Transcript - PMAS-Arid Agriculture University Rawalpindi

Contents
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Phytoremediation
Plants used for
Phytoremediation's
How does it work?
Mechanisms
Phytotransformation/Phytod
egradation
Phytoextraction
Phytostabilization
Rhizofiltration
Rhizosphere Bioremediation
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Over all Phytoremediation’s
Transgenic Plants Use for
Phytoremediation's
Aquatic plants for wastewater
treatment
Effects of Some Heavy Metals
on Human Health
Contaminant removal mechanisms
Advantages and Disadvamtages
Conclusions
References
Green
technology that uses plants systems for
remediation and restoration.
Consist
of microbial degradation in rhizosphere as
well as uptake, accumulation and transformation in
the plant.
Current Methods
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Current methods mainly remove and transport to
land fill or pump and treat type systems.
Many sites are large and pollution is not high but
still violates standards.
For secondary or tertiary treatment of waste
water.
Phytoremediation
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Phytoremediation is the direct use of living green
plants for in situ, or in place, removal, degradation,
or containment of contaminants in soils, sludge's,
sediments, surface water and groundwater.
Phytoremediation is:
It a low cost, use solar energy driven cleanup
technique.
Most useful at sites with shallow, low levels of
contamination.
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Useful for treating a wide variety of
environmental contaminants.
Effective with, or in some cases, in place
of mechanical cleanup methods.
Plants used for Phytoremediation's
Conti…
How does it work?
- Plants in conjunction with bacteria and fungi
in the rhizosphere
 transform, transport or store harmful chemicals.
- Plants attributes make them good candidates
 root system surface area to absorb substances and
efficient mechanisms to accumulate water,
nutrients and minerals.
 selectively take up ions
 Plants developed diversity and adaptivity to
tolerate high levels of metals and other pollutants.
Mechanisms
Phytotransformation/Phytodegradation
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Pollutant is taken up by the plant and
transformed in plant tissue (to be effective
must be transformed to a less toxic form).
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Trichloroethylene
(TCE), a prevalent ground
water contaminant, transformed to less toxic
metabolites by using hybrid poplar tree.
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Air Force facility in Texas using cottonwoods
to treat a large ground water plume of TCE.
EPA research lab using parrot feather (a
common aquatic weed) for TNT (Treating
New Targets) treatment.
Phytoextraction
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Uptake of chemical by the plant.
Works well on metals such as lead, cadmium,
copper, nickel etc.
Detroit lead contaminated site was removed with
Sunflower and Indian Mustard.
- recently researchers at the University of
Florida have determined that a species of
fern, native to the south east, stores high
concentrations of arsenic in its fronds and
stems more than 200 times the concentration in
the soil.
Phytostabilization
Involves the reduction of the mobility of heavy
metals in soil.
Immobilization of metals can be accomplished by
decreasing
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wind-blown
minimizing
dust,
soil erosion,
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Reducing contaminant solubility or
bioavailability to the food chain.
Trees transpire large quantities of
water (more than 15 gal/day) so
pumping action prevents contaminants
from migration into the water table.
Rhizofiltration
Use the extensive root system of plants as a
filter.
 1995, Sunflowers were used in a pond near
Chernobyl (City name).
- approx. 1 week they had hyperaccumulated
several thousand times the concentration of
cesium and strontium.
- hyperaccumulation can contain 100 times or
more of contaminant than normal plant.
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Rhizosphere Bioremediation
- Increase soil organic carbon, bacteria, and
mycorrhizal fungi, all factors that
encourage degradation of organic chemical
in soil.
- The number of beneficial bacteria increased
in the root zone of hybrid poplar trees and
enhanced the degradation of BTEX, (benzene,
toluene, ethylbenzene, and xylenes)
organic chemical, in soil.
Rhizofiltration
Applicability
A suitable plant for rhizofiltration applications
can remove toxic metals from solution over an
extended period of time with its rapid-growth root
system.
 Various plant species have been found to
effectively remove toxic metals such as Cu2+, Cd2+,
Cr6+, Ni2+, Pb2+, and Zn2+ from aqueous solutions.
