中国色图Air Sparging Technology and the Equipment Needed
Joshua Beutler – Team Alpha
Air sparging is also known as “in situ air stripping” or “in situ volatilization” and is usually used in conjunction with other remediation technologies (US EPA, 2004). Its’ basic function is to volatilize hydrocarbons in the saturated zone, causing a phase-shift from a dissolved state to a vapor phase, where it then can be extracted, or sometimes allowed to mix with ambient air depending on concentration. It is a relatively simple technology, in both equipment needed and in understanding how it works. It uses the chemical properties of hydrocarbons and their intrinsic ability to vaporize easily. The equipment needed and its primary functions are as follows:
· Air compressor – Functions as the input mechanism for fresh, clean air.
· Manifold piping and wells – Delivers the compressed air to the saturated zone.
· Monitoring devices and controls – Allow for adjustment of sparging air flow rate and pressure.
· SVE or other conjunctive remedial technology – Assists in the removal and containment of volatilized hydrocarbons as further explained below.
Soil Vapor Extraction (SVE)
Morgan Bliss – Team Alpha
Soil Vapor Extraction (SVE) is a technology used to lower the concentration of volatile organic compounds (VOCs) and other volatile compounds that are adsorbed to the soil matrix in the vadose zone (USEPA, 2009, p 1). “A vacuum is applied […] through extraction wells which creates a negative pressure gradient that causes movement of vapors toward these wells” (p 2).
In the USEPA document titled “How to Evaluate Alternative Cleanup Technologies for Underground Storage Sites,” Chapter 2 explains the technology necessary to perform this in-situ treatment of the soil. Typical SVE systems will have the following components (USEPA, 2004, Exhibit II-11):
1.) Extraction wells
a. These are fitted with vacuum gauges, pressure indicators, and sampling ports, as well as flow meters.
b. Flow meters can be pilot tubes, in-line rotameters, or venture/flow tubes (p II-25).
c. Vacuum gauges can be manometers or magnahelic gauges (p II-25).
d. When monitoring this removal process, it is necessary to do vapor sample collection as well. This is done through a sampling port, and can be done with Tedlar bags, sorbent tubes, sorbent canisters, or polypropylene tubing for direct GC injection (p II-25).
2.) Condensate Separator
a. This takes the air drawn up by the vacuum and cools it so the volatile compounds are separated out from the ambient air.
3.) Transfer Pump
a. This transfers any of the condensate from the separator and also ensures that any groundwater that is sucked up by the vacuum process is disposed of before it reaches the vacuum/filtration processes. All gathered water is sent to a water storage tank.
4.) Particulate Filter
a. This filters out any dust or dirt that may have been sucked up by the vacuum process so that only the volatile vapors continue on to be treated.
5.) Vapor Extraction Blower / Vacuum
a. The vacuum or blower is what pulls the trapped air from the pore spaces so that it can be treated. This “typically ranges from 3 to 100 inches of water vacuum” (USEPA, 2004, p II-15).
6.) Vapor Treatment Process
a. This treatment process is dependent on the chemical(s) present in the vadose zone soil, and whether it is required in the corrective action plan. A common treatment method is granular carbon adsorption (GAC). The cleaned air can then be discharged to the atmosphere (a permit may be required for this) or injected back down into the soil.
Flushing organics from soil using surfactants
Sachie Dale – Team Alpha
Equipment used is:
Injection well: an injection well is used to pump washing or flushing solution into the soil.
Extraction well: The extraction well pumps out the elutriate (a mixture of washing solution and contaminants).
Separator: The separator is used to separate the washing solution and contaminants. The washing solution is recycled.
Contaminant Treatment: separates treated water, air, and concentrated residuals. Treated water is sent to be recycled, discharged air is sent to air emissions control to be further treated, and concentrated residuals are discharged or perform further treatment.
Extraction of organics using soil flushing can be combined with bioremediation.
