Environmental Impact Assessment of Lignite Fly Ash and Its Utilization Products as Recycled Hazardous Wastes on Surface and Ground Water Quality
Combustion residues, such as alkaline lignite fly ashes, are produced worldwide in ever-increasing quantities. Combustion residues, however, may pollute the environment because they are enriched in potentially toxic elements relative to soils and sediments. For a proper assessment of the environmental impact of the utilisation and disposal of the ash it is necessary to understand the effect of the mobilisation of potentially hazardous elements from ash residues. Trace metals, though present as a relatively small fraction in fly ash, are of special interest, due to their cumulative build up, long life, and high toxicity to man, plants, and animals. Since trace elements existing in fly ash can leach out and contaminate soil as well as surface and groundwater resources, their study has recently been regarded as important in connection with the protection of the environment.
The management of fly ash produced by coal fired power plants remains a major problem in many parts of the world. Although significant quantities are being used in a range of applications and particularly as a substitute for cement in concrete, large amounts are not used which requires disposal. Those quantities are disposed sometimes on unlined landfills. The original ash contains certain amounts of toxic elements and heavy metals. Such material, if inadequately deposited, can produce surface and ground water leachate pollution.
Uses of fly ash have included the manufacture of lightweight aggregate, road base construction, landfill liners, sewage sludge treatment, as a filler in plastic composite materials, as well as the manufacture of Portland cement, etc. The use of fly ash in the ceramics industry and particularly as a component in the manufacture of bricks and tiles has also been investigated. This industry uses large volumes of silicate-based raw materials and therefore has the potential to utilize significant amounts of fly ash. Research is therefore needed to develop new alternative applications that can further exploit fly ash, which needs to be increasingly regarded as a raw material with a potential for processing into new products rather than a waste.
Samples of lignite fly ash from the thermal power plant "Nikola Tesla" (Serbia) were investigated in the Case Study. Sintering, as a method of fly ash recycling, reduces leaching concentrations of elements. Special attention was paid to the determination of leaching properties by the Generalized Acid Neutralizing Capacity Procedure (GANC). Results of the analysis emphasise that the fly ash samples sintered at different temperatures have much lower leaching concentrations than the raw fly ash samples.
Unable to display preview. Download preview PDF.