If the diameter of a sewer is 100 mm, the gradient required for generating self cleansing velocity is__________________?
(A) 1 in 60
(B) 1 in 100
(C) 1 in 120
(D) None of these
To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of_______________?
(A) Hydrochloric acid
(B) Sulphuric acid
(C) Nitric acid
(D) Citric acid
The sewer which transports the sewage to the point of treatment, is called________________?
(A) House sewer
(B) Out-fall sewer
(C) Branch sewer
(D) Main sewer
If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains__________________?
(A) Hydrogen sulphide
(B) Carbon dioxide
(C) Methane
(D) Oxygen
The ratio of minimum hourly flow to the average flow of sewage is_________________?
(A) 1/4
(B) 1/3
(C) 1/2
(D) 3/4
Removal of oil and grease from sewage, is known____________________?
(A) Screening
(B) Skimming
(C) Filtration
(D) None of these
The gradient of sewers depends upon_________________?
(A) Velocity of flow
(B) Diameter of the sewer
(C) Discharge
(D) All the above
The standard B.O.D. of water is taken for_________________?
(A) 1 day
(B) 2 days
(C) 3 days
(D) 5 days
Fresh sewage may become stale in_________________?
(A) One hour
(B) Two to three hours
(C) Three to four hours
(D) Six hours
The sewage discharge in a detritus tank of a treatment plant is 576 litres/sec with flow velocity of 0.2 m/sec. If the ratio of width to depth is 2, the depth is____________________?
(A) 100 cm
(B) 110 cm
(C) 120 cm
(D) 150 cm