Patent ID: 7449113

Claim:
A method of controlling a biological wastewater treatment process, comprising: A. in at least one treatment tank containing wastewater and having associated therewith at least one device to supply an increasing and decreasing flow of oxygen-containing gas and/or wastewater into the tank, conducting a biological process wherein the need for oxygen in the process repeatedly increases and decreases during the process, B. supporting the process at least in part by introducing the oxygen-containing gas into the wastewater in the form of bubbles provided in the wastewater by a gas supply system, and causing at least a portion of the oxygen in the bubbles to dissolve in the wastewater and at least a portion of the dissolved oxygen to be consumed by the biological process 1. wherein the oxygen so dissolved may represent an excess or a deficiency relative to the oxygen consumed by the biological process, and 2. wherein at least one gas collection member is positioned to receive offgas representing gas from said bubbles that has not been dissolved into the wastewater; C. controlling the operation of the biological process with a control system that, as the process operates, exercises continuing control over the process at least partially in response to 1. offgas measurements that are taken by the control system from the offgas collected in the gas collection member and that are correlative with changing amounts of one or more gases in the offgas, and 2. DO data correlative with varying DO levels in the wastewater and/or performance data correlative with varying ability of the gas supply system to transfer oxygen to the wastewater; D. utilizing said measurements and data to provide, in the control system, control values, which may be components of control values, and which include 1. first control values, comprising requirements control values, that change in response to, while remaining correlative with, the need for oxygen in the process, and 2. second control values, comprising DO control values and/or performance control values that change in response to, while remaining correlative with, respectively, DO levels in the wastewater and/or the varying ability of the gas supply system to transfer oxygen to the wastewater; and E. deriving, in the control system, utilizing said first and second control values, control signals for adjusting said at least one device.