## Waste Water Engineering MCQ Practice Questions (Civil Eng) Set 6

Options are :

• 5 cm
• 15 cm
• 20 cm
• 10 cm

##### If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is:

Options are :

• 1065 mm
• 1075 mm
• 1045 mm
• 1095 mm

Options are :

• Cross-sectional area/wetted perimeter
• Mean of radii in a pipe line of varying cross-sections
• Difference in heads between two points in circular pipes

##### Pick up the correct statement from the following:

Options are :

• The larger the sewer in size, no deposition will take place
• The larger the sewer in size, more will be velocity
• The smaller the sewer in size, less will be velocity
• The larger the sewer in size, deposition will take place

Answer :The larger the sewer in size, deposition will take place

##### The gradient of sewers depends upon:

Options are :

• Diameter of the sewer
• Discharge
• Velocity of flow
• All the above

##### In sewage having fully oxidised organic matter, the nitrogen exists in the form of:

Options are :

• Aluminoid nitrogen
• Free ammonia
• Nitrates
• Nitrites
• None of these

Options are :

• 2.25
• 2.50
• 2.75
• 2.55
• 2.65

##### For non-scouring velocity 5 m/sec, the type of sewers generally preferred to, is:

Options are :

• Cement concrete sewers
• Glazed bricks sewers
• Cast iron sewers
• Stone ware sewers

##### A sewer running partially full and hurried with back filled, fails in compression due to:

Options are :

• Weight of the pipe
• All the above
• Weight of the back fill

Options are :

• 2.0
• 10.0
• 5.0
• 0.25

Options are :

• Mirror test
• Ball test
• All of these
• Water test

Options are :

• 5
• 10
• 20
• 15

##### In sewers the gas generally found, is:

Options are :

• Hydrogen sulphide (H2S)
• Carbon dioxide (CO2)
• Petrol vapours
• All the above
• Methane (CH4)

Options are :

• 0.60 m/sec
• 0.70 m/sec
• 1.0 m/sec
• 0.50 m/sec
• 0.75 m/sec

Options are :

• 3 minutes
• 2 minutes
• 1 minute
• 5 minutes

##### In olden days the type of section adopted in trunk and out fall sewers was:

Options are :

• Horse shoe shaped
• Egg shaped
• Parabolic shaped
• Circular shaped

##### In a fully mechanised composting plant, involves:

Options are :

• Mechanized segregation
• Mechanized pulverising of refuse
• Mechanized receipt
• All of these

##### The gas which may cause explosion in sewers, is:

Options are :

• Ammonia
• Carbon monoxide
• Methane
• Carbondioxide

##### The settling velocity of the particles larger than 0.06 mm in a settling tank of depth 2.4 is 0.33 m per sec. The detention period recommended for the tank, is:

Options are :

• 30 minutes
• 1 hour and 30 minutes
• 1 hour
• 3 hours
• 2 hours

##### For providing an type W.C., the R.C.C. slabs in the toilet portion:

Options are :

• Should be kept 20 cm above the adjacent portion
• Should be sunk by 20 cm
• Need not be sunk
• Should be sunk by 50 cm

Answer :Should be sunk by 50 cm

Options are :

• 6
• 7
• 5
• 6.5

Options are :

• C
• E
• B
• D
• A

##### In septic tanks:

Options are :

• Free board of 0.3 m may be provided
• The baffles or tees are extended up to top level of scum
• The inlet is kept 30 cm below the sewage line and outlet is kept at a level 40% depth of the sewage
• All the above
• The clear space between the baffle top and covering slab is about 7.5 cm

##### The non-clog pump which permits solid matter to pass out with the liquid sewage, is:

Options are :

• None of these
• Reciprocating pump
• Pneumatic ejector
• Centrifugal pump

##### When drainage to sewage ratio is 20, the peak dry weather flow is:

Options are :

• Slightly more than 5% of the design discharge
• Slightly less than 5% of the design discharge
• None of these
• 20% of the design discharge

Answer :Slightly less than 5% of the design discharge

##### Clogging of sewers, is caused due to:

Options are :

• Domestic wastes thrown in manholes
• All the above
• Greasy and oily matters
• Low discharge
• Silting

##### If 2% solution of a sewage sample is incubated for 5 days at 20°C and depletion of oxygen was found to be 5 ppm, B.O.D. of the sewage is:

Options are :

• 250 ppm
• 225 ppm
• 200 ppm
• None of these

##### The rate of accumulation of sludge in septic tanks is recommended as:

Options are :

• 25 litres/person/year
• 30 litres/person/year
• 25 litres/person/month
• 30 litres/person/month

##### The effluent of a septic tank is:

Options are :

• Foul and contains dissolved and suspended solids
• As good as that from a complete treatment
• None of these
• Fit for discharge into any open drain

Answer :Fit for discharge into any open drain

Options are :

• Four pipes
• Two pipes
• One pipe
• Three pipes