ENHANCED REMOVAL EFFICIENCY OF MALODOROUS GASES IN A PILOT-SCALE PEAT BIOFILTER INOCULATED WITH THIOBACILLUS-THIOPARUS DW44

A newly isolated autotrophic bacterium, Thiobacillus thioparus DW44, which is capable of degrading sulfur-containing gases, was inoculated into a pilot-scale peat biofilter to treat the exhaust gas from a night soil treatment plant. Hydrogen sulfide (H2S), methanethiol (MT), dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the exhaust gas were efficiently removed for six months. Average removal ratios were 99.8% for H2S, 99.0% for MT, 89.5% for DMS and 98.1% for DMDS at a space velocity of 46 h-1 during the period of operation. No acclimation period was needed to reach such a high efficiency in the removal of the gases, indicating that the ability of this bacterium to remove these gases was occurred immediately after its inoculation to the peat. Ammonia (NH3) in the exhaust gas was neutralized with SO4(2)..., which is the final product of the oxidation of H2S, MT, DMS and DMDS by the bacterium. No remarkable decline of pH, which often causes a deterioration in bacterial activity, was observed, mainly because of the reaction of SO4(2-) with NH3. This study is the first report on the application of an isolated microorganism to a practical deodorizing system. The inoculation of T. thioparus DW44 into the pilot-scale peat biofilter could overcome such disadvantages of the conventional peat biofilter as a long acclimation period to reach a constant gas removability and the low removability of DMS, and resulted in enhanced removal efficiency of malodorous gases.