Tetrachloroethene, PCE

Okeke BC, YC Chang, M Hatsu, T Suzuki, K Takamizawa (2001) Purification, cloning, and sequencing of an enzyme mediating the reductive dechlorination of tetrachloroethene (PCE) from Clostridium bifermen-tans DPH-1. Can J Microbiol AT. 448-456. 

Vitamin B12 catalyzed also the dechlorination of tetrachloroethene (PCE) to tri-chloroethene (TCE) and 1,2-dichloroethene (DCE) in the presence of dithiothreitol or Ti(III) citrate [137-141], but zero-valent metals have also been used as bulk electron donors [142, 143]. With vitamin B12, carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction cis-l,2-DCE, ethene, and ethyne were the main products [138, 139]. Using Ni(II) humic acid complexes, TCE reduction was more rapid, leading to ethane and ethene as the primary products [144, 145]. Angst, Schwarzenbach and colleagues [140, 141] have shown that the corrinoid-catalyzed dechlorinations of the DCE isomers and vinyl chloride (VC) to ethene and ethyne were pH-dependent, and showed the reactivity order 1,1-DCE>VC> trans-DCE>cis-DCE. Similar results have been obtained by Lesage and colleagues [146]. Dror and Schlautmann [147, 148] have demonstrated the importance of specific core metals and their solubility for the reactivity of a porphyrin complex. 

Unlike petroleum hydrocarbons, organic compounds in general followed a different evolutionary path. Chlorinated solvents are a common group of organic compounds, and are also the most frequently encountered contaminant in groundwater. Common industrial chemicals that are characterized as chlorinated solvents include trichloro-ethene (TCE), 1,1,1-trichloroethane (TCA), tetrachloroethene (PCE) or perchloro-ethylene, chlorofluorocarbon (Freon)-113 (i.e., 1,1,2-trichloroethane or 1,2,2-tri-fluoroethane), and methylene chloride. In 1997, the EPA reported the presence of TCE and PCE in 852 of 945 groundwater supply systems throughout the United States and in 771 of 1420 Superfund sites. 

The ARS Technologies, Inc., Ferox process is an in situ remediation technology for the treatment of chlorinated hydrocarbons, leachable heavy metals, and other contaminants. The process involves the subsurface injection and dispersion of reactive zero-valence iron powder into the saturated or unsaturated zones of a contaminated area. ARS Technologies claims that Ferox is applicable for treating the following chemicals trichloroethene (TCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride, 1,1,2,2-tetrachloroethane, lindane, aromatic azo compounds, 1,2,3-trichloropropane, tetrachloroethene (PCE), nitro aromatic compounds, 1,2-dichloroethene (DCE), vinyl chloride, 4-chlorophenol, hexachloroethane, tribromomethane, ethylene dibromide (EDB), polychlorinated biphenyls (PCBs), Freon-113, unexploded ordinances (UXO), and soluble metals (copper, nickel, lead, cadmium, arsenic, and chromium). 

The Salt Lake City Department of Public Utilities in Utah installed a 360-kW unit to treat tetrachloroethene (PCE) in drinking water. The capital investment for the project was 450,000 (1998 dollars). Operating costs for the system were less than 0.20 per 1000 gal of treated water (D197211, p. 1). 

At an electronics manufacturing plant in the southwestern United States, a 30-kW Perox-Pure unit treated 20 gal of groundwater contaminated with TCE, tetrachloroethene (PCE), and dichlororethene (DCE) per minute. The O M costs for these bench-scale tests were estimated to be 1.29 per 1000 gal. Electricity priced at 0.05/kWh contributed 0.75 per 1000 gal of treated groundwater. Based on a cost of 0.65/lb, the addition of hydrogen peroxide cost 0.54 per 1000 gal of water (D17231G, pp. 405, 406, 409). 

Electro-Coatings Facility, Milwaukee, Wisconsin 14,400 tons of soil TCE and tetrachloroethene (PCE) 1,850,000... 

