BIOLOGICAL TREATMENT OF MALODOROUS GAS

PROBLEM TO BE SOLVED: To provide a biological treating method of a malodorous gas for sufficiently decomposing methyl mercaptane, methyl sulfide and methyl disulfide and effectively deodorizing with improved removing ratio of hydrogen sulfide. SOLUTION: The malodorous gas containing sulfur-containing compounds is passed through a packed layer carrying microorganism. A part of the treated gas is returned to the packed layer, treated again with the malodorous gas and the treated gas is discharged to the outside of the system. The treating efficiently is improved by providing two or more stages of the packed layer 2, 4, decomposing mainly hydrogen sulfide in the front stage of the packed layer and decomposing the residual relatively hardly decomposable sulfur compounds into hydrogen sulfide and a residual group in the post stage of the packed layer. The microorganism is preferably activated by adjusting the front stage of the packed layer to pH 2-3 and the post stage of the packed layer to pH 6.5-7.5.