Once soil is contaminated, it will never return to its previous state and will remain as a burden for future generations unless remedial measures are implemented. One type of soil contamination problem is contamination by volatile organic compounds (VOCs). It is believed that VOCs remain in soil or groundwater indefinitely because they do not decompose easily in soil and penetrate deep into the ground due to their specific weight, which is higher than water. Furthermore, groundwater contaminated with VOCs can flow to other locations, spreading the contamination to a broader area.
Shimadzu’s electrical resistance heating method is technology for remediating VOC-contaminated soil that is based on technology first developed in the Netherlands. The method was developed and commercialized by Shimadzu through extensive research and development into soil contamination conditions and soil characteristics in Japan. A major feature of the method is its ability to remediate soil quickly and at a low cost.
In the electrical resistance heating method, an alternating current is applied across electrodes inserted into the ground. This heats the soil to between 40 and 80 °C by Joule heating generated from the electrical resistance of the soil itself. Raising the soil temperature separates the VOCs from the soil as vaporized gases that can be efficiently recovered. If a soil temperature is selected that is optimal for activating microorganisms that break down the VOCs, then the technology can also be used to powerfully assist bioremediation methods.
Even areas directly underneath factories in operation, or under warehouses, or parking lots, for example, can be remediated by burying the electrodes and cable wiring in the ground. The method is almost completely unaffected by the concentration or depth of contaminants, so it can even be used to deal with deep, highly concentrated contamination. Clay layers are particularly well-suited to this type of remediation because they more easily transmit electrical currents. This soil remediation technology also minimizes environmental impact by eliminating the need for large-scale civil engineering work and by generating minimum noise and vibration.
So far, the method has been used for over 30 projects, including an ongoing remediation project, and, in all cases, customers have expressed satisfaction with the effectiveness of the remediation.