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Solidification
Preventing Hazardous Heavy Metals from Leaching Into the Environment
Inorganic wastes, which do not fulfill the criteria for disposal directly into the Secured Landfill, are treated in the Solidification Plant. Such wastes are typically metal hydroxide sludge containing heavy metals such as arsenic, barium, boron, cadmium, chromium copper, lead, mercury, nickel, selenium, silver, tin and zinc.
During the solidification process the heavy metals become insoluble and the wastes therefore can safely be disposed off in the Secured Landfill. Fly ash from the Incinerator Plant and sludge from the PCT Plant are also treated at the Solidification Plant.
At the Solidification Plant, waste is loaded into waste preparation bunkers, where it will be mixed with other similar waste. It is then loaded into the waste hopper before being transferred to the mixer by screw conveyors. In the mixer, waste is carefully mixed with consumables such as cement, lime, sand and water. |
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After treatment, the waste will appear as a concrete mixture. The mixture is disposed off to the secured landfill for the final curing over a few days. The objective of the whole process is to fix all the heavy metals in the inorganic solid waste into a concrete/silica matrix for long-term disposal in the secured landfill. As a result, hazardous heavy metals will not leach out to the environment. |
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Types of Waste
Typical waste and their DOE code numbers treated are:- |
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| SW 310 |
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Sludge from mineral oil storage tank |
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| SW 204 |
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Sludges containing one or several metals including chromium, copper, nickel, zinc, lead, cadmium, aluminium, tin, vanadium and berrylium |
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| SW 106 |
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Residues from recovery of acid pickling liquor |
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| SW 204 |
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Sludges containing one or several metals including chromium, copper, nickel, zinc, lead, cadmium, aluminium, tin, vanadium and berrylium |
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