Patent ID: 8435413
Filing Date: 2013-05-07
Classification: C02F,C22B,Y02P

Abstract:
1. A method for controlling the concentration of phosphorus (P) in cleaning solution waste water comprising: providing a waste water buffer tank which, after receiving cleaning solution waste water containing P obtained from a treatment liquid containing P, sends the waste water to a waste water treatment plant or stores the waste water; setting upper and lower liquid levels of the cleaning solution waste water in the waste water buffer tank and setting the concentration of P in the cleaning solution waste water within a target concentration range; measuring the concentration of P in the cleaning solution waste water containing P in the waste water buffer tank; sending the cleaning solution waste water containing P from the waste water buffer tank to the waste water treatment plant when the measured value of the P concentration is less than a selected upper limit; stopping flow of the cleaning solution waste water containing P to the waste water treatment plant when the concentration of P is higher than the selected upper limit; storing the waste water in the waste water buffer tank; and controlling the liquid level of cleaning solution waste water in the waste water buffer tank while reducing the concentration of P in the cleaning solution waste water in the waste water buffer tank to a value within the target concentration range when the measured value of the P concentration of the cleaning solution waste water is higher than the selected upper limit by reducing a set value of a concentration of P in the treatment liquid containing P.