DMSO含有排水の膜分離活性汚泥処理

摘要

DMSO（ジメチルスルホキシド）含有排水の処理を生物処理単独で行うことを目的として，膜分離活性汚泥処理試験を行った。ラボ試験の結果，DMSO濃度300~1800mg/Lの排水に対しDMSO/MLSS（活性汚泥濃度）負荷の限界は約0.2kgDMSO/（kgMLSS・d）であった。 この時の処理水TOC（全有機炭素）濃度は5mg/L（DMSO25mg/L）以下であり，良好な処理が可能であった。LCD（液晶ディスプレイ）製造工場に試験装置を設置し，実排水を対象に実証試験を行った。DMSO/MLSS負荷をラボ試験で得られた限界負荷以下となるように運転管理を行うことで，ラボ試験と同等の処理性能が得られた。本試験ではDMSO中の硫黄はSO_4~(2-)（硫酸イオン）まで酸化され，臭気が問題となるDMS（硫化ジメチル）などの中間生成物の蓄積はなかった。また，馴善した活性汚泥の微生物群はHyphomicrobium属の細菌が優占種と考えられた。%A demonstration test for examining MBR (Membrane BioReactor) treatment (activated sludge treatment combined with submerged membrane filtration process) was conducted with the aim of treating waste water containing DMSO (dimethylsulfoxide) with biological treatment alone. Laboratory scale tests revealed that the limit of DMSO/MLSS (activated sludge concentration) loading was approximately 0.2 kg DMSO/(kgMLSS-d) in the case of waste water with a DMSO concentration of 300 to 1 800 mg/L. The TOO (total organic carbon) concentration of the treated water was 5 mg/L (DMSO 25 mg/L) or less, which indicates that MBR is capable of providing high-performance treatment. A demonstration test was conducted, in which test equipment was installed at an LCD (liquid crystal display) production plant and an actual factory effluent was used. By controlling the operation so that the DMSO/MLSS loading did not exceed the limit load obtained in the laboratory scale tests, treatment performance equivalent to that of the laboratory scale tests was achieved. In this test, sulfur in DMSO was oxidized to SO_4~（2-）(sulfate ion), and no intermediate products such as DMS (dimethyl sulfide), which produces offensive odor, were accumulated. In the microbial community of the acclimated activated sludge, Hyphomicrobium sp. Bacteria seemed to be the dominant species.