Modelling of Aerating –Permeation Combined Process for VOCs Removal and Recovery from Polluted Wastewater

This study deals with modelling of aerating - permeation process for removal of VOCs from wastewater. The hybrid process allows desorbed VOCs from aerating process to be subsequently recovered using a membrane based vapour permeation process. A mathematical model has been developed to describe the mass transfer in both processes based on the resistance in series model. The separate evaluation of feed phase and membrane phase resistances has been carried out at different feed hydrodynamic conditions in a constant membrane thickness. A sensitivity analysis has been carried out using the developed model to investigate the effects of operational factors such as temperature, pressure, feed concentration, gas and liquid flow rate on separation performance of the process. As typical cases, removal of four VOCs, i.e. 1,2-dichloroethane (DCE), 1,1,2-Trichloroethane (TCE), Chloroform and Dichloromethane from water was investigated in a hybrid process consist of a stripping column of 90 cm height and vapour permeation unit employing PDMS membrane with an effective area of 14.7 cm2. The results indicated that while the gas phase resistance was negligible in air stripping process, it played a significant role in vapour permeation process, especially in feed side. The modelling results demonstrated that the air/water ratio has a great impact on the removal efficiency of air stripping process, but it should be limited to prevent flooding. The examination of the hybrid model has shown that the hybrid process has high efficiency for high concentrations, high gas flow rates and optimal temperature.