Waste Water Engineering Multiple Choice Questions on “Nitrogen Removal”.
1. What is the oxidation state of organic nitrogen? a) -2 b) -1 c) -3 d) +3 Answer: c Clarification: The oxidation state of organic nitrogen is – 3, Ammonia is – 3, Ammonium ion is – 3, gas Nitrogen gas is 0, Nitrous oxide is +1, Nitric oxide is +2, Nitrite ion is +3 and Nitrogen dioxide is +4.
2. Which of the following below represents nitrate ion? a) NO2 b) NO3– c) NO– d) NO2– Answer: b Clarification: Organic nitrogen is represented by N, ammonia is represented by NH3, nitrate ion is represented by NO3– and nitrite ion is represented by NO2–. The oxidation state of nitrate ion is +5.
3. Nitrogen fixation is the conversion of _________into nitrogen compounds. a) Ammonia b) Nitric oxide c) Nitrate d) Nitrogen gas Answer: d Clarification: Nitrogen fixation is the conversion of nitrogen gas into nitrogen compounds that can be assimilated by plants. Biological fixation is the most common, but fixation can also occur by lightning and through an industrial process.
4. ______ is the biochemical degradation of Organic-N into NH3 or NH4+. a) Nitrogen fixation b) Ammonification c) Nitrification d) Denitrification Answer: b Clarification: Ammonification is the biochemical degradation of Organic-N into NH3 or NH4+ by heterotrophic bacteria under aerobic or anaerobic conditions.
5. Which of the following bacteria is used in nitrification process? a) Escherichia coli b) Nitrosomonas c) Morganella d) Providencia Answer: b Clarification: Nitrification is the biological oxidation of NH4+ to NO3– through a two-step autotrophic process by the bacteria Nitrosomonas and Nitrobacter.
6. What is the minimum mass loading of nitrogen in domestic wastewater? a) 2 lbs b) 4 lbs c) 6 lbs d) 8 lbs Answer: b Clarification: The mass loading of nitrogen in domestic wastewater averages from 4 to 18 lbs of Total -N per capita per year. Untreated domestic wastewater typically contains 20 to 85 mg/L Total –N.
7. What is the minimum quantity of nitrogen present in untreated wastewater? a) 5 mg/L b) 10 mg/L c) 15 mg/L d) 20 mg/L Answer: d Clarification: Untreated domestic wastewater typically contains 20 to 85 mg/L Total -N, with the majority occurring as a mixture of NH3 – N/NH4+ – N (12 -50 mg/L) and Organic -N (8 -35 mg/L).
8. Excess nitrogen is present after secondary biological treatment. a) True b) False Answer: a Clarification: Because the carbon to nitrogen ratio of wastewater is typically on the order of 4:1 to 6:1, there will be excess nitrogen after secondary biological treatment that cannot be assimilated by micro-organisms.
9. The maximum removal of nitrogen from septic tanks is 15%. a) True b) False Answer: b Clarification: The removal of Total -N within septic tanks is on the order of 10 to 30%, with the majority being removed as particulate matter through sedimentation or flotation process.
10. What is the percentage of nitrogen removal that can be obtained from facultative lagoons? a) 50% b) 65% c) 85% d) 95% Answer: d Clarification: The pH fluctuates as a result of the algae carbonate interactions in the lagoon, so wastewater alkalinity is important. Under ideal 4 conditions, up to 95% nitrogen removal can be achieved from facultative wastewater stabilization lagoons.
11. What is the power consumed for the anoxic process for the removal of nitrogen? a) 0.5-1.5 hrs b) 1.5-2 hrs c) 2-4 hrs d) 4-8 hrs Answer: a Clarification: The retention time considered for the aerobic zone for the AO process for removing phosphorus is 0.5-1.5 hrs. This process involves aerobic oxidation followed by anaerobic digestion. This is a very effective method to remove phosphorus compounds.
12. What is the retention time considered for the anaerobic zone for the AO process for removing phosphorus? a) 1-3 hrs b) 3-5 hrs c) 5-8 hrs d) 8-11 hrs Answer: a Clarification: The retention time considered for the anaerobic zone for the AO process for removing phosphorus is 1-3 hrs. This process involves aerobic oxidation followed by anaerobic digestion. This is a very effective method to remove phosphorus compounds.
13. What is the SDNR assumed while designing postanoxic tank? a) 0.1-0.4 b) 1.5-2 c) 0.8-1 d) 3-4 Answer: a Clarification: The SDNR assumed while designing postanoxic tank is 0.1-0.4. Denitrifying bacteria exist in order to remove nitrogen biologically. The value for SDNR is different for a preanoxic tank.
14. How is the SDNR related to the BOD? a) SDNR = 0.03 F/M b) SDNR = 0.3 F/M c) SDNR = 0.03/( F/M) d) SDNR = 3 F/M Answer: a Clarification: SDNR = 0.03 F/M. This is how SDNR is related to F/M. BOD actually represents the F/M.
15. At what detention time maximum saturation rates are experienced in a denitrification process? a) 10-20 mins b) 72 mins c) 30-40 mins d) 22-24 mins Answer: a Clarification: When the detention time is 10-20 mins saturation rates are expected in a denitrification process. In this case, the F/M ratio will be very high. The rbCOD also would be very high.
16. When is internal recirculation required for preanoxic tank? a) SDNR<1 b) SDNR=1 c) SDNR =2-4 d) SDNR =4-6 Answer: a Clarification: The internal recirculation is not required if SDNR<1. Any value of SDNR>1 requires internal recirculation. Internal recirculation value is usually between 2-4.
17. What is the retention time considered for an anoxic zone for the removal of nitrogen for modified Ludzack Ettinger treatment system? a) 1-3 hrs b) 3-4 hrs c) 4-8 hrs d) 8-12 hrs Answer: a Clarification: The retention time considered for an anoxic zone for the modified Ludzack Ettinger system is 1-3 hrs. This treatment is used to remove nitrogen. This also aids in removing BOD.
18. What is the residential time considered for the sequence batch reactor for the removal of nitrogen? a) 42-45 days b) 10-32 days c) 32-52 days d) 52-72 days Answer: b Clarification: The residential time considered for the sequence batch reactor for the removal of nitrogen is 10-32 days. This SBR is the process which consumes very less space. The whole process takes place in a single tank.
19. While designing SBR for the removal of nitrogen what is the MLVSS in mg/L assumed? a) 3000-500 b) 7000-9000 c) 9000-10000 d) 60000 Answer: a Clarification: While designing SBR for the removal of nitrogen what is the MLVSs assumed is 2000-5000 mg/L. Based on this the tank size is derived. The total retention time considered for the removal of nitrogen by SBR is 20-30 hrs.
Waste Water Engineering Multiple Choice Questions on “Ion Exchange Design”.
1. The breakthrough curves for ion exchange column and adsorption column are dissimilar. a) True b) False Answer: b Clarification: The breakthrough curves for an ion exchange column and an adsorption column are similar. The contacting techniques are almost identical. The same procedures used for the design of adsorption columns may be used for ion exchange columns.
2. The area ________ the breakthrough curve is equal to the maximum amount of ions removed by the column. a) Above b) Below c) At d) Above and below Answer: a Clarification: At complete exhaustion, C = Co and the area above the breakthrough curve is equal to the maximum amount of ions removed by the column. At complete exhaustion, the entire exchange column is in equilibrium with the influent and effluent flows.
3. Macroporous resins are required for demineralisation. a) True b) False Answer: b Clarification: Macroporous resins are normally not required for demineralisation or softening. All styrenic WBA resins are Macroporous. Special particle sizes are required depending on the design technology.
4. What is the acceptable pressure drop at maximum flow rate? a) 0.5 bar b) 1.5 bar c) 2 .5 bar d) 3.5 bar Answer: b Clarification: There is no limit in height, except that the pressure drop at the maximum flow rate should not exceed 100 to 150 kPa (1 to 1.5 bars) at maximum flow rate with clean resins.
5. What is the minimum flow rate for SAC resins? a) 25 m/h b) 30 m/h c) 40 m/h d) 50 m/h Answer: a Clarification: For SAC resins, that have the highest specific gravity, the linear flow rate must be comprised between 25 and about 70 m/h (at about 20 °C). Other resins have a lower specific gravity and are compacted at a lower flow rate, the minimum being about 16 m/h.
6. What is the maximum silica content in treated water from a regeneration system? a) 10 µg/L b) 15 µg/L c) 20 µg/L d) 25 µg/L Answer: d Clarification: To a minor extent, temperature may affect the residual silica leakage in the treated water at temperatures higher than about 50 °C; silica is hardly removed by strongly basic anion exchange resins.
7. The production run should be _______ the regeneration process. a) Shorter than b) Longer than c) Equal to d) Nearer to Answer: d Clarification: The practical limit is that the production run should be at least as long as the regeneration process. As most ion exchange systems are regenerated automatically, the duration of the production run does not have to be “at least one day” as was the rule at the time (many decades ago) when the morning shift would regenerate manually every day at 7 o’clock. Efficient systems have been designed with running times as short as 3 hours.
8. What is the minimum flow rate for water treatment? a) 5 m3/h per m3 of resin b) 10 m3/h per m3 of resin c) 15 m3/h per m3 of resin d) 20 m3/h per m3 of resin Answer: a Clarification: The minimum flow rate for water treatment is 5 m3/h/m3 of resin and the maximum flow rate is 50 m3/h/m3 of resin.
9. What is the maximum operating flow for mixed bed units? a) 12 BV/h b) 13 BV/h c) 14 BV/h d) 15 BV/h Answer: d Clarification: Specific flow rate is between 5 and 50 bed volumes per hour (BV/h) and operating flow is a minimum of 12-15 BV/h. The system should be made as small as possible for economical reasons.
10. Which is the year zeolite was used as ion exchange water softeners? a) 1900 b) 1905 c) 1925 d) 1945 Answer: b Clarification: In 1905, Gans, a German chemist, used synthetic aluminosilicate materials known as zeolites in the first ion exchange water softeners. Although aluminosilicate materials are rarely used today, the term “zeolite softener” is commonly used to describe any cation exchange process.
11. _________resins can neutralize strong bases. a) SAC b) WAC c) SBA d) WBA Answer: a Clarification: SAC stands for Strong Acid Cation. SAC resins can neutralize strong bases and convert neutral salts into their corresponding acids. SBA resins can neutralize strong acids and convert neutral salts into their corresponding bases. These resins are utilized in most softening and full demineralization applications.
12. Calculate the amount of resin required for the following information. Cation Load: 10 ppm as CaCO3 Capacity: 47 Kg/m3 Correction factor: 0.9 Flow rate: 135 m3/hr Operation hours: 20 hrs a) 0.5 m3 b) 1.5 m3 c) 0.6 m3 d) 2.5 m3 Answer: c Clarification: Cation load= Cation as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Cation load/ (Exchange capacity x Correction factor). Resin Volume =[(10 x 135 x 20)/1000]/(47 x 0.9)= 0.6 m3.
13. Calculate the amount of resin required for the following information. Cation Load: 30 ppm as CaCO3 Capacity: 47 Kg/m3 Correction factor: 0.9 Flow rate: 135 m3/hr Operation hours: 20 hrs a) 1.5 m3 b) 1.8 m3 c) 0.6 m3 d) 2.5 m3 Answer: b Clarification: Cation load= Cation as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Cation load/ (Exchange capacity x Correction factor). Resin Volume =[(30 x 135 x 20)/1000]/(47 x 0.9)= 1.8 m3.
14. Calculate the amount of resin required for the following information. Cation Load: 80 ppm as CaCO3 Capacity: 47 Kg/m3 Correction factor: 0.9 Flow rate: 135 m3/hr Operation hours: 20 hrs a) 4.5 m3 b) 4.8 m3 c) 0.6 m3 d) 2.5 m3 Answer: b Clarification: Cation load= Cation as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Cation load/ (Exchange capacity x Correction factor). Resin Volume =[(80 x 135 x 20)/1000]/(47 x 0.9)= 4.8 m3.
