Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Winter 7th Sem New 2171306 Wastewater Engineering Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VII (New) EXAMINATION ? WINTER 2019
Subject Code: 2171306 Date: 03/12/2019
Subject Name: Wastewater Engineering
Time: 10:30 AM TO 01:30 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Write down operational problems with its solution occurred in aerated grit
chamber.
03
(b) A wastewater flow of 0.60 m
3
/min containing 150 mg/L of oil and grease is to be
reduced to a concentration of 25 mg/L. Assuming the following data, design a
dissolved air flotation system.
Surface loading rate (SLR) = 130 L/m
2
-min; Wastewater temperature = 35?; Air
solubility at 35? (Sa`) = 17.15 ml/L; A/S = 0.025 (mL/mg); Fraction of air
saturation (f) = 0.80 and Recycle system pressure = 500 kPa.
04
(c) Determine the size, dimensions and HRT of a UASB reactor which will be used
for the treatment of an industrial effluent. The wastewater is mainly soluble,
containing carbohydrate compounds and a granular sludge is expected. Suppose
90% soluble COD removal, 50% of the influent pCOD degraded and 90% of
influent sulfate is reduced biologically. Methane production at 35?C = 0.40 L
CH4/g COD; Reactor volume effectiveness factor = 85%, density of methane at
30?C = 0.6451 g/L and height for gas collection = 2.5 m. Also determine total gas
production (assuming 65% methane), energy available from methane and
alkalinity requirements.
Item Value
Flow Rate 1000 m
3
/day
COD 2300 mg/L
sCOD 2000 mg/L
Alkalinity 500 mg/L as CaCo3
SO4 200 mg/L
Temperature 30?C
07
Q.2 (a) Differentiate between domestic wastewater and industrial wastewater. 03
(b) Design a cylindrical flash mixing tank by determining the tank dimensions and
required input power using following data: Design flow rate = 11.5 x 10
3
m
3
/d,
Rapid Mix time= 5 s, Rapid mix G =600 s
-1
and ? = 1.5195 x 10
-3
N/m
2
.s..
04
(c) Design a grit chamber having a rectangular cross-section and a proportional weir
as the velocity control device, with the following supplied data:
Maximum flow = 12 MLD; Maximum temperature = 26?C; Minimum temperature
= 15?C; Specific gravity of grit particles = 2.65 and Diameter of smallest grit
particles to be removed = 0.02 cm.
07
OR
(c) Assuming suitable design criteria, compute the dimensions of a rectangular
settling tank to remove suspended flocculent particles from the average
wastewater flow of 15000 m
3
/d. A column test indicates that an overflow rate of
40 m/d will produce satisfactory removal of suspended floc at 3.5 m depth.
07
Q.3 (a) Write down operational problems of UASB. 03
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VII (New) EXAMINATION ? WINTER 2019
Subject Code: 2171306 Date: 03/12/2019
Subject Name: Wastewater Engineering
Time: 10:30 AM TO 01:30 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Write down operational problems with its solution occurred in aerated grit
chamber.
03
(b) A wastewater flow of 0.60 m
3
/min containing 150 mg/L of oil and grease is to be
reduced to a concentration of 25 mg/L. Assuming the following data, design a
dissolved air flotation system.
Surface loading rate (SLR) = 130 L/m
2
-min; Wastewater temperature = 35?; Air
solubility at 35? (Sa`) = 17.15 ml/L; A/S = 0.025 (mL/mg); Fraction of air
saturation (f) = 0.80 and Recycle system pressure = 500 kPa.
04
(c) Determine the size, dimensions and HRT of a UASB reactor which will be used
for the treatment of an industrial effluent. The wastewater is mainly soluble,
containing carbohydrate compounds and a granular sludge is expected. Suppose
90% soluble COD removal, 50% of the influent pCOD degraded and 90% of
influent sulfate is reduced biologically. Methane production at 35?C = 0.40 L
CH4/g COD; Reactor volume effectiveness factor = 85%, density of methane at
30?C = 0.6451 g/L and height for gas collection = 2.5 m. Also determine total gas
production (assuming 65% methane), energy available from methane and
alkalinity requirements.