Biogenesis soil-washing technology
Equipment used is:
Washing unit: this unit mixes contaminated soil introducing air and also drain wastewater. The unit is equipped with a canvas hood to collect the any organic compounds discharge.
Bioreactor: biodegradation of residual contamination in the wastewater is performed at this tank.
Oil skimmers: Oil is skimmed.
Strainers: Floating solids are collected to avoid them getting into the transfer pump.
Two 7.5-horsepower transfer pumps and hoses: Wastewater in the wash unit is transferred into baffle separator using these pumps.
API oil/water separator: Primary separator of oil from the wastewater. Recovered oil goes to oil storage drums. Wastewater is recycled.
Flushing Metals from Soil Using Chelating Agents
Jamie Ekholm – Team Alpha
The use of chelating agents is one solution for flushing metals from contaminated soils.This process is done either in-situ or ex-situ.In in-situ treatment the soil is excavated mixed with the chelating agent of choice (dependent on the metal and its form) and water to form a slurry.This slurry is processed through one or a series of washing vessels.Once the reaction has taken place, the chelant-metal complex is removed for further treatment and the soil is rinsed and returned to the ground.In the ex-situ method, the chelating agent fluid is either applied to the soil surface via perhaps a sprinkler system where it percolates downward or it is directly injected into the ground via injection wells.Once the chelant-metal complex has reached a certain location, the fluid is then extracted via vacuum pumping in the vadose zone or via a pumping well(s) in the phreatic zone.Again, the chelant-metal complex is further treated once pumped from the soil or groundwater.
There are numerous chelating agents available with ethylenedinitrilotetraacetic acid (EDTA), ethylene triamine pentaaetic acid (DTPA), nitrilotriacetic acid (NTA) and N-(acetamido)iminodiacetic acid (ADA) among the most widely used.
Ion exchange technology
Ali Forouhar – Team Alpha
Ion exchange method is used to Low intensity direct current (DC) is applied through the soil between two anode and cathode electrodes that are installed in the ground. Organic compounds that are negatively charged move toward the anode.Positively charged contaminants such as heavy metals, chromium (VI), arsenic, mercury and ammonium will moved toward the cathode.Then, the contaminants removal is done by precipitation, pumping water near the electrodes, electroplating at the electrodes and finally with ion exchange resins.Ion exchange technology is also being used for single household units that have access to low quality well water only.
Granular activated carbon filtration
Rebeka Fox-Laverty – Team Alpha
Granular activated carbon filtration is the technology used to process and purify gases and liquids.It is an adsorption type of process.It is the process used when you want things like chlorine removed from water. The process is also used to get rid of or at least reduce the odors and tastes in water or wastewater.
There are a few different systems or technologies involved; larger scale, plants or commercial and household or residential. On a larger scale, the Granular activated carbon filtration systems can consist of sand filters, filter beds, and sand anthracite filters.An air scouring system and backwash along with chlorine and ammonia gas treatment systems are also essential in the system. You will also need piping, backwash lines, connecting tees, dip pans (as necessary), tanks, and line clips. There are timers or digital large scale granular activated carbon filtration systems.
The three types of activated carbon filtration units are: A) pour-through; B) faucet-mounted; and C) high-volume. High-volume activated carbon systems are usually installed under sinks and may have valves or a separator that will also filter and separate out cooking water versus drinking waters. A pour-through system is the easiest system of the three and works similar to a coffee maker as one would pour water through the top of the filtration system and allow nature and gravity to act, which runs the water through the system being filtered of any bad chemicals, colors, odors, or tastes. The faucet-mounted systems are filtration systems that are attached to your standard kitchen faucet but with the size and style of the filter require often multiple change outs of the system.
Use of either residential or commercial systems will help eliminate harmful chemicals and smells out of water and make it safer for us to consume.
Tedla Gebre – Team Alpha
Air stripper equipments are used to remove VOCs from the ground water.The EPG low profile tray remove VOCs from groundwater with 99.9% efficiency at a flow rate of 1000gpm.This equipment is simple equipment that can utilize hot air to better strip the VOCs from the water.Using mass and energy transfer, this tool can be highly effective to increasing gpm and more VOC clean water.
