Chlorinated Volatile Organic Compounds Research Articles

Contaminated site remedial investigation and feasibility removal of chlorinated volatile organic compounds from groundwater by activated carbon fiber adsorption

Groundwater contaminated by dense, non-aqueous phase liquids (DNAPLs) such as chlorinated solvents has become a serious problem in some regions of Taiwan. The sources of these contaminants are due to industrial discharges. These chlorinated volatile organic compounds (VOCs) have been proven to be carcinogenic to humans. The groundwater is used for domestic drinking water supply in some cities of Taiwan and the severely contaminated groundwater has to be treated in order to meet the requirement of drinking water standards. This study covers two areas of work. In the first part, polluted groundwater samples were collected from the contaminated site and analytical results indicated measurable concentrations of 12 representative chlorinated VOCs in water samples. The primary VOCs detected included trichloroethene (TCE), tetrachloroethene (PCE), 1,1,2-trichloroethane (1,1,2-TCA), and 1,1-dichloroethene (1,1-DCE). Second, to remove VOCs groundwater was treated using adsorption on activated carbon fiber (ACF). This involved pumping groundwater through vessels containing ACF. Most VOCs, including TCE, PCE, 1,1,2-TCA, and DCE, were readily adsorbed onto ACF and are removed from the water stream. Our study showed that the technology was able to significantly reduce chlorinated VOCs concentrations in groundwater.

Modeling of Tetrachloroethylene Degradation by Anaerobic Granular Biological Activated Carbon.

A number of different methods have been used for modeling the adsorption and biotransformation of volatile organic chlorinated compounds such as tetrachloroethylene perchloroethylene (PCE). In this study, PCE was degraded by granular biological activated carbon (GBAC) in an anaerobic Erlenmeyer flask reactor. In order to study GBAC, we performed experiments in which the efficiencies of GBAC, granular activated carbon (GAC) and anaerobic sludge for the removal of PCE were compared. In this paper, we describe how PCE was microbially biotransformed and adsorbed on GBAC. The biotransformational products were trichloroethylene (TCE) and cis-1, 2-dichloroethylene (cis-1, 2-DCE), which were adsorbed by GBAC (at solid phase). Thus, the GBAC acted not only as a microbiological carrier, but was also instrumental in adsorbing PCE and the biotransformation products. Since the adsorbed PCE was biotransformed on the GBAC, we concluded that GBAC might be effective in the treatment of PCE in synthetic wastewater. The model confirmed that the GBAC was involved in the degradation of PCE under our conditions. The model confirmed that the GBAC was instrumental in treating PCE.

Enhancement of the catalytic oxidation of hydrogen-lean chlorinated VOCs in the presence of hydrogen-supplying compounds

The complete catalytic oxidation of trichloroethylene (TCE) over alumina-supported noble metal catalysts (Pt and Pd) and in the presence of hydrogen-rich compounds, i.e. water, hexane and toluene was evaluated. Experiments were performed at conditions of lean TCE concentration (around 1000ppm) in air, between 250 and 550°C in a conventional fixed-bed reactor. Hexane and toluene were added to the feedstream in a concentration of around 1000ppm and water concentration varied from 1000 to 15000ppm. TCE oxidation occurred faster in the presence of hexane and toluene over both catalysts. Over palladium catalysts, water did not alter catalytic activity, whereas over platinum catalysts water enhanced TCE oxidation at low temperatures (<400°C) but inhibited it at higher temperatures (>400°C). Selectivity to HCl was much improved by feeding water as a hydrogen-supplying reactant; 7500ppm of water enhanced HCl outputs from 39.4 to 78.0% with Pd, and from 37.5 to 58.9% with Pt. Selectivities to C2Cl4, formed by chlorination of the feed, and Cl2 were greatly reduced. On the other hand water promoted complete oxidation of TCE to CO2, and thus reduced selectivity to CO. In the presence of hexane and toluene, formation of HCl was also enhanced. Hexane showed higher inhibition ability than toluene over both catalysts for the C2Cl4 and Cl2 formation. Unlike in the presence of water, selectivity to CO increased, as a consequence of partial oxidation of both hydrocarbons.