 Low level radioactive contaminants also can be
removed from liquid streams.
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Rhizofiltration (cont.)
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Limitations
Rhizofiltration is particularly effective in applications
where low concentrations and large volumes of water
are involved.
Data Requirements
- Depth of contamination,
- Types of heavy metal present,
- Level of contamination must be determined and
monitored.
- Vegetation should be aquatic, emergent, or
submergent plants.
- Hydraulic detention time and sorption by the plant
roots must be considered for a successful design.
Rhizofiltration (cont.)
The example of an experiment
The plant root immersed in flowing contaminated water until
the root is saturated.
 The metal concentrated in the roots was analyzed on a dry
weight basis using Atomic Absorption
Spectrophotometry(AAS).
 The amount to metal taken up by the roots from various
solutions was compared on the basis of recovery rate (µg
metal in roots/µg metal in solution) and bioaccumulation
coefficient (ppm metal in roots / ppm of metal in solution).
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Rhizofiltration (cont.)
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Other factors that should be considered
- Potential of failure modes and contigencies
Rhizofiltration may not succeed for a number of reasons,
including mortality of plants for reasons such as
management, weather extremes, soil conditions or pest.
- Field studies
Field studies are required before full-scale application.
Specific information include rates of remediation, irrigation
requirements, rates of soil amendments, and plant selection.
Formulating clear objectives, appropriate treatments,
experimental units and planning are important considerations in field
studies.
- Economic
This technique should be less cost than traditional technologies such
as excavation, thermal desorption, landfilling etc.
Over all Phytoremediation’s
Transgenic Plants
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Most recent advances in phytoremediation is the
development of genetically modified plants able to
take up and degrade contaminants.
With increased understanding of the enzymatic
processes involved in plant tolerance and
metabolism of xenobiotic chemicals,
there is new potential for engineering plants with
increased phytoremediation capabilities.
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Several transgenic plant species are being
developed with phytoremediation applications in
mind.
Tobacco plants containing a human P450 2E1 were
able to transform up to 640 times the amount of
TCE compared with control plants.
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They also showed increased uptake and
metabolism of ethylene dibromide, another
halogenated hydrocarbon commonly found in
groundwater.
Higher tolerance to the explosives.
Aquatic plants for wastewater
treatment
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Aquatic plants are chosen for absorb particular
nutrient and to remove pathogens, metals and
other contaminants from wastewater.
Aquatic plants have been shown to be very
effective as a secondary or tertiary state for
water treatment and nutrient removal.
Living Environment of Aquatic Plants
Rivers
Lakes
Where do
they live?
Constructed Wetlands
Hydroponic systems
Mechanisms of aquatic plants phytoremediation
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Inorganic pollutants
• Rhizofiltration
• Phytostabilization
• Phytoextraction
Organic pollutants
• Phytodegradation
• Phytovolatilization
• Rhizodegradation
Aquatic plant for waste water
treatment
Water Lily has an extensive root system with rapid
growth rates, but is sensitive to cold temp, it is an ideal
plant for water treatment in warm climates.
 Duckweed (Lemma spp.) has greater cold tolerance and a
good capacity for nutrient absorption.
 Penny wort (Hydrocotyl spp) is relatively cold tolerant
with a very good capacity for nutrient uptake.
 Water hyacint uptake of heavy metal eg.,Pb,Cu,Cd,Hg
from contaminated water.
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Function of plants in aquatic treatment
Plant Parts
Roots
and/or stem
in water column
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Stem and/or
leaves at or above
water surface
Functions
Uptake of pollutants
 surfaces on which bacteria grow
 media for filtration and adsorption of
solids
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Attenuate sunlight, thus can prevent
growth of suspended algae.
 Reduce effects of wind on water
 Reduce transfer of gases and heat
between atmosphere and water.