This equipment is mobile so that installation can be at the point of the problem.
It is used for landfills, remediation, and industrial.The decontaminated water can be used for many things including drinking as long as there is no toxic material left which is not VOC and not removed by the stripper.
Kyle Gilbert – Team Alpha
A constructed wetland is a man-made wetland that is used to clean or detoxify wastewater.A constructed wetland, also called a constructed marsh or wet park, combines physical filtration, biodegradation, and aerobic/anaerobic as part of its water remediation process.Constructed wetlands are capable of removing nitrogen, phosphorus, and metals.The components of a complete system include a filtered septic tank, a retaining cell that contains an impermeable liner, a gravel substrate, mulch and water-loving plants, a distribution system including header pipe, distribution pipe, collection pipe, water level control structure, various cleanouts and possibly pumps, and a drainage field are all important parts of the remedial technology of a constructed wetland.
Pichtel, John. (2007).Fundamentals of Site Remediation, Second Edition. (pp. 169 – 175). Lanham, Maryland: Government Institutes.
United States Environmental Protection Agency. (2004). How to Evaluate Alternative Cleanup Technologies For Underground Storage Tank Sites: A Guide For Corrective Action Plan Reviewers EPA 510-R-04-002. Washington, D.C.
United States Environmental Protection Agency. (2009, July 21). Soil Vapor Extraction (SVE). Office of Underground Storage Tanks. Retrieved on November 2, 2009 from http://www.epa.gov/swerust1/cat/SVE1.HTM
United States Environmental Protection Agency. (2004, May). How to Evaluate Alternative Cleanup Technologies for Underground Storage Sites: A Guide for Corrective Action Plan Reviewers. Solid Waste and Emergency Response 5401G. EPA Document 510-R-04-002. Retrieved from http://www.epa.gov/swerust1/pubs/tum_ch2.pdf
U.S. Environmental Protection Agency. (1996, April). A citizen’s Guide to In Situ Soil Flushing. Retrieved November 1, 2009, from EPA website: http://www.hsrc-ssw.org/brownfields /frames/documents/brownfields/remediation/communityguides/soilflushing.pdf
U.S. Environmental Protection Agency. (1993, September). BiogenesisTM Soil Washing Technology. Innovative Technology Evaluation Report. Retrieved November 1, 2009 from EPA website: http://www.epa.gov/nrmrl/lrpcd/site/reports/540r93510/540r93510.htm
United States Environmental Protection Agency. (1997). Recent Developments for In Situ Treatment of Metal Contaminated Soils. (p. 33). Retrieved October 30, 2009 from: http://www.epa.gov/swertio1/download/remed/metals2.pdf
U.S. Environmental Protection Agency, Resource Guide for Electrokinetics Laboratory and Field Processes Applicable to Radioactive and Hazardous mixed wastes in Soil and Groundwater from 1992 TO 1997, September 30th, 1997, www.usepa.gov
SAMCO Technologies, Inc. (2009).Granular Activated Carbon Filtration.Retrieved October 31, 2009 from: http://www.samcotech.com/qw_granular_activated_carbon_filters.php
Water and Waste Digest. (2009).Granular Activated Carbon Filtration and Nitrification.Retrieved October 31, 2009 from: http://www.wwdmag.com/Granular-Activated-Carbon-Filtration-and-Nitrification-article599
North Dakota State University. (1992). Treatment Systems for HouseholdWater Supplies, Activated Carbon Filtration.Retrieved October 31, 2009 from: http://www.ag.ndsu.edu/pubs/h2oqual/watsys/ae1029w.htm
Shri Rajpipla Amar Carbon & Chemical Industries.Powdered Activated Carbon.Retrieved October 31, 2009 from:http://www.indiamart.com/amarcarbon/activated-carbon.html
Aqua Science. (2009). Odor and Taste Filtration (Granular Activated Carbon).Retrieved October 31, 2009 from:http://www.aquascience.net/gac/
EPG Companies. (2008). Air Strippers.Retrieved November 3, 2009 from: http://www.epgco.com/air-strippers.html
University of Minnesota Extension. (2001). Innovative Onsite Sewage Treatment Systems. Constructed Wetlands.Retrieved November 3, 2009 from: http://www.extension.umn.edu/distribution/naturalresources/DD7671.html
By Damien Watt
Air sparging is a low cost method of remediation that is used to remove volatile organic compounds (VOCs) and petroleum product from the ground and groundwater.Air sparging is done “in situ” or in place, meaning that uncontaminated air is injected into a subsurface VOCs or hydrocarbon saturated zone, changing the phase of the VOCs from dissolved state to a vapor phase.This method is typically used in combination with other remediation techniques such as soil vapor extraction to increase effectiveness.
