Utilization of Bottom Ash for Clay Mine Rehabilitation

At the end of mining activities, clay mines were abandoned due to the cost and non-availability of filling materials. These abandoned clay mines cause adverse environmental and social impacts. In addition, large quantities of bottom ash (BA) are generated as a by-product of coal combustion process. This BA is disposed by open dumping in the lands, which creates severe environmental pollution. Therefore, conducted research on utilization of BA for mine rehabilitation is beneficial. The main focus of this research is applicability of BA generated from Lakvijaya power plant, Sri Lanka as a potential backfill material and a soil amendment during the clay mine rehabilitation. Initially tests were conducted to investigate the basic properties of BA. Next, chemical composition of BA was analysed to select the suitable crops for vegetation. Further pH, electrical conductivity and water holding capacity were checked and micro structural morphology of BA was determined through Scanning Electron Microscope. The results showed that BA has good engineering properties and the potential to improve agronomic characteristics of soil. It has better water holding capacity and permeability. BA can adjust soil pH to a desirable plant growth range. As BA has a very porous structure, the root system can easily develop and helps to uptake nutrients by the plant. However, a considerable percentage of trace metals is accumulated in BA which will increase the bioavailability of some trace metals to levels that poses risk to human. Thus, investigations were carried out to identify the heavy metal concentration in leachate of BA using column leaching test. Results showed that leachability potential of trace metals in BA does not exceed the allowable limits.