Water Microbiology MCQ's

  

MCQ on Water Microbiology

1. The vaporised water is called

a) ground water

b) atmospheric water

c) surface water

d) impounded water

2. The study of marine microbes is called

a) marine microbiology

b) marinology

c) marine bacteriology

d) none of these

3. Microbes found at the bottom of oceans are called

a) limnos

b) phytoplankton

c) benthos

d) zooplankton

4. The floating and drifting microbes are called

a) zooplanktons

b) benthos

c) Planktons

d) none of these

5. The average salinity in oceans is about

a) 10%

b) 3.5%

c) 80%

d) 90%

6. In polluted regions of oceans, a unique species of Clostridium called

a) Clostridium oceanicum is present

b) Clostridium marinine is present

c) Clostridium subtilis is present

d) none of these

7. Major faecal contaminant in potable water is

a) Escherichia coli

b) Streptococcus faecalis

c) both a and b

d) Escherichia coli only

8. IMViC test is carried out to distinguish the presence of

a) E.coli from Clostridium

b) E.coli from Enterobacter aerogenes

c) E.coli from Streptococcus

d) E.coli from other bacteria

9. IMViC test includes

a) Indole test and methyl red test

b) Voges Proskauer test

c) citrate test

d) all of these

10. Disinfection include

a) Chlorination

b) UV radiation

c) ozonation

d) all of the above

11. Sedimentation of large particulate matter is enhanced by

a) Aluminium sulphate

b) Potassium nitrate

c) Potassium permanganate

d) Chlorination

12. High BOD indicates

a) less polluted water

b) less number of organisms

c) more polluted water

d) none of these

13. Oxidation ponds for secondary waste water treatment is designed to promote growth of

a) algae

b) fungi

c) plants

d) bacteria

14. Purification strategies in municipal water supplies involves

a) sedimentation

b) filtration

c) disinfection

d) all of the above

15. Aggregates of microbes as tiny masses in activated sludge process is called

a) activated sludge

b) masses

c) colloidal masses

d) floccules

Answers

1. b) atmospheric water
2. a) marine microbiology
3. c) benthos
4. c) Planktons
5. b) 3.5%
6. a) Clostridium oceanicum is present
7. c) both a and b
8. b) E.coli from Enterobacter aerogenes
9. d) all of these
10. d) all of the above
11. a) Aluminium sulphate
12. c) more polluted water
13. a) algae
14. d) all of the above
15. d) floccules

 Microbiology Questions and Answers – Aquatic Environment

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Aquatic Environment”.

1. The moisture contained in clouds and precipitated as snow,hail,rain etc constitutes _________________
a) Atmospheric water
b) Surface water
c) Groundwater
d) Subterranean water
View Answer

Answer: a
Explanation: The moisture contained in clouds and precipitated as snow, sleet, hail and rain constitutes atmospheric water. The air is washed by atmospheric water.

2. The surface waters are susceptible to contamination with microorganisms from _______________
a) the air
b) the surface runoff
c) precipitation
d) atmospheric water and the surface runoff
View Answer

Answer: d
Explanation: The surface waters are susceptible to contamination with microorganisms from atmospheric water (precipitation), the surface runoff from soil and any wastes deliberately dumped into them.

3. Which of the following is subterranean water?
a) Atmospheric water
b) Surface water
c) Groundwater
d) Rainwater
View Answer

Answer: c
Explanation: Groundwater is subterranean water that occurs where all pores in the soil or rock-containing materials are saturated.

4. Wells less than ___________ deep are considered to be shallow.
a) 1 ft
b) 100 ft
c) 50 ft
d) 1000 ft
View Answer

Answer: b
Explanation: Wells are made by sinking a shaft into the ground to penetrate the groundwater level. Wells less than 100 ft deep are considered to be shallow.

5. Thermus aquaticus, a common bacterial inhabitant generally prevails in temperatures of ____________
a) 00 C
b) 30-400C
c) 70-720C
d) 80-850C
View Answer

Answer: c
Explanation: Thermus aquaticus, a common bacterial inhabitant of hot springs has an optimum growth temperature of 70 to 720C.

6. Hydrostatic pressure increases the boiling point of water but does not change the solubility of nutrients.
a) True
b) False
View Answer

Answer: b
Explanation: Hydrostatic pressure increases the boiling point of water. It affects chemical equilibrium which in turn results in lowering of pH and a change in the solubility of nutrients such as bicarbonate.

