Remediation Technologies and Implementation Equipment

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.

Air Stripper

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.

Constructed Wetlands

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.

References

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 30^th, 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 Household Water 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