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Soil Remediation :earth_africa: (Sources (Pesticides, Herbicides,…
Soil Remediation
:earth_africa:
Contaminants
Oils and tars
Heavy metal
Impacts from water and air
Organic compounds
tetrachloroethylene (PCE)
Soluble salts
Landfill leachates
Explosives
Sources
Pesticides
Herbicides
Fungicides
Industrial waste
Household waste
Landfill
Agricultural waste
Atmospheric deposition
Natural
Purification Methods
Physical Methods
Soil Vapor Extraction
Method
Use vacuum to remove contaminant
Technology
Motor and blower
Advantages
Low cost/maintenance
less disruption to business operation
Disadvantages
only in coarse grained soil (sand/gravel)
Only soil above water table
Only for volatile contaminants
Can damage soil properties
Excavation :construction:
Method
Using excavator to remove contaminated soil to treatment landfill
Advantages
Quick
for any chemical pill
Low cost for shallow contaminant
Disadvantages
Higher cost with deep soil
Unfriendly at business operation
Heavy machine required
Electrical Resistance Heating :zap:
Technology
The electrodes can be installed angled
Method
Use electricity to heat up contaminants
Contaminant collected by extraction wells nearby
Advantages
Used in most soil
Used at any depth
less disruption to business operation
Can be place above or under groundwater table
Disadvantages
Specific equipment required
Technical expertise required
Only for volatile contaminants
Can damage soil properties
Other thermal treatments :hotsprings:
Types
Treat petroleum hydrocarbon compound
Thermal desorption
Volatile contaminants carried away by a sweep gas or vacuum and eventually destroyed via incineration or carbon adsorption
Ex situ TD
In situ TD
Smoldering
In situ smoldering utilizes a self-sustaining smoldering wave to destroy hydrocarbons without excavation.
Use for heavy hydrocarbon in coal, tar sand due to high temperature
Incineration
total destruction of contaminants through high-temperature combustion
Pyrolysis
heating of impacted soils in anoxic atmospheres
Treat heavy crude oils, petroleum sludges, tars, PAHs, and refined fuels and fuel oils
Vitrification
Using very high temperatures (1600–2000 °C) to melt and fuse contaminants and soil into a glass-like solid
Treats radioactive wastes
Radio frequency heating/microwave heating
To enhance other processes, volatilize and desorb low molecular weight hydrocarbons, decrease viscosity, improve bio-availability, and speeds microbial degradation rates
Hot air injection
increase contaminant mobility and extraction efficiency in soil vapor extraction
Steam injection
lowering contaminant viscosity, increasing mobility, or warming cold soils to improve bio-degradation rates, enhance oil recovery
Advantages
Fast
remove up to 99% contaminant
Disadvantages
Destroy soil properties (minerals, organic matter)
Huge energy required
High cost
Affect the ecosystem and re-greening effort
Chemical Methods :oil_drum:
Chemical Oxidation :droplet:
Technology
Use K2S2O8 to destroy PCE
Method
Use specific chemical to destroy contaminant
Disadvantages
Only in shallow mix soil (not clay)
Heavy machine required for mixing
Depth is limited
Advantages
Treat lots of contaminants
Fast
Soil washing
Method
Leaching of heavy metals from soil matrix with various reagents and extractants
Advantages
Permanently remove heavy metal
Fast
Disadvantages
High cost
Soil structure deterioration
Chemical
stabilization
Method
decrease the mobility, bioavailability and bioaccessibility of heavy metals
Advantages
Fast
Simple
Low cost
Disadvantages
Only change the physicochemical properties
Cannot remove all metal
Amendments: cement, clay, zeolites, phosphates, minerals, microbes and organic amendments, containing cellulose and lignin
Encapsulation
Method
Encapsulating hazardous material in manageable
solid blocks by mixing with concrete, lime or asphalt
Surface capping
Method
Cover the contaminated site with a layer
of waterproof material to form a stable, protection surface
Advantages
For highly-contaminated
Disadvantages
Small area
Biological treatments :deciduous_tree:
Bioventing
Method
Increasing the indigenous microbial (microorganisms) activity by injection of air into the vadose zone of the soil
Advantages
Target to petroleum contaminant
Toluene
Benzene
Phenol
Other organic compounds
Acetone
Easily-found equipment
Easy to install
Low cost
No disturbance
Disadvantages
Not for heavy clay soil
Not for high-concentration contaminant
Phytoremediation
Method
Using plants to extract, degrade, contain, or immobilize contaminants
5 sub-processes
phytoextraction
Contaminant is uptake by plan root and stored in plant tissues
phytodegradation
Use enzyme to break down contaminant
phytostabilization
Contaminant absorbed to roots to limit its migration
Prevent water erosion, leaching and soil dispersion of pollutant
rhizodegradation
microbial degradation within rhizosphere
plant creates environment for microcosm to destroy contaminants
phytovolatilization
Contaminant is uptake and transformed to volatile form
Advantages
Treat many contaminant types
chlorinated solvents
pesticides
Petroleum hydrocarbons
explosives
heavy metals
landfill leachates
Cost less
Target deep contamination
Disadvantages
slow process
climate dependency
Plant capacity to uptake
Institutional Controls
Avoid contaminant contact with human by physical barrier
Fast and cheap
Knowledge and regulation required
Not treat all type of contaminant
Classifications
Objectives
Removal/destruction of contamination
Modify contamination to less toxic/mobile/reactive form
Interrupting the pathway of exposure by isolation
Methods
Engineering approaches
Excavation and remove to landfill for further remediation
Process-based techniques
Biological
Physical
Chemical
Thermal
Stabilization
Positions
On-site (in-situ)
Treat the contaminant right above the soil or nearby
Off-site (ex-situ)
To remove the soil to landfill for other treatment
Landfill and modern landfill
landfill
Method
Use a large protected area to compact and bury the non-recyclable waste
Advantages
Methane released for energy
Low cost
Dispose wide range of material
Disadvantages
Large area/space required
Leaches affects water ground
Long-term
Quality control is not ensured
Technology
References
Thermal Treatment of Hydrocarbon-Impacted Soils (
https://www.sciencedirect.com/science/article/pii/S2095809917300796
)
Remediation methods for contaminated sites (
https://optima.discendum.com/learning/id652/bin/doc_show?id=1206156
)
An overview of field-scale studies on remediation of soil contaminated
with heavy metals and metalloids (
https://optima.discendum.com/learning/id652/bin/doc_show?id=1206158
)
A comparison of technologies for remediation of heavy metal contaminated soils (
https://optima.discendum.com/learning/id652/bin/doc_show?id=1206157
)
