SITE REMEDIATION

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SITE REMEDIATION

• Pedro A. García Encina
• Department of Chemical Engineering
• University of Valladolid

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CONTAMINATED SITES

• In the past much wastes were dumped
  indiscriminately or disposed of in inadequate
  facilities. These problems went ignored as did
  spills of product or leaks from tanks.
• Theses practices contaminated sites with
  hazardous substances that pose a threat to human
  populations.

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HAZARDOUS WASTE - Characteristics
Corrosivity - waste that is highly acidic or
alkaline, with pH lt2 or pH gt12.5. Ignitability
- waste that is easily ignited. Reactivity
- waste that is capable of sudden, harmful
reaction or explosion. Toxicity - waste capable
of releasing specified, toxic substances to water
in significant concentrations.
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HAZARDOUS WASTE - Major Categories
Inorganic Aqueous Waste - liquid waste composed
of acids, alkalis or heavy metals in
water. Organic Aqueous Waste - mixtures of
hazardous organic substances (pesticides,
petrochemicals) and water. Oils - liquid waste
composed primarily of petroleum derived oils
(lubrication oils, cutting fluids). Inorganic
Sludges/Solids - sludges, dusts, solids,
non-liquid wastes containing hazardous inorganic
substances (metal fabricating wastes). Organic
Sludges/Solids - tars, sludges, solids and other
non-liquid wastes containing organic hazardous
substances (contaminated soils).
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Toxicity Characteristics of Hazardous Wastes
Acute Toxicity - results in harmful effects
shortly after a single exposure, such as cyanide
poisoning. Chronic Toxicity - may take up to many
years to result in toxic effects, such as cancer
or long-term illness.
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HAZARDOUS WASTE TREATMENT

• Source Reduction
• Recycling
• Treatment
• Disposal

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POLLUTANT REDUCTION TECHNIQUES
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WASTE MINIMIZATION-PREVENTING TOMORROWS
REMEDIATION PROBLEMS

• Many of todays contaminated sites are the result
  of accepted lawful waste-disposal practices of
  years ago

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SITE REMEDIATION

• Source Reduction (?)
• Recycling (difficult)
• Treatment
• Disposal

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SITE REMEDIATION

• METHODOLOGY
• SITE CHARACTERIZATION
• REMEDIAL ALTERNATIVES ANALYSIS
• DESIGN, CONSTRUCT AND OPERATE

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SITE CHARACTERIZATION - Definition
Site Characterization is defined as the
qualitative and quantitative description of the
conditions on and beneath the site which are
pertinent to hazardous waste management.
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SITE CHARACTERIZATION - Goals
The goals of site characterization are
to 1. Determine the extent and magnitude of
contamination 2. Identify contaminant transport
pathways and receptors 3. Determine risk of
exposure
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Zones of Contamination
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Identification of Receptors and Pathways
receptors
storage tank
residual gasoline
gasoline vapors
Domestic well
groundwater table
floating gasoline
groundwater flow
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EXPOSURE PATHWAYS
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METHODS OF SITE CHARACTERIZATION

• Remote Methods
• Seismic Survey
• Soil Resistivity
• Ground Penetrating Radar
• Magnetometer Survey

• Direct Methods
• Auger Drilling
• Rotary Drilling
• Soil Excavation

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REMOTE SUBSURFACE CHARACTERIZATION
Seismic Survey
Shock wave propagates faster through rock than
soil, depth to rock and rock type can be
determined.
Geologic Wave Material Velocity (m/s) Dry
sand 500-900 Wet sand 600-1800 Clay 900-2800 Wate
r 1400-1700 Sandstone 1800-4000 Limestone 2100-61
00 Granite 4600-5800
Source
Geophones
Seismic wave
Soil
Rock
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REMOTE SUBSURFACE CHARACTERIZATION
Soil Resistivity
Soil/rock type can be determined by soil
resistivity.
Rsoil resistivity(ohm-m) selectrode spacing
(m) Vmeasured voltage (volts) Iapplied current
(amperes)
Current Meter
Battery
Voltage Meter
s
Current flow lines
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DIRECT SUBSURFACE CHARACTERIZATION
Auger Drilling

• Useful in unconsolidated geologic materials.
• Sample collection easy, intact samples can be
  collected with hollow-stem auger.
• Cannot be used where significant consolidated
  rock is present.
• Does not alter subsurface geo-chemistry.

