| abstract |
The objective of the present invention, in addition to avoiding a problem of discharging phosphorous included in RO membrane concentrated water, is to improve and stabilize water recovery rate when performing RO membrane treatment and water recovery for discharged cooling water, such as blow water, of a circulating cooling water system. Water discharged from the circulating cooling water system is treated by a water recovery system comprising clarification equipment and an RO membrane, and during water recovery, wherein treated water is returned to the circulating cooling water system, a substance which passes through the clarification equipment and includes a polymer comprising a carboxyl group having a weight average molecular weight of 5,000 or less is added to the circulating cooling water system and used as a dispersing agent for dispersing scale components. The polymer comprising a carboxyl group having a weight average molecular weight of 5,000 or less passes through the clarification equipment and, as a scale dispersing agent for the RO membrane, can suppress precipitation of scale. Since the polymer intrinsically has an anticorrosion effect, it becomes unnecessary to add a phosphoric acid compound to the cooling water system as an anticorrosion agent, or the required amount of the compound to be added can be minimized, thereby suppressing an increase in phosphorous concentration in the RO membrane concentrated water. |