A practical project in South Korea demonstrates how this task can be reliably solved even under demanding conditions.
Challenge: Managing dynamic sludge processes
In a government-operated wastewater treatment plant, raw wastewater is collected in large primary settling tanks. Heavy solids settle at the bottom as primary sludge, while a clarified water layer forms above.
The level of this sludge layer is subject to continuous fluctuations. For plant operation, this means that the interface must be measured precisely and reliably in order to control sludge removal as needed and avoid process disruptions.
At the same time, the environmental conditions place high demands on the measurement technology. High humidity, changing material properties and the requirement for low-maintenance operation call for a solution that is both robust and precise.
Solution: Electromechanical interface measurement with NivoBob® NB 3300
The electromechanical lot system NivoBob® NB 3300 is used for this application. It has been specifically developed for continuous level and interface measurement in demanding environments. In this case, the device is configured with a cable version and interface weight, enabling precise detection of the sludge-water boundary.
The measuring principle is both simple and proven: a sensing weight is lowered into the medium in a controlled manner. When it reaches the sludge surface, the tension on the cable changes, allowing the exact position of the interface to be determined. The weight is then automatically retracted.
Thanks to this electromechanical principle, the system operates independently of material properties such as conductivity or dielectric constant – an important advantage when dealing with varying sludge compositions.
Reliable operation – even under changing conditions
In this application, the sensor is installed from above in a concrete tank with a depth of approximately 3.8 meters (12.5 ft). The process conditions are typical for wastewater treatment: high humidity, moderate temperatures up to 80 °C (176 °F), and a stable, non-hazardous environment.
The installed system is configured as a cable-operated solution for interface measurement, enabling precise detection of the sludge–water boundary. At the same time, the system can be adapted for measuring ranges of up to 30 m (98 ft), offering flexibility for larger installations. Integration into the control system is achieved via analog and digital interfaces such as 4–20 mA and Modbus, ensuring straightforward implementation into existing control architectures.
Installation is carried out via a flange connection (DN100 / 4″), providing a robust and secure mounting in the concrete tank.
Key advantages at a glance
- Precise and reliable interface measurement in sludge applications
- Independent of material properties such as conductivity or dielectric constant
- High measurement accuracy of ±0.5% of the full scale
- Long service life thanks to brushless motor technology
- Flexible adaptation to different sludge types
- Easy integration via analog and digital interfaces
Robust technology for industrial use
The NivoBob® NB 3300 is designed as an electromechanical lot system for industrial applications. A microprocessor-controlled measuring cycle ensures reliable and repeatable measurement results. The robust dual-chamber housing with IP66 protection rating guarantees dependable operation even in harsh environmental conditions.
With multiple output options – including 4-20 mA, Modbus and Profibus – the sensor can be easily integrated into existing control systems. Adjustable sensitivity also allows precise adaptation to different media.
Successful implementation in an international project
The project was successfully implemented in collaboration with UWT’s distribution partner microMtec.Co in South Korea. Close cooperation ensured that the solution was optimally tailored to the specific requirements of the plant.
The result is a stable and reliable measurement solution that significantly contributes to improved efficiency in the wastewater treatment process.
Conclusion
Interface measurement in settling tanks is a key element of modern wastewater treatment. With the electromechanical lot system NivoBob® NB 3300, a robust and field-proven solution is available that delivers reliable results even under changing process conditions.
This provides the basis for precise control of sludge removal – and ultimately for efficient and stable plant operation.
