Zero discharge utilization of saline waters from “Wesola” coal-mine

A conception of comprehensive utilization of saline waters from “Wesola” coal-mine was proposed. There the water from level 665 m, that contains about 35.45 g/L Cl−, is pretreated by nanofiltration (NF) and then evaporated in twig towers while the water from level 465 m of about 2.25 g/L Cl− content is desalinated and simultaneously concentrated by electrodialysis (ED) with univalent permselective membranes. Partially evaporated twig tower brine and ED concentrate undergo further thermal evaporation to NaCl concentration up to 300 g/L and then evaporation with salt (NaCl) crystallization. The NF retentate and post-crystallization lyes are mixed with power station ashes and applied as a hydraulic filling in the mine. The profitability of comprehensive utilization was also estimated. The value of evaporated salt produced ($1.68 million per year) was found to be close to the total cost of utilization ($1.71 million per year). The decrease of charge paid for chloride and sulfate discharge (estimated as $3.45 million per year) was then considered as the utilization benefit, resulting in high economical efficiency of the proposed conception.