Environmental Engineering

201.The maximum CO₂ is emitted into the atmosphere by

1. Combustion
2. Urea
3. Biomass burning
4. Trees

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202.The maximum permissible noise level to which a man working in a chemical plant can be exposed for eight hours per day is about _________ decibels.

1. 60
2. 90
3. 105
4. 120

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203.The most commonly used chemical coagulant in water treatment is

1. Ferrous sulphate
2. Alum
3. Lime
4. Hydrazine

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204.The pH value of oxidised sewage is about

1. 1.8
2. 6.2
3. 7.3
4. 13.4

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205.The pH value of potable water should be between

1. 1 to 1.5
2. 6.5 to 8
3. 13 to 14
4. 4 to 5

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206.The principal gas evolved from sludge digestion tank is

1. CO
2. CO₂
3. CH₄
4. N₂

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207.The progressive warming up of the earth's surface is mainly due to the

1. Automobile exhaust
2. Blanketing effect of CO₂ in the atmosphere
3. De-forestation
4. Thickening of ozone layer

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208.The ratio of oxygen available to the oxygen required for stabilisation of sewage is called the

1. Bacterial stability factor
2. Relative stability
3. Biological oxygen demand (BOD)
4. Oxygen ion concentration

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209.The resistance of water to the passage of light through it is a measure of the

1. Turbidity
2. Color
3. Hardness
4. Dissolved gases

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210.The term Biological Oxygen Demand (BOD) is used in relation to

1. Potable water
2. Cooling water
3. Distilled water
4. Industrial effluents

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