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Second Semester M.E. (Environmental Engineering) (Civil) Degree Examination, June/July 2015 (2K8 Scheme) EN 201 : ADVANCED WASTE WATER TREATMENT Time : 3 Hours

Max. Marks : 100

Note : i) Answer any five questions. ii) Assume any missing data suitably. 1. a) List the objectives of advanced wastewater treatment and explain the need for advanced wastewater treatment.

10

b) Explain the settled secondary effluent filtration with chemical addition.

10

2. a) Explain the process of removal of suspended solids by micro-screening and its design criteria. 10 b) Discuss the different types of granular medium filters used in treatment of wastewater.

5

c) Estimate the amount of liquid alum required to precipitate phosphorus in a wastewater, which contains 12 mg phosphorus per liter. Also determine the required storage capacity if a 30 day supply is to be stored at the treatment facility. Based on the laboratory testing 1.6 mole of Al will be required per mole of phosphorus. The flow rate is 20,000 m3/day. The following data are for the liquid alum supply. Formula for liquid alum Al2(SO4)318 H2O, Alum strength = 48%, Density of Liquid alum solution = 1, 71 4kg/m3.

5

3. a) Explain the application of attached growth system for separate stage nitrification process. 10 b) An extended aeration plant is operated as a biological nitrification-denitrification process. The aeration tank has a volume of 8000 m3. Based on several months operating data, the average wastewater flow was 6000 m3/d with the following characteristics; 260 mg/L BOD, 300 mg/L SS, 50 mg/L total N and 30 mg/L NH3-N. The average effluent quality was 5 mg/L BOD, 8 mg/L SS, 7 mg/L total N. 4 mg/L NH3-N and 2 mg/L NO3-N. The operating MLSS concentration averaged 4500 mg/L and the temperature was in the range of 16 to 20° C. Calculate the volumetric BOD loading, F/M ratio, aeration period, BOD removal, SS removal and total N removal. 10 P.T.O.

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4. a) Explain the process of ion exchange for the removal of dissolved inorganic substances.

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b) Calculate the residence time for an anoxic basin used for denitrification for the following conditions. Influent nitrate to the basin = 50 mg/L Effluent nitrate from the basin = 10 mg/L ML VSS = 2000 mg/L Temperature = 10°C D.O = 0.1 mg/L UDN(20° C) = 0.10 day–1.

5

c) For reuse estimate the daily requirement of chlorine and the resulting buildup of total dissolved solids, when breakpoint chlorination is used for seasonal control of nitrogen for the plant flow rate of 3500 m3/d, with effluent characteristics : BOD5 = 20 mg/L Suspended solids = 25 mg/L NH3-N concentration = 23 mg/L Required effluent NH3-N concentration = 1.0 mg/L

10

5. a) What are refractory organics ? Explain how the process of activated carbon adsorption can remove refractory organics. 10 b) Explain the different methods used for combined removal of nitrogen and phosphorous by biological methods with flow diagrams. 6. a) Mention the different methods of thickening of sludge. Explain any two.

10 10

b) Determine the liquid volume before and after digestion and the percent reduction for 500 Kg dry basis of primary sludge with the following data : Primary

Digested

Solids %

5

10

Volatile matter %

50

50 (destroyed)

Specific gravity of fixed solids

2.5

2.5

~1.0

~1.0

Specific gravity of volatile solids

10

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7. a) What is sludge digestion ? Explain the process microbiology of anaerobic sludge digester.

10

b) Determine the length and number of discharge ports for a multiport diffuser that will provide a near field dilution of 10 when discharging a maximum flow of 3.0 m3/s, in a river under low flow conditions, the river water depth is 1.0 m and the current speed is 0.6 m/s. 10 8. Write short notes on any four of the following : a) Control of membrane fouling. b) Sodium absorption ratio. c) Sludge disposal. d) Pretreatment for Nanofiltration and Reverse osmosis. e) Electrodialysis. f) Sludge conditioning. ———————

(4×5=20)