, or other substances that will be detrimental to the
successful execution of the S/S treatment process. Chemical analysis may be required
when the water is of questionable quality.
12.7.3
M
IXING
AND
P
LACEMENT
Prior to full-scale operations, a field demonstration should be performed. At least
500 m
3
of contaminated material should be processed and the required tests, as
described in Section 12.8, should be performed on representative samples of the
treated material. A field demonstration should be performed on each distinctive type
of material or contaminant to be treated. The full-scale processing equipment should
be used for the field demonstration. Reagents, mix ratios, and mixing procedures
used during the field demonstration should be the same as those used for the
remainder of the work.
Mixing time, mixing speed, and amounts of contaminated material, reagents,
and water added to each batch should be recorded. Mixing time, mixing speed, and
batch proportions should be maintained within the limits specified in the approved
Work Plan as modified during the field demonstration. The use of optical tracers
has been evaluated to indicate the degree of mixing.
20
Mixing can also be monitored
in-line by measuring electrical resistance or capacitance.
20
To prevent double handling, it is preferable to place treated material directly
into the permanent storage area rather than stockpiling it until post-treatment testing
is completed.
21
12.7.4
S
AMPLING
AND
T
ESTING
F
RESHLY
M
IXED
W
ASTE
12.7.4.1
Sampling Freshly Treated Wastes
As indicated above, there are techniques that can be used to monitor the mixing and
homogeneity of freshly treated wastes in-line during the mixing process. However,
they may be too complicated, too expensive, or too unreliable for use in field
operations at the moment.
If a batch operation is used and the treated waste is grout, approaches similar
to those for fresh concrete can be used. Standard method CRD-C 620-80 outlines
techniques for sampling grouts from mixers, pumps, and discharge lines.
22
12.7.4.2
Content of Cement or Additives
ASTM C 1078
23
specifies a procedure to measure the cement content in freshly
mixed concrete. If the waste and other additives do not react with cement immedi-
ately, this method can be used. However, other methods may be required if some
immediate reactions happen between cement and other components. Another com-
mon component in the cementing materials or additives for S/S is lime. A laboratory
Search WWH ::
Custom Search