单项选择题
A.both as clarifiers B.first one as clarifiers, second one as purifier C.both as purifiers D.first one as purifier, second one as clarifier
Concerning the management of sewage treatment plant usi...
单项选择题Concerning the management of sewage treatment plant using activated sludge, which of the following is correct?（）
A.the plant should be prohibited to supplying air B.the plant should work at intervals C.the plant should be added disinfector in time D.we should check strength of activated sludge, ivory-white color is best
Disinfector in the sewage biological treatment plant us...
单项选择题Disinfector in the sewage biological treatment plant usually is （）
A.chlorine water B.ozone C.hypo-calcium chloride D.calcium oxide
Before marine sewage treatment plant works （） should be...
单项选择题Before marine sewage treatment plant works （） should be filled with fresh water.
A.deposition chamber B.oxidation pool C.disinfection chamber D.all chamber
