Case Study: Wastewater Level Monitoring
Foam and ice challenges in SBR tanks overcome with ABM’s non-contact radar level sensors
Level sensors are critical in controlling sequencing batch reactor (SBR) systems, monitoring liquid levels in the basins and helping to control pumps that move wastewater through the system.
A municipal wastewater treatment plant (WWTP) was experiencing issues with its existing level sensors. Due to a challenging environment, surface conditions and obstructions, the level sensors produced inaccurate and unreliable results.
To meet the demands of the difficult application, ABM’s explosion-proof, non-contact radar level sensors were selected, exceeding the plant’s expectations.
Problem
When existing radar level sensors continuously produced unstable results, the WWTP knew it was time to find a replacement solution.
The environment posed many challenges for the existing sensors. As the SBR cycles through treatment stages, the liquid surface conditions change from stable to turbulent, with foam and ice common on the surface.
In this case, the exiting sensors could not measure through the foam and ice, creating inaccurate level measurements. Both foam and ice can absorb, reflect, and attenuate microwave signals and affect a radar sensor’s performance.
In addition to surface conditions, obstructions and condensation amplified inaccuracy issues. Pipes inside the tank created false echoes that were not adequately managed by the sensor. Condensation build-up on the sensor’s antennas compounded the issue, creating a weak signal and maintenance issues.
The plant sought a proven solution to monitor their SBR system and ensure continuous operation.
Wastewater Level Monitoring Solution
ABM’s explosion-proof, non-contact radar level sensors with horn antennas were selected for the project due to their proven ability to perform under challenging conditions.
Working with the plant, a sensor model was selected to match the application criteria and mitigate future operational issues.
Foam and Ice
Selecting the right radar level sensor was essential for the application. ABM engineers recommended a low-frequency sensor model with self-adjusting technology to manage ice and foam concerns in the SBR basins.
False Echoes
ABM’s self-adjusting technology automatically manages false echoes. The radar sensors have continuous feedback with their environment, automatically adjusting the transmitted power and receiver sensitivity to get the same amplitude of wanted echo regardless of the distance to the liquid surface or tank conditions.
This technique allows the receiver to detect only one echo from the liquid surface while all false echoes from the pipes, tank walls and other obstructions are pushed under the noise level and eliminated, resulting in reliable and stable measurements.
Condensation
As for condensation, ABM’s radar level sensors are designed with self-cleaning operation. The rod antenna is made of non-stick Teflon material that prevents condensation or build-up from forming. In addition, the antenna shape is tapered to discourage accumulation, making it easier to shed condensation.
Conclusion
Implementing ABM’s explosion-proof non-contact radar level sensors proved instrumental in resolving the challenges the municipal wastewater treatment plant faced. The plant can now monitor tank levels and control pumps in the SBR system more confidently.
The successful deployment of ABM’s solution exceeded expectations and showcased the importance of selecting specialized technologies tailored to the unique demands of challenging environments in wastewater treatment systems.
