METHOD FOR CONTROLLING WASTE LIQUID CONCENTRATION OF TREATING LIQUID CONTAINING P

PROBLEM TO BE SOLVED: To prevent a waste liquid with a high concentration of P and a large amount of P-containing waste liquid from being fed to waste water disposal facilities and to prevent the operation from being suspended by the incapability of feeding waste liquid with a higher concentration of P to the waste water disposal facilities when materials to be treated are treated by using a treating liquid containing P. SOLUTION: A waste liquid buffer tank capable of feeding the waste liquid to, or storing in, the waste water disposal facilities after receiving the waste liquid of the treating liquid containing P is provided to treat the materials to be treated by keeping the concentration of the treating liquid containing P in a range of a target concentration. When a value of the concentration of P in the waste liquid of the treating water containing P measured in the waste liquid buffer tank does not exceed the allowable limit, the waste liquid of the treating liquid containing P is fed from the waste liquid buffer tank to the waste water disposal facilities. When the measured value of the concentration of P exceeds the allowable upper limit, the waste liquid of the treating liquid containing P is suspended from the feed to the waste liquid disposal facilities, and is stored in the waste liquid buffer tank, until the concentration of P in the waste liquid of the treating liquid containing P is lowered to the value in a range of the target concentration so as to restart treating the materials to be treated. COPYRIGHT: (C)2009,JPO&INPIT