Although much publicity has focused on polychlorinated biphenyls (PCBs) and the need for pipeline companies to prevent and remove their contaminating effects, very little is known about the mechanisms by which they are transported in pipelines. This paper describes a research project that is currently being undertaken to foster a better understanding of this problem and also discusses some preliminary results.
Polychlorinated biphenyls (PCBs) were first manufactured in 1929. Because of their unique chemical stability and compatibility to many organic solvents, these compounds have been used quite extensively in many industries under the trade name of Aroclor series (Erickson, 1986). One such use of PCB-based oils is as compressor lubricants for gas pipeline transmission and handling facilities. It was not until 1966 that the hazards of PCBs were recognized by the industry which led to its final ban in the U.S. in 1976, when Congress passed the Toxic Substances Control Act (TSCA). In regulations promulgated by the TSCA, the EPA has determined that the manufacture, processing and distribution in commerce of PCBs and PCB-containing products at concentrations at or above 50 parts per million (ppm) by weight constitutes an unreasonable risk of injury to health. Under regulations adopted pursuant to the California Hazardous Waste Control Act of 1981, PCB-containing materials are considered hazardous waste at five milligrams per liter, or approximately five (ppm) by weight. Despite the cessation of using this product since its ban, the past use of PCB-based oil as lubricants has resulted in their continued persistence in natural gas transmission and distribution systems. Due to the toxic and perhaps carcinogenic nature of PCBs, the gas industry is alarmed with the environmental problems that could be manifested by these chemicals and recognized the need to clean up the pipeline transmission and distribution systems that have been contaminated by them. However, with several hundred thousand miles of pipelines criss-crossing the country, it is cost prohibitive and perhaps fool-hardy to subject the entire pipeline system and handling facilities to clean-up without having identified the parts that have been contaminated. The major questions in planning any PCB remediation efforts include the following. What are the possible sources and sinks of PCBs in the system? What are the migration and transport mechanisms of PCBs in the transmission and distribution systems? What are the effects of PCBs on the phase behavior of natural gas systems? How is it possible to trace and clean up PCBs in pipeline and handling facilities? Is the current knowledge-base and technology adequate to resolve these problems? These are some of the major questions that need to be addressed. In order to answer these questions, it is important to understand the physico-chemical behavior of PCBs as they exist in natural gas mixtures. Adequate studies should be conducted to identify the distribution of PCB in pipeline systems so as to devise the appropriate remediation strategies and formulate optimal clean-up plans.