15. Calculate the amount of resin required for the following information. Cation Load: 100 ppm as CaCO3 Capacity: 57 Kg/m3 Correction factor: 0.9 Flow rate: 135 m3/hr Operation hours: 20 hrs a) 4.5 m3 b) 5.3 m3 c) 7.9 m3 d) 7.5 m3 Answer: b Clarification: Cation load= Cation as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Cation load/ (Exchange capacity x Correction factor). Resin Volume =[(100 x 135 x 20)/1000]/(57 x 0.9)= 5.3 m3.
16. Calculate the SAC resin required for the following data. It should be noted that prior to the SAC, a WAC system is present. M Alkalinity: 100 ppm as CaCO3 P Alkalinity: 100 ppm as CaCO3 EMA: 50 ppm as CaCO3 Capacity: 57 Kg/m3 Correction factor: 0.9 Flow rate: 135 m3/hr Operation hours: 20 hrs a) 4.5 m3 b) 6.9 m3 c) 5.7 m3 d) 7.5 m3 Answer: b Clarification: The WAC removes 60 % of the load of the Alkalinity. The load for SAC is calculated as 0.4 x (P Alkalinity + M Alkalinity). Ionic load= 0.4 x (P Alkalinity + M Alkalinity) +(EMA) as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Cation load/ (Exchange capacity x Correction factor). Resin Volume = [(130 x 135 x 20)/1000]/(57 x 0.9)= 0.6 m3.
17. The treatment system consists of a WAC, SAC which is followed by a WBA and SBA. Calculate the amount of WBA resin required for the following data. M Alkalinity: 100 ppm as CaCO3 P Alkalinity: 100 ppm as CaCO3 EMA: 25 ppm as CaCO3 Capacity: 37 Kg/m3 Correction factor: 0.9 Flow rate: 135 m3/hr Operation hours: 20 hrs a) 2.5 m3 b) 2.8 m3 c) 1.2 m3 d) 7.5 m3 Answer: c Clarification: The SAC removes around 60% of the EMA. WBA removes only EMA. Ionic load= 0.4 x EMA as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Anion load/ (Exchange capacity x Correction factor). Resin Volume = [(15 x 135 x 20)/1000]/(37 x 0.9)= 1.2 m3.
18. The treatment system includes a WAC, SAC, followed by a WBA and SBA. There is no degasser in this system. Calculate the amount of resin required for the following information. M Alkalinity: 100 ppm as CaCO3 P Alkalinity: 100 ppm as CaCO3 Silica: 45 ppm as CaCO3 CO2: 45 ppm as CaCO3 Capacity: 37 Kg/m3 Correction factor: 0.9 Flow rate: 35 m3/hr Operation hours: 10 hrs a) 1.5 m3 b) 1.1 m3 c) 7.9 m3 d) 7.5 m3 Answer: b Clarification: SBA removes Silica, carbon dioxide and Alkalinity. The load for SBA is considered as CO2 as CaCO3 + Silica as CaCO3 + 5% of (M Alkalinity +P Alkalinity) + 5% EMA. Ionic load= Anion as CaCO3 x Flow rate x Operating hours/1000. Resin Volume= Anion load/ (Exchange capacity x Correction factor). Resin Volume = [(100 x 35 x 10)/1000]/(37 x 0.9)= 1.1 m3.
19. The treatment system includes a WAC, SAC, followed by a WBA and SBA. There is a degasser in this system. Calculate the amount of SBA resin required for the following data. M Alkalinity: 100 ppm as CaCO3 P Alkalinity: 100 ppm as CaCO3 Silica: 30 ppm as CaCO3 CO2: 45 ppm as CaCO3 EMA: 100 ppm as CaCO3 Capacity: 37 Kg/m3 Correction factor: 0.9 Flow rate: 35 m3/hr Operation hours: 10 hrs a) 0.5 m3 b) 0.9 m3 c) 1.9 m3 d) 1.5 m3 Answer: a Clarification: SBA removes Silica, carbon dioxide and Alkalinity. The load for SBA which have adegasser prior to it, is considered as CO2 (5 ppm –residual Carbon dioxide) as CaCO3 + Silica as CaCO3 + 5% EMA. Ionic load= Anion as CaCO3 x Flow rate x Operating hours/1000. Resin Volume = Anion load / (Exchange capacity x Correction factor). Resin Volume = [(40 x 35 x 10)/1000]/(37 x 0.9)= 0.5 m3.
Waste Water Engineering Multiple Choice Questions on “Rural Sanitation”.
1. Which year was the Central Rural Sanitation program started? a) 1986 b) 1996 c) 2006 d) 2016 Answer: a Clarification: The Central Rural Sanitation Programme, which was started in 1986, was one of India’s first efforts to provide safe sanitation in rural areas. This programme focussed mainly on providing subsidies to people to construct sanitation facilities.
2. Which year was the Total Sanitation Campaign started? a) 1989 b) 1995 c) 1999 d) 2004 Answer: c Clarification: In 1999, a restructured Total Sanitation Campaign (TSC) was initiated to create supply-led sanitation by promoting local sanitary marts and a range of technological options.
3. What was the percentage of rural households having access to toilets in 2011? a) 20.7% b) 30.7% c) 40.7% d) 50.7% Answer: b Clarification: A huge difference in the number of rural households with toilets. According to census 2011 data, only 30.7% of rural households had access to toilets in 2011. According to rural sanitation scheme data, the number was considerably larger at 79.9%.
4. How much is the population in India practising open defecation? a) 600 million b) 620 million c) 626 million d) 636 million Answer: c Clarification: India has the largest number of people who practice open defecation (626 million) and the most number of child deaths due to poor water, sanitation and hygiene conditions compared to the rest of the world.
5. When was India’s rural sanitation restructured? a) 2011 b) 2012 c) 2013 d) 2014 Answer: b Clarification: In 2012, India’s rural sanitation scheme was restructured as the Nirmal Bharat Abhiyan (NBA) acknowledges this. Its main goal is universal toilet coverage by 2022.
6. The Nirmal Bharat Abhiyan (NBA) goals universal toilet coverage by the year _____ a) 2020 b) 2022 c) 2024 d) 2026 Answer: b Clarification: The Nirmal Bharat Abhiyan (NBA) goals not only universal toilet coverage by 2022, but also improving health and providing privacy and dignity to women, with the overall goal of improving the quality of life of people living in rural areas.
7. What is the average population in developing countries who do not have access to basic sanitation? a) 1 billion b) 1.5 billion c) 2 billion d) 2.5 billion Answer: d Clarification: Today 2.5 billion people in developing countries do not have access to basic sanitation services. This has a profound effect on their health, economic and social well-being.
8. What is the thickness of the compacted earth required for a top cover? a) 20 cm b) 50 cm c) 75 cm d) 100 cm Answer: d Clarification: A section of the trench has to be compacted with the bulldozer after its filled. The top, side and end of the section are covered with earth and the top is covered with 100 cm of compacted earth.
9. What is the maximum height of compacted waste? a) 0.5-1 m b) 1-1.5 m c) 1.5-2 m d) 2-3 m Answer: d Clarification: Each layer is compacted as the filling progresses during the course of the day until the thickness of the compacted wastes reaches a height varying from 2–3 m.
WASTE WATER Engineering Multiple Choice Questions :-
1. For a continuous flow type of sedimentation tanks
A. Width of the tank is normally kept about 6 m
B. Length of the tank is normally kept 4 to 5 times the width
C. Maximum horizontal flow velocity is limited to 0.3 m/minute
D. All the above
ANS: D
2. The asbestos cement sewers are
A. Light in weight
B. Not structurally strong to bear large compressive stress
C. Susceptible to corrosion by sulphuric acid
D. All the above
ANS: D
3. For efficient working of a sewer, it must be ensured that
A. Minimum velocity of 0.45 m/sec, is maintained at its minimum flow
B. A maximum velocity of 0.90 m/sec, is maintained at its maximum flow
C. Both A. and B.
D. Neither A. nor B.
ANS: C
4. Pick up the correct statement from the following:
A. The sewer pipes of sizes less than 0.4 m diameter are designed as running full at maximum discharge
B. The sewer pipes of sizes greater than 0.4 m diameter are designed as running 2/3rd or 3/4th full at maximum discharge
C. The minimum design velocity of sewer pipes is taken as 0.8 m/sec
D. All the above
ANS: D
5. Pick up the correct statement from the following:
A. Maximum daily flow = 2 times the average daily flow
B. Maximum daily flow = average daily flow
C. Sewers are designed for minimum permissible velocity at minimum flow
D. All the above
ANS: D
6. Bottom openings 15 cm × 15 cm in the standing baffle wall are provided
A. 15 cm c/c
B. 22.5 cm c/c
C. 30 cm c/c
D. 50 cm c/c
ANS: B
7. The pressure exerted by
A. The sewage when running full from inside, is called internal pressure
B. The internal pressure if any, causes tensile stress in the pipe material
C. Pressure sewers are designed to be safe in tension
D. All the above
ANS: D
8. For drainage pipes in buildings the test applied before putting them to use, is
A. Water test
B. Smoke test
C. Straightness test
D. All the above
ANS: B
9. No treatment of the sewage is given if dilution factor is
A. Less than 150
B. Between 150 to 200
C. Between 200 to 300
D. More than 500
ANS: D
10. Which of the following pumps in used to pump sewage solids with liquid sewage without clogging the pump is?
A. Centrifugal pump
B. Pneumatic ejector
C. Reciprocating pump
D. None of these
ANS: A
WASTE WATER Engineering MCQs
11. Acid regression stage of sludge digestion at a temperature 21°C extends over a period of
A. 15 days
B. 30 days
C. 60 days
D. 90 days
ANS: D
12. Pick up the correct statement from the following:
A. Small sewers are cleaned by flushing
B. Medium sewers are cleaned by cane rodding
C. Medium sewers may be cleaned by pills
D. All the above
ANS: D
13. The coagulant which is generally not used for treating the sewage, is
A. Alum
B. Ferric chloride
C. Ferric sulphate
D. Chlorinated copperas
ANS: A
14. The layers of vegetable wastes and night soil alternatively piled above the ground to form a mound, is called
A. A heap
B. Plateau
C. Windrow
D. None of these
ANS: D
15. If the flame of a miner’s safety lamp in the upper layers of the sewer forms an explosive, the sewer certainly contains
A. Hydrogen sulphide
B. Carbon dioxide
C. Methane
D. Oxygen
ANS: C
16. The gas which may cause explosion in sewers, is
A. Carbondioxide
B. Methane
C. Ammonia
D. Carbon monoxide
ANS: B
17. Pick up the correct statement from the following:
A. The water supply pipes carry pure water free from solid particles
B. The water supply pipes get clogged if flow velocity is less than self cleansing velocity
C. The sewers may be carried up and down the hills and valleys
D. The sewer pipes are generally laid along level hills
ANS: A
18. Pick up the incorrect statement from the following:
A. The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion
B. Sludge digestion is carried out in sludge tank
C. The gases produced in sludge digestion process, contain 75% carbon dioxide
D. The gases produced in sludge digestion process, contain 75% methane
ANS: C
19. The sewer pipes
A. Carry sewage as gravity conduits
B. Are designed for generating self-cleansing velocities at different discharge
C. Should resist the wear and tear caused due to abrasion
D. All the above
ANS: D
20. The settling velocity of the particles larger than 0.06 mm in a settling tank of depth 2.4 is 0.33 m per sec. The detention period recommended for the tank, is
A. 30 minutes
B. 1 hour
C. 1 hour and 30 minutes
D. 2 hours
ANS: D
21. depends upon The Chezy’s constant C in the formula V = C
A. Size of the sewer
B. Shape of the sewer
C. Roughness of sewer surface
D. All the above
ANS: D
22. The discharge per unit plan area of a sedimentation tank, is generally called
A. Over flow rate
B. Surface loading
C. Over flow velocity
D. All the above
ANS: D
23. Pick up the incorrect statement from the following for allowing workers to enter sewers
A. The particular manhole and one manhole on upstream and one manhole on downstream should remain open for 30 minutes
B. Proper tests for the presence of poisonous gases must be carried out
C. The men entering the manhole should be advised to smoke in the sewer
D. Warning signals should be erected
ANS: C
24. For the open drain (N = 0.025) shown in the below figure, the discharge is
A. 26.88 cumecs
B. 27.88 cumecs
C. 28.88 cumecs
D. 29.88 cumecs
ANS: C
25. To prevent settling down of sewage both at the bottom and on the sides of a large sewer, self-cleaning velocity recommended for Indian conditions, is
A. 0.50 m/sec
B. 0.60 m/sec
C. 0.70 m/sec
D. 0.75 m/sec
ANS: D
26. Assertion A.: The determination of pH value of sewerage is important.
Reason (R): The efficiency of certain treatment methods depends upon the availability of pH value.
