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Phytotechnologies for Environmental Restoration and Management. Micah Beard, M.S. Shaw Environmental, Inc. Phytoremediation. The use of plants to degrade, extract, contain, or immobilize contaminants in soil, sediment, groundwater, or surface water.
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Phytotechnologies for Environmental Restoration and Management Micah Beard, M.S. Shaw Environmental, Inc.
Phytoremediation The use of plants to degrade, extract, contain, or immobilize contaminants in soil, sediment, groundwater, or surface water. Phytotechnology Technical & Regulatory Guidance Document – Interstate Technology and Regulatory Cooperation
Phytovolatilization Phytotechnologies can be applied either in situ or ex situ and include: Degradation/ Detoxification Phytostabilization, erosion, and leachate control Constructed and Natural Wetlands for Treatment of Surface Water Phytoextraction: Heavy metal and radio nuclide accumulation Rhizodegradation & Rhizofiltration Chemical Phytostabilization Rhizodegradation, & Contaminant Uptake Hydraulic control: Plume containment
Source: ITRC, 2001 Phytostabilization • Stabilization of contaminated soils in place by vegetation, and immobilization (physically or chemically) of contaminants
Phytostabilization • Advantages • Reduction in erosion potential (wind, soil, runoff, leaching) • Low Cost / Less Disruptive • No removal or disposal • Drawbacks • Effects limited to immediate area of the plantings • Long term maintenance / monitoring
Source: ITRC, 2001 Rhizodegradation • The breakdown of contaminants in the soil through the bioactivity that exists in the rhizosphere • Bacteria, Yeasts, Fungi
Rhizodegradation • Advantages • Positive affects on soil microbe populations • Natural or created wetlands • Low Cost • Release to air less likely • Drawbacks • Effects can be limited to the immediate area of the plantings • Time • Long term maintenance / monitoring
Source: ITRC, 2001 Phytodegradation • Uptake of organic contaminants with the subsequent transformation in the plant’s roots, stems, and leaves.
Phytodegradation • Advantages • Contaminants removed from soil • No residuals management • Either metabolized or degraded • Low cost • Drawbacks • Difficult to separate from phytovolatilization • Possible toxic daughter products
Source: ITRC, 2001 Phytovolatilization • Translocation of dissolved contaminants into plant leaves followed by transpiration to the atmosphere.
Phytovolatilization • Advantages • Contaminants removed from soil • Transformed to less toxic products • No residuals management • Drawbacks • Moving problem from one media to another • Possible air monitoring
Source: ITRC, 2001 Phytoextraction • Translocation of soil contaminants to above ground stems and leaves.
Phytoextraction • Advantages • Contaminants removed from soil • Translocation to above ground plant parts allows harvesting • Reduced disposal costs • Drawbacks • Above ground plant residues must be managed • Must properly dispose
Source: ITRC, 2001 Rhizofiltration • Sorption, concentration, and/or precipitation of contaminants from surface waters or groundwater
Rhizofiltration • Advantages • Stream treatment can occur above ground • Not limited by site location • Drawbacks • Applicable to aqueous phase contamination • Requires engineered system (influent) • Requires monitoring • Must be properly disposed
Source: ITRC, 2001 Hydraulic Control • Uptake and consumption of groundwater in order to contain or control the migration of contaminants.
Hydraulic Control • Advantages • Extracted water is respired by plants • No treatment required • Drawbacks • Hydraulic control by plants is seasonal • Limited primarily to rooting zone • Time and space
Site Evaluation and Phytoremediation Design • Conduct typical site assessment • Develop conceptual phytoremediation design • Evaluate Phytoremediation design vs. traditional remedial alternatives • Costs • Bench scale or pilot scale evaluation of selected phytoremediation approach • Field implementation/planting • Monitoring and reporting
Technology Limitations • Root contact with contaminant- Plant roots must be able to extend to the depth of contaminant or contaminant must be moved to the root zone. • Growth rate of plants – Time (months to years) required for plants to reach maturity. • Contaminant concentration – Free product concentrations toxic to plants. • Unfavorable site conditions – Dense clays, salts, pH or dry conditions not conducive to plant growth. • Ecological risks – Plants may present new exposure pathway for humans and other local organisms
Technology Limitations -continued. • Space concerns – Is space or area available for design/implementation? • Waste production - If wastes are produced can they effectively be disposed? • Mechanism of contaminant remediation – will COC be accumulated within plant tissue or volatilized?
