The sewage treatment in septic tanks is due to__________________?

Related Mcqs:

1. Assertion A.: A free board of 0.3 m is provided above the top sewage line in septic tanks. Reason (R): It helps to accommodate the scum in the septic tank_________________?

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

2. The bottom of the sewage inlet chamber of septic tanks, is provided an outward slope_________________?

   A. 1 in 5
   B. 1 in 10
   C. 1 in 15
   D. 1 in 20

3. The rate of accumulation of sludge in septic tanks is recommended as____________________?

   A. 30 litres/person/year
   B. 25 litres/person/year
   C. 30 litres/person/month
   D. 25 litres/person/month

4. The digested sludge from septic tanks, is removed after a maximum period of__________________?

   A. 3 years
   B. 3.5 years
   C. 4 years
   D. 5 years

5. In septic tanks, decomposition of organic bacteria, is done by_____________________?

   A. Anaerobic bacteria
   B. Aerobic bacteria
   C. Both types of bacterias
   D. None of these

6. Which one of the following statements regarding septic tanks is wrong ?

   A. A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided
   B. The outlet invert level is kept 5 to 7.5 cm below the inlet invert level
   C. The minimum width of septic level is 90 cm
   D. The depth of tank is kept equal to its width

7. The dimensions of a rectangular settling tank are: length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is_____________________?

   A. 204 cu.m
   B. 208 cu.m
   C. 212 cu.m
   D. 216 cu.m

8. The density of population over 40 hectares is 250/hectare. If water supply demand per day is 200 litres and sewage discharge is 80% of water supply, the sewage flow in sewers of separate system, is_____________________?

   A. 0.05552 cumec
   B. 0.05554 cumec
   C. 0.05556 cumec
   D. 0.0556 cumec

9. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is_________________?

   A. 50 mg/l
   B. 100 mg/l
   C. 150 mg/l
   D. 250 mg/l

10. If q is the average sewage flow from a city of population P, the maximum sewage flow______________?

    A. Q = [(4 + )/(18 + )] q
    B. Q = [(18 + P)/(4 + )] q
    C. Q = [(18 + )/(4 + )] q
    D. Q = [(5 + )/((15 + )] q