DESULFOVIBRIO-DESULFURICANS GROWTH-KINETICS

Growth kinetics of Desulfovibrio desulfuricans, strain NCIMB 9467, was studied in laboratory scale, under well-controlled batch conditions. This research is oriented toward the practical, industrial removal of sulfate and metal ions from mine water. Growth of the microorganism in such waters was verified. From 290 experimental observations of sulfate and lactate (obtained from 145 culture tubes of 20 mL) the parameters of a Monod model were estimated. Inoculum mass was not measured but it was incorporated as another model parameter. Hydrogen sulfide was removed by addition of ferrous iron, which rapidly formed iron sulfide and precipitated toward the bottom of the culture tube. Parameters were estimated by a nonlinear least squares parameter minimizer. The growth-limiting substrate was the sulfate concentration. Under these conditions the growth of Desulfovibrio desulfuricans was characterized by a maximum growth rate of 25 . 10(-3) h-1, a sulfate affinity constant of 850 mg/L, and a reduced sulfate yield of 6.2 . 10(-3) (biomass per sulfate mass). Inoculum was 1.97 mg of bacteria/L and the consumption of lactate was characterized by a yield of 2.5 . 10(-2) (biomass per lactate mass). Sulfate was reduced at a rate of 400 mg/L/day while lactate was oxidized at a rate of 1100 mg/L/day. Mine wastewater was used as sulfate source and complemented with lactate as the carbon source. Under these conditions the strain growth was similar to that obtained with the controlled media. It was concluded that no inhibitory effects exist. The reduction velocity obtained, 200 mg/L/day, was lower than before, probably due to inoculum size or strain adaptation. A novel process is proposed to produce solid sulfur from sulfate and sulfur oxides.