civil engineering MCQs – Page 88

Practise multiple-choice questions from civil engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

civil engineering Mcqs
4351. The settling velocity of a particle in a sedimentation tank increases if_________________?
comments icon0

A. the depth of tank is decreased

B. particle size is decreased

C. none of the above

D. the surface area of tank is increased

4352. When there is no recirculation of sewage, then recirculation factor is_______________?
comments icon0

A. 0

B. 1

C. infinity

D. none of the above

4353. Which of the following retards the self purification of stream ?
comments icon0

A. higher temperature

B. sunlight

C. none of the above

D. satisfying oxygen demand

4354. The amount of coagulant needed for coagulation of water increases with_______________?
comments icon0

A. correct answer is?

B. decrease in turbidity of water

C. increase in turbidity of water

D. decrease in temperature of water</strong>

E. increase in temperature of water

4355. As compared to rapid sand filters, slow sand filters give______________?
comments icon0
A. slower filtration rate

B. lesser efficiency in removal of bacteria

C. higher efficiency in removal of bacteria </strong>

D. higher filtration rate

E. correct answer is?

4356. The major disadvantage of lime soda process of water softening is that_________________?
comments icon0
A. huge amount of precipitate is formed which creates a disposal problem

B. the effluent cannot be reduced to zero hardness

C. it is unsuitable for turbid and acidic water

D. it is unsuitable for softening the water of excessive hardness

4357. Disinfection efficiency is________________?
comments icon0

A. increased at higher pH value of water

B. highest at pH value equal to 7

C. unaffected by pH value of water

D. reduced at higher pH value of water
4358. Chlorine demand of water is equal to________________?
comments icon0

A. sum of applied and residual chlorine

B. residual chlorine

C. applied chlorine

D. difference of applied and residual chlorine
4359. The depression of water table in a well due to pumping will be maximum_______________?
comments icon0
A. close to the well

B. re R is the radius of influence

C. at a distance R/2 from the well

D. none of the above

E. at a distance R from the well

4360. A sewer that receives the discharge of a number of house sewers is called________________?
comments icon0

A. intercepting sewer

B. submain sewer

C. lateral sewer

D. house sewer

4361. The type of sewer which is suitable for both combined and separate system is_____________?
comments icon0

A. circular sewer

B. horse-shoe type sewer

C. egg shaped sewer

D. semi-elliptical sewer

4362. The working conditions in imhoff tanks are_______________?
comments icon0

A. aerobic in lower compartment and anaerobic in upper compartment

B. aerobic only

C. anaerobic in lower compartment and aerobic in upper compartment

D. anaerobic only

4363. Most of the bacteria in sewage are______________?
comments icon0
A. saprophytic

B. parasitic

C. anaerobic

D. pathogenic

4364. As compared to higher pH values, the contact period required for efficient chlorination at lower pH values is___________________?
comments icon0
A. smaller

B. same

C. none of the above

D. larger

4365. Ground water is usually free from________________?
comments icon0
A. suspended impurities

B. dissolved impurities

C. both suspended and dissolved impurities

D. none of the above

4366. If the total hardness of water is greater than its total alkalinity, the carbonate hardness will be equal to________________?
comments icon0

A. total hardness total alkalinity

B. total alkalinity

C. total hardness

D. non carbonate hardness

4367. Generally the detention period for grit chambers is kept as_______________?
comments icon0

A. 12 hours

B. 2-4 hours

C. 1 minute

D. 5 minutes

4368. Alum as a coagulant is found to be most effective when pH range of water is______________?
comments icon0

A. 2 to 4

B. 8 to 10

C. 4 to 6

D. 6 to 8
4369. The pathogens can be killed by_______________?
comments icon0
A. chlorination

B. none of the above

C. nitrification

D. oxidation

4370. The ratio of 5 day BOD to ultimate BOD is about_______________?
comments icon0

A. 3-Jan

B. 4-Mar

C. 1

D. 2/3
4371. Corrosion in concrete sewers is caused by______________?
comments icon0

A. dissolved oxygen

B. chlorine

C. nitrogen

D. septic conditions
4372. Which of the following compounds is widely used for algae control ?
comments icon0

A. sodium sulphate

B. copper sulphate

C. sodium chloride

D. calcium chloride

4373. The maximum discharge of a tube-well is about_________________?
comments icon0
A. 50 litres/sec

B. 500 litres/sec

C. 1000 litres/see

D. 5 litres/sec

4374. Facultative bacteria are able to work in________________?
comments icon0

A. presence of oxygen only

B. absence of oxygen only

C. presence of water

D. presence as well as in absence of oxygen
4375. Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters. Reason R : The sand used in slow sand filters is finer than that in rapid sand filters. Select your answer based on the coding system given below?
comments icon0
A. Both A and R are true and R is the correct explanation of A