Rod inside hollow stem for removing plug
Flight
Removable Plug
Drill Bit
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DIRECT SUBSURFACE CHARACTERIZATION
Rotary Drilling

• Useful in consolidated geologic materials, can
  drill through rock.
• Subsurface samples contaminated with drilling
  mud.
• Air-rotary may blow volatile contaminants into
  surrounding subsurface structures (basements).
• Mud-rotary alters subsurface chemistry.

mud pump
mud pit
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DIRECT SUBSURFACE CHARACTERIZATION
Drilling through confining layers may allow the
spread of contamination from one hydrologic unit
to another.
monitoring well
leaking tank
soil
contaminated ground water
confining layer (clay)
uncontaminated water
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DIRECT SUBSURFACE CHARACTERIZATION
Soil Excavation
Advantages
Disadvantages

• No specialized equipment, typically uses backhoe.
• Subsurface samples can be collected directly.
• Inexpensive.
• Good source removal mechanism.

• Useful only in unconsolidated geologic materials
  to a maximum depth of 10 meters.
• Large surface disturbance.
• Excavation not useful for long term groundwater
  monitoring.

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SOIL CHARACTERIZATION
Soil Contaminant Sampling

• Performed during drilling or excavation.
• Collection of samples from several depths within
  the soil profile.
• Where volatile compounds are present, sampling
  should be done in air-tight glass containers. No
  headspace should be left in the containers.
• Samples should be chilled for transportation to
  the laboratory.

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GROUNDWATER CHARACTERIZATION
Extent of Contamination
Successive wells should be drilled until the
extent of the groundwater contaminant plume is
defined.
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AIRBORNE CONTAMINATION
Source Waste pile Release Mechanism Volatilizat
ion Transport Medium Air Exposure
Mechanism Inhalation or skin contact Exposure
Point May be distant from source, depends on
concentration and wind speed
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AIRBORNE CONTAMINATION
Measurement Techniques
Laboratory Analysis Samples can be collected in
the field in an air-tight bag (Tedlar ) and
sampled in the laboratory. Field Analysis
Samples can be analyzed in the field via handheld
instrumentation such as a photo-ionization
detector for volatile organic compounds or a
draw-tube collection device (such as a Drager
tube).
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AIRBORNE CONTAMINATION
Reducing Airborne Hazards

• Airborne Hazards Reduction can be accomplished
  through
• Source removal
• Covering the source (prevents volatilization)
• Dilution with clean air (if indoors)

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ASSESSING EXPOSURE RISK
Definition Assessment of exposure risk seeks to
determine the probability that contamination will
migrate to a receptor (human or animal) and be
ingested (eaten, inhaled, or absorbed by the
skin).
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EXPOSURE PATHWAYS
2
3
4
1
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EXPOSURE PATHWAYS
2
Contaminated groundwater exposure from drinking
or from breathing contaminated vapors liberated
during bathing
3
4
1
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EXPOSURE PATHWAYS
2
3
4
Inhalation of airborne contaminants volatilized
from the source and carried by wind.
1
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EXPOSURE PATHWAYS
2
3
4
Direct contact with contaminated soil exposure
from skin contact with contaminants in soil.
1
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EXPOSURE PATHWAYS
2
3
4
Indirect contact exposure to contaminant from
crops or animals which have accumulated
contamination from soil or groundwater
1
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SITE REMEDIATION

• METHODOLOGY
• SITE CHARACTERIZATION
• REMEDIAL ALTERNATIVES ANALYSIS
• DESIGN, CONSTRUCT AND OPERATE

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DEVELOPMENT OF ALTERNATIVES

• Identify general response to actions for each
  objective
• Characterise media to be remediated
• Identify potential technologies
• Screen the potential technologies
• Assemble the screened technologies into
  alternatives

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ALTERNATIVE SELECTION

• 1. Long term effectiveness
• 2. Long term reliability
• 3. Implementability
• 4. Short term effectiveness
• 5. Cost

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ALTERNATIVE SELECTION

• 1. Long term effectiveness
• 2. Long term reliability
• 3. Implementability
• 4. Short term effectiveness
• 5. Cost

