Waste Water Engineering

151. Nitrogen cycle of sewage, is

1. Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
2. Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates
3. Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia
4. Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates

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152. No treatment of the sewage is given if dilution factor is

1. Less than 150
2. Between 150 to 200
3. Between 200 to 300
4. More than 500

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153. Oxidation process results in the formation of

1. Carbon dioxide
2. Nitrates
3. Sulphates
4. All the above

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154. Pathogens (or pathogenic bacterias) in water may cause

1. Typhoid
2. Cholera
3. Dysentery
4. All the above

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155. pH value of sludge during alkaline regression stage, is

1. More than 7
2. Less than 7
3. Less than 6
4. More than 6

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156. Pick up the correct statement from the following:

1. The sewer pipes of sizes less than 0.4 m diameter are designed as running full at maximum discharge
2. The sewer pipes of sizes greater than 0.4 m diameter are designed as running 2/3rd or 3/4th full at maximum discharge
3. The minimum design velocity of sewer pipes is taken as 0.8 m/sec
4. All the above

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157. Pick up the incorrect size of stone ware sewers

1. 52.5 cm
2. 67.5 cm
3. 82.5 cm
4. None of these

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158. Pick up the incorrect statement from the following for allowing workers to enter sewers

1. The particular manhole and one manhole on upstream and one manhole on downstream should remain open for 30 minutes
2. Proper tests for the presence of poisonous gases must be carried out
3. The men entering the manhole should be advised to smoke in the sewer
4. Warning signals should be erected

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159. Pick up the incorrect statement from the following:

1. The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion
2. Sludge digestion is carried out in sludge tank
3. The gases produced in sludge digestion process, contain 75% carbon dioxide
4. The gases produced in sludge digestion process, contain 75% methane

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160. Pick up the in-correct statement from the following:

1. Manholes are provided in sewer pipes at suitable intervals
2. Catch basins are generally provided in sewers for carrying drainage discharge
3. Inlets are generally provided in all sewers
4. None of these

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