The difficult job of pumping thickened solids has plagued wastewater treatment plant designers and operators for decades. While numerous studies have proposed various methods for the design of thickened solids pumping systems, what method to use should be chosen carefully as there is not one universally accepted method to address all the various solids types and pumping scenarios.
When the solids content of a flow stream is below 2-3%, it is typically considered “dilute” and special design considerations are not typically required. Solids streams at a wastewater treatment plant, however, are commonly thickened to higher concentrations to optimize the operation and the capacity of downstream processes. In doing so, the conveyance of this thickened sludge becomes considerably more difficult. The thickened solids streams no longer behave like water when pumped, but still contain enough moisture to preclude the use of conveyance mechanisms used for dewatered solids streams. This can lead to both design and operational problems that must be thoughtfully addressed.
This presentation will provide an overview of:
· how and why thickened solids stream pumping varies from dilute streams
· the most common methods used to design pumping systems for thickened solids and when to use them
· point out a faulty methodology in two very commonly used reference books that can result in significantly undersized pumps
· compare the methods against each other and with real-world data
· equipment and operational factors to consider in facility design.