PCBs , contaminants from transformers

It has been mentioned above that a vapor cleaning system has been proven successful in removing surface PCB contamination from areas previously considered inaccessable. Tbe method has tbe advantage that a minimum quantity of PCB contaminated fluid is derived for disposal in contrast to tbe drain and flush method wbicb produces several times tbe volume of tbe transformer tank. Also, as tbe level of PCB contamination in tbe mineral oil increases tbe vapor cleaning method becomes increasingly necessary and eventually becomes tbe only viable cost-effective procedure. 

Girvin et al. [358] evaluated the release of PCBs from electrical substation soils contaminated with transformer fluids. They observed that there are two phases to the uptake and release of PCBs with these soils. The initial phase is a rapid, labile phase that is followed by a slower, nonlabile phase. The labile phase occurs at a scale of hours to days while the nonlabile phase releases over weeks and months. Girvin et al. [422] also reviewed the effects of adsorption on the mobility of PCBs and their transport. In an example presented for a hexa-chlorobiphenyl, these authors noted that the PCB isomer would have a retardation factor Rf of 1400 for the particular case given. This means that the ground-... 

Polychlorinated biphenyls (PCBs) were manufactured by catalytic chlorination of biphenyl to produce complex mixtures, each containing 60-90 different PCB molecular species or congeners (see Chaps. 1 and 4). In the United States, PCB mixtures were manufactured by Monsanto under the trade name Aroclor and were widely used as dielectric fluids in capacitors and transformers from 1929 to 1978. PCBs are widespread contaminants of aquatic sediments and continue to be a focus of environmental concern because they tend to accumulate in biota and are potentially toxic. The following sections show the most effective bioremediation techniques applied to various PCB contaminated environments ... 

Polychlorinated biphenyls (PCBs) are a family of compounds that were used extensively in electrical equipment, such as transformers, because of their insulating and heat transferring qualities. They are suspected human carcinogens and have been linked to liver, kidney, and other health problems. It is known that PCBs can be transported by air, and this is thought to be one of the major ways in which they circulate around the world, explaining why they are found in the Arctic and Antarctic. Indian women dwelling on Cornwall Island located in the Canadian portion of the reservation have elevated levels of toxic PCBs in their breast mUk. The PCB contamination does not appear to come from fish, but from air the women breathe every day [45]. 

The TechXtract process was used at a warehouse where PCB contamination resulted from the storage of electrical transformers. The decontamination costs for the concrete floor at this... 

It has become clear over the past ten years that the 1980s demonstration of anaerobic microbial dechlorination of PCBs is probably the most important discovery in the field of PCB biotransformations since Ahmed and Focht first demonstrated in 1973 that PCBs were biodegradable. Many new anaerobic microbial activities have been enriched and characterized from anaerobic fresh water and marine environments and heavily polluted industrial sediments. These anaerobic cultures are capable ofdechlorinating PCBs, thereby transforming highly chlorinated Aroclors to lower-chlorinated mixtures. This natural attenuation process is an important contributor to PCB degradation and detoxification in the environment and can form the basis for intrinsic remediation of many PCB-contaminated sites. 

Thus, knowledge of the dominant transformation or transport processes would lead to a more informed decision concerning remediation of PCB-contaminated systems and would improve fate predictions. For example, the best remedial action for a biologically mediated system may simply be to allow the PCBs to degrade over time into a less toxic form. Conversely, remediation of contaminated systems dominated by physiochemical modification of the PCB congeners may require an active response to prevent the problem from moving into environmental compartments over which there is little or no control. 

PCBs are not manufactured in Malaysia and the import of PCBs has been banned since 1995. However, there are still old transformers and capacitors in use that contain PCB-contaminated oil (Hashim, 2001). Since 1998, PCB stockpiles and PCB-contaminated transformer oils have been properly disposed of at the Kualiti Alam Integrated Waste Management Centre, Bukit Pelanduk. A total of 15.5 tons of PCBs and 22 tons of transformer oils was incinerated at the site from 1998 to 2004 (Idris, 2004). There is no available record on the total import of PCBs and PCB containing products. Under the National Implementation Plan for compliance to the Stockholm Convention, an exercise to produce a PCB inventory for Malaysia has been carried out but the report has not been made public. 

