PURPOSE: To maintain the aerobic conditions for biological membranes to make satisfactory activation and to reduce the costs of maintenance and control by multiplying the amt. of satd. dissolved oxygen at the raw water temp. in a biological oxidation tank by a certain coefft. to determine the target amt. of the dissolved oxygen and controlling the air contity or aeration.
CONSTITUTION: A detector 3 for the amt. of the dissolved oxygen to measure the amt. of the dissolved oxygen in the raw water in the biological oxidation tank 1 is provided. The amt. of the satd. dissolved oxygen in the tank 1 is determined from the temp. detected by a temp. detector 2 in an arithmetic means 13. The amt. of the satd. dissolved oxygen determined in such a manner is multiplied by the coefft. changed according to the raw water temp. to calculate the target amt. of the dissolved oxygen. The calculated amt. of the dissolved oxygen is corrected by the amt. of the dissolved oxygen in the tank 1 detected by a detector 3 for the amt. of the dissolved oxygen, by which the target air quantity for aeration is determined. A control valve 9 for the air quantity for aeration is controlled by such target air quantity for aeration. As a result, the aerobic conditions for the biological membranes to make satisfactory activation are maintained and the costs of the maintenance and control are reduced.
ISHIKAWA HIDEYUKI
SUZUKI NORIHISA
OKUMA KEIJI
HITACHI ENG CO LTD
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