Plant, aquatic plant

Eichhornia crassipes (Mart.) Solms

Water hyacinth

A floating plant of extremely fast growth, with dense roots that hold metals from water. It is effective for cadmium, chromium and mercury in tanks, but in the European Union it is a banned invasive species: it can be used only in closed systems and where permitted.

Bernard DUPONT, CC BY-SA 2.0

How it works

Mechanisms: rhizofiltrationphytoextraction

Contaminants

Contaminant	Evidence	What was shown
Mercury	field	A pilot wetland plant for artisanal gold-mining wastewater (62.4 µg/L total mercury, 50 days, one-hour retention time): mercury lowered by 89%; thermal treatment of the biomass at 400 °C then separated on average 87% of the mercury from the tissues (Gomez et al. 2025). Gomez et al., Mercury removal from mining wastewater by bioaccumulation and thermal separation in Eichhornia crassipes, Environ. Sci. Pollut. Res. 32:798, 2025
Cadmium	laboratory	In solution, with six elements supplied singly (As, Cd, Cr, Cu, Ni, Se): it accumulates Cd and Cr best, Se and Cu moderately, As and Ni poorly. Highest Cd: 371 mg/kg in shoots and 6,103 mg/kg in roots (dry weight) (Zhu et al. 1999). Zhu et al., Phytoaccumulation of trace elements by wetland plants: II. Water hyacinth, J. Environ. Qual. 28:339, apis.ac.uk, 1999
Hexavalent chromium	laboratory	With chromium supplied as Cr(VI): up to 119 mg/kg in shoots and 32,951 mg/kg in roots (Zhu et al. 1999). Zhu et al., J. Environ. Qual. 28:339, apis.ac.uk, 1999

Contaminant

Evidence

What was shown

Mercury

field

A pilot wetland plant for artisanal gold-mining wastewater (62.4 µg/L total mercury, 50 days, one-hour retention time): mercury lowered by 89%; thermal treatment of the biomass at 400 °C then separated on average 87% of the mercury from the tissues (Gomez et al. 2025).

Gomez et al., Mercury removal from mining wastewater by bioaccumulation and thermal separation in Eichhornia crassipes, Environ. Sci. Pollut. Res. 32:798, 2025

Cadmium

laboratory

In solution, with six elements supplied singly (As, Cd, Cr, Cu, Ni, Se): it accumulates Cd and Cr best, Se and Cu moderately, As and Ni poorly. Highest Cd: 371 mg/kg in shoots and 6,103 mg/kg in roots (dry weight) (Zhu et al. 1999).

Zhu et al., Phytoaccumulation of trace elements by wetland plants: II. Water hyacinth, J. Environ. Qual. 28:339, apis.ac.uk, 1999

Hexavalent chromium

laboratory

With chromium supplied as Cr(VI): up to 119 mg/kg in shoots and 32,951 mg/kg in roots (Zhu et al. 1999).

Zhu et al., J. Environ. Qual. 28:339, apis.ac.uk, 1999

Limits

It is on the list of invasive alien species of Union concern (Commission Implementing Regulation EU 2016/1141): in the Union it may not be kept, grown, transported or released. Where it escapes it covers water bodies. Metal stays almost entirely in the roots, and the watery biomass must be harvested often and treated as contaminated waste. It does not tolerate frost.

Where it has been tried

Sukinda chromite valley

PhytoremediationField scale, 2012

Eichhornia crassipes, Brachiaria mutica

In-situ trial in the South Kaliapani mining area: water hyacinth and paragrass grown on chromite-contaminated effluent and soil, with measurement of chromium bioconcentration in the plants.

Outcome Over 100 days hexavalent chromium fell by 24–54% with water hyacinth and by 18–33% with paragrass; the highest bioconcentration factor and transport index values were recorded for water hyacinth.