ED – 710

*ED710*

VI Semester B.E. (Civil) Degree Examination, December 2014/January 2015 (2K11 Scheme) CE – 604 : ENVIRONMENTAL ENGINEERING – II Time : 3 Hours

Max. Marks : 100

Instructions : i) Answer five questions selecting a minimum of two from each Part. ii) Assume any missing essential data suitably. PART – A 1. a) Differentiate between conservancy system and water carriage system of sanitation.

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b) Write the effect of variation in sewage flow on the design of various components of sewerage scheme.

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c) Design a sewer to serve a population of 36000.The daily per capita water supply allowance being 135 liters, of which 80% finds its way into the sewer. The slope available for the sewer to be laid is 1 in 625 and the sewer should be designed to carry four times the dry weather flow when running full. What would be the velocity in the sewer when running full ? Assume n = 0.012 in manning’s formula.

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2. a) Explain the decomposition cycle of nitrogen with neat diagrams.

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b) What is sewage farming ? What are its advantages over the method of disposal of sewage by dilution ?

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c) A town disposes sewage by land treatment. It has a sewage form of area 150 hectares. The area included an extra provision of 50% for rest and rotation. The population of the town being 50,000 and rate of water supply 150 liters per capita per day. If 75% of the water is converted into sewage, determine the consuming capacity of the soil.

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3. a) Discuss the various natural forces helps in the purification of streams.

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b) Draw a neat sketch of a drop manhole and indicate where it is used.

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c) Explain oxygen sag curve with a neat sketch.

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d) If the 5 day 30°C BOD of a sewage sample is 110 mg/L. Calculate its 5 days 20°C BOD. Assume the deoxygenation constant at 20°C,k20 as 0.1.

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P.T.O.

ED – 710

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*Ed710*

PART – B 4. a) Explain the working of an Activated Sludge Process with a flow diagram. b) List the different modified Activated Sludge Processes and explain any two.

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c) Design a set of Activated Sludge units to treat 5 MLD of sewage for the following data : BOD of raw sewage = 260 mg/L Suspended solids = 250 mg/L BOD removal in primary clarifier = 60 mg/L BOD desired in the final effluent = 20 mg/L.

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5. a) Compare the salient features of standard rate and high rate trickling filters.

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b) Explain the principle of treatment and construction details of septic tank.

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c) Determine the size of a high rate trickling filter for the following data. Sewage flow = 4.5 MLD BOD of raw sewage = 250 mg/L Final effluent BOD desired = 30 mg/L Recirculation ratio = 1.5 BOD removal in primary clarifier = 30%.

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6. a) Explain the different stages in the sludge digestion process under anaerobic conditions.

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b) Calculate the dimensions of an oxidation pond and determine the detention time to treat one million liters of sewage per day of a city located in an area of hot climate. The 5 day BOD of sewage is 300 mg/L.

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c) Design a septic tank for a small colony for 150 persons provided with an assured water supply from the municipal head-works at a rate of 120 liters per person per day.

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ED – 710

7. a) Describe one pipe and two pipe system of plumbing for buildings and state their merits and demerits. b) Draw a typical floor plan of a house, showing the position of different sanitary fittings, traps, pipes, inspection chambers and show its connections with public sewer assuming necessary slopes are available.

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c) Design a digestion tank for the primary sludge with the help of following data, Average flow of sewage : 30 MLD Total suspended solids in raw sewage : 200 mg/L Moisture content of raw sludge : 95% Moisture content of digested sludge : 85% Solids removed in the primary settling : 65%

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8. Write short notes on the following : i) Gully trap and S-trap ii) Symbiotic relationship in oxidation ponds iii) Sludge volume Index iv) Grit Chamber.

(4×5=20) _________________