• Qualitative assessment of how well an
  alternative meets the remedial action objective
  over the long term
• To calculate by means of a complete analysis the
  residual risk (Risk represented by untreated
  contaminants or residuals remaining at the site)

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ALTERNATIVE SELECTION

• 1. Long term effectiveness
• 2. Long term reliability
• 3. Implementability
• 4. Short term effectiveness
• 5. Cost

• Is only a issue with the alternatives that leave
  untreated contaminants or treatment residuals at
  site at the conclusion of the implementation
  period
• One tradeoff that require careful consideration
  at most sites is whether to treat or to contain

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ALTERNATIVE SELECTION

• 1. Long term effectiveness
• 2. Long term reliability
• 3. Implementability Function of
• 4. Short term effectiveness
• 5. Cost

• History of the demonstrated performance of a
  technology
• Ability to construct and operate it given the
  existing conditions at the particular site
• Ability to obtain the necessary permits from
  regulatory agencies

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ALTERNATIVE SELECTION

• 1. Long term effectiveness
• 2. Long term reliability
• 3. Implementability
• 4. Short term effectiveness
• 5. Cost

• Deals primarily with the effects on human health
  an the environment of the remediation itself
  during its implementation phase
• Health and environmental risk
• Worker safety
• Implementation time

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ALTERNATIVE SELECTION

• 1. Long term effectiveness
• 2. Long term reliability
• 3. Implementability
• 4. Short term effectiveness
• 5. Cost

• The weight given to the cost when evaluating
  alternatives depend upon the particular guidance
  of the agency
• Capital costs (the cost to construct the remedy)
• Operating and maintenance cost (O M)
  (post-construction expenditures)

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TREATMENT ALTERNATIVES

• On site
• In situ
• Ex situ (Excavation)
• Off site (Excavation Transportation)

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HAZARDOUS WASTE TREATMENT METHODS
Physical/Chemical Methods Mass transfer and
chemical transformation processes resulting in
the removal or remediation of contamination by
abiotic, not combustion means. Biological
Methods Transformation or binding of
contaminants by microorganisms, principally
bacteria. Waste Stabilization Containment of
wastes such that they pose no further threat to
receptors. Combustion Methods Transformation of
organic wastes by burning.
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SOIL VAPOR EXTRACTION
Description - soil vapor extraction (SVE) uses a
vacuum applied to soil to remove volatile organic
compounds (VOCs) from the unsaturated zone. Uses
- effective for contaminants with high vapor
pressure, such as gasoline compounds, chlorinated
solvents. Advantages - low cost, simple design
and operation, efficient removal of VOCs from
unsaturated zone. Disadvantages - not effective
for non-volatile compounds, not effective in low
permeability soils or where groundwater is close
to the surface, may need to treat off-gas in
another process, does not address groundwater
contamination.
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SOIL VAPOR EXTRACTION
Vapor Extraction Pump
contaminated soil
air movement through contaminated soil
Water Table
Contaminated Groundwater
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AIR STRIPPING
Description - enhances volatilization of
dissolved contaminants from water. Can be used
for treatment of either process wastewater or
groundwater pumped to the surface. Uses - remove
volatile organic compounds (VOCs) from
water. Advantages - simple operation, efficient
removal of low concentrations of
VOCs. Disadvantages - high capital cost, design
intensive, may need to treat off-gas in another
process.
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Packed Column Air Stripper
Water Inlet (contaminated)
Air Outlet (contaminated)
Types of Packing Materials
Raschig ring
Pall ring
Berl saddle
Intalox saddle
Tri-pack
Packing Material
Water Outlet (clean)
Air Inlet (clean)
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Packed Column Air Stripper
Typical Air-Stripping Column Specifications Diam
eter 0.5 - 3 meters Height 1 - 15
meters Air/Water ratio 5-200 Pressure drop 200
- 400 N/m2
Stripping Column Off-gas Treatment System
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CARBON ADSORPTION
Description - carbon adsorption uses granular
activated carbon (GAC) to remove organic
contaminants from a water or vapor stream.
Contaminated air/water is pumped through the GAC
unit and contaminants adsorb onto carbon
particles by electrostatic forces. Uses -
effective for a wide range of organic
contaminants. Is commonly used both for process
waste treatment and for hazardous waste
remediation. Advantages - easy to install, can
completely remove many organics, can treat either
water or vapor stream. Disadvantages - high
operating expense, carbon must be changed
periodically, contaminants are not mineralized.
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SOIL WASHING OR FLUSHING

