| The velocity of flow of water in a sedimentation tank is about |
A) 50 to 100 mm/second
B) 150 to 300 mm/second
C) 150 to 300 mm/minute
D) 150 to 300 mm/hour
| The Dechlorination of the water is generally required when _____ has been practised |
A) Double chlorination
B) Super chlorination
C) Post-chlorination
D) Pre-chlorination
| The range of rate of filtration of pressure filters is |
A) 1000 to 2000 litres per hour per sq. m of filter area
B) 2000 to 4000 litres per hour per sq. m of filter area
C) 4000 to 5000 litres per hour per sq. m of filter area
D) 6000 to 15000 litres per hour per sq. m of filter area
| Excessive aeration during the water treatment |
A) improves the quality of water
B) makes the water salty
C) leads to corrosion of metal
D) increases the alkalinity
| What is predominant coagulating mechanism for raw water having high turbidity and high alkalinity |
A) Ionic layer compression
B) adsorption and charge neutralization
C) sweep coagulation
D) Inter particle bridging
| If a water treatment plant has to treat 100 million litres of water per day, then the number of Rapid Gravity Filters required would be approximately |
A) 3
B) 13
C) 23
D) 33
| Pick out the incorrect statement for a rapid sand filter: (i) the period of cleaning is usually 2 to 3 weeks (ii) the effective size of the sand particles is 0.35 to 0.6 mm (iii) the maximum permitted loss of head is 3m |
A) Only (i)
B) (i) and (ii)
C) (ii) and (iii)
D) (i), (ii) and (iii)
| Which of the following statement(s) is / are true for a Slow Sand Filter? i. Water entering the slow sand filter should not have been treated by coagulants ii. Coarsest gravel is used in the bottom most layer and the finest gravel is used in the topmost layer iii. Coarser the sand, purer will be obtained water as more impurities and bacterial will be removed |
A) Only (i)
B) (i) and (ii)
C) (ii) and (iii)
D) (i), (ii) and (iii)
| The skimming tanks are designed for a detention period of about |
A) 3-5 minutes
B) 10-20 minutes
C) 30 minutes
D) 60 minutes
| Which of the following statements are true for alum and iron salts being used as coagulants i. Iron salts are used as coagulants more frequently for treating sewage while alum is used more frequently for treating raw water ii. Alum salts produce heavy floc and can therefore remove much more suspended matter than iron salts |
A) Only (i)
B) Only (ii)
C) Both (i) and (ii)
D) Neither (i) nor (ii)
