Water, Wastewater & Stormwater

Oral

397882 - Improving digester capacity and solids concentration limit using novel CFD analysis techniques.

Tuesday, June 5
4:00 PM - 5:30 PM
Location: Greenway EF
Co-Authors: Kevin Nielsen, Corvallis, OR – CH2M; Jon Bates, Melbourne, Australia – CH2M; Sam Perera, Melbourne, Australia – CH2M

This presentation will describe the evaluation of a waste water digester using Computational Fluid Dynamics (CFD) and the comparison of simulation results to a physical tracer test. The objective of the CFD analysis was to evaluate the current mixing configurations of the digesters and to assess the impact of increasing the digester operating solids concentration. The existing sludge digestion process on site is being augmented through the implementation of recuperative thickening to increase the operating solids concentration, and hence solids retention time, in the digesters. Increasing the solids concentration will impact the performance of the digester mixing systems. Scenarios evaluated in this study included performance at the current typical solids concentration equal to 2.5%, through the practical upper limit operating concentration of 4.5%. Included in this analysis was a comparison with a physical tracer study performed 3 years ago (2014). This analysis examined the effects of variable sludge solids concentration on the performance of two digester mixing configurations. The analysis also includes the non-Newtonian behavior of the digester sludge which is dependent on local shear stress at and solids concentration levels. Rheological test data was available to characterize the fluid.
The CFD modeling was able to provide insight for design and operations decisions moving forward. The multiphase model results demonstrated digester circulation patterns which matched physical observations and validated the gas injection modeling approach. The CFD model compared well to physical tracer test results. Based on the analysis, maximum solids concentrations of 3.5 and 4.0 percent were determined for the two configurations of digesters evaluated.

Daniel Morse, MS, PhD, PE

Technologist
Jacobs

Daniel Morse is a hydraulic technologist at Jacobs, a global engineering and professional services firm. He was hired to CH2MHill in 2008. Since then, he has served in the Advanced Hydraulics group providing expertise in fluid modeling for the pump stations, dams, reservoirs, grit basins, and clarifiers. He is part of a team that solves fluid problems for all industries related to flow distribution, pump performance, reservoir operation, transient surge, and a variety of other needs. Daniel has been fortunate to support major infrastructure projects from Australia, Asia, Europe, and the Middle East including several deep tunnel collection systems. Additional opportunities have included building an in-house High Performance Computing cluster, developing custom code modules (UDFs) for ANSYS Fluent, and research for a proprietary biological screening design for pump intakes. Prior to joining CH2MHill (recently merged into Jacobs) he spent 5 years as a research assistant at Oregon State University.

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