McqMate
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 |
Answer» D. All the above |
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 |
Answer» D. All the above |
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) |
Answer» C. Both (a) and (b) |
4. |
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 |
Answer» B. 22.5 cm c/c |
5. |
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 |
Answer» B. Smoke test |
6. |
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 |
Answer» D. All the above |
7. |
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 |
Answer» D. More than 500 |
8. |
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 |
Answer» A. Centrifugal pump |
9. |
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 |
Answer» D. 90 days |
10. |
The coagulant which is generally not used for treating the sewage, is |
A. | Alum |
B. | Ferric chloride |
C. | Ferric sulphate |
D. | Chlorinated copperas |
Answer» A. Alum |
11. |
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 |
Answer» C. Windrow |
12. |
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 |
Answer» C. Methane |
13. |
The gas which may cause explosion in sewers, is |
A. | Carbondioxide |
B. | Methane |
C. | Ammonia |
D. | Carbon monoxide |
Answer» B. Methane |
14. |
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 |
Answer» C. The gases produced in sludge digestion process, contain 75% carbon dioxide |
15. |
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 |
Answer» D. All the above |
16. |
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 |
Answer» D. 2 hours |
17. |
The Chezy's constant C in the formula V = C 𝑟𝑠 depends upon |
A. | Size of the sewer |
B. | Shape of the sewer |
C. | Roughness of sewer surface |
D. | All the above |
Answer» D. All the above |
18. |
To prevent settling down of sewage both at the bottom and on the sides of a large sewer, selfcleaning 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 |
Answer» D. 0.75 m/sec |
19. |
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 |
Answer» A. Both A and R are true and R is the correct explanation of A |
20. |
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 |
Answer» C. 50,000 to 60,000 litres/sqm/day |
21. |
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 |
Answer» D. All the above |
22. |
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 |
Answer» D. Water supply allowance per capita |
23. |
If q is the average sewage flow from a city of population P, the maximum sewage flow |
A. | Q = [(4 + 𝑝 )/(18 + 𝑝 )] q |
B. | Q = [(18 +p )/(4 + 𝑝 )] q |
C. | Q = [(18 + 𝑝 )/(4 + 𝑝 )] q |
D. | Q = [(5 + 𝑝 )/(15 + 𝑝 )] q |
Answer» D. Q = [(5 + 𝑝 )/(15 + 𝑝 )] q |
24. |
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 |
Answer» B. Carbon dioxide |
25. |
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 |
Answer» D. Cross-sectional area/wetted perimeter |
26. |
If the depth of flow in a circular sewer is 1/4th of its diameter D, the wetted perimeter is |
A. | 𝝅𝑫𝟐 |
B. | 𝝅𝑫𝟒 |
C. | 𝝅𝑫𝟑 |
D. | 𝝅𝑫 |
Answer» C. 𝝅𝑫𝟑 |
27. |
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 |
Answer» D. None of these |
28. |
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 |
Answer» B. Trickling filters |
29. |
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 |
Answer» A. A trunk sewer |
30. |
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) |
Answer» B. Concreting |
31. |
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 |
Answer» A. A sedimentation tank and an activated sludge treatment plant |
32. |
Imhoff cone is used to measure |
A. | Total organic solids |
B. | Total solids |
C. | Total in organic solids |
D. | Settleable solids |
Answer» D. Settleable solids |
33. |
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 |
Answer» D. Both (a) and (c) of above |
34. |
For the COD test of sewage, organic matter is oxidised by K2 Cr2O7 in the presence of |
A. | H2SO4 |
B. | HNO3 |
C. | HCl |
D. | None of these |
Answer» A. H2SO4 |
35. |
The sludge does not contain waste water from |
A. | Bath rooms |
B. | Wash basins |
C. | Kitchen sinks |
D. | Toilets |
Answer» D. Toilets |
36. |
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 |
Answer» B. Less than the self-cleansing velocity |
37. |
In sewers the effect of scouring is more on |
A. | Top side |
B. | Bottom side |
C. | Horizontal side |
D. | All sides |
Answer» B. Bottom side |
