ANALYSIS OF FLY ASH PERFORMANCE AS A LAYERING MATERIAL POTENTIAL ACID FORMING USING COLUMN TEST AND FIELD DUMPING TEST

• Main Author: Harnanda, Suriandi
• Format: Theses
• Language: Indonesia
• Subjects: Pertambangan dan operasi berkaitan
• Online Access: https://digilib.itb.ac.id/gdl/view/69681
• Institution: Institut Teknologi Bandung

Acid mine drainage (AMD) is generated due to the oxidation of sulfide minerals accompanied by the presence of water and air. AMD that has already entered the environment can damage the aquatic ecosystem due to low pH and high concentrations of dissolved metal. The efforts to prevent the AMD generation is by covering Potential Acid Forming materials (PAF) with Non-Acid Forming (NAF) materials to avoid oxidation of sulfide minerals. To resolve the limitation of NAF material in the field, the use of fly ash which resulted from coal combustion in steam power plants as layering material can be used as an alternative. This study aimsto determine the performance of fly ash as a layering material using column tests and field tests in preventing the formation of AMD. The columns test were carried out on a laboratory scale and pilot scale with a ratio of fly ash uses as layering material of 5%, 15 %, and 25%, as well an additional column for laboratory tests with a ratio of 35%, 50%, and 60%, while on the pilot test, a layering scenario of fly ash and topsoil was placed with a thickness of 90 cm and 30 cm, respectifully, above the 30 cm thickness of PAF material. In each layer, the oxygen and water content sensors are installed to monitor the temporal changes. The results showed that in the column test with the layering scenarios, the geochemical material can not maintain the quality of the leachate to be non-acidic with an average pH 2,66 – 2,76. This is due to the condition of the layering material which relies on the physical properties of fly ash to prevent the diffusion of oxygen to a certain level was not achieved, thus the AMD is still generated. However, the addition of fly ash on the column test showed an ability to reduce the oxidation rate, because from the observation, the concentration of sulfate and dissolved metal was decreased. In the pilot test which the fly ash layer was thicker, the physical effect of layering fly ash in the role of preventing oxygen diffusion becomes significant so that AMD is not generated and resulted a leachate water with an average pH of 8,90. The results indicated that the use of fly ash as layering material with consideration of its physical and geochemical characteristics must be analysed as a whole to determine the effective performance of fly ash to prevent AMD.