Studies on removal of toxic heavy metals from water by Eichhornia crassipes

Under present investigation Eichhornia crassipes (water hyacinth) has been tested for removal of two important toxic heavy metals chromium (Cr) and zinc (Zn) from water under experimental conditions. The plant biomass was grown on pond water added with four concentrations of Cr and Zn, i.e. 5.0, 10.0, 15.0 and 20.0 mg/l for 2–15 days. The plant performed extremely well in removing the Cr and Zn from their solution. It was capable of removing up to 100% of zinc and chromium during 10–15 days incubation period. Addition of Cr and Zn at lower concentration (5.0 mg/l) was found harmless, without any symptom of toxicity even after 15 days, but at 10.0, 15.0 and 20.0mg/l of Cr, the plants have shown morphological symptoms of toxicity. The leaves started rotting, turned black and ultimately the whole plant decayed after12-15 days. On the other hand Zn was removed safely at concentrations 5.0 and 10.0 mg/l, but not at 15.0 and 20.0 mg/l, where they showed signs of toxicity and decayed after 15–20 days.