Coastal Marine Environment Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 296

sediments (option 2) can be an expensive procedure, especially when the quantities are
large. An expedient procedure is to perform gravity separation of the contaminated sedi-
ment and to remove the coarse fractions for treatment and reuse as construction material.
A useful technique for sediments that do not contain much organic matter is to form larger
particles by promoting aggregation of the ines with lime. Contaminated ine fractions can
be treated or disposed in secure settling ponds. These settling ponds are not unlike those
obtained in natural resource extraction processes (Chapter 5). Techniques for dewatering
and hastened sedimentation of the suspended ines that constitute the ine fractions of the
sediment were discussed in Chapter 5. In the case of the ines in sediments, solidiication,
and compression by ilter pressing can be used (Yamasaki et al., 1995).

8.5.4 Removal of Contaminated Sediments by Resuspension

Dredging of the sediments is necessary to facilitate the passage of the vessels or remediate
contaminated sediments. However, disturbance of the contaminated sediments can spread
the contamination. Alternatively, a two stage resuspension method is suggested as a new in
situ method for remediation of highly contaminated sediments (Fukue et al., 2012b) (Figure
8.17). In the irst stage, air jets are used in the conined water column to create a strong
turbulent low to suspend the sediments. After a certain period, the coarser sediments are
allowed to settle, whereas the iner sediments remain suspended. In the second stage, the ine

Fine
particles Silt protector

Silt protector

Smaller
particles

Sediment
Coarser, heavier particles Resuspension rod

Control panel

Addition of
agent

Floater

pH

pH/COD/SS

P SS

P P

Suspension

Mixing

Resuspension

Condensation tank

Discharge

Primary
tank
Silt fence

Flow meter

Transportation

Filtration bags
Dewatering

Sediment

No
Ye s

SS

Dispersion

Water release

FIGURE 8.17
Schematic drawing of the entire resuspension process. The top drawing is a “blow-up” illustration of the resuspen-
sion principle.