An antibiotic-resistant bacterium, Dehalococcoides ethenogenes strain 195, that Cornell University researchers isolated from sewage sludge, has been found to remove all the chlorine from organic solvents such as tetrachloroethene (PCE) and trichloroethene (TCE) by halorespiration to form ethene, an innocuous end product. 

CESAR was developed to address the problem of locating, characterizing, and removing dense non-aqueous-phase liquids (DNAPLs) from contaminated aquifer systems. The process is particularly suited to remediating groundwater contaminated with chlorinated solvents, such as trichloroethylene (TCE), tetrachloroethene (PCE), trichloroethane (TCE), and carbon tetrachloride (CCE). According to the vendor, CESAR can also be applied to sites contaminated with creosote, polychlorinated biphenyls (PCBs), Freon 113, volatile organic compounds (VOCs),... 

During the pilot-scale field demonstration in Watertown, Massachusetts, two-zone plume interception treatment technology was used to treat a lO-ft-by-20-ft surface area of groundwater contaminated with trichloroethene (TCE) and tetrachloroethene (PCE). The total costs of the project from November 1996 through November 1997 were approximately 150,000 (D21041T, p. 104). 

ISOTEC is a technology that uses the periodic injection of hydrogen peroxide and proprietary catalysts to oxidize organic contaminants in situ. According to the vendor, this technology can treat soil and groundwater contaminated with chlorinated compounds, petroleum hydrocarbons, polychlorinated biphenyls (PCBs), trichloroethene (TCE), tetrachloroethene (PCE), pesticides, herbicides, as well as benzene, toluene, ethylbenzene, and xylene (BTEX). The ISOTEC technology is commercially available. 

According to the vendor, the total cost for treating an estimated 9800 m of contaminated soil at the Sweden 3 Chapman site, in Sweden, New York, for a 12-month duration was 52/m of soil (D18722Y, p. 134). Soil at this site was contaminated with trichloroethene (TCE), tetrachloroethene (PCE), acetone, methylethyl ketone (MEK), methyl isobutyl ketone (MIBK), toulene, and xylene. 

At the U.S. Department of Energy s (DOE s) Kansas City Plant in Kansas City, Missouri, a Ultrox UV/ozone/hydrogen peroxide system was used to treat up to 38 liters/min of groundwater contaminated with tetrachloroethene (PCE). The capital costs were estimated at 380,000. Operation and maintenance costs were estimated to be 5/m of water treated (D19079Y, pp. 3-5). 

Consider the prospects for tetrachloroethene (PCE) to be transported in the gas phase from a contaminated soil out to the atmosphere. For this to occur [either through diffusion (see Chapter 18) or in response to venting during remediation], this PCE must substantially exist in the soil gas. 

You have worked hard to study the internal dynamics of tetrachloroethene (PCE) and to calculate vertical turbulent diffusion coefficients in lakes. A friend of yours is more interested in the process of air-water exchange. One day, she sees some of your PCE data lying on your desk. She is very happy with the table below and... 

Linear Two-Box Model with One Variable Linear Two-Box Model of a Stratified Lake Box 21.7 Linear Two-Box Model for Stratified Lake Illustrative Example 21.5 Tetrachloroethene (PCE) in Greifensee From the One-Box to the Two-Box Model Linear Two-Box Models with Two and More Variables Nonlinear Two-Box Models... 

Linear -Dimensional Systems and Their Eigenvalues Box 21.8 Eigenvalues and Eigenfunctions of Linear Systems Illustrative Example 21.6 Dynamic Behavior of Tetrachloroethene (PCE) in Greifensee... 

Illustrative Example 21.5 Tetrachloroethene (PCE) in Greifensee From the One-Box to the Two-Box Model... 