Results of the reactant sand-fracking pilot test and implications for the in situ remediation of chlorinated VOCs and metals in deep and fractured bedrock aquifers

Permeable reactive barriers (PRBs), such as the Waterloo Funnel and Gate System, first implemented at Canadian Forces Borden facility in 1992, are a passive remediation technology capable of controlling the migration of, and treating contaminated groundwater in situ. Most of the PRBs installed to date have been shallow installations created by backfilling sheet-pile shored excavations with iron filing reactive media. More recently continuous trenchers [R. Puls, Installation of permeable reactive barriers using continuous trenching equipment, Proceedings of the RTDF Permeable Barriers Work Group, Virginia Beach, VA, September 1997] and Caissons [J. Vogan, Caisson installation of a pilot scale, permeable reactive barrier in situ treatment zone at the Sommersworth Landfill, NH, Presented to the RTDF Permeable Barriers Work Group, Alexandria, VA, April 1996], and vertical fracturing emplacements [G. Hocking, Vertical hydraulic fracture emplacement of permeable reactive barriers, Progress Report delivered to the Permeable Reactive Barriers Workgroup of the Remedial Technology Development Forum, Beaverton, OR, April 1998] have been used to create reactive barriers in soil. None of the prior methods are capable of adequately addressing groundwater contamination in deep and fractured bedrock aquifers. The purpose of the RSF pilot study was to install reactive media into an impacted bedrock aquifer, and to evaluate the effectiveness of in situ treatment of chlorinated volatile organic compounds (CVOCs) and metals in that type of aquifer. Three discrete fractures were identified and treated and were subjected to testing before and after treatment. Between 300 and 1700 lb. of 1 mm diameter reactive proppants were injected into each zone to facilitate treatment. Monitoring data obtained from adjacent observation wells verified that fracking fluids reached at least 42 ft from the treatment well following hydrofracturing. The concentrations of many of the CVOCs decreased up to 98% based on the results of pre- and post-RSF treatment analyses. Consistent with other research, concentrations of CVOCs were noted to decrease including trichloroethene (TCE), tetrachloroethene (PCE), 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethane (1,1-DCA), and 1,1-dichloroethene (1,1-DCE) and increases were noted in concentrations of cis-1,2-dichloroethene ( cis-1,2-DCE) and chloroform suggesting that the rate of transformation of the parent compounds to these daughter products is higher than the rate of destruction of the daughter products. The RSF pilot study demonstrated that: (1) zero valent iron foam proppants have the physical and chemical properties necessary to effectively treat CVOCs and metals in groundwater when inserted under high pressures into fractured bedrock. (2) Iron foam reactive media can be placed in bedrock using high pressure hydraulic fracturing equipment and polysaccharide viscosifiers. (3) The extent of the treatment can be monitored in situ using tracers and pressure transducers. (4) Well capacity is increased by improving hydraulic conductivity through hydraulic fracturing and proppant injection. The approximate cost of all of the effort expended in the pilot study was about US$200,000. Full-scale implementations are projected to cost between US$100,000 and US$1,000,000 and would depend on site specific conditions such as the extent and level of impacted groundwater requiring treatment. This technology can potentially be implemented to create treatment zones for the passive treatment of CVOC and metal impacted groundwater in fractured rock aquifers offering a cost-effective alternative to a pump and treat forever scenario.

Aging and Structure/Activity Characteristics of CR–ZSM-5 Catalysts during Exposure to Chlorinated VOCs

This study investigates the aging and partial deactivation process for four chromium exchanged ZSM-5 catalysts during oxidative destruction of 1% vinyl chloride or trichloroethylene, each in humid (1.35% water) air at 500°C. After 51 h on stream under these harsh conditions, all catalysts are found to undergo partial loss of exchanged chromium, which correlates with the chlorine content of the chlorinated VOC (CVOC) feed molecule. Conversely, changes in catalytic activity are not entirely correlated with residual chromium levels in the zeolite, suggesting that the chromium cation location is also important. A deactivation pathway is proposed involving slow generation of volatile CrO2Cl2 to explain the process of cation migration and loss. These results are utilized to derive relationships between catalyst structure (cation site locations, accessibilities, and framework bond strengths) and catalytic properties (activity, selectivity, and site stability). The analysis shows that Cr cations, which are closely associated with a maximum number of zeolite framework oxygen atoms, are most resistant to migration or loss from the catalyst during CVOC oxidation. Chromium sites (SII, SIII) within the straight channels or near channel intersections are found to be most active, but are also most prone to migration and/or loss. This enhanced activity is believed to occur because of the high accessibility of SII and SIII sites to incoming CVOC molecules. Rapid loss of chromium from these sites is believed to be due to their weak association with the zeolite framework. Conversely, chromium sites (SI, SIV) located in the sinusoidal channels are determined to be less active, but more persistent during deactivation because of their increased coordination with zeolite framework atoms and reduced accessibility to incoming CVOC molecules.

