Removal of nitrogen and phosphorus from industrial wastewaters by phytoremediation using water hyacinth (Eichhornia crassipes (Mart.) Solms)

This paper elucidates the phytoremediation potential of water hyacinth (Eichhornia crassipes [Mart.] Solms) for TN and TP rich industrial wastewaters determined for 15 weeks under different set-ups of 2-fold (56 TN mg/l and 15.4 TP mg/1), 1 -fold, 1/2-fold, 1/4-fold and 1/8-fold and a control with no nutrients in duplicate. A mass balance was conducted to evaluate the phytoremediation efficiencies and to identify the key mechanisms of nutrient removal from the wastewaters. Our results manifested that water hyacinth is a promising candidate for a batch removal of TN and TP from wastewaters. 100% removal of both TN and TP was observed at the end of the 9th week in all the set-ups mainly due to assimilation and the period between 6-9 weeks became the optimum period after which complete harvesting is recommended. Plants having an age of 6 weeks are ideal to commence the free-floating wetland and 21 days hydraulic retention time (HRT) is recommended for optimum removal of TN and TP. Assimilation and denitrification were the key mechanisms of TN removal while assimilation and sorption became the prominent mechanisms in the removal of TP from wastewaters. Keywords Assimilation; denitrification; phytoremediation; total nitrogen (TN); total phosphorus (TP); water hyacinth (Eichhornia crassipes (Mart.) Solms)