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 a correct explanation of A
C. A is true but R is false
D. A is false but R is true
ANS: A
27. The normal values of over flow rates for sedimentation tanks using coagulant, ranges between
A. 25,000 to 35,000 litres/sqm/day
B. 40,000 to 50,000 litres/sqm/day
C. 50,000 to 60,000 litres/sqm/day
D. 80,000 to 100,000 litres/sqm/day
ANS: C
28. The drainage area of a town is 12 hectares. Its 40% area is hard pavement ( K = 0.85), the 40% area is unpaved streets (K = 0.20) and the remaining is wooded areas (K = 0.15). Assuming the time of concentration for the areas as 30 minutes and using the formula Ps = 900/(t + 60) the maximum run off is
A. 0.10 cumec
B. 0.12 cumec
C. 0.15 cumec
D. 0.20 cumec
ANS: C
29. Sewer pipes are designed for maximum discharge with 25% to 33% vacant cross-sectional area for
A. Unexpected large scale infiltration of stream water
B. Unexpected increase in the population
C. Under estimates of maximum and average flows
D. All of the above
ANS: D
30. The rational formula for peak drainage discharge, was evolved by
A. Fruhling
B. Lloyd David
C. Kuichling
D. All of these
ANS: D
Q No: 31
The sewer that unloads the sewage at the point of treatment is called
A. Main sewer
B. Outfall sewer
C. Branch sewer
D. House sewer
ANS: B
Q No: 32
During preliminary treatment of a sewage
A. Oil and grease are removed from skimming tanks
B. Floating materials are removed by screening
C. Girt and sand are removed by girt chambers
D. All the above
ANS: D
Q No: 33
For a grit chamber, if the recommended velocity of flow is 0.2 m/sec and detention period is 2 minutes, the length of the tank, is
A. 16 m
B. 20 m
C. 24 m
D. 30 m
ANS: C
Q No: 34
Dry weather flow is:
A. Average daily rate of flow
B. Average monthly rate of flow
C. Average annual rate of flow
D. Water supply allowance per capita
ANS: D
Q No: 35
Pick up the incorrect statement from the following:
A. The mixture of water and waste products, is called sewage
B. The treated sewage effluents, are generally used for irrigating the crops
C. The process of collecting, treating and disposing off the sewage, is called sewerage
D. The old convergence system was definitely better than water carried sewerage system ANS: D
Q No: 36
Pick up the correct statement from the following:
A. The maximum rate of storm runoff is called peak drainage discharge
B. Rational method of estimating peak run off, may be used precisely for areas less than 50 hectares
C. The period after which the entire area starts contributing to the runoff, is called the time of concentration
D. All the above
ANS: D
Q No: 37
If q is the average sewage flow from a city of population P, the maximum sewage flow
A. Q = [(4 + )/(18 + )] q
B. Q = [(18 + P)/(4 + )] q
C. Q = [(18 + )/(4 + )] q
D. Q = [(5 + )/((15 + )] q
ANS: C
Q No: 38
¾th or ¼th extra space is left in sewer pipes at maximum discharge for
A. Low estimates of the average and maximum flows
B. Large scale infiltration of storm water
C. Unexpected increase in population
D. All the above
ANS: D
Q No: 39
If the flame of a miner’s safety lamp in a manhole extinguishes within 5 minutes, the sewer certainly contains
A. Hydrogen sulphide
B. Carbon dioxide
C. Methane
D. Oxygen
ANS: B
Q No: 40
Hydraulic mean radius is
A. Mean radius of sewer
B. Difference in heads between two points in circular pipes
C. Mean of radii in a pipe line of varying cross -sections
D. Cross-sectional area/wetted perimeter
ANS: D
Q No: 41
If the depth of flow in a circular sewer is 1/4th of its diameter D, the wetted perimeter is
A. /2
B. /4
C. /3
D. D
ANS: C
Q No: 42
Pick up the correct statement from the following:
A. Anaerobic bacteria flourish in the absence of oxygen B. Aerobic bacteria flourish in the presence of oxygen C. Facultative bacteria flourish with or without oxygen D. All the above
ANS: D
The Brake Horse power of the motor (efficiency 60%) required for a pump of capacity 0.075 cumec
for a total lift of 12 m, is
A. 10
B. 15
C. 20
D. 25
Q No: 44
Aerobic bacterias
A. Flourish in the presence of free oxygen
B. Consume organic matter as their food
C. Oxidise organic matter in sewage
D. All the above
ANS: D
Q No: 45
At the junction of sewers
A. Top of smaller sewer is kept lower
B. Top of larger sewer is kept lower
C. Tops of both the sewers are at the same level
D. None of these
ANS: D
Q No: 46
Traps
A. Are water seals which prevent the entry of foul gases
B. Are used to trap the rats entering sewers
C. Dissolve the foul gases
D. Create symphonic action to increase the quick disposal of sewerage ANS: A
Q No: 47
The sewage treatment units in which anaerobic decomposition of organic matter is used, are called
A. Imhoff tanks
B. Trickling filters
C. Sludge sedimentation tanks
D. None of these
ANS: B
Q No: 48
Pick up the correct statement from the following:
A. In treated sewage, 4 ppm of D.O. is essential
B. Only very fresh sewage contains some dissolved oxygen
C. The solubility of oxygen in sewage is 95% that is in distilled water
D. All the above
ANS: D
Q No: 49
If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. None of these ANS: B
Q No: 50
The sewer which received discharge from two or more main sewers, is known as
A. A trunk sewer
B. An outfall sewer
C. A main sewer
D. An intercepting sewer
ANS: A
Q No: 51
The grit and silt of the grit chambers, may not be used for
A. Raising low lying areas by dumping
B. Concreting
C. Both A. and B.
D. Neither A. nor B.
ANS: B
Q No: 52
For treating the sewage of a large city, you will recommend
A. A sedimentation tank and an activated sludge treatment plant
B. A plant consisting of Imhoff tanks with low rate trickling filters
C. Sedimentation tanks with high rate trickling filters
D. None of these
ANS: A
Q No: 53
Imhoff cone is used to measure
A. Total organic solids
B. Total solids
C. Total in organic solids
D. Settleable solids ANS: D
Q No: 54
Pick up the correct statement from the following:
A. The ratio of the quantity of the diluting water to that of the sewage, is known as dilution factor
B. The automatic purification of polluted water, is known self purification phenomenon C. The photosynthesis is carried out in the presence of sun light
D. All the above
ANS: D
Q No: 55
1000 kg of sewage contains
A. 0.112 kg in suspension
B. 0.112 kg in solution
C. 0.225 kg in solution
D. Both A. and C. of above
ANS: D
Q No: 56
Dilution method of disposing of sewage, is not preferred to
A. When sewage is fresh
B. When diluting water has high dissolved oxygen content
C. When diluting water is used for water supply near the point of sewage disposed
D. When the diluting water is having flow currents ANS: C
Q No: 57
If the peak discharge of a storm water drain (S.W. Drain) is expected to exceed 150 cumecs, the free board to be provided, is
A. 100 cm
B. 90 cm
C. 80 cm
D. 50 cm
ANS: A
Q No: 58
The reduced levels of the string at the consecutive sight rails A and B are 203.575 m, 203.475 m respectively. If the difference of their R.D.s is 10 m, the gradient of the sewer line is
A. 1 in 100 upward
B. 1 in 500 upward
C. 1 in 100 downward
D. 1 in 503 upward
ANS: C
Q No: 59
R.M.O. expenses include
A. Running expenses
B. Maintenance expenses
C. Operation expenses
D. All the above
ANS: D
Q No: 60
For the COD test of sewage, organic matter is oxidised by K2Cr2O7 in the presence of
A. H2SO4
B. HNO3
C. HCl
D. None of these
ANS: A
Q No: 61
The sludge does not contain waste water from
A. Bath rooms
B. Wash basins
C. Kitchen sinks
D. Toilets
ANS: D
Q No: 62
In sewers the velocity of flow should not be
A. More than the self-cleansing velocity
B. Less than the self-cleansing velocity
C. Less than 10 m/sec
D. More than 20 m/sec
ANS: B
Q No: 63
Pick up the correct statement from the following:
A. Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers
B. 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river
C. Solubility of oxygen in sewage is 95% of that of distilled water
D. All the above
ANS: D
Q No: 64
In sewers the effect of scouring is more on
A. Top side
B. Bottom side
C. Horizontal side
D. All sides ANS: B
Q No: 65
The rainfall at any place may be determined by
A. Its intensity
B. Its direction
C. Its frequency
D. All the above
ANS: D
Q No: 66
Pick up the correct statement from the following:
A. The circular section of sewers provides maximum hydraulic mean depth
B. The circular sewers are provided for separate sewerage system
C. The circular sewers work efficiently if the sections run at least half full
D. All the above
ANS: D
Q No: 67
Pick up the correct statement from the following:
A. Rate of digestion of sludge is more at higher temperature
B. Thermophilic organisms digest the sludge if the temperature ranges from 40° to 60°C
C. Mesophilic organisms digest the sludge if the temperature is between 25° and 40°C
D. All the above
ANS: D
Q No: 68
Sewer ventilating columns are generally placed at
A. Distances 150 m to 300 m
B. Upper ends of branch sewers
C. Every change in the size of sewers
D. All the above
ANS: D
Q No: 69
The sewer which resists sulphide corrosion, is
A. Brick sewer
B. Cast iron sewer
C. R.C.C. sewer
D. Lead sewer
ANS: D
Q No: 70
In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a discharge Q, is
A. Q/(B × D)
B. Q/(L × D)
C. Q/L
D. Q/(B × L)
ANS: D
Q No: 71
The formula which accepts the value of rugosity coefficient n = 0.012 to be used in Manning’s formula, is given by
