Removal of iron (fe) from industrial wastewaters by constructed wetlands: an application of water Hyacinth (EICHHORNIA CRASSIPES (mart.) solms) stands

Abstract

Severe contamination of water resources including groundwater with iron (Fe) due to various anthropogenic activities has been a major environmental problem in the industrial areas of Sri Lanka. At present Fe rich industrial' wastewaters are mostly treated with chemical precipitation. Moreover this technique is generally costly, depends on many intrinsic environmental parameters and requires intensive management and long-term maintenance. Hence the use of the obnoxious weed water hyacinth (Eichhornia crassipes (Mart.) Solms) in constructed wetlands to phytoremediate Fe rich wastewaters seems to be an appealing option. Although several studies have documented that hyacinths are good metal accumulating plants none of these studies have documented the effects of the nutritional status of the plants on the phytoremediation of metal rich industrial wastewaters. Hence in this paper we report the possible Fe removal efficiencies under different nutritional conditions of water hyacinth in batch type constructed wetlands. This study was conducted for 15 weeks by culturing water hyacinth in 590 I capacity fiberglass tanks under different nutrient concentrations of 2-fold (56 TN mg/l and 15.4 TP mg/l), l-fold, 112-fold, 114-fold and lI8-fold with Fe rich industrial wastewaters containing 9.27 Fe mg/l. A control set-up of hyacinths containing only Fe as a heavy metal but without any nutrients was also studied. A mass balance was conducted to investigate the phytoremediation efficiencies and to determine the different mechanisms governing Fe removal from the wastewaters