The application of solvent cleaning and vacuum heating has been studied as a method for rendering contaminated metal and paper PCB harmless. However, no research has been attempted to make soil and ballast harmless. The Railway Technical Research Institute (RTRI) has devised a method for treating PCB contaminated soil/ballast based on the "PCB ultraviolet decomposition/biological treatment" developed by RTRI, and studied its effects.
      The treatment of PCB-contaminated sludge (Fig. 1) makes it harmless by drawing most of the PCB contained in the sludge into isopropyl alcohol (IPA) through addition of IPA to sludge and centrifugation, and then application of ultraviolet decomposition and microorganism treatment. Further experiments are underway to treat completely even residual trace amounts of PCB in the centrifugate sludge by adding PCB decomposer microorganisms.
      For PCB-adhered ballast, a circulation treatment method (Fig. 2) was devised in which contaminated ballast comes into continuous contact with PCB-decomposer microorganisms, and bench tests (treatment of about 5 kg ballast) were carried out. Test results showed that this circulation treatment can remove PCB adhered to the surface of ballast.