7. Primary producers are found growing in which of the following layers of water?
a) upper layer
b) middle layer
c) intermediate layer
d) bottom layer
View Answer

Answer: a
Explanation: In most aquatic habitats the primary producers i.e. algae have their growth restricted to the upper layers of waters through which light can penetrate.

8. The degree of salinity in freshwater is nearly zero.
a) True
b) False
View Answer

Answer: a
Explanation: The degree of salinity in natural waters ranges from near zero in freshwaters to saturation in salt lakes.

9. The microorganisms from lakes and rivers can grow at a salt concentration of _________
a) 2.5 to 4 percent
b) 5 percent
c) below 1 percent
d) above 1 percent
View Answer

Answer: c
Explanation: Microorganisms from lakes and rivers are salt sensitive and do not grow at a salt concentration of more than 1 percent whereas marine microorganisms are halophilic.  

10. Which of the following compounds are required for the growth of saprophytic bacteria and fungi?

a) organic compounds
b) nitrates
c) phosphates
d) mercury
View Answer

Answer: a
Explanation: Organic compounds are required for the growth of saprophytic bacteria and fungi whereas nitrates and phosphates are important for the growth of algae.

Microbiology Questions and Answers – Distribution and Techniques for the Study of Aquatic Microorganisms

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Distribution and Techniques for the Study of Aquatic Microorganisms”.

1. Protozoa and other minute animal life are known as ____________________
a) plankton
b) phytoplankton
c) zooplankton
d) mycoplankton
View Answer

Answer: c
Explanation: The aggregation of floating and drifting microbial life in the surface region of the aquatic ecosystem is called plankton. Protozoa and other minute animal life are known as zooplankton.

Microbiology Questions and Answers – Distribution and Techniques for the Study of Aquatic Microorganisms

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Distribution and Techniques for the Study of Aquatic Microorganisms”.

1. Protozoa and other minute animal life are known as ____________________
a) plankton
b) phytoplankton
c) zooplankton
d) mycoplankton
View Answer

Answer: c
Explanation: The aggregation of floating and drifting microbial life in the surface region of the aquatic ecosystem is called plankton. Protozoa and other minute animal life are known as zooplankton.

2. Microbial inhabitants of the bottom region of a body of water are referred to as                       a) phytoplankton

b) benthic organisms

c) zooplankton

d) mycoplankton

View Answer

Answer: B

Explanation: Microbial inhabitants of the bottom region of a body of water are referred to as the benthic organisms. The richest region of an aquatic system in terms of numbers and kinds of organisms is the benthic region.

3. Phytoplanktonic organisms are non-motile.
a) True
b) False
View Answer

Answer: b
Explanation: Most phytoplanktonic organisms are motile, possess some structural features or contain oil droplets which give them buoyancy.

4. Which of the following places shows the presence of Geothermal vents?
a) Coasts of California
b) Coasts of Peru
c) Galapagos islands
d) Pacific ocean
View Answer

Answer: c
Explanation: It has been calculated that geothermal vents such as the one near the Galapagos Islands account for most of the nutrients dissolved in the oceans of the world.

5. Large spiraling surface currents in the ocean that tend to aggregate and retain nutrients are known as _______________
a) benthic region
b) upwelling
c) geothermal vents
d) gyres
View Answer

Answer: d
Explanation: Gyres are large spiraling surface currents in the ocean that tend to aggregate and retain nutrients, wastes, and microorganisms. Gyres have only been appreciated in recent years, through the use of satellite imagery.

6. Most aquatic microorganisms can grow on the usual laboratory media.
a) True
b) False
View Answer

Answer: b
Explanation: Many aquatic microorganisms will not grow on the usual laboratory media such as nutrient agar or nutrient broth and consequently, cannot be isolated.

7. Which of the following techniques is used for identification and enumeration of algae, bacteria, protozoa?
a) Microscopic examination
b) Submerged-slide technique
c) Membrane-filter technique
d) Enrichment-culture technique
View Answer

Answer: a
Explanation: Microscopic examination for identification and enumeration of algae, bacteria, protozoa, and many fungi is carried out.

8. Which of the following techniques can be used to separate different-size fractions of the aquatic microbial community?
a) submerged-slide technique
b) fluorescent antibody technique
c) membrane-filter technique
d) by measuring biochemical activity
View Answer

Answer: c
Explanation: Membrane-filter technique is applicable for the examination and cultivation of many bacteria from the aquatic environments. It can also be used to separate different-size fractions of the aquatic microbial community.

