3.5. Chromium
Cr concentrations in wastewater samples ranged from 0.07 to
0.35 mg/L (Table 3). In the samples from in-let to cell-3, Cr
concentrations were exceeded the permissible limit (0.1 mg/L) set
for industrial and sewage wastewater (Pak-EPA, 2000), while its
concentrations in the samples from cells 4–7 and out-let were
within the permissible limit. Furthermore, Cr concentrations in the
out-let wastewater samples was significantly lower (P < 0.001)
than in in-let of the CW, indicating that the CW has effectively
removed the Cr from wastewater. Cr concentrations ranged from
0.4 to 1.3 mg/kg in the sediment samples (Table 4). Like other
metals, Cr concentrations were also shown decreasing trend as the
distance increased from the in-let towards out-let. These results are
comparable with those reported by Lesage et al. (2007) and are
contrary with those reported by Mays and Edwards (2001). The Cr
removal performance of the CW was 89% (Table 3), which is
consistent with the findings (82%) of Hadad et al. (2006). The Cr
concentrations were 5 folds high in the in-let samples as compared
to out-let and reduced to permissible limits before entering in to
cell-3. Plant uptake and accumulation of Cr varied from species
to species, as given in Table 5. Cr concentrations ranged from 0.4 to
1.2 mg/kg in aerial tissues and from 1.4 to 2.3 mg/kg in root tissues.
The highest Cr concentration was found in the A. plantago-aquatica
species with RCF and ACF of 3.5 and 2.0, respectively (Table 6). On
the basis of Cr hyperaccumulation, this plant species along with
other hyperaccumulators can be used for phytoremediation of Crrich
wastewater.