Power of Simplicity
The EPA’s Citizen’s Guide to Cleanup Technologies
Series 6: Permeable Reactive Barriers
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 Permeable Reactive Barriers. You can reach it through the hyperlink under the blue header below.
If you dress in cotton and dance in the rain, it will soak the cotton and pass to the skin. Water permeates cotton. Cotton is permeable to water.
Photograph by Daniel Lin, licensed under Creative Commons Attribution-Share Alike 2.0 Generic License
Permeate originates with Latin; per mean through and meare means to pass.
In broader terms, permeability is the property of a material that allows liquids, vapors or gases to pass through it.
Beach sand is highly permeable. When the waves or tide retreat, they leave no ponds behind: all water has soaked down.
Clays and silts present low permeability. Water will pond until it evaporates.
In chemistry, a reactive substance is a substance that acts chemically on another substance or substances.
Hydrochloric acid is dangerously reactive. It will instantly burn through flesh. (Wear highly protective gear if you plan on working with acids.)
Soaps are mildly reactive. They break oils into particles that become soluble in water and can be rinsed away.
A barrier is something that stands in the way; that stops progress or prevents an approach.
(Ref. The World Book Encyclopedia Dictionary.)
Great Wall of China near Jinshanling
Photographer: Jakub Halun, Licensed under the GNU Free Documentation License, Version 1.2
The word originates with Latin barra, bar. A barrier is an object that bars.
When we speak about permeable barriers, it seems that we have entered a field of oxymorons.
The operative word is reactive.
A permeable reactive barrier, or “PRB,” allows groundwater to flow (permeate) through it. Within the barrier we have reactive materials that trap harmful contaminants or reduce their harm through chemical or biological processes. The treated groundwater flows out the other side of the wall.
The PRB bars the progress of the contaminants and allows the treated groundwater to proceed.
Go to the EPA’s Citizen’s Guide to Permeable Reactive Barriers at http://www.clu-in.org/download/Citizens/a_citizens_guide_to_permeable_reactive_barriers.pdf for the rest. It is simple and fun to read.