Practical aspects of in-situ electrokinetic extraction

Electrokinetic extraction is an emerging technology that can be used to remove contaminants from heterogeneous fine-grained soils in situ. Contaminants in the subsurface are removed by the application of a direct-current electric field across the contaminated soil. The primary contaminant transport and removal mechanisms are electroosmotic advection and ionic migration. However, there are many complex physicochemical reactions occurring simultaneously during the process that may enhance or retard the cleanup process. Nonetheless, the viability of the technology has been established by results obtained from many bench-scale and large-scale laboratory and pilot-scale field experiments performed on various soils. This paper will review the fundamental concepts of the technology and discuss some important practical aspects and design criteria of the technology for field implementations. An example on cost analysis of the technology is also presented to demonstrate the use of various equations presented in the paper and to illustrate the cost-effectiveness of the technology.link_to_subscribed_fulltex

Influence of electroosmotic treatment on the hydro-mechanical behaviour of clayey silts: preliminary experimental results

Preliminary results of an investigation focused on the influence of electrokinetic treatment on the mechanical and hydraulic behaviour of clayey soils are presented. The experimental programme aims at providing a contribution to the sustainability of contaminant extraction or containment via electroosmosis. Changes in the hydraulic and mechanical properties of two illitic clayey soils, subjected to a DC electric field, were investigated. Samples of the two soils were subjected to electrokinetic filtration, for different periods of time, and under different constant loads. Afterwards, they were tested under onedimensional compression to detect changes in stiffness and hydraulic conductivity due to the electrical treatment. After the application of a DC field for a few hours, a small reversible increment in the average soil stiffness was observed, with respect to the untreated soil, while the hydraulic conductivity was not affected substantially. Dramatic changes of the mechanical and hydraulic soil properties, correlated to changes of the soil pH, were observed following non-conditioned electrokinetic treatment with duration of the order of days.Peer ReviewedPostprint (published version

Mechanical and Physical Effects of Electroosmotic Dewatering of Clayey Soils

Electrokinetic (EK) treatment is studied for fine grained dredged soils as an innovative and cost-effective method to accelerate the dewatering and improve their mechanical behaviour. Owing to their high-water content, the dredged sediments take a very long time for the consolidation process, much more than those considered in the typical problems of geotechnical engineering. Some electroosmotic tests in oedometer conditions on a clayey soil have been carried out at the University of Napoli Federico II in a special apparatus (special oedometer), adopting a pore fluid with different salt concentration. The results show that the addition of soluble salts in small quantities (until 8 g/l) can improve the electroosmotic consolidation of soft clay. On the contrary, excessive salinity reduces the efficiency of electroosmotic dewatering. The optimal salinity content has been then determined. At the end of the EK tests, some triaxial tests have been performed on the treated specimens in order to analyse the effectiveness of the EK treatment in the improvement of the soil mechanical propertie