A. Bazin
B. Crimp and Bruges
C. William-Hazen
D. Kutter
ANS: B
Q No: 72
The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known
A. Bio-Chemical Oxygen Demand (B.O.D.)
B. Dissolved Oxygen (D.O.)
C. Chemical Oxygen Demand (C.O.D.)
D. None of these
ANS: B
Q No: 73
Water content of sewage is about
A. 90 %
B. 95 %
C. 99 %
D. 9.9 %
ANS: D
Q No: 74
Skimming tanks are
A. Used to remove the grease and oil
B. Those from which sludge is skimmed out
C. Tanks provided with self- cleansing screens
D. Improved version of grit chambers
ANS: A
Q No: 75
The most efficient cross-section of sewers in a combined sewerage system is
A. Parabolic
B. Circular
C. Rectangular
D. New egged ANS: B
Q No: 76
The detention period for plain sedimentation water tanks, is usually
A. 4 to 8 hours
B. 8 to 16 hours
C. 16 to 24 hours
D. 24 to 36 hours
ANS: A
Q No: 77
The factor responsible for purification of sewage in river is
A. Hydrology
B. Dissolved oxygen in water
C. Temperature
D. All the above
ANS: D
Q No: 78
Hume steel pipes are
A. Steel pipes
B. Steel shell coated from inside with cement mortar
C. Steel shell coated from outside with cement mortar
D. Both B. and C.
ANS: D
Q No: 79
To maintain aerobic biological activity, the moisture content of the compost mass should be about
A. 45 %
B. 50 %
C. 55 %
D. 60 %
ANS: C
Q No: 80
Pick up the correct statement from the following:
A. The larger the sewer in size, more will be velocity
B. The smaller the sewer in size, less will be velocity
C. The larger the sewer in size, no deposition will take place
D. The larger the sewer in size, deposition will take place ANS: D
Q No: 81
The pH value of sewage is determined with the help of
A. Imhoff Cone
B. Turbid meter
C. Potentiometer
D. None of these
ANS: C
Q No: 82
If the length of overland flow from the critical point to the mouth of drain is 13.58 km and difference in level between the critical point and drain mouth is 10 m, the inlet time is
A. 2 hours
B. 4 hours
C. 6 hours
D. 8 hours
ANS: D
Q No: 83
The normal value of over flow rates for plain primary sedimentation tanks, ranges between
A. 25,000 to 35,000 litres/sqm/day
B. 40,000 to 50,000 litres/sqm/day
C. 50,000 to 60,000 litres/sqm/day
D. 80,000 to 100,000 litres/sqm/day
ANS: B
Q No: 84
Pick up the incorrect statement from the following:
A. Septic tanks are horizontal continuous flow type of sedimentation tanks
B. Septic tanks are generally provided a detention period of 12 to 36 hours
C. Septic tanks are completely covered and high vent shafts are provided for the escape of foul gases
D. None of these
ANS: D
Q No: 85
Which one of the following statements regarding septic tanks is wrong?
A. A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided
B. The outlet invert level is kept 5 to 7.5 cm below the inlet invert level C. The minimum width of septic level is 90 cm
D. The depth of tank is kept equal to its width
ANS: D
Q No: 86
In a trickling filter
A. Filtration process is used
B. Biological action is used
C. Neither A. nor B.
D. Both A. and B. ANS: B
Q No: 87
In areas where rainy season is limited to a few months, the type of sewerage system recommended is
A. Combined system
B. Partially separate system
C. Separate system
D. None of these
ANS: C
Q No: 88
The rate of accumulation of sludge in septic tanks is recommended as
A. 30 litres/person/year
B. 25 litres/person/year
C. 30 litres/person/month
D. 25 litres/person/month
ANS: A Q No: 89
Dried sewage after treatment is used as
A. Fertilizer
B. Building material
C. Chemical for lowering B.O.D.
D. Base material for paints
ANS: A Q No: 90
15 cumecs, the depth d and width are related by
For drains up to
A. d = 0.2 B
B. d = 0.5 B
C. B = 0.2 d
D. B = 0.5 d
ANS: B
Q No: 91
In areas where light rains are uniformly distributed throughout the year, the type of sewerage system to be adopted is
A. Separate system
B. Combined system
C. Partially combined system
D. None of these ANS: B
Q No: 92
Self-cleansing velocity is
A. Velocity at dry weather flow
B. Velocity of water at flushing
C. Velocity at which no accumulation remains in the drains
D. Velocity of water in a pressure filter
ANS: C
Q No: 93
5 days-biochemical oxygen demand (BOD5) is taken at a temperature of
A. 0°C
B. 15°C
C. 20°C
D. 25°C
ANS: C
Q No: 94
Pick up the correct statement from the following:
A. Inlets are provided on the road surface at the lowest point for draining rain water B. Inlets are generally provided at an interval of 30 m to 60 m along straight roads C. Inlets having horizontal openings, are called horizontal inlets
D. All the above
ANS: D
Q No: 95
If a 2% solution of sewage sample is incubated for 5 days at 20°C and the dissolved oxygen depletion was found to be 8 mg/l. The BOD of the sewage is
A. 100 mg/l
B. 200 mg/l
C. 300 mg/l
D. 400 mg/l
ANS: D
Q No: 96
Pick up the in-correct statement from the following:
A. Manholes are provided in sewer pipes at suitable intervals
B. Catch basins are generally provided in sewers for carrying drainage discharge
C. Inlets are generally provided in all sewers
D. None of these
ANS: C
Q No: 97
A well oxidized sewage contains nitrogen mainly as
A. Nitrates
B. Nitrites
C. Free ammonia
D. None of these
ANS: A
Q No: 98
The moisture content of sludge is reduced from 90% to 80% in a sludge digestion tank. The percentage decrease in the volume of sludge, is
A. 25 %
B. 50 %
C. 10 %
D. 5 %
ANS: B
Q No: 99
In a sludge tank, the gas mainly produced, is
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide
ANS: D
Q No: 100
Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to
A. Initial demand
B. First stage demand
C. Carbonaceous demand
D. All of these
ANS: D
Q No: 101
are available in size
Stoneware sewers
A. 10 cm
B. 15 cm
C. 20 cm
D. All the above
ANS: D Q No: 102
If is the diameter of upper circular portion, the overall depth of New Egg shaped sewer section,
is A. 1.250 D
B. 1.350 D
C. 1.425 D
D. 1.625 D ANS: D
Q No: 103
In normal conditions, the period for sludge digestion, is
A. 10 days
B. 20 days
C. 30 days
D. 60 days
ANS: C
Q No: 104
For evaporation and measurement of settable solids, the apparatus used, is
A. A jar
B. A breaker
C. A test tube
D. An Imhoff cone
ANS: D
Q No: 105
In trickling filter, B.O.D. is reduced to
A. 30 to 40%
B. 40 to 60%
C. 60 to 80%
D. 80 to 90%
ANS: C
Q No: 106
For design of sewers, percentage of sewage discharge is assumed
A. 65 to 70%
B. 70 to 75%
C. 75 to 80%
D. 85%
ANS: C
Q No: 107
The grit chambers of sewage treatment plants, are generally cleaned after
A. 2 days
B. 7 days
C. 12 days
D. 14 days
ANS: D
Q No: 108
Maximum permissible velocity 1.5 m/sec, is adopted in drains
A. With beds of rocks and gravels
B. Lined with stones
C. Both A. and B.
D. Neither A. nor B.
ANS: C
Q No: 109
The average temperature of sewage in India, is
A. 10°C
B. 15°C
C. 20°C
D. 25°C
ANS: C
Q No: 110
‘Cowl’ is provided at
A. Lower end of ventilating column
B. Upper end of ventilating column
C. Upper end of the manhole
D. First step in manhole
ANS: B
Q No: 111
If the discharge of a sewer running half is 628 1.p.s., i = 0.001, and n = 0.010, the diameter of the
sewer, is
A. 1.39 m
B. 1.49 m
C. 1.59 m
D. 1.69 m
ANS: D Q No: 112
A drop manhole is provided if
A. A sewer drops from a height
B. A branch sewer joins the main sewer at higher level
C. A lamp is inserted to check obstruction
D. None of these
ANS: B Q No: 113 running partially full with central angle ,
For a circular sewer of diameter
A. d/D = ½ (1 – –
B. a/A
C. r/R = [1 –
D. All the above ANS: D
Q No: 114
The use of coarse screens for the disposal of sewage, may be dispensed with by
A. Comminutor
B. Shredder
C. Both A. and B.
D. Neither A. nor B.
ANS: C
Q No: 115
In the activated sludge process
A. Aeration is continued till stability
B. Aeration is done with an admixture of previously aerated sludge
C. Sludge is activated by constant stirring
D. Water is removed by centrifugal action
ANS: B
Q No: 116
For detecting the nitrates in sewage, the colour may be developed by adding
A. Potassium permanganate
B. Sulphuric acid and napthamine
C. Phenol-di -sulphuric acid and potassium hydroxide
D. None of these
ANS: C
Q No: 117
The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is
A. Vs = 418 (Gs – Gw) d [(3T + 70)/100]
B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100]
C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100]
D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]
ANS: B
Q No: 118
In septic tanks,
A. Free board of 0.3 m may be provided
B. The baffles or tees are extended up to top level of scum
C. The clear space between the baffle top and covering slab is about 7.5 cm
D. All the above
ANS: D
Q No: 119
Inter-distance between ventilation columns in a sewer line is kept
A. 25 to 50 m
B. 50 m to 100 m
C. 100 m to 150 m
D. 150 m to 300 m
ANS: D
Q No: 120
Stone ware pipes are
A. Highly resistant to sulphide corrosion
B. Highly impervious
C. Hydraulically efficient because of their smooth interior surface
D. Especially suited to pressure pipes
ANS: D
Q No: 121
The intensity of rain is expressed in
A. cm/minute
B. cm/hour
C. cm/day
D. None of these
ANS: B
Q No: 122
The ratio of the diameter of a circular section and the side of a square section hydraulically equivalent, is
A. 1.095
B. 1.085
C. 1.075
D. 1.065
ANS: A
Q No: 123
Which one of the following part of human body withstands minimum radiation?
A. Thyroid
B. Kidneys
C. Eyes
D. Ovaries/testis
ANS: D
Q No: 124
Drop manholes are the manholes
A. Without entry ladders
B. Without manhole covers
C. With depths more than 3.5 m
D. Having drains at different levels ANS: D
Q No: 125
The bottom of the sewage inlet chamber of septic tanks, is provided an outward slope
A. 1 in 5
B. 1 in 10
C. 1 in 15
D. 1 in 20
ANS: B
Q No: 126
If 2% solution of a sewage sample is incubated for 5 days at 20°C and depletion of oxygen was found to be 5 ppm, B.O.D. of the sewage is
A. 200 ppm
B. 225 ppm
C. 250 ppm
D. None of these
ANS: C
Q No: 127
Primary treatment of sewage consists of removal of
A. Large suspended organic solids
B. Oil and grease
C. Sand and girt
D. Floating materials
ANS: A
Q No: 128
The sewers
A. Must be of adequate size to avoid over flow
B. Must flow under gravity ½ to ¾ full
C. Must be laid at least 2 to 3 m deep to collect /water from the basements
D. All the above
ANS: D
Q No: 129
Cement concrete sewers are only suitable if non-scouring velocity is between
A. 2.5 to 3.0 m/sec
B. 3.0 to 4.0 m/sec
C. 3.5 to 4.5 m/sec
D. 4.5 to 5.5 m/sec
ANS: A
Q No: 130
In a fully mechanised composting plant, involves
A. Mechanized receipt
B. Mechanized segregation
C. Mechanized pulverising of refuse
D. All of these
ANS: D
Q No: 131
The most widely used pump for lifting sewage is
A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. Air pressure pump
ANS: A
Q No: 132
weight of water, the hydraulic mean depth of the sewer and the bed slope
w is the unit
of the sewer, then the tractive force exerted by flowing water, is
A. w r S S
B. w r1/2
C. w r S
D. w r2/3
ANS: A
Q No: 133
Setting out the alignments of sewers may start from
A. City
B. Out-fall
C. Tail end
D. Any point
ANS: C
Q No: 134
The detention time of a circular tank of diameter d and water depth H, for receiving the sewage Q per hour, is
A. d² (0.011d + 0.785H)/Q
B. d (0.022d + 0.085H)/Q
C. d (0.785d + 0.011H)/Q
D. d (0.285d + 0.011H)/Q
ANS: A
Q No: 135
Lead acetate test in sewer manhole is done to test the presence of
A. Methane gas
B. Hydrogen sulphide
C. Carbondioxide gas
D. Diesel vapours ANS: B
Q No: 136
Antisyphonage pipe is fitted
A. At the end of septic tanks
B. On manholes
C. With a W.C. trap
D. At the beginning of sewer line
ANS: C
Q No: 137
In a grit chamber of a sewage treatment plant,
A. Flow velocity 0.15 m to 0.3 m/sec is kept
B. Depth of 0.9 m to 1.20 m is kept
C. One minute of detention period is kept
D. All the above
ANS: D
Q No: 138
The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is
A. 1.5
B. 2.0
C. 3.0
D. 4.0
ANS: B
Q No: 139
pH value of sludge during alkaline regression stage, is
A. More than 7
B. Less than 7
C. Less than 6
D. More than 6
ANS: A
Q No: 140
The arrangement made for passing the sewer line below an obstruction below the hydraulic gradient lines called
A. Inverted syphon
B. Depressed sewer
C. Sag pipe
D. all of these
ANS: D
Q No: 141
Pick up the incorrect size of stone ware sewers
A. 52.5 cm
B. 67.5 cm
C. 82.5 cm
D. None of these
ANS: D
Q No: 142
Chlorination of water is done for the removal of
A. Bacterias
B. Suspended solids
C. Sediments
D. Hardness
ANS: A
Q No: 143
Sludge banks are formed if sewage is disposed of in
A. Rivers
B. Seas
C. Lakes
D. None of these
ANS: B
Q No: 144
Assertion A.: A free board of 0.3 m is provided above the top sewage line in septic tanks.
