Groundwater remediation
Groundwater remediation is the process that is used to treat
The many and diverse activities of humans produce innumerable waste materials and by-products. Historically, the disposal of such waste have not been subject to many regulatory controls. Consequently, waste materials have often been disposed of or stored on land surfaces where they percolate into the underlying groundwater. As a result, the contaminated groundwater is unsuitable for use.
Current practices can still impact groundwater, such as the over application of
Techniques
Ground water remediation techniques span biological, chemical, and physical
Biological treatment technologies
Bioaugmentation
If a treatability study shows no degradation (or an extended lab period before significant degradation is achieved) in contamination contained in the groundwater, then inoculation with strains known to be capable of degrading the contaminants may be helpful. This process increases the reactive enzyme concentration within the bioremediation system and subsequently may increase contaminant degradation rates over the nonaugmented rates, at least initially after inoculation.[2]
Bioventing
Bioventing is an on site remediation technology that uses
Biosparging
Biosparging is an
Bioslurping
Bioslurping combines elements of bioventing and vacuum-enhanced pumping of free-product that is lighter than water (light non-aqueous phase liquid or LNAPL) to recover free-product from the groundwater and soil, and to bioremediate soils. The bioslurper system uses a “slurp” tube that extends into the free-product layer. Much like a straw in a glass draws liquid, the pump draws liquid (including free-product) and soil gas up the tube in the same process stream. Pumping lifts LNAPLs, such as oil, off the top of the water table and from the capillary fringe (i.e., an area just above the saturated zone, where water is held in place by capillary forces). The LNAPL is brought to the surface, where it is separated from water and air. The biological processes in the term “bioslurping” refer to aerobic biological degradation of the hydrocarbons when air is introduced into the unsaturated zone contaminated soil.[5]
Phytoremediation
In the
Permeable reactive barriers
Certain types of
Chemical treatment technologies
Chemical precipitation
Ion exchange
Carbon adsorption
The most common activated carbon used for remediation is derived from bituminous coal. Activated carbon adsorbs volatile organic compounds from ground water; the compounds attach to the graphite-like surface of the activated carbon.[citation needed]
Chemical oxidation
In this process, called
Surfactant enhanced recovery
Surfactant enhanced recovery increases the mobility and solubility of the contaminants absorbed to the saturated soil matrix or present as
Permeable reactive barriers
Some permeable reactive barriers utilize chemical processes to achieve groundwater remediation.[citation needed]
Physical treatment technologies
Pump and treat
Pump and treat is one of the most widely used ground water remediation technologies. In this process ground water is pumped to the surface and is coupled with either biological or chemical treatments to remove the impurities.[citation needed]
Air sparging
Air sparging is the process of blowing air directly into the ground water. As the bubbles rise, the contaminants are removed from the groundwater by physical contact with the air (i.e., stripping) and are carried up into the unsaturated zone (i.e., soil). As the contaminants move into the soil, a soil vapor extraction system is usually used to remove vapors.[8]
Dual phase vacuum extraction
Dual-phase vacuum extraction (DPVE), also known as multi-phase extraction, is a technology that uses a high-vacuum system to remove both contaminated groundwater and soil vapor. In DPVE systems, a high-vacuum extraction well is installed with its screened section in the zone of contaminated soils and groundwater. Fluid/vapor extraction systems depress the water table and water flows faster to the extraction well. DPVE removes contaminants from above and below the water table. As the water table around the well is lowered from pumping, unsaturated soil is exposed. This area, called the capillary fringe, is often highly contaminated, as it holds undissolved chemicals, chemicals that are lighter than water, and vapors that have escaped from the dissolved groundwater below. Contaminants in the newly exposed zone can be removed by vapor extraction. Once above ground, the extracted vapors and liquid-phase organics and groundwater are separated and treated. Use of dual-phase vacuum extraction with these technologies can shorten the cleanup time at a site, because the capillary fringe is often the most contaminated area.[9]
Monitoring-well oil skimming
Monitoring-wells are often drilled for the purpose of collecting ground water samples for analysis. These wells, which are usually six inches or less in diameter, can also be used to remove hydrocarbons from the contaminant plume within a groundwater aquifer by using a belt-style oil skimmer. Belt oil skimmers, which are simple in design, are commonly used to remove oil and other floating hydrocarbon contaminants from industrial water systems.[citation needed]
A monitoring-well oil skimmer remediates various oils, ranging from light fuel oils such as petrol, light diesel or kerosene to heavy products such as No. 6 oil, creosote and coal tar. It consists of a continuously moving belt that runs on a pulley system driven by an electric motor. The belt material has a strong affinity for
Typically, belt skimmers remove very little water with the contaminant, so simple weir-type separators can be used to collect any remaining hydrocarbon liquid, which often makes the water suitable for its return to the aquifer. Because the small electric motor uses little electricity, it can be powered from
See also
- Toxic torts
- Brownfield
- CERCLA
- Groundwater pollution
- Plume (hydrodynamics)
- Groundwater remediation applications of nanotechnology
References
- ^ "Archived copy" (PDF). Archived from the original (PDF) on 2013-12-28. Retrieved 2014-08-09.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ a b Hayman, M, & Dupont, R. R. (2001). Groundwater and Soil Remediation: Process Design and Cost Estimating of Proven Technologies. Reston, Virginia: ASCE Press.
- ^ "Akaya FAQs". Akaya. Archived from the original on 2015-10-07. Retrieved 2015-09-14.
- ^ "Bioventing", The Center for Public Environmental Oversight (CPEO). Retrieved 2009-11-29.
- ^ "Bioslurping", The Center for Public Environmental Oversight (CPEO). Retrieved 2009-11-29.
- ^ Stewart, Robert. "Groundwater Remediation" Archived 2016-05-07 at the Wayback Machine, 2008-12-23. Retrieved on 2009-11-29.
- ^ "Surfactant Enhanced Recovery", The Center for Public Environmental Oversight (CPEO). Retrieved 2009-11-29.
- ^ "Air Sparging", The Center for Public Environmental Oversight (CPEO). Retrieved 2009-11-29.
- ^ "Dual Phase Extraction", The Center for Public Environmental Oversight (CPEO). Retrieved 2009-11-29.
- ^ "The Alternative To Pump And Treat" Bob Thibodeau, Water Online Magazine, December 27, 2006.
External links