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Title: Cascade air-stripping system for removal of low and semi-volatile organic contaminants

Abstract

Many hazardous waste sites have been known to have groundwaters contaminated with low volatile, hazardous compounds such as bromoform 1,1,2,2-tetrachloroethane, 1,2-dibromo-3-chloropropane (DBCP), napthalene, and polychlorinated biphenyls (PCBs). In addition, a large number of public water supplies have been reported to have taste and odor problems in drinking water, which are attributed primarily to naturally occurring compounds, such as 2-methylisoborneol (MIB), geosmin, etc. These classes of compounds have very low Henry's Constant, H{sub c}, in the range of 1 to 50 atm. Air-stripping in countercurrent packed towers is a well accepted treatment process for removing volatile organic chemicals (VOCs) from water. The USEPA has identified packed countercurrent air-stripping as not only the least-cost, but also one of the best available technologies for the removal of VOCs. However, the economic viability of this process is limited to volatile compounds of H{sub c} value greater than SO atm. A novel modification of the conventional countercurrent air-stripping process, introduced as cascade air-stripping was proposed for cost effective removal of these classes of compounds from water and at hazardous waste spill-sites. The main objectives of this study were to demonstrate the concept of cascade air-stripping; to compare cascade air-stripping with conventional air-stripping under identical conditions;more » and to verify the hypothesis that the cascade system is superior to the conventional system at the pilot and prototype scales. Results of the pilot and prototype study showed that the cascade airstrip ping system was a viable and economical approach to remove low and semi-volatile organic compounds from water. The cascade system consistently showed higher removals than the conventional system for both pilot and prototype scale study.« less

Authors:
Publication Date:
Research Org.:
Drexel Univ., Philadelphia, PA (United States)
OSTI Identifier:
5478442
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; CHLORINATED ALIPHATIC HYDROCARBONS; MATERIALS RECOVERY; CHLORINATED AROMATIC HYDROCARBONS; GROUND WATER; DECONTAMINATION; NAPHTHALENE; VOLATILE MATTER; WATER POLLUTION; AROMATICS; CLEANING; CONDENSED AROMATICS; HALOGENATED ALIPHATIC HYDROCARBONS; HALOGENATED AROMATIC HYDROCARBONS; HYDROCARBONS; HYDROGEN COMPOUNDS; MANAGEMENT; MATTER; ORGANIC CHLORINE COMPOUNDS; ORGANIC COMPOUNDS; ORGANIC HALOGEN COMPOUNDS; OXYGEN COMPOUNDS; POLLUTION; PROCESSING; RECOVERY; WASTE MANAGEMENT; WASTE PROCESSING; WATER 540320* -- Environment, Aquatic-- Chemicals Monitoring & Transport-- (1990-)

Citation Formats

Jang, Won. Cascade air-stripping system for removal of low and semi-volatile organic contaminants. United States: N. p., 1989. Web.
Jang, Won. Cascade air-stripping system for removal of low and semi-volatile organic contaminants. United States.
Jang, Won. 1989. "Cascade air-stripping system for removal of low and semi-volatile organic contaminants". United States. doi:.
@article{osti_5478442,
title = {Cascade air-stripping system for removal of low and semi-volatile organic contaminants},
author = {Jang, Won.},
abstractNote = {Many hazardous waste sites have been known to have groundwaters contaminated with low volatile, hazardous compounds such as bromoform 1,1,2,2-tetrachloroethane, 1,2-dibromo-3-chloropropane (DBCP), napthalene, and polychlorinated biphenyls (PCBs). In addition, a large number of public water supplies have been reported to have taste and odor problems in drinking water, which are attributed primarily to naturally occurring compounds, such as 2-methylisoborneol (MIB), geosmin, etc. These classes of compounds have very low Henry's Constant, H{sub c}, in the range of 1 to 50 atm. Air-stripping in countercurrent packed towers is a well accepted treatment process for removing volatile organic chemicals (VOCs) from water. The USEPA has identified packed countercurrent air-stripping as not only the least-cost, but also one of the best available technologies for the removal of VOCs. However, the economic viability of this process is limited to volatile compounds of H{sub c} value greater than SO atm. A novel modification of the conventional countercurrent air-stripping process, introduced as cascade air-stripping was proposed for cost effective removal of these classes of compounds from water and at hazardous waste spill-sites. The main objectives of this study were to demonstrate the concept of cascade air-stripping; to compare cascade air-stripping with conventional air-stripping under identical conditions; and to verify the hypothesis that the cascade system is superior to the conventional system at the pilot and prototype scales. Results of the pilot and prototype study showed that the cascade airstrip ping system was a viable and economical approach to remove low and semi-volatile organic compounds from water. The cascade system consistently showed higher removals than the conventional system for both pilot and prototype scale study.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1989,
month = 1
}

