Category: WASTE WATER Engineering Objective Questions

250+ TOP MCQs on Trickling Filters – 2 and Answers

Waste Water Engineering MCQs on “Trickling Filters – 2”.

1. For rock type high filtration rate trickling filters what would be the recycling ratio assumed?
a) 0
b) 1-2
c) >2
d) >3
Answer: b
Clarification: For rock type high filtration, the recycling ratio would be 1-2. In case of intermediate filtration, this ratio is a little different. It is around 0-1. In case of plastic type filtration, the rate of recycle ratio is also 1-2.

2. For rock type low filtration rate trickling filters what would be depth assumed while designing it?
a) 1.8-2.4 m
b) <1.8 m
c) 3-12.2 m
d) >12.2 m
Answer: a
Clarification: For rock type low filtration, the depth assumed is around 1.8-2.4 m while designing it. It is assumed as 1.8-2.4 m even for intermediate filtration. It is assumed as 1.8-2.4 m for high rate filtration trickling filters also.

3. For plastic type high filtration rate trickling filters what would be depth assumed while designing it?
a) 1.8-2.4 m
b) <1.8 m
c) 3-12.2 m
d) >12.2 m
Answer: c
Clarification: For plastic type high filtration, the depth assumed is around 3-12.2 m while designing it. It is different for roughing type trickling filters. It is assumed as 0-2.

4. For rock type low filtration rate tricking filters what would be the BOD removal rate?
a) 50-80%
b) 50-90%
c) 80-90%
d) 40-70%
Answer: c
Clarification: For rock type low filtration rate trickling filters, the BOD removal efficiency is 80-90%. This is lower in case of rock type intermediate filtration trickling filters. It is around 50-80% only.

5. For rock type high filtration rate trickling filters what would be the BOD removal rate?
a) 50-80%
b) 50-90%
c) 80-90%
d) 40-70%
Answer: b
Clarification: For rock type high filtration rate trickling filters, the BOD removal efficiency is 50-90%. This is lower than rock type low filtration rate trickling filters. The BOD removal efficiency of high filtration rate filters is similar to that of intermediate filtration rate filters.

6. For plastic type high filtration rate trickling filters what would be the BOD removal rate?
a) 50-80%
b) 60-90%
c) 80-90%
d) 40-70%
Answer: b
Clarification: For plastic type high filtration rate trickling filters, the BOD removal efficiency is 60-90%. This is lower than rock type low filtration rate trickling filters. The BOD removal efficiency rate is highest only when low filtration rate type trickling filters are used.

7. For roughing type trickling filters what would be the BOD removal rate?
a) 50-80%
b) 60-90%
c) 80-90%
d) 40-70%
Answer: d
Clarification: For roughing type trickling filters, the BOD removal efficiency is 40 -70 %. This roughing type filters can be both plastic and rock type. In both the cases, the removal efficiency is 40-70%.

8. In which type of trickling filter very low power is consumed?
a) Low or standard filtration rate(Rock type)
b) Intermediate filtration rate (Rock type)
c) High filtration rate (Rock type)
d) High filtration rate (Plastic type)
Answer: a
Clarification: Depending on the filtration rates, the trickling filters can be classified as high, low rate or intermediate filtration rate trickling filters. The minimum power consumed is when utilizing low or standard filtration rate rock type tricking filters. Around 2-4 KW/103m3 is consumed.

9. In which type of trickling filter very high power is consumed?
a) Low or standard filtration rate(Rock type)
b) Intermediate filtration rate (Rock type)
c) High filtration rate (Rock type)
d) Roughing (Plastic/Rock type)
Answer: d
Clarification: Depending on packing material for the trickling filters it has been classified into 2 types. Rock and plastic type. The roughing type trickling filter which can constitute either rock or plastic packing consumes the highest power. This is around 10-20 KW/ 103m3.

10. In which type of trickling filter is nitrogen oxidized?
a) Low or standard filtration rate(Rock type)
b) Intermediate filtration rate (Rock type)
c) High filtration rate (Rock type)
d) Roughing (Plastic/Rock type)
Answer: a
Clarification: In the low or standard filtration rate type trickling filter, the filter packing is only at the top from 0.6-1.2 m. Hence the lower portions are populated by autotrophic nitrifying bacteria. This oxidises the ammonia nitrogen to nitrite and nitrate forms.