38. |
The sewer which resists sulphide corrosion, is |
A. | Brick sewer |
B. | Cast iron sewer |
C. | R.C.C. sewer |
D. | Lead sewer |
Answer» D. Lead sewer |
39. |
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) |
Answer» D. Q/(B × L) |
40. |
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 |
Answer» B. Crimp and Bruges |
41. |
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 |
Answer» B. Dissolved Oxygen (D.O.) |
42. |
Water content of sewage is about |
A. | 90 % |
B. | 95 % |
C. | 99 % |
D. | 9.9 % |
Answer» D. 9.9 % |
43. |
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 |
Answer» A. Used to remove the grease and oil |
44. |
The most efficient cross-section of sewers in a combined sewerage system is |
A. | ) Parabolic |
B. | Circular |
C. | Rectangular |
D. | New egged |
Answer» B. Circular |
45. |
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 |
Answer» A. 4 to 8 hours |
46. |
The factor responsible for purification of sewage in river is |
A. | Hydrology |
B. | Dissolved oxygen in water |
C. | Temperature |
D. | All the above |
Answer» D. All the above |
47. |
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) |
Answer» D. Both (B) and (C) |
48. |
To maintain aerobic biological activity, the moisture content of the compost mass should be about |
A. | 45 % |
B. | 50 % |
C. | 55 % |
D. | 60 % |
Answer» C. 55 % |
49. |
Pick up the correct statement from the following: |
A. | The larger the sewer in size, more will be |
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 |
Answer» D. The larger the sewer in size, deposition will take place |
50. |
The pH value of sewage is determined with the help of |
A. | Imhoff Cone |
B. | Turbid meter |
C. | Potentiometer |
D. | None of these |
Answer» C. Potentiometer |
51. |
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 |
Answer» B. 40,000 to 50,000 litres/sqm/day |
52. |
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 |
Answer» D. The depth of tank is kept equal to its width |
53. |
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 |
Answer» C. Separate system |
54. |
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 |
Answer» A. 30 litres/person/year |
55. |
Dried sewage after treatment is used as |
A. | Fertilizer |
B. | Building material |
C. | Chemical for lowering B.O.D. |
D. | Base material for paints |
Answer» A. Fertilizer |
56. |
For drains up to 15 cumecs, the depth “d” and “B” width are related by |
A. | d = 0.2 |
B. | d = 0.5 B |
C. | B = 0.2 d |
D. | B = 0.5 d |
Answer» B. d = 0.5 B |
57. |
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 |
Answer» B. Combined system |
58. |
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 |
Answer» C. Velocity at which no accumulation remains in the drains |
59. |
5 days-biochemical oxygen demand (BOD5) is taken at a temperature of |
A. | 0°C |
B. | 15°C |
C. | 20°C |
D. | 25°C |
Answer» C. 20°C |
60. |
A well oxidized sewage contains nitrogen mainly as |
A. | Nitrates |
B. | Nitrites |
C. | Free ammonia |
D. | None of these |
Answer» A. Nitrates |
61. |
In a sludge tank, the gas mainly produced, is |
A. | Oxygen |
B. | Nitrogen |
C. | Hydrogen |
D. | Carbon dioxide |
Answer» D. Carbon dioxide |
62. |
If “D” 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 |
Answer» D. 1.625 D |
63. |
In normal conditions, the period for sludge digestion, is |
A. | 10 days |
B. | 20 days |
C. | 30 days |
D. | 60 days |
Answer» C. 30 days |
64. |
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 |
Answer» D. An Imhoff cone |
65. |
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% |
Answer» C. 60 to 80% |
66. |
For design of sewers, percentage of sewage discharge is assumed |
A. | 65 to 70 |
B. | 70 to 75% |
C. | 75 to 80% |
D. | 85% |
Answer» C. 75 to 80% |
67. |
The grit chambers of sewage treatment plants, are generally cleaned after |
A. | 2 days |
B. | 7 days |
C. | 12 days |
D. | 14 days |
Answer» D. 14 days |
68. |
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) |
Answer» C. Both (a) and (b) |
69. |
The average temperature of sewage in India, is |
A. | 10°C (B) (C) (D) |
B. | 15°C |
C. | 20°C |
D. | 25°C |
Answer» C. 20°C |
70. |
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 |
Answer» C. Inlets are generally provided in all sewers |
71. |
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) (C) (D) |
B. | 50 % |
C. | 10 % |
D. | 5 % |
