Dissolved Oxygen Measurement In Continuous Aeration Sewage Treatment

When used to measure the dissolved oxygen in an aeration tank, sensors tend to quickly become contaminated and need frequent cleaning. A cost-effective solution to this problem has finally been found with the development of the Yokogawa DO402 Dissolved Oxygen Converter system. With this system, the sensor is mounted in a float ball holder that protects it from contamination and enables continuous maintenance-free use for extended periods.

Sewage that flows into a treatment plant is sent to a primary sedimentation tank to remove the garbage and sludge. Thereafter, it is routed to an aeration tank where activated sludge (sludge containing bacteria, protozoa, and other microorganisms) is added and air is blown into the mixture to agitate it. The microorganisms in the activated sludge thrive on the oxygen and cause the organic substances in the sludge to proliferate and the generated solids to be precipitated.

A shortage of dissolved oxygen (DO) will kill the microorganisms, so the DO concentration in the aeration tank must be properly controlled. A DO analyzer is used to continuously measure the DO concentration.