11. When filled which of the following material only nitrogen is removed?
a) River rock (Large)
b) River rock (Small)
c) Plastic conventional
d) Plastic random packing-conventional
Answer: b
Clarification: The trickling filters usually constitute rock or plastic packing. The trickling filters remove BOD/ nitrogen. When it is filled only with River rock (small) then it was noticed that only the nitrogen was removed by oxidizing the ammonia nitrogen to nitrite and nitrate.

12. When filled which of the following material both nitrogen and BOD are removed?
a) River rock (Large)
b) River Rock (Small)
c) Plastic High specific area
d) Plastic random packing-high specific area
Answer: a
Clarification: The trickling filters usually constitute rock or plastic packing. The trickling filters remove BOD/ nitrogen. When it is filled only with River rock (large) then it was noticed that both BOD and nitrogen get removed.

13. What is the surface area of the plastic high specific surface area packing material used in trickling filters as the packing medium?
a) 60 m2/m3
b) 90 m2/m3
c) 140 m2/m3
d) 45 m2/m3
Answer: c
Clarification: The surface area for the plastic medium high specific surface area is about 140 m2/m3. This removes only Nitrogen. The void space is >94%.

14. What is the surface area of the plastic conventional packing material used in trickling filters as the packing medium?
a) 60 m2/m3
b) 90 m2/m3
c) 140 m2/m3
d) 45 m2/m3
Answer: b
Clarification: The surface area for the plastic medium of the conventional type is about 90 m2/m3. This removes both Nitrogen and BOD. The void space is >95%.

15. What is the surface area of the plastic random packing conventional packing material used in trickling filters as the packing medium?
a) 60 m2/m3
b) 90 m2/m3
c) 98 m2/m3
d) 150 m2/m3
Answer: c
Clarification: The surface area for the plastic random packing of the conventional type packing material is about 98 m2/m3. This removes both Nitrogen and BOD. The void space is around 80%.

16. What is the surface area of the plastic random packing high specific surface area packing material used in trickling filters as the packing medium?
a) 60 m2/m3
b) 90 m2/m3
c) 98 m2/m3
d) 150 m2/m3
Answer: d
Clarification: The surface area for the plastic random packing high specific area is about 150 m2/m3. This removes only Nitrogen. The void space is around 70%.

17. What is the surface area of the River rock (Small) packing material used in trickling filters as the packing medium?
a) 60 m2/m3
b) 90 m2/m3
c) 98 m2/m3
d) 150 m2/m3
Answer: a
Clarification: The surface area for the River rock (Small) packing material is about 60 m2/m3. This removes only Nitrogen. The void space is around 50%.

18. What is the surface area of the River rock (Large) packing material used in trickling filters as the packing medium?
a) 60 m2/m3
b) 90 m2/m3
c) 45 m2/m3
d) 150 m2/m3
Answer: c
Clarification: The surface area for the River rock (Large) packing material is about 45 m2/m3. This removes both Nitrogen and BOD. The void space is around 60%.

19. The settling tank which is followed after the Trickling filter has which of the following characteristic?
a) Recirculation is present
b) Low suspended solids
c) The sludge from here is returned to the primary clarifier directly.
d) Has high BOD
Answer: b
Clarification: The settling tank which is followed after the tricking filter usually constitutes very low suspended solids. They differ from the activated sludge process by not having a recirculation system. The sludge from these systems is processed in the sludge disposal system which is then sent to the primary clarifier.

20. What is the maximum reduced concentration of BOD obtained at the outlet of tricking filter?
a) 40 mg/L
b) 20 mg/L
c) 30 mg/ L
d) 45 mg/L
Answer: b
Clarification: The concentration of BOD obtained at the outlet of the trickling filter is 20 mg/L. The concentration of TSS obtained at the outlet of the trickling filter is around 20 mg/L. This is the maximum value of BOD or TSS that can be obtained at the output of a trickling filter.

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250+ TOP MCQs on Moving Bed Bioreactor and Answers

Waste Water Engineering Multiple Choice Questions on “Moving Bed Bioreactor”.

1. MBBR provides support for both autotrophic and heterotrophic bacteria.
a) True
b) False
Answer: a
Clarification: Each individual biocarrier increases productivity through providing the protected surface area to support the growth of heterotrophic and autotrophic bacteria within its cells.

2. MBBR needs an assistance to maintain biofilm.
a) True
b) False
Answer: b
Clarification: This technology provides cost-effective treatment with minimal maintenance since MBBR processes self-maintain an optimum level of productive biofilm.

