ME – 129

*ME129*

First Semester M.E. (Civil) Degree Examination, July 2016 Major : (Environmental Engineering) 2K8EN101 : ADVANCED WATER TREATMENT Time : 3 Hours

Max. Marks : 100 Note : 1) Answer any five full questions. 2) Assume missing data suitably.

1. a) What is aeration ? State the objectives of aeration in water supplies.

5

b) Discuss the factors influence the transfer of gas in water and with the help of common gas transfer equation explain how the gas transfer can be optimized.

5

c) The initial dissolved oxygen concentration of pond water at 30 cm deep is 2.0 mg/l. Find the concentration after 10 days if the temperature of the water is 20°C, on the assumption that the rate of absorption of oxygen from the atmosphere is sufficiently fast to saturate the surface layer of water in a relatively short time. 10 2. a) Derive an expression for settling velocity of a discrete particle in a settling tank.

10

b) Design a sedimentation tank with a flocculation chamber, to treat 75MLD of water. Also sketch the same.

10

3. a) Explain how does the application of coagulants helps in the purification of water ? Discuss the destabilization of colloids in the treatment of water using Al(III) and Fe (III) salts. 10 b) Determine the settling velocity of spherical particles of size 5.9 × 10–2 cm. The specific gravity is 2.50 and kinematic viscosity at 20°C is 1.08 × 10 –2 cm2/sec. If the specific gravity of another particle of identical size is 1.1, check at what rate the particle will settle or rise. 10 4. a) Explain the action of chlorine as a disinfecting agent in the treatment of water with relevant chemical equations. 10 b) At a concentration of 1 mg/L of chlorine, the time required for 90% kill of target organisms in water is 10 minutes. Compute the concentration of chlorine required for the same percentage of kill in 25 minutes. At this does, estimate the quantity of bleaching powder with 40% available chlorine to treat the water for a town of 1,00,000 persons supplied at the rate of 135 lpcd. 10 P.T.O.

ME – 129

*ME129*

-2-

5. a) Discuss the different rate control patterns adopted in operating filters.

5

b) Discuss the role played by size and shape characteristics of filter media in rapid sand filters.

5

c) Design an under-drainage system to treat 100 MLD of water by rapid sand filters and sketch your design.

10

6. a) Explain the process of adsorption and write in detail any two adsorption isotherms.

10

b) The laboratory data were collected in a batch adsorption study. Plot the data according to the Freundlich isotherm and determine the values for the constants. A volume of 500 ml is placed in each flask, and the waste has an initial COD of 100 mg/L. Flask No. Wt. of Carbon (mg)

Final COD (mg/L)

1.

964

3.4

2.

740

5.1

3.

550

8.2

4.

398

12.6

5.

265

20.5

6.

166

33.2

7.

0

100

10

7. a) Explain the concept of reverse osmosis. Also discuss the necessity of pretreatment of feed before reverse osmosis treatment.

10

b) Explain the method of operation of ion exchange units along with relevant chemical equations. 8. Write short notes on any four of the following : a) Short circuiting in settling tanks b) Disinfection using UV rays and ozone c) Zeta potential d) Filter troubles e) Breakthrough curve f) Electro-dialysis. —————————

10

(4×5=20)