G.H. R AISONI COLLEGE OF ENGINEERING NAGPUR
CIVIL ENGINEERING DEPT.
SEM : VIII
SUB: WATER AND WASTE WATER TREATMENT ( Elective III)
( QUESTION BANK)
UNIT I
Q1
–
Draw layout of conventional water tr
eatment plant and explain the function of each
in detail.
Q2
–
Explain the types of aerators with figures.
Q3
–
Design the cascade types of aerator for the design flow 25MLD.
Q4 Explain the objectives of aerators.
Q5 Explain ‘ Two film Theory ’ of gas
transfer
.
UNIT II
COAGULATION
Q6

Explain the theory of coagulation. Describe various types of coagulants commonly
used in water treatme
nt.
Q7 Write short note on ‘ Alum’ state advantages and disadvantages of it.
Q 8 How to find out the optimum dose of coagulant
Q 9 Write short note on ‘Coagulation Aid’
Q10 State the factors affecting coagulation.
RAPID MIXER (FLASH MIXER)
Q11 State the design criteria for Flash mixer.
Q12Design the flash mixer for the design discharge of 250 m3 / hr.
Q13 What are the different methods of mixing device and explain each in detail.
Q14 Explain t
he relation of pH
–
alkalinity and turbidity in the coagulation.
FLOCCULATION
Q15
–
Explain the theory of flocculation.
Q16 State the design steps for floculator as per CPEEO.
Q17 Design the clar
rifloculator for the design flow 250 m3 / hr . Assume suitable data.
SEDIMENTATION
Q18 What are the factors on which the sedimentation depend. And explain in brief.
Q19 Prove that removal of particulate is depend on the plan area only.
Q20 Write short note on ‘ Tube Settler’
Q21 Explain in detail the procedure
for flocculate and discrete particulate removal from
Sedimentation tank.
Q22 3.785 MLD passes through a sedimentation basin, which is 6m, wide, 15 m long
and 3 m deep.
a) Find the detention time for the basin
b) What is
the average velocity of flow through the basin
c) If the suspended solid content of water averages 40 ppm, what weight of dry
solids will be deposited every 24 hours? Assuming 75 percent removed in basin?
d) Calculate surface overflow rate.
Q2
3
–
Design a settling basin is designed to have a surface overflow rate of 32.6 m/day.
Determine the overall removal obtained for a suspension with size distribution
given below. G = 1.2 and dynamic viscosity 1.027 centipoises and d
ensity 0.997
gm/cm3
Particle
size
( mm)
0.1 0.08 0.07 0.06 0.04 0.02 0.01
Weight
fraction
greater
than size
( %)
10 15 40 70 93 99 100
UNIT III
FILTRATION
Q24 What is the criteria for sand used in the filter.
Q 26 State the difference between slow and rapid sand filter.
Q27 Write a short note on classification of filter.
Q28 What are the problems in Filte
r and Explain the theory of filtration.
Q29. What is air binding ( Negative head in filter) Explain in brief.
Q30 Find the depth of filter bed for the following data
Filtration rate = 5 m3/m2/ hr.
Diameter of particle 0.6mm
Loss of head = 2.5 m
Q31 Estimate the depth of gravel bed for 2mm,5mm and 10mm. Assume suitable data.
Q3
2 Design completely a rapid sand filter for a town having total filtered water
requirement of 6 MLD. Assume suitable data. Assume 3% of filtered water required
for back washing.
Q33 The particle size distribution of the stock sand t
o be used in filter as follows.
Sand size
(mm)
0.21 0.3 042 0.84 1012 10.68 2.38
Cumulative
weight n
%
3.6 11 22 42 64 84 90
The desired effective size of the filter sand is 0.5 mm and uniformity coefficient is 1.5.
Determine the
diameters of the finer and courser particles that are required to be
removed from stock sand.
Q34 What do you understand by loss of head and negative head in rapid sand filter?
What are their permissible limit? What will happen when negativ
e head is
excessive?
Q35 Explain the chemistry of chlorination
Q36 What are the factors affecting bacterial efficiency of chemical disinfectant
( Clorine).?
Q37 Write short note on Ozone and Uv disinfectant.
Q36 Write short not
e on disinfecting action of chlorine.
Q38 What is break point chorination. Explin the under what condition it is advocated?
Q39 State the requirements of disinfectant?
Q40 Explain the kinetics of Disinfections.
