A method of treating a waste brine that includes sodium, sulfate and chloride and producing sulfate and chloride salt crystals, wherein the waste brine is produced by a coal-to-chemical or coal-to-liquid process, the method comprising: concentrating the waste brine; directing the concentrated waste brine to a Mirabilite crystallizer and producing via cooling crystallization hydrated sodium sulfate salt crystals and a chloride-rich brine stream; separating the hydrated sodium sulfate salt crystals from the chloride-rich brine stream; melting the hydrated sodium sulfate salt crystals to form an aqueous sodium sulfate solution or a slurry; directing the aqueous sodium sulfate solution or slurry to a sulfate crystallizer and crystallizing anhydrous sodium sulfate salts from the aqueous sodium sulfate solution or slurry to form sulfate salt crystals comprising sulfate and sodium and a mother liquor; recycling the mother liquor from the sulfate crystallizer to the Mirabilite crystallizer; removing sulfate and suspended solids from the chloride-rich brine stream produced by the Mirabilite crystallizer by directing the chloride-rich brine stream from the Mirabilite crystallizer through a nanofiltration device which produces a permeate stream and a reject stream containing the sulfate removed from the chloride-rich brine stream; directing the permeate stream from the nanofiltration device to a chloride crystallizer and producing chloride salt crystals comprising chloride and sodium; recycling the reject stream produced by the nanofiltration device to the Mirabilite crystallizer and mixing the reject stream with the waste brine directed into the Mirabilite crystallizer. concentrating the waste brine; directing the concentrated waste brine to a Mirabilite crystallizer and producing via cooling crystallization hydrated sodium sulfate salt crystals and a chloride-rich brine stream; separating the hydrated sodium sulfate salt crystals from the chloride-rich brine stream; melting the hydrated sodium sulfate salt crystals to form an aqueous sodium sulfate solution or a slurry; directing the aqueous sodium sulfate solution or slurry to a sulfate crystallizer and crystallizing anhydrous sodium sulfate salts from the aqueous sodium sulfate solution or slurry to form sulfate salt crystals comprising sulfate and sodium and a mother liquor; recycling the mother liquor from the sulfate crystallizer to the Mirabilite crystallizer; removing sulfate and suspended solids from the chloride-rich brine stream produced by the Mirabilite crystallizer by directing the chloride-rich brine stream from the Mirabilite crystallizer through a nanofiltration device which produces a permeate stream and a reject stream containing the sulfate removed from the chloride-rich brine stream; directing the permeate stream from the nanofiltration device to a chloride crystallizer and producing chloride salt crystals comprising chloride and sodium; recycling the reject stream produced by the nanofiltration device to the Mirabilite crystallizer and mixing the reject stream with the waste brine directed into the Mirabilite crystallizer. melting the hydrated sodium sulfate salt crystals to form an aqueous sodium sulfate solution or a slurry; directing the aqueous sodium sulfate solution or slurry to a sulfate crystallizer and crystallizing anhydrous sodium sulfate salts from the aqueous sodium sulfate solution or slurry to form sulfate salt crystals comprising sulfate and sodium and a mother liquor; recycling the mother liquor from the sulfate crystallizer to the Mirabilite crystallizer; removing sulfate and suspended solids from the chloride-rich brine stream produced by the Mirabilite crystallizer by directing the chloride-rich brine stream from the Mirabilite crystallizer through a nanofiltration device which produces a permeate stream and a reject stream containing the sulfate removed from the chloride-rich brine stream; directing the permeate stream from the nanofiltration device to a chloride crystallizer and producing chloride salt crystals comprising chloride and sodium; recycling the reject stream produced by the nanofiltration device to the Mirabilite crystallizer and mixing the reject stream with the waste brine directed into the Mirabilite crystallizer.