C. Remediation of C. Remediation of groundwater contaminantsgroundwater contaminants

Physical, chemical, and biological Physical, chemical, and biological remediation methodsremediation methods

Objectives:Objectives:

Define Define remediationremediation and distinguish and distinguish among physical, chemical, and among physical, chemical, and biological remediation techniques biological remediation techniques ((bioremediationbioremediation).).

List, describe, and give examples of List, describe, and give examples of contaminated water remediation contaminated water remediation techniques.techniques.

RemediationRemediation of contaminants: of contaminants:

Definition Definition

– RemediationRemediation is the return of an area or is the return of an area or component to as natural a condition as component to as natural a condition as possible (e.g., contaminated water).possible (e.g., contaminated water).

Types of remediation:Types of remediation:

PhysicalPhysical treatment may include air treatment may include air striping, filtering of water, etc.striping, filtering of water, etc.

ChemicalChemical treatments include addition of treatments include addition of chemicals that facilitate physical or chemicals that facilitate physical or biological treatments, or oxidize biological treatments, or oxidize contaminants, etc.contaminants, etc.

BiologicalBiological treatment (bioremediation) treatment (bioremediation) utilizes complex biochemical pathways utilizes complex biochemical pathways of various organisms to degrade or of various organisms to degrade or detoxify contaminants.detoxify contaminants.

Techniques for remediation:Techniques for remediation: The method of remediation depends on The method of remediation depends on

the chemical nature of the contaminant:the chemical nature of the contaminant:– Pure-compound recoveryPure-compound recovery is possible when is possible when

groundwater is contaminated with a compound that is groundwater is contaminated with a compound that is not water soluble.not water soluble.

– Pump and Treat methodsPump and Treat methods typically involves typically involves pumping contaminated groundwater out and pumping contaminated groundwater out and treating with appropriate types of treatmenttreating with appropriate types of treatment• Air stripingAir striping• Chemical oxidation (using ozone, chlorine, etc)Chemical oxidation (using ozone, chlorine, etc)

– In-situ Remediation In-situ Remediation doesn’t involve removal doesn’t involve removal of the soil and groundwaterof the soil and groundwater

Pure-compound recovery:Pure-compound recovery:

Organic contaminants like oil and gasoline Organic contaminants like oil and gasoline are less soluble in water and can often be are less soluble in water and can often be pumped off the pumped off the surfacesurface of aquifers. of aquifers.

The specific gravity of the compound may The specific gravity of the compound may require pumping from the require pumping from the bottombottom of a of a confined aquifer (if > 1.0).confined aquifer (if > 1.0).

Sometimes, the product recovered is still Sometimes, the product recovered is still usable for its original function.usable for its original function.

Pump and Treat/In-Situ RemediationPump and Treat/In-Situ Remediation

Soil vapor extraction (SVE)Soil vapor extraction (SVE) removes organic removes organic contaminants (primarily from the unsaturated contaminants (primarily from the unsaturated zone) by flushing with air on site.zone) by flushing with air on site.

Air spargingAir sparging (in-situ aeration) uses circulated (in-situ aeration) uses circulated air to remove volatile contaminants (primarily air to remove volatile contaminants (primarily from the unsaturated zone) on sitefrom the unsaturated zone) on site

Bioventing also introduces air, but only to Bioventing also introduces air, but only to speed up natural aerobic microbial speed up natural aerobic microbial processess.processess.

Bioremediation techniques:Bioremediation techniques:

BioremediationBioremediation is the use of living organisms is the use of living organisms like bacteria, plants, animals, or fungi to like bacteria, plants, animals, or fungi to speed up the remediation process.speed up the remediation process.

A tremendous variety of microbes have been A tremendous variety of microbes have been used for remediation of contaminants.used for remediation of contaminants.

In-situ bioremediation introduces microbes In-situ bioremediation introduces microbes directlydirectly into the water which then degrade into the water which then degrade contaminants through biochemical contaminants through biochemical processes.processes.

Examples of bioremediation:Examples of bioremediation: Microbes have been used for centuries to Microbes have been used for centuries to

remediate wastewater (biol. treatment).remediate wastewater (biol. treatment). Microbes can also degrade and detoxify a Microbes can also degrade and detoxify a

wide variety of synthetic organic wide variety of synthetic organic compounds, metals, toxic elements, etc.compounds, metals, toxic elements, etc.

Microbes used to degrade contaminants Microbes used to degrade contaminants include bacteria, and fungi.include bacteria, and fungi.

Plants, animals, and mixed populations of Plants, animals, and mixed populations of different organisms can also be used .different organisms can also be used .

Advanced treatment techniques:Advanced treatment techniques: More advanced treatment techniques More advanced treatment techniques

may utilize may utilize combinationscombinations of remediation of remediation techniques.techniques.

Examples include injecting surfactants or Examples include injecting surfactants or chemicals underground to augment chemicals underground to augment conventional pump-and-treat techniques.conventional pump-and-treat techniques.

These are efforts to integrate in-situThese are efforts to integrate in-situ bio-bio-remediation with pump-and-treat remediation with pump-and-treat techniques.techniques.

Genetically-engineered Genetically-engineered microbes:microbes:

Attempts have been made to genetically Attempts have been made to genetically engineer microbes so that they degrade engineer microbes so that they degrade contaminants more efficiently and quickly.contaminants more efficiently and quickly.

Microbes have been patented for this purpose Microbes have been patented for this purpose (“superbug” to degrade oil spills).(“superbug” to degrade oil spills).

There is concern that these “unnatural” There is concern that these “unnatural” microbes may become pests in the microbes may become pests in the environment.environment.

Summary:Summary:

Remediation of water (or return to Remediation of water (or return to “natural” conditions by removal of “natural” conditions by removal of contaminants) may use physical, contaminants) may use physical, chemical, or biological techniques.chemical, or biological techniques.

Remediation techniques include pure-Remediation techniques include pure-compound recovery, air stripping, pump-compound recovery, air stripping, pump-and-treat techniques, bioremediation, and and-treat techniques, bioremediation, and combinations of these.combinations of these.