Stripped contaminants

Cost of an air stripping system is site specific and contaminant specific. In 1991, the cost of air stripping contaminants with a Henry s law coefficient from 0.1 to 10 was estimated to range from 0.07 per 1000 gal of water treated to 0.70 per 1000 gal of water treated (packed-tower system). As the Henry s law coefficient was decreased to 0.005, costs rapidly rose to 7.00 per 1000 gal of water treated (D164241, p. 7). 

Concentrating methods, such as solvent extraction for copper and carbon absorption for gold, will selectively strip just the metal of interest. Loaded solvents and carbon columns are stripped of their metal value in a concentrated solution that can now be electrowon to recover the metal value. The spent electrolytic solutions stripped of the copper or gold can be recycled back to recover more metal value from the solvents or carbon. Some contaminant metals may also pass through this process and continually build up in the electrolyte. For these operations, the solutions can be diluted into the original leach solutions as make up lixiviant, or a process similar to the one just described can be used to strip contaminant metals from the electrolytes. 

Exterior windows with movable sashes are not recommended in laboratories. Wind blowing through the windows and high-velocity vortices caused when doors open can strip contaminants out of the fume hoods and interfere with laboratory static pressure controls. 

If sulfur is a contaminant, its content can be measured, but it may suffice to characterize its effects by the copper strip corrosion test, or by the doctor test". 

Deeper contamination may be remedied with bioventing, where air is injected through some wells, and extracted through others to both strip volatiles and provide oxygen to indigenous organisms. Fertilizer nutrients may also be added. This is usually only a viable option with lighter refined products. 

Steps. Thermal-swing cycles have at least two steps, adsorption and heating. A cooling step is also normally used after the heating step. A portion of the feed or product stream can be utilized for heating, or an independent fluid can be used. Easily condensable contaminants may be regenerated with noncondensable gases and recovered by condensation. Water-iminiscible solvents are stripped with steam, which may be condensed and separated from the solvent by decantation. Fuel and/or air may be used when the impurities are to be burned or incinerated. 

Process condensate from reforming operations is commonly treated by steam stripping. The stripper is operated at a sufficiently high pressure to allow the overhead stripping steam to be used as part of the reformer steam requirement (71). Contaminants removed from the process condensate are reformed to extinction, so disposal to the environment is thereby avoided. This system not only reduces atmospheric emissions, but contributes to the overall efficiency of the process by recovering condensate suitable for boiler feedwater make-up because the process is a net water consumer. 

EPA has also developed pretreatment standards for industrial faciHties that discharge directiy to pubHcly owned treatment works (POTWs). The three types of pollutants of principal concern are pollutants that interfere with the operation of the POTW, pollutants that contaminate the sludges produced in the POTW, and pollutants that pass through the POTW or that are otherwise incompatible. One particular concern is volatile contaminants that can be stripped into the air during conventional wastewater treatment and become air pollution problems. These pretreatment standards are included in the effluent guidelines for the different industries. 

Expect some product contamination if feed components can react with water, eg, ester will be partially hydrolyzed to acid and alcohol fate of reaction product species depends on above rules, eg, methanol from methyl ester hydrolysis probably not stripped out of bottoms stream. 

Zinc Costing of Ca.pa.citors, In the zinc coating of paper strip for capacitors, the paper strip is fed from air through locks into a vacuum environment. There, it is coated by thermally evaporated zinc. The rate of evaporation is so high that contamination of the zinc vapor is excluded. The paper is fed at the maximum rate permitted by its own strength. 

In Situ Air Stripping. An innovation to conventional pump and treat air stripping is in situ air stripping. Two horizontal wells are installed, one below the water table and one in the vadose zone. Air is injected in the lower well while contaminated soil vapor is extracted by vacuum through the upper well. 

Volatile organic contaminants occur primarily in groundwaters as a result of the disposal of industrial solvents on the ground or in soakage pits. The removal of these compounds has best been accompHshed by the use of air stripping or adsorption on activated carbon. 

Unreacted phosgene is removed from the cmde chloroformates by vacuum stripping or gas purging. Chloroformates of lower primary alcohols are distillable however, heavy-metal contamination should be avoided. As stated earlier, chloroformates generating a stable carbonium ion on decomposition, ie, secondary or tertiary chloroformates or henzylic chloroformates, are especially unstable in the presence of heavy metals and more specifically Lewis acids and, hence, should be distilled at as low a temperature and high vacuum as possible. 

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