Modeling and calculations of waste water treatment from nitrogen compounds in bioreactors with the use of biofilm models

Abstract

The mathematic model and calculations of the waste waters cleaning parameters from the compounds ammonium nitrogen (nitrification) in bioreactors with the additional using of the fixed biocenosis as the biofilm in their volume are proposed. The valuation of the different influence factors on the waste waters cleaning parameters is given. The kinetics of reaction according to the Monod nonlinear equation is used that allowed us to calculate the nitrogen concentrations on the external and internal biofilm surfaces and to evaluate the efficiency of the biofilm work of the given thickness relative to the penetration character of the nitrogen pollutions in it. At this, the substrate flow and the penetration depth into the biofilm are functions of the substrate concentration on the biofilm surface, rate of the reaction within it, and the diffusive mass transfer. As a main parameter for the evaluation of the oxygen influence for the control over the process of ammonium oxidation to nitrite, the relation of the concentrations oxygen to ammonium nitrogen is proposed. The specific examples and calculations have showed that the given relation may be a better alternative for the control over the nitrification processes in the reactor in comparison with oxygen concentration.