BOOK
Mathematical Modeling of Biofilms
(2006)
Additional Information
Book Details
Abstract
Over 90% of bacterial biomass exists in the form of biofilms. The ability of bacteria to attach to surfaces and to form biofilms often is an important competitive advantage for them over bacteria growing in suspension. Some biofilms are "good" in natural and engineered systems; they are responsible for nutrient cycling in nature and are used to purify waters in engineering processes. Other biofilms are "bad" when they cause fouling and infections of humans and plants. Whether we want to promote good biofilms or eliminate bad biofilms, we need to understand how they work and what works to control them. Mathematical Modeling of Biofilms provides guidelines for the selection and use of mathematical models of biofilms. The whole range of existing models - from simple analytical expressions to complex numerical models - is covered. The application of the models for the solution of typical problems is demonstrated, and the performance of the models is tested in comparative studies. With the dramatic evolution of the computational capacity still going on, modeling tools for research and practice will become more and more significant in the next few years. This report provides the foundation to understand the models and to select the most appropriate one for a given use. Mathematical Modeling of Biofilms gives a state-of-the-art overview that is especially valuable for educating students, new biofilm researchers, and design engineers. Through a series of three benchmark problems, the report demonstrates how to use the different models and indicates when simple or highly complex models are most appropriate. This is the first report to give a quantitative comparison of existing biofilm models. The report supports model-based design of biofilm reactors. The report can be used as basis for teaching biofilm-system modeling. The report provides the foundation for researchers seeking to use biofilm modeling or to develop new biofilm models. Scientific and Technical Report No.18
Table of Contents
Section Title | Page | Action | Price |
---|---|---|---|
Contents | 6 | ||
Overview | 12 | ||
WHAT IS A BIOFILM | 12 | ||
WHAT IS A MODEL? | 12 | ||
MODEL SELECTION | 13 | ||
BIOFILM MODELS | 16 | ||
BENCHMARK PROBLEMS | 19 | ||
1.0 INTRODUCTION | 22 | ||
WHAT IS A BIOFILM? | 22 | ||
GOOD AND BAD BIOFILMS | 23 | ||
WHAT IS A MODEL? | 25 | ||
THE RESEARCH CONTEXT FOR BIOFILM MODELING | 26 | ||
A BRIEF OVERVIEW OF BIOFILM MODELS | 27 | ||
GOALS FOR BIOFILM MODELING | 28 | ||
THE IWA TASK GROUP ON BIOFILM MODELING | 29 | ||
OVERVIEW OF THIS REPORT | 29 | ||
Guidance for model selection | 29 | ||
Biofilm models considered by the Task Group | 30 | ||
Benchmark problems | 31 | ||
2.0 MODEL SELECTION | 32 | ||
BIOFILM FEATURES RELEVANT TO MODELING | 32 | ||
COMPARTMENTS | 33 | ||
The biofilm | 33 | ||
The bulk liquid | 36 | ||
The mass-transfer boundary layer | 37 | ||
The substratum | 38 | ||
The gas phase | 38 | ||
COMPONENTS | 38 | ||
Dissolved components | 38 | ||
Particulate components | 41 | ||
PROCESSES AND MASS BALANCES | 42 | ||
Transformation processes | 43 | ||
Transport processes | 46 | ||
Transfer processes | 47 | ||
MODEL PARAMETERS | 50 | ||
Significance of model-parameter definitions | 50 | ||
Significance of model parameter units | 51 | ||
Significance of environmental conditions | 52 | ||
Plausibility of parameter values | 53 | ||
Sensitivity of model parameters | 53 | ||
System-specific parameters | 54 | ||
GUIDANCE FOR MODEL SELECTION | 54 | ||
Overview of the models | 55 | ||
Modeling objectives and user capability | 56 | ||
Time scale | 58 | ||
Macro versus micro scales | 59 | ||
Substrate removal | 59 | ||
Biomass accumulation, production, and loss | 60 | ||
Spatial profiles of dissolved components | 62 | ||
Spatial distribution of particulate components | 62 | ||
Physical structure of the biofilm | 62 | ||
3.0 BIOFILM MODELS | 63 | ||
MASS BALANCES IN BIOFILM MODELS | 63 | ||