3. Which of the following is not correct with respect to MBBR?
a) Compact design
b) Expandable
c) Multiple pass process
d) Load responsive
Answer: c
Clarification: MBBR consists of a compact design which is a fraction of the size of conventional systems. It is expandable, single pass process that is there is no requirement of return activated sludge and is load responsive.

4. Which ions are present on the charged surface of MBBR?
a) Iron
b) Iodine
c) Aluminium
d) Sodium
Answer: c
Clarification: Charged surfaces on the media are biologically regenerated as ammonium ions which are adsorbed and then subsequently nitrified by the biofilm and desorbed.

5. The ions are desorbed after ______ by the biofilm.
a) Nitrified
b) Denitrified
c) Adsorbed
d) Absorbed
Answer: a
Clarification: Charged surfaces on the media are biologically regenerated as ammonium ions which are adsorbed and then subsequently nitrified by the biofilm and desorbed. These reactive surfaces increase treatment efficiency and buffer the biofilm communities against toxic compounds in the wastewater.

6. MBBR was developed based on the activated sludge process and _____
a) Sedimentation process
b) Clarifier process
c) Aeration process
d) Biofilter process
Answer: d
Clarification: Charged surfaces on the media are biologically regenerated as ammonium ions which are adsorbed and then subsequently nitrified by the biofilm and desorbed. These reactive surfaces increase treatment efficiency and buffer the biofilm communities against toxic compounds in the wastewater.

7. What part of the tank is used by MBBR for biomass growth?
a) 1/ 4
b) 1/ 2
c) 3/ 4
d) 1/ 1
Answer: d
Clarification: The biomass growth is seen in the entire tank. The whole tank is used in MBBR for biomass growth.

8. The biofilm carrier movement is caused by ________
a) Stirring
b) Horizontal shaft
c) Vertical shaft
d) Agitation by air
Answer: d
Clarification: The agitation set up by the air in the aerobic process causes biofilm carrier movement, while in anoxic and anaerobic processes a mixer (normally a horizontal shaft mounted banana mixer) keeps the carrier moving.

9. What is the shape of the biofilm carrier?
a) Circular
b) Rectangular
c) Square
d) Cylindrical
Answer: d
Clarification: The biofilm carrier is made of high density polyethylene and shaped like a small cylinder with a cross on the inside of the cylinder and “fins” on the outside.

10. What is the length of the cylinder?
a) 2 mm
b) 5 mm
c) 7 mm
d) 10 mm
Answer: c
Clarification: The cylinder has a length of 7 mm and a diameter of 10 mm (not including fins). Lately larger carrier of similar shape was introduced, intended for use in plants with coarse inlet sieves.

11. What is the diameter of the cylinder?
a) 5 mm
b) 7.5 mm
c) 10 mm
d) 12 mm
Answer: c
Clarification: The cylinder has a diameter of 10 mm (not including fins) and a length of 7 mm. A larger carrier of similar shape was introduced, intended for use in plants with coarse inlet sieves.

12. What is the standard filling degree of MBBR?
a) 50%
b) 55%
c) 67%
d) 72%
Answer: c
Clarification: One of the advantages of MBBR is that the filling of a carrier in the reactor may be subjected to preferences. The standard degree of filling of MBBR is 67% resulting in a total specific carrier area of 465m2/m3.

13. What is the retention time considered for aeration tanks in a moving bed bioreactor system?
a) 4hrs
b) 5-6 hrs
c) 6-8 hrs
d) 8-12 hrs
Answer: c
Clarification: The retention time considered for an aeration tank for moving bed bioreactor system is 6-8 hrs. In normal cases, without the media the retention time for aeration tank is considered as 8-10 hrs. The media in the moving bed bioreactor increases the surface area and reduces the tank size.

14. What is the surface area of the media used in these moving bed bioreactor systems?
a) 2000 m2
b) 3000 m2
c) 200-300 m2
d) 400-600 m2
Answer: d
Clarification: The media increases the surface area of the tank, thus results in a smaller tank size. Generally the media used in these moving bed bioreactors have the surface area in the range 400-600 m2. Recently there have been introductions of new media with a surface area close to 650-700m2.

15. What is the BOD removal level for moving bed bioreactor?
a) 3.5-4.5 Kg BOD/m3day
b) 2-2.75 Kg BOD/ m3day
c) 3 Kg BOD/ m3day
d) 5 Kg BOD/m3day
Answer: a
Clarification: The BOD removal for the moving bed bioreactor is 3.5-4.5 Kg BOD/m3day. The Moving bed bioreactor removes nitrogen also. These are provided with diffusers in order to provide aeration.

