Environmental Studies · Chemistry

Water and Wastewater Treatment

1,423 Questions

This topic deals with water purification, wastewater treatment methods, and industrial effluent management. It includes questions on filtration, disinfection, and water hardness removal. These concepts are tested in environmental science and engineering exams.

Water purificationWastewater treatmentBioremediation strategiesWater hardness removalIndustrial effluent management

Water and Wastewater Treatment Questions

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Activated sludge should have the ability to settle quickly so that it can

  1. Be rapidly pumped back from sedimentation tank aeration tank.

  2. Absorb pathogenic Bactria present in waste water while sinking to the bottom of the settling tank

  3. Be discarded and anaerobic ally digested

  4. Absorb colloidal organic matter
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Activated sludge should have the ability to settle quickly so that it can be rapidly pumped back from sedimentation tank to the aeration tank, where it can start the process of decomposition of the organic matter again. Activated sludge has filamentous bacteria that are capable of performing the aerobic digestion of organic waste is the sewage water.

Hence, the correct answer is 'Be rapidly pumped back from sedimentation tank aeration tank' 

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Waste water treatment generates a large amount of sludge, which can be treated by

  1. Anaerobic digesters

  2. Floc

  3. Chemicals

  4. Oxidation pond
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen.
  •  The process is used for industrial or domestic purposes to manage waste and to produce fuels. 
  • Hence, Wastewater treatment generates a large amount of sludge, which can be treated by anaerobic digesters.
  • So, the correct answer is 'anaerobic digesters'.
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Chlorine treatment

  1. Removes all the air pollutants

  2. Disinfects water by killing germs

  3. Removes hardness of water

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Chlorine is a powerful disinfectant that can kill the bacteria and viruses by destabilizing the chemical bonds of the pathogens. So, it is used in purification of water.

Hence, the correct answer is 'Disinfects water by killing germs'

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Secondary treatment is carried out for removal of;

  1. Suspended solids

  2. Dissolved organic matters

  3. Floating materials

  4. Solid impurities
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Secondary sewage treatment is a biological process designed to remove dissolved organic matter by using microorganisms to break down the waste.

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Identify the correct sequence of steps involved in the treatment of sewage.
(i)   Growth of aerobic microbes to reduce BOD
(ii)  Sequential filtration for removing floating debris
(iii) Production of inflammable gas
(iv) Growth of anaerobic microbes for digestion of bacteria

  1. i, iv, ii, iii

  2. ii, iv, i, iii

  3. ii, i, iv, iii

  4. iv, ii, iii, i
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The sequence is: (ii) filtration to remove debris, (i) aerobic treatment to reduce BOD, (iv) anaerobic digestion of sludge, and (iii) production of biogas.

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The primary treatment of sewage water involves.

  1. Sludge digestion

  2. Aerobic bacterial activity

  3. Anaerobic bacterial activity

  4. Filtration and sedimentation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Primary treatment is a physical process that involves the removal of large floating debris through filtration and the settling of solid particles through sedimentation.

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Which one is a biological in sewage treatment?

  1. Primary treatment

  2. Secondary treatment

  3. Tertiary treatment

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The sewage treatment unit employs the primary, secondary and tertiary treatment for the complete process. In the primary treatment, filtration of the large and solid waste is done. Then in secondary treatment, the decomposing microbes are used for the breakdown of the organic sewage. So, the secondary treatment is the biological treatment of the waste water. In the tertiary treatment, the chemical treatment is provided to the water.

Hence, the correct answer is 'Secondary treatment'

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Chlorination of treated waste water is required for

  1. Killing all microbes

  2. Removing suspended materials

  3. Complete breakdown of organic matter

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Chlorination is the process of treating the water with chlorine to kill the water-borne microbes that can possibly cause diarrhoea, typhoid, jaundice, amoebiasis etc. It is performed during the tertiary treatment step. Chlorine compounds like sodium hypochlorite are added to water to give effect to the process.

