Tokyo PCB waste-disposal business

(Industrial Waste Close-up 2007.04)

Japan Environmental Safety Corporation, Tokyo Facility

Location : Oumi 2-chome Chizaki Koto-ku, Tokyo (in disposal field inside the central breakwater)
Items subject to treatment : high-voltage transformer/condenser/stabilizer and insulation oil for pole-mounted transformers (in Tokyo metropolitan area)
Disposal capacity : 2 t/day in terms of PCB decomposition

Start of PCB disposal

PCB (polychlorinated biphenyl) has been widely used for various articles since 1955 as a useful material having chemical stability, heat resistance, insulation properties, etc. However, its toxicity has become as a social issue and then in 1972, the production stoppage and calling-in have been undertaken via administrative guidance and also the storage of PCB and articles containing PCB has become obligatory for businesses. In 2001, PCB waste disposal special measures law was enacted. According to the law, large companies such as electric power companies which have a large amount of PCB have carried forward its disposal by its own efforts, while for the storage of the small amount, its disposal has been driven forward as a national policy by setting up PCB waste disposal facilities at five places in Japan. The law makes it obligatory to dispose all PCB wastes by 2016 and then, these facilities play an important role in achieving such a goal. In December, 2004 KitaKyushu Facility has started its operation at first. Following this, Toyota, Tokyo, Osaka Facilities are now in operation, and further Muroran Facility is scheduled to operate in October of this year (2007).

PCB disposal process

Tokyo Facility (Photo 1) that we visited this time was built in the Tokyo metropolitan central breakwater disposal field. In 2005, it had started its operation, though it temporarily stopped operation because of an accident happened in March in next year(2006) and started again in October in the same year.

A view of Tokyo Facility
Photo 1. A view of Tokyo Facility

PCB wastes subject to carrying-in are those from Tokyo, Saitama, Chiba, and Kanagawa. In contrast to ordinal industrial wastes, the highly safe and sure disposal is critical so that its own receiving standards have been applied to the PCB wastes. At carrying-in stage predefined leak-proof metal container and a traffic monitoring system using GPS technology (Photo 2) are used in the transportation. Main roads such as an express way are preffered to use for transportation route and those who carry in waste have to purchase liability insurance of 300 million yen (minimum) in case of an accident.

GPS traffic monitoring system
Photo 2. GPS traffic monitoring system

The PCB disposal process is composed of two processes; a process for PCB waste of high concentration (% level) such as a high-voltage transformer/condenser/stabilizer, and a process for PCB waste of low concentration (ppm level) such as insulation oil of pole-mounted transformer.

Oil in high-voltage transformer/condenser is extracted and is stored in a PCB tank. Containers and parts are recycled as metals such as iron, copper and aluminum through a four-stage cleaning line (Photo 3) consisting of first-stage, second-stage, alkali, and third-stage units. Small parts such as a stabilizer are shredded, and then the shreds other than metals are prepared into slurry by grinding and mixing in a mill. In a chemical decomposition process, PCB is fed into subcritical water of 370 ℃/26.5MP along with sodium hydrate (NaOH) and oxygen and is decomposed into carbon dioxide (CO2), sodium chloride (NaCl) and water. Oil containing PCB is extracted from a container by cutting the container under liquid (Photo 4) so as to prevent PCB volatilization into air.

Cleaning equipment for PCB containers and parts
Photo 3. Cleaning equipment for PCB containers and parts

Submerged condenser-cutting equipment
Photo 4. Submerged condenser-cutting equipment

In the disposal process for PCB of low concentration, insulating oil containing PCB is extracted from pole-mounted transformers and is decomposed into biphenyl and NaCl through a dechlorination decomposition method (200℃ at ambient pressures) using chemical solvent DMI (1,3-dimethyl -2-imidazolidinone) and NaOH. After the extraction of insulation oil, containers are returned to Tokyo Electric Power Company and the treated oil is recycled as fuel. Most of discharged water from the two processes is cyclically used, while a part of such water is released into a public sewer through drainage treatment.

Introduction of multiple safety control system

As for safety measures, a multiple safety control system, unprecedented in conventional industrial waste disposal facilities, has been adopted. Exhaust air from the facility is treated with the combination of oil scrubbing and activated carbon adsorption treatments, and is always monitored. Since the floor surface of the facility is coated with resin which excels in impermeability, chemical resistance, and abrasion resistance. It works as a countermeasure against emergent spillage besides a spill-prevention dike. Air pressure inside the facility is kept lower than atmospheric pressure to prevent air leak from the facility. Monitoring systems are introduced to secure safe operation such as automatic shutoff of the facility when an earthquake strikes and exceeds a certain level of magnitude. Also an information-release room is set up to actively show the disposal processes and the operation status to the public.

Though the facility has come across various start-up difficulties, it is expected to make significant progress in PCB waste disposal measures and prevention of environmental pollution.