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