Volatile contaminants

Gc/ftir has both industrial and environmental appHcations. The flavor and aroma components in fragrances, flavorings, and foodstuffs can be identified and quantified via gc/ftir (see Food additives). Volatile contaminants in air, water, and soil can be analy2ed. Those in air are usually trapped in a sorption tube then injected into the chromatograph. Those in water or soil are sparged, extracted, or thermally desorbed, then trapped and injected (63,64). 

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. 

A U.S. EPA study (41) showed that soil vapor extraction (SVE) is an effective treatment for removing volatile contaminants from the vadose zone. Sandy soils are more effectively treated than clay or soils with higher organic content because higher air flows are possible in sand and clays—organic soils tend to adsorb or retain more contaminants. Removal of volatiles is rapid in the initial phase of treatment and thereafter decreases rapidly thereafter-an important consideration in the design of air emissions control over the life of the project. 

Isopiestic or isothermal distillation. This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace metal studies. The procedure involves placing two beakers, one of distilled water and the other of a solution of the material to be purified, in a desiccator. The desiccator is sealed and left to stand at room temperature for several days. The volatile components distribute themselves between the two beakers whereas the non-volatile contaminants remain in the original beaker. This technique has afforded metal-free pure solutions of ammonia, hydrochloric acid and hydrogen fluoride. 

Where FW contains bicarbonate or carbonate alkalinity (as calcium, magnesium, or sodium salts), these salts undergo thermal decomposition in the boiler, and the steam-volatile contaminant gas carbon dioxide is introduced into the steam distribution system, as shown ... 

Pirrone N, Hedgecock 1, Forlano L. 2000. The role of the ambient aerosol in the atmospheric processing of semi-volatile contaminants a parameterised numerical model (CASPAR). J Geophys Res 105(D8) 9773-9790. 

Volatilization of the dissolved volatile contaminants through the air-water interface... 

Volatilization or transportation of volatile contaminants from the plants to the air (phytovolatilization)... 

Soil vapor extraction (SVE) can be used to remove volatile contaminants and, when combined with another technology, to treat nonvolatile contaminants. If contamination has reached the aquifer, it is necessary to use SVE in combination with groundwater pumping and air stripping. 

In some configurations, the vacuum used in MPE increases the effective drawdown of ground-water (i.e., the increase or lowering of the depth of the groundwater table) locally near the pumped well. This has the effect of increasing exposed soil in the saturated zone and the removal of volatile contaminants located above and below the original water table. 

Kavanaugh, M.C., Trussell, R.R. (1980) Design of aeration towers to strip volatile contaminants from drinking water. J. Am. Water Works Assoc. 72, 684-692. 

Air sparging Injects air below the water table and captures it above the water table to extract volatile contaminants and promote biodegradation Can be inefficient in low-permeability zones and complex geologic settings Typically limited to depths less than 30 ft Multicomponent mixtures can adversely affect extractability... 

Yuan, D., Schuring, J. R., and Chan, P. C., 1999, Volatile Contaminant Extraction Enhanced by Pneumatic Fracturing Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management, April, pp. 69-76. 

In general chloroaromatic hydrocarbons decompose faster than the more hydrophilic compounds such as phenols. The destruction of these two kinds of pollutants occurs at different sites in or around the cavitation bubble and follows different pathways. The difference becomes even more pronounced when more volatile contaminants are used. 

Little information on the levels of 1,4-dichlorobenzene concentrations in infant and toddler foods and in baby formula was located. Page and Lacroix (1995) analyzed a variety of beverage and food samples for 32 different volatile contaminants, including 1,4-dichlorobenzene and found residue levels to be quite low (range, 0.1-22 ppb). Soft drink samples contained 0.1 g/kg (ppb), while cream with 10% butterfat, butter, margarine, peanut butter, flour, and pastry mix contained concentrations of 0.1 ppb, 1.3-2.7 ppb, 12.2-14.5 ppb, 1.2-8.8 ppb, 7.3 ppb, and 22 ppb, respectively. No information was located to determine whether children differed in their weight-adjusted intake of 1,4-dichlorobenzene. 

Page DB, Lacroix GM. 1995. On-line distillation/purge and trap analysis of halogenated, nonpolar, volatile contaminants in foods. J AOAC Int 78(6) 1416-1428. 

Because airborne and volatile contaminants can present a significant threat to industrial workers health and safety, identification and quantification of these airbome and volatile contaminants through air/soil monitoring is an essential component of a health and safety program at an industrial site having hazardous substances. The purpose of air and soil monitoring is to identify and quantify airbome and volatile hazardous contaminants in order to determine the level of plant worker s protection needed. 

In general, there are two principal approaches available for identifying and/or quantifying airbome contaminants as well as volatile contaminants in soil ... 

The first approach onsite use of direct-reading instruments as initial quahtative identification or screening (note the airborne/volatile contaminant, or the class to which it belongs, is demonstrated to be present but quantitative determination of its exact concentration must await subsequent testing) and... 

E rovides for complete site cleanup by addressing less volatile contaminants as well as volatile organic compounds (VOCs)... 

RPT technologies are designed to operate in the gas phase and may not be applicable for direct treatment of liquid or solid wastes. However, technologies snch as air stripping could be used to volatilize contaminants from soil or groundwater prior to treatment. The technology cannot treat contaminants such as metals. 

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. 

Vaportech enhanced volatilization is designed to remove volatile contaminants from vadose zone soils in situ. The technology operates by injecting clean air around the perimeter of the contaminated area and withdrawing contaminated air from the middle. 

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