D-BAUG - Departement Bau, Umwelt und Geomatik - ETH Zürich

Resources ▪ Highlights
Fig. 1: Biofilm development can be characterized using different length scales: (a) Different types of microbial cells are distributed
heterogeneously in different colonies (microscale), (b) internal pores and channels within the biofilm matrix can allow for limited
advective flow inside the biofilm (micro- or mesoscale), (c) patchy distribution of biofilm clusters over the biofilm substratum (mesoscale),
(d) heterogeneous distribution of biofilm within the overall system of an annular reactor in research (macroscale) and (e)
in a rotating biological contactor as example for full-scale biofilm reactors (macroscale) (Photo: Siemens).
Fig. 2: Experimental systems and biofilm reactors are characterized
by length and time scales. Three time scales can be differentiated:
Initial attachment (minutes – hours), initial biofilm
development (days), growth, detachment, re-growth, maturation
(weeks, months, years). Research relevant to biofilm reactors
must integrate micro-, meso-, and macroscale and must evaluate
long-term biofilm development.
Fig. 3: The local entrainment velocity, u a , normalized by the Kolmogorov velocity, u η , is rendered over the turbulence interface visualized by
using an isosurface of enstrophy, where the isolevel, c ω² , normalized by the mean enstrophy in the turbulent region is cω² / = 10 -3 .
D-BAUG Annual Report 2009 ▪ 65