WorksheetsEVS - III
Total questions: 50
Worksheet time: 25mins
1. Which of the following retards the self purification of stream ?
a) higher temperature
b) sunlight
c) satisfying oxygen demand
d) none of the above
2. Sewage treatment units are normally designed for
a) 5-10 years
b) 15-20 years
c) 30-40 years
d) 40-50 years
3. Settling velocity increase with
a) specific gravity of solid particles
b) size of particles
c) depth of tank
d) temperature of liquid
4. Standard BOD is measured at
a) 200C – 1 day
b) 250C – 3 day
c) 200C – 5 day
d) 300C – 5 day
5. The correct relation between theoretical oxygen demand (TOD), Biochemical oxygen demand (BOD), and chemical oxygen demand (COD) is given by
a) TOD>BOD>COD
b) TOD>COD>BOD
b) TOD>COD>BOD
D) COD>BOD>TOD
6. Select the correct statement
a) 5 day BOD is the ultimate BOD
b) 5 day BOD is greater than 4 day BOD keeping other conditions same
c) 5 day BOD is less than 4 day BOD keeping other conditions same
d) BOD does not depend on time
7. If Biochemical oxygen demand(BOD) of a town is 20000 kg/day and BOD per capita per day is 0.05kg, then population equivalent of town is
a) 1000
b) 4000
c) 100000
d) 400000
8. The rate of BOD exerted at any time is
a) directly proportional to BOD satisfied
b) directly proportional to BOD remaining
c) inversely proportional to BOD satisfied
d) inversely proportional to BOD remaining
9. The ratio of 5 day BOD to ultimate BOD is about
a) 1/3
b) 2/3
c) 3/4
d) 1.0
10. In a BOD test, 1.0 ml of raw sewage was diluted to 100 ml and the dissolved oxygen concentration of diluted sample at the beginning was 6 ppm and it was 4 ppm at the end of 5 day incubation at 200C. The BOD of raw sewage will be
a) 100ppm
b) 200ppm
c) 300ppm
d) 400ppm
11. The minimum dissolved oxygen which should always be present in water in order to save the aquatic life is
a) 1ppm
b) 4ppm
c) 10ppm
d) 40ppm
12. The relative stability of a sewage sample, whose dissolved oxygen is same as the total oxygen required to satisfy BOD, is