There are primarily two factors that determine the effectiveness of air sparging.The two factors are weight of the compound and the permeability of the soil.Air sparging is most effective when used to remove lighter, more volatile compounds such as benzene and toluene.Heavier compounds, more stable such as diesel or kerosene do not work as well with air sparging.The permeability is a factor cause air sparging works to disrupt the equilibrium vapor and dissolved phase of the between the contaminant and the soil and/or groundwater.The passage of air through the soil is necessary for the air sparging to be effective.So knowledge of soil characteristics and the permeability is required when choosing this technique.
The design of an air sparging system requires a multiple tiered approach.It involves the installation of wells to first inject air.“Sparge” points have to be strategically placed in the affected area to get the uncontaminated air into the soil.Then wells have to be installed to monitor the plume of the contaminant to maximize removal efficiency.Lastly wells have to be installed to extract the contaminants once they have been sparged from the soil or the groundwater.All of this information is gathered by conducting what is called pilot testing.Pilot testing is conducted to design the air sparging system effective and is also used to evaluate the system performance as well.
Utilizing air sparging as a remediation technique has it advantages and disadvantages.Air sparging is low cost, easy to install, there are few groundwater consideration to be made, minimal disturbances to affected site, and the equipment in most cases readily available. The disadvantages to an air sparging system is that it can not be used with heavier or more stable compounds, if free liquids exist, can not be used to treat confined aquifers, and it does require an some knowledge of the affected area cause some of the chemical, physical, and biological interactions are not yet understood.Air sparging, if the conditions allow for the technique to be used, can be a cost effective method to remediate an affect site with minimal disturbances.
EPA. (1995, May). Air Sparging. In How to Evaluate Alternative Cleanup Technologies for Underground Storage Tank Sites: A Guide for Corrective Action Plan ReviewersHow to Evaluate Alternative Cleanup Technologies for Underground Storage Tank Sites: A Guide for Corrective Action Plan Reviewers. Retrieved
Subsurface barriers: Grout Curtains
By David J. Seidel
Grout curtains are rigid underground barriers formed by injecting grout into porous rock or soil through wells. It offers several advantages as a remediation technology:
1.With a grout curtain, soil heterogeneity has much less of an impact on wall placement than a slurry wall (Dwyer, 1994)
2.Versatile – grouting can stabilize a wide variety of soil types ranging from gravel to
heavy clays (Mutch et al., 1997)
3.Starting from a small borehole, large diameter columns or panels can be created (Dwyer, 1994)
4.Grouting can install a wall (inject) in confined places that might otherwise limit installation – for instance, cut-off walls can be constructed beneath buildings without disrupting the structure (Mutch et al., 1997)
5.Grout curtains can be installed at depths up to 150 – 200 ft (Dwyer, 1994)
6.Drilling can be done at any angle forming both vertical and horizontal water control barriers (Dwyer,1998)
7.Grout unitsare mobile, permitting drilling with rotation and percussion (Dwyer,1998)
8.A down-the-hole (DTH) percussion hammer coupled with the drill string results in more
reliable drilling alignments (straight and parallel), faster drilling rates, and a quieter
operation (Dwyer, 1998)
9.Innovative equipment allows injection of multiple fluids or gases (Dwyer, 1998)
a. DTH percussion hammer
b.Multi-nozzle grout injection unit increases the efficiency of injection
10.Grout curtains can be used in coordination with subsurface treatment.
