Classification of hazardous waste

There are four steps in the classification of a hazardous waste:

• Identification of the waste or waste stream as probably hazardous.
• Testing and analysis to determine the hazardous properties, characteristics and components of a waste. This will confirm whether the waste is hazardous or not.
• Classification and treatment in accordance with SABS Code 0228 "The Identification and Classification of Dangerous Substances and Goods".
• Analysis and Hazard Rating of the waste or its residue, in order to determine the Hazard Rating and the Minimum Requirements for disposal.

An additional step would be re-examination of an existing classification with the objective of possible delisting and reclassification. This would apply in cases where, because of pre-treatment, low concentration, low mobility or other applicable factors, waste can delist to a lower Hazard Rating.

Identification of a probably hazardous waste

It is possible to identify industries and processes, which are likely to generate hazardous waste. The first indication that a waste stream could be hazardous, therefore, can be the industrial activity, process or waste stream from which it arises.

Analysis to confirm that a waste is a hazardous waste

If it is probable that the waste is a hazardous waste, it must be tested for its properties and analysed for it's substances. These are then compared to the lists of characteristics, properties and substances in SABS Code 0228, the Basel Convention, and the Waste Classification Tables.

If the properties and substances of the waste are not listed in SABS Code 0228, but conform to the Basel Convention or one of the nine classes in the Code, the waste is probably a hazardous waste.

SABS Code 0228

SABS Code 0228: "The Identification and Classification of Dangerous Goods and Substances" is a system for classifying hazardous substances for transport purposes. In the Code, hazardous substances are given an identification number and divided into nine classes:

• Class 1  Explosives
• Class 2  Gases
• Class 3  Flammable liquids
• Class 4  Flammable solids
• Class 5  Oxidising substances and organic peroxides
• Class 6  Toxic and infectious substances
• Class 7  Radioactive substances
• Class 8  Corrosives
• Class 9  Other miscellaneous substances

The waste must be tested against the nine classes, to see into which class it falls (it may fall into more than one class). The Minimum Requirements for that class must then be complied with.

Hazardous waste treatment

In many cases, it will be a Minimum Requirement that the waste be treated to reduce its hazardousness. Exact treatment methods are not usually prescribed. These remain dependent upon the availability of facilities or on the suitability of treatment technologies.

Hazard Rating

The toxicity of the waste or the residue remaining after treatment must be determined before disposal. This is called Hazard Rating.

In Class 6 of SABS Code 0228, hazardous substances are given a danger rating for transport and divided into three danger groups. However, these danger groups only relate to the risk the substance poses to man during transport (mammalian toxicity or LD₅₀). Hazard Rating for disposal, on the other hand, also takes into account risk to the environment. For this reason, the LC₅₀ or acute ecotoxicity of a substance is used in addition to the LD_50.

The LC₅₀ is the concentration at which a substance would kill 50 per cent of organisms if it were disposed of directly into a body of water. If the concentration of the hazardous substance is only ten percent of the LC₅₀ it should have very little harmful effect on the aquatic organisms.

0,1 x LC₅₀ is therefore used to represent an Acceptable Risk Level.

To determine the Hazard Rating, the Estimated Environmental Concentration or EEC of the substance in the waste is calculated in grams disposed of per hectare per month multiplied by a factor of 0,66.

EEC (ppb) = g/ha/month x 0,66

The EEC is compared to the Acceptable Risk Level.

If the EEC is higher than the Acceptable Risk Level, then the waste remains in the originally classified Hazard Rating.

If the EEC is lower than the Acceptable Risk Level, the waste may delist to a lower Hazard Rating.

The EEC is used to determine the amount of a substance that can safely be disposed of per hectare per month at a landfill site.

The EEC is also used to determine the total amount of a hazardous substance that may be accepted at a certain landfill site, before it must close for that substance. This is termed the Total Load.