rhizofiltration

Rhizofiltration is a phytoremediation technique that uses plant roots to remove contaminants from polluted water. It targets dissolved pollutants in groundwater, surface water, or wastewater and relies primarily on the sorption of contaminants to root surfaces, with some accumulation in root and shoot tissues. The approach is particularly capable of removing inorganic contaminants such as heavy metals and radionuclides from aqueous sources.

Mechanism and design: contaminants bind to functional groups on root cell walls and mucilaginous substances, a process known as biosorption. Plant roots provide a large reactive surface area and can create microenvironments that enhance uptake. In some cases, limited translocation into plant tissues occurs. Rhizofiltration systems can be implemented in situ, by cultivating plants in waterlogged beds or trench-like configurations that intercept contaminated water, or ex situ, in tanks or constructed wetlands where water is circulated through an established root zone.

Plant species and applications: fast-growing, metal-tolerant species are commonly used. Sunflowers (Helianthus annuus) have been widely studied, along with willows (Salix spp.), poplars (Populus spp.), reeds, and Indian mustard (Brassica juncea). The technology is applied to dilute yet large-volume water streams, groundwater plumes, and industrial effluents, where it can work in tandem with other remediation methods.

Operations and limitations: after treatment, the contaminated biomass must be harvested and disposed of as hazardous waste to prevent re-release. Rhizofiltration is most effective for low-to-moderate contaminant concentrations and clear water streams. Limitations include dependence on favorable water chemistry, plant health, and the need for ongoing biomass management.