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－　　－13High-Concentration Organic Wastewater Treatment Using Inclusively Immobilized Soil BacteriaIwahito TAKAHASHI, Katsumi SATO, Tomoe KOMORIA, Daisuke KISHINA and Hiroaki MORITAActivated sludge method is a wastewater treatment technique used for removing organic matter from sewage using bi-ological floc. It is widely used as a low-cost and environmentally friendly method for sewage treatment. However, this method is not suitable for treating high-concentration wastewater　since it is often necessary to perform physicochemi-cal pretreatment, such as dilution with water, pressure floatation treatment, or chemical treatment. The aim of this study is to biologically treat high-concentration wastewater using a suitably selected soil bacteria. The soil bacteria adopted in this study were separated and cultured from the soil collected in Okinawa Prefecture in 2012. The base sequence was then determined, and the homology search was performed by Basic Local Alignment Search Tool of the DNA Data Base of Japan. It was found to be a soil bacterium called Agrobacterium Tumefaciens by 99% homology. When Agrobacte-rium Tumefaciens was directly used to treat high-concentration wastewater, it caused sludge bulking, and its treatment capacity was low and the chemical oxygen de-mand value found using chemiluminescence detection of permanganate index (CODMn) was unstable. However, there was no outflow of bacteria from the inside of the inclusion when Agro-bacterium Tumefaciens were inclusively immobilized by the sodium alginate-acrylamide method, which suggests that the sludge volume can be reduced. The CODMn concentration of the artificial sewage added was 1500 mg/L, which was exponentially attenuated, and a high removal rate of 96% was observed 12 hours after the start of treatment. Fur-thermore, the allowable design value for the volumetric load is 3CODMn-kg/m3 per day, and thereby the compactifica-tion of wastewater treatment facility should be possible. These findings have proved that the treatment method proposed in this article is significant in the field of excluded facilities for the purpose of high-concentration wastewater treatment because of reduction of cost and facility area.Keywords: high-concentration wastewater, biological treatment, inclusion immobilization method, soil bacteria, sludge bulking包括固定化した土壌細菌を用いた高濃度排水処理技術の研究　活性汚泥法は，好気性微生物によって有機物を除去する方法であり，コストや環境負荷に対して利点が多いことから下水処理に広く利用されている．しかし，高濃度排水処理には適しておらず，このため，高濃度排水に対しては，前処理として，水による希釈や加圧浮上処理，薬品処理などといった物理化学的処理を行う必要がある．本研究は，高濃度排水に適した土壌細菌を選定し，これを用いた生物処理を目的とした．用いた土壌細菌は，2012年に沖縄県で採取した土壌から分離培養したものであり，日本DNAデータバンクのBLASTによる相同性検索を行った結果，相同性99％でAgrobacterium Tumefaciensという土壌細菌であることが判明した．このAgrobacterium Tumefaciensをそのまま高濃度排水処理に用いるとバルキング現象を引き起こし，処理能力は低く，処理後のCODMn値も不安定であった。それに対し，Agrobacterium Tumefaciensをアルギン酸ナトリウム-アクリルアミド法で包括固定化することにより，包括内部からの菌の流出は見られず，このことから汚泥発生量の低減が図れるものといえる．また，投入した人工下水のCODMn濃度1500mg/Lに対し，指数関数的に減衰し，処理開始12時間後に96％の高い除去率が認められた．さらに，容積負荷は3CODMn-kg/m3・日が許容設計値となり，このことから排水処理施設の小型化が図られるといえる．　以上のことから，本報で提案する処理方法は，コスト削減，施設面積の縮小が図られ，高濃度排水処理を目的とした除外施設の分野において有意性があるものといる。キーワード：高濃度排水，生物処理，包括固定化，土壌細菌，バルキングJournal（掲載誌）Journal of JSCE, Vol.9, 198-204, Apr. 2021.Published Paper