Abstract
Purpose. Efficiency determination of the aeration tank at the stage of design or reconstruction of bioreactors in which biological wastewater treatment is carried out requires the use of special mathematical models and calculation methods. The main purpose of the article is to develop CFD models for evaluating the operation efficiency of aeration tanks. Methodology. A numerical model has been developed for the computer calculation of the biological wastewater treatment process in aerotanks, taking into account hydrodynamics. The model is based on two-level mass conservation equations for the substrate and activated sludge and the velocity potential equation. The process of biological transformation of the substrate is calculated based on the Monod model. For the numerical integration of the mass transfer equations of activated sludge and substrate, the alternating-triangular difference splitting scheme is used. In this case, the basic equations are divided into two equations of a more simplified form. For the numerical integration of the equations for the velocity potential, it is split into two one-dimensional equations. Further, each equation is solved according to explicit scheme. For the numerical integration of equations that describe the process of substrate transformation based on the Monod model, the Euler method is used. Findings. The software implementation of the constructed numerical model has been carried out. The results of a computational experiment on the study of the wastewater treatment process in an aeration tank with plates are presented. This leads to the conclusion that the quality control of wastewater treatment in aeration tanks is possible with the help of plates. Originality. A multivariate CFD model has been developed, which makes it possible to quickly assess the efficiency of the aeration tank. A feature of the model is the ability to evaluate the operation of the aeration tank, taking into account its geometric shape and location of additional plates in the construction. Practical value. The constructed numerical model can be used during calculations in the case of designing aeration tanks, or in determining the efficiency of wastewater treatment under new operating conditions.
Highlights
Biological treatment is one of the most effective methods of wastewater treatment [3, 4, 6]
The existing mathematical models [1–5, 7–17] do not take into account a number of important parameters affecting the efficiency of bioreactors, or require significant time when implemented on computers (CFD-models)
The following scenarios were considered: scenario no. 1: the aerotank works without additional elements inside the structure; scenario no. 2: aerotank has one plate inside the structure; scenario no. 3: aerotank has two plates inside the structure; scenario no. 4: aerotank works as a reservoir for the substrate destruction, but there is no entry and exit of the substrate and activated sludge
Summary
Biological treatment is one of the most effective methods of wastewater treatment [3, 4, 6] Efficiency determination of this treatment at the stage of design or reconstruction of bioreactors, in which this method of wastewater treatment is carried out, requires the use of special mathematical models and calculation methods. These theoretical calculation methods are the main toolkit, since a physical experiment in the field of biological treatment always requires a long time and expensive equipment. The development of mathematical models for assessing the efficiency of biological reactors, which allow taking into account these important factors and quickly determining the values of the parameters necessary for the designer, is an important scientific task
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