Use of dispersed flow models in design of biofilm reactors

An attempt has been made to set up a relationship between the removal efficiency and the dispersion characteristics of biological filters. For granular-media trickling filters, effluent concentrations have been calculated with the equation of complete mixing at low flow rates and by means of a dispersed plug-flow model for large hydraulic loadings. For coarse media, the mixed flow zone disappears and the substrate removal is obtained using the equation of dispersed plug flow. The effect of temperature and substrate concentration on the filter efficiency has been investigated using the model developed and the application of this theory to the practical problems has been thus demonstrated.     

Kinetics Characteristics of Biofilm Reactors

A numerical model of biofilm reactors was tested using Monod typebiological kinetics in terms of the properties of feed solutionand dispersion. The model is based on computer techniques andthe numerical evaluation of the normalized biofilm mathematicalmodel. The effect of inlet parameters including concentration,flow rate, mass transfer coefficient and biofilm thickness wereinvestigated using the computer program developed. The numericalmodel was also applied to experimental data to demonstrate itsvalidity. In thin biofilms kinetic coefficients and otherparameters such as molecular diffusivity can be determinedbased upon experimental results. In thick biofilms, however, anadditional kinetic parameter or any other quantity related tomass transfer is a prerequisite in the evaluation ofexperimental data.     

A Study on Performance Characteristics of Suspended Growth Systems

A numerical model is presented to determine hydraulic and solids residence times and effluent concentrations from activated sludge reactors systems. Mass balance equations for biomass and substrate are numerically solved to determine the effects of different variables. Dimensionless quantities and computer techniques are used to express the results generally. Monod kinetics and reactors-in-series principles are applied to explain variations in axial dispersion andwastewater quality experienced in real systems. By means of the numerical approach, the variation of the ratio between the hydraulic residence time of a given reactor and that of an equivalent plug-flow tank with the same inlet and outlet conditions is investigated. Using the numerical results obtained, graphs are plotted for designing plug-flow activated sludge systems. Experimental data reported in literature is also evaluated to demonstrate the cases where the existing classical solution to the problem differs from the exact results.