Removal Of Metals By Phytoremediation

P.Suganthi II-M.Sc Eco biotechnology Bharathidasan University Trichy.

E-mail:[email protected]

What is bioremediation? • • • •

Bioremediation is a treatment process that uses naturally occurring microorganisms (yeast, fungi, or bacteria) to break down, or degrade, hazardous substances into less toxic or nontoxic substances. Microorganisms, just like humans, eat and digest organic substances for nutrients and energy. In chemical terms, "organic" compounds are those that contain carbon and hydrogen atoms. microorganisms can digest organic substances such as fuels or solvents that are hazardous to humans.

• What is phytoremediation? •

Phytoremediation can be defined as the use of green plants to remove pollutants from the environment or to render them harmless

Phytoremediation •

Phytoremediation is a form of bioremediation and applies to all chemical or physical processes that involve plants for degrading or immobilizing contaminants in soil and ground water.

• •

“Phyton“ = Plant (in greek) “Remediare“ = To remedy (in latin).

Types of phytoremediation Six main types They are……..

Types of Phytoremediation

Phytoaccumulatin

Phytostabilization

Phytodegradation

Rhizodegradation

Phytovolatilization

Rhizofiltration

The phytoextraction operation Chemicals added

Biopump grown

Ni

2+

+

Au

Cu

2+

Pd

2+

Plant material harvested and burnt to produce bio-ore

Bio-ore smelted

Bio-ore landfilled

Phytomining

Phytoremediation

Phytostabilization •

Phytostabilization is the use of plants to stabilize the soil matrix itself and immobilize the contaminant from future migration

•

Plants control pH, soil gases, and redox conditions in soil to immobilize contaminants.

•

Humification of some organic compounds is expected.

• Phytovolatilization •

Plants take up volatile compounds through their roots, and transpire the same compounds, or their metabolites, through the leaves, thereby releasing them into the atmosphere

•

.

• Phytodegradation •

Contaminants are taken up into the plant tissues where they are metabolized, or biotransformed.

•

Where the transformation takes place depends on the type of plant, and can occur in roots, stem or leaves.

Sugars and organic material into the soil Phytodegradation/stabilisation

Water and metals out of the soil Phytoextraction

Biopumps

• Phytoextraction – plant removal of: – – – –

water nitrates, phosphates heavy-metals some organic nasties

• Phytodegradation and stabilisation enhanced by: – soil aeration – plant exudates – soil microbiota stimulated by plant exudates

• •

Rhizodegradation It also called phytostimulation, rhizosphere biodegradation, or plant-assisted bioremediation /degradation, is the breakdown of contaminants in the soil through microbial activity that is enhanced by the presence of the rhizosphere.

•

Microorganisms (yeast, fungi, and/or bacteria) consume and degrade or transform organic substances for use as nutrient substances.

• •

Rhizofiltration It is the adsorption or precipitation of contaminants onto plant roots or the absorption of contaminants into the roots when contaminants are in solution surrounding the root zone.

•

The plants are raised in greenhouses hydroponically (with their roots in water rather than in soil).

Overview of Phytoremediation

Mechanisms for Organic and Inorganic

Sources of heavy metal in the environment Textiles Waste

Municipal and Industrial waste

Pesticides

Sediment from wastewater treatment plant

Development vs Environment & Health Industrialization Urbanization

Waste Water

AtmospherePrimary pollutants (NOx,VOCs) Secondary pollutants (oxidants, fineparticulates

Solid Waste

Intensive agriculture Soil

Plant

Agrochemicals

Water

Rapid development

Environment

Agro-products

Exhaust gases

Plant species………….of Phytoremediation Approximately 400 plant species from at least 45 plant families have been reported to hyperaccumulate metals

Water Hyacinth in Sewage Discharge Ponds •

Due to the growth of water hyacinth, excess nutrients in the water column are removed.

•

Heavy metals in the sewage water is also taken up by water hyacinth.

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This is most essential aspect of sewage water treatment, which requires no chemicals or, electrical energy.

•

Heavy metals cause many health hazards to human kind such as cancer, kidney disorder, hypertension, hormone imbalance (which has severe consequence on human reproductive mechanism), nervous disorder, etc. Under conventional treatment procedure, organic manure is produced before removing heavy metals

• •

Two problems are solved in a single step:

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Excess nutrients such as phosphorus and nitrate are removed

•

Toxic heavy metals are also removed from entering the ecosystem.

Phytoremediation of mixed-contaminated soil using the hyperaccumulator plant Alyssum lesbiacum: Evidence of histidine as a measure of phytoextractable nickel

Alyssum lesbiacum

Effects of Ni addition on shoot dry weight (a) and the concentration of Ni in the shoots (b). The concentration of Ni was determined with

ICP-AES

Phytostabilization of Mine Tailings in Arid and Semiarid Environments An Emerging Remediation Technology

Phytoremediation of Hexavalent Chromium Polluted Soil Using Pterocarpus indicus and Jatropha curcas •

• •

Phytoremediation of chromium polluted soil using local and potential plants poses a number of unique interlink advantages particularly for Surabaya as well as other big cities in Indonesia Pterocarpus indicus and Jatropha curcas were able to remediate hexavalent chromium polluted soil of less than 90 mg KgG1. Jatropha was planted in hexavalent chromium polluted soil because Jatropha could remediate higher concentration than Pterocarpus

Pterocarpus indicus

Jatropha curcas

Cont….

Metal Phytoremediation potential of Rhizophora mucronata

Cont………..

Improve Phytoremediation using Genetic Engineering. Metals • • • •

• • •

•

Introduce genes encoding transport proteins. IRT1 iron transporter MRP1 Mg-ATPase transporter High affinity Zn transporter from Thalassiosira weissflogii Introduce genes encoding metalsequestering proteins or peptides. Phytochelatins (e.g., cad1) Metallothioneins Introduce genes to enhance metal transport into roots, and from roots to other plant biomass. Genes encoding metal chelators

• • • • •

• •

Introduce genes to change the oxidation state of metals. mercuric reductases selenium methylation enzymes Organics Introduce genes encoding key biodegradative enzymes (plant and microbial origin). Laccases Dehalogenases

Before….….. After

Phytoremediation Advantages: - Low cost - Well suited for use at very large field sites - Transfer is faster than natural attenuation - High public acceptance - Fewer air and water emissions - Soils remain in place and are usable following treatment -

Compatible with engineered technologies

Phytoremediation Applications

Phytoremediation Limitations -

Long duration of time for remediation

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Not all compounds are susceptible to rapid and complete degradation

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High concentrations of hazardous materials can be toxic to plants

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Effective only for moderately hydrophobic contaminants

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Toxicity and bioavailability of degradation products is not known

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Potential for contaminants to enter food chain through animal consumption

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Hyperaccumulators are often slow growers

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Need to dispose plant biomass

Thank you