Air Stripping

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Air Stripping

• What is air stripping?
• How does it work?
• What are its advantages above other treatment
  processes?
• What are its disadvantages?
• What kind of cost is required to build and
  maintain an air stripping process?
• Who makes air stripping products?

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What is Air Stripping?

• Air stripping is the process of forcing air
  bubbles through polluted water to remove harmful
  or unwanted chemicals. The air moving through the
  water causes the chemicals to change to a gaseous
  state. This gas is then bubbled out of the water
  with the air. This air and other gas mixture is
  then collected and cleaned. Air stripping is
  commonly used to treat groundwater.

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How Does Air Stripping Work?

• Water that has unwanted volatile contaminates
  (pollution) such as produced water from the oil
  industry can be cleaned using a variety of air
  stripping methods.
• Sprayed over packing material to maximize the
  surface area of the water exposed to air being
  pumped in.
• Aeration tanks can be used to remove the need for
  packing materials.

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A Basic Air Stripping Process
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An Air Stripping Packed Tower
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Some Pros and Cons

• Other equipment can be added to the basic air
  stripper. These additions can include
• An air heater to improve removal efficiencies due
  to higher energy of the system.
• Control systems that regulate water level with
  sump level switches.
• Safety features, such as
• Differential pressure monitors
• Explosion-proof components
• Air emission treatment systems

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• Packed tower air strippers are installed either
  as permanent installations on concrete pads or on
  a skid or a trailer.
• Aeration tanks can reduce the size of the
  strippers
• Aeration Tank less than 2 meters or 6 feet high
  
• Packed Tower 5 to 12 meters or 15 to 40 feet
  high
• Air stripping works best when the water contains
  chemicals that evaporate easily.
• This includes fuels and solvents.
• Air stripping can remove up to 99 of these
  chemicals when the process is designed properly,
  and on average the process removes over 95 of
  the waters impurities.

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• Air strippers are relatively less complicated to
  construct than other filtration processes and
  they are also easier to maintain.
• The Air stripping process cannot remove metals,
  PCBs (polychlorinated biphenyls, totally man
  made), or other chemicals that do not evaporate.
• The major problem encountered with packed tower
  air strippers is fouling of the packing. This
  reduces the air flow rate through the system.
• Fouling is caused by the oxidation of minerals in
  the water being fed into the system.
• These minerals can include iron and manganese.
  Also, precipitation of calcium, and biological
  growth on the packing material can add to the
  fouling.
• Air stripping has been used to clean up
• polluted water at hundreds of ground water and
  waste sites.

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Cost Concerns

• One of the major operating cost of an air
  stripping process is the electricity required for
  the polluted water pump, the sump discharge pump,
  and the air blower.

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In Situ Air Stripping of Contaminated Groundwater
at U.S. Department of Energy Savannah River Site
Aiken, South Carolina
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• Equipment Costs Site Costs
• Design and Engineering 5,000
• Site Costs 5,000
• Mobile Equipment 15,000
• Total Site Costs 5,000
• Capital Well Installation Labor Costs
• Air Injection Well 93,323 Mobilize/Demobilize
• Air Extraction Well 76,762
• Technician-2 12,000
• Subtotal Well Installation 170,085
• Laborers-2 10,000
• Oversight Engineer-1 12,000
• Air Injection 3,500
• Per diem 3,600
• Air Extraction System 5,000 Monitoring/Maintenanc
  e Crew
• Vapor Air Separator 2,750
• Technician-1 8,340

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• Carbon adsorption Unit 10,000
• Oversight Engineer-1 16,680
• Duct Heater 3,250
• Total Annual Labor Costs 62,620
• Water Treatment Unit 4,000
• Monitoring Equipment 17,000
• Temporary Storage Space 1,500
• Carbon Recharge 101,688
• Portable Generator 3,500
• Fuel Oil-diesel 35,362
• Fuel Storage 1,500
• Lubricants 6,950
• Piping and installation 5,200
• Deionized Water 3,336
• Electrical 6,240
• Chemical Additives 6,950
• Subtotal Other Equipment 63,440
• Maintenance Supplies 3,475
• Total Equipment Costs 253,525

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According to this Report

• This process can better clean polluted water for
  60 of the total instillation and maintenance
  costs.

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A Survey of Offshore Oilfield Drilling Wastes and
Disposal Techniques to Reduce the Ecological
Impact of Sea Dumping
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• Technology
• Air stripping
• Processes
• Packed tower with air bubbling through the
  produced water stream.
• Advantages
• Can remove 95 of volatile compounds as well as
  benzene, toluene, naphthalene, phenanthrene,
  anthracene, pyrene and phenols H2S and ammonia
  can be stripped but pH must be adjusted higher
  temperature improves removal of semi-volatiles
  small size, low weight and low energy
  requirements simple to operate well-known
  technology.

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• Disadvantages
• Can be fouled by oil risk of iron and calcium
  scales forming generates an off-gas waste stream
  that may require treatment requires some
  pre-treatment of produced water stream.
• Costs
• Low capital and operating costs overall
  treatment cost US0.02 to 0.10/1,000 gallons,
  plus 0.50 to 1.50/1,000 gal if off-gas control
  by activated carbon is required.

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References

• http//www.frtr.gov/matrix2/section4/4_50.html
• https//www.denix.osd.mil/denix/Public/Library/Rem
  edy/Savannah/toc.html
• http//www.cpeo.org/techtree/ttdescript/airstr.htm
  
• http//www.offshore-environment.com/productionwate
  rs.html
• http//www.epa.gov/superfund/sites
• http//www.cluin.org