Air binding phenomena in rapid sand filters occur due to_________________?

Related Mcqs:

1. Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters. Reason R : The sand used in slow sand filters is finer than that in rapid sand filters. Select your answer based on the coding system given below?

   A. Both A and R are true and R is the correct explanation of A
   B. Both A and R are true but R is not the correct explanation of A
   C. A is true but R is false
   D. A is false but R is true

2. As compared to rapid sand filters, slow sand filters give______________?

   1) slower filtration rate
   2) higher filtration rate
   3) lesser efficiency in removal of bacteria
   4) higher efficiency in removal of bacteria
   The correct answer is?

   A. (1) and (2)
   B. (2) and (3)
   C. (1) and (4)
   D. (2) and (4)

3. The percentage of filtered water, which is used for backwashing in rapid sand filters, is about______________?

   A. 0.2 to 0.4
   B. 0.4 to 1.0
   C. 2 to 4
   D. 5 to 7

4. The effective size of sand particles used in slow sand filters is_______________?

   A. 0.25 to 0.35 mm
   B. 0.35 to 0.60 mm
   C. 0.60 to 1.00 mm
   D. 1.00 to 1.80 mm

5. In water treatment, rapid gravity filters are adopted to remove_______________?

   A. dissolved organic substances
   B. dissolved solids and dissolved gases
   C. floating solids and dissolved inorganic solids
   D. bacteria and colloidal solids

6. Period of cleaning of slow sand filters is about________________?

   A. 24 – 48 hours
   B. 10-12 days
   C. 2-3 months
   D. 1-2 year

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

   A. 50 to 60
   B. 100 to 150
   C. 500 to 600
   D. 1400 to 1500

8. The rate of Alteration of pressure filters is_________________?

   A. less than that of slow sand filters
   B. in between the filtration rate of slow sand filters and rapid sand filters
   C. greater than that of rapid sand filters
   D. equal to that of slow sand filters

9. The depression of water table in a well due to pumping will be maximum_______________?

   A. at a distance R from the well
   B. close to the well
   C. at a distance R/2 from the well
   D. none of the above
   where R is the radius of influence

10. In a BOD test, 1.0 ml of raw sewage was diluted to 100 ml and the dissolved oxygen concentration of diluted sample at the beginning was 6 ppm and it was 4 ppm at the end of 5 day incubation at 20°C. The BOD of raw sewage will be___________?

    A. 100 ppm
    B. 200 ppm
    C. 300 ppm
    D. 400 ppm