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

Question: For a given discharge, the efficiency of sedimentation tank can be increased by______________?

• 1. increasing the depth of tank
• 2. decreasing the depth of tank
• 3. increasing the surface area of tank
• 4. decreasing the surface area of tank

Question: The settling velocity of a particle in a sedimentation tank depends on__________________?

• 1. depth of tank
• 2. surface area of tank
• 3. both depth and surface area of tank
• 4. none of the above

Question: The overflow rate for plain sedimentation tanks is about__________________?

• 1. 500 to 750 litres/hour/ m2
• 2. 1000 to 1250 litres/hour/ m2
• 3. 1250 to 1500 litres/hour/m2
• 4. 1500 to 2000 litres/hour/m2

Question: The settling velocity of a particle in a sedimentation tank increases if_________________?

• 1. particle size is decreased
• 2. the surface area of tank is increased
• 3. the depth of tank is decreased
• 4. none of the above

Question: The velocity of flow of water in a sedimentation tank is about__________________?

• 1. 5 to 10 cm/sec.
• 2. 15 to 30 cm/sec.
• 3. 15 to 30 cm/minute
• 4. 15 to 30 cm/hour

Question: The amount of residual chlorine left in public water supply for safety against pathogenic bacteria is about______________?

• 1. 0.01 to 0.05 ppm
• 2. 0.05 to 0.5 ppm
• 3. 0.5 to 1.0 ppm
• 4. 1.0 to 5.0 ppm

Question: Orthotolidine test is used for determination of________________?

• 1. dissolved oxygen
• 2. residual chlorine
• 3. biochemical oxygen demand
• 4. dose of coagulant