Continuous, real-time cake dryness measurement for smarter sludge dewatering

The sensor transforms the dewatering press from a standalone machine into an intelligent system. Real-time feedback allows for integration with PID controllers to automatically adjust screw speed based on actual cake dryness. This ensures the machine always operates at its peak efficiency, regardless of sludge variations.

Additionally, it acts as a critical safety catch. It detects sudden drops in dryness caused by empty polymer tanks or incorrect settings, allowing operators to intervene before performance is compromised.

For installations at plants with fluctuating sludge concentrations, we are able to operate a perfectly tuned dewatering system over the long term—in conjunction with measurements of influent sludge concentration—with minimal operating costs and consistent results.

Key Benefits

• Process Optimization: Enables fully automated machine control based on real-time data and is completely maintenance-free.
• Cost-Effective Precision: The OAE-SCOUT offers high accuracy at a significantly lower CAPEX, and does not require clumsy sampling machines.
• Operational Safety: Detection of process failures (e.g., empty polymer tank or wrong settings).
• Representative Measurement: Measures a volume of cake deep inside the cylinder, not just where the sensor touches the cake.
• Regulatory Compliance: Replaces manual sampling for internal documentation with automatic 24/7 digital logging.
• Maintenance Free: Non-contact internal measuring principle with no moving parts, no cleaning.

Technical details

The sensor is an OEM solution developed to fit seamlessly into the architecture of VOLUTE™ and other screw presses.

• Measurement Principle: Ultrasonic Transmission (Direct Cake Measurement).
• Integration: 4–20 mA or MODBUS for SCADA/PLC connection.
• Compatibility: Compatible with RVP Series (via standard compression box fittings) and FS/GS Series 300 / 350 / 400 (fits directly into inspection ports).
• Calibration: One-time 3-point on-site calibration; no regular re-calibration needed.

Measurement results from real-world operation—specifically at a municipal WWTP and during the dewatering of excess activated sludge—demonstrated a correlation with laboratory results of 93% (R = 0.93) when measuring within a dry matter range of 14–19% DM. The mean absolute error did not exceed 0.4% DS, which corresponds to the accuracy of standard laboratory methods. The average deviation close to zero (-0.01% DS) confirms that the sensor is not subject to systematic errors and provides reliable data without the need for frequent recalibration.

High correlation is particularly crucial during changes in operating parameters—both operators and the control system thus receive immediate feedback on the actual state of the “output product.” This enables rapid optimization of machine settings, reduces sludge disposal costs, and minimizes the risk of insufficient dewatering. The OAE-SCOUT sensor is thus a reliable partner for all operations where measurement accuracy is the foundation of economically and environmentally sustainable sludge management.

OAE-SCOUT Sensor Calibration Tool