Disclosed are wastewater treatment systems and methods for semiconductor fabrication process. The method comprises performing first concentration on wastewater discharged from a semiconductor process chamber, and performing second concentration on concentrated wastewater or at least a portion of the wastewater concentrated by the first concentration. The step of performing the first concentration includes performing in a first electrodialysis apparatus an ion exchange between the wastewater and first treatment water. The step of performing the second concentration includes allowing the concentrated wastewater to circulate in a second electrodialysis apparatus, allowing second treatment water to circulate in the second electrodialysis apparatus, providing a power to an anode and a cathode of the second electrodialysis apparatus to perform an ion exchange between the second treatment water and the concentrated wastewater, and joining a portion of the concentrated wastewater to the second treatment water.

A method of reducing activity of sulfur and/or nitrogen metabolizing bacteria is provided. The method includes adding a composition of an alkali metal salt of chlorite and/or an alkali metal salt of chlorate and hydrogen peroxide to process water of a cooling tower and increasing a concentration of the composition from about 0 ppm to about 300 ppm in about 1 to about 100 minutes.