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P.a <br /> i M10 <br /> gigff& <br /> e <br /> e Bir Strjppina <br /> In air stripping, recovered ground water :is pumped <br /> into the top of a column and flows downward through <br /> a packing material. Air is forced upward through <br /> the column, providing sufficient air-water contact <br /> to typically remove over 99 percent of dissolved <br /> BTEX constituents. The treated water leaves the <br /> bottom of the column and is discharged or treated <br /> further if required. Air leaving the top of the <br /> tower may also require further treatment prior to <br /> discharge to the atmosphere. Air stripping is <br /> typically used when hydrocarbon contaminant levels <br /> mm are too high for economical activated carbon <br /> treatment of water. <br /> e Combined_A$,gStrippj-ng an a.r,,,r n am p jj _ <br /> Combined use of air stripping and carbon adsorption <br /> is warranted when constituents have a wide range of <br /> volatilities, when stringest treatment requirements <br /> exist, or when influent hydrocarbon concentrations <br /> are relatively high. Air stripping selectively <br /> removes the most volatile components from the water <br /> and leaves residuals of less volatile compounds. <br /> Carbon adsorption will remove most of these less <br /> volatile constituents from the stripped water. <br /> Carbon adsorption is also often used to polish <br /> water or remove contaminants from the air emitted <br /> from the stripping tower. Generally, air stripping <br /> followed by carbon adsorption may be cost effective <br /> in situations where hydrocarbon concentrations <br /> exceed 10 ppm. <br /> 11ioloa'c�Z_Treatment <br /> Biological treatment techniques used by municipal <br /> wastewater facilities can be scaled down_ and <br /> applied to removal of dissolved hydrocarbons from <br /> ground water. The hydrocarbons can serve as a food <br /> source for certain aerobic microorganisms that <br /> convert the organic compounds into carbon dioxide, <br /> water, energy, and biological solids. <br /> Disadvantages of biological treatment include <br /> higher capital, operating, and maintenance costs. <br /> Also, biological systems are more complex than <br /> other treatment systems and may be more prone to <br /> problems. For these reasons, biological treatment <br /> - ----of--ground-Nater--3.s -not-widely-practiced. <br /> 23 ". <br />