1.Mutch, R.D., R.E. Ash, and J.R. Caputi. 1997. “Contain Contaminated Groundwater.” Chemical\Engineering, Vol. 104, No. 5, pp. 114-119.
2.Dwyer, B.P. 1998. “Treatment of Mixed Contamination in Complex Hydrogeologic
Settings.” Sandia National Laboratories.
3.Dwyer, B.P. 1994. “Feasibility of Permeation Grouting for Constructing Subsurface Barriers.” SAND94-0786
Organic contaminants can be found in many different soil types and textures and contain different physical and chemical compounds. Organic contaminants are usually non-volatile, insoluble in water, not readily biodegradable, some extremely toxic, and have a low molecular weight are general characteristics.The hydrophobic organic contaminants are dioxins, furans, PCBs and polyaromatic hydrocarbons are found in lower doses in soil. Organics with a low molecular weight would consist of alcohols, phenols and carboxylic acids but chlorinated dibenzodioxins would be an extreme toxic organic contaminant. Now, we have identified the characteristics and given examples of organic contaminants. the objective will to find a soil flushing co solvent or surfactant to remove the contaminants from the soil.
Common field information and gathering often includes the description of the incident, natural soil exposures, weathering that has taken place, subsurface cores, and soil sampling. This effort will identify the organic contaminant, the areas of past and present disposal through observations and information on the soil analysis. The overall objective of soil flushing is to minimize cost during the removal of organics while satisfying various requirements and specifications
The picture is a typical soil flushing system provided by FRTR remediation technologies http://www.frtr.gov/matrix2.html
Surfactant flushing involves injecting a surfactant mixture (example: water plus a miscible organic solvent such as alcohol or a special surfactant) into the contaminated area to extract organic contaminants.The aqueous mixture dissolves and mobilizes the organic. Water flooding is use to remove the residual effluent above ground and the recovered fluid can be reused in the flushing process to keep cost down. The residual solids and sludge are properly treated before disposal. Some cases air emissions of volatile contaminates from recovered flushing fluids should be collected and treated, to meet regulatory standards.
Advantages to using surfactant remediation is the use of certain surfactant can keep cost down during removal. The use of certain surfactants can enhance soil porosity and texture. The use of soil flushing can remove an organic contaminant faster out of the soil than other remediation programs. Also,eliminates the need to excavate, handle, and transport contaminated media. Surfactants mobilizes the contaminated area from spreading to other areas while being removed.
Fundamentals of Site Remediation. John Pichtel. 2nd ed. pp.175 - 177.
AF Center for Engineering http://www.afcee.af.mil/resources/technologytransfer/programsand initiatives
FRTR Remediation Technologies Screening Matrix and Reference Guide, http://www.frtr.gov/matrix2/section2/2-2-1.html.
Interstate Technology Regulatory Council, http://www.itrcweb.org.
By Rob Walker
Bioreactors are enclosed tanks that are used primarily in the biodegradation of Organic toxins. Bioreactors treatment of slurry-phase contaminated soil or sludge.The slurry is formed by the addition of water to contaminated soil in order to form a slurry density that is desired.The slurry is mixed to maintain suspended soils and to increase contact between microorganism and contaminated materials.Bioreactors can be aerobic or anaerobic.Biodegradation in Bioreactor is affected by pH, temperature, nutrients, concentration of contaminants, microorganism, dissolved Oxygen and aeration in aerobic systems.Bioreactors are commonly used due to the low cost to operate, using minimal man power and minimal sludge.Bioreactors are very efficient at degradation of recalcitrant compounds and very efficient at removal of toxic substances. Disadvantages are; long optimization time, extensive design time, requires large area of land, poor understanding of microbial biokinetics, and lack of VOC control.
