Air stripping is a mass-transfer process whereby volatile contaminants are stripped out of the aqueous solution and into the air. The process exposes the contaminated water to a fresh air supply which results in a net mass transfer of contaminants from the liquid phase to the gaseous phase. Contaminants are not destroyed by air stripping but rather are transferred into the air stream where they may need further treatment. Air stripping applies to volatile and semivolatile organic compounds. It does not apply to low volatility compounds, metals, or inorganic contaminants.
Several types of air stripping technologies are available including tray aeration, spray aeration, and packed towers. Among these technologies, packed tower aeration
(PTA) is the most commonly applied to remove volatile organics from groundwater. In a packed tower, the contaminated water comes in contact with a countercurrent flow of air. The packing material in the tower breaks the water into small droplets and thin films causing a large contact area where the mass transfer can take place. Figure 9.17.14 shows a typical treatment process using air stripping.
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