A simplified mixed-culture biofilm model

Abstract

AbstractÐA simple dynamic model is presented for fast simulation of the removal of multiple substrates by dierent bacterial species growing in a bio®lm reactor. The model is an extension to the well-known half-order reaction concept that combines a zero-order kinetic dependency on substrate concentration with diusion limitation. The basic idea behind this model implementation is to decouple the calculations of the two major processes in the bio®lm: substrate diusion and biochemical conversion. The separate assessment of substrate diusion allows to relate the penetration depth of substrates to a fraction of biomass that is active in conversion. The conversion is then calculated considering only the active fraction of the biomass. The model is compared to experimental data from the literature and is found to be able to closely replicate the overall dynamics in a bio®lm system. The major advantage of the proposed model is the simple structure which leads to a reduction of the computational eort as compared to state-of-the-art mixed-culture bio®lm models. # 1999 Elsevier Science Ltd. All rights reserved Key wordsÐbio®lm, diusion, modelling, mixed-culture, simulation

Determination of Spatial Distributions of Zinc and Active Biomass in Microbial Biofilms by Two-Photon Laser Scanning Microscopy

“…However, the significant amount of active biomass distributed all over the thick biofilms suggests that essential nutrients, electron donors, and electron acceptors are still available to biomass in the inner biofilm regions. Thus, our results do not support predictions based on the concept of homogeneous biofilm models with active biomass located predominantly near the interface of the biofilm and the bulk aqueous phase and inactive biomass in the inner regions (27,30,39).…”

“…Model simulations based on the assumption of a homogeneous biofilm result in the prediction that active biomass will be located predominantly in the outer regions of biofilms (9,27,30,39). The existence of a heterogeneous structure in which open channels allow the bulk fluid to penetrate to variable depths within biofilms makes conclusions based on the assumption of homogeneous structure of questionable value.…”

Tratamiento biológico de aguas residuales: Principios, modelación y diseño

“…Una sola fracción de la biomasa se puede asumir a priori como se mostró en la sección 17.2. O bien, la densidad de diferentes fracciones de biomasa en el interior de la biopelícula, se puede determinar a cada intervalo de tiempo, a partir del balance del crecimiento, decaimiento y desprendimiento Rauch et al, 1999). Mientras que los cambios en las fracciones de la biomasa sobre el tiempo sean considerados, se asume que todas las fracciones de la biomasa se encuentran homogéneamente distribuidas sobre el espesor de la biopelícula, simplificando ampliamente las (a) Observe que los intervalos en esta tabla tienen que ser utilizados con extrema precaución, ya que el espesor de la biopelícula dependerá de múltiples factores, incluyendo la carga de sustrato, el tipo de sustrato, las fuerzas de desprendimiento y la operación global del reactor.…”

A wastewater treatment using a biofilm airlift suspension reactor with biomass attached to supports: a numerical model

“…For the growth of heterotrophic bacteria in the biofilm, two substrates are required, i.e., an electron acceptor (dissolved oxygen DO) and an electron donor (soluble organic matter). Both substrates are essential for bacterial growth (Wang and Wang 2012) and, consequently, the whole process is inhibited when one of the two is not available (Rauch et al 1999). Furthermore, nitrification is adversely affected at high COD:N ratios due to the direct competition for molecular oxygen between autotrophs (nitrifying microorganisms) and heterotrophs (carbonaceous substrate based microorganisms).…”