SBIR-STTR Award

Coal tar is a by-product of the coal gasification process used between 1880 and 1950 to produce a natural gas substitute. It is estimated that several billion gallons of this material were land-disposed at over 1500 sites in the United States. The tar contains seventeen polynuclear aromatic hydrocarbons (PAH) which have been placed on the EPA priority pollution list as a result of their mutagenicity and toxicity. The buried coal tar is of environmental concern as it can migrate as a liquid phase, slowly releasing the toxic hydrocarbons to soil and groundwater.A large fraction of the coal tar consists of 2 and 3 ring PAH which are known to be easily biodegradable by common soil bacteria in laboratory experiments. The 4-6 ring PAH may also be biodegradable, while the higher molecular weight substances in the tar are considered to be environmentally inert. Thus the potential exists for the treatment of coal tar wastes by biodegradation. Similar wastes, such as petroleum sludges, have been biodegraded by land treatment. This study proposes to determine the feasibility of treating coal tar waste by composting, a process of controlled biodegradation which has the advantage of the control of volatile emissions and avoids the problems of leachate contamination of groundwater.

Coal tar is a by-product of the coal gasification process used between 1880 and 1950 to produce a natural gas substitute. It is estimated that several billion gallons of this material were land-disposed at over 1,500 sites in the U.S. The tar contains seventeen polynuclear aromatic hydrocarbons (PAH) which have been placed on the EPA priority pollutant list as a result of their mutagenicity and toxicity. The buried coal tar is of environmental concern because of the continuous release of toxic hydrocarbons to soil, ground water, and the atmosphere. Current in-place management of coal tar deposits by capping or restricting access is not feasible or cost effective if the deposits are extensive or if subsurface migration is occurring. Controlled biodegradation of heavily tar-contaminated soil by composting is an attractive alternative to physical containment. Its feasibility has been demonstrated by CAA Bioremediation Systems in a Phase I, Small Business Innovation Research Grant. The cost effective biodegradation of heavily tar-contaminated soil will be demonstrated in the Phase II project on site in a pilot scale, static pile, forced aeration compost reactor. The degree of biodegradation attained in the treatment process will be monitored and documented in order to define the role of composting in comprehensive site remediation. Methods will also be developed during this project to quantify and control volatilization during material excavation, transport, mixing and treatment.