Selection of the flotation unit as part of the technology to implement integrated wastewater treatment at coal mining operations

Treatment of open-pit water from coal strip mines, which are characterized by large volumes of runoff water, low temperature and presence of hard-to-remove substances, i.e. sulphates, chlorides, nitrates and ammonium ions, which makes the choice of optimal water treatment technology much more difficult, is a complex engineering task. The stage of reagent treatment of the original runoff water is designed for thorough removal of the suspended and colloidal substances, petroleum products, phosphates and heavy metal compounds, in particular iron. Flotation is used for wastewater treatment in many industries to remove insoluble dispersed impurities, which are poorly settling on their own. The purpose of the study was to identify the optimal configuration and the operating mode of the flotation equipment to achieve the maximum efficiency of runoff water treatment at coal-mining operations. The article provides a detailed description of the operating principles of the flotation plants of different types for wastewater treatment at coal operations, as well as information on the results of the commercial tests in real operating conditions. A hybrid-type electro-flotation unit is recommended for wastewater treatment with the throughput capacity of up to 100 m3/h (the optimal plant should contain from 1 to 4 electroflotation units with the throughput capacity of 25 m3/h each). Pressure-type flotation units with the capacity of 50-100 m3/h are more appropriate for wastewater treatment with the discharge capacity exceeding 100 m3/h. Execution of tests helps to make reasonable technical and managerial decisions aimed at improving the quality of wastewater treatment and reducing the costs of the operation.