Tag: water borne disease

Questions Related to water borne disease

Study the given differences between primary sludge and activated sludge and select the incorrect ones. 

Primary Sludge Activated sludge
(i) It is sludge formed during primary sewage treatment. It is sludge formed during secondary sewage treatment.
(ii) It possesses flocs of decomposer microbes.  It does not possess flocs of decomposer microbes.
(iii) It does not require aeration.  Formation of activated sludge requires aeration.
(iv) A lot of decomposition occurs during formation of primary sludge.  Very little decomposition occurs during formation of activated sludge. 
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  1. (i) and (ii)

  2. (ii) and (iv)

  3. only (iv)

  4. (ii) and (iii)

Show answer
Correct Option: C
Explanation:

The primar sludge is formed during primary sewage treatment, while activated sludge is a sludge during secondary sewage treatment, little decomposition occurs during primary sludge formation, while lot of decomposition occurs during activated sludge.

So, the correct option is 'only (iv)'.

Select the correct statement regarding activated sludge formed during secondary sewage treatment.

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  1. A small part of it is rapidly pumped back from sedimentation to aeration tank.

  2. It absorbs pathogenic bacteria present in waste water while sinking to the bottom of the settling tank.

  3. A major part of it Is anaerobically digested.

  4. Both (a) and (c)

Show answer
Correct Option: D
Explanation:
A small part of activated sludge is pumped back  from sedimentation to aeration tank. But it dos not absorb pathogenic bacteria.
A major part of activated sludge is anaerobically digested by methanogens.
So, the correct option is 'Both (a) and (c)'

____________  is the first step of sewage treatment.

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  1. Precipitation

  2. Chlorination

  3. Sedimentation

  4. Aeration

Show answer
Correct Option: C
Explanation:

Primary treatment in sewage treatment involves physical removal of particles (large and small) from the sewage through filtration and sedimentation. Initially floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. 

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.

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

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

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

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

Show answer
Correct Option: B
Explanation:

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%), $CO _2$ (30-40%) and traces of hydrogen, $H _2S$ and nitrogen.

During the primary treatment of sewage, solid particles that settle down are called

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  1. Flocs

  2. Primary sludge

  3. Activated sludge

  4. Anaerobic sludge

Show answer
Correct Option: B
Explanation:

Primary or physical treatment is the process of removal of small and large, floating and suspended solids from sewage through two processes of filtration and sedimentation. First floating and suspended matter is removed through sequential filtration with progressively smaller pore filters. The sediment is called primary sludge while the supernatant is called effluent. The primary sludge traps a lot of microbes and debris. It is subjected to composting, land fill or anaerobic digestion to produce biogas and manure. 

So, the correct answer is 'Primary sludge'.

Which of the following could be a substance found in waste water that floats on the top and is removed in the Primary Treatment of water?

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  1. Oil and grease

  2. Human faeces

  3. Hair

  4. Plastic

Show answer
Correct Option: A
Explanation:

  • Primary treatment removes material that will either float or readily settle out by gravity. It includes the physical processes of screening, comminution, grit removal, and sedimentation.
  • Human faeces, hair and plastic settle down at bottom while Oil and grease are immiscible in water and are found floating on top.
So, the correct option is 'Oil and grease'.

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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  1. (i), (ii), (iii), (iv)

  2. (i), (ii), (iii), (vii)

  3. (i), (ii) (iv), (v)

  4. (i),(iv),(v), (viii)

Show answer
Correct Option: A
Explanation:
  • Treatment of wastewater is done by the heterotrophic microbes naturally present in the sewage. 
  • This treatment is carried out in two stages: 
  1.  Primary treatment: These treatment steps basically involve physical removal of particles large and small from the sewage through filtration and sedimentation. Initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge and the supernatant forms the effluent. The effluent from the primary settling tank is taken for secondary treatment.
  2. Secondary treatment or Biological treatment: The primary effluent is passed into large aeration tanks. 
  • Hence, (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 affluent. (iv) The Sludge is taken for Secondary treatment following statements & about wastewater treatment are correct. 

  • So, the correct answer is '(i), (ii), (iii), (iv)'.

Which of the following statements is correct ?

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  1. Activated sludge - sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria

  2. Biogas is produced by the activity of aerobic bacteria on animal feed

  3. Methanobacterium is an aerobic bacterium found in rumen of cattle.

  4. Biogas, commonly called gobar gas, is pure methane.

Show answer
Correct Option: A

Permutit is the trade name of a mixture of?

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  1. Hydrated silicates of Ca and Mg

  2. Hydrated silicates of Al and Na

  3. Hydrated aluminates of Ca and No

  4. None of these

Show answer
Correct Option: A
Explanation:
The permutit process is a process in where hard water containing such as Calcium is filtered through natural sand called the zeolite.
This is the hydrated silicate of Ca and Mg.
So, the correct option is 'Hydrated silicates of Ca and Mg'

Which of the following is correct for sewage discharge in river?

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  1. At the discharge point B.O.D is high and fishes die

  2. At the discharge point D.O. is high

  3. B.O.D increase downstream ion river

  4. From the discharge 50 KM away, Fishes ,die

Show answer
Correct Option: A