Microbiology Questions and Answers – Aquatic Microorganisms

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Aquatic Microorganisms.

1. Which of the following zones have considerable rooted vegetation?
a) littoral zone
b) limnetic zone
c) profundal zone
d) benthic zone
View Answer

Answer: a
Explanation: There is usually a fairly large littoral zone along the shore which has considerable rooted vegetation and includes regions where light penetrates to the bottom.

2. Which of the following layer is composed of soft mud or ooze?
a) Photic zone
b) Limnetic zone
c) Benthic zone
d) Profundal zone
View Answer

Answer: c
Explanation: The benthic region is composed of soft mud or ooze at the bottom. Profundal region exists at much greater depths of the water body whereas the littoral zone is present along the shore.

3. In which of the following seasons does the nutrient concentration falls at a drastically lower level?
a) Winter
b) Spring
c) Summer
d) Autumn
View Answer

Answer: c
Explanation: Occurrence of algal blooms during the spring and autumn results in lowering the nutrient concentration during summers.

4. Rapidly expanding urbanization makes it difficult to generalize upon typical microbial flora of streams.
a) True
b) False
View Answer

Answer: a
Explanation: The drastic environmental changes in streams and rivers created by rapidly expanding urbanization on the one hand and changes in farming practices on the other make it impossible to generalize upon typical or characteristic microbial flora.

5. The coastal adjunct of the marine ecosystem is __________________
a) stream
b) estuary
c) river
d) lake
View Answer

Answer: b
Explanation: An estuary is the coastal adjunct of the marine ecosystem. It is a semi-enclosed coastal body of water which has a free connection with the open sea.

Microbiology Questions and Answers – Aquatic Microorganisms

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Aquatic Microorganisms.

1. Which of the following zones have considerable rooted vegetation?
a) littoral zone
b) limnetic zone
c) profundal zone
d) benthic zone
View Answer

Answer: a
Explanation: There is usually a fairly large littoral zone along the shore which has considerable rooted vegetation and includes regions where light penetrates to the bottom.

 2. Which of the following layer is composed of soft mud or ooze?

a) Photic zone
b) Limnetic zone
c) Benthic zone
d) Profundal zone
View Answer

Answer: c
Explanation: The benthic region is composed of soft mud or ooze at the bottom. Profundal region exists at much greater depths of the water body whereas the littoral zone is present along the shore.

3. In which of the following seasons does the nutrient concentration falls at a drastically lower level?
a) Winter
b) Spring
c) Summer
d) Autumn
View Answer

Answer: c
Explanation: Occurrence of algal blooms during the spring and autumn results in lowering the nutrient concentration during summers.

4. Rapidly expanding urbanization makes it difficult to generalize upon typical microbial flora of streams.
a) True
b) False
View Answer

Answer: a
Explanation: The drastic environmental changes in streams and rivers created by rapidly expanding urbanization on the one hand and changes in farming practices on the other make it impossible to generalize upon typical or characteristic microbial flora.

5. The coastal adjunct of the marine ecosystem is __________________
a) stream
b) estuary
c) river
d) lake
View Answer

Answer: b
Explanation: An estuary is the coastal adjunct of the marine ecosystem. It is a semi-enclosed coastal body of water which has a free connection with the open 

 6. The Chesapeake Bay, one of the world’s major estuarine system serves as the receiving basin for how many rivers?

a) 4
b) 6
c) 3
d) 9
View Answer

Answer: d
Explanation: The Chesapeake Bay, one of the world’s major estuarine system serves as the receiving basin for nine major rivers, draining much of southern New York State, Pennsylvania, Maryland and Virginia.

7. In regions of the estuary that are nutritionally poor, it is more likely to find which of the following organisms?
a) coliforms
b) appendaged bacteria
c) viruses
d) fecal streptococci
View Answer

Answer: b
Explanation: In regions of the estuary that are nutritionally poor, one is likely to find the budding and/or the appendaged bacteria, in addition to pseudomonads.

8. The characteristic color of the Red Sea is associated with heavy blooms of __________________
a) diatoms
b) cyanobacteria
c) dinoflagellates
d) chlamydomonads
View Answer

Answer: b
Explanation: The characteristic color of the Red Sea is associated with heavy blooms of a cyanobacterium, Oscillatoria erythraea, which contains the pigments phycoerythrin and phycocyanin.

