Chlorinated organic compounds, environmental

Potential environmental hazards from wastewater sludges are associated with trace constituents (e.g., chlorinated organic compounds) that partition from the effluent into the sludge. It should be noted, however, that recent trends away from elemental chlorine bleaching have reduced these hazards. A continuing concern is the very high pH (>12.5) of most residual wastes. When these wastes are disposed of in an aqueous form, they may meet the RCRA definition of a corrosive hazardous waste.24... 

Glaze WH, Henderson JE, Smith G (1975) Analysis of new chlorinated organic compounds formed by chlorination of municipal wastewater. In Jolley RJ (ed) Water chlorination environmental impact and health effects. Ann Arbor Science, Ann Arbor, MI, pp 139-159... 

The classification of many chlorinated organic compounds as EPA priority pollutants is based on their toxicity combined with environmental persistence. 

Supplement to the 15 th edn. of Standard Methods for the Examination of Water and Waste Water. Selected Analytical Methods Approved and Cited by the US Environmental Protection agency. American Public Health Association, American Waterworks Association, Water Pollution Control Federation, Sept. (1978). Methods S60 and S63. Methods for benzidine, chlorinated organic compounds, pentachlorophenol and pesticides in water and waste water (Interim, Pending issuance of methods for organic analysis of water and wastes, Sept. 1978), Environmental Protection Agency, Environmental Monitoring and Support Laboratory (EMSL). 

The use of chlorinated organic compounds in agriculture and industry has caused a number of environmental problems. A good illustration is provided by the case of 1,1,1 -trichloro-2,2-bis(p-chlorophenyl)ethane, better known as dichlorodiphenyl-trichloroethane, or DDT. 

Generation 11a. These were the now infamous chlorinated organic compounds such as DDT. These compounds have substantial ecological problems and are largely banned in the industrialized world. However, most of these compounds have such long environmental lifetimes that they can still be found (sometimes in surprisingly high amounts) in current environmental samples. Most of these compounds were substantially more toxic to insects compared to mammals. 

Andersson I, Parkman H, Jemelov A. 1990. The role of sediments as sink or source for environmental contaminants A case study of mercury and chlorinated organic compounds. Limnologica 20(2) 347-360. 

Comber, S. and Gardner, M. (1999) An assessment of trends in European environmental data for mercury and chlorinated organic compounds in water and biota. Science of the Total Environment, 243/244, 193-201. 

One use of the electron affinities of molecules is to predict the sensitivity and temperature dependence of the ECD to compounds that might be analyzed. Many environmental pollutants have different multiple substituents. Pesticides are highly chlorinated organic compounds. The chlorinated biphenyls, naphthalenes, and dioxanes are among the most toxic compounds. The temperature dependence of these compounds in the ECD is important, but has not been extensively studied. When the electron affinities and bond dissociation energies are known, the temperature dependence can be calculated from the kinetic model. This is done for the chlorinated biphenyls and naphthalenes, and the calculated temperature dependence is then compared with experiment. These calculations offer clues about the best conditions for analysis. 

Molecular chlorine, CI2, is an ideal chemical for delignification as it is cost-efficient and has reasonable selectivity, well capable of removing 75-90% of the residual lignin in a single stage. However its undesirable effects - waste water with chlorides that is corrosive, and a tiny by-product of chlorinated organic compounds -means that molecular chlorine has been abandoned entirely in some countries and where it is still used this is often in conjunction with chlorine dioxide (D) whose environmental footprint is some 2.6 times smaller. Today, more than 75% of pulps are bleached without any molecular chlorine. These are described as elemental chlorine-free (ECF). Only c. 6% of bleached pulps are total chlorine-free (TCF),... 

Bouwer EJ, McCarty PL. 1982. Removal of trace chlorinated organic compounds by activated carbon and fixed film bacteria. Environmental Science and Technology 16 836-843. 

A recent application of methanogenic bacteria has been in the reductive deha-logenation of halogenated (chiefly chlorinated) organic compounds found as pollutants in wastewater and other environmental sources. This area is beyond the scope of this review, however several recent references are noted. The study by Gantzer and Wackett provides an excellent introduction to the challenges posed by the biostability of (poly)chlorinated organic compounds [118]. 

Figure 16.2a summarizes the major uses of chlorine. Chlorinated organic compounds, including 1,2-dichloro-ethene and vinyl chloride for the polymer industry, are hugely important. Dichlorine was widely used as a bleach in the paper and pulp industry, but environmental legislations have resulted in changes (Figure 16.2b). Chlorine dioxide, CIO2 (an elemental chlorine-free bleaching agent), is prepared from NaC103 and is favoured over CI2 because it does not produce toxic effluents. ...

Environmental organic chemistry is a rapidly expanding subject and one that allows many perspectives. Environmental chemistry historically grew out of analytical chemistry and the ability of analytical chemists to detect very low concentrations of pollutants, especially chlorinated organic compounds, in complex matrices such as soils, atmospheric particles, and animal tissues. The discovery that such pollutants are transported throughout the world, and that some are highly persistent in the environment, led to increasing interest in the fates of such compounds in nature. 

Chlorinated organic compounds (COCs) refer to the substitution of one or more hydrogen in aliphatic and aromatic hydrocarbons and their derivatives by chlorine. COCs are widely used in the fields of chemistry, medicine, electronics, pesticides, etc. Many COCs are endocrine disturbance substances, show carcinogenic effects, and have been listed as priority pollutants by the US Environmental Protection Agency (USEPA). When released into the environment, COCs are transported in both air and water. However, COCs are chemically stable and difficult to destroy, and they are eventually deposited in soils and sediments due to their hydrophobic-ity. Soils and sediments contaminated with COCs are long-term sources of pollutants and pose great threats to human health and ecosystems. Therefore, remediation of these contaminated soils and sediments is of great importance. 

In addition to their oxidizing and reducing properties, the use of chlorine bleaches results in chlorinated organic compounds which have many unwanted environmental consequences. Alternatives are being rapidly implemented. 

Direct thermal combustion represents the conventional technology for the destruction of chlorinated organic compounds. However, besides the very high temperatures (>1000 °C), this route has the typical disadvantage of generating more toxic by-products, such as the polychlorinated carcinogenic and environmentally persistent dibenzodioxins and polychlorinated dibenzofiirans [57]. 

The effluents from the bleaching process contain chlorinated organic compounds and cannot be disposed of by combustion with the spent cooking liquor. It pollutes the waste water stream with its oxygen demand and its toxic and genotoxic effects, it may even contain polychlorinated dibenzo-ftirans and dibenzo-p-dioxins in small concentrations. The stability of the chloro-organic compounds inaeases its biological and environmental persistence and this increases the tendency to bioconcentration in... 

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