Phytoremediation Potential of Water Hyacinth for Removal of Chromium From Tannery Effluent

Abstract

Tannery effluent from chrome tanning carries chromium, mostly as trivalent chromium, together with salts, sulfide and a heavy load of organic matter, and its treatment is a persistent problem for small and medium tanneries. Water hyacinth (Eichhornia crassipes), a fast-growing floating plant that takes up metals through its roots, is often proposed as a low-cost way to strip chromium from such water. This narrative review asks what published work does and does not show about that proposal. It draws on literature on chromium chemistry and toxicity, on phytoremediation and rhizofiltration, on the biology and ecological risks of water hyacinth, and on studies of metal uptake by this plant, and it reports no new data. The evidence shows that water hyacinth can concentrate chromium, mainly in its roots, and that part of the removal is simple sorption rather than metabolic uptake. Most of it comes from short experiments with clean synthetic solutions, so it says little about real effluent, where salinity, organic load, competing ions and chemical form change both toxicity and uptake. Questions of mass balance, long-term plant health, safe disposal of metal-laden biomass and invasive-species risk are seldom answered together. The review concludes that water hyacinth is best regarded as a polishing or pre-treatment step to be tested on site, and it sets out what a credible pilot would need to measure.