# Practical Methodology for a Three-Dimensional-Printed Hybrid Desalination System
## 3 Results
### ED Reactor Characterization  
The efficiency of the constructed ED reactor was evaluated through desalination experiments using a NaCl solution of 10 g/L initial concentration, with a total volume of 1 L. This concentration represents typical brackish water conditions (1-10 g/L). Desalination of brackish water is of great interest for agricultural and domestic applications, where moderate salinity levels need to be reduced in an energy-efficient manner. An ERS consisting of 0.2 M NaCl was prepared to ensure consistent conductivity around the electrodes, facilitating proper electrochemical performance throughout the experiment. The experimental setup included the use of a unit cell to characterize the ED system. The ED reactor was paired with a power source that applied a constant theoretical potential of 0.1 V, equivalent to the electrical potential of a RED unit cell. This setup aimed to simulate conditions similar to a hybrid ED-RED system, with the specific purpose of evaluating the minimum desalination capability of the ED reactor. The applied voltage provided the necessary driving force for ion migration across the membranes, ensuring effective desalination during the process.  
Figure 7: Effect of flow rate on open-circuit potential and power density in RED characterization.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Evaluation** & **OCP (V)** & **J (A/m2)** & **P4 (W/m2)** \\ \hline Theoretical model & 0.100 & 3.40 & 0.085 \\ Experimental result & 0.092 & 1.76 & 0.077 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison between theoretical model and experimental results of RED reactor performance.  
Higher flow rates improve desalination efficiency by reducing concentration polarization near the membrane surfaces, thereby enhancing ion transport across the compartments. Studies, including those by [34, 35], demonstrate that increased flow rates decrease the thickness of the boundary layer, reducing resistance to ion migration and preventing ion buildup that otherwise hinders desalination. This effect allows for more efficient desalination, especially at higher initial salt concentrations. Desalination experiments were conducted over 60 min, with electrical conductivity measurements taken every 10 min to monitor the progression of salinity changes in both the desalinated and brine compartments. The initial conductivity in all reservoirs was set at 16.6 mS/cm. The results are illustrated in Figure 8, which depicts the variation in conductivity observed during the experiments conducted at different flow rates, ranging from 20 to 80 mL/min. The desalinated water compartment showed a consistent decline in conductivity over time, while the brine compartment experienced a corresponding increase. These trends demonstrate the direct impact of flow rate on the efficiency of ion transport between compartments.  
The experimental data indicate that increasing the flow rate enhances the efficiency of the desalination process. Specifically, at the highest tested flow rate of 80 mL/min, the conductivity in the desalinated compartment decreased to a minimum of 14.53 mS/cm, corresponding to a salt removal efficiency of 12.46% over the one-hour experimental duration, as summarized in Table 4. These results demonstrate a positive correlation between flow rate and desalination efficiency, underscoring the importance of optimizing flow parameters to maximize ion removal and improve the overall effectiveness of the ED system.