Q41 Result of chlorine demand test on a raw water is as follows
Sample
No
Chlorine dosage
( mg/L)
Residual chlorine
after 10 minutes
contact ( mg/L)
01 0.2 0.19
02 0.4 0.36
03 0.6 0.50
04 0.8 0.48
05 0.9
0.34
06 1.0 0.20
07 1.2 0.40
08 1.4 0.60
09 1.6 0.80
Sketch a Chlorine Demand curve What is break point dosage. And what is chlorine
demand
Q42 Chlorine usage in the treatment of 20000 cubic meter of water per day is 8 Kg/day.
Th
e residual chlorine after 10 mints contact is 0.2 mg/L calculate the dose of
chlorine in mg/L and chlorine demand of water?
Q43 Calculate the quantity of bleaching poder required per year for disinfecting 5 MLD
water. The dose of chlo
rine ha to be 0.3 ppm and bleaching powder contain 30% of
available chlorine.
Q44 If 0.7 mg/L of total chlorine is required for satisfaction disinfections of water at
pH =7.0. What dosage will be necessary at pH = 8.0 If it is given t
hat initially 12
minutes cotact time is required at pH 7.0 Find the time of contact required at pH =
8.0 if n= 1.5 in the equation Cn t = Constant. Take Ki = 2.7 x 10

8 mol/L.
Q45. What are the different methods for removal of iron
and Manganese? Explain each
in brief . what the permissible limit in drinking water and what happens if these
are more than permissible limit in drinking water.
Additional Questions
Q1 Explain t
he double diffuse Theory and what is Zeta potential.
Q2 What is gas transfer? Derive the formula for rate of gas operation?
Q3 Explin Two Film Theory.
Q4 Find the driving head that will be required to expose water for 2 seconds on the
assu
mption that the coefficient of velocity is 0.92 for
1) Vertical jet
2) Jet inclined at an angle of 450 with horizontal
3) Also find associated carry and rise.
Q5 Find the time of exposer for water falling through a hight of 3.0 m. in
1) Single Descent
2) Double Descent
Q6 Derive the equation for time of exposer ‘t’ for gravity aerator, when water fall from
the height ‘h’ through ‘n’ of desent.
Q8 Write detailed note on Taste and Odour removal from water.
Q9 Explain back washing in Rapid sand filter. How it will come to know the filter is at
the position of backwashing? What is the limit.
Q10Water Zigzag through a baffled cha
nnel at a velocity of 0.3 m/sec and speed up to
0.7 m/s. in the slots. There are 19 around the end baffled Find
1) Loss of head neglecting channel friction
2) Power Dissipated
3) G and Gt value
Flow of water is 25 Mld and displaceme
nt time is 30minutes.
Q11 A rectangular sedimentation basin is to handle 10 MLD of raw water. A detention
Basin of width to length ration 1/ 3 is proposed to trap all particles larger than 0.04
mm in size. Assuming a relative den
sity of 2.65 Calculate the detention time if the
depth of tank is 3.5 m.
Q12 A settling analysis is run on flocculated particle. Is run . the initial solid
concentration is 250mg/L the resulting matrix is shown below. What will be
the
overall removal efficiency of the settling basin which is 3.0 m deep with detention
time 1 hour 45 mints.
Time of sampling (minutes)
Depth
( m)
30 60 90 120 150 1
80
0.5 133 83 50 38 30 23
1.0 180 125 93 65 55 43
1.5 203 150 118 93 70 58
2.0 213 168 135 110 90 70
2.5 220 180 145 123 103 80
3.0 225 188 155 133 113 95
What will be the theoretical removal efficiency in the settlin
g basin with the loading rate
of 25 m3/m2/ day
Q13 A filter unit is 4.5 x 9.0 m. After backwashing 10000 cubic meter per day in 24
hours, the filter is backwashed at the rate of 10 lit/ sec/m2 for 15 minutes. Calculate
the average
filtration rate, quantity and percentage of treated water used in washing
and the rate wash water flow in each trough. Assuming 4 troughs.
Q14Explain the Underdrainage system ( UDS) with sketch in Rapid sand filter and state
t
he specification of laterals opening
Q15 Define ‘ Effective size and ‘ Coefficient of Uniformity” of filter sand. Give the
values for slow and rapid sand filter.
n1S fn an b硰eriment of removal of Cl2 from water sprayed in to the air
in the
spherical droplets 0.25 cm in diameter, the initial super saturation of water with
Cl2 was 23 mg/i. After 1 second of exposer, this was reduce to 10mg/i.cind
†††
Coefficient of gas transfer
Q13 A settling analysis is run on discrete particles . the column is 1.8 m and data are
given as shown
Time
( min)
0 60 8
0 100 130 200 240 420
Concentration ,
mg/L
300 189 180 168 156 111 78 27
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