Abstract
It is not uncommon for mining activity to generate wastes associated with negative engineering impacts include susceptibility to runoff due to the absence of vegetation, erosion, and sinkhole. Due to their high degree of permeability, movement of heavy metal contaminants in waste soils and aquifers occurs actively along with the hydrogeological parameters, and research on using biocementation methods such as enzyme induced calcite precipitation (EICP) to reduce the hydraulic conductivity is therefore beneficial. Mine waste soil collected from a copper mine in Lohan Dam, Sabah is characterized physically, morphologically, and chemically then treated with EICP under different operational parameters include curing duration (1,3,7 days), curing temperatures (5, 10, and 25 oC ), and relative density (70 and 80 %). The hydraulic conductivity was then tested using a constant head permeability test and the calcium carbonate content (%) is determined using the HCL washing method. Properties of the Lohan Dam wastes are found to be predominantly coarse grain soil of low plasticity, high specific gravity, high permeability, acidic in nature, and low organic content. Morphologically, they are composed of powdered and hardened particles with dark brown color with high amount of irregular-shaped particles. Mineralogical, Lohan Dam soil wastes contain a high level of heavy metals beyond the safety level of the Department of Environmental Malaysia. EICP treatment had to change the degree of permeability from ‘high and medium’ to ‘low’ with a 94-97% reduction in hydraulic conductivity corresponding to the amount of calcium carbonate content produced ranging 6.94-9.63%. In conclusion, relative density shows the marginal effect, curing duration, and temperature shows a more significant impact on the treatment effectiveness.
Highlights
The mining process generates a large number of inert materials but the presence of toxic heavy metals such as mercury, arsenic, lead, zinc, cadmium is not uncommon
This paper reports the investigation of the performance of enzymeinduced calcite precipitation (EICP) in terms of reduction of the hydraulic conductivity of heavy-metal contaminated mine waste and the calcium carbonate content is produced
The mine wastes were classified based on their particle size, particle distribution, and texture using two major classification systems; Association of State Highway and Transport Officials (AASHTO) and Unified Soil Classification System (USCS)
Summary
The mining process generates a large number of inert materials but the presence of toxic heavy metals such as mercury, arsenic, lead, zinc, cadmium is not uncommon. Hazardous chemicals may present naturally or due to addition during the extraction process. The potential threat of these contaminants to the environment sustainability may include alteration of soil composition and threatening the quality of water supply and groundwater. Negative engineering impacts include susceptibility to runoff due to the absence of vegetation, erosion, and sinkhole due to highly permeable soil, and landslide due to unstable grounds, which may increase because of the debilitated properties of soil. As the movement of contaminants especially in soils and aquifers often occurs along with the hydrogeological parameters, study on remedial methods such as biocementation using enzymeinduced calcite precipitation (EICP) is necessary. Since EICP is considered relatively new, more inventive, and environmentally sustainable compared to the other methods, a wider application of this technique in geotechnical engineering should be explored
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