In a sedimentation tank, the detention period for water ranges from _____________ hours?

Related Mcqs:

1. In sewage treatment, the detention period allowed for oxidation ponds ranges from _____________ weeks?

   A. 1 to 2
   B. 4 to 5
   C. 9 to 10
   D. 15 to 20

2. A solid metallic block weighing 5 kg has an initial temperature of 500°C. 40 kg of water initially at 25°C is contained in a perfectly insulated tank. The metallic block is brought into contact with water. Both of them come to equilibrium. Specific heat of block material is 0.4 kJ.kg-1. K-1. Ignoring the effect of expansion and contraction and also the heat capacity to tank, the total entropy change in kJ.kg-1, K-1 is_________________?

   A. -1.87
   B. 0
   C. 1.26
   D. 3.91

3. Water filtration rate in a slow sand filter ranges from ____________ litres/m2/hr?

   A. 10 to 20
   B. 100 to 200
   C. 1500 to 2500
   D. 4000 to 5000

4. Water filtration rate in a rapid sand filter ranges from ______________ kilolitres/m2/hr?

   A. 0.1 to 1
   B. 3 to 6
   C. 10 to 15
   D. 15 to 20

5. In sewage treatment, its sedimentation is speeded up by commonly adding__________________?

   A. Hydrochloric acid
   B. Lime
   C. Copper sulphate
   D. Sodium sulphate

6. A long cylinder and a sphere both of 5 cms diameter are made from the same porous material. The flat ends of cylinder are sealed. Both the cylinder and sphere are saturated with the same solution of sodium chloride. Later both the objects are immersed for a short and equal interval of time in a large tank of water which is well agitated. The fraction of salt remaining in the cylinder and the sphere are Xc and Xs respectively. Which of the following statement is correct ?

   A. Xc > Xs
   B. Xc = Xs
   C. Xc < Xs
   D. Xc greater/less than Xs depending on the length of the cylinder

7. The destruction of water-borne pathogens is termed as disinfection of water. Which of the following is a water disinfectant ?

   A. Chlorine
   B. Alkalis
   C. Benzene hexachloride
   D. Alkyl benzene sulphonate (ABS)

8. The function of skimming tank in sewage treatment is to remove _____________ substances?

   A. Dissolved solid
   B. Suspended solid
   C. Oil & fatty
   D. Gritty & inorganic

9. 1 kg of calcium carbide (CaC2) produces about 0.41 kg of acetylene gas on treatment with water. How many hours of service can be derived from 1 kg of calcium carbide in an acetylene lamp burning 35 litres of gas at NTP per hour ?

   A. 5
   B. 10
   C. 15
   D. 20

10. Thermal pollution of water increases its toxicity and oxidation of oxygen demanding waste besides favouring bacterial growth. A rise in water temperature by 10°C, doubles the toxic effects of _____________ present in it?

    A. Coal ash
    B. Potassium cyanide
    C. Ortho-xylene
    D. None of these