MCM-48 supported chromium catalyst for trichloroethylene oxidation

MCM-48 supported chromium (Cr/MCM-48) catalyst was prepared by introduction of chromium chloride during gel-preparation for the hydrothermal synthesis of MCM-48. Based on the N 2 adsorption/desorption isotherm, BET, pore size distribution, XRD, FTIR, TGA, and DTA data, Cr/MCM-48 was found to have high surface area (∼832 m 2/g), uniform pore size distribution (∼24 Å), mesoporous structures similar to MCM-48 itself, and incorporation of about 3 wt% of Cr component in the mesoporous framework. Cr/MCM-48 was very active for the oxidative destruction of trichloroethylene (TCE), which is a typical chlorinated volatile organic compound (CVOC); 100% conversion of TCE was achieved at 350°C. Based on the TGA of trichloroethylene/water adsorption study, it was found that MCM-48 had high adsorption capacity (>0.25 g TCE/g catalyst). In addition, the hydrophobicity of the adsorptive properties of Cr/MCM-48 materials could be modified. The high adsorption capacity and catalytic activity of Cr/MCM-48 material make it suitable for adsorption/catalysis bifunctional systems for energy-saving treatment of low concentration of VOC or CVOC.

揮発性有機塩素化合物の加熱酸化分解処理

Tests were carried out on a heater-type, oxidation-decomposition system to study whether this system could achieve complete decomposition of volatile chlorinated organic compounds (TCE, PCE), major contaminants of groundwater and soil. Test results revealed a decomposition characteristic that there is less residual TCE/PCE (higher decomposition percentage) with greater inflow load, longer retention time, and higher temperature of the reactor used. This system was capable of about 100% decomposition of TCE into CO2 and HCI, when the temperature of the reactor was 950°C, the retention time was over 8.0 seconds, and the TCE concentration was over 3%. Under these conditions, it was possible to carry out stable continuous treatment. CCl4, PCE, CHCl3 were detected below the limited value as by-products and there was no forming of Dioxins under these conditions. Tests which involved the treatment of a gas which contained both TCE and PCE revealed a TCE decomposition of approximately 100%, and a PCE decomposition of below the limited value, when the reactor temperature was 950°C, the retention time was over 8.0 seconds, and the TCE and PCE concentrations were over 3% and 0.3%, respectively. This system has the efficiency of more than two times that of a UV system.

Field Evaluation of High Voltage Electron Beam Technology for Treating VOC-Contaminated Groundwater. Part I: VOC Removals and Treatment Costs

AbstractAs part of the Superfund Innovative Technology Evaluation program, the U.S. Environmental Protection Agency evaluated the High Voltage Environmental Applications, Inc. (HVEA), electron beam (E-beam) technology at the U.S. Department of Energy Savannah River Site (SRS) in Aiken, South Carolina. This technology irradiates water with a beam of high-energy electrons, causing the formation of three primary transient reactive species: aqueous electrons, hydroxyl radicals, and hydrogen radicals. Target organic compounds are either mineralized or broken down into low molecular weight organic compounds, primarily by these species. The E-beam system used for the evaluation is housed in an 8- by 48-foot trailer and is rated for a maximum flow rate of 50 gpm. During two different periods totaling 3 weeks in September and November 1994, about 70,000 gallons of SRS M-area groundwater contaminated with volatile organic compounds (VOCs) was treated with the E-beam system. The highest removal efficiencies (REs) observed for unsaturated chlorinated VOCs in groundwater - trichloroethene (TCE), tetrachloroethene (PCE), and cis-1,2-dichloroethene (1,2-DCE) - were &gt;99, 99, and &gt; 91%, respectively. REs ranged from 68 to &gt; 98% for 1,1,1-trichloroethane (1,1,1-TCA), 1,2-dichloroethane (1,2-DCA), chloroform, and carbon tetrachloride (CCl

Determination of Organic Parameters in Waste and Leachates From the Hazardous Waste Landfill of Raindorf; Germany

