BIOREMEDIATION OF COAL CONTAMINATED SOIL AS THE ROAD FOUNDATIONS LAYER

Abstract

Waste area ex-coal mining land is left without proper management and utilization. After analysis, ex-mining land material can be reused as road construction material by increasing mechanical properties. Microbial-induced calcite precipitation (MICP) is a soil improvement technique using microorganisms capable of altering and enhancing their mechanical and physical properties. In this study, an unconfined compressive test was used to see the effect of calcite precipitation on the behavior of the unconfined compressive strength of sand contaminated with coal. Variations in the concentration of Bacillus subtilis were applied as much as 3%, 4.5%, and 6% on sand contaminated with coal. The bacteria used were 3 days of culture was still in the stationary phase and 6 days of culture in the dead phase. After 28 days of curing, there is a significant increase in the UCS values of the MICP-stabilized soil compared to the untreated soil. The use of 3 days of bacterial culture was more effective in increasing the UCS value than 6 days of culture. At optimum conditions, the UCS value increased up to 15 times after the 28-day curing period. As a conclusion the ex-mining land material after treated with MICP using Bacillus subtilis, it can be reused and qualifies as a road construction material