Abstract: The ultrapure water producing system produces ultrapure water with high purity and remarkably low content of metals even just after restart of operation thereof. Water sent through the pump 3 or 4 into a line 8 flows through a heat exchanger 10, a line 12, a UV oxidation apparatus 20, a line 22, an ion exchange device 30, a line 32 and a membrane filtering device 40 and is treated in each device in this order to be ultrapure water. The devices 10, 20, 30, 40 have bypass lines 11, 21, 31, 41, respectively. In the sterilizing process, bactericide water is fed only to the membrane filtering device 40 via the bypass lines 11, 21 and 31. In the following sterilizing process of the heat exchanger 10 and the UV oxidation apparatus 20, the bactericide water flows the line 41 bypassing around the membrane filtering device 40.

Abstract: The ultrapure water producing system produces ultrapure water with high purity and remarkably low content of metals even just after restart of operation thereof. Water sent through the pump 3 or 4 into a line 8 flows through a heat exchanger 10, a line 12, a UV oxidation apparatus 20, a line 22, an ion exchange device 30, a line 32 and a membrane filtering device 40 and is treated in each device in this order to be ultrapure water. The devices 10, 20, 30, 40 have bypass lines 11, 21, 31, 41, respectively. In the sterilizing process, bactericide water is fed only to the membrane filtering device 40 via the bypass lines 11, 21 and 31. In the following sterilizing process of the heat exchanger 10 and the UV oxidation apparatus 20, the bactericide water flows the line 41 bypassing around the membrane filtering device 40.

Abstract: A polishing agent recovery and reuse method and device for the same removes large impurities by a filtration device, concentrates by an ultrafiltration device, and continuously recovers polishing agent. Polishing agent used in polishing a semiconductor board or a coating formed on top of a semiconductor board is collected in a pre-processing container after use. Large impurities are removed by a dual fine filtration device. The resulting filtrate is concentrated by an ultrafiltration device. The concentrated solution may then be mixed with filtrate from the dual fine filtration device to further concentrate the polishing agent. The concentration of the polishing agent in the concentrated solution, the pH, and the temperature of the solution are continuously monitored and controlled. The filtrate of the ultrafiltration device is further treated to remove impurities, resulting in pure or ultrapure water. The recovered polishing agent may be reused in further polishing steps.