单选题Most marine biological sewage treatment plants consist of all the following statements except （）.A aeration tanksB settling tanksC disinfection agentD anaerobic bacteria

A.agitation function

B.bacteria

C.chemica

D.oxidizing function

most of australia’s unique plants and animals are imported from other continents. ()

A.boiler

B.separator

C.incinerator

D.treatment lological sewage

24． The reason why most plants can’t grow on the sandy beach is that

A． there isn't enough sunlight

B． there is too much water

C． it is too crowded there

D． it has little food for plants

Biological treatment may use __ to treat sewage (1)living organisms (2)chemicals (3)additives

A.(1)

B.(2)

C.(3)

D.(1)(2)(3)

A、consists of

B、consist of

C、is consisted ofare consisted of

第三组：

The sewage treatment system must be capable of discharging an effluent that comes within the limits of the tests. Sewage can be treated biologically so that it may be discharged with minimal damage to ecosystem. Biological treatment involves the use of living organisms to treat the sewage within the sewage treatment plant so the liquids and sludge discharged are within the standards specified.

Biological treatment plants are usually built up as a module and consist of various sections.

Waste matter collected from the ships sanitary appliances is led through a sanitary piping system to the treatment module. The solid matter is broken up by passing it through a screen or a series of revolving cutters. The broken up solid material, together with the waste liquid, passes into a tank containing bacteria which require oxygen and a nutrient to propagate. The nutrient is contained in the solid waste material, and oxygen is supplied by bubbling compressed air through the broken up waste. The propagated bacteria change the waste material into a sludge by aerobic digestion. The sludge is finally treated to kill the coliform. bacteria before it is passed overboard.

When a biological sewage plant is started up, such as when activating a new ship or after cleaning out the tank, a pellet containing bacteria is introduced into the tank. It takes approximately one week for the bacteria to propagate and make the system fully effective. The choice of sanitary appliance cleaners requires extreme care, as many cleaners are toxic to the active bacteria. Once a biological sewage plant is made active it should not be shut down. If it is it will have to be reactivated again because the bacteria will die without a supply of nutrients and oxygen.

Bacteria that require oxygen for their survival are referred to as aerobic. Aerobic bacteria are normally used in ships&39; sewage treatment equipment. Other forms of bacteria that do not require oxygen are referred to as anaerobic. Anaerobic bacteria are used in shore based sewage treatment works where methane is obtained as a by-product for use as fuel.

This passage is mainly about

A.sewage treatment methods

B.the various sections of a sewage treatment plants

C.biological sewage treatment system

D.how the sewage treatment plants are started up

A.aeration tanks

B.settling tanks

C.disinfection agent(消毒剂

D.anaerobic bacteria(厌氧菌)

A

Why do plants grow in some places and not in others? Why does some land have so much growing on it，while other land has almost no plants growing on it at all?

To grow plants need several things． One is warmth． In very cold places almost nothing grows． Plants also need water． In very dry parts of the earth only a few unusual plants can grow． That's why dry deserts everywhere are almost not covered by trees or grass．

Plants must also have a place in which to f，ut down their roots and grow． They find it diffi-culr to grow on hard land． The town is built on hard land． The plants here have only the soil found between the cracks of the stones Io grow in．

Another thing plants must have before they can grow is food．

Whar will happen if we try to make things grow on the sandy beach? A few plants，such as beach grass，will grow in sand，L ut most plants won-t． Even if the weather is warm enough．and we water the plants each day． Many of them will die because the sand on this beach has al-most no food for plants．

( )21． According to the passage，plants need _________ things to grow well．

A． two

B． three

C． four

D． five

Most marine biological sewage treatment plants consist of all the following statements except ______.

A.aeration(通风) tanks

B.settling tanks

C.disinfection agent(消毒剂)

D.anaerobic bacteria(厌氧菌)