Save energy and cut aeration costs with the new optical DO sensor

Aeration systems typically use more than half the electricity consumed in a wastewater treatment facility. So, when operational decisions are based on incorrect dissolved oxygen readings, they can create significant unnecessary electrical energy costs, as well as impacting treatment effectiveness.

The new ADS420 smart optical Dissolved Oxygen (DO) sensor delivers the essential measurements that help you avoid those costs.

Smart, reliable, accurate
DO measurement made easy

Designed to work the way you want to work, the new ADS420 utilizes the latest generation of drift-free optical measurement technology – minimizing operational costs and removing the need for routine calibration.

Compact, robust, and digitally enabled it features ABB’s EZLink™ technology, allowing for more efficient measurement and simpler deployment.

EPA compliant technology
EPA compliant technology

Using reliable and proven optical dissolved oxygen method which meets EPA approval.

No need for routine calibration
No need for routine calibration

The digital SmartCap is preloaded with calibration coefficients - simply snap on and start measuring.

No need for routine calibration
Simplified measurement

Access essential sensor data, and support through the EZLink Connect app, for added convenience.

Save energy and cut aeration costs with the new ADS420 optical DO sensor

Learn more about aeration challenges and how ABB’s new ADS420 helps water companies to save energy while ensuring regulatory compliance.

  • Screen /
  • Biological treatment
  • Sludge processing
  • Secondary clarifiers
  • Disinfection
  • Primary clarifiers

Aeration process

Aeration provides oxygen for bacteria to treat and stabilize the wastewater.

The supplied oxygen is used by aerobic bacteria in the wastewater to break down organic matter containing carbon, forming carbon dioxide and water.

Without sufficient oxygen, the bacteria cannot biodegrade the incoming organic matter in a reasonable time.

The optimum range of dissolved oxygen (DO) in aeration basins is based on the characteristics of the sewage influent, size of the aeration basin, and the sewage flow rate.

Aeration process

Dissolved oxygen concentrations in the aeration basin have a direct impact on treatment efficiency and need to be carefully monitored and controlled.

Aeration challenge

Treatment plant loading varies continuously and uncontrollably, from diurnal variation due to population activity, and seasonal changes such as heavy rains and industrial slug loads.

The variation in these process disturbances is extremely large and can vary from hours to months! This presents a significant challenge for the optimization of equipment and process control.

Aeration challenge

Wastewater treatment plants are subject to constant variations in loading that have a direct effect on aeration demand.

Energy Usage

Typically, aeration requires more than half of the electricity consumed in a typical wastewater treatment facility.

To put this into perspective: In a typical mid-sized US city, 30% - 40% of energy use results from wastewater treatment operations.

Up to 25% of a city’s total energy use is related to aeration, and WWTPs are rarely operated at design – on average plants run at only one-third of capacity.

Energy Usage

Improving efficiency

ABB’s range of products and digital solutions for the wastewater industry provide better, more accurate monitoring, measurement and control of aeration processes, creating energy efficiency savings and a smaller carbon footprint, while ensuring regulatory compliance.

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Variable frequency drives (VFD) deliver innovative pump and blower features that can greatly decrease aeration operating costs by maintaining correct oxygen levels within aeration basins and reducing airflow from the blowers.

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Intelligent sensors and analyzers provide reliable, accurate measurement of the key parameters across the wastewater treatment plant to optimize process control and ensure regulatory compliance.

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Our extensive instrumentation portfolio includes a range of flow, pressure, level and temperature measurement devices for wastewater treatment. Including direct mass flowmeters to accurately measure blower airflow for precise control.

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The ABB Ability™ Digital Powertrain is a suite of digital solutions – including devices, software and services – combining connectivity and data analytics with our expertise to make your operations efficient, predictable and safe.

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Innovations in ABB’s Variable Frequency Drives (VFDs), combined with the latest developments in measurement and control technology, are helping operators to reduce energy usage and maintain stable operating processes under varying demands.

The two main approaches to aeration are Surface Aeration and Diffused or Blower Aeration, and the most reliable control strategies for any method rely on the use of a dissolved oxygen sensor. The location and reliability of the DO probe is essential to ensure correct and efficient aeration control.

Surface aeration

Surface aeration

Surface aerators push water from under the water’s surface up into the air, then the droplets fall back into the water, mixing in oxygen.

