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Environmental (181-200)

Updated: Apr 26, 2020


A. Groundwater-Carbon dioxide and hardness B. Lake water at the bottom-Low D.O. and colour C. Canal water-Low organic content and high D.O. D. River water in floods-High turbidity and D.O.


182. Figure 6.1 shows roughly, the daily mass curves of supply to and demand from an elevated service reservoir (ESR).

The minimum required capacity of the c reservoir is given by (A+B)


183. If present in water, chlorination of water does not reduce the dissolved oxygen content


184. Dechlorination of water is achieved by adding sodium thiosulphate


185. The efficiency of a sedimentation tank does not depend upon depth of the tank


186. Treatments reduce salinity of water

1. Reverse osmosis.

2. Electrodialysis.



187. A city supply of 15000 cubic metres of water per day is treated with a chlorine

dosage of 0.5 ppm. For this purpose, the requirement of 25% bleaching powder per day would be 30 kg



The distribution system shown in Fig. is called grid iron system


189.The results of analysis of a sample of water are given below:

given above, it can be inferred that the water needs

treatment for the removal of iron and hardness and disinfection



Cast iron pipe-Spigot and socket joint Asbestos cement pipe-Simplex joint Plain ended pipes subjected to frequent vibrations-Victaulic joint G.I. pipe-Screwed joint


191. The water supply to a house begins with the connection of the service pipe with the municipal water mains. The connection comprises:

1. Ferrule.

2. Goose neck.

3. Stopcock.

4. Water meter.


192. When the coefficient of rugosity is increased from 0.01 to 0.02, the gradient

of a pipe of a given diameter to carry the same flow at the same velocity will be

increased by 4 times



A. Concrete sewer-Unsuitable where soil contains excessive sulphates B. Stoneware sewer-Resistant to corrosion from most acids C. Cast iron sewer-Corrosion resistance in most natural soils D. Steel sewer-Cannot withstand high external load


194. Which one of the following statements is true of trickling filter sludge?

It has a comparatively low sludge volume index


195. BOD is preferred to COD as an index of sewage concentration because

BOD relates specifically to putrescible organic matter which is the most objectionable sewage constituent



A. Grit chamber-Two minutes B. Primary sedimentation-Two hours C. Activated sludge-Six hours D. Sludge digestion-Twenty days


197. Under Indian conditions, the average per capita contribution of BOD is

50 to 70 gm/d


198. Sewage sickness relates to clogging of pores in soil due to excessive application of sewage to land, obstructing aeration and leading to septic conditions



Waste pipe-Carries liquid wastes that do not include human excreta Soil pipe-Carries liquid wastes including human excreta Vent pipe-Provides flow of air to orfroma drainage system in order to prevent vacuum pressures and excessive pressure and provides escape for foul gases Antisiphonage pipe-Preserves the water seal of traps through access to atmospheric air



Carbon monoxide-Asphyxiation Carbon dioxide-Greenhouse effect Methane-Explosion Sulphur dioxide-Acid rain

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