Q. The type of bacteria which is active in trickling filter during biological treatment of sewage is the __________ bacteria.

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Q. Presence of dissolved impurities of __________ is responsible for the red brownish color of water.

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Q. TLV of aldrin in public water supply system is about __________ μg/litre.

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Q. A gas is termed as non-toxic, if its maximum permissible concentration (TLV) ranges from __________ ppm.

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Q. Removal of __________ is accomplished by aeration of water.

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Q. High noise level in a chemical plant can be controlled by the

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Q. Limestone powder is injected during pulverised coal burning in boilers to __________ the flue gases.

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Q. Main pollutants released from petroleum refineries is

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Q. Maximum permissible limit of industrial noise as recommended by World Health Organisation (WHO) is __________ decibels.

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Q. Which of the following is a green house gas other than CO₂ ?

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Q. Pick out the correct statement.

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Q. BOD of raw municipal sewage may be in the range of about __________ mg/litre.

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Q. Irradiation of water by ultraviolet light of suitable wavelength is commonly used for disinfection of water in

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Q. When the concentration of SO₂ in air is greater than __________ ppm, it gives a pungent smell.

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Q. Presence of a certain minimum quantity of flourine is desirable in potable water to prevent

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Q. Death may occur, when SO₂ concentration in atmospheric air exceeds __________ ppm.

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Q. Which of the following acts as a natural source of air pollution ?

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Q. Higher concentration of CO₂ in atmosphere

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Q. Permissible safe limit (TLV) of __________ toxic gas is 100-1000 parts per million (ppm).

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Q. Radioactive substances present in the polluted water stream can be removed by

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