Extensive investigations of leachates and solid waste samples for organic sum parameters and environmentally relevant organic compounds were carried out at the hazardous waste landfill of Raindorf, which is operated in accordance with German Technical Instructions on Waste (TI Waste). The measurements showed that the majority of the waste samples contained only minor amounts of phenols, highly volatile chlorinated organic compounds (VCHC), benzene, toluene, ethylbenzene and xylene (BTEX), polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH). The concentrations ranged from less than 100 μg/kg-1 up to 1000 μg/kg-1 of dry substance. Only hydrocarbons were detected in higher concentrations (mg to g kg-1 of dry substance). In most leachate and gas samples taken at the landfill, the concentrations of the abovementioned parameters were close to or even below the detection limit. The measurement of organic single compounds underlined the usefulness of the sum parameters, adsorbable organic halogen compounds and phenol index, for the estimation of the total amount of these substances. A comparison of organic sum parameter concentrations measured in leachates from landfills of differing ages indicates that the application of TI Waste leads to a reduction of the organic load in the leachate. © 1996 ISWA

Combined sorbent/catalyst media for destruction of halogenated VOCs

Several chromium modified zeolites have been developed and tested for their ability to physisorb chlorinated VOCs (CVOCs) at ambient and then catalytically destroy them at elevated temperatures (ca. 300°C). These dual function materials, which act as both sorbents and catalysts, are believed to be the key to implementing a new energy efficient process for the destruction of low concentration level CVOC streams. Data showing catalytic activity, sorptivity and other physical properties for Y and ZSM-5 zeolites based media are presented. A chromium exchanged ZSM-5 (Cr-ZSM-5) medium which showed superior performance catalytically (> 95% TCE and MeCl2 destruction at 300°C) and adequate sorption capacity (0.074 g TCE/g sorbent, 0.064 g MeCl2/g sorbent at 23°C in the presence of humid air) was chosen for subsequent dual function tests. These tests showed that ambient temperature fixed bed sorption of CVOCs followed by periodic heating of the upper portion of the bed to catalytic temperatures (ca. 35°C) with slow temperature ramping of the lower portion to desorb trapped CVOCs, produced a highly energy efficient cyclic process for their destruction. A Cr-ZSM-5 bed, which alternately stored and then destroyed CVOC from a humid 110 ppm TCE stream at a space velocity of 2400 h−1, was shown to operate over a 1460 min cycle which required heating for only 7% of the time.

Gas phase photocatalytic degradation on TIO2 pellets of volatile chlorinated organic compounds from a soil vapor extraction well

Abstract The degradation of trichloroethylene (TCE, Cl2C=CHCl) and tetrachloroethylene (PCE, Cl2C=CCI2) in a gas stream from a soil vapor extraction (SVE) well was demonstrated with an annular photocatalytic reactor packed with porous TiO2 pellets in a field trial at the Savannah River Site in Aiken, SC. The TiO2 pellets were prepared using a sol‐gel method. The experiments were performed at 55 to 60°C using space times of 108 to 1010 g • s • mol‐1 for TCE and PCE. Chloroform (CHCl3) and carbon tetrachloride (CCl4) were detected as minor products from side reactions. On a molar basis, the amounts CCl4 and CHCl3 produced were about 2 and 0.2% of the reactants, respectively.

U.S. Environmental Protection Agency’s Super-fund Innovative Technology Evaluation of Pneumatic Fracturing ExtractionSM

The U.S. Environmental Protection Agency (EPA), in cooperation with Accutech Remedial Systems (ARS) and the New Jersey Institute of Technology (NJIT), performed a field demonstration of Pneumatic Fracturing Extraction (PFE)SM for the removal of chlorinated-volatile organic compounds (VOCs) from vadose zones of low permeability. The demonstration was conducted in the fall of 1992 at an industrial park in Somerville, New Jersey, where removal of VOC contamination in shale bedrock was required to comply with New Jersey’s Environmental Cleanup Responsibility Act (ECRA). During the demonstration, airflow and contaminant concentrations were monitored to establish a database against which the developer’s claims about the technology were evaluated. The developer contended that PFE would increase extracted airfkiw rates from the subsurface formation by at least 100 percent and would increase the mass removal rate for the key contaminant, trichloroethene (TCE), by at least 50 percent. Also, during the demonstration...

Contribution of an industrial waste incinerator to the atmospheric concentrations of volatile chlorinated organic compounds

The contribution of five volatile chlorinated organic compounds emitted from waste incinerator to the surrounding atmosphere were investigated. The atmospheric concentrations of these compounds were low level as compared with those around the factories in which chlorinated organic compounds were used as solvent. It was found that the influence of the incinerator exhausts to the atmosphere was negligible or very small for these compounds.

Emission of organic compounds by combustion of waste plastics involving vinyl chloride polymer

Organic compounds emitted from combustion of waste plastics involving vinyl chloride polymer were investigated in an actual waste incinerator. The amounts of volatile aliphatic hydrocarbons and volatile chlorinated organic compounds decreased when the secondary combustion temperature was controlled over 900°C. On the other hand, the amounts of some aromatic hydrocarbons increased with a rise of the secondary combustion temperature.