16. What is the combined BOD and nitrogen removal level for moving bed bioreactor?
a) 3-4 Kg BOD/m3
b) 2-2.75 Kg BOD/m3
c) 5 Kg BOD/m3
d) 6 Kg BOD/m3
Answer: b
Clarification: The combined BOD and nitrogen removal for the moving bed bioreactor is 2-2.75 Kg BOD/m3day. The Moving bed bioreactor removes BOD also. These are provided with diffusers in order to provide aeration.

17. Calculate the tank volume for the Moving bed bioreactor system for the following data.
Flow: 500 m3/h.
BOD: 500 mg/L
Retention time: 8 hrs
a) 800 m3
b) 4000 m3
c) 8000 m3
d) 5000 m3
Answer: b
Clarification: In this case as the BOD level is high, the retention time considered is 8 hrs. Volume of tank= Flow x Retention time. Volume= 500 X 8= 4000m3.

18. Calculate the tank volume for the Moving bed bioreactor system for the following data.
Flow: 800 m3/h.
BOD: 1500 mg/L
Retention time: 8 hrs
a) 5000 m3
b) 6400 m3
c) 8400 m3
d) 9200 m3
Answer: b
Clarification: In this case as the BOD level is high, the retention time considered is 8 hrs. Volume of tank= Flow x Retention time. Volume= 800 X 8= 6400m3.

19. Calculate the tank volume for the Moving bed bioreactor system for the following data.
Flow: 800 m3/h.
BOD: 300 mg/L
Retention time: 6 hrs
a) 4500 m3
b) 4800 m3
c) 6500 m3
d) 10500 m3
Answer: b
Clarification: In this case as the BOD level is not that high, hence the retention time considered is 6 hrs. Volume of tank= Flow x Retention time. Volume= 800 X 6= 4800m3.

20. Calculate the tank volume for the Moving bed bioreactor system for the following data.
Flow: 80 m3/h.
BOD: 300 mg/L
Retention time: 6 hrs
a) 500 m3
b) 600 m3
c) 480 m3
d) 120 m3
Answer: c
Clarification: In this case as the BOD level is not that high, hence the retention time considered is 6 hrs. Volume of tank= Flow x Retention time. Volume= 8 X 6= 480m3.

250+ TOP MCQs on Disc Filtration – 2 and Answers

Waste Water Engineering Questions and Answers for Aptitude test on “Disc Filtration – 2”.

1. What is the size of openings for a disc filter?
a) 20-35 µm
b) 10-20 µm
c) 20-30 µm
d) 5-10 µm
Answer: a
Clarification: The size of the opening for a disc filter is 20-35 µm. The disc filter removes suspended solids. During normal operation, 60-70% of the disc filter is submerged.

2. What is the hydraulic loading rate in m2/m3/h of a disc filter assumed while designing it?
a) 0.25-0.83
b) 0.02-0.083
c) 2.5-8.3
d) 8.3-10
Answer: a
Clarification: The hydraulic loading rate of a disc filter assumed while designing it is 0.25-0.83 m2/m3/h. This is measured in the units m2/m3/h. This depends on the suspended solids present in the waste water.

3. What is the head loss considered for the disc filter while designing it?
a) 75-150 mm
b) 40-70 mm
c) 150-175 mm
d) 175-200 mm
Answer: a
Clarification: The head loss considered for the disc filter while designing it is 75-150 mm. This is based on the submerged surface area of the disc. In most cases, it is considered as 100 mm.

4. What is the drum diameter considered while designing the disc filter?
a) 0.75-1.5 m
b) 2-3 m
c) 3-4 m
d) 4-5 m
Answer: a
Clarification: The drum diameter considered while designing the filter is 0.75-1.5 m. This varies depending on screen design. Smaller diameter results in greater time for backwash.

5. What is the drum speed considered while designing a disc filter?
a) 1.8 m/ min
b) 1 m/min
c) 6 m/min
d) 4.5 m/min
Answer: d
Clarification: The drum speed considered while designing a disc filter is 4.5 m/min. This however varies with the head loss. This holds good at 50mm head loss.

6. What is the drum speed considered while designing a disc filter at 150 mm head loss?
a) 30-40 m/min
b) 26 m/min
c) 20-25 m/min
d) 28 m/min
Answer: a
Clarification: The drum speed considered while designing a disc filter is 30-40 m/min. This however varies with the head loss. This holds good at 150mm head loss.

