Identification and localization of hydrodynamic anomalies in a real wastewater treatment plant by an integrated approach: RTD-CFD analysis

The presence of hydrodynamic anomalies (HAs) in biological reactor reduces pollutants removal yields and increases management costs. This work aims to study the hydrodynamic behaviour of biological reactors of a real wastewater treatment plant (WWTP) in order to detect the presence of hydrodynamic anomalies (dead volume and bypass). The identification and the localization of these anomalies were conducted by an integrated residence time distribution (RTD) analysis - computational fluid dynamic (CFD) numerical analysis. From the results of the RTD analysis a dead volume of 30% was quantified without bypass. The three-dimensional CFD model revealed a dead volume inside the oxidation/nitrification tank equal to 10% located downstream of the baffle wall. Employing the RTD-CFD integrated analysis approach, the size of dead volume located in the denitrification reactor was quantified as equal to 60%. RTD analysis allowed for the quantification of the HAs while CFD analysis provided for the position of the HAs with reliable accuracy. RTD-CFD integrated approach is a preparatory tool for planning any corrective actions in a focused way in order to use all the volume of the reactor, maximizing the efficiency of the treatment processes, minimizing management costs and reducing the consumption of energy.