Improvement of the Mine Water Purification Efficiency via Modified Settling Tank

Coal mining technologies always lead to tremendous environmental pollution of air, water resources, lands and biodiversity, both in regional and global scale. The level of environmental safety and ecological quality of the coal-mining region significantly decreases due to mining operations. In particular, mine waters with solid particles and dissolved chemicals are discharged to surface reservoirs. The suspended substances of mine waters, both in solid and dissolved forms, pose a high threat for the ecological and chemical balance of natural waters. Due to the ability to adsorb heavy metals, they play a significant role in the pollution of nearby water bodies. Chemicals not only change the quality of water bodies, but also pose an increased environmental risk to aquatic organisms and the health of the population. The purpose of the paper was to revise the mine water drainage technological scheme of the "Stepova" coal mine, as the subdivision of the "DTEK Pavlogradvugillya" Public Joint-Stock Company (Ukraine), and justify the technical considerations concerning implementation of a horizontal settling tank with unique design. It is justified that such mechanical treatment facility with vertical perforated partitions will significantly improve the overall water quality and provide further treatment in the storage pond. The modeling of the mine water purification process for the conditions of the "Stepova" coal mine was carried out due to the investigation of the kinetics of suspended particles precipitation simulated under laboratory conditions. The obtained dependences allow selecting the most optimal design and technological parameters of the proposed settling tank of advanced design. The values of the expected technological parameters of the proposed settling tank were determined, namely the predicted value of mine water purification efficiency, approximate depth of particles sedimentation in the point of treated water removal from the settling tank, and the hydraulic size of suspended solids. It was established that the implementation of the proposed technological scheme of mine water purification will reduce the concentration of suspended solids to the normative concentrations allowed for discharge into surface water bodies.