3.3. Iron
Table 3 shows the Fe concentrations (0.07–0.27 mg/L) in
wastewater samples collected from in-let, all cells and out-let of the
CW and found within the permissible limit (2.0 mg/L) set for
industrial and sewage wastewater (Pak-EPA, 2000). However, the
Fe concentrations in the out-let wastewater samples were significantly
lower (P< 0.01) than in-let of the CW, indicating that the CW
has been also effectively removed Fe from the wastewater. These
findings are consistent with those observed by Maine et al. (2009).
In sediment samples, the concentrations of Fe ranged from 1.0 to
1.7 mg/kg and significantly (P < 0.01) decreased as the distance
increased from in-let towards out-let of CW. Fe concentration was
3–4 folds high in the in-let samples as compared to out-let. Like Pb
and Cd, the interaction between concentrations and distance was
significant for in-let and out-let samples. The Fe removal efficiency of the CWwas 74.1%, higher than those (47%) reported by Jayaweera
et al. (2008) and consistent with those reported by Maine et al.
(2009). It means that the CWwas very effective in the removal of Fe
from wastewater. In general, these findings are in agreement with
those of Ye et al. (2001a,b) and O’Sullivan et al. (2004) but in
contrast with those reported by Lesage et al. (2007).
Table 5 summarizes the uptake and accumulation of Fe by plants
and their concentrations varied from species to species. The Fe
concentrations in aerial and root tissues were ranged from 1.0 to
2.8 mg/kg and 2.7 to 5.7 mg/kg, respectively. These values are lower
than those reported by Lesage et al. (2007) in the plants collected
from CW treating domestic wastewater in Flanders, Belgium. This
may be due to the lower initial Fe concentrations and other physiochemical
properties of wastewater treated in that CW. The
highest Fe concentrationwas found in the C. aquatitis, T. latifolia and
C. demersum species with RCF 4.6, 4.6 and 4.4, respectively, and ACF
2.5, 1.9 and 2.3, respectively (Table 6). These plant species can be
used for phytoremediation of Fe contaminated wastewater. Earlier
study conducted by Jayaweera et al. (2008) indicated that chemical
precipitation and rhizofilteration are the key mechanisms to
remove Fe from Fe-rich wastewater.