Reason (R): It helps to accommodate the scum in the septic tank.
A. Both A and R is true and R is the correct explanation of A
B. Both A and R is true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true
ANS: A
Q No: 145
The temperature affects the
A. Biological activity of bacteria in sewage
B. Solubility of gases in sewage
C. Viscosity of sewage
D. All the above
ANS: D
Q No: 146
The clarigesters are
A. Circular septic tanks
B. Rectangular septic tanks
C. Circular Imhoff double tanks with bottom hoppers
D. Circular Imhoff double storey tanks without bottom hoppers ANS: D
Q No: 147
The density of population over 40 hectares is 250/hectare. If water supply demand per day is 200 litres and sewage discharge is 80% of water supply, the sewage flow in sewers of separate system, is
A. 0.05552 cumec
B. 0.05554 cumec
C. 0.05556 cumec
D. 0.0556 cumec ANS: C
Q No: 148
In a residential colony, sewers of diameters 100 mm, 150 mm and 225 mm were laid with a gradient 1 in 120. Which portion of the sewage system does not choke in due course of time?
A. 100 mm dia.
B. 150 mm dia.
C. 225 mm dia.
D. All of these
ANS: C
Q No: 149
The spacing of bars for perforations in coarse screens used for the treatment of sewage, is
A. 20 mm
B. 30 mm
C. 40 mm
D. 50 mm
ANS: D
Q No: 150
In case of Imhoff tanks,
A. The shape is rectangular
B. Detention period is 2 hours
C. The velocity of flow is restricted to 0.30 m/minute
D. All the above
ANS: D
WASTE WATER Engineering Objective Questions Pdf ::
Q No: 151
The pH value of fresh sewage is usually
A. Equal to 7
B. More than 7
C. Less than 7
D. Equal to zero
ANS: B
Q No: 152
The maximum depth of sedimentation tanks, is kept
A. 3 m
B. 3.5 m
C. 4 m
D. 4.5 m
ANS: A
Q No: 153
If the depletion of oxygen is found to be 5 ppm after incubating a 2.5% solution of sewage sample for 5 days at 21°C, B.O.D. of the sewage is
A. 50 ppm
B. 100 ppm
C. 150 ppm
D. 200 ppm
ANS: D
Q No: 154
Pick up the correct statement from the following:
A. Indore method of composting involves decomposition under aerobic conditions
B. Bangalore method of composting involves decomposing under anaerobic conditions
C. Fully stabilised refuse by the Bangalore method of compositing is a powdery mass called humus
D. all of these
ANS: D
Q No: 155
Lead caulked joints are used for laying
A. Stone ware pipes
B. Earthenware pipes
C. C.I. pipes
D. G.I. pipes
ANS: B
Q No: 156
If D is the diameter of a circular sewer and D’ is the top horizontal diameter of an equivalent egg shaped section, the relationship which holds good, is
A. D’ = 0.64 D
B. D’ = 0.74 D
C. D’ = 0.84 D
D. D’ = 0.94 D
ANS: C
Q No: 157
The spacing of man holes along a straight portion of a sewer is 300 m, the diameter of the sewer may be
A. 0.9 cm
B. 1.2 m
C. 1.5 m
D. > 1.5 m
ANS: D
Q No: 158
A sewer running partially full and hurried with back filled, fails in compression due to
A. Weight of the pipe
B. Weight of the back fill
C. Superimposed traffic loads
D. All the above
ANS: D
Q No: 159
A five day B.O.D. at 15°C of the sewage of a town is 100 kg/day. If the 5 day B.O.D. per head at 15°C for standard sewage is 0.1 kg/day, the population equivalent is
A. 100
B. 1000
C. 5000
D. 10000
ANS: D
Q No: 160
Kjeldahl nitrogen is a mixture of
A. Ammonia and nitrogen
B. Nitrogen and organic nitrogen
C. Organic nitrogen and ammonia
D. All the above
ANS: D
WASTE WATER ENGINEERING Objective Questions with Answers
Q No: 161
The quantity of liquid waste which flows in sewers during the period of rainfall, is known
A. Sanitary sewage
B. Industrial waste
C. Storm sewage
D. None of these
ANS: C
Q No: 162
Nitrogen cycle of sewage, is
A. Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
B. Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates
C. Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia
D. Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates ANS: A
Q No: 163
Depletion of ozone layer in the outer atmosphere may cause
A. Lung cancer
B. Skin cancer
C. Bronchitis
D. Heart disorder
ANS: B
Q No: 164
The minimum diameter of a sewer is kept
A. 10 cm
B. 15 cm
C. 20 cm
D. 25 cm
ANS: B
Q No: 165
A cylindrical ejector having its height 2 m fills after every 10 minutes with a peak sewage discharge of 0.0157 cumec. The diameter of the ejector chamber, is
A. 2.30 m
B. 2.40 m
C. 2.45 m
D. 2.50 m
ANS: C
Q No: 166
Pick up the correct statement from the following:
A. The materials separated by screens, is called screenings
B. The screenings are disposed off either by burning or by burial or by dumping
C. The process of burning the screenings, is known as compositing
D. All the above
ANS: D
Q No: 167
Which one of the following gases is most significant as air pollutant?
A. Carbondioxide
B. Oxygen
C. Nitrogen
D. Sulphur-dioxide
ANS: D
Q No: 168
Hazen’s formula VS = 418 (GS – Gw)d [(3T + 70)/100] is used for the settlement velocity of the particles of diameter
A. Less than 0.01 mm
B. Less than 0.05 mm
C. Less than 0.1 mm
D. Greater than 0.1 mm
ANS: D
Q No: 169
For sewers, inverted siphon is provided for
A. One pipe
B. Two pipes
C. Three pipes
D. Four pipes
ANS: C
Q No: 170
Pick up the correct statement from the following:
A. pH value indicates acidity and alkalinity of sewage B. In acidic sewage, the pH value is less than 7 C. In alkaline sewage, the pH value is more than 7
D. All the above
ANS: D
Q No: 171
For large sewers, maximum distance between manholes may be
A. 50 m
B. 100 m
C. 200 m
D. 300 m
ANS: D
Q No: 172
In sewers designed with self cleansing velocity,
A. The bottom is silted
B. The bottom is scoured
C. Both silting and scouring occur at the bottom
D. Neither silting nor scouring occurs at the bottom ANS: D
Q No: 173
The value of Chezy’s constant C = 157.6/(1.81 + K/ ) is used in
A. Chezy’s formula
B. Bazin’s formula
C. Kutter’s formula
D. Manning’s formula ANS: B
Q No: 174
An inverted siphon is designed generally for
A. One pipe
B. Two pipes
C. Three pipes
D. Four pipes
ANS: C
Q No: 175
The spacing of bars of perforations of fine screens used for the treatment of sewage, is
A. 2 to 3 mm
B. 3 to 5 mm
C. 5 to 8 mm
D. 8 to 10 mm
ANS: A
Q No: 176
Pathogens (or pathogenic bacterias) in water may cause
A. Typhoid
B. Cholera
C. Dysentery
D. All the above
ANS: D
Q No: 177
The rate of accumulation of sludge per person per year, is
A. 10 litres
B. 15 litres
C. 20 litres
D. 25 litres
ANS: C
Q No: 178
The screens are fixed
A. Perpendicular to the direction of flow
B. Parallel to the direction of flow
C. At an angle 30° to 60° to the direction of flow
D. None of these
ANS: C
Q No: 179
In circular sewers if depth of flow is 0.2 times the full depth, the nominal gradient,
A. Is only provided
B. Is doubled
C. Is trebled
D. Is not enough
ANS: B
Q No: 180
In detritus tanks,
A. Flow velocity is kept 0.09 m/sec
B. Detention period is kept 3 to 4 minutes
C. Organic and inorganic materials are separated
D. All the above
ANS: D
Q No: 181
The flow velocity in detritus tanks is
A. 0.05 m/sec
B. 0.09 m/sec
C. 1.25 m/sec
D. None of these
ANS: B
Q No: 182
If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is
A. 1045 mm
B. 1065 mm
C. 1075 mm
D. 1095 mm
ANS: D
Q No: 183
The water carried sewerage system removes
A. Domestic sewage
B. Industrial sewage
C. Storm sewage
D. All the above
ANS: D
Q No: 184
A nuisance is experienced in diluting water if dilution factor is less than
A. 100
B. 60
C. 40
D. 20
ANS: D
Q No: 185
A manhole is generally provided at each
A. Bend
B. Junction
C. Change of gradient
D. All the above
ANS: D
Q No: 186
The asbestos cement pipes are generally laid
A. Horizontally
B. Vertically
C. At an angle of 30°
D. At an angle of 60°
ANS: B
Q No: 187
The design period in years for pumping plants, is
A. 1
B. 2 to 3
C. 3 to 5
D. 5 to 10
ANS: D
Q No: 188
A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of
A. Carbondioxide gas
B. Hydrogen sulphide gas
C. Methane gas
D. Petrol vapours
ANS: C
Q No: 189
The disintegrating pump in which solid matter is broken up before passing out, is
A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. None of these
ANS: A
Q No: 190
If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is
A. 50 mg/l
B. 100 mg/l
C. 150 mg/l
D. 250 mg/l
ANS: D
Q No: 191
Design period of 40 to 50 years is adopted for
A. Branch sewers
B. Main sewers
C. Trunk sewers
D. All the above
ANS: D
Q No: 192
A circular sewer section is preferred to because
A. It is cheaper in construction
B. It provides maximum area for a given perimeter
C. It provides maximum hydraulic mean depth
D. All the above
ANS: D
Q No: 193
In very first stage of decomposition of the organic matter in sewage
A. Nitrites are formed
B. Nitrates are formed
C. Carbondioxide is formed
D. Ammonia is formed
ANS: D
Q No: 194
In a city the ratio of the drainage to sewage is 20, the percentage discharge passing through non-monsoon periods, is
A. 5
B. 10
C. 15
D. 20
ANS: D
Q No: 195
The self-cleansing velocity of water flowing through pipe lines, is
A. 2 metres/sec
B. 1 metre/sec
C. 0.5 metre/sec
D. 0.25 metre/sec ANS: A Q No: 196
In case of sewer lines
A. Water test is carried out to check water tightness of the joints
B. Test for straightness is carried out with the help of a lamp and mirror
C. Obstruction test is carried out with the help of smooth ball of diameter 13 mm
D. All the above
ANS: D
Q No: 197
The normal values of over flow rates for secondary sedimentation tanks, ranges between
A. 25,000 to 35,000 litres/sqm/day
B. 40,000 to 50,000 litres/sqm/day
C. 50,000 to 60,000 litres/sqm/day
D. 80,000 to 10,000 litres/sqm/day
ANS: A
Q No: 198
A manhole is classified as shallow if its depth is between
A. 0.4 to 0.5 m
B. 0.5 to 0.7 m
C. 0.7 to 0.9 m
D. 0.9 to 1.20 m
ANS: C
Q No: 199
The first stage of neutral process of sludge digestion, is
A. Acid fermentation
B. Acid regression
C. Alkaline fermentation
D. None of these
ANS: A
Q No: 200
The stone ware sewers
A. Are used for carrying sewage and drainage from houses
B. Are manufactured from clays and shale
C. After casting are dried and burnt at temperature 150°C, 700°C and 1200°C
D. All the above
ANS: D
Q No: 201
The formula V = (1/n) r2/3
A. Chezy’s formula
B. Bazin’s formula
C. Kutter’s formula
D. Manning’s formula
ANS: D
Q No: 202
In sewers the highest non-scouring velocity is achieved in
A. Glazed bricks sewers
B. Cast iron sewers
C. Cement concrete sewers
D. Stone ware sewers
ANS: A
Q No: 203
The maximum diameter of sewers adopted in the designs is
A. 1.0 m
B. 2.0 m
C. 3.0 m
D. 4.0 m
ANS: C
Q No: 204
If D.O. concentration falls down to zero in any natural drainage, it indicates the zone of
