Worker Exposure to Chlorinated Organic Compounds from the Activated-sludge Wastewater Treatment Process
The objective of this research was to investigate some of the potentially controlling factors influencing the atmospheric releases of volatile organic chlorinated compounds from the activated-sludge sewage treatment process. The field study was designed to evaluate the wastewater and airborne concentrations of six chlorinated compounds: hexachlorobicycloheptadiene (hex-BCH), heptachlorobicycloheptene (Hex-VCL), chlordene, chloroform (CHCl3), carbon tetrachloride (CCl4) and tetrachloroethylene (TCE). Analysis of samples consisted of saturating 5 mL aliquots with sodium chloride, extracting with an equal amount of petroleum ether (PE) and subsequent analysis using a gas chromatograph. The air samples collected on Chromsorb 102 were desorbed with 2 mL PE. The study revealed that the highest wastewater concentrations for the water-insoluble hex-BCH, hex-VCL and chlordene were found in the aeration basins, which suggests adsorption of these compounds to the biomass. The plant effluent wastewater concentrations were reduced because of airborne release and suspended solids separation in the clarifiers. In contrast, the wastewater concentrations for the more water-soluble CHCl3, CCl4 and TCE were significantly reduced in the aeration basins. This is because of aerial stripping at the grit-chamber weir. This study suggests that the water-insoluble compounds have prolonged aerial release from the aeration basins. The water-insoluble compounds adhere to the biomass, which is recycled through the plant. The aerial release of these water-insoluble compounds was enhanced by increased aeration rate but depressed by higher suspended solids concentrations.
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ABSTRACT: The adsorptive capacities of activated carbon for major organic constituents (target compounds) of a wide variety of wastewater were measured in pure water and in actual wastewater samples. Competitive adsorption due to the presence of other orgnic components of total organic carbon of the wastewater (background TOC) reduced carbon capacities for all target compounds in the wastewaters from the respective pure water isotherms. The capacity reduction for a target compound was found to depend on the relative adsorptivity of the target compound versus competing compounds (poorly adsorbed TOC components produced a small reduction in capacity for a more strongly adsorbed target compound), and the fraction of the background TOC attributable to the target compound. Those findings were validated by carbon column adsorption breakthrough data.Environmental Progress 02/1990; 9(1):1 - 9. DOI:10.1002/ep.670090111 · 1.31 Impact Factor
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ABSTRACT: This article describes a systematic review of the industrial hygiene literature for uses of trichloroethylene (TCE) in industry for the exposure assessment of two population-based case control studies of brain cancer in the United States. Papers and reports that address uses of and exposures to TCE were identified from MEDLINE, TOXLINE, NIOSHTIC, the NIOSH Health Hazard Evaluation database (keywords: chlorinated solvents and trichloroethylene), and in other reviews. This search was complemented by reviewing the reference lists from the identified literature. The collected information was systematized by the Standard Industrial Classification (SIC) system, and measurement data reported in the literature were summarized in a database. TCE use was extensive from the early 1920s through the 1970s mainly as a degreasing agent in metal-fabricating operations. After the 1970s it became less popular because of environmental concerns. TCE historically has had a multitude of uses in many other industries, e.g., dry cleaning, textile, electronics, leather, and rubber. Also, many products like adhesives, drugs, paints, inks, and various industrial products have contained TCE. It was banned as a food additive and in cosmetics in 1977. The arithmetic mean (AM) of the measurements across all industries and decades was 38.2 ppm. The highest personal and area air levels were reported in vapor degreasing (AM of 44.6 ppm). Most TCE measurements were performed in the 1950s, 1970s, and 1980s. The data described here could be used by exposure assessors as is to identify the presence and approximate levels of exposure. Using the same information as a basis should increase the reliability of the assessments, making it easier to compare both the exposure assessment methods and the epidemiologic results across different studies.Journal of Occupational and Environmental Hygiene 06/2007; 4(5):375-90. DOI:10.1080/15459620701301763 · 1.17 Impact Factor
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