B. Both A and R are true but R is not the correct explanation of A

C. A is true but R is false

D. A is false but R is true

4376. The design discharge for the combined sewer system shall be taken as________________?
comments icon0
A. rainfall + 2 DWF

B. rainfall + 6 DWF

C. equal to rainfall

D. rainfall + DWF

4377. Percentage of bacterial load that can be removed from water by the process of plain sedimentation is about_______________?
comments icon0

A. 100

B. 75

C. 10 to 25

D. 50

4378. The hydraulic mean depth (HMD. for an egg-shaped sewer flowing two-third full is_______________?
comments icon0

A. none of the above

B. less than HMD when flowing full

C. greater than HMD when flowing full

D. equal to HMD when flowing full

4379. The disinfection efficiency of chlorine increases by_______________?
comments icon0
A. decreasing the time of contact

B. decreasing the temperature of water

C. increasing the temperature of water</strong>

D. correct answer is ?

E. only (1)

F. both (1) and (2)

4380. The most common cause of acidity in water is_______________?
comments icon0

A. nitrogen

B. oxygen

C. carbon dioxide

D. hydrogen

4381. Residual chlorine in water is determined by________________?
comments icon0

A. starch iodide method

B. orthotolidine method

C. both (A) and (B)

D. none of the above

4382. The suitable method for disinfection of swimming pool water is________________?
comments icon0

A. lime treatment

B. by using potassium permanganate

C. chlorination

D. ultra violet rays treatment
4383. The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of________________?
comments icon0

A. 100 mg/litre

B. 1000 mg/litre

C. 1 mg/litre

D. 10 mg/litre
4384. The suitable system of sanitation for area of distributed rainfall throughout the year with less intensity is_________________?
comments icon0

A. partially separate system

B. combined system

C. separate system

D. partially combined system

4385. The rate of filtration in slow sand filters in million litres per day per hectare is about_____________?
comments icon0
A. 50 to 60

B. 100 to 150

C. 1400 to 1500

D. 500 to 600

4386. The minimum and maximum diameters of sewers shall preferably be_________________?
comments icon0
A. 15 cm and 300 cm

B. 15 cm and 100 cm

C. 30 cm and 450 cm

D. 60 cm and 300cm

4387. The main disadvantage of cement concrete sewers is________________?
comments icon0
A. difficulty in transportation due to heavy weight

B. difficulty in construction

C. less strength

D. less life

4388. Orthotolidine test is used for determination of________________?
comments icon0
A. residual chlorine

B. dissolved oxygen

C. biochemical oxygen demand

D. dose of coagulant

4389. The process of lagooning is primarily a means of________________?
comments icon0

A. increasing the capacity of storage re-servoirs

B. reducing the excessive flow in sewers

C. increasing flow of sewage through imhoff tanks

D. disposing of sludge
4390. Sewage treatment units are designed for_______________?
comments icon0
A. average flow only

B. maximum and minimum flow

C. maximum flow only

D. minimum flow only

4391. The type of valve, which is provided on the suction pipe in a tube-well, is____________?
comments icon0

A. air relief valve

B. pressure relief valve

C. reflux valve

D. sluice valve

4392. The correct relation between theoretical oxygen demand (TOD), Biochemical oxygen demand (BOD) and Chemical oxygen demand (COD) is given by_______________?
comments icon0
A. TOD>COD>BOD

B. TOD>BOD>COD

C. COD>BOD>TOD

D. BOD>COD>TOD

4393. Double filtration is used_______________?
comments icon0
A. to increase the filtration slow sand filters capacity of

B. for isolated buildings like pools, hotels etc swimming

C. all of the above

D. to increase the filtration rapid sand filters capacity of

4394. The overflow rate for plain sedimentation tanks is about__________________?
comments icon0
A. 500 to 750 litres/hour/ m2

B. 1500 to 2000 litres/hour/m2

C. 1000 to 1250 litres/hour/ m2

D. 1250 to 1500 litres/hour/m2

4395. The chemical most commonly used to increase speed of sedimentation of sewage is_______________?
comments icon0

A. sodium permanganate

B. copper sulphate

C. sulphuric acid

D. lime
4396. Composting and lagooning are the methods of_______________?
comments icon0

A. sedimentation

B. sludge disposal

C. sludge digestion

D. filtration

4397. The characteristics of fresh and septic sewage respectively are____________________?
comments icon0

A. acidic and alkaline

B. alkaline and acidic

C. both acidic

D. both alkaline

4398. Standard BOD is measured at________________?
comments icon0
A. 20C 5day

B. 25C- 3day

C. 20C 1day

D. 30C- 5day

4399. The time of concentration is defined as_______________?
comments icon0
A. sum of (A) and (B)

B. the time taken by rainfall water to run from most distant point of water shed to the inlet of sewer

C. the time required for flow of water in sewer to the point under consideration

D. difference of (A) and (B)

4400. Sewerage system is usually designed for_________________?
comments icon0

A. 10 years

B. 25 years

C. 75 years

D. 50 years