Microscopic (local or differential) mass balances | 64 | ||
General differential mass balances | 64 | ||
Particular forms of differential mass balances | 65 | ||
Macroscopic (global or integral) mass balances | 67 | ||
General integral mass balances | 67 | ||
Particular forms of the integral mass balance | 69 | ||
Relationships among the various models | 70 | ||
ANALYTICAL MODELS (A) | 73 | ||
Features | 73 | ||
Definitions and equations | 74 | ||
Mass balances for substrate in the bulk liquid | 74 | ||
Mass balances for substrate in the biofilm | 74 | ||
Mass balances for biomass | 76 | ||
Mathematical treatment | 76 | ||
One biological conversion process | 76 | ||
Two or more biological conversion processes & biofilm architecture | 77 | ||
Kinetics for multiple limiting substrates | 77 | ||
Solving the problem with a simple spreadsheet | 77 | ||
Applications | 78 | ||
Numerical versus analytical solutions | 78 | ||
Describing an existing reactor system | 78 | ||
Designing a biofilm reactor | 80 | ||
PSEUDO-ANALYTICAL MODELS (PA) | 80 | ||
Features of the basic pseudo-analytical model | 80 | ||
Adapting the pseudo-analytical model for multiple species | 82 | ||
The multi-species models | 82 | ||
Multi-species applications | 86 | ||
Standard condition | 86 | ||
High influent N:COD | 86 | ||
Low influent N:COD | 87 | ||
High detachment rate | 87 | ||
Oxygen Flux | 88 | ||
Interfacial Concentrations and Biofilm Deepness | 88 | ||
Summary for multi-species PA models | 89 | ||
NUMERICAL ONE-DIMENSIONAL DYNAMIC MODEL (N1) | 89 | ||
Features | 90 | ||
Definitions and equations | 92 | ||
Mathematical treatment with AQUASIM | 94 | ||
Applications | 95 | ||
Substrate removal | 95 | ||
Biofilm growth, microbial composition and detachment | 96 | ||
Pseudo 2d modeling of plug flow | 98 | ||
Pseudo 3d modeling | 98 | ||
NUMERICAL ONE-DIMENSIONAL STEADY STATE MODEL (N1s) | 100 | ||
Features | 100 | ||
Definitions and equations | 101 | ||
Software Implementation | 101 | ||
MULTI-DIMENSIONAL NUMERICAL MODELS (N2 and N3) | 102 | ||
General features | 102 | ||
Model classifications | 103 | ||
Definitions | 103 | ||
Representation of dissolved components | 103 | ||
Representation of particulate components | 104 | ||
Summary of multidimensional models used | 106 | ||
2d and 3d models with discrete biomass and solutes in continuum space (N2a, N2b, N3a, N3b, N3c) | 107 | ||
Features | 107 | ||
Definitions and equations | 108 | ||
Biofilm system definition | 108 | ||
Mass balances for dissolved components | 110 | ||
Momentum and mass balances for the liquid flow | 113 | ||
Mass balances for particulate components | 114 | ||
Solution methods | 116 | ||
The overall solution approach | 116 | ||
Solution methods for particular parts of the model | 117 | ||
Software implementation | 118 | ||
2d models with discrete biomass and discrete solutes (the Cellular Automata models N2c, N2d, N2e, N2f) | 119 | ||
Discretization of the physical domain | 119 | ||
Definition of substrate and microbial particles | 120 | ||
Discretization of Monod-type substrate-utilization kinetics | 120 | ||
Stochastic representation of microbial growth, inactivation, and endogenous respiration | 120 | ||
Simulation of microbial dynamics within the biofilm (N2f) | 121 | ||
Simulation of advective flux (N2d, N2e) | 121 | ||
Applications | 122 | ||
Formation of biofilm structure and activity in relation with the environment | 122 | ||
Biomass accumulation in biofilm | 122 | ||
Substrate uptake and mass transport in biofilm systems | 123 | ||
Biofilm structure | 125 | ||
Model comparison with experimental data | 127 | ||
Interactions in multispecies biofilms | 128 | ||
Multispecies nitrifying biofilm | 128 | ||
Multispecies methanogenic biofilm | 129 | ||
Competition between internal storage compound producer and EPS producing bacteria | 131 | ||
4.0 BENCHMARK PROBLEMS | 133 | ||
INTRODUCTION | 133 | ||
BENCHMARK 1: SINGLE-SPECIES, FLAT BIOFILM | 134 | ||
Definition of the system to be modeled | 134 | ||
Nomenclature | 183 | ||
References | 189 |