A rain sanitary sewer is constructed to carry
1.sanitary sewage
2.storm sewage
3. surface water
4.ground water
Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to
1. initial demand
2. first stage demand
3.carbonaceous demand
4.all of these.
For treating the sewage of a large city, you will recommend
1.a sedimentation tank and an activated sludge treatment plant
2.a plant consisting of Imhoff tanks with low rate trickling filters
3.sedimentation tanks with high rate trickling filters
4.None of these.
If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is
1.1 in 60
2.1 in 100
3.1 in 120
4.None of these.
The gas which may cause explosion in sewers, is
1.carbondioxide
2.methane
3.ammonia
4.carbon monoxide.
The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is
1.1.5
2.2
3.3
4.4
A sewer pipe contains 1 mm sand particles of specific gravity 2.65 and 5 mm organic particles of specific gravity 1.2, the minimum velocity required for removing the sewerage, is
1.0.30 m/sec
2.0.35 m/sec
3.0.40 m/sec
4. 0.45 m/sec
If the over land flow from the critical point to the drain is 8 km and the difference in level is 12.4 m, the inlet time is
1.2 hours
2.3 hours
3.4 hours
4.5 hours
In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is
1.2.25
2.2.5
3.2.55
4.2.65
In R.C. sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept
1.10
2.5
3.2
4.0.25
Pick up the correct statement from the following :
1.pH value indicates acidity and alkalinity of sewage
2. In acidic sewage, the pH value is less than 7
3.In alkaline sewage, the pH value is more than 7
4.All the above.
Pick up the in-correct statement from the following :
1.Manholes are provided in sewer pipes at suitable intervals
2.Catch basins are generally provided in sewers for carrying drainage discharge
3.Inlets are generally provided in all sewers
4.None of these.
Removal of oil and grease from sewage, is known
1.screening
2.skimming
3.filtration
4.None of these.
A rainfall may be classified as acidic if its pH value is less or equal to
1.6
2.7
3.5
4.6.5
Aerobic bacterias
1. flourish in the presence of free oxygen
2.consume organic matter as their food
3.oxidise organic matter in sewage
4.All the above.
An inverted siphon is designed generally for
1.one pipe
2.two pipes
3.three pipes
4.four pipes.
Assertion (A) : Discharging the effluents from the oxidation ponds just up stream of lakes or reservoirs is undesirable. Reason (R) : The discharged algae get settled in the reservoirs and cause anaerobic decomposition and other water qualities.
1.Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not a correct explanation of A
3.A is true but R is false
4.A is false but R is true.
Chlorination of water is done for the removal of
1.bacterias
2.suspended solids
3.sediments
4.hardness.
Clogging of sewers, is caused due to
1.silting
2.low discharge
3.greasy and oily matters
4.all the above
Dilution method of disposing off sewage, is not preferred to
1. when sewage is fresh
2.when diluting water has high dissolved oxygen content
3.when diluting water is used for water supply near the point of sewage disposed
4.when the diluting water is having flow currents
Disposal to sewage in large cities, is done in
1.irrigation
2.dilution
3.oxidation
4.putrifaction.
f 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
1.200 ppm
2.225 ppm
3.250 ppm
4.None of these.
Flocculated particles do not change their
1.size
2.shape
3.weight
4.None of these.
For evaporation and measurement of settlable solids, the apparatus used, is
1.a jar
2.a breaker
3.a test tube
4.an Imhoff cone.
For house drainage minimum gradient is
1.1 in 60
2.1 in 80
3.1 in10
4.1 in 400
For non-scouring velocity 5 m/sec, the type of sewers generally preferred to, is
1.cast iron sewers
2.cement concrete sewers
3.glazed bricks sewers
4.stone ware sewers.
For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed
1. 3 PPm
2.4 PPm
3.5 PPm
4.10 PPm
House connections to the laterals is generally made by
1.R.C.C.
2.P.C.C.
3.Cast iron
4.Glazed stonewares.
If D is the diameter of upper circular portion, the overall depth of a standard egg shaped section, is
1.D
2.1.25 D
3.1.5 D
4.1.75 D
If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is
1.1045 mm
2.1065 mm
3.1075 mm
4.1095 mm.
In a fully mechanised composting plant, involves
1.mechanized receipt
2.mechanized segregation
3.mechanized pulverising of refuse
4.all of these.
In olden days the type of section adopted in trunk and out fall sewers was
1. parabolic shaped
2.horse shoe shaped
3.egg shaped
4.circular shaped.
In SI units the power of sound is represented in
1.kgs
2.joules
3.neutons
4.watts.
Pick up the correct statement from the following :
1. In treated sewage, 4 PPm of D.O. is essential
2. Only very fresh sewage contains some dissolved oxygen
3.The solubility of oxygen in sewage is 95% that is in distilled water
4.All the above.
Self-cleansing velocity is
1.velocity at dry weather flow
2.velocity of water at flushing
3.velocity at which no accumulation remains in the drains
4.velocity of water in a pressure filter.
The asbestos cement pipes are generally laid
1.horizontally
2.vertically
3.at an angle of 30°
4.at an angle of 60°.
The coagulant widely used for sewage treatment, is
1.alum
2.ferric chloride
3.ferric sulphate
4. chlorinated copperas.
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
1.204 cu m
2.208 cu m
3.212 cu m
4.216 cu m
The minimum recommended diameter of sewers, is
1.20 cm
2.5 cm
3.10 cm
4.15 cm
The non-clog pump which permits solid matter to pass out with the liquid sewage, is
1.centrifugal pump
2.reciprocating pump
3.pneumatic ejector
4.none of these.
The rate of accumulation of sludge in septic tanks is recommended as
1.30 litres/person/year
2. 25 litres/person/year
3.. 30 litres/person/month
4.25 litres/person/month.
The screens are fixed
1. perpendicular to the direction of flow
2. parallel to the direction of flow
3.at an angle 30° to 60° to the direction of flow
4.None of these.
The sewage is pumped up
1.from low lying areas
2.from flat areas
3.from basements
4.all the above.
The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is
1. 0.68 m
2.0.88 m
3.1.36 m
4. 1.76 m.