7. What is the hydraulic loading rate in m2/m3/h of a cloth disc filter assumed while designing it?
a) 0.1-0.27
b) 10-20
c) 2-4
d) 1-2
Answer: a
Clarification: The hydraulic loading rate of a cloth disc filter assumed while designing it is 0.1-0. 27 m2/m3/h. This is measured in. This depends on the suspended solids present in the waste water.

8. What is the head loss considered for the cloth disc filter while designing it?
a) 50-300 mm
b) 400-500 mm
c) 500 -600 mm
d) 600-700 mm
Answer: a
Clarification: The head loss considered for the cloth disc filter while designing it is 50-300 mm. This is based on the submerged surface area of the disc. In most cases, it is considered as 150-200 mm.

9. What is the drum diameter considered while designing the cloth disc filter?
a) 0.9-1.8 m
b) 2 m
c) 3-4 m
d) 5 m
Answer: a
Clarification: The drum diameter considered while designing the cloth filter is 0.9-1.8 m. This varies depending on screen design. Smaller diameter results in greater time for backwash.

10. What is the maximum NTU a disc filter can handle?
a) 25 NTU
b) 10 NTU
c) 50 NTU
d) 100 NTU
Answer: a
Clarification: The maximum NTU a disc filter can handle is 25 NTU. The removal efficiency is around 60-70%. This depends on the influent characteristics of the wastewater.

Waste Water Engineering for Aptitude test,

250+ TOP MCQs on Reverse Osmosis Membrane Properties – 2 and Answers

Tricky Waste Water Engineering Questions and Answers on “Reverse Osmosis Membrane Properties – 2”.

1. What is the permeate flux of UTC series?
a) 0.5
b) 0.8
c) 1
d) 3.3
Answer: b
Clarification: The permeate flux of the RO membrane UTC series is 0.8, BARC-TFC1 is 0.45, BARC-TFC2 is 0.55, NS-100 is 0.7, NS-200 is 0.8, NS-300 is 3.3, PA-300/RC-100 is 1 and CP is 0.06.

2. What is the percentage salt rejection of PES-1000?
a) 98 %
b) 99 %
c) 99.8 %
d) 99.9 %
Answer: d
Clarification: The percentage of salt rejection for RO membrane NS-100 is 99 %, NS-200 is 99.8 %, NS-300 is 68 %, PES-1000 is 99.9 %, PA-300/RC-100 is 99.4 % and FT-30 is 99%.

3. Which of these is true about reverse osmosis membranes?
a) They get hydrolysed at extreme low/ high pH conditions
b) They get hydrolysed at extreme high pH conditions
c) They get hydrolysed at extremely low pH conditions
d) They don’t get hydrolysed at extreme low/ high pH conditions
Answer: a
Clarification: The cellulose acetate membranes get hydrolysed at extreme low/ high pH conditions. Cellulose acetate membranes are 100 microns thick. Modern membranes are blend acetate cellulose membranes.

4. Which of these materials can be made into thin film composite?
a) Polyamide
b) Cellulose acetate
c) Cellulose triacetate
d) Polyethylene sulphate
Answer: a
Clarification: Polyamide membranes are used to make thin film composite membranes. These are available in hollow fibre sheets. These are also available in flat sheets.

5. Which of these pollutants cannot be tolerated by the hollow fibre sheets?
a) Free chlorine
b) BOD
c) COD
d) Free magnesium
Answer: a
Clarification: The pollutants which a hollow fibre sheet cannot handle is free chlorine. It causes irreversible damage to the fibre sheet. It affects the salt rejecting capacity.

6. What is the concentration of chlorine upto which these spiral wound membranes can withstand?
a) 2.0 ppm
b) 1.0 ppm
c) 1.5 ppm
d) 2.5 ppm
Answer: b
Clarification: The concentration upto which these membranes withstand chlorine concentration is 1 ppm. These membranes do not require pretreatment. They are less expensive as maintenance is less.

7. What is the diameter assumed for hollow fine membranes for treating sea water?
a) 90 microns
b) 95 microns
c) 100 microns
d) 105 microns
Answer: b
Clarification: The diameter assumed for hollow fine membranes for treating sea water is 95 microns. Du pont made the first hollow fine fibre. These membranes are self-supporting types.

