**5. Large scale applications**

can be used as a transportation mechanism to introduce into the soil the nutrients and other chemicals that may facilitate the bacterial growth and development, as well as the supply of

Lageman [59] developed a technology called Electrokinetic Biofence (EBF). The aim of the EBF is to enhance biodegradation of the VOCs in the groundwater at the zone of the fence by electrokinetic dispersion of the dissolved nutrients in the groundwater. EBF which con‐ sists of a row of alternating cathodes and anodes with a mutual distance of 5 m. Upstream of the line of electrodes, a series of infiltration wells were installed, which have been periodi‐ cally filled with nutrients. After running the EBF for nearly 2 years, clear results have been observed. The concentration of nutrients in the zone has increased, the chloride index is de‐ creasing, and VOCs are being dechlorinated by bio-activity. The electrical energy for the

The removal of volatile and semi-volatile organics from soil can be carried out heating the soil, evaporating the volatile organics and aspirating the vapors, which in turn are trapped in the appropriate absorbent such as active carbon to be finally eliminated by incineration. The heating of soil can be done in several ways. One possibility is the use of an electric cur‐ rent. Soil is not a good electric conductor, so the passing of an electric current generates heat. In electrokientic remediation, it is used a continuous electric current because the objective is to transport the ionic and nonionic contaminants out of the soil. In the case of electroheating, a transportation of the contaminants using the electric field as a driven force is not necessa‐ ry. The electric field is only used as a source of energy that is transformed from electric ener‐ gy into heat. That is why in electroheating the continuous electric field is substituted by an alternate current that supplies the energy but does not induce transportation. Soil is not a good electric conductor. The conductivity of soils is much lower than the typical electric conductor such as metals. The conductivity of soil largely varies with the moisture content and the presence of mobile ions. Anyway, the conductivity of soil is usually low and the heating is easy to achieve with an alternate current. It is recommendable to avoid the use of electroheating in saturated soils. A soil saturated in moisture favors the transportation of

Electroheating shows several advantages form other technologies designed for the removal of volatile organics from soils. In electroheating, the heating of soil is directly related to the electric field intensity. So, the increase of temperature and the final temperature in the soil can be easily controlled adjusting the intensity of the electric field. Furthermore, the heat is generated into the soil, in the whole volume at the same time, achieving a more uniform temperature in the area to be treated. The uniform temperature permits a uniform removal

Electrical heating was used in the remediation of a contaminated site in Zeist, the Nether‐ lands [60]. The site was severely polluted with chlorinated solvents such as perchloroethy‐ lene (PCE) and trichloroethylene (TCE) and their degradation products are cis-1,2 dichloroethene (C-DCE) and vinyl chloride (VC). Satisfactory results were obtained in the

other chemicals that can contribute to the degradation of the contaminants [57, 58].

EBF is being supplied by solar panels.

222 Organic Pollutants - Monitoring, Risk and Treatment

current instead of the electric heating.

of the contaminants and a more efficient use of the energy.

**4.4. Electroheating**

Electrokinetic remediation has been used as a remediation technology in several tests at field scale. In the USA, field projects were carried out or funded by USEPA, DOE, ITRC, US-Ar‐ my Environmental Centre, as well as companies like Electropetroleum Inc. [63], Terran Cor‐ poration, and Monsanto, Dupont, and General Electric which developed the LasagnaTM technology [64, 65]. In Europe, more field projects with electrokinetic remediation have been carried out, specially associated to the commercial activity of the Hak Milieutechniek Com‐ pany [66, 67]. Recently, some field experiences were reported in Japan and Korea [68]. Some of these tests deal about the remediation of polluted sites with organic contaminants such as organochlorides, PAHs and PCBs. Considering the information available in literature, the cost of field application of electrokinetic remediation is about an average value of 200 \$/m3 for both organic and inorganic contaminants, however it must be kept in mind that electro‐ kinetic remediation, like any other remediation technology, is site specific and the costs can be vary from less than 100 to more than 400 \$/m3 [69].

#### **6. Future perspectives**

The scientific knowledge accumulated in the last 20 years conducted to several lessons learned that must be keep in mind in the design of projects for the remediation of contami‐ nated sites. Thus, the remediation of contaminated soils with organic contaminants is site specific. The results obtained in the remediation of a site cannot be assumed for other conta‐ minated sites. This is due to the large influence of the physicochemical properties of the soil and its possible interactions with the organic contaminants in the results of the electrokinetic remediation treatment. Besides, the chemicals used for enhancing the electrokinetic treat‐ ment may complicate the behavior of the system and the removal results may largely vary from one site to another. Recently, it has been considered that the combination of several re‐ mediation techniques may improve the remediation results, especially in sites with complex contamination, including recalcitrant organics compounds and inorganic contaminants. The combination of electrokinetics with bioremediation, phytoremediation, chemical oxidation or electrical heating, presents very interesting perspectives for the remediation of difficult sites. It is expected the combination of remediation technologies to improve the remediation results, saving energy and time.

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