• Description - Excavated soil is flushed with
  water or other solvent to leach out
  contamination. Based on the principles of
  solid-liquid extraction
• Uses - remove organic wastes and certain
  (soluble) inorganic wastes
• Advantages - simple operation, efficient removal
  of organic contaminants (VOC, semi VOC and
  halogenated organics) . For metal, it has been
  successful at extracting organically bound metals
  (tetraethyl lead)
• Disadvantages - Longer washing times and
  soil-handling problems with lower-permeability
  clays and clay-like soils

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SCHEMATIC FLOWSHEET OF A SOIL WASHING SYSTEM
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CHEMICAL OXIDATION
Description - organic chemicals in extracted
groundwater or industrial process wastewater are
transformed into less harmful compounds through
oxidation by ozone (O3), hydrogen peroxide
(H2O2), chlorine (Cl2) or ultraviolet radiation
(UV). UV is often used in combination with ozone
or hydrogen peroxide. Uses - effective for a wide
range of organic contaminants such as VOCs,
mercaptians, and phenols. Can also be used for
some inorganics, such as cyanide. Process is
non-specific, oxidant will react with any
reducing agent present in the waste, such as
naturally occurring organic matter. Advantages -
effective, reliable treatment for waste streams
which contain a variety of contaminants, often
used for drinking water purification.
Disadvantages - high operating expense,
incomplete oxidation may create chlorinated
organic molecules (if Cl2 is used), generation of
oxidizing agent typically cannot vary with
fluctuating contaminant concentrations.
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CHEMICAL OXIDATION Reactor Configuration
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CHEMICAL OXIDATION - Results
Initial TCE 58 mg/L
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CHEMICAL OXIDATION - Results
Halogenated aliphatic destruction by H2O2 and UV
at 20oC.
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CHEMICAL OXIDATION - Design Considerations
Thermodynamics Free energy available from
reactions Oxidant Free Energy (E,
volts) O3 2.07 H2O2 1.78 Cl2 1.36
Kinetics Reaction must proceed to necessary
completion within the residence time in the
reactor vessel. Combination of UV with ozone or
hydrogen peroxide increases reaction kinetics .
Design Steps 1) Will oxidation reaction proceed
with contaminants present? 2) What is the contact
time necessary between the oxidant and the
contaminants present?
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SUPERCRITICAL FLUID EXTRACTION
Description - contaminated liquid or solid is
placed in a reactor vessel with the extraction
fluid, which is heated and pressurised to the
critical point (see chart). In treatment of
hazardous wastes, fluids most commonly used are
water and CO2, some organic solvents may also be
used. Uses - supercritical fluid extraction can
be used to treat contaminated soils, sediments,
sludges, solids or liquids. Advantages -
effective treatment for process wastes or
extracted soil or groundwater which is either
highly contaminated with organic compounds or
with very recalcitrant (hard to treat) organics
Disadvantages - expensive, solids must be
reduced in size to 100 um to pass through high
pressure pumps.
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SUPERCRITICAL FLUID EXTRACTION Reactor
Configuration
Schematic diagram of reactor for the extraction
of organic compounds from water, CO2 is the
extraction fluid.
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SUPERCRITICAL FLUID EXTRACTION Solvent Selection
Criteria
Cost - water, CO2 are least expensive Recoverabili
ty - solvent must be recoverable for process to
be economical Hazard in use - SFE involves high
temperatures and pressures which reactor vessels
must be built to withstand Critical temperature
and pressure - the higher the critical T and P of
the solvent, the greater the operating
expense Distribution coefficient - determines the
solvent/ contaminant ratio which can be used.
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MEMBRANE PROCESSES
Electrodialysis - separation of ionic species
from water by direct-current electric field.
Useful for removal of charged ions and metals
from water. Reverse Osmosis - solvent is forced
through a semi-permeable membrane by the
application of pressures in excess of the osmotic
pressure. Useful for removal of metals and some
organics. Ultrafiltration - separates dissolved
contaminants on the basis of molecular size.
Lower limit for molecular weight is approximately
500.
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BIOLOGICAL PROCESSES
Description - biodegradation uses micro-organisms
(bacteria) to remove organic contaminants from
vapors, liquids or solids. Most organic
contaminants are utilized by bacteria as both a
carbon and energy source. Uses - biological
processes are effective on both process waste
streams and remediation of soil and groundwater.
Biodegradation systems for soil and groundwater
can by designed either in-situ (in place) or
ex-situ (removed from the ground). Advantages -
low cost, low site disturbance, effective for
many organic contaminants. Disadvantages - long
clean-up times, not effective for inorganic
contaminants, specialized conditions necessary
for chlorinated solvent degradation.
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BIOLOGICAL PROCESSES

