WATER QUALITY-CONTROLLING METHOD FOR PURIFICATION OF SEWAGE AND APPARATUS THEREFOR

摘要

PURPOSE:To lower suspended solids in purified water to the minimum, by changing a set value of dissolved oxygen concentration in response to a volume index of sludge, and controlling an amount of air to be supplied into an aeration vessel while using the changed new dissolved oxygen concentration as an objective value. CONSTITUTION:SVI meter 21 is arranged in an aeration vessel 1 to feed measured data to an arithmetric unit 22. An objective value of dissolved oxygen concentration preset by a setting instrument 7 is applied to the arithmetic unit 22. Using the preset value from the setting instrument 7 as basic data, the arithmetric unit 22 discriminates whether the present state is under an over-SVI, proper-SVI or under-SVI pattern condition, from the measured data by SVI21, and calculates dissolved oxygen concentration necessary for returning it into the proper pattern when it is under the over or under pattern condition. Said result is inputted as a new objective value to a comparator 6.