Simulation of growth and detachment in biofilm systems under defined hydrodynamic conditions.
Detachment from biofilms was evaluated using a mixed culture biofilm grown on primary wastewater in a tube reactor. The growth of biofilms and the detachment of biomass from biofilms are strongly influenced by hydrodynamic conditions. In a long-term study, three biofilms were cultivated in a biofilm tube reactor. The conducted experiments of biofilm growth and detachment can be divided into three phases: 1) an exponential phase with a rapid increase of the biofilm thickness, 2) a quasi-steady-state with spontaneous fluctuation of the biofilm thickness between 500 and 1,200 microm in the investigated biofilm systems, and 3) a washout experiment with increased shear stress in three to four steps after several weeks of quasi-steady-state. Whereas the biofilm thickness during the homogeneous growth phase can be regarded constant throughout the reactor, it was found to be very heterogeneous during the quasi-steady-state and the washout experiments. Growth and detachment during all three phases was simulated with the same one-dimensional biofilm model. For each of the three phases, a different detachment rate model was used. During the homogeneous growth phase, detachment was modeled proportional to the biofilm growth rate. During the quasi-steady-state phase, detachment was described by random detachment events assuming a base biofilm thickness. Finally, the washout experiment was simulated with detachment being a function of the biofilm thickness before the increase of the shear stress.
Horn
Harald
H
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA. harald.horn@chemie.hs-magdeburg.de
Reiff
Helmut
H
Morgenroth
Eberhard
E
D001420:Bacteria, Aerobic / Q000502:physiology; D001422:Bacterial Adhesion / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors / Q000382:microbiology; D002455:Cell Division; D003198:Computer Simulation; D005434:Flow Cytometry / Q000379:methods*; D007220:Industrial Waste; D008954:Models, Biological; D009038:Motion; D012212:Rheology / Q000295:instrumentation / Q000379:methods; D033081:Shear Strength; D013314:Stress, Mechanical; D014871:Water Microbiology
D007220:Industrial Waste