Blower aeration

Blower aeration

Aeration is supplied by blowers through a series of pipes into the base of the aeration pits.

Classical control strategies, based on a simple PID control loop, adjust the air flow based on the DO set-point via a flow control valve. This maintains the DO value within acceptable limits, but fails to address the low-energy-consumption requirements of modern plants.

A control strategy using ABB’s VFDs together with ABB’s dissolved oxygen sensor, SensyMaster thermal mass flow meter, and ControlMaster cascade controller, allows the drive to directly change the speed of the blower. This means the control valves can be removed, significantly reducing energy consumption.

Advances in blower aeration control

Traditional aeration control strategies for surface aerators use a simple controller to turn the DOL (direct on line) starter on or off depending upon the dissolved oxygen level. Often, this approach proves incapable of maintaining the DO value within acceptable limits and, in most cases, shows high levels of inrush current.

ABB’s VFDs can be used directly with the ADS420, allowing the drive to directly change the speed of the aerator. This removes the need for the controllers and offers significant energy savings.

Advances in surface aeration control

Dependable performance you can rely on

Able to withstand the harshest environments

The ADS420’s fast, stable, and accurate measurements are unaffected by pH, sample flow, sulfides, sulfates and other interferences, that can affect traditional membrane-based sensors.

The tough lumiphore coating is resistant to abrasion and fouling. This ensures reliable long-term deployment in the hostile operating conditions, found in many utility and industrial wastewater treatment processes.

Eliminate manual calibration errors

Each SmartCap is supplied pre-calibrated and contains the factory calibration coefficients, serial number, and other diagnostic and manufacturing information within the membrane cap.

When the SmartCap is connected, this information is automatically uploaded to the sensor with no user calibration required and no special codes to enter. Simply snap on the SmartCap and start measuring.

Eliminate manual calibration errors
EZLink makes measurement easy

The ADS420 is designed to be easy to set up and operate. Supplied fully factory-calibrated, it can be operational in minutes with ABB’s EZLink ‘plug and play’ technology.

Using advanced automatic sensor recognition and set-up, EZLink technology enables the ADS420 to quickly match with our digital transmitters, with no wiring, additional set-up, or fine-tuning required. Once operational, all analysis and signal conditioning are performed within the sensor, with the resulting data relayed digitally to the transmitter.

EZLink makes measurement easy
Stable, drift-free measurement

The ADS420 uses the US EPA-approved Rugged Dissolved Oxygen (RDO™)* method. The method uses a membrane embedded with lumiphore molecules. Oxygen molecules in the sample interact with the lumiphore molecules by altering the membranes luminescent state. The shift in light is measured between the membrane and a reference LED to provide an accurate calculation of dissolved oxygen concentration.

* RDO is a trademark of In-Situ.

Stable, drift-free measurement
Fully automated air cleaning

Biological fouling of oxygen membranes can severely affect sensor performance, leading to inaccurate readings and increased energy usage, unless they are regularly cleaned.

In applications where high biofouling is expected, the ADS420 can be used with ABB’s fully user configurable EZClean system. This robust automatic cleaning system periodically releases a powerful jet of air across the membrane surface, removing any biofilm build up.

Fully automated air cleaning

Improve efficiency through smart real-time data analysis and control

Work the way you want to work, by combing the ADS420 with our latest generation of smart digital transmitters and solutions.

  • Measure at multiple locations for enhanced aeration optimization or combine with other parameters for improved regulatory compliance
  • Easy access to data with seamless digital integration into DCS, or securely monitor and control remotely via your web browser
  • Directly connect to your smart device to access essential sensor information and support whenever and wherever you need it.
AWT20 Front Mobile

Mounting configurations

Versatile, compact design for easy mounting and installation

Floating ball

Ensures a constant submersion depth, with varying water levels.


Mount directly onto a pole using the ¾” NPT thread or ABB pole mounting kit.


Chain mount kit for cost-effective open channel installation.


Quick disconnect T-piece for inline pipe mounting.

Take control of your aeration process

ABB’s new ADS420 DO sensor helps you to:

  • Reduce energy consumption
  • Lower your operational costs
  • Improve operational efficiency

Work the way you want to work, with the ADS420.

Contact us to find out more