Environmental Engineering in CE
Noise produced by cooling fans (employed in air cooled heat exchangers or cooling tower) is mainly caused due to the turbulence created by blade passage through air. It can be reduced by use of a slower fan

With greater number of blades
Neither A nor B
Both A & B
Of increased diameter

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Environmental Engineering in CE
Coal mines drainage waste water (acidic in nature) results from the earth's water percolating through the voids created in coal bed during mining. This polluted water which either drains out naturally to water courses or are removed before starting the mining is

Left as such without any treatment
None of these
Neutralised by alkali treatment
Diluted with fresh water to reduce its acidity

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