Download GTU BE/B.Tech 2018 Winter 7th Sem New 2171306 Wastewater Engineering Question Paper

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Seat No.:

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Enrolment No.

GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-VII (NEW) EXAMINATION - WINTER 2018

Subject Code: 2171306
Subject Name: Wastewater Engineering

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Time: 10:30 AM TO 01:30 PM

Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

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Q.1 (a) Explain the importance of Equalization process in a wastewater treatment plant. 03
(b) Explain the purpose of following unit operations/processes in a wastewater treatment plant : (i) Screening (ii) Suspended growth biological process (iii) Primary sedimentation (iv) Nitrification 04
(c) Differentiate between domestic wastewater and industrial wastewater. 07

Q.2 (a) Explain the terms : (i) SOR (ii) WOR (iii) Food to microbe ratio 03
(b) Design an aerated grit chamber for an average flow of 8 MLD. 04

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(c) A coarse screen is inclined at angle of 60" to the horizontal. There are 25 numbers of rectangular bars having 20mm size (facing the flow) and a clear spacing of 25mm. Determine the head loss using Kirschner equation, when the bars are clean and approach velocity is 1 m/s. 07

OR

(c) Find out the area of secondary clarifier to be used for ASP using following data, if the sludge has to be thickened to a concentration of 10,000 mg/L

Kg/m3	80	60	50	40	30	20	10
MLSS	4	3	2
Velocity m/d	0.44	0.78	1.7	53	34	62	68	76	83

Q.3 (a) Enlist and explain the operational problems of screens. 03
(b) Write a short note on tube settlers. 04

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(c) Design a primary settling tank for a wastewater treatment plant having a flow rate of 0.5 m³/s assuming SOR value as 32.5 m³/m²-day. Check for WOR and detention time. 07

OR

(a) Draw a flow diagram for sewage treatment with suspended growth biological process. 03
(b) Enlist the different types of mixers used in a wastewater treatment plant and explain any one. 04
(c) Design a cylindrical flash mixing tank by determining the tank dimensions and required input power using following data :

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Design flow rate = 11.5x 10⁶ m³/d
Rapid mix t=35's
Rapid mix G =600s^-1
p=1.5195x 10^-3 N/ m²—s 07

Date: 29/11/2018

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Total Marks: 70

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Q.4 (a) Explain the operational problem of Bulking sludge. 03
(b) Differentiate between diffused aeration and mechanical aeration 04
(c) For a flow rate of 0.05657 m³/s and average BOD₅ concentration of 140 mg/L in primary treated effluent , find the volume of aeration tank for a complete mix ASP for following conditions : 07

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1. The treated effluent should have 30 mg/L BOD and 30 mg/L SS
2. Assume BOD of SS =33 % of SS
3. Ks=100 mg/L BOD, µm=2.5 d^-1. Y =0.5, kd=0.05d^-1

Also calculate HRT and F/M ratio.

OR

(a) What is Bio tower? Explain its working. 03

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(b) Write a short note on Sequencing Batch Reactor 04
(c) Design a Rotating Biological Contactor to treat a flow of 50 MLD of primary treated wastewater having BOD₅ of 200 mg/L. Desired effluent BOD₅ is 30 mg/L. 07

Q.5 (a) Prepare a list of sludge dewatering devices and explain any one along with a neat sketch. 07
(b) Determine the dimensions of UASB reactor for wastewater having flow rate of 1500m³/d. The characteristics of wastewater are as under: 07
BOD = 300 mg/L

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COD= 450 mg/L
TSS=400 mg/L
VSS=270 mg/L
Sulphate = 85 mg/L
Assume required data.

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Also estimate the methane gas generation rate.

OR

(a) Differentiate between Standard rate and high rate digester. 03
(b) Design an oil and grease trap to remove 170 mg/L of O& G for a flow of 45000m³/d of domestic wastewater. 04
(c) Find out the volume of equalization tank to get a constant out flow for the hourly flow rate variations as given in table below: 07

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Time	0	1	2	3	4	5	6	7	8	9	10	11
Flow m3/s	0.0875	0.0725	0.0514	0.0434	0.0318	0.0382	0.0353	0.063	0.111	0.1315	0.135	0.135
Time	12	13	14	15	16	17	18	19	20	21	22	23
Flow m3/s	0.1351	0.129	0.123	0.1131	0.103	0.1034	0.1045	0.1156	0.127	0.128	0.128	0.118

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