POTENTIAL FOR THE USE OF ON-LINE RESPIROMETRY FOR THE CONTROL OF AERATION

A full-scale study was undertaken at the James C. Kirie Water Reclamation Plant (WRP) owned and operated by the Metropolitan Water Reclamation District of Greater Chicago (District). The objective of the study was to investigate whether the use of on-line respirometry would be feasible and more advantageous than the existing on-line dissolved oxygen (DO) probe system to determine and control the aeration requirement that is currently being used at the James C. Kirie WRP.Two empirical models were developed and improved with a view to automating and adjusting the air supply rate based on oxygen uptake rate (OUR) as measured by the on-line respirometer to the aeration tanks commensurate with the variation in the strength or oxygen demand of the incoming sewage. The results of this study showed that aeration control by on-line respirometry is technically feasible using a feed forward control strategy, and that it has the potential to save electrical energy, especially in a system where air supply far exceeds demand. However, more work needs to be done to actually demonstrate the applicability and reliability of on-line respirometric control of aeration using the models developed in this study.