• Necessary Constituents
• microorganisms capable of degrading contaminants
• contaminants in aqueous (water) phase
• available electron acceptor present

Aerobic Degradation takes place in the presence
of molecular oxygen (O2), the most energetically
favorable electron acceptor. Anaerobic
Degradation when O2 is not available, other
compounds can act as electron acceptors for
biodegradation processes, such as NO3, Fe3,
Mn4, SO4, and CO2.
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Energy Available from Electron Acceptor Processes
Electron
Toluene
Benzene
Acceptor
O
-3566
2
-
NO
-3245
3
4
, Mn

-2343

SO-2
-340
4
CO
-136
2
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BIOLOGICAL PROCESSES - Remediation of soil and
groundwater
In-situ biodegradation Natural
attenuation Engineered systems Ex-situ
biodegradation Pump and treat systems for
groundwater Landfarming systems for soil
treatment
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In-Situ Biodegradation - Natural Attenuation
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Natural Attenuation of Contaminants
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Relative Importance of Electron Acceptor
Processes at 25 Air Force Sites
Aerobic
Methanogenesis
Respiration
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10
Denitrification
14
Iron (III)
Reduction
8
Sulfate
Reduction
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Source Wiedemeier et al., 1995
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Stoichiometric Conversion Example Iron Reduction
BTEX 36Fe3 21H2O 36Fe2 7CO2
7H2O
Assume 20 mg/l Fe2 observed in aquifer
Calculate BTEX consumed per unit volume
0.9 mg/l BTEX consumed in aquifer
Calculate groundwater flux and total BTEX
consumed
Flux vwh 1000 ft3/d 7500 gal/d 28x103 l/d
Assume Vgw 1 ft/day Plume width 100
Plume height 10
BTEX consumed (28x103 l/d) (0.9 mg/l) 25
g BTEX/day
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In-Situ Biodegradation - Engineered Systems
Air-sparging/nutrient addition system
Groundwater treatment unit
air compressor
water/nutrient supply tank
injection well
water table
contaminated soil
air sparger
pump
confining layer
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In-Situ Biodegradation - Engineered Systems
Infiltration gallery, recirculating system
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In-Situ Biodegradation - Engineered Systems
Combination air injection/extraction system
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In-Situ Biodegradation - Engineered Systems Air
injection bioventing
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Ex-Situ Biodegradation - Pump and treat
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Ex-Situ Biodegradation - Biofiltration
Moisture Addition
Biofilter
Blower
Vapor Extraction Well
Biofilter is colonized with bacteria capable of
degrading contaminants. Media can be soil, peat,
compost, or manufactured packing material.
Contaminated Soil
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Ex-Situ Biodegradation - Biopiles
Gas Monitoring Probes
Air Intakes
Irrigation Piping
Wood Chips
Weights
Tarp
Aeration Pipes
Crushed Stone
Soil
Curb
Contaminated Soil
Impermeable Base
Leachate Pipe
Aeration Pipe
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Ex-Situ Biodegradation - Landfarming

• Procedures
• Excavated soils are spread onto the ground
  surface to a depth of less than 0.5 meters.
• Underlying soils should be low permeability, or a
  clay liner or impermeable membrane should be used
  to prevent contaminant migration to groundwater.
• Landfarmed soils should be tilled every 2-3
  months and kept moist.

