Volatile organic compounds : VOC concentrations

Carbon adsorption with regeneration may be a better treatment option when the volatile organic compound (VOC) concentration is less than 100 ppm. High levels of very permeable gases, such as carbon dioxide, may reduce the system s efficiency. 

Steam regeneration is most commonly applied to activated carbon that has been used in the removal and/or recovery of solvents from gases. At volatile organic compound (VOC) concentration levels from 500 to 15,000 ppm, recovery of the VOC from the stream used for regeneration is economically justified. Below about 500 ppm, recovery is not economically justifiable, but environmental concerns often dictate adsorption followed by destruction. While activated carbon is also used to remove similar chemicals from water and wastewater, regeneration by steam is not usual. The reason is that the water-treatment carbon contains 1 to 5 kg of water per kg of adsorbent that must be removed by drying before regeneration or an excessive amount of superheated steam will be needed. In water treatment. 

The removal of volatile organic compounds (VOC) from air is most often accompHshed by TSA. Air streams needing treatment can be found in most chemical and manufacturing plants, especially those using solvents. At concentrations from 500 to 15,000 ppm, recovery of the VOC from steam used to regenerate activated carbon adsorbent thermally is economically justified. Concentrations above 15,000 ppm ate typically in the explosive range and... 

Volatile Organic Compounds (VOCs) VOCs are a class of gaseous pollutants containing carbon. The indoor air typically contains dozens of VOCs at concentrations that are measurable. 

The formation of ethylcellulose nanoemulsions by a low-energy method for nanoparticle preparation was reported recently. The nanoemulsions were obtained in a water-polyoxyethylene 4 sorbitan monolaurate-ethylcellulose solution system by the PIC method at 25 °C [54]. The solvent chosen for the preparation of the ethylcellulose solution was ethyl acetate, which is classed as a solvent with low toxic potential (Class 3) by ICH Guidelines [78]. Oil/water (O/W) nanoemulsions were formed at oil/ surfactant (O/S) ratios between 30 70 and 70 30 and water contents above 40 wt% (Figure 6.1). Compared with other nanoemulsions prepared by the same method, the O/S ratios at which they are formed are high, that is, the amount of surfactant needed for nanoemulsion preparation is rather low [14]. For further studies, compositions with volatile organic compound (VOC) contents below 7 wt% and surfactant concentrations between 3 and 5 wt% were chosen, that is, nanoemulsions with a constant water content of 90% and O/S ratios from 50 50 to 70 30. 

SWITGTHERM A catalytic process for oxidizing volatile organic compounds (VOCs). It involves regenerative heat exchange, which permits autothermal operation at VOC concentrations in the range 250 to 650 ppm. Developed in Poland and now used in over 100 installations there. 

Fellin P, Otson R. 1994. Assessment of the influence of climatic factors on concentration levels of volatile organic compounds (VOCs) in Canadian homes. Atmos Environ 28(22) 3581-3586. 

Begerow J, Jermann E, Keles T, et al. 1995. Passive sampling for volatile organic compounds VOCs in air at environmentally relevant concentration levels. Fresenius Journal of Analytical Chemistry 351(6) 549-554. 

Monitoring data have not shown cresols to be widely occurring atmospheric pollutants. The National Ambient Volatile Organic Compounds (VOCs) Database, a compilation of published and unpublished air monitoring data from 1970 to 1987, contained very little information on the cresols (Shah and Heyerdahl 1989). The database contained only information for o-cresol in source-dominated atmospheres (air surrounding a facility or known release of the chemical in question). The median air concentration of o-cresol at source-dominated sites is 0.359 ppb for 32 samples (Shah and Heyerdahl 1989). 

Catalytic oxidation is capable of treating contaminant concentrations ranging from 1 part per million (ppm) to 20,000 ppm. Typically, it is applied to streams containing about 3000 ppm per volume or less of volatile organic compounds (VOCs). At levels approaching 3000 ppm per volume VOCs, the recoverable heat from the process may be sufficient to sustain oxidation without additional fuel. 

Reclaim is a passive, in situ technology that uses a hydrophobic porous polymer to attract, adsorb, and concentrate petroleum hydrocarbons and volatile organic compounds (VOCs) from soils and/or groundwater. Reclaim is considered a passive treatment technology because it requires no mechanical equipment remediation consists of placing polymer-filled canisters in recovery wells and allowing the containers to attract and adsorb organic contaminants. Reclaim canisters are then recycled and contaminants recovered for analysis and/or disposal. This polymer extracts contaminants whether they are in liquid phase, vapor phase or dissolved phase in water. 

EnviroSep, Inc. (EnviroSep), has developed a thick-film absorption technology for the removal of volatile organic compounds (VOCs) from water. The technology uses a proprietary form of silicone rubber to absorb contaminants. The vendor claims the technology is effective for VOCs with less than 2% solubility in water and a boiling point of less than 200°C for the pure compound and is most efficient for use at sites with contaminant concentrations between 10 parts per million (ppm) and 2000 ppm. The technology is intended for aqueous waste streams. 

Potential applications for this technology include the treatment of airstreams contaminated with volatile organic compounds (VOCs) from air stripping, soil vapor extraction, industrial air emissions, and for the cleaning of air in closed environments. PCO is best suited for waste streams with low concentrations of contaminants, and with low to medium flow rates. The AIR-11 process can operate consistently in conditions where flow rates and VOC concentrations are highly variable, even intermittent. 

Photocatalytic oxidation (PCO) is a destructive process for the treatment of gas-phase waste streams that can operate successfully at low concentrations of contaminants and at a low energy cost. In this technology, ultraviolet (UV) light illuminates a titanium dioxide catalytic surface at room temperatures and produces hydroxyl radicals, which destroy volatile organic compounds (VOC s). 

This system is designed to treat volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) at very high concentrations, which traditional nonvacuum air stripping... 

High concentrations of volatile organic compounds (VOCs) can be poisonous to bacteria. At sites with high concentrations, in situ air stripping should be used to reduce the VOC concentrations before attempting in situ bioremediation. Site evaluation should include as assessment of the levels of nutrients in the soil to determine whether an additional carbon source or oxidizing agent is needed. 

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