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VTU Civil Engineering (Semester 7)
Environmental Engineering 2
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Explain briefly the important features of the different 'system of sewerage'. Also, state their merits and demerits.
12 M
1 (b) Differentiate between the following:
i) Sullage and sewage
ii) Raw sewage and septic sewage
iii) Dry weather flow and wet weather flow
iv) Lateral sewer and outfall sewer.
8 M

2 (a) With a neat sketch explain i) The objectives, ii) Location, iii) Details of a manhole. Bring out the functions of a manhole.
10 M
2 (b) Design a circular sewer to serve a Residential suburb of a city with the following data.
i) Area of suburb = 50 hectares
ii) Population = 6000 persons
iii) Average rate of water supply = 20 lpcd
iv) Subtraction allowance = 20%.
v) Critical design rainfall intensity = 40 mm/hr
vi) Average available ground slope 1 in 1000.
vii) Co-efficient of runoff = 0.45.
viii) Manning's N=0.012.
Maximum flow in the sewerage system may be taken as three times the average flow.
10 M

3 (a) Explain the terms BOD and COD and their importance in waste water treatment.
4 M
3 (b) Deduce an expression for determining BOD at any time.
8 M
3 (c) The following observations were made on a 5% dilution of sample of sewage
D.O. of blank = 3.3 mg/l
D.O of diluted sample after 5 days incubation = 0.89 mg/lit.
D.O. of origin sample = 0.55 mg/l
Calculate the ultimate B.O.D of sample. Assume KD = 0.1/day.
8 M

4 (a) Draw a flow diagram from an outfall to the disposal into a river valley after complete treatment for a proposed sanitary project for a town. Indicate the purpose of each unit adopted during the process treatment.
12 M
4 (b) What are the important salient properties of 'Activated sludge process'? Explain the process involved in treating domestic sewage.
8 M

5 (a) Explain briefly the dilution method of disposal of sewage. What are the factors which influence the choice of the method to be adopted?
8 M
5 (b) Discuss in detail the process deoxygenation and reoxygenation with respect to self purification of natural waters with a neat sketch.
12 M

6 (a) What do you understand by the term 'Low cost waste treatment'?
4 M
6 (b) Explain with a neat sketch the principle and process working of an 'Oxidation pond'.
6 M
6 (c) Design an oxidation pond to treat sewage in a tropical country, from a colony of 10,000 persons. The B.O.D. of the sewage is 300 mg/l and flow is 120 lpcd 90% of water supplied is collected as sewage. Check the detention time. Sketch the detail of the oxidation pond.
10 M

7 (a) What is sludge gas? What is its typical composition? What are the uses of sludge gas?
4 M
7 (b) Explain briefly the different stages of sludge digestion process in a 'Digester'. With a neat sketch explain the constructional details of sludge digestion tank.
8 M
7 (c) Design sludge digestion tank for one lakh population. The sludge content per capita per day is 0.07kg. The moisture of sludge is 94%. The specific gravity of wet sludge is 1.02 and 3.5% of fresh sludge is being mixed with digested sludge.
8 M

Write short notes on the following:
8 (a) Sewage farming.
5 M
8 (b) Testing of a sewer time
5 M
8 (c) Sludge bulking and sludge volume index
5 M
8 (d) Oxidation ditch.
5 M

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