Preparation of Wastes for Disposal

Although it is far better to find uses for hazardous waste constituents and put them into a nonhazard-ous form, in the past, and even today, wastes were disposed of to the geosphere, usually in landfill. This requires treatment of wastes to get them into a form that is suitable for long-term disposal. 

Some wastes can be immobilized in thermoplastics, which are solids or semisolids that become liquefied at elevated temperatures and that cool to rigid but deformable forms. The thermoplastic material most used for this purpose is asphalt bitumen. 

Water-insoluble pozzolanic substances containing oxyanionic silicon such as SiO and usually reacted with calcium hydroxide are used for waste solidification. The most abundant and commonly used pozzolanic substance is fly ash from coal combustion. Other pozzolanic substances, which are usually waste products from various processes include flue dust and ground slag from blast furnaces. 

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