Item Value
Flow Rate 1000 m
3
/day
COD 2300 mg/L
sCOD 2000 mg/L
Alkalinity 500 mg/L as CaCo3
SO4 200 mg/L
Temperature 30?C
07
Q.2 (a) Differentiate between domestic wastewater and industrial wastewater. 03
(b) Design a cylindrical flash mixing tank by determining the tank dimensions and
required input power using following data: Design flow rate = 11.5 x 10
3
m
3
/d,
Rapid Mix time= 5 s, Rapid mix G =600 s
-1
and ? = 1.5195 x 10
-3
N/m
2
.s..
04
(c) Design a grit chamber having a rectangular cross-section and a proportional weir
as the velocity control device, with the following supplied data:
Maximum flow = 12 MLD; Maximum temperature = 26?C; Minimum temperature
= 15?C; Specific gravity of grit particles = 2.65 and Diameter of smallest grit
particles to be removed = 0.02 cm.
07
OR
(c) Assuming suitable design criteria, compute the dimensions of a rectangular
settling tank to remove suspended flocculent particles from the average
wastewater flow of 15000 m
3
/d. A column test indicates that an overflow rate of
40 m/d will produce satisfactory removal of suspended floc at 3.5 m depth.
07
Q.3 (a) Write down operational problems of UASB. 03
2
(b) Design a bio-tower system to treat a wastewater flow of 10 MLD having settled
BOD5 = 175 mg/L & to be operated at 25?C. The depth of modular plastic media
to be used is 6.0 m & recirculation ratio will be 2:1. The treatability constant
determined at 20?C = 0.06 min
-1
& desirable concentration of effluent is 20 mg/L.
04
(c) Assuming suitable design criteria, design a trickling filter system to treat an
average domestic wastewater flow of 10 MLD having influent BOD5 equal to 250
mg/L. The desired effluent BOD5 is 25 mg/L or less.
07
OR
Q.3 (a) Write the Eckenfelder equations (with & without recirculation) for Bio tower
design.
03
(b) Enlist and Explain the operational problems of chemical unit operations. 04
(c) Estimate the size of digester required to treat the sludge from a primary treatment
plant designed to treat 38000 m
3
/d of wastewater. Check the volumetric loading,
estimate percent stabilization and the amount of gas produced. For wastewater to
be treated, it has been found that the quantity of dry volatile solids and
biodegradable COD removed is 0.15 Kg/m
3
and 0.14 Kg/m
3
, respectively. Assume
that the sludge contains about 95% moisture and has a specific gravity of 1.02.
Assume hydraulic regime of the reactor is complete mix. (SRT =10 days @ 35?C;
Efficiency of waste utilization =0.70; Y =0.08 Kg VSS/Kg bCOD utilized; k d =
0.03 d
-1
and digester gas is 65% methane)
07
Q.4 (a) Explain the factors responsible for bulking of sludge. 03
(b) An activated sludge plant is to be designed for 10 MLD domestic wastewater flow
to operate at 10 days MCRT and 6 hours of HRT. Assuming BOD5 20?C as 175
mg/L in influent to the aeration tank, sludge wasting flow equal to 70 m
3
/d and
return sludge concentration equal to 8000 mg/L, determine the concentration of
MLVSS to be maintained in the aeration tank to achieve effluent BOD5 of 30
mg/L. Also determine the recirculation ratio at which plant should be operated.
Assume the kinetic coefficients Kd = 0.06 d
-1
and Y = 0.6.
04
(c) Explain the phases of SBR operational cycle with neat sketch. 07
OR
Q.4 (a) Write a short note on extended aeration. 03
(b) Explain the working mechanism of Rotating Biological Contractor with neat
sketch.
04
(c) Design a rotating biological contactor to treat 10 MLD flow of municipal
wastewater having BOD5 concentration of 250 mg/L. The primary treatment
removes 30 % raw BOD5 and desired effluent BOD5 is 250 mg/L. Assume 0.05
m
3
/m
2
-d hydraulic loading and other suitable data if needed.
07
Q.5 (a) Enlist and explain the types of filter presses. 03
(b) Explain various methods of dewatering of sludge. 04
(c) Design sludge drying beds to dewater the digested sludge produced from
wastewater treatment plant based on the activated sludge process designed for
50000 population. Assume other suitable data.
07
OR
Q.5 (a) Define the following terms: (i) Sludge volume index, (ii) Mean cell residence time
and (iii) Mixed liquor suspended solids
03
(b) Explain various methods of thickening of sludge. 04
(c) Write a short note on ?Natural evaporation ?as a treatment of wastewater.
07
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This post was last modified on 20 February 2020