Ferrous sulphate oxidation using Thiobacillus ferrooxidans cells immobilised on sand for the purpose of treating acid mine-drainage

Abstract

Thiobacillus ferrooxidans was immobilised on sand (size 0.85 mm to 1.18 mm) for use in a repeated batch and continuously operated packed-bed bioreactor which has not been previously reported in the literature. Repeated batch operation resulted in the complete oxidation of ferrous to ferric iron. The bacteria were active immediately after 3-4 weeks in a non-aqueous medium; i.e. the sand was allowed to dry out, demonstrating the stability of the system. A lag phase of 28 days was recorded when the sand was stored dried in a sealed container for 16 weeks compared with a lag phase of 13 days for a sample frozen for 18 weeks. After a period of 10 days, continuous operation of the reactor at a dilution rate of 0.64 h(-1) resulted in 95-99% oxidation of ferrous iron or 0.31-0.33 kg m(-3) h(-1). With the use of a scanning electron microscope, images were recorded of Thiobacillus ferrooxidans on sand.

Using biochemical system to improve cinnabar dissolution

“…A maximum concentration of 1.32 g/L was achieved at dilution rate of 0.4/h or higher. The trend of mercury concentration was similar with ferrous iron oxidation rate discussed previously since increasing the dilution rate led to a higher ferrous iron oxidation rate (Wang et al, 2007;Wood et al, 2001). This may indicate that cinnabar dissolving has relation to ferrous iron oxidation rate and ferric iron concentration.…”

Simultaneous oxidation and precipitation of iron using jarosite immobilized Acidithiobacillus ferrooxidans and its relevance to acid mine drainage

“…Assuming that the kinetics of Fe 2+ oxidation and biomass growth were the same for free and attached cells, a similar Fe 2+ oxidation rate would be expected if there was no significant difference in the inoculated bacterial concentration (Karamanev, 1991;Wood et al, 2001). Thus, the number of viable bacteria retained in jarosite was calculated to be about 3 × 10 8 cells g − 1 ; lower than those reported by Pogliani and Donati (2000) (10 9 cells g − 1 ) and Kinnunen and Puhakka (2004) (3.12 × 10 10 cells g − 1 ).…”

“…have been investigated (Jensen and Webb, 1995;Pogliani and Donati, 2000). After the iron oxidation step, limestone is the preferred neutralizing agent because it is less expensive than lime and its application produces a lower volume of sludge (Akcil and Koldas, 2006;Sandstrom and Mattsson, 2001;Wood et al, 2001). However, the precipitation of Fe(OH) 3 can armor the limestone surfaces, significantly decreasing the rate and extent of limestone dissolution and alkalinity production (Cravotta and Trahan, 1999).…”

Geochemical and Temporal Influences on the Enrichment of Acidophilic Iron-Oxidizing Bacterial Communities

“…Active bioreactors can also effectively oxidize Fe(II) and remove Fe(T) from solution and are considerably more effective than passive systems on a space basis. Acidophilic Fe(II) oxidizers Acidithiobacillus spp., Leptospirillum spp., and Ferrovum myxofaciens have all been enriched in both fixed-film and suspended-growth laboratory-scale bioreactors for AMD treatment (39)(40)(41)(42). Natural, mine-impacted microbial communities dominated by Ferrovum myxofaciens and Gallionella-related strains were also enriched in pilot-scale bioreactors (33,43,44).…”