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單項(xiàng)選擇題

（）are used to digest the sewage to produce innocuous sludge in a biological sewage treatment plant.

A.anaerobic bacteria
B.aerobic bacteria
C.air bubbles
D.disinfection chemicals

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單項(xiàng)選擇題

The extended aeration process consists of （） the liquor either by bubbling air through it or by agitating the surface.

A.deoxygenating
B.oxygenating
C.chemicalizing
D.disinfecting

單項(xiàng)選擇題

A number of biological sewage treatments plants are in use at sea but nearly all work on the principle called （）

A.deoxygenating
B.extended aeration
C.oxygenating
D.bubbling air

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