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Environmental (261-280)

Updated: Apr 27, 2020


1. Setting sight rails over the trench.

2. Driving pegs to the level of the invert line of the sewer.

3. Transferring the centre line of the sewer to the bottom of the trench.

4. Placing the sewer in the trench


262. A grit chamber of dimensions 12.0 m x 1.50 m x 0.80 m liquid depth has a flow of 720 m³ /hr. Its surface loading rate and detention time are, respectively

40000 lph/m² and 1.2 minutes



Large floating matter- Screens Suspended inorganic matter- Grit chamber Suspended organic matter- Primary clarifier Dissolve organic matter- Trickling filter


264. Which of the following are claimed as advantageous in respect of aerobic sludge digestion as compared to anaerobic sludge digestion ?

1. lower BOD concentration in supernatant liquor

2. production of a sludge with excellent denaturing propensity

3. lesser capital cos


265. The following data pertain to a sewage


Initial D.O. = 10mg/l

Final D.O. = 2 mg/1

Dilution to 1%

The BOD of the given sewage sample is 800 mg/l



Sludge disposal - Lagging sludge digestion - Seeding Aerobic action - Contact bed Recirculation - Biofilters


267. Sewage sickness occurs when- voids of soil get clogged due to

continuous application of sewage on a piece of land


268. In the design of storm sewers, "time of concentration" is relevant to determine the rainfall intensity


269. Self-purification of running streams may be due to dilution, sedimentation and oxidation


270. Which of the following waste disposal tasks are achieved by a septic tank with its dispersion trench ?

1. settling and anaerobic sludge digestion.

2. bio-oxidation of effluent


271. Which of the following air pollutants is/are responsible for photochemical


1. oxides of nitrogen

2. unburnt hydrocarbons



A.Electrostatic precipitators - Fine dust B. Cyclones - Coarse particles C. Wet scrubbers-Gas D. Adsorbers-Sulphur dioxide



1. Eutrophication..... Nutrient accumulation leading to ecosystem change occurring in impounded water


274. The typical density in kg/cum (in situ) of well - compacted municipal solid waste in landfill is in the range of 310 to 500


275. Materials are used as landfill sealants for the control of gas and leachate movements?

1. Bentonite

2. Butyl rubber


276. Two sources generate noise levels of 90dB and 94 dB respectively. The cumulative effect of these two noise levels on the human ear is 95.5 dB


277. Two identical centrifugal pumps are operated in parallel so as to deliver into a

common delivery pipe. Speed for both is also identical. At what total discharge (Q)

and total head (H) will the system operate as compared to discharge and head to each of the pumps operated singly?

Total Q would be approximately doubled, but H would remain the same


278. Storage of water by impounding is required where there is a large variation in quantity of the river flow from time to time


279. In a water treatment plant, dissolved iron and manganese can be removed from the water by aeration and coagulation


280. The various treatment processes in a water treatment plant are listed below :

1. coagulation

2. flocculation

3. sedimentation

4. filtration

5. chlorination

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