Coates, J.T., Elzerman, A.W. (1986) Desorption kinetics for selected PCB congeners from river sediments. In Transport and Transformation of Organic Contaminants. D.L. Macalady, Ed., J. Contam. Hydrology 1, 191-210. 

A dramatic illustration of the mass of the chemical repository is the catastrophic release of a small proportion of this reservoir that occurred with the tragic destruction of the World Trade Center in New York City on 11 September 2001. In addition to the dreadful loss of life when the Twin Towers were destroyed, the destruction of these two towers resulted in the dispersal of 1.2 million tons of building debris, along with some fraction of the 130 000 gal of PCB-contaminated transformer oil from the two transformers housed in the buildings, and the dispersal of PBDEs contained in the estimated 50 000 personal and 300 main frame computers (Butt et al., 2004). 

Nevertheless, EPA created a number of exceptions to the extension of marking requirements to items containing between 50 and 500 ppm PCBs. First, PCB-contaminated transformers were not required to be marked because of cost considerations according to EPA, 35 million such transformers were in use and marking all of them would cost about 350 million. 44 Fed. Reg. 31521. In addition, EPA stated that persons who had petitioned for exemptions from the ban on PCB manufacture would not be required to label chemicals that contained less than 500 ppm PCB until EPA acted on their petitions. 44 Fed. Reg. 31522. 

Although PCBs no longer are being produced for electrical products in the U.S., the EPA estimates that thousands of PCB transformers and millions of PCB small capacitors may stiU be in use or in storage. The threat of widespread contamination from PCB fire-related incidents is one reason behind the EPA s efforts to reduce the number of PCB products in the environment. The users of high-power equipment are affected by the regulations primarily because of the widespread use of PCB transformers and capacitors in old equipment. Table 22.3 Hsts the primary classifications of PCB devices. 

Alan Q. Eschenroeder and Edward J. Faeder, "Human health risks from PCB - contaminated mineral oil transformers," PCB seminar, Seattle, Washington, October 22-25, 1985. 

In September 1983, a fire occurred in a transformer vault under the plaza on the same block as the First National Bank building in Chicago. Smoke issued from a sidewalk grating for about 45 min. but, fortunately, significant PCB contamination was limited to the vault. 

An initial, fundamental decision must be made concerning whether to change the classification of the transformer to PCB contaminated ie., <500 ppm PCB, or to <50 ppm PCB and remove the unit from TSCA purview. 

The decision to retrofill rather than replace a contaminated transformer depends, as discussed above, upon a number of different factors. For example, the cost of new oil and the cost of labor have to be weighed against the benefits of reduced maintainance, service and disposal costs, the impact of public perception, and reductions in the possible costs of leaks, spills or fires. Once a decision has been made to retrofill, the usefulness of the action is governed by the effectiveness of the process to mitigate the problem of PCB leaching from the impregnated coil. 

Polychlorinated Biphenyls. There are several sources of polychlorinated biphenyls (PCBs) in museums. Often these are first discovered by waste-disposal companies that pick up a museum s hazardous refuse. Disposal companies usually analyze solvent, paint, and other hydrocarbon wastes because disposal of PCB-contaminated material is vastly more complex and expensive than disposal of ordinary wastes. In some cases, museum waste has been contaminated by fluids leaking from transformers or fluorescent light ballasts, both of which are common sources of PCBs. However, on two occasions of which the present author is aware, the contamination was from Arochor slide-mounting medium (a material which contains PCBs and polychlorinated triphenyls) and/or PCB-contaminated pigments such as phthalocyanine blue and green, and diarylide (benzidine) yellow. 

Secondary sources of PCDD/PCDFs, their reservoirs, are those matrices where they are already present, either in the environment or as products. Product reservoirs include PCP-treated wood, PCB-containing transformers and sewage sludge, compost and liquid manure, which can be used as fertilizers in agriculture and gardens. Reservoirs in the environment are, for example, landfills and waste dumps, contaminated soils (mainly from former chemical production or handling sites), and contaminated sediments (especially in harbours and rivers with industries discharging directly to the waterways). 

Polychlorinated biophenyls (PCBs) Heat and fire resistant - extensively used from 1929 and 1977 in electrical transformers All manufacture banned - extensively regulated - very widespread global contaminant... 

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