Biodesulfurization of Flue Gases Using Synthesis Gas Delivered as Microbubbles

Introduction Anaerobic treatment processes for biodegradation of hazardous materials have increasingly been gaining attention in environmental applications. Microbial processes utilizing sulfate reducing bacteria (SRB), in particular, have found potential applications in variety of treatment processes such as flue gas desulfurization [1,2], gypsum reclamation [3], sulfur recovery from sulfitdsulfate wastewater from pulp and paper, chemical and mining industries [4], and degrading explosive materials [51. However, in all these applications, the source of electron donor is a major factor on the economics of the process. Previously, we have proposed a microbial process with sewage digest as an attractive low-cost feedstock for SRB cultures in the desulfurization of flue gases and sulfitdsulfate-laden industrial waste water [6] . In that process, a columnar reactor with mixed SRB cultures immobilized in BIO-SEPm polymeric porous beads with sewage digest as a carbon and energy source exhibited conversion rate of 16.5 mmol sulf i tehl (32 kg/d.m3) with 100% conversion to HzS. Though municipal sewage digest is a readily available low-cost carbon source, the real cost of the medium depends on the location of the sewage treatment plant and power plant and on the transportation involved in bringing the sewage back and forth from the sewage plant. Therefore, the current research has been focused on an alternative low-cost feedstock. Various groups have demonstrated that SRB could be suppo$d by carbon dioxide and/or carbon monoxide as the sole carbon source and hydrogen as the energy source [7-111. Du Preez et al. [8,10] operated a sulfate-reducing reactor with a mixed SRB population to demonstrate the feasibhty of using syn-gas as the feed source for SRB. Recently, van Houten et al. [9] reported the operation of a gas-lift sulfate-reducing reactor that was fed a CO-HZ mixture (up to 20% CO) and yielded a maximum sulfate conversion rate of 30 g SO:/d.L.