8. What is the diameter assumed for hollow fine membranes for treating brackish water?
a) 90 microns
b) 95 microns
c) 85 microns
d) 80 microns
Answer: c
Clarification: The diameter assumed for hollow fine membranes for treating brackish water is 85 microns. Du pont made the first hollow fine fibre. These membranes are self -supporting types.

9. Which type of membrane exhibit low flux?
a) Isotropic
b) Anisotropic
c) Asymmetric
d) Tubular
Answer: a
Clarification: The membrane which exhibits very low flux is isotropic. These membranes exhibit high resistance to flow. Hence they have low flux.

10. Which type of membrane exhibit high flux?
a) Isotropic
b) Anisotropic
c) Symmetric
d) Tubular
Answer: b
Clarification: The membrane which exhibits very high flux is anisotropic. These membranes exhibit high salt rejection. These membranes have a very thin rejecting skin.

11. Which of these can be operated by turbulent flow?
a) Tubular
b) Spiral wound
c) Plate and frame
d) Hollow fibre
Answer: a
Clarification: The membrane which can be operated by turbulent flow is tubular type membrane. This reduces scaling and fouling. Thus this reduces the operation and maintenance cost.

12. What type of structure does the hollow fibre have?
a) Symmetric
b) Asymmetric
c) Isotropic
d) Anisotropic
Answer: b
Clarification: The hollow fibre membranes have asymmetric structure. These are produced as long capillary tubes. These do not require additional physical support.

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250+ TOP MCQs on Sanitary Fittings and Answers

Waste Water Engineering Multiple Choice Questions on “Sanitary Fittings”.

1. What is the preferred class of iron pipes?
a) A
b) B
c) C
d) D
Answer: c
Clarification: Galvanised iron pipes of class “C” is of first quality and should confirm to IS 1239. All pipes and fittings should be approved by the owner/ consultants prior to installation.

2. Cast iron pipes should confirm to IS 1729.
a) True
b) False
Answer: a
Clarification: Cast Iron pipes should be of approved quality and shall conform to IS 1729. These pipes shall be used wherever they are exposed and non-vertical.

3. What is the maximum specification for water cement ratio?
a) 0.2
b) 0.4
c) 0.6
d) 0.8
Answer: c
Clarification: The maximum specification for water cement ratio is 0.6. The concrete should be mixed on a clean surface and the water used for mixing should be clean potable water.

4. The mixing time of concrete prior to placement should not exceed 20 minutes.
a) True
b) False
Answer: a
Clarification: The concrete should be mixed on a clean surface and the water used for mixing should be clean potable water. The maximum specification for water cement ratio is 0.6.

5. What is the standard brick size?
a) 70*100*200
b) 75*115*225
c) 75*110*225
d) 75*115*220
Answer: b
Clarification: The bricks shall be clean and best available in the area. The bricks shall neither be over burnt nor underburnt. 75 x 115 x 225 is the standard size of the brick.

6. What is the expected depth tolerance in bricks?
a) 0.5 mm
b) 1.0 mm
c) 1.5 mm
d) 2.0 mm
Answer: c
Clarification: The expected tolerances are of 1.5mm in depth, 3mm in width & 6mm in length. The bricks when immersed in water for 24 hours shall not absorb more than 20% of its weight of water.

7. What is the preferred size of water closet pan?
a) 10”
b) 15”
c) 20”
d) 25”
Answer: d
Clarification: The preferred size of water closet pan is 25″ with “P” or “S” trap in white glazed earthenware. Low level flushing cistern of 15 litres capacity is used.

8. What is the capacity of the preferred low level flushing cistern?
a) 10 litres
b) 15 litres
c) 20 litres
d) 25 litres
Answer: b
Clarification: Low level flushing cistern of 15 litres capacity is used. Fordham is used with all the fittings and accessories with 32 mm flush chromium plates flush bend.

9. What is the diameter of flush pipe?
a) 30 mm
b) 32 mm
c) 34 mm
d) 36 mm
Answer: b
Clarification: The diameter of the flush pipe is 32mm. 12mm chromium plated tap with appropriate marks for cold or hot water.

10. What is the size of preferred taps for wash basins?
a) 10 mm
b) 12 mm
c) 14 mm
d) 15 mm
Answer: b
Clarification: 12mm chromium plated tap with appropriate marks for cold or hot water. 32 mm chromium plated brass waste coupling with rubber plug and chain. 12mm p.v.c. connector with wiped joints & 15mm chromium plated brass stop cock.