A. Degradation
B. Active decomposition
C. Recovery
D. Cleaner water
ANS: B
Q No: 205
Facultative bacteria survive in
A. The presence of oxygen
B. The absence of oxygen
C. Both cases A. and B.
D. Neither A. nor B.
ANS: C
Q No: 206
For trunk and out-fall, the type of sewers generally used, is
A. Standard egg shaped
B. Circular shaped
C. Horse shoe shaped
D. Parabolic shaped ANS: C
Q No: 207
The maximum spacing of manholes specified by Indian standard in sewers upto 0.3 m diameter is
A. 20 m
B. 30 m
C. 45 m
D. 75 m
ANS: C
Q No: 208
The suitable cross-section of sewers to carry combined flow, is
A. Circular
B. Egg shaped
C. Rectangular
D. Horse shoe shaped
ANS: B
Q No: 209
The underground sewers are more subjected to
A. Tensile force
B. Compressive force
C. Bending force
D. Shearing force
ANS: B
Q No: 210
The minimum recommended diameter of sewers, is
A. 5 cm
B. 10 cm
C. 15 cm
D. 20 cm
ANS: C
Q No: 211
Ventilating shafts are provided to a sewer line at every
A. 100 m
B. 150 m
C. 200 m
D. 300 m
ANS: D
Q No: 212
The most efficient cross section of sewers in a separate sewerage system is
A. Parabolic
B. Circular
C. Rectangular
D. New egged ANS: B
Q No: 213
Boussinesq’s equation for ascertaining unit pressure at a depth on sewers due to traffic loads, is
A. pt = 3H3p/2 Z5
B. pt = 2H3p/3 Z5
C. pt = 3H3p/2Z5
D. pt = 2 3p/3Z5 ANS: A
Q No: 214
If the over land flow from the critical point to the drain is 8 km and the difference in level is 12.4 m, the inlet time is
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours
ANS: C
Q No: 215
For trunk sewers more than 1.25 m in diameter, the ratio of the maximum daily sewage flow to the average daily sewage flow is assumed
A. 1.5
B. 2.0
C. 2.5
D. 3.0
ANS: A
Q No: 216
The settlement of a particle in sedimentation tank, is affected by
A. Velocity of flow
B. Viscosity of water
C. Size and shape of solid
D. All the above
ANS: D
Q No: 217
If the pH value of sewage is 7
A. It is acidic
B. It is alkaline
C. It is neutral
D. None of these ANS: C
Q No: 218
A sewer pipe contains 1 mm sand particles of specific gravity 2.65 and 5 mm organic particles of specific gravity 1.2, the minimum velocity required for removing the sewerage, is
A. 0.30 m/sec
B. 0.35 m/sec
C. 0.40 m/sec
D. 0.45 m/sec
ANS: D
Q No: 219
The width of a settling tank with 2 hour detention period for treating sewage 378 cu m per hour, is
A. 5 m
B. 5.5 m
C. 6.5 m
D. 7 m
ANS: D
Q No: 220
The sewer which collects the discharge from a collecting system and delivers it to a treatment plant, is known
A. House sewer
B. Lateral sewer
C. Branch sewer
D. Sewer outfall
ANS: D
Q No: 221
For non-scouring velocity 5 m/sec, the type of sewers generally preferred to, is
A. Cast iron sewers
B. Cement concrete sewers
C. Glazed bricks sewers
D. Stone ware sewers
ANS: C
Q No: 222
Pick up the correct statement from the following:
A. The boning rod is used for checking the levels of the sewer inverts
B. Manhole covers are made circular for the convenience of the cleaning staff
C. A manhole is classified as shallow manhole if its depth is less than 0.9 m
D. All the above
ANS: D
Q No: 223
The ratio of maximum sewage flow to average sewage flow for trunk mains having diameters more than 1.25 m, is
A. 1.5
B. 2.0
C. 3.0
D. 4.0
ANS: A
Q No: 224
The most dangerous pollutant in vehicular emissions is
A. CO
B. SO2
C. CO2
D. O3
ANS: A
Q No: 225
Large diameter sewers subjected to external pressure alone, are reinforced
A. Near the inner surface of the pipe
B. Near the outer surface of the pipe
C. Both A. and B.
D. With elliptical cage
ANS: D
Q No: 226
For laying a sewer line in a trench of 2 m width, an offset line is marked on the ground parallel to the given centre line at a distance of
A. 100 cm
B. 120 cm
C. 140 cm
D. 160 cm
ANS: D
Q No: 227
The liquid wastes from kitchens, bath rooms and wash basins, is not called
A. Liquid waste
B. Sullage
C. Sewage
D. None of these
ANS: C
Q No: 228
The detention time (t) of a settling tank, may be defined as the time required for
A. A particle to travel along its length
B. A particle to travel from top surface to bottom sludge zone C. The flow of sewage to fill the tank
D. None of these
ANS: C
Q No: 229
The following is the physical characteristic of sewage
A. Turbidity
B. Colour
C. Odour
D. All the above
ANS: D
Q No: 230
The effluent of a septic tank is
A. Fit for discharge into any open drain
B. Foul and contains dissolved and suspended solids
C. As good as that from a complete treatment
D. None of these
ANS: A
Q No: 231
The design period of sewage treatment works in normally
A. 5 – 10 years
B. 15 – 20 years
C. 30 – 40 years
D. 40 – 50 years
ANS: B
Q No: 232
In Chezy’s formula V = C rs for calculating the velocity of flow in circular sewer of diameter running full, the value of hydraulic mean radius is
A. D
B. D /2
C. D/3
D. D/4
ANS: D
Q No: 233
It is customary to design a sewer for D.W.F. on the basis of
A. Average demand
B. Twice the average demand
C. Thrice the average demand
D. Four times the average demand
ANS: C
Q No: 234
For sewer mains of 0.5 to 1 m diameter, the ratio of maximum daily sewage flow to the average daily sewage flow is assumed
A. 1.5
B. 2.0
C. 2.5
D. 3.0
ANS: B
Q No: 235
Fresh sewage is generally
A. Alkaline
B. Acidic
C. Highly decomposed
D. A source of objectionable odour
ANS: A
Q No: 236
The recommended detention period for grit chambers is
A. 1 minute
B. 2 minutes
C. 3 minutes
D. 5 minutes
ANS: A
Q No: 237
For detecting the nitrites in the sewage, the matching colour may be developed by adding
A. Potassium permanganate
B. Sulphuric acid and napthamine
C. Phenol-di -sulphuric acid potassium hydroxide
D. None of these
ANS: B
Q No: 238
If is the diameter of upper circular portion, the overall depth of a standard egg shaped section,
is
A. D
B. 1.25 D
C. 1.5 D
D. 1.75 D ANS: C
Q No: 239
The laying of sewers is done with
A. Magnetic compass
B. Theodolite
C. Level
D. Clinometer ANS: C
Q No: 240
A rainfall may be classified as acidic if its pH value is less or equal to
A. 6
B. 7
C. 5
D. 6.5
ANS: C
Q No: 241
The settlement velocity of a solid (diameter 0.5 mm, specific gravity 1.75) in water having temperature 10°C, is
A. 213.5 cm/sec
B. 313.5 cm/sec
C. 413.5 cm/sec
D. 500 cm/sec
ANS: B
Q No: 242
For house drainage minimum gradient is
A. 1 in 60
B. 1 in 80
C. 1 in 10
D. 1 in 400
ANS: A
Q No: 243
For estimating the peak run off the rational formula Q = 0.0278 KpA was evolved by
A. Kinchling
B. Lloyd Davis
C. Frubling
D. All the above
ANS: D
Q No: 244
A rain sanitary sewer is constructed to carry
A. Sanitary sewage
B. Storm sewage
C. Surface water
D. Ground water
ANS: A
Q No: 245
The most effective arrangement for diverting excess storm water into a natural drainage, is
A. Leaping weir
B. Overflow weir
C. Siphon spill way
D. None of these
ANS: C
Q No: 246
The drop man holes are generally provided in sewers for
A. Industrial areas
B. Large town ships
C. Hilly town ships
D. Cities in plains
ANS: C
Q No: 247
For a peak discharge of 0.0157 cumec, with a velocity of 0.9 m/sec, the diameter of the sewer main, is
A. 10 cm
B. 12 cm
C. 15 cm
D. 18 cm
ANS: C
Q No: 248
For design purposes, the normal rate of infiltration of ground water into the sewer, is
A. 500 litres/km/cm
B. 1000 litres/km/cm
C. 1500 litres/km/cm
D. 2000 litres/km/cm
ANS: D
Q No: 249
You are asked to design sewer pipes of diameters 0.4 m to 0.9 m at maximum flow, you will assume the sewer flow running at
A. Full depth
B. Half full
C. Two third full
D. Three fourth full
ANS: B
Q No: 250
The algae dies out in the zone of
A. Degradation
B. Active decomposition
C. Recovery
D. Cleaner water ANS: A
Q No: 251
In a sludge digestion tank if the moisture content of sludge V1 litres is reduced from p1 % to p2 % the volume V2 is
A. [(100 + P1)/(100 – P2)] V1
B. [(100 – P1)/(100 + P2)] V1
C. [(100 – P1)/(100 – P2)] V1
D. [(100 + P2)/(100 – P1)] V1
ANS: C
Q No: 252
Assertion A. : Discharging the effluents from the oxidation ponds just up stream of lakes or reservoirs is undesirable.
Reason (R) : The discharged algae get settled in the reservoirs and cause anaerobic decomposition and other water qualities.
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 a correct explanation of A C. A is true but R is false
D. A is false but R is true
ANS: A
Q No: 253
The sewage treatment in septic tanks is due to
A. Anaerobic decomposition
B. Aerobic decomposition
C. Parasitic decomposition
D. None of these
ANS: A
Q No: 254
The dimensions of a rectangular settling tank are: length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is
A. 204 cu.m
B. 208 cu.m
C. 212 cu.m
D. 216 cu.m
ANS: D
Q No: 255
If is the rugosity coefficient, is the bed slope of sewer, the velocity of flow in m/sec may be obtained by the formula V = (1/n) r2/3 s1/2 evolved by
A. Chezy
B. Manning
C. Bazin
D. Kutter ANS: B
Q No: 256
Disposal to sewage in large cities, is done in
A. Irrigation
B. Dilution
C. Oxidation
D. Purification
ANS: B
Q No: 257
3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the D.O. concentration was 5 mg/l. The BOD of raw sewerage is
A. 100 mg/l
B. 200 mg/l
C. 300 mg/l
D. 400 mg/l
ANS: C
Q No: 258
The digested sludge from septic tanks, is removed after a maximum period of
A. 3 years
B. 3.5 years
C. 4 years
D. 5 years
ANS: A
Q No: 259
Assertion A.: The minimum self cleansing velocity in the sewer, at least once a day, must be generated.
