ABSTRACT

Phytoremediation has been defined as “the use of plants and associated soil microbes to reduce the concentrations or toxic effects of contaminants in the environments.” This cost-effective technology mainly comprises phytoextraction (or phytoaccumulation), phytofiltration, phytostabilization, phytovolatilization, phytodegradation, rhizodegradation, and phytodesalinization. Various floating, submerged, emergent, and other forms of aquatic macrophytes can remove heavy metals and metalloids from water. Besides vascular plants, various species of algae can also accumulate heavy metals and metalloids. Wetlands can serve as both sinks and sources of heavy metals, and constructed wetlands are used for the remediation of heavy metal/metalloid-contaminated water and wastewater. Bioremediation mediated by both indigenous and genetically engineered microorganisms also offers immense possibilities. Consortia of microorganisms are found to be more efficient than a single species or strain. Recombinant DNA technology can be used to engineer metallothioneins into microbes to enhance their heavy metal-chelating ability. Supplementing microbial biomass with substances like surfactants can also augment biosorption efficiency for arsenate removal. Fungi have been found to serve as biocatalysts that can help in transforming heavy metals into less toxic compounds in industrial effluents and wastewater.