# Water Treatment – MCQ || Water Supply

## Water Treatment – MCQ

1. The rate of filtration of a slow sand filter is

a) 200 to 400 lit/m2/hr
b) 100 to 200 lit/m2/hr
c) 200 to 300 lit/m2/hr
d) 100 to 300 lit/m2/hr

b) 100 to 200 lit/m2/hr

2. A city supply of 15 MLD is to be disinfected with chlorine doses of 0.5 ppm. The bleaching powder contains 25 % of chlorine. The requirement of bleaching powder per day is

a) 300 kg
b) 75 kg
c) 30 kg
d) 7.5 kg

c) 30 kg

3. The expression for settling velocity for a sedimentation tank is given by

a) Q/BH
b) Q/BL
c) Q/LH
d) None of these.

b) Q/BL

4. What is the maximum permissible velocity in horizontal flow type sedimentation tank?

a) 1.2 m/sec
b) 0.9 m/ sec
c) 0.6 m/sec
d) 0.3 m/sec

d) 0.3 m/sec

5. What is the normal detection period for a plain sedimentation water tank?

a) 2 to 4 hours
b) 4 to 8 hours
c) 6 to 12 hours
d 8 to 16 hours

b) 4 to 8 hours

6. What is the effective size of sand particles in the case of a slow sand filter?

a) 0.7 mm to 1.3 mm
b) 0. 53 mm to 0.7 mm
c) 0. 4 mm to 0.53 mm
d) 0.2 mm to 0.4 mm

d) 0.2 mm to 0.4 mm

7. Which of the following factors affects the settlement of particles in the sedimentation tank?

a) Viscosity of water
b) Velocity of flow
c) Specific gravity of solid
d) Size and shape of solid
e) All of these

e) All of these

8. Settling velocity is proportional to the square of the diameter of the particle( according to Stoke’s law) when

a) Diameter of particles is between 0.1 and 10 mm
b) Diameter of particles is less than 0.1 mm
c) Diameter of particles is more than 1.0 mm
d) For all diameter

b) Diameter of particles is less than 0.1 mm

9. The maximum permissible concentration of cadmium in potable water as per who guide lines

a) 0.01 mg/l
b) 0.009 mg/l
c) 0.006 mg/l
d) 0.003 mg/l

d) 0.003 mg/l

10. Which of the following condition indicates the 100 % removal of particles from the bottom of a sedimentation tank?

a) Settling velocity < Liquide rising velocity
b) Settling velocity ≤ Liquide rising velocity
c) Settling velocity ≥ Liquide rising velocity
d) None of these

c) Settling velocity ≥ Liquide rising velocity

11. If the liquid rising velocity is greater than the settling velocity, then one would expect

a) 100 % removal of particles
b) 50 % removal of particles
c) 0 % removal of particles
d) None