As the total sink flowrates (SK1+SK3) in contaminant cascade ’A’ has the highest flowrate, the design methodology is performed on contaminant cascade ’A’ first. The design methodology starts with SK1 first. The source ranking order based on contaminant ’B’ is SR1->SR2->SR3->SR4. Figure 7a first presents the source and sink CCs specifically for SK1. Notice that the Pinch occurs at contaminant ’B’, with required freshwater as 18.4 t/h.

According to the proposed source allocation methodology in Section 2.4 and 3, since the Pinch does not occur at the sink’s main limiting contaminant ’A’ - step (i), as well as SR1 and SR2 are conflicting sources, there is still room for freshwater reduction. SR1 allocated to SK1 can be reduced. Using the graphical strategy presented in Section 2.4, SR1 can be reduced until the distance of sink CC to source CC for both contaminants are identical. The source CC is then shifted to the left. Figure 7b shows the source and sink CCs with reduced SR1. Otherwise, using the procedure from Section 3, the step (ii) from the source allocation step can be performed. Since this involves two contaminants, pair with two sources from the arranged source, i.e. SR1 and SR2. In step (iii), use Eqs(4-5) to determine the flowrates of SR1 and SR2 to be allocated to SK1. As this is only two contaminants, setting the freshwater requirement- Eq(4) for A to be equal to B is enough. In step (iv), the flowrates of SR1 and SR2 that can be allocated to SK1 needs to be checked. The determined flowrates are found a: SR1=3.45 t/h and SR2=2.875 t/h. As both flowrates are not negative and are less than the available flowrates, the step for SK1 is completed. The procedure is then repeated for SK3 – step (vi). It can be noticed that the freshwater requirement is reduced to 16.675 t/h, with only 3.45 t/h of SR1 to be allocated to SK1- see Figures 9.