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Contents Phytoremediation Plants used for Phytoremediation's How does it work? Mechanisms Phytotransformation/Phytod egradation Phytoextraction Phytostabilization Rhizofiltration Rhizosphere Bioremediation 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 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 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. 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 Pollutant is taken up by the plant and transformed in plant tissue (to be effective must be transformed to a less toxic form). Trichloroethylene (TCE), a prevalent ground water contaminant, transformed to less toxic metabolites by using hybrid poplar tree. 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 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 wind-blown minimizing dust, soil erosion, 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. 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. Rhizofiltration (cont.) 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). Rhizofiltration (cont.) 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 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. 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. 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 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 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. Function of plants in aquatic treatment Plant Parts Roots and/or stem in water column 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 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. Heavy Metals 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 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. 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. 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) Conclusion Although much remains to be studied, phytoremediation will clearly play some role in the stabilization and remediation of many contaminated sites. The main factor driving the implementation of phytoremediation projects are low costs with significant improvements in site and the potential for ecosystem restoration. References 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
