Growth of acidophilic chemolithotrophic microbial communities and sulfur oxidation in the presence of coal ashes

Out of two communities of acidophilic chemolithotrophic microorganisms (ACM), a mesophilic and a thermophilic ones, the latter was selected due to its higher rate of sulfur oxidation and pH decrease to >1 in the presence of coal ashes (CA). The structure of ACM communities was retained. Sulfur-oxidizing activity of the microorganisms from the thermophilic community was observed at pH from 1.8 to 2.6 at sulfur concentrations of 0.6–1.0%. Efficient production of acidic solutions with pH 0.69–0.86 was observed after single CA introduction in the amount corresponding to 5–30% pulp density and in the course of pulp density increasing daily from 1 to 50%. Leaching of rare earth elements from 30% coal ash pulp (pH 0.76) was 15 to 30% of their initial content. No sorption of metals on the biomass was observed.