Patent ID: 7754471

Claim:
A process, comprising: subjecting an SO 2 -containing gas stream comprising a concentration of H 2 S and a concentration of SO 2 to a direct reduction step to yield a direct reduction tail gas; wherein said concentration of H 2 S in said SO 2 -containing gas stream is in the range of from 0.5 to 3 volume percent of said SO 2 -containing gas stream and said concentration of SO 2 in said SO 2 -containing gas stream is in the range of from 0.05 to 1 volume percent of said SO 2 -containing gas stream, wherein said direct reduction tail gas has a concentration of SO 2 that is less than 1000 ppmv; and biologically treating with a sulfur bacteria selected from the group consisting of Beggiatoa, Thiothrix and Thiobacillus , said direct reduction tail gas to yield a sweet tail gas and a bioreactor sulfur product; wherein said sweet tail gas has a concentration of H 2 S less than 100 ppmv.