Waste that can not be incinerated, and which cannot go straight to the landfill, undergoes a process of stabilization before being disposed of.

This process of stabilization produces physical and/or chemical changes in the waste, modifying its nature so as to transform it into a product that can be safely disposed of in the landfill.

The process of stabilization ensures that:

• The migration of toxic components through the stabilized form of the waste is minimized if not eliminated.
• The toxicity or solubility of the contaminants in the waste is minimized if not eliminated.
• The waste cannot flow or become viscous at environment temperature.
• The waste is physically transformed so that it can be handled safely.
• All free liquids are eliminated.
• The waste is transformed so that it cannot become wind-borne.
• The mechanical resistance of the waste is increased.

The process itself entails adding bonding agents to the waste so as to limit the mobility or the toxicity of contaminants initially identified. Depending on the nature of the contaminants, the bonding agents and the technique employed, the stabilization of the waste is achieved by means of one or more of the following mechanisms: redox, precipitation, neutralization, chelation, adsorption, coagulation or agglutination, micro- or macro-encapsulation, structural changes, etc.

One of the main ways to stabilize waste is cementation. Bitumen or other bonding agents can also be used. The method and formula to be applied is determined beforehand at the Chemical Analysis Laboratory of the Plant.

When cement is used to stabilize waste, water and other ingredients in the correct proportion, according to the nature of the waste, are added to allow setting of the homogeneous mixture. The thus stabilized waste undergoes a series of tests to confirm that it meets every standard dictated for waste going into the landfill for final disposal.

Waste typically needing stabilization are:

• Waste from steel mills
• Sludge containing heavy metal hydroxides from electroplating industry
• Waste from battery production (sludge from lead smelting wash; battery shells)
• Waste from industrial processes (sludge from industrial water treatment)
• Heavy metals from the electronics industry
• Sludge containing heavy metals from metal plating industry
• Sludge containing pigment and other waste from paint factories
• Waste from non-ferrous metal industry (neutralization sludge)
• Sludge containing heavy metals form industrial effluents treatment plants