AERATION CONTROL USING CONTINUOUS DISSOLVED OXYGEN MONITORING IN AN ACTIVATED SLUDGE WASTEWATER TREATMENT PROCESS

The original design for the 2000 UC Davis Wastewater Treatment Plant (WWTP) relied on manual aeration control to maintain desirable dissolved oxygen (DO) levels in the oxidation ditch. Given the large daily variation in flow and wastewater strength, WWTP operators found it difficult to maintain stable DO levels. As a result, operators typically erred by providing too much oxygen, and the ditch was often found to be in an over-aerated state. Thus, the original control strategy wasted energy and promoted unstable biological conditions.In January 2004, UC Davis installed a new system for continuously measuring DO in the oxidation ditch and automatically controlling aeration. The project scope included installing a “floating ball-type” DO monitor, adding variable speed drives (VFDs) on two aerator motors, and programming a PLC to automatically vary aeration in response to measured DO levels in the oxidation ditch.This paper discusses the challenges of manual aeration control, the process UC Davis used to automate aeration and results for the first year of operation.