PREPARED by (Capsule Laboratories Inc.)
Building structures occasionally are contaminated with one or more hazardous organic chemicals such as PCBs. PCBs have shown an extreme environmental stability and have proven to be very difficult to effectively remediate. Given the history of PCBs spilled and the increasingly stringent cleanup standards, the cost of PCB cleanup is constantly increasing.
The amount of PCB contamination that can be removed in a cleanup differs from site to site depending upon the type of surface to be cleaned, the age of the surface, the elapsed time since the spill occurred, the ability to remove the cleanup chemicals, the type of PCB and whether the cleanup is in an area of repeated spills. Each one of these variables makes comparative evaluations difficult. The factors relating to successful PCB remediation are shown in the following cause and effect diagram.
The majority of PCB spills from electrical transformers takes place on porous materials such as concrete and asphalt. PCBs have shown strong penetrating properties on porous materials. Concrete itself has characteristics which make cleanup difficult, most notably its porosity which directly affects the extent of migration of a liquid or vapor contaminant. Aging and weathering also changes concrete’s porosity and absorption characteristics, making it easier for PCBs to migrate further into the material . Surface defects, such as cracks, provide an easier path into the concrete. In addition, the concrete is usually an integral structural component of the building with demolition and disposal not always being an option.
Another factor affecting PCB cleanup is the variability in field test procedures and the analytical methods for PCB analysis. A solvent wipe sample is not as effective on porous surfaces as on nonporous surfaces. Sample results vary depending upon the total area included in the wipe sample, the person doing the sampling, the location of the sample and the analytical method used. Duplicate analysis of the field sampling and the analytical data show a large variability in the method results.
The final consideration in the cleanup of PCB spills is the regulatory standards. These standards apply to the surface as well as the depth of penetration. The PCB removal system employed must be able to efficiently extract the PCB from the contaminated surface. If this does not work, demolition and disposal of the surface becomes the only option.
The strategy for site remediation should begin with determining the nature and extent of contamination present. The key variables in this stage are: 1) the depth of contamination, 2) the time allowed for cleanup, and 3) the cleanup level required. The final step would evaluate the decontamination effectiveness by using statistically valid sampling and analytical techniques.
A site-specific decontamination plan can be developed by choosing the best remediation process that will efficiently remediate the PCBs. The evaluation of decontamination procedures should consider the production rate of the process, use processes that minimize cross-contamination, effectively reach the depth of contamination and generate as little waste as possible. The methods for surface decontamination can be categorized under the following techniques: 1) chemical processes,
2) scarification, 3) concrete removal, and 4) treatment in situ.
One or more of these methods may be used to achieve the required cleanup standard. Each method will have four major factors that will determine the cost for the cleanup. These factors are: 1) waste generated in the process, 2) the labor involved in a process, 3) the materials needed, and 4) the time allowed for cleanup.
Until recently, the chemical processes used to clean up PCBs were developed for other applications but proved useful for PCB remediation. The cleanup of PCBs was primarily accomplished with the use of like polarity solvents for PCBs, such as kerosene, hexane and chlorinated solvents such as trichlorethylene. Solvents have been used because of their increased PCB solubility. The drawbacks of using solvents are their volatile nature, their flammability and the difficulty in both application and removal. The use of solvents also increases the PCBs’ mobility, allowing them to migrate further into porous surfaces.
Detergents have also been extensively used in cleaning up PCB spills. The surfactants in these products reduce the surface tension which increases the solubility of the soils to be cleaned. Even with the use of a surfactant, PCBs are not very soluble in these products. The soil and oil in the spill area are soluble in detergents, which allows effective surface removal of the PCB. Alkaline detergents rely on their increased surfactant capacity to remove PCBs from the surface while acidic formulations rely on surface etching and increased soil solubility. Due to the polar nature of the detergent, redeposition is a major problem. The PCB-laden soil must be removed before it is redeposited on the surface. Additionally, the difficulty and complexity of waste treatment and disposal requirements present further problems.
