3.4. Nickel
In the wastewater samples, Ni concentrations ranged from
1.63 to 2.76 mg/L (Table 3) and exceeded the permissible limit
(1.0 mg/L) set by Pak-EPA (2000). The ANOVA analyses indicated
that the concentration of Ni in the out-let wastewater samples
was significantly lower (P L. gibba L. > P. glabrum > S. cypernius > E. cressipes > P.
australis > P. stratiotes > A. plantago-aquatica > J. articulatus > C.
aquatilis > C. demersum. However, bio-transformation of metallic
complexes is responsible for removal of heavy metals from
wastewater in a CW, because of enzymatic action that made the
metals more easily bioavailable to the plants