Application of a Mathematical Model for Activated Sludge Treatment

Abstract

The development and application of a dynamic mathematical model is discussed in the paper. The original model consisting of six differential and a few linear equations describes the biological processes, e.g. the biodegradation of carbonaceous material, growth of microorganisms, oxygen requirement of the activated sludge wastewater treatment. In the course of development a few constants involved in the model were transformed to variables. Thus the constants representing the different organic fractions of the wastewater as well as the temperature were replaced by variables or functions in the model describing continuous operation. Another transformation involved the value of the maximal substrate degradation rate constants, which is characteristic for certain operational conditions. The possibility for changing these values according to a function when approaching new equilibrium under new operational conditions (e.g. starting up of a plant or starting activated carbon addition) was provided. The model was supplemented by the Langmuir isotherm, thus it became capable of simulating the powdered activated carbon (PAC) addition process. Also, the Pflanz-equation concerning settling and recirculation was applied for the description of the continuous operation. The model, thus extended and run on personal computers, was verified on the basis of both batch and continuous experiments. The first industrial application of the model has been carried out in the Nitrochemical Works, for an in-situ experiment.