Analysis of biofilm growth rate in a packed bed bioreactor

Abstract

This paper focuses on the determination of the specific growth rate (nb) of bound E. coli UB 1832 cells, a necessary parameter in describing biofilm formation. Independent experiments have been performed in a fixed bed biofilm reactor to assess the rates of suspended cell deposition, attached cell growth and endogenous decay, and biofilm detachment. The decay rate was measured separately from the reactor and found to be negligible. The deposition rate was also very small when glass beads and E. coli UB 281 comprised the surface. Therefore, biofilm detachment rate (kdet) equalled the attached cell growth rate (1). This means that ub can be estimated directly from D (Xsus/Xb) (V/A) (2). Use of relationship (2) provides a μb of 0.005.h−1 slow compared to typical E. coli growth rates, whereas kdet determinations give a mean value of 0.33.h−1. The difference may be due to an overestimation of attached cells per unit of support area (Xb), due to fouling processes involving the substratum material of the reactor. The determination of kdet is a convenient way to assess ub when fouling could complicate such determinations.