RUI: Modeling of Sludge Dewatering Processes

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The objective of this project is to improve the process by which equipment and processes are designed for removing water from sludges. This will involve the development of computer based simulation models of full-scale dewatering facilities that will enable cost- effective design and the ability to identify operational conditions to maximize dewatering efficiency. Theoretical approaches will include modeling the physics of the belt filter press which involves gravity sedimentation, cake filtration in a laterally unconfined domain incorporating the effect of secondary consolidation or creep, cake removal mechanisms, and belt washing efficiency. The integrated model of the belt filter press is expected to be driven by laboratory derived relationships of sludge porosity as functions of effective stress and permeability. These relationships will be determined by examining specific resistance and compression- permeability cell data. The model will be tested with data from a scale model filter press using a reproducible suspension of kaolin. Further model testing will be accomplished using the city of Portland's full-scale belt filter presses to analyze the model's ability to predict dewatering characteristics of an anaerobically digested sludge. Results of this project are expected to be used in improvements of current practice in designing systems for dewatering sludges, processing and management of which are approximately half the cost of wastewater treatment.