Olpas Tentacle activated sludge (MLSS) concentration measurement

Olpas Tentacle MLSS concentration sensor

The Olpas Tentacle concentration sensor can be used for measurement of activated sludge concentrations in municipal wastewater treatment plants. For this measurement, the Olpas Tentacle sensor is connected to the Crodeon Reporter datalogger for sensor power and online, wireless data transmission.

Olpas Tentacle activated sludge/MLSS concentration sensor with Crodeon Reporter connector

The sensor is installed in the Aquafin Diest wastewater treatment plant aeration basin. The Olpas Tentacle can be mounted to a fixed support of suspended by a chain. For this measurement, it is chosen to suspend the sensor by a stainless steel chain.

Crodeon Reporter datalogger with Tentacle connected. Tentacle is suspended on a stainless steel chain

Real-time measurement

The following video shows the exact conditions where the sensor is used. During normal operation, the sensor is lowered 30 to 100cm under the water surface. There was no disturbance of the aeration air bubbles observed in the measurement results.

Olpas Tentacle MLSS concentration sensor just above the water surface - normally the sensor is installed 30-100cm lower for a good average value.

Factory calibration and no maintenance

The Olpas Tentacle is factory calibrated for TSS measurements with a reference of 1000 mg/L Al2O3 particles. This calibration reference allows the usage of the Tentacle sensor for MLSS measurements without recalibration.

Measured data. An increase in MLSS concentration is seen during rain events in the environment of the WWTP.

The concentration is higher during aeration cycles as we can expect increased mixing of the sludge flocs due to air bubble recirculation. Besides that, the concentration is seen to increase because of heavy loading of the WWTP by sudden rain events (such as on 29/08).

Olpas Tentacle after approx. 6 weeks of measuring without maintenance or cleaning. The orange ultrasound measurement window is clear visible in the center of the probe. No measurement issues were reported even-though some biofouling formation can be observed.

Comparison to WWTP standard - optical MLSS measurements

The factory calibrated Olpas Tentacle is compared to the default measurement installed in the WWTP: an optical MLSS concentration sensor. The optical sensor requires weekly cleaning and biweekly offset correction. The Olpas Tentacle sludge concentration sensor can operate without cleaning and corrections for prolonged periods. Here, a 6 week window without maintenance was demonstrated.