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EJ – 685

*EJ685*

VI Semester B.E. (Civil) Degree Examination, January 2013 (Y2K6 Scheme) CE604 : ENVIRONMENTAL ENGG. – II Time : 3 Hours

Max. Marks : 100

Instructions : 1) Answer any five full questions, selecting atleast two from each Part. 2) Assume suitable data wherever necessary and indicating the same. PART – A 1. a) Distinguish between combined system of sewerage and separate system of sewerage. What are their merits and demerits ? 10 b) Differentiate between the following i) Sullage and sewage ii) Sewer and sewerage iii) Nomogram and partial flow diagram iv) Infiltration and exfiltration v) Manhole and drop manhole.

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2. a) Discuss the factors that affect the D.W.F.

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b) Define “Time of concentration”. Explain its significance in the estimation of storm runoff.

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c) A certain district has 20% drainage area with runoff ratio as 0.9, 25% of drainage area with runoff ratio as 0.85, 50% drainage area having runoff ratio, as 0.10 and 5% area having runoff ratio as 0.05. Determine the impermeability factor. If the total area of district is 4.62 hectares and the maximum rainfall intensity is 62.5 mm/hr, calculate the total quantity of storm water discharge.

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3. a) Explain the construction, and working of a manhole with a neat sketch. b) Explain briefly the common sewer materials used.

10 10 P.T.O.

*EJ685*

EJ – 685

4. a) Explain the phenomenon of “self purification of streams”. Explain the mechanisms involved in it.

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b) Explain the sanitary significance of B.O.D.

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c) The 5 day 20°C B.O.D. of a sample of sewage is 100 mg/l. Calculate its B.O.D at 37°C, after 2 days.

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PART – B 5. a) With the help of a flow diagram, explain the functions of different units of a wastewater treatment, for a large city. b) Design a septic tank to treat the wastewater generated from a population of 250 persons with an assured water supply of 100 liters per capita per day. 6. a) Explain the principles of biological treatment of sewage. b) Explain chemical precipitation with reference to waste water treatment.

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c) The flow of sewage from a primary clarifier to a standard rate trickling filter is 4.6 MLD. The 5 day BOD of the influent is 160 mg/l. Determine the volume of the filter media required for the standard rate trickling filter and its depth given the following : Organic loading : 160 g/m3/day Hydraulic loading : 2100 l/m2/day.

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7. a) What is sludge digestion ? Explain different stages of sludge digestion.

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b) Draw the flow diagrams of an activated sludge process and its working briefly.

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c) List the low-cost treatment units. What are their advantages ?

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8. a) Explain with a neat sketch construction and working of a septic tank. How effluent from septic tank is disposed ?

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b) Design an oxidation pond for treatment of domestic wastewater discharged from a residential colony with 5000 persons contributing 120 lpcd. The 5 day BOD of wastewater is 300 mg/l. 10 ———————