Patent ID: 8123944

Claim:
A method of aqueous solids treatment comprising: digesting the aqueous solids in a thermophilic digestion vessel under thermophilic conditions to produce thermophilic digested solids, wherein the thermophilic digestion vessel is aerobic or anaerobic; then transferring the thermophilic digested solids to a mesophilic aerobic digestion vessel; and then digesting the transferred thermophilic digested solids in the mesophilic aerobic digestion vessel under mesophilic conditions; wherein the mesophilic aerobic digestion vessel comprises bacteria capable of oxidizing hydrogen sulfide to sulfur or reducing sulfur dioxide to sulfur, and wherein the bacteria metabolize the sulfur, such that the concentration of hydrogen sulfide or of sulfur dioxide within the thermophilic digested solids is reduced during said mesophilic aerobic digestion.