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Environmental (221-240)

Updated: Apr 26, 2020

221. If the total hardness and alkalinity of a sample of water are 300 mg/1 and 100

mg/1 (CaC0₃ scale) respectively, then its carbonate and non-carbonate hardness (in units of mg/1) will be respectively 100 and 200


222. Electrical conductivity (EC) of water and total dissolved solids (TDS) are

interrelated. The value of EC will increase with increase in TDS


223. When two identical centrifugal pumps are operating in series on a common rising main, then the pressure in the rising main wjll be nearly doubled, while the discharge will remain the same


224. In transition of sewers from smaller diameter sewers to larger diameter sewers, the continuity of sewers is maintained at the crowns of the sewers


225. The slope of a 1.0 m diameter concrete sewer laid at a slope of 1 in 1000,

develops a velocity of 1 m/s, when flowing full. When it is flowing half-full,

the velocity of flow through the sewer will be 1.0 m/s



Oxidation ditch-Aerobic bacteria (suspended culture) Waste stabisation pond-Facultative bacteria Inhoff tank-Anaerobic bacteria Rotating Biological Contractor (RBC)-Aerobic bacteria (attached culture)


227. One litre of sewage, when allowed to settle for 30 minutes gives a sludge

volume of 27 cm³. If the dry weight of this sludge is 3.0 grams, then its sludge

volume index will be 9


228. An industrial wastewater enters a stream having a BOD concentration of 10 mg/1 and a flow of 20 m³/s. If the flow of wastewater is 1.5 m³/s and its BOD

concentration is 250 mg/1, then the BOD concentration in the stream at a point downstream of the point of confluence of wastewater with the stream will be

26.74 mg/l


229 A polluted stream undergoes self purification in four distinct zones

1. Zone of degradation

2. Zone of active decomposition

3. Zone of recovery

4. Zone of clear water.



Soil pipe-Water closet waste Intercepting trap-House drainage p-trap-Wash basin Cowl-Ventilating Pipe



CO-Ozone liberation at ground level CO₂-Greenhouse effect SO₂-Acid rains NOₓ-Acute toxicity


232. The atmosphere extends upto a height of 10,000 km. It is divided into the following four thermal layers

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere


233. Which one of the following solid waste disposal methods is ecologically most

acceptable ?Compositing


234. The construction of impounding reservoir is required when the rate of flow in the stream, in dry season is less than the demand


235.treatments reduce salinity of water?

1. Electrodialysis

2. Reverse osmosis

3. Freezing


236. The cleaning of slow sand filter is done by. scraping off top layers of sand and

admitting water


237. What is the correct sequence of formation of the following compounds during chlorination of water in which ammonia is present?

1. NHCl

2. NHCl

3. NCl₃





Sluice valve ... To control flow of water through pipe lines

Air valve ... To release the accumulated air

Scour valve ... To remove silt in a pipe line


240. Which one of the following would contain water with the maximum amount of turbidity ? rivers

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