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Heavy Metals
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Arsenic
Lead
Aluminum
Beryllium
Copper
Iron
Mercury
Nickel
These persist in soils and are toxic to animals even
in small quantities
Effects of Some Heavy Metals on
Human Health
Scope of Arsenic contaminaton
Scope of Nickle Contamination
Contaminant removal mechanisms
Physical
Sedimentation
Filtration
Adsorption
Volatilization
Chemical
Biological
Precipitation
Bacterial metabolism
Adsorption
Plant metabolism
Hydrolysis reaction Plant absorption
Oxidation reaction
Natural die-off
World Wide Projects on Bioremediation projects
Team
Year
Organism
Peking University
2010
E.coli
UT Dallas
2010
E.coli
METU Turkey
2010
E.coli
USeoul Korea
2010
E.coli
TU Delft
2010
E.coli
Michigan
2009
E.coli
UQ Australia
2009
E.coli
Cornell University
2009
B.subtilis
Description
Heavy metal
decontamination of
aquatic environments
via binding proteins
Establishing E.coli as a
biosensor for
environmental pollutants
using fluorescence
Designing a biosensor to
detect CO as a
dangerous pollutant
Using fluorescence
proteins to detect
various heavy metals in
water
Enabling hydrocarbon
degradation in aqueous
environments
Sensing and degrading
toluol
Uptake and reduction of
mercury in water
Creating a cadmium
sensor
Projects Working in Pakistan For
Bioremediation's
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Local Government and Rural Development Department
(LGRDD) and Anjum-e-Takmeel-e-Maqased-e Insania
(ATMI) (1996-1999)
Three of the above organizations contributed to introduce
various components of ISFS/Bio-remediation in GanguJuma
Village, Taxila.
The village reclaimed village wastewater was about 0.75 it
covered about 3.5 acre of land,the land consumed for
biological treatment of wastewater was about 0.75 acre and
rest of the land restored for integrated farming activities.
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ISFS/Bio-remediation Resource Centre Village GanguJuma,
Taxila UNICEF Pakistan and Sardar Ahmed Khan Memorial
Welfare Trust (SAK-MWT) (1999-2001).
Established Bio-remediation Garden to reclaim sewerage
water of NARC offices through bio-remediation.
Established Bio-remediation Orchard for treatment of 0.65
million gallons waste water of Shehzad Town, Islamabad.
Established integrated farming facilities through usage of
reclaimed water at Bio-remediation Garden and Bioremediation Orchard
Advantages
 Cost effective when compared to other more
conventional methods.
 “nature” method, more aesthetically pleasing.
 minimal land disturbance.
 reduces potential for transport of
contaminants by wind, reduces soil erosion
 hyperaccumulaters of contaminants mean a
much smaller volume of toxic waste.
 multiple contaminants can be removed with the
same plant.
Disadvantages
Slow rate and difficult to achieve acceptable
levels of decontamination.
 Potential phase transfer of contaminant.
 Possibility of contaminated plants entering
the food chain.
 Disposal of plant biomass could be a RCRA
regulated hazard substances.
 Possible spread of contaminant through
falling leaves.
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Disadvantages (cont.)
Decrease in action during winter months when
trees are dormant.
 Trees and plants require care.
 Contaminant might kill the tree.
 Degradation product could be worse than
original contaminant.
 Much testing is needed before a procedure
can be utilized (EPA approval)
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Conclusion
 Although much remains to be studied, phytoremediation
will clearly play some role in the stabilization and
remediation of many contaminated sites.
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The main factor driving the implementation of
phytoremediation projects are low costs with significant
improvements in site and the potential for ecosystem
restoration.
References
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S a m c h e r i a n , and M . M a r g a r i d a O l i v e i R A. 2013.
Transgenic Plants in Phytoremediation: Recent Advances and New
Possibilities. Environmental science & technology . Vol. 39, no. 24.
Martinoia, E., Grill, E., Tomasini, R., Kreuz, K., Amrehin, N. ATPdependent glutathione S-conjugate ‘export’ pump in the vacuolar
membrane of plants. Nature 1993, 364, 247-249.
Ross, S.M.Toxic Metals in Soil-Plant Systems; Wiley: Chichester, UK,
1994.
De la Fuente, J. M., Ramirez-Rodriguez, V., Cabrera-Ponce, J. L.,
Herrera-Estrella,L.Aluminiumtoleranceintransgenicplants by alteration
of citrate synthesis. Science 2010,276,1566-1568