Wastewater Sludge Pumping Systems
Abstract
For many years, Bondi Sewage Treatment Plant has experienced operating problems in achieving reliable withdrawal of raw sludge from the primary sedimentation tanks without manual intervention. This is mainly due to the inability to consistently initiate flow during startup conditions and is primarily related to the very long suction lines and poor location of the pumps relative to the sludge hoppers. These pump suction problems have been the subject of numerous investigation and trials over several years.
To gain a better understanding of the flow properties of the sludge at Bondi Sewage Treatment Plant, Sydney Water Corporation in conjunction with Sinclair Knight Merz and Royal Melbourne Institute of Technology (RMIT University) undertook additional sludge rheology testing to enable pressure drop in the pipeline to be estimated. Vane and Couette rheometer tests were undertaken to measure yield stress and plastic viscosity of the sludge at varying concentrations to simulate both startup and steady state (laminar flow) conditions respectively. The Bingham plastic model was used to establish a predictive model for Bondi sludge. These test results show much larger values of yield stress for startup than for established flow.