The sticky behavior of activated sludge during the dewatering and drying process is a worldwide issue. This is also the case in the Centridry® installation at the Monsanto Antwerp Wastewater Treatment Plant in Belgium. The applied technology combines a decanter centrifuge combined with a flash dryer in one enclosed compact system to reduce the sludge volume.
Previously, system capacity was very limited due to partially-dried sludge sticking on the screw conveyor of the decanter 
centrifuge and even onto the dryer wall. This was forcing the sludge feed to be stopped, with the system requiring extensive cleaning every 8 hours. In cases where the sludge dewatered in the centrifuge to such an extent that it had already reached the dryness range wherein it became sticky, the torque on the shaft of the screw conveyor peaked to such significant levels that the sludge feed needed to be reduced to prevent mechanical damage.
Solution: Creating an aquaplaning effect with Kemira PAX-14
Based on practical experience and further evidenced by a statistical analysis of the performance of the drying system, it was shown that occasional mixing of the plant´s flotation sludge containing PAX-14 with the standard excess sludge from the clarifier underflow resulted in a lower fouling frequency on the dryer wall. PAX-14 obviously has a positive impact on the sludge properties, especially in that particular dryness area in which the stickiness occurs.
As a result of the addition of PAX-14 in the waste sludge feed, the torque of the centrifuge’s screw conveyor is kept under control and the solid build-up on the dryer wall is nearly eliminated, yielding a significant annual centrifuge-dryer capacity increase of nearly 50%.
Customer benefits
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Reduced maintenance cycles
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Higher capacity due to the stickiness-mitigating effect of PAX-14
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Improved process and OPEX efficiency
