## 3 Results and Discussion
With the 3:2 configuration and a \(P_{\rm in}\) of 8 kW, an \(R\) of about 77% can be observed in Figure 5 compared to a value of about 64% in Figure 6. Naturally, this also affects the production of the system and its efficiency. Figure 4: Permeate production for different BWRO configurations using sample 11 (Table 1) as \(C_{\rm f}\). Figures 7 and 8 show the operating points that maximize \(Q_{\text{P}}\) for the BWRO configurations 1:0, 2:1 and 3:2, considering the \(C_{\text{f}}\) of samples 20 and 11, respectively. It can be observed that with higher \(C_{\text{f}}\) the curves are closer together and even intersect. Another factor affected by \(C_{\text{f}}\) is the appropriate \(P_{\text{in}}\) (for maximizing \(Q_{\text{P}}\)) range using each configuration. This range is notably lower for configurations 1:0 and 2:1. The operating curves of the 2:1 and 3:2 configurations are so close that a jump from 1:0  
Figure 5: \(R\) for different BWRO configurations using sample 20 (Table 1) as \(C_{\text{f}}\). Figure 6: \(R\) for different BWRO configurations using sample 11 (Table 1) as \(C_{\text{f}}\). to 3:2 can be made directly depending on the trend of \(P_{\text{in}}\). It can be observed that the curves are longer for the feedwater with higher \(C_{\text{f}}\) than for sample 20 (lower \(C_{\text{f}}\)). This is because at lower \(C_{\text{f}}\), SWMMs produce more \(Q_{\text{p}}\) and are more likely to not meet the \(Q_{\text{r-min}}\) constraint or exceed the \(Q_{\text{p-max}}\) per SWMM. The BWRO system operation with higher \(C_{\text{f}}\) allows a wider operating range without exceeding the imposed constraints but producing a lower \(Q_{\text{p}}\) with the same \(P_{\text{in}}\). Figure 8: Curves of maximum \(Q_{\text{p}}\) for different BWRO configurations using sample 11 (Table 1) as \(C_{\text{f}}\). Figure 7: Curves of maximum \(Q_{\text{p}}\) for different BWRO configurations using sample 20 (Table 1) as \(C_{\text{f}}\). Table 2 shows the range of \(P_{\text{in}}\) in which each BWRO configuration should be applied considering five samples (20, 5, 22, 3 and 11 (Table 1)) representing different \(C_{\text{f}}\) of the studied groundwater well. Some overlap was considered in \(P_{\text{in}}\) to avoid excessive configuration changes, depending on the \(P_{\text{in}}\) trend (increasing or decreasing). It should be mentioned that some operating points that were very close to the constraints established by the membrane manufacturer were removed to avoid instabilities in the operation of the BWRO system. This is the main reason why higher \(P_{\text{in}}\) was required for lower \(C_{\text{f}}\) in addition to the selected \(p_{\text{f}}\) and \(Q_{\text{f}}\) steps that eliminate some possible operating points. The \(P_{\text{in}}\) required depends, among other things, on the osmotic pressure of the feed solution, which in turn not only depends on the amount of \(TDS\) but on its inorganic composition. Table 3 shows the \(R\) range for each configuration. These values are important as the reference for the on/off percentages of the RO concentrate valve (Figure 1). The data of the operating points for maximizing \(Q_{\text{P}}\) using configurations 1:0, 2:1 and 3:2 for the five samples shown in Tables 2 and 3 can be found in Appendix A. **Author Contributions:** Formal analysis, A.R.-G.; investigation, A.R.-G.; writing--original draft preparation, A.R.-G.; writing--review and editing, A.R.-G. and I.N. ; supervision, I.N. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was not funded. **Conflicts of Interest:** The authors declare no conflict of interest.