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By Bob Dabkowski

The key to optimizing the aeration process is accurate and reliable dissolved oxygen (DO) monitoring and control. To achieve this, the Duck Creek Wastewater Treatment Plant has adopted advanced luminescent technology for online DO monitoring.

Although activated sludge systems are less expensive to build than trickling filter plants, they are typically more expensive to operate because of the need for greater energy to run blowers for aeration. The key to optimizing the aeration process is accurate and reliable DO control.

Insufficient levels of DO prevent the successful degradation of organic matter and create conditions for the proliferation of filamentous bacteria. Too high DO levels, on the other hand, wastes energy. Power costs related to the operation of activated sludge plants generally run from 30 percent to 60 percent of the total electrical power consumed, and the electricity bill is typically the first or second most costly operational expense at most facilities. Accurate DO control in the aeration process, however, can save plants substantial amounts of power – and money – by applying only enough air for the biological process to function efficiently.

Prior to the plant expansion, Duck Creek operators had used a handheld membrane-based probe to monitor DO levels in the plant's trickling filter solids contact system. Keeping the probe operating properly for this intensive daily operation was always a headache for plant staff, requiring frequent membrane replacements and continuous cleaning and recalibration.