Method and device for treating saline wastewater

摘要

The present invention provides a method and device for treating saline wastewater, e.g., accompanying water from gas field drilling, the method and device making it possible to highly efficiently convert the saline wastewater into an effectively utilizable substance in high yield at low cost with reduced environmental burdens.Saline wastewater which contains sodium chloride is concentrated by separating water from the saline wastewater to thereby produce high-concentration saline wastewater. The high-concentration saline wastewater is introduced into the positive-electrode-side chamber of an electrolytic tank which includes a positive electrode and a negative electrode that have been separated by a semipermeable membrane that is permeable to sodium ions, and electrolysis is then conducted to yield sodium hydroxide in the high-concentration saline. This sodium hydroxide is brought into contact with a gas discharged from a gas-turbine power generator or engine power generator which has been disposed in order to obtain electric energy for operating either the plant from which the saline wastewater is discharged or the device for treating the saline wastewater, thereby obtaining an aqueous solution containing sodium carbonate and/or sodium hydrogen carbonate. The sodium carbonate and/or sodium hydrogen carbonate is separated and recovered from this aqueous solution.