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The Full Guide To Dissolved Oxygen Monitors
Wednesday, March 17, 2021

Dissolved oxygen activated sludge plants rely on the balance of DO to conserve energy and budgets.

A target of 2mg/L of dissolved oxygen is optimal to ensure oxygen in the center mass of the floc. If there isn't enough oxygen, the floc will break up, requiring an expensive dose of new biomass.

If the DO levels are too high, you've wasted manpower and energy. Consumption in the floc increases, power consumption increases, and settling can be inhibited.

If you aren't monitoring the power consumption on your aerators, the cost could be prohibitive. It's estimated by the Water Environment Federation that treatment plants use 45% to 75% of all their electricity demand on aeration.

How can you prevent cost overruns and maintain proper DO levels?

Keep reading to find out!

A Look at Different Dissolved Oxygen Sensors

The implementation of DO monitoring and automated aeration protocols in wastewater treatment plants has been able to achieve a 25%-40% savings on their energy use.

Dissolved oxygen monitors, or DO monitors, are used to prevent over- or under-oxygenation of water through two main methods. Both methods have their pros and cons, as well as unique engineering challenges to overcome.

The first is Optical Fluorescence Sensor and the other is an Electrochemical Galvanic Membraned Sensor.

Keep reading to see how each works.

Optical Fluorescence Sensor

The optical DO sensor uses fluorescence to determine the chemical compounds in the water, specifically oxygen. Every molecule or compound absorbs a specific wavelength of light.

The Q46D optical dissolved oxygen sensor is calibrated to detect the concentration of dissolved oxygen. Through a process of interaction called quenching, oxygen diffuses into the active sensor material.

These kinds of sensors can detect a range of 0-40 PPM or parts per million. The optical elements have a 2-5 year life, which can be replaced. The lifetime of the element is determined by the extent of how much it is "bleached" in the quenching process.

Electrochemical Galvanic Membraned Sensor

The second form of sensing is the electrochemical galvanic membrane monitor.

Membrane DO sensors are not new, and a very reliable sensing method with decades of research and studies behind their efficacy. Durable and properly designed, they typically need little if any maintenance for a year or more.

Oxygen diffuses through a Teflon membrane, isolating the sensor from the liquid being measured. A current runs between the platinum and lead electrodes proportional to the concentration of the oxygen in the liquid.

Temperature is also measured for an accurate, reliable result from between -5°C to 50°C.

Both sensors benefit from Q-Blast technology from ATI to automatically clean the sensors periodically. This removes manual sensor cleaning maintenance from the equation and freeing up manpower for other duties.

Your Guide to Dissolved Oxygen Monitors

Dissolved oxygen monitors don't have to be just an extra thing to monitor, clean, and repair. They can provide a vital service that saves your treatment plant work, money, and time. The end-user gets cleaner, healthier, tap water at a lower cost.

Everybody wins with DO monitoring and integrated automation!

Want to see how you can implement these systems in your treatment plant today? Contact Analytical Technolog, Inc. in the USA or the UK to speak to a representative now!

Our goal at ATI is to help provide our customers with the knowledge needed to ensure a safe and healthy environment. Toward this goal, we strive to develop and produce the highest quality instruments available. Our commitment to continuous improvement of analytical sensing systems is the key to our steadily expanding monitoring capability, and provides our users with the power of reliable information.

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