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WASTE STABILIZATION AND CONTAINMENT

• Procedure Excavated soils or process wastes are
  secured such that contaminant migration will not
  occur (containment), or are mixed with binding
  agents that solidify the waste and prevent
  leaching or release of the contaminants
  (stabilization).
• Processes
• Encapsulation
• Sorption processes
• Polymer stabilization
• In-situ vitrification

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COMBUSTION METHODS
Description waste combustion can take place in
hazardous waste incinerators, cement kilns, or
industrial boilers. Most significant design
parameter is the heat value of the waste. Many
concentrated organic wastes will support
combustion without supplemental fuel. Applicable
wastes all organic wastes can be mineralized
using combustion methods. Metals are oxidized in
the combustion process and are either vented in
gaseous form or are concentrated in ash. Metals
prone to gaseous emission are arsenic, antimony,
cadmium, and mercury. Procedure Wastes are
graded for suitability for combustion. Waste
analysis also indicates the proper fuel/air
mixture for complete combustion.
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CONTAINMENT

• Frecuently it is necessary to minimize the rate
  of off site contaminant migration employing
  containments technologies to minimize risk to
  public health and environment.
• Containment technologies may be associated with
  other technologies to implement a long-term
  clean-up strategy for the site

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CONTAINMENT

• Active system components require considerable
  effort and on-going energy in put to operate (For
  example pumping wells)
• Pasive system components work without much
  attention, except maintenance (such a cover)

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BARRIER
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BARRIER
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SELECTION OF REMEDIAL ALTERNATIVES
1. Data Needs A. Site Characterization B. Regu
latory Disposition C. Risk Assessment 2.
Establishment of Site Objectives A. Clean-up
Level Necessary B. Long-term Liability C. Costs
3. Development and Analysis of
Alternatives A. Development of Possible
Alternatives B. Analysis of Alternatives for
Effectiveness 4. Remedial Option Selection,
Implementation, and Monitoring A. Remedial
Option Selection B. Implementation C. Long term
Site Monitoring
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SELECTION OF REMEDIAL ALTERNATIVES

• Data Needs
• Understand extent and magnitude of contamination.
  A thorough site characterization is necessary.
  Chemical fate and transport must be understood.
• Determine risk to potential receptors. This is
  necessary to correctly focus efforts where they
  are most needed. Typical exposure pathways
  include groundwater wells and airborne
  contaminants.
• Determine what limits or requirements are placed
  on the clean up by government regulations. It is
  important to insure that all participants
  understand and agree on the goal of the remedial
  effort.

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SELECTION OF REMEDIAL ALTERNATIVES

• Establishment of Site Objectives
• Establishment or negotiation of acceptable
  clean-up goals is necessary prior to selection of
  a remedial process.
• The extent of long-term liability for the site
  should be considered.
• Costs of each remedial option must be considered
  along with the financial means of the financially
  responsible party. Options for cost assistance
  should be considered at this stage (national and
  international).

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SELECTION OF REMEDIAL ALTERNATIVES

• Development and Analysis of Alternatives
• A list of potential remedial alternatives is
  compiled for further study based on their
  feasibility to clean up the site.
• Criteria for selection of a remedial alternative
  are effectiveness, reliability, cost, time to
  implementation, and time to clean up.
• Before a remedial solution is chosen, a detailed
  plan of implementation should be formulated to
  insure that the technique is capable of
  remediating the site to the goals prescribed.

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SELECTION OF REMEDIAL ALTERNATIVES

• Remedial Option Implementation and Monitoring
• After a remedial option is selected, construction
  contracts and engineering designs must be
  completed. Can be done by employee engineers or
  contractor engineers (must be familiar with
  technology chosen).
• Long term site monitoring should continue to
  insure that the solution is working, and that
  further contaminant migration does not occur.
  Monitoring should include all applicable media
  (groundwater, soil vapor, and air).

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CONTAMINATED SITES IN SPAIN
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ACTIONS TO BE CARRIED OUT IN SPAIN
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LEY 10/98 DE RESIDUOS

• CONTAMINATED SITES
• Depends of Comunidades Autónomas
• List of contaminated places (priority to
  clean-up)
• Need to clean-up the site
• The responsible of the contamination
• The owner of the site

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REGIONAL PLANS
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CONTAMINATED SITE (BOECILLO)
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CONTAMINATED SITE (BOECILLO)
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CONTAMINATED SITE (BOECILLO)