单项选择题
（）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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相关考题
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单项选择题
For a given exhaust gas boiler, what is the quantity of its evaporation mainly determined?（）
A.the temperature and flow quantity of the exhaust gas from M.E
B.the quantity of steam demanded
C.the rotary speed and the cooling water temperature of main engine
D.efficiency of M.E turbocharger -
单项选择题
A purge recovery system is used in a centrifugal air conditioning or refrigeration system to （）
A.purge lube oil from the liquid refrigerant
B.recover water purged from the system
C.separate foul gases from the receiver
D.purge non-condensable gases without losing refrigerant -
单项选择题
Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?（）
A.Sub-cooled liquid
B.Sub-cooled vapor
C.Superheated vapor
D.Liquid
