Air sparging systems

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. 

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

In an air sparging system, the primary mechanism for contaminant removal is by the transfer of contaminants from the dissolved to the vapor phase. The extent to which this transfer can take place during air sparging depends on the Henry s law constant, which is an indication of the extent to which each will partition between the dissolved state and the vapor state under equilibrium conditions. A contaminant with a greater Henry s law constant is more readily stripped from groundwater by air sparging than one with a lower Henry s law constant. 

Design of an air sparging system requires a balanced airflow to maintain effectiveness and control of the migration of fluids and vapors. Because of the potential for loss of control, an air sparge system should not be designed or installed without a field pilot test. Design data from pilot tests include ... 

Site and Pilot Test Data Required for Air Sparging System Design... 

Designing an effective air sparging system is as much art as science. In its best form, it has the potential to provide an effective and efficient remedial alternative. If it is poorly designed and operated, air sparging can lead to adverse environmental consequences. 

Spartech is a mobile system designed for the removal of volatile contaminants from aquifers. It is a patented air sparging system that works by bubbling air through an aquifer and is essentially an in situ method of air stripping. The volatilized contaminants may be recovered by using a soil vapor extraction (SVE) system or similar device. 

The ORC system is designed to treat a plume with a peak BTEX concentration of 25 ppm and close the site in 1 year. The values for the air sparging system were derived independently by the site consultant and site closure is expected in 3 years (D138231). 

Steffan et al. [45] isolated a propane-oxidizing strain ENV 425 which was able to convert MTBE to CO2. This strain has been used to establish a biobarrier in an MTBE plume in New Jersey [49]. An air-sparging system at the site was tested, but was not successful in degrading MTBE. Therefore, propane was added to the sparge air for 10-minute periods at intervals of three hours each. Since natural microbial populations were low at the site (perhaps because of an unfavorable environment of about pH 3), one month later a culture of the propane-oxidizing strain ENV 425 was injected directly... 

Linek, V., Benes, E, and Hovorka, F. (1981), Role of interphase nitrogen transport in the dynamic measurement of the overall volumetric mass transfer coefQcient in air-sparged systems, Biotechnology and Bioengineering, 23(2) 301-319. 

Soil Vapor Extraction System. Once the air is injected into the saturated subsurface, it wiU migrate toward the surface due to the effect of buoyancy. Eventually the contaminated injected air will enter the vadose zone. At this point, a sou vapor extraction (SVE) system may be implemented. Soil vapor extraction applies a vacuum to the vadose zone to assist in collecting vapors. The vacuum will help vapor collection as well as assist in preventing unwanted off-site migration. Equipment used in a soil vapor extraction system is similar to that used in an air sparging system, except that a vacuum pump is used instead of an air compressor. Additionally, if the vapors being collected by the soil vapor extraction system are moist, a dewatering system may be employed (Johnson et al., 1993). 

In addition to proper system design and layout, proper choices regarding the operating parameters of an air sparging system are essential to the success of the remediation program. 

Monitoring of air sparging systems installed at different sites provided valuable information on the air sparging process, partieularly the radius or zone of influence and contaminant... 

A number of methods can be employed to monitor remedial progress, including the use of monitoring wells, groundwater analysis, and effluent vapor analysis. Selected case studies are summarized in Table 14.1 and in this section to provide information on expected contaminant removal using air sparging systems. 

Bass, D. H., and R. A. Brown. 1997. Performeuice of Air Sparging Systems—A Review of Case Studies, in Proceedings of the Fourth International Symposium on In-Situ and On-Site Bioremediation, BateUe Press, Columbus, OH, vol. 1, pp. 117—122. 

Marley, M. C., F. Li, and S. Magee. 1992b. The Application of a 3-D Model in the Design of Air Sparging Systems, in Proceedings of Focus on Eastern Ground Water Issues, pp. 377-392. 

The 50 cathode cell has overall dimensions of approximately 180 x 60 x 50 cm with a cross-sectional area for flow of c. 1530cm it has provision for an air-sparging system to improve mixing and promote turbulence within the electrolyte. A porous filter plate is built into the cell at the inlet tn order to diffuse liquid Sow through the cell to prevent localized metal accumulation on the cathodes which could Lead to short circuiting. When the foam cathodes are fully loaded, they are replaced with fresh ones. In single pass operations, the cathodes nearest the inlet require most frequent replacement. The RETEC-50 cell is primarily aimed at electroplating wastes and typically operates at 400-500 A and from -2 to -6V. 

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