a) 1
b) 100
c) infinity
d) zero
13. Dissolved oxygen in streams is
a) maximum at noon
b) minimum at noon
c) maximum at midnight
d) same throughout the day
14. Facultative bacteria are able to work in
a) presence of oxygen only
b) absence of oxygen only
c) presence as well as in absence of oxygen
d) presence of water
15. The means of access for inspection and cleaning of sewer line is known as
a) inlet
b) manhole
c) drop manhole
d) catch basin
16. Sewerage system is designed for
a) maximum flow only
b) minimum flow only
c) average flow only
d) maximum and minimum flow
17. Sewage treatment units are designed for
a) maximum flow only
b) minimum flow only
c) average flow only
d) maximum and minimum flow
18. Laying of sewers is usually done with the help of
a) a theodolite
b) a compass
c) sight rails and bonding rods
d) a plane table
19. Corrosion in concrete sewers is caused by
a) septic conditions
b) dissolved oxygen
c) chlorine
d) nitrogen
20. If the sewage contains grease and fatty oils, these are removed in
a) grit chambers
b) detritus tanks
c) skimming tanks
d) sedimentation tanks
21. Generally the detention period for grit chambers is kept as
a) 1 minute
b) 5 minute
c) 2 -4 hours
d) 12 hours
22. Which one of the following unit works in anaerobic conditions ?
a) sludge digestion tank
b) sedimentation tank
c) activated sludge treatment
d) trickling filters
23. Septic tank is a
i) settling tank
ii) digestion tank
iii) aeration tank
The correct answer is
a) only (i)
b) (i) and (iii)
c) (i) and (ii)
d) only (iii)
24. The maximum efficiency of BOD removal is achieved in
a) oxidation pond
b) oxidation ditch
c) aerated lagoons
d) trickling filters
25. The working conditions in imhoff tanks are
a) aerobic only
b) anaerobic only
c) aerobic in lower compartment and anaerobic in upper compartment
d) anaerobic in lower compartment and aerobic in upper compartment
26. In facultative stabilization pond, the sewage is treated by
a) aerobic bacteria only
b) algae only
c) dual action of aerobic bacteria and anaerobic bacteria
d) sedimentation
27. The detention period for oxidation ponds is usually kept as
a) 4 – 8 hours
b) 24 hours
c) 10 to 15 days
d) 3 months
28. Composting and lagooning are the methods of
a) sludge digestion
b) sludge disposal
c) sedimentation
d) filtration
29. The main disadvantage of oxidation pond is that
a) large area is required for construction
b) maintenance and operation cost are high
c) BOD removal is very low
d) none of the above
30. For satisfactory working of a sludge digestion unit, the pH range of digested sludge should be maintained as
a) 4.5 to 6.0
b) 6.5 to 8.0
c) 8.5 to 10.0
d) 10.5 to 12.0
31. Sludge volume index is defined as the ratio of
a) percentage of sludge by volume to percentage of suspended solids by weight
b) percentage of sludge by volume to percentage of total solids by weight
c) percentage of total solids by weight to percentage of sludge by volume
d) percentage of total solids by weight to percentage of sludge by volume
32. For normal sludge, the value of sludge index for Indian condition is
a) 0 to 50
b) 50 to 150
c) 150 to 350
d) 350 to 500
33. When there is no recirculation of sewage, then recirculation factor is
a) 0
b) 1
c) infinity
d) none of the above
34. A pipe which is installed in the house drainage to preserve the water seal of traps is called
a) vent pipe
b) antisiphonage pipe
c) waste pipe
d) soil pipe
35. In the two-pipe system of house plumbing, the pipes required for
a) one soil pipe, one waste pipe and one vent pipe
b) one soil pipe, two waste pipes and one vent pipe
c) one soil pipe, one waste pipe and two vent pipes
d) two soil pipes, one waste pipe and one vent pipe
36. The pipe which is used to carry the discharge from sanitary fittings like bathrooms, kitchens etc. is called
a) waste pipe
b) soil pipe
c) vent pipe
d) antisiphonage pipe
37. The gas from sludge digestion tank is mainly composed of
a) nitrogen
b) carbon dioxide
c) hydrogen sulphide
d) methane
38. Most of the bacteria in sewage are
a) parasitic
b) saprophytic
c) pathogenic
d) anaerobic
39. The process of lagooning is primarily a means of
a) reducing the excessive flow in sewers
b) disposing of sludge
c) increasing the capacity of storage reservoirs
d) increasing flow of sewage through imhoff tanks
40. The biochemical treatment of sewage effluents is essentially a process of
a) oxidation
b) dehydration
c) reduction
d) alkalinization
41. To divert excessive flow from combined sewers, the most commonly used weir is a
a) cipoletti weir
b) broadcrested weir
c) leaping weir
d) submerged weir
42. Chlorine is used in the treatment of sewage to
a) help grease separation
b) aid flocculation
c) increase the biochemical oxygen demand
d) cause bulking of activated sludge
43. In the design of grit chambers
a) baffles are essential
b) temperature is an important factor
c) the detention period should be at least 30 minutes
d) the maximum velocity of flow is 30 cm per second
44. Incrustation of the tubewell pipes may results in
a) discharge of highly corrosive acidic water
b) discharge of highly alkaline water
c) reduces discharge from tubewell
d) excessive discharge of sand with water
45. The maximum velocity occurs in an egg shaped sewer when the ratio depth of flow to vertical diameters is
a) 0.33
b) 0.50
c) 0.81
d) 0.95
46. Shrouding is provided in
a) slotted pipe tubewell
b) cavity type tubewell
c) strainer type tubewell
d) none of the above
47. If in a test conducted for determining relative stability, the period of incubation at 200C is t days, the relative stability in % is given by
a) 100[1 – (0.794)t]
b) 100[1 – (0.630)t]
c) 100[1 – (0.694)t]
d) 100[1 – (0.730)t]
48. Ozone layer in the upper atmosphere is getting destroyed owing to its reaction with
a) carbon dioxide
b) hydrogen peroxide
c) oxides of nitrogen
d) chlorofluorocarbons
49. The intensification of green house effect is attributed to the increased level of
a) carbon dioxide
b) carbon monoxide
c) chlorofluorocarbons
d) sulphur dioxides
50. Electrostatic precipitators are used as pollution control device for the separation of
a) SO2
b) NOx
c) hydrocarbon
d) particulate matter