Integrated Chemistries, Incorporated has developed a patented PCB extraction process using an aqueous-based solvent system. Chemically, CAPSUR® interacts with the PCB molecule allowing extraction of PCBs from surfaces, and then suspends the PCBs in water allowing easy removal. The formulation also has the additional capability of being applied as a foam blanket which allows application to overhead, vertical and horizontal surfaces. This increases the contact time with the surface and the PCB extraction efficiency while reducing the volume of material needed for cleanup.
The CAPSUR® process was developed by first evaluating bulk extraction efficiencies. A known amount of PCB was put in a graduated conical centrifuge tube and extracted with CAPSUR®. The weight of the extracted PCB determined the extraction efficiency of the product. Extraction efficiencies, in some cases, were as great as 98 percent.
The application procedure for CAPSUR® follows classical laboratory extraction procedures. The contaminated area is foamed, agitated with a stiff broom and left for a five minute dwell time. The residues are vacuumed up, the surface lightly rinsed with water and then revacuumed. The first step is repeated, omitting the agitation step. The area then is foamed with a five-minute dwell time, vacuumed, triple rinsed with water and vacuumed again. The emulsified PCBs are suspended in water and vacuumed up and out of the surface, counteracting the effect that gravity has had on the extent of contamination.
Customer use data has validated the effectiveness of CAPSUR®‘s formulation and application procedure (Appendix 1). These results are consistent with bulk extraction efficiencies predicted in the laboratory and can be used to predict the number of application cycles of CAPSUR® necessary to reach the desired cleanup standards (Appendix 2). In areas with initial spill concentrations less than 200 ug/100 cm2, one application has met regulatory standards. In areas with concentrations ranging from 200 to 800 ug/100 cm2, two cycles are required (Appendix 3). Concentrations greater than 800 require three or more cycles (Appendix 4). This data suggests that the extraction capacity is a function of the extent of PCB contamination and the capacity of the cleanup solvent.
Typically, one of the major problems at a cleanup site is turnaround time for analysis. Once a spill occurs, a field analysis kit, using a Enzyme ImmunoAssay (EIA) kit, could evaluate whether PCBs were spilled and at what concentration levels. The same analysis kit could confirm whether the cleanup was completed or whether further chemical or physical treatment is necessary. The major cost associated with PCB cleanup is the labor involved in the cleanup process. A field analysis kit would make it easier to mobilize cleanup crews when analytical results dictate that cleanup is necessary and keep the crews in the field until cleanup is completed. This kit would eliminate the downtime waiting for lab results and the remobilization costs for the cleanup crew.
Both the enzyme-linked immunosorbent assay (ELISA) and the enzyme immunoassay (EIA) have been shown to be useful residue analysis methods. ELISA and EIA have been used extensively in clinical chemistry but their commercial introduction into environmental chemistry has been relatively recent. The conventional analysis method for the PCB, by GC/ECD or GC/MS, is sensitive and well characterized. However, these instrumental methods are not readily adopted to the development of a fieldable PCB assay. ELISA and EIA can be utilized to develop a fieldable assay kit. The ELISA assay has demonstrated low matrix interference and high sensitivity for the detection of the Aroclor 1242, 1248, 1254 and 1260 PCB mixtures. Appendix 5 is illustrative of the performance of the PCB ELISA format for the analyte Aroclor 1248. The response observed for the assay in this format will provide a detection limit of 840 ppb for a direct sample extract and a detection limit of 17 ppb for a 50x concentrate.
The specificity of this method eliminates interference effects commonly found in other field test kits. The dynamic range, precision, standard deviation and matrix effects approach the capabilities achieved by GC/MS. The test principles are based on the use of antibodies which recognize the analyte. A competition event occurs where a known recorded analyte competes with the unknown analyte. The concentration is determined by the chromogen molecules turning color, with color inversely proportional to concentration. The time for analysis is 20 minutes and the kits are easy to use with no special training required.
As case studies have shown, it is much easier to clean up a new spill than an old spill. As PCB usage is phased out, the remaining challenge will become cleaning up past spills. Knowing to what depth a product can extract and clean the building structure along with a field test kit to confirm cleanup efficiencies will help in site remediation. This will determine if the chemical process alone can meet the standards, if a mix of surface grinding and the chemical process is necessary, or if demolition is the only option.