ANALYSIS OF IMMOBILIZED CELL BIOREACTORS FOR DESULFURIZATION OF FLUE-GASES AND SULFITE SULFATE-LADEN WASTE-WATER/

Sulfur dioxide (SO2) is one of the major pollutants in the atmosphere that cause acid rain. Microbial processes for reducing SO2 to hydrogen sulfide (H2S) have previously been demonstrated by utilizing mixed cu ltures of sulfate-reducing bacteria (SRB) with municipal sewage digest as the carbon and energy source. To maximize the productivity of the SO2-reducing bioreactor in this study, various immobilized cell biorea ctors were investigated: a stirred tank with SRB flocs and columnar re actors with cells immobilized in either kappa-carrageenan gel matrix o r polymeric porous BIO-SEP(TM) beads. The maximum volumetric productiv ity for SO2 reduction in the continuous stirred-tank reactor (CSTR) wi th SRB flocs was 2.1 mmol SO2/h.l. The kappa-carrageenan gel matrix us ed for cell immobilization was not durable at feed sulfite concentrati ons greater than 2000 mg/l or at sulfite feed rate of 1.7 mmol/h.l. A columnar reactor with mixed SRB cells that had been allowed to grow in to highly stable BIO-SEP polymeric beads exhibited the highest sulfite conversion rates in the range of 16.5 mmol/h.l (with 100% conversion) to 20 mmol/h.l(with 95% conversion). In addition to flue gas desulfur ization, potential applications of this microbial process include the treatment of sulfate/sulfite-laden wastewater from the pulp and paper, petroleum, mining, and chemical industries.