Environmental (21-40)

21.The maximum permissible limit for flouride in drinking water is 1.5 mg/litre

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22.Standard EDTA (ethylene diamine terra acetic acid) solution is used to determine the hardness in water

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23. If the coliform bacteria is present in a sample of water, then the coliform test to

be conducted is presumptive coliform test,confirmed coliform test,completed coliform test

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24.Alkalinity in water is expressed as milligrams per litre in terms of equivalent

calcium carbonate

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25.The product of H+ ions and OH- ions in a stronger alkali is

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26.Which of the following values of pH represents a stronger acid? 2

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27.Turbidity is measured on standard silica scale

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28.On standard silica scale, the turbidity in drinking water should be limited to 10 ppm

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29.Residual chlorine in water is determined by starch iodide method,orthotolidine method

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30.Orthotolidine test is used for determination of residual chlorine

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31.If the total hardness of water is greater than its total alkalinity, the carbonate

hardness will be equal to total alkalinity

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32.The amount of residual chlorine left in public water supply for safety against

pathogenic bacteria is about 0.05 to 0.5 ppm

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33.The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of 10 mg/litre

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34.The velocity of flow of water in a sedimentation tank is about 15 to 30 cm/minute

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35.The length of rectangular sedimentation tank should not be more than 4B

where B is the width of the tank

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36.The overflow rate for plain sedimentation tanks is about 500 to 750 litres/hour/m2

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37.Percentage of bacterial load that can be removed from water by the process of

plain sedimentation is about 75

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38.The settling velocity of a particle in a sedimentation tank depends on surface area of tank

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39.The settling velocity of a particle in a sedimentation tank increases if none of the above

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40.For a given discharge, the efficiency of sedimentation tank can be increased by

increasing the surface area of tank