In conclusion Bioreactors are an efficient way to remove anthropogenic organic compounds from soil. Bioreactors provide a low cost remediation technique. Bioreactors require a large amount of area, VOC emissions must be taken into account when considering using Bioreactors.
Alok Bhandari, A. B., Rao Y Surampalli, R. Y. S., Passcale Champagne, P. C., Say Kee Ong, S. K. T., R D Tyagi, R. D. T., & Irene M C Lo,
Juana B. Eweis, J. B. E., Sarina J. Ergas, S. J. E., Daniel P Y Chang, D. P. Y. C., & Edward D Schroeder, E. D. S. (1998). Bioremediation Principles.
The Advantages and Benefits of
Team Delta – Dan South
A chelating agent is a molecule that has several localized negative groups that can bond strongly with a metal cation, thereby making the cation unavailable for other bonding and essentially inactive (Williams, James, and Roberts, 2000).There are many benefits to using chelating agents in a fluid to flush metals out of soil.
The first benefit is that by locking up the binding sites, the agent prevents or at least reduces the ability of the metal cation to form insoluble complexes or to adsorb onto soil particles.This makes the metal more vulnerable to remediation.By adding properly chosen chelating agents that make the target metal more soluble, a person can extract more of the compound by methods such as extraction wells (Peters, 1999).In one study, researchers were able to remove 85% of the copper in a test column from all soil fractions, even the clay fraction where the metal bonds the strongest (Tsang, Zhang, Lo, 2007).Other experiments showed that by using different chelating agents or changing the techniques in administering the chelating agent, a person can remove almost 100% of lead or 73% of copper in a contaminated soil, much better than can be achieved using just water alone (Peters, 1999).A third benefit is that soil flushing with chelating agents can be more economical and safer than soil removal or soil washing because there is no excavation required (Tsang, Zhang, Lo, 2007).This would reduce impact on an active area such as a operating industrial facility.There is no soil that needs to be moved, hauled, or disposed of.The safety effect is also important as construction projects can be extremely dangerous having had nearly 1,000 fatal injuries in 2008 (U.S. Dept. of Labor, 2009).
In summary, using chelating agents to flush metals from soil can have several beneficial effects.It isolates the metals from other molecules by locking up the binding sites.It also makes the metals more soluble and therefore easier to extract.Because of that, using chelating agents with soil flushing fluids increases the amount of metals that can be extracted from contaminated soil.By being an in-situ technique, soil flushing can be less expensive in terms of money and human safety.
Peters, R. W. (1999). Chelant extraction of heavy metals from contaminated soils. Journal of Hazardous Materials, 66(1-2), 151-210.
Tsang, D. C. W., Zhang, W., & Lo,
Williams, P. L., James, R. C., & Roberts, S. M. (Eds.). (2000). Principles of toxicology (Second ed.).
Granular Activated Carbon Filtration
By Mary Steffen-Deaton
Granular Activated Carbon (GAC) Filtration is a treatment method that can be used to remove contaminates from water and air.“A GAC filter system is used to remove semi-volatile and volatile organic compounds (SVOCs and VOCs), such as constituents of gasoline, heating oil, and chlorinated solvents, from polluted drinking water.”(DEP, 2006).Granular Activated Carbon Filtration uses filters made of natural materials from coal, wood, lignite, peat, coconut shells, and coke and then an adsorption process occurs to remove contaminates from liquids and gases.Each of the types of materials in the filter has its own adsorption properties so to remove specific contaminates.The contaminated water is directed through the GAC columns or canisters and a heat source like steam is used to expand the surface area of the carbon to help remove the dissolved organics then the pollutants are removed releasing water free of contaminates or at lower levels.This can be an effective method in removing chlorine, and volatile organic compounds that are carbon based. “Adsorption by activated carbon has a long history of use in treating municipal, industrial, and hazardous wastes.” (Pitchel, 2007).