Answer» B. 50 % |
72. |
If ‘D’ 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 |
Answer» D. 1.625 D |
73. |
In trickling filter, B.O.D. is reduced to |
A. | 30 to 40% (B) (C) (D) |
B. | 40 to 60% |
C. | 60 to 80% |
D. | 80 to 90% |
Answer» C. 60 to 80% |
74. |
For design of sewers, percentage of sewage discharge is assumed |
A. | 65 to 70% (B) (C) (D) |
B. | 70 to 75% |
C. | 75 to 80% |
D. | 85% |
Answer» C. 75 to 80% |
75. |
The grit chambers of sewage treatment plants, are generally cleaned after |
A. | 2 days (B) (C) (D) |
B. | 7 days |
C. | 12 days |
D. | 14 days |
Answer» D. 14 days |
76. |
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 |
Answer» B. Aeration is done with an admixture of previously aerated sludge |
77. |
For detecting the nitrates in sewage, the colour may be developed by adding |
A. | Potassium permanganate (B) (C) (D) |
B. | Sulphuric acid and napthamine |
C. | Phenol-di-sulphuric acid and potassium hydroxide |
D. | None of these |
Answer» C. Phenol-di-sulphuric acid and potassium hydroxide |
78. |
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] |
Answer» B. Vs = 418 (Gs - Gw)d² [(3T + 70)/100] |
79. |
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 |
Answer» D. 150 m to 300 m |
80. |
Stone ware pipes are |
A. | Highly resistant to sulphide corrosion (B) (C) (D) |
B. | Highly impervious |
C. | Hydraulically efficient because of their smooth interior surface |
D. | Especially suited to pressure pipes |
Answer» D. Especially suited to pressure pipes |
81. |
The intensity of rain is expressed in |
A. | cm/minute (B) (C) (D) |
B. | cm/hour |
C. | cm/day |
D. | None of these |
Answer» B. cm/hour |
82. |
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 |
Answer» A. 1.095 |
83. |
Which one of the following part of human body withstands minimum radiation? |
A. | Thyroid |
B. | Kidneys |
C. | Eyes |
D. | Ovaries/testis |
Answer» D. Ovaries/testis |
84. |
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 |
Answer» D. Having drains at different levels |
85. |
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 |
Answer» B. 1 in 10 |
86. |
Primary treatment of sewage consists of removal of |
A. | Large suspended organic solids |
B. | Oil and grease |
C. | Sand and girt |
D. | Floating materials |
Answer» A. Large suspended organic solids |
87. |
Cement concrete sewers are only suitable if non-scouring velocity is between |
A. | ) 2.5 to 3.0 m/sec (B) (C) (D) |
B. | 3.0 to 4.0 m/sec |
C. | 3.5 to 4.5 m/sec |
D. | 4.5 to 5.5 m/sec |
Answer» A. ) 2.5 to 3.0 m/sec (B) (C) (D) |
88. |
The most widely used pump for lifting sewage is |
A. | Centrifugal pump |
B. | Reciprocating pump |
C. | Pneumatic ejector |
D. | Air pressure pump |
Answer» A. Centrifugal pump |
89. |
Setting out the alignments of sewers may start from |
A. | City |
B. | Out-fall |
C. | Tail end |
D. | Any point |
Answer» C. Tail end |
90. |
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 |
Answer» A. d² (0.011d + 0.785H)/Q |
91. |
Lead acetate test in sewer manhole is done to test the presence of |
A. | Methane gas (B) (C) (D) |
B. | Hydrogen sulphide |
C. | Carbondioxide gas |
D. | Diesel vapours |
Answer» B. Hydrogen sulphide |
92. |
Anti syphonage pipe is fitted |
A. | At the end of septic tanks (B) (C) (D) |
B. | On manholes |
C. | With a W.C. trap |
D. | At the beginning of sewer line |
Answer» C. With a W.C. trap |
93. |
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 |
Answer» D. All the above |
94. |
The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is |
A. | 1.5 (B) (C) (D) |
B. | 2.0 |
C. | 3.0 |
D. | 4.0 |
Answer» B. 2.0 |
95. |
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 |
Answer» A. More than 7 |
96. |
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 |
Answer» D. all of these |
97. |
Pick up the incorrect size of stone ware sewers |
A. | 52.5 cm (B) (C) (D) |
B. | 67.5 cm |
C. | 82.5 cm |
D. | None of these |
Answer» D. None of these |
98. |
Chlorination of water is done for the removal of |
A. | Bacterias |
B. | Suspended solids |
C. | Sediments |
D. | Hardness |
Answer» A. Bacterias |
99. |
Sludge banks are formed if sewage is disposed of in |
A. | Rivers |
B. | Seas |
C. | Lakes |
D. | None of these |
Answer» B. Seas |
100. |
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 |
Answer» D. Circular Imhoff double storey tanks without bottom hoppers |
Done Reading?