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

Multiple choice separation of components of mixtures methods of separation elements, compounds and mixtures chemistry

Which of the following processes enable pure water to be obtained from seawater?
I filtration
II distillation
III evaporation

  1. I and II only

  2. I and III only

  3. II and III only

  4. I,II and III
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Distillation and evaporation enables pure water to obtained from seawater,

both these process includes the evaporation of water and then condensing the water vapours to obtain pure form of water.

Multiple choice business organisation and correspondence issues of the environment international efforts for conserving biodiversity effects of pollution on environment government efforts in pollution control

Abatement measures of water pollution is 

  1. Sewage treatment

  2. Septic tank

  3. Green mufflers

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The method abatement of the pollution is generally adopted to reduce the sources of pollution and the impact and its consequences on the environment and health. The sewage treatment plants are set up in the industries which let out high amounts of liquid waste. Physical, chemical, and biological processes are used to remove contaminants and produce treated wastewater. Septic tank is in which sewage is collected and allowed to decompose through bacterial activity. Green muffler involves the plantation of trees to reduce noise pollution because the trees absorb the excessive noise.

Thus, the correct answer is option D. 

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

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

  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)
Reveal answer Fill a bubble to check yourself
D Correct answer
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)'
Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

____________  is the first step of sewage treatment.

  1. Precipitation

  2. Chlorination

  3. Sedimentation

  4. Aeration
Reveal answer Fill a bubble to check yourself
C Correct answer
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. 

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

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.

  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)
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

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

  1. Flocs

  2. Primary sludge

  3. Activated sludge

  4. Anaerobic sludge
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

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?

  1. Oil and grease

  2. Human faeces

  3. Hair

  4. Plastic
Reveal answer Fill a bubble to check yourself
A Correct answer
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'.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

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

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

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

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

  4. (i),(iv),(v), (viii)
Reveal answer Fill a bubble to check yourself
A Correct answer
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)'.
Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

Tertiary treatment of sewage is also known as

  1. Advance Treatment

  2. Preliminary Treatment

  3. Secondary Treatment

  4. Primary Treatment
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Tertiary treatment is the final stage of sewage treatment, involving advanced processes to remove remaining nutrients, chemicals, or pathogens, often referred to as advanced treatment.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

The biological treatment of waste water makes use of

  1. Aerobic bacteria and fungi

  2. Anaerobic bacteria and algea

  3. Aerobic and anaerobic bacteia

  4. Anaerobic bacteria and Eucalyptus leaves
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aerobic digestion of waste is the natural biological degradation and purification process in which bacteria that thrive in oxygen-rich environments break down and digest the waste. During oxidation process, pollutants are broken down into carbon dioxide ( CO$ _{2}$ ), water (H$ _{2}$O), nitrates, sulphates and biomass (microorganisms). By operating the oxygen supply with aerators, the process can be significantly accelerated. Of all the biological treatment methods, aerobic digestion is the most widespread process that is used throughout the world. Anaerobic digestion is a complex biochemical reaction carried out in a number of steps by several types of microorganisms that require little or no oxygen to live. During this process, a gas that is mainly composed of methane and carbon dioxide, also referred to as biogas, is produced. The amount of gas produced varies with the amount of organic waste fed to the digester and temperature influences the rate of decomposition and gas production. Wastewater pollutants are transformed into methane, carbon dioxide and smaller amount of bio-solids. The biomass growth is much lower compared to those in the aerobic processes. They are also much more compact than the aerobic bio-solids.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

Physical treatment for the industrial wastes include sedimentation and filtration.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass. The fluid that passes through is called the filtrate.  Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness).
Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans.
Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

Sewage purification is performed by 

  1. Microbes

  2. Fertilisers

  3. Antibiotics

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

Sewage treatment is done in three stages: primary, secondary and tertiary treatment. Secondary treatment removes dissolved and suspended biological matter, using microorganisms in a controlled environment. Most secondary treatment systems use aerobic bacteria, which consume the organic components of the sewage (sugar, fat, and so on). Some systems use fixed film systems, where the bacteria grow on filters, and the water passes through them. Suspended growth systems use activated sludge, where decomposing bacteria are mixed directly into the sewage. Because oxygen is critical to bacterial growth, the sewage is often mixed with air to facilitate decomposition.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

One of the method for purification of water is sedimentation.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The sedimentation process involves the settling down of particles suspended in water under the effect of gravity. The particles that settle down are known as sediment. In purification of water sedimentation process helps in reducing the concentration of particles in suspension. It is the first step used in the primary treatment of sewage water. 

Thus, the correct answer is option A. 

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

Biological treatment in sewage treatment plant is also known as

  1. Primary treatment

  2. Secondary treatment

  3. Tertiary treatment

  4. Quaternary treatment
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Secondary treatment in a sewage plant relies on the activity of aerobic and anaerobic microorganisms to break down organic matter, hence it is called biological treatment.

Multiple choice biology wastewater story basics of water pollution sewage treatment wastewater treatment - need and methods personal and public cleanliness who will do this? water borne disease hygiene - a key to healthy life

In water treatment plants, the gas used 

  1. Ozone

  2. Carbon dioxide

  3. Nitrogen

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

Carbon dioxide, CO$ _2$, is gaining acceptance for pH control in water treatment plant. It reduces high pH levels quickly. It is not stored as an acid solution so it is considered safer than sulfuric acid. It is non-corrosive to pipes and equipment. It requires less equipment and monitoring costs. It requires no handling costs. It can be utilized via a completely automated system.