Effective Cleanup of Groundwater Contaminated with Radionuclides Using Permeable Reactive Barriers - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 168

To implement an electrochemical technology, first wells are drilled around
the contaminated region. Electrodes are installed in the wells and a low
direct current or low potential gradient is applied to the electrodes (Reddy
and Cameselle 2009). The generated electric field induces several transport,
transfer, and transformation processes moving the contaminants to the elec-
trodes where they can be removed. Also, the contaminants may be immo-
bilized or degraded within the contaminated site. Other terms used for
electrochemical remediation include electrokinetics, electrokinetic remediation,
electroremediation, electroreclamation , and so on. If only water is used around
the electrodes, the process is called unenhanced electrochemical remedia-
tion. Enhanced electrochemical remediation uses conditioning solutions and
ion exchange membranes.
Key advantages of electrochemical remediation are
• Flexibility in terms of choosing ex situ or in situ
• Applicability to low-permeability and heterogeneous layers (clay,
silt, loess, etc.)
• Both saturated and unsaturated soils can be treated
• Heavy metals, radionuclides, organic contaminants, and their mix-
tures can be treated
• It can be integrated into conventional systems
The complex character of the transport, transfer, and transformation pro-
cesses and the influence of buffer capacity, mineralogy, organic matter con-
tent, geochemistry soil-contaminant interactions and heterogeneity on the
efficacy require extensive investigations in the design phase. All this is nec-
essary to guarantee successful implementation of electrochemical remedia-
tion technologies.
9.4.1 Electrochemical Processes
The fundamental transport mechanisms caused by an electric field are
(Gregolec et al. 2005)
• Electromigration (transport of charged ions or ion complexes in
solution)
• Electroosmosis (movement of liquid relative to a charged stationary
surface)
• Electrophoresis (movement of charged particles relative to a station-
ary fluid)
Electromigration and electroosmosis occur in fine-grained soils, electro-
migration and electrophoresis are dominant in coarse-grained soils.