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Environmental (281-300)

Updated: Apr 27, 2020

281. The effective size (ES) of sand and its uniformity coefficient (UC) are the

usually specified parameters for sand filters. In slow sand filters, as compared to

rapid sand filters ES is less but UC is more


282. If only ammonia was present in water, the only change in Fig.6.4 would have been that the curve would

be passing through the origin


283. Which one of the following is the purpose of providing a surge tank in a pipeline carrying water ?

to protect the pipeline against water hammer


284 Rapid mixing unit - 30 second Flocculator- 30 minute Propeller mixing unit 10 second Sedimentation tank-1.5 hours


285. The maximum flow occurs in an eggshaped sewer when the ratio of depth

of flow to vertical diameter is 0.95


286. The following three stages are known to occur in the biological action involved in the process of sludge digestion :

1. Acid fermentation.

2. Acid regression

3. Alkaline fermentation.


287. Fresh sludge has moisture content of 99% and, after thickening, its mojsture content is reduced to 96%. The reduction in volume of sludge is 75%



Dissolved solids-Reverse osmosis Colloidal solids-Coagulation Volatile solds-Digestion Settleable solids-Sedimentation


289. In the oxidation ditch, the excess sludge is taken to drying beds


290. The flow sheet of the liquid stream of a sewage treatment scheme consists of

1. screen chamber

2. grit chamber

3. primary settling tank

4. trickling filter

5. secondary settling tank


291. Oxidation ditch ... algae


292. The two main gases liberated from an anaerobic sludge digestion tank would

include carbon dioxide and methane


293. Which one of the following sewage treatment units has a parshall flume

grit chamber


294. Which one of the following is least important in the activated sludge process? the sludge volume index of the return sludge to be less than 200


295. The following zones are formed in a

polluted river:

The correct sequence in which these zones occur progressively downstream in a

polluted river is

1. zone of pollution

2. zone of active decomposition

3. zone of recovery

4. zone of clear water



Acid water-Mining SO₂- Volcanoes CO - Automobiles Fly ash-Thermal power station


297. Aerosol is dispersion of small solid or liquid particles in gaseous media


298. Water present in an artesian aquifer is usually above atmospheric pressure


299. Consider the following statements :

The daily per capita consumption of water apparently increases with

1. higher standard of living of people

2. availability of sewerage in the city

3. wholesome and potable quality of water



Incrustation of filter sand media- Washing the filter with sodium hydroxide or bleaching powder of occasionally Air binding & development of negative head-Increasing the depth of water during filter operation by about 15-20 cm as compared to the normal depth maintained during daily operation and more frequent backwashing Mud ball formation - Through back washing with salt solution after soaking the filter in it Slime growth on filter-Compressed air scouring for about 4 minutes at the time of backwashing and manual surface raking

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