9. Aquatic bacteria tend to be Gram-negative.
a) True
b) False
View Answer

Answer: a
Explanation: In general, aquatic bacteria tend to be Gram-negative. It is thought that the Gram-negative envelope provides a structure better suited to support life in nutritionally dilute aquatic environments than the Gram-positive cell wall.

10. Which of the following genus of bacteria is not found in fresh waters?
a) Pseudomonas
b) Flavobacterium
c) Aeromonas
d) Vibrio
View Answer

Answer: d
Explanation: Species of the following genera are commonly found in freshwater: Pseudomonas,
Flavobacterium, Aeromonas and Alcaligenes. Vibrio are found in marine or estuarine waters.

Microbiology Questions and Answers – Productivity of Aquatic Microorganisms

« Prev

Next »

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Productivity of Aquatic Microorganisms”.

1. The primary producers in the marine system are ________________
a) protozoa
b) cyanobacteria
c) fungi
d) cyanobacteria and eukaryotic algae
View Answer

Answer: d
Explanation: The primary producers in the marine system are cyanobacteria and eukaryotic algae which predominate in the phytoplankton.

2. The primary producers transform radiant energy into heat energy.
a) True
b) False
View Answer

Answer: b
Explanation: The primary producers through photosynthesis, are capable of transforming radiant energy into chemical energy (organic compounds).

3. The biological activity of an aquatic ecosystem is dependent upon which of the following factors?
a) number of primary producers
b) amount of chemical energy produced
c) rate of primary production
d) number of deaths of organisms
View Answer

Answer: c
Explanation: The biological activity of an aquatic ecosystem is dependent upon the rate of primary production performed by the photosynthetic organisms.

4. n which of the following water bodies, the role of photosynthetic organisms is considerably reduced?
a) Lakes
b) Ponds
c) Estuaries
d) Streams
View Answer

Answer: c
Explanation: In shallow estuaries the role of photosynthetic organisms as primary producers is considerably reduced. Plant growth from the shoreline contributes leaves, stems, and roots of vegetation and other organic detritus.

5. Which of the following aquatic organisms contribute in a small amount to the shallow estuary food web?
a) benthic algae
b) bacteria
c) protozoa
d) nematodes
View Answer

Answer: a
Explanation: Phytoplankton and benthic algae make a small contribution to the food supply in the food web of shallow estuaries.

Microbiology Questions and Answers – Productivity of Aquatic Microorganisms

« Prev

Next »

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Productivity of Aquatic Microorganisms”.

1. The primary producers in the marine system are ________________
a) protozoa
b) cyanobacteria
c) fungi
d) cyanobacteria and eukaryotic algae
View Answer

Answer: d
Explanation: The primary producers in the marine system are cyanobacteria and eukaryotic algae which predominate in the phytoplankton. 

2. The primary producers transform radiant energy into heat energy.

a) True
b) False
View Answer

Answer: b
Explanation: The primary producers through photosynthesis, are capable of transforming radiant energy into chemical energy (organic compounds).

3. The biological activity of an aquatic ecosystem is dependent upon which of the following factors?
a) number of primary producers
b) amount of chemical energy produced
c) rate of primary production
d) number of deaths of organisms
View Answer

Answer: c
Explanation: The biological activity of an aquatic ecosystem is dependent upon the rate of primary production performed by the photosynthetic organisms.

4. n which of the following water bodies, the role of photosynthetic organisms is considerably reduced?
a) Lakes
b) Ponds
c) Estuaries
d) Streams
View Answer

Answer: c
Explanation: In shallow estuaries the role of photosynthetic organisms as primary producers is considerably reduced. Plant growth from the shoreline contributes leaves, stems, and roots of vegetation and other organic detritus.

5. Which of the following aquatic organisms contribute in a small amount to the shallow estuary food web?
a) benthic algae
b) bacteria
c) protozoa
d) nematodes
View Answer

Answer: a
Explanation: Phytoplankton and benthic algae make a small contribution to the food supply in the food web of shallow estuaries.

6. Which among the following are referred to as the “pasture of the sea”?

a) fishes
b) algae
c) nematodes
d) phytoplankton
View Answer

Answer: d
Explanation: Plankton, particularly phytoplankton, has been referred to as the “pasture of the sea”. Fish, whales, and squids feed directly on plankton or on larger plankton-feeding animals.

