Artisanal and small-scale gold mining (ASGM) in Indonesia still uses mercury in amalgamation process to extract gold form the ores. The process easily produces gold but at the same time produces very dangerous mercury waste. In this study, a comprehensive series of tests were carried out on amalgamation tailings from the ASGM in Sekotong area, West Nusa Tenggara. The tailings contain mercury up to 150 ppm, above the safe threshold, and gold up to 20 ppm which is intended to be recovered. Furthermore, mineral liberation analysis (MLA) and gravity recoverable gold (GRG) test were performed to determine the feasibility of recovering gold from the tailings. The liberation degree of the gold started from particle size of 37 \xm causes challenging to recover it. However, the GRG test confirmed that the gold was still feasible to be recovered by gravity concentration.

Recently Indonesia is conducting Underground Coal Gasification (UCG) project in South Sumatra for power generation.The potential of negative impacts from UCG on groundwater and the broader environment can not be ignored since past similar projects were often confronted with pollution isues of BTEX and PAHs due to condensation of tar-loaded gas. This study focuses on finding indigenous microorganisms capable of BTEX degradation and evaluate their biodegradability. Several microorganisms were successfully isolated and screened. Pseudomonas putida and Bacillus cereus were chosen for this bioremediation study since the bacteria were predominant and highly viable on the screening test. The BTEX degradation has been studied in single component using single and mixed bacterial cultures in the concentration range of 250-500 ppm. The experimental results show that biodegradation of BTEX by P. putida ranged from 61.4-70.2% and by B.cereus ranging 63.9-74.7 % at initial BTEX concentration of 500 ppm.Meanwhile, consortium of both isolates has the highest percentage of BTEX biodegradation (67.8-79,8%) during 14 days of retention time.The findings reveal that indigenous bacteria of P. putida dan B. cereus exhibit the potential to be used for decontamination of BTEX as an anticipated mitigation for potential pollution coming from the UCG project.

The gasification of Coal has a potential for long term energy supply in the future by conversion of non-mineable coal seams to syngas for various industrial applications. However, recalcitrant aromatic compounds such as phenol, anthracene, and acenaphthene from UGC are potential to contaminate groundwater, soil and the broader environment. Therefore, the polluted environment required bioremediation. The purpose of this study was to determine the capability of Bacillus velezensis and Stenotropromonas maltophilia isolated from the area of Underground Coal Gasification (UCG) on biodegradation of phenol, anthracene, and acenaphthene in the single and mixed cultures. The degradation of pollutants in the concentration range of 250-500 ppm evaluated by measuring of the ability of bacteria to grow in single component supplemented mineral salt media, screening tests for hydrocarbon-degrading bacteria and biodegradation ability by gravimetric analysis method. The results showed biodegradability of phenol, anthracene, and acenaphthene at concentration 500 ppm after 14 days by S. maltophilia were 60,2%, 80,4%, and 82,5%. B. velezensis showed 79% of biodegradability of phenol, anthracene 79,8%, and acenaphthene 81,1%. The consortium of both isolates has the highest percentage of phenol, anthracene, and acenapthene biodegradation 83,4 %, 83, 53 % and 83,47 % respectively.

A large amount of Hg is used for gold extraction through the amalgamation process in the Mandailing Natal derived from artisanal and small-scale gold mining (ASGM) area located in the North Sumatera Province, Indonesia. The objective of this work was to characterize the potential contamination of total Hg in water, sediments, and soil in this ASGM area. Sampling was done in two locations in West Panyabungan and Huta Bargot Districts using grab sampling method. Results showed that accumulation of Hg in the studied soils and sediments was the highest, but Hg in aquatic solution was below the detection limit of the analytical method of the studied community wells and rivers. The highest concentration of Hg was found in the river sediments of the Saba Padang irrigation (1,63 mg/kg), and in the soil of the plantation area of Huta Bargot (1,62 mg/kg) respectively. These concentrations may pose a serious problem for aquatic and land life, related ecosystems, and human health. For further study, there is a need to study Hg availability in riverine biota to better understand the cycling of Hg in this ASGM area. Understanding the ecological impacts can assist in the prioritizing of impact mitigation efforts.