Remediation of PCBS

Committee on Remediation of PCB-Contaminated Sediments Board on Environmental Studies and Toxicology Division on Life and Earth Studies National Research Council, 2001. A Risk-Management Strategy for PCB-Contaminated Sediments. National Academy Press. Washington, D.C. 

The use of subcritical water extends beyond destruction. A method for remediation of PCB-contaminated soil and sediments has been described that uses zerovalent iron as the dechlorination agent and subcritical water extraction (SWE) as the transporting medium. The initial findings indicate that this technique may be a viable method for remediation of PCB-contaminated soil and sediments (Yak et al., 1999). 

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. 

Polychlorobiphenyls (PCBs) have been studied under the UV/Ti02 photo-catalytic process to assess the use of photocatalytic oxidation in the treatment of PCBs. These organic microcontaminants are biologically refractory therefore, AOPs were studied for the remediation of PCBs. Haloaliphatic and haloaromatic compounds have been found to be mineralized to C02 and HC1 by UV/Ti02 process (Mathews, 1988). 

The remediation of contaminated sediments has been shown to decrease PCB concentrations in fish inhabiting contaminated rivers. For example, one study monitored PCB concentrations in fish before and after remediation of PCB contaminated sediment (Bremle and Larsson 1998). It was found that PCB concentrations in lake water decreased from 0.0086 to 0.0027 pg/L, while concentrations in fish were halved after remediation was completed. Although concentrations of PCBs in fish decreased after remediation, the relative composition of PCB congeners remained relatively the same as before remediation. Fish still concentrated higher chlorinated congeners relative to levels detected in lake water (Bremle and Larsson 1998). 

Hong, Chia-swee State University of New York Albany, New York Photocatalytic remediation of PCB-contaminated water and sediment NIEHS... 

TavlaridesL. 1998b. Supercritical fluid technology—remediation of PCB/PAH contaminated soils. 

Generally we can note that polychlorinated organic compounds like PCBs are very resistant to various bioremediation procedures and physical-chemical treatments are the most used for heavily contaminated sites. For remediation of PCB-contaminated sites the following technologies can be recommended. 

Utilizing Pd nanoparticles formed by bioreduction is more feasible for in situ remediation of PCB-contaminated soils because the reactions take place at room temperature. However, the use of Eef p) might be preferred despite the need for elevated temperatures, because of the multiple reactions of Fe p) with other soil contaminants, including As, Cr, and PAH. 

J.H. Hartig and M.A. Zarull Table 3. Timetable for remediation of PCB contaminated sediments in Waukegan Harbor, Illinois. ... 

Recently, Commodor Solutions Technology Inc. (88,89) and Pittman and co-workers (90-93), have pioneered the ambient temperature, solvated-electron reduction of PCBs, both neat and in wet soils, using Ca/NHs and Na/NHs. Remediation of PCB- and chlorinated aliphatic hydrocarbon-contaminated soils, wet and dry by solvated electron reductions at ambient temperatures, are addressed by Pittman et al in chapter 25. Dechlorination rates using Na/NHs are huge (diffusion controlled) and the chlorine is mineralized as NaCl. High dechlorination efficiencies are available at reasonable consumptions of sodium metal. In this technique, wet soils were slurried in liquid NH3 and then either calcium or sodium metal was dissolved. The solvated electrons dechlorinated PCBs to biphenyl at far faster rates than the solvated electrons were consumed by water. While this method is promising for environmental remediation, it requires a suitable reaction vessel able to sustain the moderate pressures produced by ammonia at temperatures between 0 and 50°C. Ammonia boils at -33 °C, but its use as a liquid in the 0 to 50 °C range is standard practice in industry. 

Solvated Electron (Na/NHj) Dechlorination of Model Compounds and Remediation of PCB-and CAH-Contaminated Wet Soils... 

The discovery that microbial dechlorination of PCBs was occurring in many aquatic sediments brought the hope that this process would provide a natural means of remediation [371,451]. Dechlorination decreases the bioaccumulation potential of PCBs by making them more degradable and is expected to decrease the potential toxicity of PCBs [2,34,105,371,451-453]. Extensive microbial dechlorination of PCBs has occurred in some aquatic sediments including those of the Hudson River (NY) and Silver Lake (Pittsfield, MA) [371]. 

According to DTC, typical operating costs range from 50 to 100 per feed ton (0.91 metric tons) for refinery-type wastes, and 100 to 200 per feed ton for soil remediation. DTC notes that estimates are feed and product quality sensitive and site specific. Remediation of polychlorinated biphenyl (PCB)-contaminated soil must also take into account the cost of destroying the concentrated PCB product (D110410, p. 7). 

The PCB-REM process for the remediation of polychlorinated biphenyls (PCBs) in soils, sludges, and water uses both chemical and biological treatment. It is a combination of solids pretreatment... 

The IT Corporation thermal destruction unit is a mobile unit that uses infrared incineration technology. The main objective of this process is to transform the feedstock into another form (an ash acceptable for delisting) while assuring safe discharge of exhaust gas products to the environment. The unit is capable of on-site remediation of wastes and soils contaminated with polychlorinated biphenyls (PCBs) and other organics. This technology is based on a conveyor belt furnace process. 

The problem of PCB pollution continues into the 21st century. Several legal cases have dominated the media in recent years, such as General Electrics responsibility to remediate the Hudson River and Monsanto s and Solutia s 600 million dollar settlement in 2003 with Alabama over claims concerning Monsanto s Anniston, Alabama plant. 

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. 

WHO has conducted three international studies of PCBs, polychlorinated dibenzodioxins, and polychlorinated dibenzo-furans in human milk during 1987-2003 (WHO 2000). The first two surveys were conducted in 1987-1988 and 1992-1993 in a number of European countries. The third, conducted in 2000-2003, included additional countries. A fourth survey has been developed with the intent to assess the persistent organic pollutants (POPs) found in human milk so that each country can better identify and set priorities among POPs for remedial action (WHO 2000). The sample population will include at least 50 mothers from each country who are planning to breastfeed (WHO 2005). Two sampling periods have been proposed, the first to obtain a baseline sample of POPs in representative... 

A project consists of the removal of PCB-contaminated media at three different cleanup sites a loading dock, a transformer storage lot, and a disposal pit. There are several different types of bulk PCB remediation wastes at the three sites that must be identified and sampled separately as follows ... 

Either field or laboratory personnel prepare composite samples by mixing equal aliquots of grab samples and taking an aliquot of a well-mixed composite of sufficient weight for laboratory analysis. Grab samples selected for compositing must be of the same type of bulk PCB remediation waste the TSCA does not allow compositing of different types of PCB waste. 

Use embryo and fetal cell cultures to determine if remediation of several classes of mixtures of environmental toxicants (PCBs, HAHs, PAHs) decreases the toxicities of the parent mixtures or actually enhances the toxicities... 

Table 2 demonstrates the remediation of 100 g of PCB-contami-nated soil samples by Ca/NH3 (excess Ca). In clay, sandy, or organic soils, the destruction efficiencies were >99.9%. Similar studies were done with sodium. Calcium can be used effectively but becomes far less efficient than sodium as the amount of water in NH3 increases [24],... 

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