Air sparging

When contaminant air rises above the water table into the vadose zone, the VOCs are captured by soil-venting extraction, escape to the atmosphere, or are treated as they encounter indigenous bacteria present in that zone. 

When air sparging is halted, and vapor extraction processes are stopped, the subsurface will again approach a state of equilibrium that is consistent with the lower energy effort. The partitioning gradient that had existed under active sparging 

The effectiveness of air sparging as a remediation tool depends on several variables, including soil type, the method of air injection, and the type and concentration of contaminants. The particle size and gradation of a particular soil determine the flow pattern in which the injected air will travel. 

Use of pulsed air injection rather than continuous air injection may improve performance at many sites. After a system has been operating for a period of time, the concentration of contaminant in the recovered air declines. Continued injection of the same volume of injected air recovers less VOC. Injection of air in a pulsed pattern allows time for reestablishment of a greater concentration gradient toward air channels and a more uniform concentration throughout the contaminant plume area. When the system is resumed, volatilization is again the predominant removal mechanism. 

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Foaming characteristics of lubricating oils NFT 60-129 ISO/DIS 6247 ASTM D 892 Air sparging and measurement of foam after standing... 

Air sparging Air thane Air toxics Airwick AISI1010 [112725-33-6] AISI304 [11109-50-5] AISI430 [11109-52-7] AISI 4820 [35724-97-5]... 

R. E. Hiachee, R. M. Miller, and P. C. Johnson, eds.. In situ Meration Air Sparging Bioventing and Belated Kemediation Processes, BatteUe Press, Columbus, Ohio, 1995. 

R. E. Hiachee, ed.. Air Sparging for Site Kemediation, Lewis PubUshers, Ann Arbor, Mich., 1994. 

Pressure. Within limits, pressure may have Htfle effect in air-sparged LPO reactors. Consider the case where the pressure is high enough to supply oxygen to the Hquid at a reasonable rate and to maintain the gas holdup relatively low. If pressure is doubled, the concentration of oxygen in the bubbles is approximately doubled and the rate of oxygen deHvery from each bubble is also approximately doubled in the mass-transfer rate-limited zone. The total number of bubbles, however, is approximately halved. The overall effect, therefore, can be small. The optimum pressure is likely to be determined by the permissible maximum gas holdup and/or the desirable maximum vapor load in the vent gas. 

Sulfurchlorination of unsaturated compounds or mercaptans is normally carried out at atmospheric pressure in a glass-lined reaction vessel because of the potential to Hberate HCl during the reaction. The sulfurchlorination vessel is equipped with a cooling jacket or coils (very exothermic reaction), a nitrogen or dry air sparging system, an overhead condenser, and a caustic or bleach scmbber. If one of the reactants (olefin or mercaptan) is alow boiling material, ie, isobutylene, a glass-lined pressure vessel is recommended. 

Ex situ bioremediation may use various biological wastewater treatment processes, soil piles, or land appHcation. With in situ bioremediation, the basic process is the same microbes, soil, and water working together as a bioreactor. Where the in situ techniques differ are in how contaminants and microbes are brought in contact and how oxygen, nutrients, and other chemical supplements ate distributed in the soil—water—air matrix. Typical in situ bioremediation techniques include natural or intrinsic attenuation, air sparging, and bioventing. 

API, In Situ Air Sparging. Evaluation of Petroleum Industy Sites and Considerations for Applicability, Design, and Operation, Pubhcation No. 841-46090, American Petroleum Institute, Washington, D.C., 1995. 

In 1981, a novel flotation device known as the air-sparged hydrocyclone, shown in Figure 3, was developed (16). In this equipment, a thin film and swid flotation is accompHshed in a centrifugal field, where air sparges through a porous wall. Because of the enhanced hydrodynamic condition, separation of fine hydrophobic particles can be readily accompHshed. Also, retention times can be reduced to a matter of seconds. Thus, this device provides up to 200 times the throughput of conventional flotation cells at similar yields and product quaHties. 

Fig. 3. Air-sparged hydrocyclone, where A represents the tangential feed that estabHshes swid flow B, the area of small bubbles formed by high shear at the porous wall and C, the outlet for the (D) hydrophilic particles rejected by the swid flow. The (B) hydrophobic particles are in the axial froth flow.

Other approaches to increase current density without impairing cathode quaUty include air sparging, high velocity forced circulation of electrolyte, and the use of an abrasive belt or abrasive slurry for scmbbing the surface of the cathode. 

Adequate ventilation is necessary for aH process lines to ensure worker safety. Electroless copper baths must have good ventilation to remove toxic formaldehyde vapors and caustic mist generated by the hydrogen evolution reactions and air sparging. Electroless nickels need adequate ventilation to remove nickel and ammonia vapors. Some states and municipalities requite the removal of ammonia from wastewaters. A discussion of printed circuit board environmental issues and some sludge reduction techniques is avaHable (25). 

Biihhle-diameter correlation for air sparged into relatively inviscid liquids. Dt, = hiihhle diameter, D = orifice = gas velocity through sparging orifice, P = fluid density, and 1 = fluid viscosity. [From Can. J. Chem. Eng., 54,... 

FIG. 19-79 Variations in the basic column design a) packed column, (h) Jameson cell, and (c) air-sparged hydrocyclone. 

This is 90% nitric acid, d. 1.48-1.50. In order to remove dissolved nitrogen oxides from it, 0.5 g. of urea is added and the mixture is air-sparged for 20 minutes. The acid should be colorless before it is added to the acetic anhydride. 

The nitrating mixture should be colorless at this point. If it is not, 0.5 g. of urea should be added and the mixture air-sparged until colorless. 

A published account of laboratory batch sulfations of Alfol 1214 SP, Alfol 1216 SP, and natural coconut alcohol using chlorosulfonic acid at atmospheric pressure and 16 L/min dry air sparged through the reaction mixture to remove HC1 is available [42], The optimal conditions and the characteristics of the triethanolamine alcohol sulfates obtained are shown in Table 1. 

In situ bioremediation techniques combined with SVE and air sparging... 

The combination of SVE with air sparging technology. Air sparging involves the injection of air into the saturated zone of contaminated groundwater. The air bubbles enhance the... 

Air sparging systems, involving the injection of air directly into the groundwater... 

An important innovation in bioremediation technology has been the use of air sparging to oxygenate groundwater. A typical system is presented in Figure 14.6. Using this technique, the removal of contaminants is achieved using two simultaneous mechanisms ... 

A continuous oxygen supply is thus achieved, which is limited only by the mass transport phenomena between the gas and aqueous phases this is the main advantage of air sparging over the alternative of water circulation systems. 

Depth of air injection. The end of the well from which air sparging is conducted is usually located 30 to 60 cm below the contaminated area. 

Kirtland, B.C. and Aelion, C.M., Petroleum mass removal from low permeability sediment using air sparging/soil vapor extraction impact of continuous or pulsed operation, J. Contam. Hydrol., 41, 367-383, 2000. 

Washington, J.B. and Ong, S.K., Air sparging effectiveness laboratory characterization of air-channel mass transfer zone for VOC volatilization, J. Hazard. Mater., 87, 241-258, 2001. 

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