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Standard IX
Biology
Water Recycling
Study the fol...
Question

Study the following statements and select the incorrect ones.


(i) Physical removal of large and small particles through filtration and sedimentation is called primary sewage treatment.
(ii) Secondary sewage treatment is mainly a mechanical process.
(iii) Activated sludge sediment in a sewage treatment plant is a rich source of aerobic bacteria.
(iv) Biogas, commonly called as gobar gas, is pure methane.

A
A-(iii), B-(i), C-(iv), D-(ii)
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B
A-(i), B-(iii), C-(iv), D-(ii)
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C
A-(iii), B-(ii), C-(iv), D-(i)
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D
A-(iii), B-(i), C-(ii), D-(iv)
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Solution

The correct option is D A-(i), B-(iii), C-(iv), D-(ii)
Secondary treatment is also called biological treatment or microbial degradation. It is mainly a biological process. Biogas is a mixture of gases, containing predominantly methane (50-70%), CO2 (30-40%) and traces of hydrogen, H2S and nitrogen.

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Q. Assertion :Secondary treatment of sewage is also called biological treatment while primary treatment is called physical treatment. Reason: Primary sewage treatment depends only upon sedimentation properties of materials present in sewage and filtration.
Q.

Physical removal of large and small particles from the sewage through filtration and sedimentation is called:


Q. Refer the given flowchart of sewage treatment, accordingly match Column I with Column II and select the correct answer from the codes given below:


Column IColumn IIA.The stage in which physicaltreament of sewage is done(i)Anaerobic degestion of activatedsludge and production of biogasB.The stage in which biologicaltreatment of sewage is done(ii)Activated sludgeC.Name of the sediment in primary treatment(iii)Aeration tanksD.It is carried to aeration tanks fromprimary settling(iv)Primary effluentE.Name of the sediment in secondary treatment (v)Primary sludgeFSite of flocs growth(vi)Secondary treatmentGFunction of sludge digester(vii)Primary
Q. Microbes are used in
(i) primary treatment of sewage
(ii) secondary treatment of sewage
(iii) production of biogas
(iv) production of bioactive molecules
Q. Read the following statements & about waste water treatment how many of them are correct
(i) In Primary treatment First, floating debris of waste is removed by sequence filters
(ii) The Soil and small pebbles are removed by sedimentation in settling tanks
(iii)The sediment is called primary sludge and supernatant is effluent.
(iv) The Sludge is taken for Secondary treatment.
(v) Lower the B.O.D., higher Is water pollution.
(vi)When DDT enters the food chain then they reach water and are easily degradable.
(vii)Discharge of sewage water into river water will decrease its B.O.D.
(viii) Chlorine is added to disinfect drinking water

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