For effective-management and disposal of hazardous waste, waste classification is an essential pre-requisite. Generally, the following approaches have been followed internationally to classify the hazardous wastes :

  1. Listing by source approach
  2. Listing by pure component approach
  3. Criteria approach
  4. Exclusive list approach

Listing by Source Approach

There are certain activities which lead to the generation of hazardous wastes. In this system of classification, the wastes have been identified on the basis of their source of generation.

Listing by Pure Component Approach

As per this method, the wastes have been classified as hazardous based on the toxic and hazardous constituents present in the waste. A list of hazardous wastes which contain toxic and hazardous constituents is given in Appendix I. There are 35 generic types of wastes based on the toxic and hazardous constituents present in the waste.

Criteria Approach

Normally, a chemical or a compound does not exist in pure form in the waste. A waste is generally a complex mixture of different chemicals and/or compounds which exhibit certain properties. In this system of waste classification, the wastes exhibiting the following characteristics have been classified as hazardous wastes :

  1. Ignitability, e.g., hydrocarbons
  2. Reactivity, e.g., nitrates, chromates and permanganates
  3. Corrosively, e.g., acids and alkalis
  4. Toxicity, e.g., pesticides, lead, arsenic or cadmium compounds
  5. EP-Toxicity, e.g., radioactive wastes.

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Most of the countries follow a combination of these approaches in classifying and identifying their hazardous wastes. For example. United States of America, United Kingdom, West Germany etc., have adopted a combination of Listing by Source and Criteria approaches. Norway has adopted the Listing by Pure Component approach.

Recently, Government of India has passed rules for the Management of Toxic and Hazardous Wastes. In our country, the combination of Listing by Pure Component and Source has been adopted in identifying the hazardous wastes. The list of hazardous wastes, identified by the Government of India is given in Appendix II.

Exclusive List Approach

In listing by exclusion approach, the chemical wastes which cause no harm to human health, environmental quality and life, in general are listed by intuition. The waste chemicals which do not fall under this category have been designated as hazardous. This method of classifying the wastes is arbitrary because it results from the subjective opinion of the person classifying the wastes. Thus, it is not a good method of classification.