MICROBIAL REMOVAL OF ORGANIC SULFUR FROM COAL

THE U.S. POSSESSES HUGE COAL RESERVES, BUT SULFUR DIOXIDE (SO2) RELEASED UPON COMBUSTION IS A MAJOR CONTRIBUTOR TO ACID RAIN. SIGNIFICANT ADVANCES HAVE BEEN MADE IN THE DEVELOPMENT OF MICROBIAL PROCESSES FOR PRECOMBUSTION REMOVALOF INORGANIC SULFUR FROM COAL. THIOBACILLUS AND SULFOLOBUS SP. HAVE BEEN MOST FREQUENTLY EMPLOYED. THEY ARE OPTIMALLY ADAPTED TO FUNCTION AT A PH BELOW 3 AND OFTEN AT ELEVEATED TEMPERATURES. HOWEVER, THESE CONDITIONS HAVE BEEN INEFFECTIVE IN REMOVAL OF ORGANIC SULFUR FROM COAL. UNDER NATURAL CONDITIONS, BACTERIA AND FUNGI FOUND IN COAL ARE LARGELY NEUTROPHILIC. ONLY AFTER EXPOSURE TO AIR AND WATER AND ACTIVITY OF IRON-METABOLIZING BACTERIA DOES THE PH BEGIN TO FALL AND THE ACIDOPHILES INCREASE IN NUMBER. COMPLEX MICROBIAL COMMUNITIES OCCURRING NATURALLY IN SULFUROUS WATERS INCLUDE HETEROTROPHIC MICROORGANISMS ABLE TO TRANSFORM ORGANIC SULFUR INTO MORE READILY REMOVED FORMS. GROUPS OF MICROBES INHABITING SULFUROUS, NON-ACIDIC WATER WILL BE COLLECTED AND SCREENED FOR THEIR ABILITY TO REMOVE ORGANIC SULFUR FROM COAL. EMPHASIS WILL BE PLACED ON USE OF AN ENTIRE MICROBIAL COMMUNITY, RATHER THAN ISOLATING ONE OR TWO ORGANISMS.