Patent ID: 7718066

Claim:
A method of exercising continuing control over an oxygen-consuming biological wastewater treatment process in which the need for oxygen repeatedly increases and decreases and which is conducted in a plurality of wastewater treatment plant processing tanks in cooperation with a gas supply system to supply oxygen-containing gas bubbles to, and dissolve oxygen in, the wastewater in at least one of said plant processing tanks and a control system comprising at least one flow control element to supply an increasing and decreasing flow of oxygen-containing gas through the gas supply system into the wastewater in the at least one plant processing tank, at least one gas collection member and gas detector to provide off-gas data correlative with changing amounts of one or more gases in offgas from the wastewater, a controller to process the offgas data and cause the flow control element to increase and decrease the flow of oxygen-containing gas into the wastewater in said tank or tanks, and wherein the control system is programmed to tend to maintain a positive DO level in at least a portion of the at least one tank which method comprises: providing in the control system DO (dissolved oxygen) data correlative with varying DO levels in the wastewater and/or performance data correlative with varying ability of the gas supply system to dissolve oxygen in the wastewater, generating control values in the control system derived at least in part from (a) the offgas data and (b) the DO data and/or performance data and using such control values to generate control signals to cause the at least one flow control element to cause varying flows of oxygen-containing gas through the gas supply system and into the at least one processing tank that are correlative with the varying consumption of oxygen by the biological process adjusted to cause wastewater DO levels to move toward, return to or be maintained at a target value and/or compensate for the varying ability of the gas supply system to dissolve oxygen in the wastewater.