SUBSTRATE UTILIZATION AND MASS-TRANSFER IN AN AUTOTROPHIC BIOFILM SYSTEM - EXPERIMENTAL RESULTS AND NUMERICAL-SIMULATION

An autotrophic biofilm has been investigated for over 10 months in a b iofilm tube reactor. The objective of this investigation was the verif ication and improvement of a biofilm model. The use of a Clark-type ox ygen microelectrode in situ allowed the determination of the substrate flux in the biofilm. Also, the population dynamics of the autotrophic bacteria could be evaluated by varying the substrate conditions. Simu lation of the experimental results showed that the liquid phase of the biofilm decreased with biofilm depth. This could be described by a lo gistic function. The density of the inert volume fraction was found to be higher than that of the viable bacteria. This was verified in a no nsubstrate phase of 5 weeks. Growth and decay of the autotrophic bacte ria could be described by the growth, endogenous respiration, and deat h processes. Mass transfer coefficients at the bulk/biofilm interface were evaluated. They were found to be one order of magnitude higher th an those known from hydrodynamics in tu bes without a biofilm. (C) 199 7 John Wiley & Sons, Inc.