11. What is the depth of concrete required for half-round channels for surface drains?
a) 50 mm
b) 75 mm
c) 100 mm
d) 105 mm
Answer: b
Clarification: These shall be of best Indian make glazed chinaware and of specified size and must be bedded on 75mm thick concrete or cement mortars.

12. What is the ratio of cement to be used to plaster the drain at the bottom of the camber?
a) 1:1
b) 1:2
c) 2:4
d) 1:3
Answer: b
Clarification: The channel or drain at the bottom of the chamber shall be plastered with 1:2 cement and sand mortar and finished smooth to the grade. The channels and drains shall be shaped and laid to provide smooth flow.

13. What is the depth of brick masonry required in inspection chambers?
a) 1 m
b) 1.2 m
c) 1.5 m
d) 1.8 m
Answer: b
Clarification: Bed concrete PCC 1:3:6, 150mm thick with 150mm offsets on all sides beyond the Brick wall. Brick Masonry 230 thick all round up to the maximum depth of 1.20 meters in cement mortar 1:6.

14. What is the number of coats of paint required for manhole covers?
a) 1
b) 2
c) 3
d) 4
Answer: b
Clarification: Cast Iron heavy duty Manhole cover and frame suitable to the size of the chamber. The cover shall be painted in 2 coats of bituminous anti-corrosive paint. Cover shall be close fitting so as to prevent gases form coming out.

15. What is the quantity of powder required in 1000 litres of water for sterilization?
a) 100 grams
b) 150 grams
c) 200 grams
d) 250 grams
Answer: b
Clarification: The system shall be first flushed out with water and a does of 50 parts of chlorine to one Million parts of water. The proportions shall be 150 grams to 1000 litres of water for sterilization.

250+ TOP MCQs on Autoclaves and Answers

Waste Water Engineering Multiple Choice Questions on “Autoclaves”.

1. ________ is a pressure chamber used to carry out processes at high temperature and pressure.
a) Oven
b) Micro clave
c) Autoclave
d) Hot air oven
Answer: c
Clarification: An autoclave is a pressure chamber used to carry out industrial processes requiring elevated temperature and pressure different from ambient air pressure. Autoclaves are used in medical applications.

2. Autoclaves are used in the medical applications to perform ______
a) Vulcanization
b) Sterilization
c) Heating
d) Cleaning
Answer: b
Clarification: Autoclaves are used in medical applications to perform sterilization and in the chemical industry to cure coatings and vulcanize rubber for hydrothermal synthesis. There are other industrial applications also.

3. What is the common temperature used in autoclaves?
a) 121˚C
b) 109˚C
c) 135˚C
d) 142˚C
Answer: a
Clarification: Many autoclaves are used to sterilize the equipment and supplies by subjecting them to high-pressure saturated steam at 121 °C (249 °F) for around 15–20 minutes depending on the size of the load and the contents.

4. Who invented the autoclave?
a) Pasteur
b) Charles Chamberland
c) Arnold O. Beckman
d) Antonie van Leeuwenhoek
Answer: b
Clarification: Pasteur invented hot air oven. Charles Chamberland invented autoclave. Arnold O. Beckman invented pH meter. Antonie van Leeuwenhoek is considered as the father of microbiology.

5. All the trapped air is removed from the autoclave before activation.
a) True
b) False
Answer: a
Clarification: It is very important to ensure that all of the trapped air is removed from the autoclave before activation, as trapped air is a very poor medium for achieving sterility. Sterilization can be achieved in three minutes by steam at 134˚C.

6. A device that uses steam to sterilize equipment and other objects is a medical autoclave.
a) True
b) False
Answer: a
Clarification: Autoclaves are found in many laboratories, medical fields, institutions and other places that need to ensure the sterility of an object. This means that all bacteria, fungi, viruses and spores are inactivated.

7. What is the inner surface of autoclaves made of?
a) Mild steel
b) Stainless steel
c) Copper
d) Aluminum
Answer: b
Clarification: There is a horizontal and vertical type of autoclave. In vertical autoclaves, the whole autoclave is made of stainless steel and the outer surface is made of mild steel. Vertical autoclaves are used mainly for the sterilization process.

8. What is the operating temperature for table top steam sterilizer?
a) 110-115 ˚C
b) 121-130˚C
c) 121-135˚C
d) 121˚C
Answer: c
Clarification: The sterilization temperature for high pressure sterilizer of a rectangular model is 121˚C. The operating temperature for high pressure sterilizer of rectangular model is 121˚C to 135˚C.

