Question: A floating body is said to be in a state of stable equilibrium_________________?

• 1. when its metacentric height is zero
• 2. when the metacentre is above the centre of gravity
• 3. when the metacentre is below the centre of gravity
• 4. only when its centre of gravity is below its centre of buoyancy

Question: A vertical rectangular plane surface is submerged in water such that its top and bottom surfaces are 1.5 m and 6.0 m res-pectively below the free surface. The position of center of pressure below the free surface will be at a distance of________________?

• 1. 3.75 m
• 2. 4.0 m
• 3. 4.2m
• 4. 4.5m

Question: The process in which the chlorination is done beyond the break point is known as_________________?

• 1. prechlorination
• 2. post chlorination
• 3. super chlorination
• 4. break point chlorination

Question: Double filtration is used_______________?

• 1. to increase the filtration slow sand filters capacity of
• 2. to increase the filtration rapid sand filters capacity of
• 3. for isolated buildings like pools, hotels etc swimming
• 4. all of the above

Question: Disinfection of water results in______________?

• 1. removal of turbidity
• 2. removal of hardness
• 3. killing of disease bacteria
• 4. complete sterilisation

Question: Period of cleaning of slow sand filters is about________________?

• 1. 24 – 48 hours
• 2. 10-12 days
• 3. 2-3 months
• 4. 1-2 year

Question: Air binding phenomena in rapid sand filters occur due to_________________?

• 1. excessive negative head
• 2. mud ball formation
• 3. higher turbidity in the effluent
• 4. low temperature

Question: The rate of filtration in slow sand filters in million litres per day per hectare is about_____________?

• 1. 50 to 60
• 2. 100 to 150
• 3. 500 to 600
• 4. 1400 to 1500

Question: The chemical most commonly used to increase speed of sedimentation of sewage is_______________?

• 1. sulphuric acid
• 2. copper sulphate
• 3. lime
• 4. sodium permanganate

Question: The detention period in coagulation tanks is usually kept as_______________?

• 1. 1 to 2 minutes
• 2. 30 to 45 minutes
• 3. 2 to 6 hours
• 4. 2 to 6 days