Fig. 5 shows a plot of the removal efficiency for RP and SRP in the
five systems as a function of pore volumes. Note that all the
columns have different substrate configuration as listed in Table 1.
A clear influence of the proportion of Al-WTR can be observed in
the pattern of the removal efficiencies. All the columns removed P
effectively particularly over the first 100 pore volumes during
which average influent P was 18.5 mg P L1 (RP) and 10.0 mg P L1
(SRP). During this period, average removal efficiencies for the
columns were 91.2, 91.3, 90.9, 88.9, 93.2% (RP) and 92.7, 94.8, 94.8,
93.1 and 95.4% (SRP) for columns 1–5 respectively. Columns began
to lose the P adsorptive capacity after variable lengths of time. This
was particularly evident in column 4, which had the least proportion
of the Al-WTR in composition (40%).