Pilot scale continuous reactor for water treatment by electrochemical advanced oxidation processes: Development of a new hydrodynamic/reactive combined model

The development of continuous flow electrochemical reactors is required to overcome the limitations of conventional batch reactors for treatment of large flows of effluents. Therefore, the objective of this study was to develop and characterize a new pilot-scale reactor using BDD anode and carbon felt cathode operating in continuous mode. First, a "Design of Experiment" analysis was performed in order to identify the most critical operating parameters for the percentage of mineralization of 29.8 mg L-1 hydrochlorothiazide (HCT) solution. The liquid flow rate has been identified as the most critical parameter together with the configuration of the reactor (number of electrodes, distance between electrodes). Moreover the designed reactor was able to reach very high percentage of mineralization (97%) for a mean residence time of 83 min. To better understand the important role of the flow rate and the configuration, a hydrodynamic study was then performed. "Residence Time Distribution" curves were obtained and fitted well with the continuous-stirred tank reactor in series with dead zones (CSTR-DZ) model. The 28-electrodes configuration had a lower dead volume fraction whatever the liquid flow rate applied. By increasing the liquid flow rate the hydrodynamic behavior tends more to a plug flow reactor. Finally, a new mathematical model for the mineralization of HCT solution was proposed by combining mineralization kinetic with hydrodynamic CSTR-DZ model. This model was then compared to experimental data and the model was able to capture experimental trends. This approach opens up interesting perspectives for a successful scale-up for continuous electrochemical reactors.