Eco-friendly management of wastes

1. Adnan shakeel
M.Sc botany (Env. biology)
En. No. GH1717

2. Introduction
 Phytoremediation (phyto - plant, remedium – restoring
balance) is the name given to a set of technologies that clean
contaminated sites using plants.
• Phytoremediation relies on plant’s ability to act as a solar –
driven pumping and filtering system.
 Heavy metal pollution is a serious environmental problem.
Since heavy metals are non-biodegradable ,they accumulate
in the food chain.
 Some important disasters caused by heavy metals are;
Minamata disater, Sandoz chemical spill, Spanish waste water
spill and itai itai disease

3. Brief historical view
 About 300 years ago, plants were used in waste water
treatment. Thlaspi caerulescens and Viola -
calaminaria were the first plant species documented
to accumulate high levels of metals in leaves.
 Utsunamiya and chaney first made a field trial on Zn
and Cd phytoextraction in 1991.
 1935, Byers reported that plants of the genus
Astragalus were capable of accumulating up to 0.6
selenium in dry shoot biomass.

4. Process of phytoremediation

5. Phytostimulation
 Degradation of the contaminant by plant rhizosphere
microorganisms.
 Media: Mainly soil, sediment and sludge but also
surface and ground water
 Examples: Grasses, hybrid poplar, red mulberry, alfalfa,
cattails

6. Phytodegradation
 Degradation of the contaminant through plant
matabolism or through the release of enzymes by
the plant.
 Media : Soil, sediment, sludge, ground and surface
water.
 Examples : Algae,, stonewarts, hybrid poplar, rice,
cattails.

7. Phytoextraction
 Plants accumulate metals and radio-nuclides and
translocate them to their harvestable parts.
 Media : Soil, sediment and sludge.
 Examples : Indian mustard, alpine pennycress, sun
flower, poplars.

8. Rhizofilteration
 Plants absorb or precipitate metals and radionuclides
from aqueous solutions around the roots, therefore
immobilizing the contaminants.
 Media : Surface or ground water
 Examples : Sunflower, Indian mustard, water hyacinth.

9. Phytovolatization
 Uptake and possible transformation of a compound
by the plant and subsequent release into the
atmosphere
 Media: Ground water, soil, sediment, and sludge
 Examples : Poplar, alfalfa, Indian mustard

10. Phytostabilisation
 Stabilisation of the metal-contaminated soil by
plant roots, reducing the movement off-site.
 Media : soil
 Examples : Indian mustard, grasses, hybrid poplars.

11. Plants used in
phytoremediation
 Alfalfa is living in symbiosis with hydrocarbon-degrading
bacteria. Arabidopsis can transform Hg into gaseous
state.
 Bamboo family can accumulate silica in its stalk. Bladder
campion can accumulate Zn and Cu.
 Indian mustard can accumulate Se, Pb, Cr, Cd, Ni, Zn and
Cu.
 Buxaceae and Euphorbiaceae can accumulate Ni. Tomato
and alpine pennycress can accumulate Pb, Zn and Cd.
Poplar is used for the absorption of the atrazine.

12.  Cadmium, using Salix viminalis, cadmium and zinc using alpine
pennycress (Thlaspi caerulescens).
 Lead, using Indian mustard (Brassica juncea), Ambroisa
artemisifolia and poplar trees.
 Arsenic, using the sunflower ( Helianthus annus), or Chinese
Break fern (Pteris vittata).
 Caesium-137 and stromium-90 were recovered from a pond using
sunflowers.
 Mercury, selenium, and organic pollutants like polychlorinated
biphenyls have been removed by using transgenic plants
containing genes for bacterial enzymes.

13. Role of biotechnology and genetics in
phytoremediation
 Selenium (Se) : Transgenic plants have been produced
through methylation of amino acids at specific sites
which have the ability to volatize Se.
 Mercury (Hg) : Transgenic tobacco has been produced due
to the integration of certain bacterial genes like merA and
merB due to which it shows resistance to Hg
 Arsenic (Ar) : Certain bacterial genes present in E.coli,
such as ArsC is responsible for reduction of arsenic and
formation of a complex in presence of glutathione (GSH).
An increased amount of GSH can be produced by
expression of glutamyl cysteine synthetase enzyme.

14. Advantages and disadvantages
Advantages Disadvantages
1. Natural method. 1. long clean-up process.
2. Suitable for broad 2. Uncertain performance.
range of contaminants.
3. Cost effective for large 3. Not applicable for every
land areas where other site (deep wastes, ana-
technologies are not feasible. erobic soils, etc.)
4. Sensible, appropriate and 4. Regulatory hurdles
sustainable technology.

15. Field Scale Applications
 Recovery of heavy metals from soil : Brassica juncea and
its modified strains have been shown to accumulate up to 40%
of their biomass as heavy metals such as lead and chromium
 .
 Researchers in the state of New jersey in U.S.A carried out field
trials in 1994 and demonstrated that the plants could be safely
grown in chromuim contaminated soil at a site adjacent to
Liberty State Park, N.J.A. Small amount of chromium was
taken by the plants and removed from the soil. The plants were
then harvested and metal was recovered.
 Currently Indian mustard is under work at various research
centers of U.S.A, to optimise metal uptake by such modified
brassica strains.

16.  Treatment of muncipal wastewater and
industrial wastes : Roots and rhizomes of some
plants provide an ideal habitat for the growth of various
kinds of microorganisms. These microbes are very
effective in remediation of contaminated wastewater
and industrial wastes.
 In U.S.A, Albermarle’s two bromine plants in magnolia,
has been artificially designed by suitable plant species
to study the potential of plants in wastewater
treatment.
 The plant species used are; Scirpus lacustris, maiden
cane and Typha latifolia.