Environmental Engineering Reference
In-Depth Information
the locculation tank. This sample (sample W) was found to consist primarily of water,
with concentrations of 134 Cs and 137 Cs in the undetectable range (<10 Bq/L).
The results shown in Figure 13.18 indicate that the concentrations of 134 Cs and 137 Cs
for the various samples obtained at different treatment stages, cavitation treatment and
removal of ine fractions could effectively decrease the concentrations of the radioactive
cesium (Sample B). The decrease of radioactive concentrations resulting from the removal
of ine suspended solids after cavitation treatment was 90.3% for both the 134 Cs and 137 Cs.
The effects of ultrasonic treatment followed by cavitation treatment for the coarse fractions
are not as effective (Samples from C to G).
13.6.4.2 Full-Scale Application
In full-scale application, carrying on from the pilot tests into actual performance, the pro-
cedure will consist of separating ine particles from the coarser materials, by cavitation,
ultrasonic treatment, deposition using the locculants, and pressing. As far as cesium-
contaminated surface soils are concerned, water treatment is not necessary when the
deposition of suspended solids is performed using locculants. The pilot study shows
that approximately 20% of the original sample in weight was separated from the original
soils, and that the separated ine fractions maintained a high concentration of radioactiv-
ity, meaning that the residual sand and gravel fractions in the original soil material were
remediated. However, the concentrations of radioactive cesium in the remaining ine par-
ticles after cavitation and ultrasonic treatments showed approximately 200 Bq/kg in 134 Cs
and 350 Bq/kg in 137 Cs.
13.6.4.3 Assessment of Sustainable Practice Success
The goal of remediating vast surface areas of contaminated surface layer soils requires one
to reduce the huge quantities of contaminated material as part of the treatment process
9000
8000
7000
137 Cs
6000
5000
134 Cs
4000
3000
After cavitation
2000
Duration of ultrasonic treatment
3 6 9 12 15 min
1000
0
A B C D E F G H
Original
soil
Fine
fraction
Samples
FIGURE 13.18
Results of the cavitation and ultrasonic treatments of samples contaminated with 134 Cs and 137 Cs.
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