Water quality changes of a closed underground coal mine in Korea

Abstract

The objective of this study was to assess the changes in mine water quality as an underground mine flooded from July 2005 to October 2008. The effect of air injection with a blower into the water was used to evaluate the potential to convert ferrous to ferric iron and to provide in situ treatment and precipitation. Mine flooding averaged 31 cm/day with a linear shape until November 2007, when it flattened out due to outflow. During flooding, mine water pH remained around 6, but Eh shifted from 200 to -150 mV. After the mine water level stabilized, contents of elements such as Fe and SO(4) tended to decrease as time passed. Air was injected by diffusers (150 L/min/each) at three different depths of 2, 3, and 5 m below the water level in the shaft. Dissolved oxygen eventually increased to 4 or 5 mg/L depending on the depth of the diffusers. Aeration caused conversion of ferrous iron to ferric iron and about 30 mg/l of iron was removed from the mine water. Therefore, air injection shows potential as a semi-active treatment or part of conventional treatment to precipitate iron in the mine pool.

SIMPL: A Simplified Model-Based Program for the Analysis and Visualization of Groundwater Rebound in Abandoned Mines to Prevent Contamination of Water and Soils by Acid Mine Drainage

“…In this study, the Dongwon, Samtan, Sewon, Jeongdong, and Hamtae coal mining areas located in the Gohan/Sabuk district are used as study areas to test whether SIMPL can be applied to relatively extensive abandoned coal mine sites ( Figure 8 ). The groundwater rebound phenomenon in the shaft of the Dongwon coal mine was analyzed; here, changes in the intra-pit groundwater level and water quality have been monitored since 2005, as reported by Cheong et al [ 24 ].…”

“…The SIMPL simulation result was somewhat lower than the field monitoring result from July 2005 until April 2006, but was a little higher from July 2006 until November 2007; however, these differences were not large. After the groundwater level reached 639 m in November 2007, the increase in groundwater level slowed down, a result of groundwater flowing out to the surface at the 639 m point through cracks in the strata [ 24 ]; this is also seen in the field monitoring data. This Dongwon coal mine case study confirms that SIMPL can be successfully used for groundwater rebound prediction for extensive areas of abandoned mines.…”