Reliable solids measurements for centrifuge control

Vaasa Water’s Pått wastewater treatment plant, located in Finland, cleans the wastewater of the entire city of Vaasa and part of the wastewater of the neighboring municipalities of Korsholm and Malax. The wastewater treatment plant was drying its sludge with a centrifuge, mainly on weekdays only, which meant that the efficiency was not the best possible. The drying result was evaluated visually from camera footage which did not provide the exact dry content, and the centrifuge was at times adjusted manually through an automation system. The dry content was analyzed weekly at the plant’s laboratory. With the centrifuge approaching the end of its lifecycle, the decision was made to replace it with a new one. The starting point for the procurement of the new centrifuge was that it would operate fully automatically 24/7, without a crew. Operation without personnel and the optimal use of the centrifuge require several continuous measurements, which were supplied by Valmet. The whole project (a new centrifuge, measurements, and controls) paid for itself in about 1.5 years through the considerable savings in the reprocessing costs of the dried sludge.