7. The term fertility of oceans is used to express the capacity for the production of inorganic matter.
a) True
b) False
View Answer

Answer: b
Explanation: The term fertility of oceans is used to express the capacity for the production of organic matter by the organisms present in these waters.

8. What amount of dry organic matter is produced by deep ocean areas?
a) 1g
b) 10g
c) 0.5g
d) 100g
View Answer

Answer: c
Explanation: The terrestrial environment produces 1 to 10 g of dry organic matter per square meter per day compared to 0.5 g for the deep ocean areas.

9. Which among the following factors are limiting the growth of phytoplankton organisms?
a) carbon dioxide
b) radiant energy
c) water
d) radiant energy,nitrogen
View Answer

Answer: d
Explanation: The factors generally limiting growth are radiant energy, nitrogen and phosphorus, and the trace elements. The nitrogen, phosphorus and trace elements are made available through the mineralization reactions of microorganisms.

10. Which among the following oceans is the most richest in life?
a) Antarctic Ocean
b) Atlantic Ocean
c) Pacific Ocean
d) Indian Ocean
View Answer

Answer: a
Explanation: The Antarctic Ocean is described as being richer in life than any other major oceanic area. The richness of nutrients in this region is attributable to the mixing of the waters of the Atlantic, Pacific, and Indian Oceans.

11. In which of the following water bodies, fertility is high?
a) open sea
b) coastal regions
c) lakes
d) rivers
View Answer

Answer: b
Explanation: Although coastal and estuarine regions provide a less stable physical environment, their fertility exceeds that of the open sea because of the large amounts of nutrients available.

12. Which of the following product is not obtained from dissimilation of organic matter under aerobic conditions?
a) ammonium
b) sulphate
c) methane
d) phosphate
View Answer

Answer: c
Explanation: Under aerobic conditions the principal products resulting from dissimilation of organic compounds are ammonium, carbon dioxide, sulphate, and phosphate.

13. Which of the following organism have siliceous skeletons?
a) Foraminifera
b) Coccolithophores
c) Radiolaria
d) Cyanobacteria
View Answer

Answer: c
Explanation: Radiolaria and silicoflagellates have siliceous skeletons whereas foraminifera and coccolithophores produce calcareous skeletons.

Microbiology Questions and Answers – Determining Sanitary Quality of Water

«

»

This set of Microbiology online test focuses on “Determining Sanitary Quality of Water”.

1. Which of the following forms of water is the most contaminated?
a) Underground water
b) Rainwater
c) Surface water
d) Water stored in ice caps
View Answer

Answer: c
Explanation: Surface water should not be used for drinking purposes unless it is subjected to purification since there is constant danger of contamination and consequent transmission of disease.

2. Alum is used for which of the following purification process?
a) Sedimentation
b) Filtration
c) Disinfection
d) Ozonation
View Answer

Answer: a
Explanation: Sedimentation is enhanced by addition of alum (aluminum sulphate) at the treatment plant, which produces a sticky flocculent precipitate.

3. The potability of water can be checked by sanitary surveys.
a) True
b) False
View Answer

Answer: b
Explanation: Sanitary surveys reveal whether water is being produced under conditions in which potable water would ordinarily be produced. However, potability can be determined only by chemical and bacteriological laboratory tests.

4. The coliform group of bacteria includes all the __________________ bacilli.
a) aerobic
b) anaerobic
c) aerobic, non-sporulating
d) aerobic, gram-negative, non-sporulating
View Answer

Answer: d
Explanation: The coliform group of bacteria includes all the aerobic and facultatively anaerobic, gram-negative, non-sporulating bacilli that produce acid and gas from the fermentation of lactose.

5. Which of the following organism does not belong to coliform group of bacteria?
a) Salmonella
b) Serratia
c) Enterobacter
d) Proteus
View Answer

Answer: c
Explanation: Coliform group of bacteria consists of E.coli and Enterobacter aerogenes. All others belong to the enteric group.

6. Coliforms are natural inhabitants of the large intestine of human and animals.
a) True
b) False
View Answer

Answer: a
Explanation: Coliforms, fecal streptococci and Clostridium perfringens are normal inhabitants of the large intestine of humans and other animals and are consequently present in feces.

7. Which of the following acts as a carbon source for Enterobacter aerogenes?
a) Peptone
b) Sodium citrate
c) Yeast extract
d) Tryptone
View Answer

Answer: b
Explanation: Enterobacter aerogenes will grow in a chemically defined medium in which sodium citrate is the only carbon compound as it is capable of utilizing it.

