A method of biotreating a
solid material to remove an undesired compound using a nonstirred surface
bioreactor is provided. According to the method the surface of a plurality of coarse substrates is coated with a
solid material to be biotreated to form a plurality of coated coarse substrates. The coarse substrates have a particle size greater than about 0.3 cm and the
solid material to be biotreated has a particle size less than about 250 mu m. A nonstirred surface reactor is then formed by stacking the plurality of coated coarse substrates into a heap or placing the plurality of coated coarse substrates into a tank so that the
void volume of the reactor is greater than or equal to about 25%. The reactor is inoculated with a
microorganism capable of degrading the undesired compound in the
solid material, and the
solid material is then biotreated in the surface
bioreactor until the undesired compound in the
solid material is degraded to a desired concentration. Preferably the thickness of the solid material
coating on the plurality of coarse substrates is less than about 1 mm and the
void volume of the reactor is greater than or equal to about 35%. The process is useful for many different
biotreatment processes, including the
bioremediation of
contaminated soils, the desulfurization of
coal, and the biooxidation of
refractory sulfide ores and concentrates. In
bioremediation applications, the undesired compound is typically an
organic compound. In
coal desulfurization and
refractory sulfide ore biooxidation applications, the undesired compound is
sulfide minerals.