Simultaneous Determination of Residual Chlorine and Volatile Chlorinated Organic Compounds in Vegetables by the Head Space Method

In order to elucidate the mechanism of formation of volatile chlorinated organic compounds (VCOC) from vegetables treated with sodium hypochlorite, simultaneous determination of residual chlorine and VCOC was studied. A sample was added to a head space analysis vessel filled in advance with phosphate buffer (pH 7.0) and potassium cyanide, then the vessel was sealed and allowed to stand for 30 minutes. The obtained gas was subjected to ECD-GC for determination. The substance formed in soybean sprouts immersed in sodium hypochlorite solution (200ppm) was identified as chloroform by GC/MS. Residual chlorine and chloroform were detected in the sprouts at levels of 12.1μg/g and 114ng/g respectively. The analysis of 66 samples of commercially available vegetables with the present method revealed residual chlorine ranging from 0.14 to 3.7μg/g and chloroform from 15 to 241ng/g in four samples of soybean sprouts, etc.

Emission of volatile chlorinated organic compounds by combustion of waste organochlorine material

Many volatile organochlorine compounds are formed by combustion of waste organochlorine materials and emitted mostly in exhaust gas. Dichloromethane and trichloroethylene in fuel or waste solvent were completely decomposed by combustion, but decomposition yield in case of waste liquid composed of large volume of water depended on combustion temperature.

Sampling and Analysis Experiments for Improved Characterization of Products of Incomplete Combustion

Laboratory and field experiments were conducted to evaluate the volatile organic sampling train (VOST) methodology for the sampling and analysis of products of incomplete combustion (PICs). A pilot-scale incinerator was used to incinerate several volatile chlorinated organic compounds which were known to produce PICs. Approximately 300 ppm of 1,2-dichloroethane, 1,1,1-trichloroethane, and trichloroethene were individually incinerated at 700°C. Standard VOST sampling apparatus was used to collect samples for determinations of precision and for distributive volume-studies. A series of experiments was conducted to establish whether PICs were being formed at concentration levels which could be measured by the VOST methodology. Samples were collected at 1 L/ min for 20 min with standard pairs of Tenax-Tenax/charcoal cartridges. The major PICs found were vinyl chloride from 1,2-dichloroethane, 1,1-dlchloroethene from 1,1,1-trichloroethane, and carbon tetrachloride from trichloroethene. Chloromethane was also formed at significant levels for all of the compounds incinerated. Additional field samples that were collected and analyzed showed that the precision of the PIC generation was fairly constant. Use of a wide-bore (0.53 mm) capillary column, to improve chromatographic resolution, was also evaluated. This modification was used to enhance the gas chromatography/mass spectrometry performance and allow improved identification of compounds in the field samples. An Environmental Protection Agency audit cylinder containing compounds at approximately 5 ppb was also sampled and analyzed. Results showed these procedures incorporating VOST methodology were accurate and precise.

土壌汚染 土壌中の揮発性有機塩素化合物の挙動

土壌汚染 土壌中の揮発性有機塩素化合物の挙動

Advances in the determination of volatile organic solvents and other organic pollutants by gas chromatography with thermal desorption sampling and injection

The problem of the separation of 34 volatile organic chlorinated compounds is solved by using three different GC columns selected according to the needs of the particular separation required. The effect of water vapor contained as moisture in the trapped air on the retention of some characteristic compounds is studied. The influence of dead volumes on trap injection is also studied.

芳香族炭化水素の塩素化反応による低沸点有機塩素化合物の生成

浄水処理過程で生成するトリハロメタンについての研究は数多くなされており, 生成前駆物質の構造及び性状も解明されている。しかしながら, トリハロメタン以外の低沸点有機塩素化合物の生成前駆物質については, ほとんど知られていない。そのため本研究ではフミン酸の構成因子である芳香族炭化水素の6種類をモデル物質として選び, それらの生成能について検討した。その結果, これらの6化合物はCCl4, CHClCCl2, CCl2CCl2, CHCl3の生成前駆物質であることを示し, 生成能の検討において, pHが酸性側でそれらの生成能が増大する特徴が認められた。また, モデル物質の水溶液をオゾン処理した場合と, オゾン未処理の場合を比較すると, 各低沸点有機塩素化合物の生成能は, 増加するものと, 減少するものがあり, これら生成前駆物質の分子構造に依存することが考えられた。