9. The sterilizer of pressure cooker type is made of ________
a) Aluminium
b) Steel
c) Stainless steel
d) Copper
Answer: a
Clarification: The sterilizer of pressure cooker type is made of aluminium for quick transfer of heat, which generates steam under pressure. The sterilizer is subjected to the saturated steam environment for preset specified time as soon as it reaches the right temperature.

10. Which type of autoclaves is mainly used for bulk research work?
a) Vertical autoclave
b) Horizontal autoclave
c) Sterilization pressure cooker
d) Table top steam sterilizer
Answer: b
Clarification: Horizontal autoclaves are mainly used for institutions or laboratory for doing bulk sterilizing research work. These autoclaves have double walled inside and outside made of stainless steel of 304 quality.

11. Which type of control valve can be used for 90-degree change in direction of flow?
a) Butterfly valve
b) Diaphragm valve
c) Globe valve
d) Gate valve
Answer: c
Clarification: Globe valves are the only ones which can be used for 90 degree change in direction of flow. Specifically angle- globe valves are used for that purpose. Globe valves are not used for controlling pressure.

12. Which of these is a linear motion control valve?
a) Ball valve
b) Butterfly valve
c) Plug valve
d) Diaphragm valve
Answer: d
Clarification: Control valves are classified as linear and rotary motion valves. Diaphragm and Globe valves are classified as linear motion control valve. Whereas Ball, Butterfly and plug valves are classified as rotary motion control valves.

13. Which of the following is not a type of control butterfly valve?
a) Single off-set
b) Concentric
c) Triple off-set
d) Concentric centreline
Answer: b
Clarification: Control butterfly valves are of 4 types. Single offset, double offset, triple offset and concentric centreline. There is no type of control butterfly such as concentric.

14. What is inherent flow characteristics?
a) The curve obtained between control valve capacity and valve stem travel
b) The curve obtained between control valve capacity and Cv
c) The curve obtained between Cv and valve stem travel
d) The curve obtained between control valve capacity and pressure drop
Answer: a
Clarification: The curve between control valve capacity and valve stem travel is known as inherent flow characteristics. This curve is obtained at a constant pressure drop. The relationship between control valve capacity and valve stem travel is known as flow characteristic of the control valve.

15. Which type of valve is preferred for sequential operations?
a) Electric actuated control valve
b) Single acting control valve
c) Quick opening valve
d) Double acting control valve
Answer: c
Clarification: Quick opening valves are used for sequential processes. These are used in batch and semi-continuous process. These are self- actuated valves.

16. Which of these control valves has the lowest pressure recovery?
a) Globe valve
b) Ball valve
c) Butterfly valve
d) Plug valve
Answer: a
Clarification: Globe valves have lower pressure recovery than the ball, plug and butterfly valves. The velocity is very high at the vena contracta. As the liquid flows further down due to the increase in an area the velocity decreases and there is an increase in pressure. This phenomenon is known as pressure recovery.

17. Which type of actuator is preferred when high and fast stroking speed is required?
a) Direct acting actuator
b) Reverse acting actuator
c) Electro hydraulic actuator
d) Piston actuator
Answer: d
Clarification: Piston actuators are preferred when high and fast stroking speed is required. This type of actuator utilises air pressure upto 150psig. This eliminates the need for a pressure regulator.

18. Direct acting actuators fall under which category of actuator?
a) Diaphragm actuator
b) Piston actuator
c) Electro hydraulic actuator
d) Manual actuators
Answer: a
Clarification: Direct actuator is a type of Diaphragm actuator. Another type of diaphragm actuator is reverse acting actuator. The size of these actuators depends on the air supply required.

19. The gain of a control valve should never be less than _______
a) 1
b) 5
c) 0.5
d) 0.75
Answer: c
Clarification: The gain of a control valve should never be lesser than 0.5. Gain is defined as the ratio between the differences in flow to the differences in stoke or travel. In case the value is lesser than 0.5 then there would be a problem in controlling the valve.

20. What should be the rangeability of the control valve?
a) Gain
b) Cv
c) Turndown
d) Stoke%
Answer: c
Clarification: Rangeability should be greater than the turndown of a control valve. The ratio of the Cv at which the valve is fully open to the minimum Cv at which it can control is known as rangeability. Turndown is the ratio of the calculated Cv at the maximum condition to that of the Cv calculated at the minimum condition.