Air sparging, also known as ''in situ'' air stripping and ''in situ'' volatilization is an ''in situ'' remediation technique, used for the treatment of saturated

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

s and

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...

contaminated by

volatile organic compound Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...

s (VOCs) like

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

which is a widespread problem for the ground water and

soil health Soil health is a state of a soil meeting its range of ecosystem functions as appropriate to its environment. In more colloquial terms, the health of soil arises from favorable interactions of all soil components (living and non-living) that belong ...

. The vapor extraction has manifested itself into becoming very successful and practical when it comes to disposing of VOCs. It was used as a new development when it came to saturated zone remediation when using air sparging. Being that the act of it was to inject a hydrocarbon-free gaseous medium into the ground where contamination was found. When it comes to situ air sparging it became an intricate phase process that was proven to be successful in Europe since the 1980s. Currently, there have been further development into bettering the engineering design and process of air sparging.

Mechanism

Air sparging is a subsurface contaminant remediation technique that involves the injection of

pressurized air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and ...

into contaminated

ground water Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

causing hydrocarbons to change state from dissolved to

vapor In physics, a vapor (American English) or vapour (British English and Canadian English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critic ...

state. The air is then sent to the vacuum extraction systems to remove the contaminants. The extracted air or "off vapors" are treated to remove any toxic contaminants.

Methods and treatment

Soil vapor Extraction Soil vapor extraction (SVE) is a physical treatment process for in situ remediation of volatile contaminants in vadose zone (unsaturated) soils (EPA, 2012). SVE (also referred to as in situ soil venting or vacuum extraction) is based on mass tran ...

(SVE) involves the use of multiple air injection points and multiple soil vapor extraction points that can be installed in contaminated soils to extract vapor phase contaminants above the water table. Contamination must be at least 3 feet deep beneath the ground surface in order for the system to be effective. A blower is attached to wells, usually through a manifold, below the water table creating pressure. The pressurized air forms small bubbles that travel through the contamination in and above water column. The bubbles of air volatilize contaminants and carry them to the unsaturated soils above. Vacuum points are installed in the unsaturated soils above the saturated zone. The vacuum points extract the vapors through to a Soil Vapor Extraction system. In order for the vacuum to avoid pulling the air from the surface, the ground has to be covered with a tarp or other method of sealing out surface air. Surface air intrusion into the system reduces efficiency and can reduce the accuracy of system metrics. The tarp is used to stop vapors from breakthrough to the surface above. The air sparging system treats the off-gases (referred as contaminated vapors and extracted air). The vapor is treated with granulated activated carbon prior to release to the atmosphere. For example, arsenic-contaminated groundwater were treated by air sparging and what the treatment does is remove arsenic at certain percentage using solution of iron and arsenic only at a molar ratio of 2. Treatment using air sparging is beneficial as groundwater contains high amounts of dissolved iron, which contains the theoretical capacity for the treatment.

Applicability

Air sparging is generally applied for commercial usage. Air sparging contaminant groups are VOCs and fuels found in groundwater. Air sparging is usually applied to the lighter gasoline constituents such as benzene, ethylbenzene, toluene, and xylene. This method is typically not applied on the heavier gasoline products such as kerosene and diesel fuels. The usage of air sparging is commonly applied when cleaning up contaminated water under buildings and obstacles to prevent the further contamination of that water source. The usage of air sparging and SVE is safe when properly conducted. This makes sure only clean air that meets a certain quality standard is released, therefore it does not pose a threat when the proper sample method is done to make sure that hazardous gases do not exit into the atmosphere.EPA,OSWER,OSRTI, US. "A Citizen's Guide to Soil Vapor Extraction and Air Sparging , US EPA". EPA United States. Environmental Protection Agency.

Mechanism

Methods and treatment

Applicability

References

Further reading