FEASIBILITY OF COAL TAR BIODEGRADATION BY COMPOSTING

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 GROUND WATER. A LARGE FRACTION OF THE COAL TAR CONSISTS OF 2 OR 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 BIODEGRABLE, WHICH THE HIGHER MOLECULARWEIGHT 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 ADVANTAGED OF THE CONTROL OF VOLATILE EMISSIONS AND AVOIDS THE PROBLEMS OF LEACHATE CONTAMINATION OF GROUNDWATER.