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
Phytotechnologies can be applied either in situ or ex situ and include:
Phytostabilization, erosion, and leachate control
Degradation/ Detoxification
Phytovolatilization
Constructed and Natural Wetlands for Treatment of Surface Water
Phytoextraction: Heavy metal and radio nuclide accumulation
Rhizodegradation & Rhizofiltration
Rhizodegradation, & Contaminant Uptake
Hydraulic control: Plume containment
Chemical Phytostabilization
Phytostabilization Stabilization of contaminated soils in place by vegetation, and
immobilization (physically or chemically) of contaminants
Source: ITRC, 2001
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
Rhizodegradation The breakdown of contaminants in the soil through the
bioactivity that exists in the rhizosphere
Bacteria, Yeasts, Fungi
Source: ITRC, 2001
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
Phytodegradation Uptake of organic contaminants with the subsequent
transformation in the plant’s roots, stems, and leaves.
Source: ITRC, 2001
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
Phytovolatilization Translocation of dissolved contaminants into plant leaves
followed by transpiration to the atmosphere.
Source: ITRC, 2001
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
Phytoextraction
Translocation of soil contaminants to above ground stems and leaves.
Source: ITRC, 2001
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
Rhizofiltration Sorption, concentration, and/or precipitation of
contaminants from surface waters or groundwater
Source: ITRC, 2001
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
Hydraulic Control Uptake and consumption of groundwater in order to
contain or control the migration of contaminants.
Source: ITRC, 2001
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?
Elizabeth City, NC
Argonne East Site
BP Amoco Site – Sugar Creek, MO
Top Related