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  • This study was conducted to evaluate the feasibility of using rotating disk contactor (RDC) to strip VOCs from the contaminated water. Five VOCs, trichloroethylene, tetrachloroethylene, ethylbenzene, chloroform, and 1,1,1-trichloroethane, were used under either batch or continuous operation. Based on several oxygen transfer models proposed in the literature, a semi-empirical model has been developed in this study. The mass transfers of the compounds studied were found to be a function of disk rotational speed, depth of immersion, flow rate, specific contact areas of the bulk water surface and the exposed disk surface. For a given depth of immersion, mass transfer ratemore » is proportional to the speed to a power of approximately 1.45. At a constant speed, the mass transfer coefficient decreases with decreasing depth of immersion. Under similar operating conditions, the mass transfer of VOCs is proportional to 55% of that of oxygen. Experimental data show that the rate of mass transfer of VOCs depends on the solute's diffusivity to a power approximately equal to 0.5 which is independent of the speed and other operating conditions. However, the gas-phase resistance has greater influence on the removal of less volatile components at low rotational speeds. The energy consumption and its application for the removal of VOCs are also discussed in comparison to that of the packed tower aeration.« less
  • The performance of a centrifugal vapor-liquid contactor equipped with high specific surface area packing (>2,000 m{sup 2}/m{sup 3}) was evaluated for air stripping of jet fuel components from groundwater. Hydraulic test data indicated that the Sherwood flooding correlation which has been proposed for use in designing centrifugal vapor-liquid contactors overestimates the rotational speeds at which flooding occurs. For the mass transfer performance, a concept of area of a transfer unit (ATU) was introduced to account for the change in fluid loading with radius of the packing torus. The ATU was found to be a strong function of the specific surfacemore » area of the packing and to a lesser extent a function of rotor speed and liquid flow rate. A correlation based on the specific surface area of the packing is proposed for predicting the ATU. A simple empirical model is also proposed for determining the power consumed in turning the packing torus at various operating conditions. Previous claims in the literature that centrifugal vapor-liquid contactor is resistant to fouling because of high shear force were found not to be valid for groundwater with high iron content.« less
  • Soil venting offers promise as a method for recovering volatile contaminants from unsaturated soil. This technique involves the withdrawal of air from a field of dry wells to recover pollutant vapors. Field-scale venting applications have successfully recovered large quantities of volatile organics from contaminated soil. However, attempts to document recovery rates and final concentrations in pilot studies have met with limited success, and previous laboratory studies have been restricted to artificial or modified soil. Aromatic hydrocarbons were removed from these artificially contaminated soils through abiotic volatilization induced by airflow. Recovery rates and total mass removed were confirmed with a closedmore » mass balance at the end of each trial. Undisturbed, natural soils were studied to indicate the behavior expected from inhomogeneous, anisotropic, structured media in the field. These studies were carried out on fine sand and silt loam. Responses of recovery rates to moisture content, airflow rates, and initial dosages were recorded. An initial period of quasi-equilibrium vapor yield was found to correspond with residual solvent concentrations greater than 5,000 or 8,000{mu}g 9{sup {minus}1} on Weswood fine sand and Weswood silt loam, respectively. This period of recovery is called phase 1, and is followed by a transition to a period of low vapor yield, called phase 2. The phase 2 loss rates were found to be considerably lower than predicted by an equilibrium-based model devised by Roy and Griffin (1989). An empirical model which relates loss rate to residual concentration is presented. This model can be applied to soils similar in structure and texture to those investigated in this study. Furthermore, this procedure can be applied to a wide range of soils and pollutants by generating two coefficients with a similar, short-term air stripping study.« less
  • SPECIATE presents Volatile Organic Compound (VOC) and Particulate Matter (PM) species profiles for more than 400 source categories. The species profiles consist of weight percentages of individual compounds of total VOC and total PM. Speciation factors are used to estimate emissions of air toxics from emission factors or estimates of total VOC's and PM. Speciated emission factors are also presented in the data base.
  • SPECIATE presents Volatile Organic Compound (VOC) and Particulate Matter (PM) species profiles for more than 400 source categories. The species profiles consist of weight percentages of individual compounds of total VOC and total PM. Speciation factors are used to estimate emissions of air toxics from emission factors or estimates of total VOC's and PM. Speciated emission factors are also presented in the data base.