Biofilm model calibration and microbial diversity study using Monte Carlo simulations

Abstract

Mathematical models are useful tools for studying and exploring biological conversion processes as well as microbial competition in biological treatment processes. A single-species biofilm model was used to describe biofilm reactor operation at three different hydraulic retention times (HRT). The single-species biofilm model was calibrated with sparse experimental data using the Monte Carlo filtering method. This calibrated single-species biofilm model was then extended to a multi-species model considering 10 different heterotrophic bacteria. The aim was to study microbial diversity in bulk phase biomass and biofilm, as well as the competition between suspended and attached biomass. At steady state and independently of the HRT, Monte Carlo simulations resulted only in one unique dominating bacterial species for suspended and attached biomass. The dominating bacterial species was determined by the highest specific substrate affinity (ratio of µ/KS ). At a short HRT of 20 min, the structure of the microbial community in the bulk liquid was determined by biomass detached from the biofilm. At a long HRT of 8 h, both biofilm detachment and microbial growth in the bulk liquid influenced the microbial community distribution.

Modelling microbial competition in nitrifying biofilm reactors

“…Conceptual and predictive mathematical models describing microbial diversity should be developed to obtain a deeper understanding of ecosystems and possible ways to manipulate them (Nielsen et al, ). Recently, mathematical models have been developed including microbial diversity, for example, a recent study used a multi‐species biofilm model to demonstrate the influence of biomass detachment and microbial growth in the bulk liquid on the microbial community in a heterotrophic biofilm (Brockmann et al, ). A few nitrifying biofilm models including two or more species of the same functional guild (AOB or NOB) have been presented.…”

Influence of process dynamics on the microbial diversity in a nitrifying biofilm reactor: Correlation analysis and simulation study

“…First, only the microbial parameters of AOB known to have an important effect on bulk liquid composition, that is, maximum growth rate and affinity for ammonium and oxygen, see Vannecke and Volcke () and previously performed sensitivity analyses (Brockmann and Morgenroth, , ; Brockmann et al, , ), were calibrated to the experimentally recorded bulk liquid concentrations of total ammonium (TNH), total nitrite (TNO 2 ), and nitrate (NO 3 − ). By checking the fit of the simulation results with the observed overall process performance, it was found that besides the calibration of these microbial parameters for the AOB, these parameters also had to be calibrated for the NOB guild.…”

“…Microbial diversity is typically neglected in conventional models, which at most make a distinction between functional guilds, that is, AOB and NOB in case of nitrification processes. Nevertheless, multispecies models including microbial diversity are useful tools to investigate in which way microbial population dynamics are influenced, for example, by various microbial properties (Vannecke and Volcke, ) or biofilm characteristics (Brockmann et al, ). They are also essential to study the relation between macroscopic reactor behavior and microbial population dynamics.…”

Modeling microbial growth and dynamics

“…Brockmann et al (2013) presented a multi-species kinetic model incorporating biofilm detachment that was used to study the effect of hydraulic retention times (HRT) and bulk fluid species composition on the selection of dominant species in a biofilm. Multi-substrate kinetic models have been developed by (Lu et al 2007) by switching between different growth rates depending on the locally limiting resource but one may assume that multiple, complementary resources influence the growth rate at the same time (Makinia 2010, p. 134).…”