Effective Cleanup of Groundwater Contaminated with Radionuclides Using Permeable Reactive Barriers - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 166

Bioaccumulation

UO 2+
2

UO 2+
2

Bioprecipitation

UO 2+
2

UO 2

UO 2+ + HPO 4 - = HUO 2 PO 4

2L-(ligands)

2

UO 2+

2

Biosorption

FIGURE 9.10
Radionuclide interactions with microorganisms. (Adapted from Interactions of Microorganisms
with Radionuclides , Lloyd, J.R. and Macaskie, L.E., Biochemical basis of microbe-radionuclide
interactions, 313-342, Copyright 2002, with permission from Elsevier.)

9.3 Construction Methods of PRBs
First, cut-off wall construction techniques were applied to PRBs. Single-
and two-phase diaphragm walls, bored-pile walls, jet grouting, thin walls,
sheet-pile walls, driven cutoff walls, injection, and frozen walls are the most
common cutoff wall alternatives. To date, in addition to using cutoff wall
construction methods, an increasing number of innovative techniques are
being used to construct PRBs such as: drilling methods; deep-soil mixing;
high-pressure jet technology; injected systems; column and well arrays; deep
aquifer remediation tools (DART); and hydraulic fracturing and biobarriers.
The main configurations of PRBs are

• Continuous reactive barriers
• Funnel-and-gate systems
• Arrays of wells
• Injected systems

The basic performance requirements for a reactive zone within a PRB are
(Beitinger and Bütow 1997, Smyth et al. 1997, Beitinger 1998)

• Replaceability of the reactive materials
• Higher permeability than the surrounding reservoir
• Stability against fines washed into barriers from the surrounding
soil
• Long life-span

The selection of the construction technique mainly depends on site charac-
teristics (Gavaskar 1999), for example,