1.Not too costly as far as treatment cost go.
2.The average well owner can have this method installed to help remove man-made and naturally occurring organics. So whole homes can have systems to prevent ingestion of contaminates.
3.The GAC systems do not restrict flow nor do they produce any wastewater.
Pichtel, John.Fundamentals of Site Remediation. 2nd ed. 2007,
Department of Environmental Protection. 2006, Bureau of Water Protection and
Samco Technologies, Inc.From:http://www.samcotech.com/qw_granular_activated_carbon_filters.php
By Doug Sposito
Air Stripping is a treatment system that removes volatile organic compounds (VOCs) from contaminated ground water or surface water by forcing an air stream through the water and causing the compounds to evaporate.
Engineers use the Henry’s law constant to determine if air stripping will be a good treatment method.Henry’s law states that at a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.Constants in the range of 10-5 to 10-3 m3/mol are required.Volatile organics with a constant less than 10-5 evaporate too slowly.Benzene toluene and chlorinated are typical molecules suitable for air stripping.
Another consideration is the air to water flow ratio.Ratios ranging from 5-200 are considered good.Too much air flow will prevent the water from moving and create a condition known as “flooding”.
Air strippers are advantageous due to the relatively low installation and operational costs and ease of operation.Air strippers are now considered a proven technology.Air strippers only need intermittent checking by a technician so are useful in remote locations also reducing the financial costs for those responsible for maintaining the system.The disadvantages are the limited use to only volatile organic compounds.Air stripping unfortunately is also a mass transfer technology; transferring the contamination from one environment, the ground water to another, the air.
If the water contains other contaminants it may need to be pretreated.Iron and hardness also need to be removed prior to treatment.
In a typical air stripper the water is also oxygenated as it is moved opposite of the air current.This oxygenation precipitates the iron out of solution; a necessary step prior to treatment.If the water tests hard, calcium and magnesium would also need to be precipitated and removed prior to treatment to help avoid clogging of the system.
Controlling environmental pollution: an introduction to the technologies ...
By P. Aarne Vesilind, Thomas D. DiStefano
Control of emissions from an air stripper treating contaminated groundwater
W. D. Byers
Industrial Processes and Hazardous Waste, CH2M HILL,
Development of an Air-Stripping and UV/H2O2 Oxidation Integrated Process To Treat a Chloro-Hydrocarbon-Contaminated Ground Water
Benefits of Constructed Wetlands
Constructed wetlands are just as the name implies- they are replicas of natural wetlands made by man. Wetlands are a natural filtration system trapping contaminants and sediments that are received by runoff, precipitation and environmental “incidents” such as spills. These contaminates are then biodegraded through various processes. One such process is the uptake of said contaminants through plant roots and then releasing them to the air. Another process is by trapping them in the plant root matrix where they can be collected and disposed of.
So why fabricate a constructed wetland? Because you get all the benefits of a natural wetland at basically any location you desire. Establishing a constructed wetland is a relatively simple process including excavating, inserting a liner (if needed), laying a dike of desired size and water control devices (if applicable). Once this has been completed, the vegetation is planted. Care must be taken in choosing the type of vegetation as certain plants are needed for maximum uptake. Growth of natural vegetation can also occur. Another benefit of constructed wetlands is that they are cheaper to build than a water treatment plant and maintenance and operation costs are low in comparison.
Constructed wetlands are frequently used to treat water from treatment plants and have been shown to be highly effective in removing metals from other sources of contamination. But this is not the only location where they are useful. In addition to pollution control and low costs, constructed wetlands also provide habitats for various flora and fauna and, depending on location, serve as public attractions.
Picture from Federal Remediation Technologies Roundtable
Constructed Wetlands- Natural processes t treat water, Build Habitats
Innovative Onsite Sewage Treatment Systems: Constructed Wetlands
EPA-Constructed Treatment Wetlands