8. What will be the plate count of good quality water?
a) 10 per ml
b) 50 per ml
c) 100 per ml
d) 1000 per ml
View Answer

Answer: c
Explanation: In the standard plate count method, water of good quality is expected to give a low count, less than 100 per ml.

9. Among the following which microorganism acts as a representative of fecal streptococci group?
a) Streptococcus faecalis
b) Streptococcus bovis
c) Streptococcus equinus
d) Streptococcus faecium
View Answer

Answer: a
Explanation: Streptococcus faecalis is representative of the fecal streptococci group and are abundantly present in the large intestine of humans. Their occurrence in water is indicative of fecal pollution.

10. Thiobacillus can produce an acidity in the range of pH __________
a) 7
b) 5
c) 3
d) 1
View Answer

Answer: d
Explanation: Organisms of the genus Thiobacillus oxidize elemental sulphur to sulphuric acid and can produce acidity in the range of pH 1.

11. In which of the following organism does iron secreted to form stalks or ribbons attached to the cell?
a) Sphaerotilus
b) Gallionella
c) Thiobacillus
d) Streptococcus
View Answer

Answer: b
Explanation: Some iron bacteria such as Gallionella transform soluble compounds of iron to insoluble compounds of iron which are secreted to form stalks or ribbons attached to the cell.

Microbiology Questions and Answers – Wastewater and Treatment Processes

»

This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Wastewater and Treatment Processes”.

1. Which of the following sewerage systems carry domestic and industrial wastewater?
a) sanitary sewers
b) storm sewers
c) combined sewers
d) storm and combined sewers
View Answer

Answer: a
Explanation: Sanitary sewers carry domestic and industrial wastewater for its ultimate treatment and disposal.

2. The more oxidizable organic material, the lesser the BOD.
a) True
b) False
View Answer

Answer: b
Explanation: The magnitude of the BOD is related to the amount of organic material in the wastewater-i.e., the more oxidizable organic material, the higher the BOD.

3. Which of the following is a strict anaerobe?
a) Enterobacter
b) Alcaligenes
c) Pseudomonas
d) Methanosarcina
View Answer

Answer: d
Explanation: Methane producers are strict anaerobes e.g., Methanobacterium, Methanosarcina, Methanococcus. They produce methane and carbon dioxide as end products.

4. In which of the following treatment involve oxidation of organic constituents of the wastewater?
a) Primary treatment
b) Secondary treatment
c) Advanced treatment
d) Final treatment
View Answer

Answer: b
Explanation: Secondary or biological treatment is done to adsorb and ultimately oxidize organic constituents of the wastewater, i.e, to reduce the BOD.

5. The upper region of the trickling filter is favorable for the growth of _____________
a) fungi
b) protozoa
c) algae
d) bacteria
View Answer

Answer: c
Explanation: The upper region of the trickling filter is favorable for the growth of algae, and at times their growth may become so extensive that it impairs the operation of the filter.

6. Activated sludge usually employs an aeration period of ________________
a) 1 hour
b) 24 hours
c) 10-15 hours
d) 4-8 hours
View Answer

Answer: d
Explanation: The activated sludge process usually employs an aeration period of 4 to 8 hours, after which the mixture is piped to a sedimentation tank.

7. Oxidation ponds are very deep ponds.
a) True
b) False
View Answer

Answer: b
Explanation: Oxidation ponds also called lagoons are shallow ponds which are 2 to 4 ft in depth designed to allow algal growth on the wastewater effluent.

8. Trickling filter is used in which of the following wastewater treatment processes?
a) Primary treatment
b) Secondary treatment
c) Advanced treatment
d) Final treatment
View Answer

Answer: b
Explanation: The trickling filter is used in secondary treatment in which a stationary microbial culture is fed by a continuous supply of nutrients. It is used for filtration processes.

9. Belt filter presses are used in which of the following process?
a) Thickening
b) Stabilization
c) Dewatering
d) Disposal
View Answer

Answer: c
Explanation: Dewatering is done by vacuum filters, belt filter presses and centrifuges and is often enhanced by the addition of polymer or other chemical coagulant aids.

10. Which of the following gases are produced in large amounts during sludge digestion?
a) methane
b) carbon-dioxide
c) hydrogen
d) nitrogen
View Answer

Answer: a
Explanation: About 60-70% methane is produced during sludge digestion with smaller amounts of carbon dioxide, hydrogen and nitrogen.