The second step is to classify the sinks into Above and Below Pinch
regions, for both contaminants ’A’ and ’B’. The source order for
contaminant ’A’ is: SR1->SR2->SR3-SR4, while
the source order for ’B’ is:
SR4->SR3->SR2-SR1.
The required step is to compute the ratio of shifted sink concentration
to the shifted source concentration
(Z*k,SKj/C*k,SRi) for each sink-source
pair and for each contaminant ’k’. Table 4 shows the computation
results. For SK1 and SK3, as all the minimum ratios paired with SR1,
SR2, SR3 and SR4 are less than 1, they are impossible to be fulfilled by
merely internal sources. This is because the concentrations (either A or
B) of these sources are all higher than both of the sinks. For SK3,
although SR2 has lower concentrations of A and B than SK3, the source
flowrate is not enough to cover SK3. So, they require freshwater and
should be classified as Below the Pinch in contaminant ’A’ Composite
Curve. While for SK2 and SK4, the minimum ratios for both sinks to all
sources are less than 1, which means they should be classified as sinks
that belong to below the Pinch Region.
Table 4: Determination of sink-to-source concentration ratio. The
minimum value among the contaminants are highlighted in bold