(NL9500577-A)      In the treatment of a gas (1) contg. hydrogen sulphide, in which the gas is washed with an alkaline wash liq. in a scrubber (5), the spent wash liquor (4) is treated with oxygen in an aerobic reactor (6) in the presence of sulphide-oxidising bacteria, elemental sulphur is removed from the reactor effluent (9), and the effluent (13) then used as wash liq. in the scrubber. The effluent (13) is treated in an anaerobic reactor (17) with sulphate-reducing bacteria and returned to the aerobic reactor.    Also claimed is an appts. for the above process.    USE -   Used for treating natural gas, coal gas and other gases required for use. The gas may contain NH3, HCN, SO2, COS and/or CS2.    ADVANTAGE -   In the unmodified process, small amts. of sulphate are produced in the aerobic reactor, and accumulate in the system. In the modified process above, sulphate (and any SO2 in the gas) is reduced to sulphide, in the anaerobic reactor, and the sulphide converted to elemental sulphur in the aerobic reactor.    (EP814894-A1)      In the treatment of a gas (1) contg. hydrogen sulphide, in which the gas is washed with an alkaline wash liq. in a scrubber (5), the spent wash liquor (4) is treated with oxygen in an aerobic reactor (6) in the presence of sulphide-oxidising bacteria, elemental sulphur is removed from the reactor effluent (9), and the effluent (13) then used as wash liq. in the scrubber. The effluent (13) is treated in an anaerobic reactor (17) with sulphate-reducing bacteria and returned to the aerobic reactor.    Also claimed is an appts. for the above process.    USE -   Used for treating natural gas, coal gas and other gases required for use. The gas may contain NH3, HCN, SO2, COS and/or CS2.    ADVANTAGE -   In the unmodified process, small amts. of sulphate are produced in the aerobic reactor, and accumulate in the system. In the modified process above, sulphate (and any SO2 in the gas) is reduced to sulphide, in the anaerobic reactor, and the sulphide converted to elemental sulphur in the aerobic reactor.    (EP814894-B1)      In the treatment of a gas (1) contg. hydrogen sulphide, in which the gas is washed with an alkaline wash liq. in a scrubber (5), the spent wash liquor (4) is treated with oxygen in an aerobic reactor (6) in the presence of sulphide-oxidising bacteria, elemental sulphur is removed from the reactor effluent (9), and the effluent (13) then used as wash liq. in the scrubber. The effluent (13) is treated in an anaerobic reactor (17) with sulphate-reducing bacteria and returned to the aerobic reactor.    Also claimed is an appts. for the above process.    USE -   Used for treating natural gas, coal gas and other gases required for use. The gas may contain NH3, HCN, SO2, COS and/or CS2.    ADVANTAGE -   In the unmodified process, small amts. of sulphate are produced in the aerobic reactor, and accumulate in the system. In the modified process above, sulphate (and any SO2 in the gas) is reduced to sulphide, in the anaerobic reactor, and the sulphide converted to elemental sulphur in the aerobic reactor.    (US5976868-A)      In the treatment of a gas (1) contg. hydrogen sulphide, in which the gas is washed with an alkaline wash liq. in a scrubber (5), the spent wash liquor (4) is treated with oxygen in an aerobic reactor (6) in the presence of sulphide-oxidising bacteria, elemental sulphur is removed from the reactor effluent (9), and the effluent (13) then used as wash liq. in the scrubber. The effluent (13) is treated in an anaerobic reactor (17) with sulphate-reducing bacteria and returned to the aerobic reactor.    Also claimed is an appts. for the above process.    USE -   Used for treating natural gas, coal gas and other gases required for use. The gas may contain NH3, HCN, SO2, COS and/or CS2.    ADVANTAGE -   In the unmodified process, small amts. of sulphate are produced in the aerobic reactor, and accumulate in the system. In the modified process above, sulphate (and any SO2 in the gas) is reduced to sulphide, in the anaerobic reactor, and the sulphide converted to elemental sulphur in the aerobic reactor.