Removal of inorganic and organic sulphur from fossil fuels by bacteria

Abstract

Some soil-coal moist samples collected from a coal mine were checked for sulphur oxidizers using the recommended liquid media for acidophilic and non acidophilic thiobacilli, of ph 2.5, 4.5 nd 7.5 with ferrous sulphate, sulphur and sodium thiosulfate, separate or in combinations as energy sources were tried. The coal mine samples were found devoid of such bacteria (even after 28 days of incubation) indicating that this coal mine in its surrounding does not have sulphur source for energy for such bacteria. Isolation of some bacteria capable of utilizing thiophene as carbon, sulphur and energy source and reducing sulphate as end product was carried out. Oil-soil samples collected previously were used to isolate these cultures using modified Bushnell and Haas (BH) medium and thiophene (5% v/v). Modified BH medium was prepared by using chloride salts of the components instead of sulphate salts and the sulphate produced was analysed spectrophotometericaly. In two samples out of 12 tested, sulphate ions were formed to a level significantly higher than in control flasks as well as other tested flasks. The inorganic sulphur present in three Japanese coal samples was found to be amenable to attach by both T. thio oxidans and T. ferro oxidans strains, previously isolated from local systems. Coal sample No. 1 and No. 2 are better oxidised by T. ferro oxidans whereas for sample No. 3, T. thio oxidans were found better. This behaviour may be contributed to higher ash contents in the first two samples: more metals present were directly attacked by T. ferroxidans, while T. thio oxidans lack the ability to attack the metals directly. (author)