MORE IN Environmental Engineering 2
VTU Civil Engineering (Semester 7)
Environmental Engineering 2
June 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 the need for good sanitation. Hence, describe types of sewerage system and their suitability.
6 M
1 (b) Explain factors affecting DWF and teh effects of flow variations on the design of sewerage system.
7 M
1 (c) A certain district of a city has a projected population of 50000 residing over a area of 40Ha. Find the design of discharge for the sewer line, for the following data:
i) Rate of water supply = 200 lped ii) Average impermeability factor for the area = 0.3 iii) Time of concentration = 50 minutes. The sewer line is to be designed for a flow equivalent to the WWF plus twice the DWF. Take sewage generated as equal to 75% of water supplied. Use the formula: $R_i = \dfrac {25.4a} {t+b} .$ Comment on the result.
7 M

2 (a) Explain the effect of flow variation on velocity of flow in sewers.
6 M
2 (b) Explain i) Self cleansing velocity ii) Non-scouring velocity.
5 M
2 (c) A 600mm diameter sewer is required to flow at 0.4 depth on a grade ensuring a degree of self cleansing equivalent to that obtained at full depth at a velocity of 850mm/s. Find the required grade, associated velocities and rates of discharge at full depth and 0.4 depth. Take n=0.015 for all depth of flow $\left \{ Given : \ \dfrac {a} {A} = 0.374 : \ \ \dfrac {r} {R} = 0.857 \right \} .$
9 M

3 (a) Explain the need for providing sewer appurtenances in sewerage system. Hence name common sewer appurtenances.
4 M
3 (b) What are inlets? Draw the locations and section of inlet and explain.
6 M
3 (c) What is Manholes? Explain the need of manhole. Draw neat sketch of deep manhole.
10 M

4 (a) Differentiate between fresh sewage, scale sewage and septic sewage.
3 M
4 (b) What is first stage BOD? Derive the equation for 1st stage BOD, with a neat sketch.
5 M
4 (c) Explain COD and its relation with BOD.
4 M
4 (d) What is Treatability Index? What is the use of treatability index?
8 M

5 (a) Explain various factors that affect self purification process of stream.
7 M
5 (b) Explain waste water disposal into sea.
5 M
5 (c) 100m3/s of a city sewage is discharged in a river is fully saturated with oxygen and flows at a minimum rate of 1250 m3/s, with a minimum velocity of 0.15 m/s. If the 5-day BOD of the sewage is 260 mg/lt, find where the critical DO will occur in the river. Take KD=0.11 d-, f=4.0. Also ultimate BOD is 125% of 5-d BOD of the mixture of sewage and river water. DO saturated for river water = 9.17 mg/lt.
8 M

6 (a) Explain the importance of providing rocks and screens in a waste - water treatment plant. Draw a neat sketch of a bar - screen and explain the loss of head through the screen.
10 M
6 (b) Write a note on grit-chambers.
5 M
6 (c) What are skimming tanks? Explain with a neat sketch.
5 M

7 (a) Explain the biological treatment techniques for treating waste-water.
6 M
7 (b) What are HRTF's? Explain importance of recirculation and its effect on the efficiency of HRTF's.
6 M
7 (c) The MLSS concentration in an aeration tank is 2000mg/lt and the sludge volume after 30 minutes of settling in a 1000ml cylinder is 176ml. Calculate:
i) SVI ii) SDI iii) Required return sludge ratio and iv) SS concentration in the recirculated sludge.
8 M

8 (a) What are stabilization ponds? Explain the algae - bacteria symbiosis in an oxidation pond with a neat sketch.
6 M
8 (b) Explain the stages i anaerobic sludge digestion.
6 M
8 (c) Draw a neat sketch of septic tank with soak pit. Write the design criteria required for septic tank.
8 M

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