Environmental Enlightenment #202
By Ami Adini - Reissued May 10, 2017

This is a SHORT, LIGHT and SIMPLE newsletter. Its purpose is to rekindle in the initiated terminology they have once learned, and enlighten the uninitiated on terms they may have heard but never knew the meaning of.


Power of Simplicity
The EPA’s Citizen’s Guide to Cleanup Technologies




Series 3: Soil Vapor Extraction and Air Sparging

See our Newsletter, Environmental Enlightenment #200, for introduction to one highly valuable, plainly written series of Citizen’s Guides published by the EPA at http://www.clu-in.org/products/citguide

With this issue, we introduce the EPA’s Citizen’s Guide to Soil Vapor Extraction and Air Sparging. You can reach it through the hyperlink under the blue header below.


http://www.clu-in.org/download/Citizens/a_citizens_guide_to_soil_vapor_extraction_and_air_sparging.pd


Sparging is the action of bubbling gas or air through liquid. (Wikipedia)



Vapors consist of molecules that move off from a substance.


All what matter is, is a balled-up conglomeration of motions and when enough energy is present, certain motions detach from the “mother ship” and become “vapor.”
 
Illustration © Rod Nave, HyperPhysics

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
  http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/imgkin/vapp3.gif

In a greater or lesser degree, all substances give off vapors: water spilled on the floor disappears after a time; it has evaporated.

Certain liquids evaporate faster than other liquids.

Acetone evaporates fast, really fast.

Lead evaporates slow, very slow.


I remember a guided tour back in 1978 at the Yale campus in New Haven, Connecticut. Our guide pointed to parts of a leaded roof that evaporated over the ages.


Photo credit: Kevin Rosseel, Morguefile.com

If you spill a liquid in a closed room, after a time its vapors will fill up the room and the puddle will stop evaporating. 

Illustration © Rod Nave, HyperPhysics
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

  http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/imgkin/vapp3.gif

The same happens to liquids that penetrate the subsurface soil; they give off vapors that permeate and fill up the pores of the soil.

Comparative pore space:
Left: soil with large pore space.
Right: Compacted soil lacking large pore space
.

Illustration courtesy of Colorado Master Gardener Program, Colorado State University Extension
(http://www.cmg.colostate.edu/gardennotes/213.html)

Soil pore space
If you want to dry up moisture, you blow air upon it  

The air stream captures the molecules that the substance gives off and carries them away, thus enabling the substance to release additional vapor.


In a similar way, we use vacuum to induce airflow through the soil. We want it done by vacuum rather than pressure because we want the captured, toxic vapor to be drawn into our suction machines, which feed it to the vapor treatment part of the operation where the vapor is destroyed or captured for treatment off site.


©1998, Daniel Gallagher (http://www.webapps.cee.vt.edu/ewr/environmental/teach/gwprimer/svent/svent.html)

This operation is called soil vapor extraction or SVE.

By its very nature it can work only on the soil that is above the water table.

Sparging is used to remove volatile contaminants that have lodged in the saturated soil under the water table.


Image courtesy of NEXT Environmental Inc. (http://www.nextenviro.com)

Air is bubbled under pressure, and the bubbles search ways to rise in the aquifer. The tighter the aquifer (for example, clay), the harder it is for the bubbles to move. Thus, sparging works best with loose aquifers. Various combinations of sand, gravel, silt, and clay make for loose aquifers. Solid layers of clay and silt make aquifers tight.

Go to:
http://www.clu-in.org/download/Citizens/a_citizens_guide_to_soil_vapor_extraction_and_air_sparging.pdf
for the rest.

It is easy to understand and… interesting!

You can find past issues of "Environmental Enlightenment" at www.amiadini.com with wealth of information about issues concerning assessment and cleanup of contamination in the subsurface soil and groundwater.

Call me if you have any questions. There are no obligations.

Ami Adini Environmental Services, Inc.
Environmental Engineering Consultants & Contractors
Underground Storage Tank Experts
California Lic. #1009513 A B HAZ ASB
818-824-8102; mail@amiadini.com
www.amiadini.com

Ami Adini is a mechanical engineer, California Registered Environmental Assessor, Level II (Exp.), and president of AMI ADINI ENVIRONMENTAL SERVICES, INC. (AAES), an environmental engineering consulting firm and general contractors specializing in all phases of environmental site assessments, rehabilitation of contaminated sites and upgrading of underground storage tank facilities. AAES provides practical solutions to environmental concerns using the highest standards of ethics and integrity while providing its clients with maximum return on their investments.