Mine water quality variation during the overhaul of fully mechanized mining equipment in Shenfu mining area

The ecological environment is fragile and the water resources are scarce at Shenfu mining area in the Ordos Basin. Mine water is an important unconventional water resource. However, the various pollution components produced during the underground mining process have greatly limited the reuse of mine water. The working face is the main source of pollution components, especially during the overhaul of fully mechanized mining equipment. In order to find out the release law of pollutant components during the overhaul process of the fully mechanized mining equipment in the working face, a field experimental study on the variation of mine water quality at this stage was carried out. The result showed that long term water-rock interaction caused a high concentration TDS (>1 000 mg/L) of groundwater in the coal seam roof aquifer. The groundwater was mixed with a low concentration TDS of used water during the period of fully mechanized coal mining equipment maintenance and mining. The concentration was 1 296.0-1 316.0 mg/L TDS of mine water, and the concentration of SO4 2- decreased by 28.0-48.0 mg/L. Human activity discharged some pollutants (e.g. NH4 + and Escherichia coli) to mine water, and nitrification increased the concentration of nitrate (1.12-1.97 mg/L) in mine water of the mined out face and prior to equipment maintenance. The concentrations of oxygen consumption, TOC and UV254 obviously increased with fully mechanized coal mining equipment maintenance. Three-dimensional excitation-emission matrix fluorescence spectroscopy (3DEEMs) showed that main organic matters were tyrosine like and tryptophan like from human activity and coal dissolving. Polycyclic aromatic hydrocarbons and petroleum pollutants were main organic matters during fully mechanized mining equipment maintenance, and the fluorescence intensities were very high. Finally, there were some organic matters from human activity, equipment oil and coal during coal mining, but the fluorescence intensities were lower. In a word, a fully mechanized mining equipment maintenance caused a high concentration of many contaminations (especially organic matter).Good pollution control would help reducing the concentration of pollutants and the cost of mine water treatment. © 2019, Editorial Office of Journal of China Coal Society. All right reserved.