Biomedical Engineering Reference
In-Depth Information
Chapter 10
T
HE
R
OLE OF
B
IOFILM AND
F
LOC
S
TRUCTURE
IN
B
IOLOGICAL
W
ASTEWATER
T
REATMENT
M
ODELLING
Mario Plattes
*
Centre de Ressources des Technologies pour l'Environnement, Centre de Recherche
Public Henri Tudor, 66, rue de Luxembourg (BP 144), L-4002 Esch-sur-Alzette,
Luxembourg
Abstract
Biological wastewater treatment modelling has become and important tool in process
engineering. There are state of the art activated sludge models (ASMs) available, which have
found wide application in the engineering community. Biofilm models have found less
application in engineering practice so far, and a gap has developed between biofilm research
and engineering practice in the biofilm modelling community. In this context biofilm and floc
structure have played different roles in biological wastewater treatment modelling. Activated
sludge models (ASMs) do not explicitly take floc structure into account. In contrast biofilm
structure has been strongly emphasized in biofilm models over the past decades. Biofilm
models have as a result evolved with increasing complexity from one- to two- to three-
dimensional models. One reason for this is that biofilm structure is crucially linked to
diffusion by Fick's laws of diffusion, since it is known that diffusion is an important process
in biofilm systems. The application of Fick's laws of diffusion has thus been a driving force
towards the development of multidimensional biofilm models with increased model
complexity, because biofilms have a complex, heterogenous three-dimensional structure. The
increasing complexity has not led, however, to increased application of biofilm models in
engineering practice, and there is a trend towards simplified (e.g. zero-dimensional) models
for this purpose. Further it has been shown that diffusion and structure play an important role
in activated sludge systems. The role of activated sludge structure has recently led to the
development of multidimensional activated sludge models in activated sludge research, whilst
the state of the art ASMs for engineering practice do not take floc structure into account.
*
Tel. : +352 - 545580 - 612 ; fax. : +352 - 545580 - 601
