Computational Fluid Dynamic Approach for Biological System Modeling

s: Various biological system models have been proposed in systems biology, which are based on the complex biological reactions kinetic of various components. These models are not practical because we lack of kinetic information. In this paper, it is found that the enzymatic reaction and multi-order reaction rate is often controlled by the transport of the reactants in biological systems. A Computational Fluid Dynamic (CFD) approach, which is based on transport of the components and kinetics of biological reactions, is introduced for biological system modeling. We apply this approach to a biological wastewater treatment system for the study of metabolism of organic carbon substrates and the population of microbial. The results show that CFD model coupled with reaction kinetics is more accurate and more feasible than kinetic models for biological system modeling. Introduction Systems biology integrates knowledge from diverse biological components and data into models of the system as a whole to investigate the behavior and relationships of all elements in a particular biological system. To establish a modeling approach is one of the key tasks for systems biology. Present models of biological system are most commonly based on the framework of deterministic chemical kinetics. This approach applied to study biological system has already provided valuable results, for example in studies of the networks controlling bacterial chemotaxis, developmental patterning in Drosophila and infection of E. coli by lambda phage. The major difficulty in applying deterministic chemical kinetics to modeling biological system is that we do not have enough information about the chemical kintics. Further more, the slow transport of reactants may influence the reaction rate remarkably, for the biological reaction, especially the enzymatic reaction, is very fast in comparison with the transport of reactants, so the transport behavior of the components in a biological system should be considered in the model. In this paper, a computational fluid dynamic approach is introduced for modeling of biological system. It is based on the transport of the components in biological systems with the inclusion of reaction kinetics. The population of the microbial and metabolism of organic carbon substrates and nitrogen in biological system for wastewater treatment are studied with the CFD approach. Firstly the approach is described with basic biological reactions, then, a benchmark biological wastewater treatment system is simulated. Computational fluid dynamics is a body of knowledge and techniques used to solve mathematical models of fluid dynamics on digital computers. This formulates and solves the fundamental mass, momentum, and energy conservation equations in space. For many processes it is, in principle, possible to incorporate a diverse range of phenomena within these basic equations and/or to complement them with additional conservations such as biological reactions. Examples of this approach applied in biological system have recently been provided for flow and mass transfer study by many researchers. We focus on the aerobic biological system for removal of organic carbon substances and nitrogen in wastewater, which is the main objective of the biological wastewater treatment system. This kind of biological system is a man-controlled ecological system, first developed at early 20th century and remained one of the most important wastewater treatment systems. The ecological system, in a constant stirred reactor with a cylinder dimension of radii and height of 4m, using high speed surface aerator in top of the center, is modeled with the method to study the population of the microbial and metabolism of the substrates and nitrogen. Method The mass transfer of the components in the system with biological reaction is controlled by convection and diffusion in the water, and the formula control the mass transfer of a component is as following: Ri S z C y C x C D z C u y C u x C u t C z y x ∑ + + ∂ ∂ + ∂ ∂ + ∂ ∂ = ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ ) ( ) ( 2 2