Adjustment of Reactor Model in Organic Matter Removal from Wastewater Applying Numerical Residence Time Distribution Analysis

Abstract

Mass balance models in wastewater treatment may overpredict the organic matter degradation in aerated basins, because the simulation tools apply simplified reactor models, which could not represent the actual hydrodynamic and mixing conditions in the reactors. Ineffective reactor zones, short hydraulic circuits could have an effect on the actual performance of treatment process. In this paper, a wastewater treatment plant with a capacity of 10 MLD was investigated, where residence time distribution (RTD) analysis performed with computational fluid dynamics tools determined the actual time for biodegradation, and the biokinetic model could be updated. For the numerical RTD analysis 3D transient multiphase flow with turbulence closure was applied, whereas mass balance modelling used GPS-X simulation tool calibrated by field data. The model results were in good agreement with the measured chemical oxygen demand, total suspended solid values in treated effluent, and this method highlighted the importance of extension of mass balance modelling with hydrodynamic calculations.