Features
４　Action to Remediation of Soil contamination(3)?PCBs and Dioxinst
Yasushi HOGA Civil Engineering Div.
Konoike Construction Co., Ltd.

1. PCB and dioxin
Polychlorinated biphenyl (PCB) is a mixture of synthetic organic chemicals extensively used in hundreds of industrial and commercial applications. The widespread utility is due to its characteristics, such as electrical insulating properties, incombustibility, high boiling point, and chemical stability to acid and alkali. However, since 1972, prohibition on the manufacture of PCB has long been implemented in Japan because of prevailing concerns over its toxic effects and persistence in the environment. Consequently, the treatment of PCB essentially maintained in various places and the measures against the contaminated soil are needed promptly.
On the other hand, dioxin is another highly persistent chemical, which is diffused into the environment by combustion. It is formed by burning chlorine-based chemical compounds with hydrocarbon and is an unintentional by-product of industrial processes, such as garbage incineration and from the electric furnace used in the manufacture of steel. Indeed, PCB and some agricultural chemicals containing dioxin as impurities are possibly accumulating continuously into the environment just like a mud on the bottom of a lake, etc.　
This condition remains a threat to both our health and our environment. Hence, the “Law Concerning Special Measures against Dioxins" defines polychlorinated dibenzo-para-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF), including coplanar PCB* as "dioxins".


2. Government regulation in Japan
The environmental standards (refer to Table 1) concerning contamination of PCB on water, groundwater, and soil are identified. In addition, the elution standards and content standards are stipulated as third-class specification toxic substance in the “Soil Contamination Countermeasures Law” (May 2002 proclamation)1). We must keep it in mind when treating polluted soil.
The official declaration as regards the terms for disposal and storage conditions, as well as the duties of a PCB waste storage entrepreneur, PCB manufacturer, and the role of the national and local governments is identified in "Law Concerning Special Measures Against PCB Waste" (June 2001 proclamation). The types of PCB wastes, collection and conveyance, disposal methods, and acceptance standards for the last waste disposal place are stated in " Waste Disposal and Public Cleansing Law (Law No.137 of 1970) " (December 1970 proclamation). This law also places emphasis on the treatment of PCB-polluted soil.

Table 1 　 Environmental standards

Table 1 　 Environmental standards

Regarding dioxin, the environmental standards on the quality of the atmosphere, water, bottom sediment, and soil are specified based on the “Law Concerning Special Measures against Dioxins”. (refer to Table 1) In addition, the necessary regulation and measure on dioxin-contaminated soil are also stipulated. This law is different from the “Soil Contamination Countermeasures”. Based on the “Law Concerning Special Measures against Dioxins”, three regions are designed as the measured areas against soil contamination in Japan (as of February 2006). The designation at the two regions has already been lifted because the assessment is complete. Moreover, the investigation on soil pollution caused by dioxin is noted in "The Manual of the Survey and Measurement of Dioxins in Soil" (January 2000)2).

3. Development of countermeasure technology
In the existence of soil pollution in a certain area, the person responsible for the contamination and the landowner have the sole task to eradicate the contamination promptly and to ensure the security of the people residing within the vicinity. Therefore, practical application and dissemination of investigation procedures in the event of soil pollution and countermeasure technology, which should be economical and safe, are strongly desired. Especially, as regards PCB and dioxin which are highly toxic and stable chemicals, detailed objective evaluation and technicality of the technology as to the effects of the treatment or the influence of the treatment on the peripheral environment are significant.
The Environment Agency (currently, the Ministry of the Environment) demonstrated an investigation 3) on dioxin pollution soil purification technology in 1999. Six technologies (Table 2), such as melt-solidification and chemical decomposition method, etc. were selected. Since 2003, the study on the establishment of technology, which can purify dioxin and PCB, has been conducted. This study resulted in the formation of totally 14 (Table 2) out of the methods on melt-solidification, Thermal Phase Separation (TPS), and steam decomposition. The result is submitted to the Ministry of the Environment HP4)5) and is undergoing development for future investigation of technology to salvage contamination of the environment by PCB or dioxin.

Table 2 Technology approved by the Ministry of the Environment for
investigation on dioxin-polluted soil purification
Table 2 Technology approved by the Ministry of the Environment for investigation on dioxin-polluted soil purification
（Fig. 1 Vitrifiction facilities (GeoMelt 100t / batch, 2003, Hashimoto-shi, Wakayama)

Fig. 1 Vitrifiction facilities
(GeoMelt 100t / batch, 2003, Hashimoto-shi, Wakayama)

Fig.2 Thermal Phase Separation facilities (Treatment of dioxin-contaminated soil, 2006, Toyono-gun, Osaka)
Fig.2 Thermal Phase Separation facilities
(Treatment of dioxin-contaminated soil, 2006, Toyono-gun, Osaka)

〔Reference〕
1) http://www.env.go.jp/en/lar/soil_cc_law/index.html
2) http://www.env.go.jp/chemi/dioxin/manual/dojo-manual.pdf
3) http://www.env.go.jp/press/press.php3?serial=2417
4) The year of 2003･2004　http://www.env.go.jp/water/dojo/diox-tech/index.html
5) The year of 2005　http://www.env.go.jp/water/dojo/gijyutsu/index.html

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