A. Chlorination kills the microbes.
B. Suspended particles are removed by filtration.
C. The complete breakdown of organic matter occurs by decomposition during the secondary treatment.
Hence, the correct answer is 'Killing all microbes'

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In treatment of waste, biological treatment is

  1. Primary treatment

  2. Secondary treatment

  3. Tertiary treatment

  4. Reverse osmosis stage
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The sewage treatment unit employs the primary, secondary and tertiary treatment for the complete process. In the primary treatment, filtration of the large and solid waste is done. Then in secondary treatment, the decomposing microbes are used for the breakdown of the organic sewage. So, the secondary treatment is the biological treatment of the waste water. In the tertiary treatment, the chemical treatment is provided to the water.

Hence, the correct answer is 'Secondary treatment'

Multiple choice bio-chemistry biochemical techniques centrifugation separation techniques separation of matter

Which of the following devices uses the principle of centrifugation?

  1. Washing machine

  2. Ceramic water filter

  3. Household ultraviolet (UV) purifier

  4. Distillation tower
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Centrifugation is a technique which involves the application of centrifugal force to separate particles from a solution according to their size, shape, density, the viscosity of the medium and rotor speed. The larger the size and the larger the density of the particles, the faster they separate from the mixture. Example- washing machine works on the principle of centrifugation.

Multiple choice bio-chemistry biochemical techniques centrifugation separation techniques separation of matter

Which of the following devices uses the process of centrifugation?

  1. Washing machine

  2. Ceramic water filter

  3. Household ultraviolet (UV) purifier

  4. Distillation tower
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the process of centrifugation, we use a rotator and because of that the heavier particles in the solution get settled at the bottom and we get a clear solution, in washing machine we are having rotator at the bottom and hence it can be used for the process of centrifugation.

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Primary treatment of sewage is

  1. Physical process

  2. Biological process

  3. Chemical process

  4. Biochemical process
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Primary treatment of sewage involves physical processes like sedimentation and filtration to remove large particles and suspended solids. It does not involve biological or chemical degradation.

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Sewage treatment process includes all of these features, except

  1. A small part of the activate sludge is pumped back into the aeration tank to serve as incoculum

  2. Activated sludge cannot be used in anaerobic digestion process

  3. Anaerobic bacteria digest aerobic bacteria in sludge digesters

  4. Transfer of primary effluent in aeration tanks
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The process of removal and digestion of inorganic and organic waste present in the sewage water is called sewage treatment.

A. The flocs of bacteria obtained after treatment of the sewage water is called activated sludge. A small part of it is pumped back into the aeration tank which will act as inoculum and will multiply to start the digestion of organic compounds again.
B. Activated sludge can be anaerobic bacterium as well.
C. In sludge digesters, the digestion of organic compounds occurs.
D. Primary effluent is transferred to the aeration tanks for the purpose of digestion through aerobic bacteria.
Hence, the correct answer is 'Anaerobic bacteria digest aerobic bacteria in sludge digesters'.

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Among the following, which do not come under the category of sewage treatment?

  1. The organic material present in the waste is allowed to undergo microbial oxidation

  2. Large size material are filtered through screen

  3. The waste water is suitably treated for the removal of phosphate by the coagulation method

  4. Degrading the number of toxic organic waste
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sewage treatment is the process of removing contaminants from wastewater, primarily from household sewage. It includes physical, chemical, and biological processes to remove these contaminants and produce environmentally safe treated wastewater (or treated effluent).

The sewage treatment involves three stages, called primary, secondary, and tertiary treatment. First, the solids are separated from the wastewater stream. Then, dissolved biological matter is progressively converted into a solid mass by using indigenous, water-borne micro-organisms. Finally, the biological solids are neutralized, then disposed of or re-used, and the treated water may be disinfected chemically or physically (for example by lagoons and micro-filtration).