ASSESSMENT OF EX-MINED POOL WATER QUALITY PIT L1 AND PIT E1 WITH APPROACH CATCHMENT AREA IN LATI MINE OPERATION PT. BERAU COAL

• Main Author: Medy Tandy, Lia
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/56769
• Institution: Institut Teknologi Bandung

Acid mine drainage (AMD), or acid rock drainage (ARD), is acid water which is produced from mining activity that has high acidity and was formed from oxidation process of sulphide minerals along with the presence of water. The source of the acidity is coming from sulphide minerals oxidation process. Oxygen acts as an oxidizing agent. Not only as one of the reactant in AMD generation, but water also flush the dissolving of the oxidation process. The water source can be a runoff or groundwater. In this condition, the oxidized sulphide minerals will release acid (H+) into water that causes the water to be acidic (low pH). Decreasing pH will cause. PT. Berau Coal is one of the company in coal mining that use open pit mining method. Pit L1 and Pit E1 has completed be mined and became a huge void which is full of acid water (range of pH in Pit L1 is 3.09-3.15 and in Pit E1 is 3.36). the main water source is coming from runoff which has pH of 6.08. In the previous study, analysis of the catchment area and water balance in the respective pit has been conducted and the result in the range of two years (2012 – 2014) showed that from the 58.73 Ha disturbed area in the Pit L1, revegetation are that naturally occurs was 12.09 Ha or about 14% and in the Pit E1, there was no revegetation occur from 4.9 Ha of the disturbed area. From the water balance analysis, it showed that the volume of the water that filled the pit lake L1 was about 1.321.453 m3 which is overfilled the pit volume capacity (about 1.265.283 m3), and the same case occur in pit E1, the volume of the water that filled pit lake E1 was about 70.744 m3 and the pit capacity was 22.974 m3. From this study, it can be concluded that water that goes into each pit has exceeded the ability of the lake capacity so that there was a surplus or excess water of 56 170 m3 in the Pit lake L1and 47 770 m3 in Pit lake E1. The purpose of this study is to know whether catchment area approach and water balance analysis which is done in the previous study give effect to the water quality in 2012 and 2014 in each pit. The simulation of the final water quality change will be conducted using PHREEQC Interactive Software to explain any minerals that play a role in the acid mine drainage generation of each pit. Primary data was obtained from field measuring of the pit water and laboratory analysis. Besides that, secondary data from the previous study (Novita, 2012 dan Elsyamba, 2014) will be used. In this study, data of the minerals in the previous study as a result of inverse modeling (Novita, 2012 dan Elsyamba, 2014) will be used as an input in the inverse modeling simulation in PHREEQC to examine further about water quality change in each pit. Output from this simulation is a reaction model which is close to the previous result and pH value is in the representative value from each pit, 3.16 in Pit L1 and 3.68 in Pit E1. The results from this forward modeling show that the water quality is not significantly better because pH value in Pit Lake L1 is about 4.31 and in Pit Lake E1 is 3.70.