POLYCHLORINATED BIPHENYLS (PCB's) - Environmental Implications

HAZARDOUS PCB's WASTE - HANDLING, TREATMENT & DISPOSAL

The PCB's waste requiring disposal mainly consist of:
  • Waste arising during the manufacturer / use of PCB's - both solids and liquids.
  • Dielectric fluid removed from transformers because of degradation and contamination
  • Dielectric fluid in scrapped transformers
  • Dielectric of scrapped capacitors in manufacture and in redundant equipment
  • PCB's contaminated material e.g. scrap capacitors, windings, absorbent material used in cleaning equipment or spills - Imported Waste.
PCB's Waste from its major uses

(a) Transformers

The PCB's have been used in transformers since 1940 because of their high boiling points, stability, non-flammability and dielectric characteristics. The adequate disposal of transformers dielectric fluid should be mandatory in order to escape from environmental consequences. PCB's filled transformers are principally used, where the consequence of fire from ignition of the dielectric due to arcing or from an external source would be serious e.g. in ships, basement of buildings and mines. However, the dense fumes, which are evolved when PCB's are subjected to high temperature makes them unacceptable in some situations. The rejected dielectric and scraped transformer contribute the PCB's waste to the environment.

(b) Capacitors

The capacitors are used to smooth out the large load fluctuations on industrial power supply systems. The lower chlorinated PCB's are used in large capacitors. Even in small electrical gadgets, the small PCB's filled capacitors are fitted particularly in fractional horse power motors used in domestic and light industrial electrical equipment. Typically these contain lower chlorinated PCB's mainly absorbed on the windings. The PCB's waste in these application arises, when the equipment is scrapped, capacitors replaced and during manufacture of capacitors. In present time, there have been considerable reduction of PCB's used in the capacitors.

PCB's Waste Treatment and Disposal Methods Adopted in Various Countries

The method of treatment and disposal of PCB's waste as adopted in various countries involve mainly following methods.

A. Incineration
Most of the PCB waste generated are destroyed by controlled incineration in the units fitted with wet gas scrubbing systems capable of achieving sustained temperature of 11000C. The waste disposal by this method is used particularly for following processes:

  • Liquid waste from manufacturing process and from transformers and large capacitors
  • Solid waste from manufacturing process usually cast in drums.
  • Miscellaneous solid waste including waste from manufacture of small capacitors, contaminated rags, saw dust, fuller's earth etc. at manufacturing and handling plants.
B. Heat Treatment
Certain PCB's wastes are subjected to varying degree of heat treatment in some countries. These are principally associated with scrap, small capacitors, which are recovered from domestic waste. The capacitors shell of aluminium are separated but the separation process is not completely effective and some PCB's associated with it finds its way into the scrap, which is destroyed at higher temperature during scrap melting. During the heat treatment process some PCB's escape to the atmosphere, though in diluted form.

C. Landfill
In several countries, small capacitors scrap arising from use in starter circuits, fractional horsepower electric motor application is disposed to landfill or in redundant appliances. One of the main routes is via the domestic refuse, which is taken for landfill, and the item is buried at the bottom of layer of refuse, if not recycled. Small quantities of contaminated rags, paper, sawdust etc. arising at manufacturing and handling plant also reach to the landfill.

D. Recovery
The PCB's waste principally from transformer applications and also from large capacitors is recovered by clarification and vacuum distillation process. In large capacitors, the excess fluid is drained off for recovery and incineration.

E. Other disposal method
The PCB's waste in some countries are stored isolatedly, pending the availability of acceptable disposal method and accumulated backlog is still largely dealt with incineration.
Recommendations for Proper Handling and Disposal of PCB's Waste

a. Labelling of Products and Wastes

Modern Electric transformers and large capacitors containing PCB's should be identified with labels, informing buyers the need for adequate disposal. The manufacturer should undertake retrospective labelling, wherever possible. The strict maintenance procedure for PCB's filled units are required in comparison to units filled with hydrocarbon oils.

b. Storage and Containment

The bulk liquid PCB's and waste liquid PCB's must be adequately sealed and well labelled and stored in heavy duty containers, but not in standard drums. In case of highly chlorinated type of PCB's used in transformers, appropriate labelling should be used by the manufacturers. The PCB's for reclamation from PCB's based material should be stored in sealed containers to avoid contamination of external environment

c. Handling

Appropriate housekeeping is mandatory, when PCB's are utilized for any product manufacture. The transfer of liquid PCB's should have to be appropriately conducted to ensure, that it should not be a residual source of pollution.

Where large quantities of PCB's are still used, the bunds, dump tanks should be provided to prevent PCB's passing into the drains, if the dielectric fluid is mishandled. Strict precautions should be taken to ensure that PCB's do not enter into sewerage system or watercourse particularly from old disused transformer dump yard or storage place.