To make it possible to exhibit stable deodorization performance at a low cost and during an extended period even for a malodorous gas of composite odor with variation of an odor concentration and an odor quality.SOLUTION: A biological filter 21, which digests a malodorous gas G by biological treatment, is configured from a wood chip 21A, a floor material 23 having many vent holes 22A is accommodated in a housing H which has an introduction port 24a, in which the malodorous gas is introduced, at a lower part thereof, and the wood chip 21 is filled onto the same. By sprinkling which is performed by sprinkling means 30 from above the biological filter 21, a moisture content of the wood chip 21A is so maintained as to be 150% or more and 300% or less. Further, an excess water W, which passed the biological filter 21 by circulation means 40, is recovered and is fed to the sprinkling means 30, thereby circulating water to be sprinkled by the sprinkling means 30.SELECTED DRAWING: Figure 2【課題】臭気濃度や臭気質の変動を伴う複合臭の臭気ガスに対しても、低コストで長期間安定した脱臭性能を発揮できること。【解決手段】臭気ガスＧを生物的処理によって消化するバイオフィルタ２１を木材チップ２１Ａで構成し、下方に臭気ガスが導入される導入口２４ａを有するハウジングＨ内に、多数の通気孔２２Ａを有する床材２３を収容して、その上に木材チップ２１を充填し、散水手段３０によってバイオフィルタ２１の上方からなされる散水により木材チップ２１Ａの含水率を１５０％以上、３００％以下に維持する。また、循環手段４０によりバイオフィルタ２１を通過した余剰水Ｗ1を回収し散水手段３０に供給することで、散水手段３０で散水する水を循環させている。【選択図】図２
