| 摘要 |
PROBLEM TO BE SOLVED: To prevent a lowering of membrane flux by a method wherein when a normal-wastewater treatment is changed over to an abnormal-wastewater treatment, pH of coagulation treatment is adjusted to a specific value, and when pH of water supplied to a membrane separation device becomes a specific value, an adjustment is made so that the concentration of ferrous ions of water becomes a specific value or higher. SOLUTION: Wastewater of a thermoelectric power plant is introduced into a coagulation reaction tank 1 so as to be subjected to a coagulation treatment under conditions that pH adjusting agents and flocculants are added to the wastewater, and the resulting coagulated liquid is led to a membrane separation device 3 through a circulation tank 2 to obtain treated water. In such treatment method, when a treatment in which wastewater of the power plant contains relatively small amount of primary ferrous ions is changed over to a treatment in which the wastewater contains relatively large amount of primary ferrous ions, pH of coagulation treatment is adjusted to 8-9. And when pH of water supplied to the device 3 becomes 8-9, an adjustment is made so that the concentration of primary ferrous ions of water becomes 100 mg/L or more. Thus membrane flux can be prevented from falling. |