Reason (R): If certain deposition takes place and is not removed, it obstructs free flow and causes further deposition leading to complete blocking of the sewer.
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 a correct explanation of A C. A is true but R is false
D. A is false but R is true
ANS: A
Q No: 260
The presence of free ammonia in sewage, is detected by
A. Boiling
B. Adding potassium permanganate
C. Adding sulphuric acid
D. Phenol-di-sulphuric acid ANS: A
Q No: 261
Dry water flow in a combined sewer, is
A. Industrial sewage
B. Domestic sewage
C. Storm water
D. Inclusive of domestic and industrial sewage but excludes storm water ANS: C
Q No: 262
The porosity of sediments in sewer pipes, is usually taken as
A. 0.010
B. 0.011
C. 0.012
D. 0.013
ANS: D
Q No: 263
In sewage having fully oxidised organic matter, the nitrogen exists in the form of
A. Nitrites
B. Nitrates
C. Free ammonia
D. Aluminoid nitrogen
ANS: B
Q No: 264
The minimum diameter of sewer to be adopted is
A. 10 cm
B. 12.5 cm
C. 15 cm
D. 25 cm
ANS: C
Q No: 265
If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. None of these
ANS: C
Q No: 266
The sewerage system consists of
A. House sewer
B. Lateral sewer
C. Branch sewer
D. All of these
ANS: D
Q No: 267
Clogging of sewers, is caused due to
A. Silting
B. Low discharge
C. Greasy and oily matters
D. All the above
ANS: D
Q No: 268
Oxidation process results in the formation of
A. Carbon dioxide
B. Nitrates
C. Sulphates
D. All the above
ANS: D
Q No: 269
The sewage is pumped up
A. From low lying areas
B. From flat areas
C. From basements
D. All the above
ANS: D
Q No: 270
The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120°, the depth of sewerage is
A. 20 cm
B. 25 cm
C. 40 cm
D. 50 cm
ANS: D
Q No: 271
Pick up the correct statement from the following:
A. Turbidity is more in strong sewage
B. The black colour indicates septic sewage
C. The sewage omits offensive odours after four hours
D. All the above
ANS: D
Q No: 272
If the grit in grit chambers is 4.5 million litres per day, its cleaning is done
A. Manually
B. Mechanically
C. Hydraulically
D. Electrically
ANS: A
Q No: 273
Which one of the following tests is used for testing sewer pipes?
A. Water test
B. Ball test
C. Mirror test
D. All of these
ANS: D
Q No: 274
The ratio of depths at partial flo
A. 1 –
B. 1 –
C. ½ (1 –
D. ½ (1 –
ANS: C
Q No: 275
The non-clog pump which permits solid matter to pass out with the liquid sewage, is
A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. None of these
ANS: A
Q No: 276
With self cleansing velocity in sewers
A. Silting occurs at bottom
B. Scouring occurs at bottom
C. Both silting and scouring occur at bottom
D. Neither silting nor scouring occurs at bottom
ANS: D
Q No: 277
When drainage to sewage ratio is 20, the peak dry weather flow is
A. 20% of the design discharge
B. Slightly less than 5% of the design discharge
C. Slightly more than 5% of the design discharge
D. None of these
ANS: B
Q No: 278
As compared to fresh river water, sea water contains oxygen
A. 10% less
B. 20% less
C. 10% more
D. 20% more
ANS: B
Q No: 279
Flocculated particles do not change their
A. Size
B. Shape
C. Weight
D. None of these
ANS: D
Q No: 280
Imhoff cone is used to determine
A. Settleable solids
B. Suspended solids
C. Dissolved solids
D. None of these
ANS: A
Q No: 281
For providing an Indian type W.C., the R.C.C. slabs in the toilet portion
A. Should be sunk by 20 cm
B. Should be kept 20 cm above the adjacent portion
C. Should be sunk by 50 cm
D. Need not be sunk
ANS: C
Q No: 282
Discrete or granular particles change their
A. Size
B. Shape
C. Weight
D. None of these ANS: D
Q No: 283
The sewer pipe which carries sewage from a building for immediate disposal is
A. House sewer
B. Lateral sewer
C. Intercepting sewer
D. Main sewer
ANS: A
Q No: 284
The ratio of design discharge to the surface area of a sedimentation tank is called
A. Surface loading
B. Overflow rate
C. Overflow velocity
D. All of these
ANS: D
Q No: 285
In SI units the power of sound is represented in
A. Kgs
B. Joules
C. Newtons
D. Watts
ANS: D
Q No: 286
Which one of the following resists hydrogen sulphide corrosion?
A. R.C.C.
B. Glazed stone wares
C. Asbestos cement
D. Glazed ware
ANS: D
Q No: 287
The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is
A. 0.68 m
B. 0.88 m
C. 1.36 m
D. 1.76 m
ANS: C
Q No: 288
In olden days the type of section adopted in trunk and out fall sewers was
A. Parabolic shaped
B. Horse shoe shaped
C. Egg shaped
D. Circular shaped
ANS: B
Q No: 289
For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed
A. 3 ppm
B. 4 ppm
C. 5 ppm
D. 10 ppm
ANS: B
Q No: 290
In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is
A. 2.25
B. 2.50
C. 2.55
D. 2.65
ANS: D
Q No: 291
The coagulant widely used for sewage treatment, is
A. Alum
B. Ferric chloride
C. Ferric sulphate
D. Chlorinated copperas
ANS: B
Q No: 292
House connections to the laterals is generally made by
A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares
ANS: D
Q No: 293
The ratio of minimum hourly flow to the average flow of sewage is
A. 1/4
B. 1/3
C. 1/2
D. 3/4
ANS: B
Q No: 294
In R.C. sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept
A. 10.0
B. 5.0
C. 2.0
D. 0.25
ANS: D
Q No: 295
Removal of oil and grease from sewage, is known
A. Screening
B. Skimming
C. Filtration
D. None of these
ANS: B
Q No: 296
Rate of flow of sewage is generally assumed
A. More than the rate of water supply
B. Equal to the rate of water supply
C. Less than the rate of water supply
D. At 150 litres per capita
ANS: D
Q No: 297
The gradient of sewers depends upon
A. Velocity of flow
B. Diameter of the sewer
C. Discharge
D. All the above
ANS: D
Q No: 298
If the depth of partial flow in a sewer of diameter 2 m, is 50 cm, its wetted perimeter is
A.
B. /2
C. /3
D. 2 /3
ANS: D
Q No: 299
The standard B.O.D. of water is taken for
A. 1 day
B. 2 days
C. 3 days
D. 5 days
ANS: D
Q No: 300
In sewers the gas generally found, is
A. Hydrogen sulphide (H2S)
B. Carbon dioxide (CO2)
C. Methane (CH4)
D. All the above
ANS: D
Q No: 301
Fresh sewage may become stale in
A. One hour
B. Two to three hours
C. Three to four hours
D. Six hours
ANS: C
Q No: 302
The small sewers are cleaned by
A. Flushing
B. Cane rodding
C. Wooden pills
D. None of these
ANS: A
Q No: 303
The sewage discharge in a detritus tank of a treatment plant is 576 litres/sec with flow velocity of 0.2 m/sec. If the ratio of width to depth is 2, the depth is
A. 100 cm
B. 110 cm
C. 120 cm
D. 150 cm
ANS: C
Q No: 304
If is the diameter of upper circular portion, the area of cross-section of a standard egg shaped sewer, is
A. D²
B. D²
C. D²
D. D²
ANS: A
Q No: 305
Drop manholes at the junctions of sewer lines, are provided if
A. Invert level of a branch sewer is more than 60 cm that of the main sewer
B. Sewer line runs along a main road
C. Ordinary manhole cannot be built
D. Two sewer lines intersect
ANS: A
Q No: 306
In sewage, the solids in mg per litre is
A. 100 to 500
B. 500 to 1000
C. 1000 to 1500
D. 1500 to 2000
ANS: B
Q No: 307
During purification process of sewage the gas given off, is
A. Carbon dioxide
B. Hydrogen
C. Ammonia
D. All the above
ANS: D
Q No: 308
The gas evolved in sewers is
A. Carbondioxide
B. Hydrogen sulphide
C. Methane
D. All of these
ANS: D
309. The sewerage system originates from
A. House sewers
B. Lateral sewers
C. Branch sewers
D. Main sewers
ANS: A
310. If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains
A. Hydrogen sulphide
B. Carbon dioxide
C. Methane
D. Oxygen
ANS: A
311. In septic tanks, decomposition of organic bacteria, is done by
A. Anaerobic bacteria
B. Aerobic bacteria
C. Both types of bacterias
D. None of these
ANS: A
312. The sewer which transports the sewage to the point of treatment, is called
A. House sewer
B. Out-fall sewer
C. Branch sewer
D. Main sewer
ANS: B
313. Sewer pipes need be checked for
A. Minimum flow
B. Maximum flow
C. Both A. and B.
D. None of these
ANS: C
314. To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of
A. Hydrochloric acid
B. Sulphuric acid
C. Nitric acid
D. Citric acid
ANS: B
315. hydraulically equivalent, the relationship which holds good, is
A. D8/3 = 4 b8/3
B. D3/8 = 4 b3/8
C. D2/3 = 4 b2/3
D. D3/2 = 4 b3/2
ANS: A
316. If the diameter of a sewer is 100 mm, the gradient required for generating self cleansing velocity is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. None of these
ANS: A
317. Aerobic activity is maximum
A. In freshly produced sewage
B. At sewer pipes
C. In sewer treatment plants
D. None of these
ANS: A
318. In 1000 kg of sewage, the total solids approximate
A. 0.5 to 1.0 kg
B. 1 kg to 2.0 kg
C. 5 kg to 7.5 kg
D. 7.5 kg to 10 kg
ANS: A
319. Sewer manholes are generally provided at
A. The change of gradient
B. The change of direction
C. The junctions of sewers
D. All of these
ANS: D
320. Before discharging the foul sewage into rivers, it is generally treated by
Waste Water Engineering Multiple Choice Questions on “Chemical Reactions Associated with Water Treatment”.
1. The chemical composition of wastewater naturally reflects the origin from which it came. a) True b) False Answer: a Clarification: Wastewater is the liquid end-product, or by-product, of municipal, agricultural, and industrial activity. As such, the chemical composition of wastewater naturally reflects the origin from which it came.
2. The world’s available fresh water supply is about _______ percent of that total water supply. a) 10 b) 4 c) 3 d) 7 Answer: c Clarification: The world’s available fresh water supply is about 3 percent of that total water supply. Only 20 percent of this amount is available for use in drinking water supplies. The remainder of the world water is salt water, which is costly to desalinate for drinking water purposes.
3. Which of the following related to the aerobic organic matter is true? a) Essential nutrients for growth b) Development of sludge deposits c) Growth of undesirable aquatic life d) Development of septic conditions Answer: d Clarification: Both nitrogen and phosphorus are essential nutrients for growth. These nutrients can lead to the growth of undesirable aquatic life. Their biological stabilization can lead to the depletion of natural oxygen resources and to the development of septic conditions.
4. ______ tend to resist conventional methods of wastewater treatment. a) Suspended solids b) Nutrients c) Refractory organics d) Priority pollutants Answer: c Clarification: Refractory organics tend to resist conventional methods of wastewater treatment. Typical examples include surfactants, phenols, and agricultural pesticides.
5. The quality of the fish habitat begins to increase when the dissolved oxygen concentration drops below 4 or 5 mg L-1. a) True b) False Answer: b Clarification: The quality of the fish habitat begins to decrease when the dissolved oxygen concentration drops below 4 or 5 mg L-1. Even if the receiving stream is at saturation, which is unlikely, that leaves only 3 or 4 mg L-1 of oxygen to be used for assimilation of the wastewater discharge.
