The Al-WTR had a bulk density of 1.18 0.11 g cm3 and
a porosity of 45%, both of which are comparable to values of 0.7–
1.83 g cm3 (bulk density) and 30–54.4% (porosity) reported in
literature for potential candidate materials for wetland systems
(Roger, 2000; Drizo et al., 1999; Del Bubba et al., 2003). From the
PSD, the values of d10 and d60 and UC were computed to be 0.5, 1.8
and 3.6 respectively and these are consistent with several guidelines
for securing adequate hydraulic conductivity and minimizing
risk of clogging (Vymazal,1998; IWA, 2000). Qualitative assessment
of the elemental distribution on the surface of the Al-WTR by the
SEM–EDX showed the predominance of aluminium and this was
expected to highly influence its P adsorption ability (See Fig. 2
(top)).