Mathematical Sciences

Lund University

Title Fundamental nonlinearities of the reactor-settler interaction in the activated sludge process
Authors Stefan Diehl, Sebastian Farås
Alternative Location, Restricted Access
Publication Water science and technology
Year 2012
Volume 66
Issue 1
Pages 28 - 35
Document type Article
Status Published
Quality controlled Yes
Language eng
Publisher IWA Publishing
Abstract English The activated sludge process can be modelled by ordinary and partial differential equations for the biological reactors and secondary settlers, respectively. Because of the complexity of such a system, simulation models are most often used to investigate them. However, simulation models cannot give general rules on how to control a complex nonlinear process. For a reduced-order model with only two components, soluble substrate and particulate biomass, general results on steady-state solutions have recently been obtained, such as existence, uniqueness and stability of solutions. The aim of the present paper is to utilize those results to formulate some implications of practical importance. In particular, strategies are described for the manual control of the effluent substrate concentration subject to the constraint that the settler is maintained in normal operation (with a sludge blanket in the thickening zone) in steady state. Such strategies contain how the two control parameters, the recycle and waste volumetric flow ratios, should be chosen for any (steady-state) values of the input variables.
Keywords Clarifier, Continuous sedimentation, Modelling, Partial differential equation, Thickener,
ISBN/ISSN/Other ISSN: 1996-9732