6. Organic matter + nutrients + O2 → CO2 + H2O + _______ a) Biomass b) O2 c) Nutrients d) Organic matter Answer: a Clarification: This is the general form of the equation for decomposition of organic matter during the BOD test. It should be noted that oxygen is consumed in the reaction and biomass is the catalyst for the reaction.
7. 2NH3 +3O2 -> 2NO2– + ___ + 2H2O. a) O2 b) 2H+ c) H+ d) 2O2 Answer: b Clarification: This equation represents the first step of nitrification. Ammonia combines with oxygen to give nitrite and water in the presence of nitrosomonas bacteria. Two hydrogen free radicles are produced.
8. Which among these is the alternative BOD test for determining the oxygen consuming potential of a wastewater sample? a) ThOD b) COD c) BOD d) TOC Answer: b Clarification: An alternative to the BOD test for determining the oxygen consuming potential of a wastewater sample is the chemical oxygen demand (COD) test. As the name implies, the carbonaceous oxygen demand is oxidized chemically in the COD test.
9. What does SWOT stand for? a) Solid Waste Operation and Treatment b) Storm Water Operation and Treatment c) Supercritical Water Oxidation d) Storm and Wastewater Operation and Treatment Answer: c Clarification: Supercritical water oxidation (SCWO) is an intensive version of the WAO process. SCWO has become a rapidly developing innovative waste treatment technology for the oxidation of organic wastes and hazardous materials in water.
10. What is the combination of using a photocatalyst and UV or visible light for the treatment of wastewater and gaseous pollutants is called? a) Photocatalysis b) Super critical water oxidation c) Advanced oxidation process d) Wet air oxidation Answer: a Clarification: Photocatalysis is the combination of using a photocatalyst and UV or visible light for the treatment of wastewaters and gaseous pollutants. When illuminating a photocatalyst using UV or visible light, various organic compounds can be oxidized and mineralized at the photocatalyst surface or oxidized in solution ambient and atmospheric condition.
11. What is stoichiometry? a) A quantitative relationship between reactants and products b) Defines a qualitative value of the reactants and products c) Defines the quantity of reactants and products upon reaching equilibrium d) It defines quantity of only reactants Answer: a Clarification: Stoichiometry is a quantitative relationship between reactants and products. This is arrived only after balancing a chemical equation. This is required to calculate the rate of a reaction.
12. What is the rate of a chemical reaction not dependent on? a) Stoichiometry b) Surface area of reactants c) Temperature d) Pressure Answer: d Clarification: The rate of a reaction is independent of the pressure. Stoichiometry is the basis on which the rate of a reaction is defined. Greater the surface area of the reactants, greater is the rate of a reaction.
13. How is iconic strength related to total dissolved solids? a) I= (2.5 x 10-5)TDS b) I = (2.5 × 105) TDS c) I= 2.5 TDS d) I = 2.5 x10 TDS Answer: a Clarification: I = (2.5×10-5) TDS .This correlation was defined by Stumm and Morgan in 1996. The ionic strength can be found if the TDS is known. TDS is measured in mg/L.
14. In solutions as ionic concentration increases a non-ideal condition arises. To account for this non-ideal condition due to the ion-ion interaction what is the effective concentration term called as? a) Activity b) Dielectric constant c) Ionic coefficient d) Ionic strength Answer: a Clarification: Activity is the effective concentration term used to account for the non-ideal conditions encountered due to ion-ion interaction. Activity is defined at 1 atm pressure and 298.15 K temperature. It is measured in mol/L (M).
15. In dilute solutions which are normally encountered in water treatment what is the value of the activity of coefficient assumed? a) 0.5 b) 0.75 c) 1.0 d) >1 Answer: c Clarification: In dilute solutions usually encountered in water treatment the activity of coefficient assumed is 1. For electrolytes the activity coefficient is assumed <1 and for non-electrolytes >1.
16. What will be the activity coefficient of a solution consisting of monovalent ions? a) Equal to 1 b) >1 c) Close to 1 d) <0 Answer: c Clarification: The activity coefficient of a solution consisting of monovalent ions would be close to 1. For water supplies usually, the ionic strength is <5millimole/L. The Davies Equation is used to calculate the activity for concentrated solutions <0.1 M.
17. In case of Moving Bed Bioreactor and Activated Sludge process which is the factor that limits the rate of the reaction? a) temperature b) pressure c) pH d) ionic composition Answer: a Clarification: Temperature limits the rate of reaction in case of both Moving bed bioreactor and Activated Sludge Process. As temperature increases the rate of the reaction increases. But beyond a value of the temperature the rate decreases, as the enzymes present in the bacteria get deactivated.
18. What is the value of activity coefficients for monovalent and divalent ions for a potable water at an ionic strength of 0.01 M? a) 0.9 and 0.66 respectively. b) 0.9 in both the cases c) 0.66 and 0.9 respectively. d) 0.66 in both the cases Answer: a Clarification: The value of the activity coefficient for the monovalent ion is 0.9. The value of the activity coefficient for the divalent ion is 0.66. The activity coefficients for neutral species is negligible.
19. In water treatment which factor which has a major control over reaction selectivity and product distribution? a) pH b) temperature c) pressure d) ionic concentration Answer: a Clarification: The pH has a major control over reaction stability and product distribution. The pH determines whether the reactant species are catalyst or ionic. Control of the pH will result in an acceleration of desired pathways.
20. The degradation of BOD is classified as what type of reaction? a) First Order Reaction b) Zero Order Reaction c) Second Order Reaction d) Third Order Reaction Answer: a Clarification: The degradation of Biological Oxygen Demand is classified as First Order Reaction. rL =− kLL. This is the equation that depicts the degradation of BOD. Here rL represents the rate of reaction, kL represents coefficient of rate of degradation of BOD and L represents the BOD concentration.
Waste Water Engineering Multiple Choice Questions on “Types of Settling Tank”.
1. _______ is a process by which particles settle to the bottom of the liquid. a) Settling b) Coagulation c) Sedimentation d) Filtration Answer: a Clarification: The process by which particulates settle at the bottom of a liquid and form sediment is called settling. Particles experience a force, either due to gravity or due to centrifugal motion and tend to move in a uniform manner.
2. Settling tanks are also called as sedimentation tanks. a) True b) False Answer: a Clarification: Settling tanks are also referred to as sedimentation tanks. The process by which particulates settle at the bottom of a liquid and form sediment at the bottom of the vessel is called settling.
3. Which is the primary force acting on the Settleable particles? a) Gravitational force b) Centrifugal force c) Mechanical force d) Radial force Answer: a Clarification: The applied force such as gravity and a drag force that is due to the motion of the particle through the fluid. The applied force is not affected by the particle’s velocity. The drag force is a function of the particle velocity.
4. How many types of settling are present? a) 2 b) 3 c) 4 d) 6 Answer: c Clarification: There are four types of settling present. Type 1 is for non-flocculent particles, type 2 is for flocculent particles, type 3 is called as a zone or hindered settling, type 4 is called as compression settling.
5. Type III settling is called as hindered settling. a) True b) False Answer: a Clarification: Close particles that hinder interparticle forces and the settling of neighbouring particles, settle at a constant velocity and settle in secondary clarifiers in type III settling.
6. What is type IV settling also called as? a) Zone settling b) Hindered settling c) Compression settling d) Expansion settling Answer: c Clarification: In a high concentration settling where the particles touch each other and settling can occur only by compression of the compacting mass is called compression settling.
7. What is the product obtained when a coagulant is mixed with wastewater? a) Sediments b) Acid c) Floc d) Grit Answer: a Clarification: The most commonly used coagulant is alum. A coagulant combines with the impurities in wastewater and forms an end product called as flocs which is greater in diameter and can be easily removed.
8. Which mode of settling are tube settlers based on? a) Counter current settling b) Cocurrent settling c) Cross flow settling d) Flocculant settling Answer: a Clarification: Settling in tubesettler is based on counter current settling. Solids that settle down, move due to gravity. These constitute various plastic shaped geometries that enhance the settling characteristics of the sedimentation basin.
9. In countercurrent settling how is the solid suspension fed? a) From the bottom b) From the sides c) From the top d) Flow is up the plates Answer: c Clarification: In countercurrent settling the solid suspension is fed from the top. The time taken for a particle to settle in both countercurrent/co-current settling is the same. The direction in which the feed is fed is different.
10. How is the length of the surface calculated in case of countercurrent settling? a) Lp=wVƟ/ v cos Ɵ b) Lp=(VƟ – V sinƟ)/ v cos Ɵ c) Lp=w(VƟ – V sinƟ) d) Lp=w(VƟ – V sinƟ)/ v cos Ɵ Answer: d Clarification: The length of the surface is calculated as Lp=w (VƟ– V SinƟ)/ v cos Ɵ. Where LƟ is the length of the surface. V is the settling velocity. W is the perpendicular distance. Ɵ is the angle of surface inclination.
11. When will the particles settle in a tank which is subjected to countercurrent settling? a) V<(VƟ – V sinƟ)/v cosƟ b) V>= VƟ/v cosƟ c) V>= (VƟ – V sinƟ)/v cosƟ d) VƟ/v cosƟ Answer: c Clarification: The particles will settle in a tank when V>= (VƟ – V sinƟ)/v cosƟ. Where V is the settling velocity. Ɵ is the angle of surface inclination.
12. Lamella Clarifier works on which principle? a) Cocurrent settling b) Countercurrent settling c) Cross flow settling d) Hindered settling Answer: b Clarification: Lamella Clarifier works on Countercurrent settling. The feed is fed by a feed duct to the feed box. The flow is directed downwards towards individual side-entry plate slots.
13. How is the length of the surface of a settling tank determined in case of cross- flow settling? a) Lp=wVƟ/ v cos Ɵ b) Lpc) Lp= (VƟ – V sinƟ)/ v cos Ɵ d) Lp<(VƟ – V sinƟ)/ v cos Ɵ Answer: a Clarification: The length of the settling tank in case of cross flow settling is determined as Lp=wVƟ/ v cos Ɵ .Where Lp is the length of the surface. V is the settling velocity. W is the perpendicular distance. Ɵ is the angle of surface inclination.
14. How is the area of a sludge thickening tank calculated? a) A=2QTa/H0 b) A=QTa/H0 c) A=QTa/2H0 d) A=QTa/H02 Answer: b Clarification: The area of the sludge thickening tank is calculated as A=QTa/H0. Where A is the area of the sludge thickening tank. Q is the flow rate. Ta is the time to reach the desired underflow concentration. H0 is the initial height of the interface column.
15. How is the critical concentration of sludge thickener tank calculated? a) Hu= C02 H0/ Cu b) Hu= C0 H0/ Cu2 c) Hu= Cu H0/ CoS d) Hu= C0 H0/ Cu Answer: d Clarification: The critical concentration is calculated as Hu= C0 H0/ Cu. Where Hu depth at which the solids are under the desired underflow concentration. Cu is the desired underflow concentration.
16. What is the major assumption made when solid flux method is used to find the area of the sedimentation basin? a) Settling basin is not operating at a steady state b) Settling basin is operating at an adiabatic state c) Settling basin is operating at a steady state d) Settling basin is operating at an isobaric state Answer: c Clarification: Settling basin is operating at a steady state. This is the assumption made when the area of the sedimentation basin is to be calculated by the solid flux analysis method. The downward flux of the solids is brought about by gravity.
17. How is the height of the sludge calculated in a sludge drying bed? a) Ht-Hx=(H2-Hx)eit2 b) Ht=(H2-Hx)eit2 c) Ht-Hx=(H2)eit2 d) Ht-Hx=(Hx)eit2 Answer: a Clarification: The height of the sludge in a sludge drying bed due to compression settling is calculated as Ht-Hx= (H2-Hx)eit2 where Ht is the height of the sludge at time t. Hx is the height of sludge after 24 hrs. H2 height of sludge after 2 days. i is a constant for a given suspension.
