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Steady-state analysis of activated sludge processes with a settler model including sludge compression

Diehl, Stefan LU ; Zambrano, Jesús and Carlsson, Bengt (2016) In Water Research 88(1). p.104-116
Abstract
A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key... (More)
A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bioreactor, Bürger-Diehl settler model, Growth kinetics, Limiting flux, Secondary settling tank, Solids residence time (SRT).
in
Water Research
volume
88
issue
1
pages
104 - 116
publisher
Elsevier
external identifiers
  • pmid:26476681
  • wos:000367276500010
  • scopus:84944462976
ISSN
1879-2448
DOI
10.1016/j.watres.2015.09.052
language
English
LU publication?
yes
id
267e0e1a-b30d-439f-93bb-4f3438a1335a (old id 8045344)
date added to LUP
2015-11-11 14:45:03
date last changed
2017-06-04 03:21:11
@article{267e0e1a-b30d-439f-93bb-4f3438a1335a,
  abstract     = {A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration.},
  author       = {Diehl, Stefan and Zambrano, Jesús and Carlsson, Bengt},
  issn         = {1879-2448},
  keyword      = {Bioreactor,Bürger-Diehl settler model,Growth kinetics,Limiting flux,Secondary settling tank,Solids residence time (SRT).},
  language     = {eng},
  number       = {1},
  pages        = {104--116},
  publisher    = {Elsevier},
  series       = {Water Research},
  title        = {Steady-state analysis of activated sludge processes with a settler model including sludge compression},
  url          = {http://dx.doi.org/10.1016/j.watres.2015.09.052},
  volume       = {88},
  year         = {2016},
}