civil engineering Mcqs
4351. The polluted water is one which_______________?
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A. contains pathogenic bacteria

B. consists of undesirable substances rendering it unfit for drinking and domestic use

C. is contaminated

D. is safe and suitable for drinking and domestic use

4352. The settling velocity of a particle in a sedimentation tank increases if_________________?
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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

4353. When there is no recirculation of sewage, then recirculation factor is_______________?
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A. 0

B. 1

C. infinity

D. none of the above

4354. Which of the following retards the self purification of stream ?
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A. higher temperature

B. sunlight

C. none of the above

D. satisfying oxygen demand

4355. The amount of coagulant needed for coagulation of water increases with_______________?
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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

4356. As compared to rapid sand filters, slow sand filters give______________?
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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?

4357. The major disadvantage of lime soda process of water softening is that_________________?
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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

4358. Disinfection efficiency is________________?
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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
4359. Chlorine demand of water is equal to________________?
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A. sum of applied and residual chlorine

B. residual chlorine

C. applied chlorine

D. difference of applied and residual chlorine
4360. The depression of water table in a well due to pumping will be maximum_______________?
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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

4361. A sewer that receives the discharge of a number of house sewers is called________________?
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A. intercepting sewer

B. submain sewer

C. lateral sewer

D. house sewer

4362. The type of sewer which is suitable for both combined and separate system is_____________?
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A. circular sewer

B. horse-shoe type sewer

C. egg shaped sewer

D. semi-elliptical sewer

4363. The working conditions in imhoff tanks are_______________?
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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

4364. Most of the bacteria in sewage are______________?
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A. saprophytic

B. parasitic

C. anaerobic

D. pathogenic

4365. As compared to higher pH values, the contact period required for efficient chlorination at lower pH values is___________________?
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A. smaller

B. same

C. none of the above

D. larger

4366. Ground water is usually free from________________?
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A. suspended impurities

B. dissolved impurities

C. both suspended and dissolved impurities

D. none of the above

4367. If the total hardness of water is greater than its total alkalinity, the carbonate hardness will be equal to________________?
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A. total hardness total alkalinity

B. total alkalinity

C. total hardness

D. non carbonate hardness

4368. Generally the detention period for grit chambers is kept as_______________?
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A. 12 hours

B. 2-4 hours

C. 1 minute

D. 5 minutes

4369. Alum as a coagulant is found to be most effective when pH range of water is______________?
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A. 2 to 4

B. 8 to 10

C. 4 to 6

D. 6 to 8
4370. The pathogens can be killed by_______________?
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A. chlorination

B. none of the above

C. nitrification

D. oxidation

4371. The ratio of 5 day BOD to ultimate BOD is about_______________?
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A. 3-Jan

B. 4-Mar

C. 1

D. 2/3
4372. Corrosion in concrete sewers is caused by______________?
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A. dissolved oxygen

B. chlorine

C. nitrogen

D. septic conditions
4373. Which of the following compounds is widely used for algae control ?
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A. sodium sulphate

B. copper sulphate

C. sodium chloride

D. calcium chloride

4374. The maximum discharge of a tube-well is about_________________?
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A. 50 litres/sec

B. 500 litres/sec

C. 1000 litres/see

D. 5 litres/sec

4375. Facultative bacteria are able to work in________________?
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A. presence of oxygen only

B. absence of oxygen only

C. presence of water

D. presence as well as in absence of oxygen
4376. 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?
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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

4377. The design discharge for the combined sewer system shall be taken as________________?
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A. rainfall + 2 DWF

B. rainfall + 6 DWF

C. equal to rainfall

D. rainfall + DWF

4378. Percentage of bacterial load that can be removed from water by the process of plain sedimentation is about_______________?
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A. 100

B. 75

C. 10 to 25

D. 50

4379. The hydraulic mean depth (HMD. for an egg-shaped sewer flowing two-third full is_______________?
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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

4380. The disinfection efficiency of chlorine increases by_______________?
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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)

4381. The most common cause of acidity in water is_______________?
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A. nitrogen

B. oxygen

C. carbon dioxide

D. hydrogen

4382. Residual chlorine in water is determined by________________?
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A. starch iodide method

B. orthotolidine method

C. both (A) and (B)

D. none of the above

4383. The suitable method for disinfection of swimming pool water is________________?
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A. lime treatment

B. by using potassium permanganate

C. chlorination

D. ultra violet rays treatment
4384. The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of________________?
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A. 100 mg/litre

B. 1000 mg/litre

C. 1 mg/litre

D. 10 mg/litre
4385. The suitable system of sanitation for area of distributed rainfall throughout the year with less intensity is_________________?
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A. partially separate system

B. combined system

C. separate system

D. partially combined system

4386. The rate of filtration in slow sand filters in million litres per day per hectare is about_____________?
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A. 50 to 60

B. 100 to 150

C. 1400 to 1500

D. 500 to 600

4387. The minimum and maximum diameters of sewers shall preferably be_________________?
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A. 15 cm and 300 cm

B. 15 cm and 100 cm

C. 30 cm and 450 cm

D. 60 cm and 300cm

4388. The main disadvantage of cement concrete sewers is________________?
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A. difficulty in transportation due to heavy weight

B. difficulty in construction

C. less strength

D. less life

4389. Orthotolidine test is used for determination of________________?
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A. residual chlorine

B. dissolved oxygen

C. biochemical oxygen demand

D. dose of coagulant

4390. The process of lagooning is primarily a means of________________?
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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
4391. Sewage treatment units are designed for_______________?
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A. average flow only

B. maximum and minimum flow

C. maximum flow only

D. minimum flow only

4392. The type of valve, which is provided on the suction pipe in a tube-well, is____________?
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A. air relief valve

B. pressure relief valve

C. reflux valve

D. sluice valve

4393. The correct relation between theoretical oxygen demand (TOD), Biochemical oxygen demand (BOD) and Chemical oxygen demand (COD) is given by_______________?
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A. TOD>COD>BOD

B. TOD>BOD>COD

C. COD>BOD>TOD

D. BOD>COD>TOD

4394. Double filtration is used_______________?
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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

4395. The overflow rate for plain sedimentation tanks is about__________________?
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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

4396. The chemical most commonly used to increase speed of sedimentation of sewage is_______________?
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A. sodium permanganate

B. copper sulphate

C. sulphuric acid

D. lime
4397. Composting and lagooning are the methods of_______________?
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A. sedimentation

B. sludge disposal

C. sludge digestion

D. filtration

4398. The characteristics of fresh and septic sewage respectively are____________________?
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A. acidic and alkaline

B. alkaline and acidic

C. both acidic

D. both alkaline

4399. Standard BOD is measured at________________?
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A. 20C 5day

B. 25C- 3day

C. 20C 1day

D. 30C- 5day

4400. The time of concentration is defined as_______________?
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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)