The SCA Östrand mill in Sweden converted their wastewater treatment system in 2004 from an anaerobic to a multibio system. Where previously, the dewatered waste activated sludge was sent to a landfill, the new system has the sludge dewatered in a new line, mixed with thick black liquor and then fed to the recovery furnace. The new dewatering line includes a dewatering unit and a centrifuge, bringing the dry content over 10%.
Two inline suspended solids (SS) sensors from the Cerlic ITXIL range were installed in strategic positions for controlling the dewatering line. Both sensors are utilised for closed-loop control of the polymer dosage before the dewatering unit and the centrifuge.
The TSS value from the Cerlic sensor is multiplied with the volume flow to get the dry content flow, which is then used to calculate the optimal polymer dosage. The data provided by the Cerlic sensors is also used for manual control of the amount of waste activated sludge.
The Cerlic sensors have contributed to a successful start-up of the dewatering line at the wastewater treatment plant. The sensors are used to maintain optimal conditions for the process with optimal dosage of polymers and the initial objective of a final dry content of 10% has been exceeded.
Key advantages of Cerlic sensors:
- Higher efficiency in the process equipment due to stable and optimal operating conditions
- Reduced consumption of polymers as excess dosage is avoided
- Quick notification of operational disturbances