A consistent modelling methodology for secondary settling tanks: a reliable numerical method
- 1 July 2013
- journal article
- research article
- Published by IWA Publishing in Water Science & Technology
- Vol. 68 (1), 192-208
- https://doi.org/10.2166/wst.2013.239
Abstract
The consistent modelling methodology for secondary settling tanks (SSTs) leads to a partial differential equation (PDE) of nonlinear convection-diffusion type as a one-dimensional model for the solids concentration as a function of depth and time. This PDE includes a flux that depends discontinuously on spatial position modelling hindered settling and bulk flows, a singular source term describing the feed mechanism, a degenerating term accounting for sediment compressibility, and a dispersion term for turbulence. In addition, the solution itself is discontinuous. A consistent, reliable and robust numerical method that properly handles these difficulties is presented. Many constitutive relations for hindered settling, compression and dispersion can be used within the model, allowing the user to switch on and off effects of interest depending on the modelling goal as well as investigate the suitability of certain constitutive expressions. Simulations show the effect of the dispersion term on effluent suspended solids and total sludge mass in the SST. The focus is on correct implementation whereas calibration and validation are not pursued.Keywords
This publication has 23 references indexed in Scilit:
- On reliable and unreliable numerical methods for the simulation of secondary settling tanks in wastewater treatmentComputers & Chemical Engineering, 2012
- On-line robust nonlinear state estimators for nonlinear bioprocess systemsCommunications in Nonlinear Science and Numerical Simulation, 2012
- Settler dynamic modeling and MATLAB simulation of the activated sludge processChemical Engineering Journal, 2009
- One-dimensional modelling of the secondary clarifier-factors affecting simulation in the clarification zone and the assessment of the thickening flow dependenceWater Research, 2007
- Advances in distributed parameter approach to the dynamics and control of activated sludge processes for wastewater treatmentWater Research, 2006
- Dynamics of an activated sludge process with nitrification and denitrification: Start-up simulation and optimization using evolutionary algorithmComputers & Chemical Engineering, 2006
- New automatic control strategies for sludge recycling and wastage for the optimum operation of predenitrification processesJournal of Chemical Technology & Biotechnology, 2005
- Optimal operation of alternating activated sludge processesControl Engineering Practice, 2005
- Detailed spatio-temporal solids concentration profiling during batch settling of activated sludge using a radiotracerWater Research, 2005
- Optimisation of clarifier-thickeners processing stable suspensions for turn-up/turn-downWater Research, 2004