In Illustrative Example 21.5 we discussed the behavior of tetrachloroethene (PCE) in a stratified lake. As mentioned before, our conclusions suffer from the assumption that the concentrations of PCE in the lake reach a steady-state. Since in the moderate climate zones (most of Europe and North America) a lake usually oscillates between a state of stratification in the summer and of mixing in the winter, we must now address the question whether the system has enough time to reach a steady-state in either condition (mixed or stratified lake). To find an answer we need a tool like the recipe for one-dimensional models (Eq. 4, Box 12.1) to estimate the time to steady-state for multidimensional systems. 

Inhomogeneous systems. If Eq. 21-46 is an inhomogeneous system, that is, if at least one Ja is different from zero, then usually all eigenvalues are different from zero and negative, at least if the equations are built from mass balance considerations. Again, the eigenvalue with the smallest absolute size determines time to steady-state for the overall system, but some of the variables may reach steady-state earlier. In Illustrative Example 21.6 we continue the discussion on the behavior of tetrachloroethene (PCE) in a stratified lake (see also Illustrative Example 21.5). Problem 21.8 deals with a three-box model for which time to steady-state is different for each box. 

In Illustrative Example 21.5 we calculated the steady-state concentrations of tetrachloroethene (PCE) in the epilimnion and hypolimnion of Greifensee for two different input situations. In case a, all the PCE is put into the surface water (epilimnion) whereas in case b the PCE is added only to the hypolimnion. In reality, Greifensee is not stratified during the whole year. Periods of stratification during the warm season are separated by periods of complete mixing (winter). Thus, the lake switches between two distinctly different stages. It seems that the steady-state considerations made in Illustrative Example 21.5 do not adequately reflect the real behavior of Greifensee. 

You have constructed a linear two-box model for tetrachloroethene (PCE) in a lake in which the only input of PCE is from the outlet of a sewage treatment plant. The atmospheric PCE concentration is assumed to be zero in your model. How will the steady-state of the model be altered if the PCE input from sewage is reduced by... 

Calculate the steady-state concentration of tetrachloroethene (PCE) in an evaporative lake with constant volume (lake without outlet in which the inflowing water is balanced by evaporation). Assume that the lake is kept completely mixed and use the following information ... 

P 22.3 Determine Vertical Turbulent Diffusivity in a Lake from Measurements of Tetrachloroethene (PCE)... 

In Chapter 21 the model of a stratified lake served as a prototype of a linear two-box model (Fig. 21.10). The necessary mathematics were developed in Boxes 21.6 and 21.7. In Illustrative Example 21.5 the fate of tetrachloroethene (PCE) in Greifensee was used to demonstrate that for the case of a two-box model it is still possible to carry out back-of-the-envelope calculations. Further examples are given in Problems 23.2 and 23.3, where the behavior of anthracene in a mixed as well as in a stratified lake is assessed. 

A colleague who has to survey the water quality in River A tells you that he needs to quantify the oxygen consumption in the river downstream of a sewage discharge. He shows you the following measurements of dissolved oxygen as well as concentration data for tetrachloroethene (PCE) that is introduced into the river with a constant input by the sewage plant. 

Thus, sorption affects C( ,0) in the same way as if the angular frequency to were increased by the factor (/w)-1 or the period t were reduced by As shown in Fig. 25.7, such a change causes both the attenuation and the specific phase shift P to grow. In Illustrative Example 25.6 we look at the influence of sorption on the transport of tetrachloroethene (PCE) in an aquifer. 

You are interested in the hydraulic and geochemical properties of an aquifer, particularly in its dispersivity and average organic matter content. Fortunately, at your disposition you have long-term time series of water temperature and tetrachloroethene (PCE) measured in two adjacent wells, 15 m apart from each other along the main flow direction in the aquifer. From earlier tracer experiments you are pretty sure that the two wells are located on the same streamline, that is, they see the same water passing by, although not at the same time. 

Figure 25.9 Measured breakthrough curves from the Borden field experiment for tetrachloroethene (PCE) and chloride (Cl ). From Brusseau (1994).

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