Mid Term Exam

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22 Φεβ 2014 (πριν από 3 χρόνια και 4 μήνες)

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ميحرلا نمحرلا الله مسب

College of
Engineering



Course no :


Student No:


Course Title:

Mid Term Exam

Student Name:


Environmental Engineering

Theoretical Exam

_____________________


[Page
1

of
4

Pages
]


Exam Time:
1.5
Hours

1
st



Se
mester
200
8
-
200
9

Date:


04
/
0
11
/20
0
8


14
:
0
0

No of
Questions
:
F
ife

Total Grade:
30

Try to
Answer
All

Questions

Open Book:

No


Using Computer:
No

Using
Calculato
r:
No




First Question


(
6/3
0)

Define

the following
terms

in

details
?


1.

Non
-
Point Source

Pollution
:

Scattered or diffuse, having no specific location of
discharge.(Agricultural fields, Feedlots Atmospheric Deposition)

2.

BOD: Biochemical Oxygen Demand Amount of dissolved oxygen consumed by
aquatic
microorganisms.


3.

Aeration
:

Aeration is the supply of oxygen from the atmosphere to water to effect beneficial changes in the
quality of the water.

It is a common treatment process for groundwater and less common for surface waters. Aeration is
used

To release excess H2S gas which may cause undesirable tastes and odors.

To release excess CO2 which may have corrosive tendencies on concrete materials.

To increase the O2 content of water in the presence of undesirable tastes due to algae (fishy smell)

To

increase the O2 content of water which may have negative taste, color and stain properties due to
the presence of iron and manganese in solution. The addition of oxygen assists the precipitation of
iron and manganese.


4.

Sedimentation

Sedimentation by defin
ition is the solid
-
liquid separation using gravity settling to remove suspended
solids' (Reynolds, 1982).

In water treatment, sedimentation processes used are:

Type L: to settle out discrete non
-
flocculent particles in a dilute suspension.

Type n: to sett
le out flocculent particles in a dilute suspension





Coagulation

The purpose of coagulation and flocculation is to cause small pollutant particles such as metals to
aggregate and form large enough flocks so that they can be separated from the wastewater th
rough
sedimentation.


ميحرلا نمحرلا الله مسب

College of
Engineering



Course no :


Student No:


Course Title:

Mid Term Exam

Student Name:


Environmental Engineering

Theoretical Exam

_____________________


[Page
2

of
4

Pages
]


6.

Chlorination

(
Reaction
)

chlorine is a yellow
-
greenish gas showing high toxicity to humans and animals

Chlorine can be liquefied at room temperature

CL
2

+ H
2
O H
+

+ CL
-

+ HOCL

HOCL = H
+

+ OCL
-

HOCl molecule
is the most effective compound for the disinfecting process.


Second
Question


(
9
/
3
0)

Answer the

following
questions

1.

What
are

the difference
s

between Fine

Screening
and Micro Screening?

fine screens

are fitted after the coarse screens if storage is not
provided,

If there is storage then fine screens are placed at the outlet of the storage tanks.

typically mesh with openings about 6 mm diameter

circular drum type or a traveling belt

Micro screening

the mesh openings :range from 20 to 40 µm.

used only
as the main (physical) treatment process for relatively uncontaminated waters

2.

What are the Factors that
cause

lower efficiency of disinfection?

Turbidity

Resistant organisms (Giardia)

High amount of organic material

Deposits of iron and manganese

Oxidizabl
e compounds


3.

What are the most commonly used disinfectants?
(Discuss two of them)?

Chlorine dioxide

Ozone

UV radiation

Chlorination


4.

How the rate of destruction of micro
-
organisms

is postulated

(Equation)?

The rate of destruction of micro
-
organisms is ofte
n postulated as a first
-
order chemical reaction





ميحرلا نمحرلا الله مسب

College of
Engineering



Course no :


Student No:


Course Title:

Mid Term Exam

Student Name:


Environmental Engineering

Theoretical Exam

_____________________


[Page
3

of
4

Pages
]


Third
Question


(
4

/
3
0)


The flow from the water supply to the treatment plant is shown in the table below. What will be the
needed storage in order to equalize the inflow to the plant?


hour

Flow


(m
3
/
s)

Flow


(m
3
/h)

Cumulative

Flow

(m
3
)

Equalized

Flow

(m
3
/s)

Equalized

Flow

(m
3
/h)

Cumulative

Flow

(m
3
)

Required

Flow

(m
3
)

0


6


0.46

1656

1656

0.59

2124

2124

468

6


12


0.74

2664

4320

0.59

2124

4248

-
72

12


18


0.64

2304

6624

0.59

2124

6372

-
252

18


24


0.52

1872

8496

0.59

2124

8496

0


Fourth Question


(6/30)



Find

the
BOD5
-
Degra
dation

percentage

a
nd discuss the result
s
?

(graphic)



Sample

TC

IC

TOC

COD

BOD
5

BOD
5


(mg/l)


(mg/l)


(mg/l)


(mg/l)


(mg/l)

Degradation

1

800

100

700

2310

1004

89%

2

650

80

570

1881

818

3

500

60

440

1452

631

4

300

40

260

858

373

5

100

20

80

264

115

6

150

0

150

495

215























ميحرلا نمحرلا الله مسب

College of
Engineering



Course no :


Student No:


Course Title:

Mid Term Exam

Student Name:


Environmental Engineering

Theoretical Exam

_____________________


[Page
4

of
4

Pages
]



Fifth Question


(5/30)


Determine the
2
-
day BOD and ultimate BOD for a wastewater whose 5
-
day 2
3

C⁂佄⁩猠

0

浧/L⸠周e
牥ac瑩潮⁣潮獴a湴⁋n‰⸲㍤
-
1

what would have been the 5
-
day BOD if it had been conducted at 25




B佄
t

= UBOD (1
-
e
-
kt) =L 0(1
-
e
-
kt)



2
8
〠0 L〠⠱
-
e
-
〮㈳0㔩




L〠0
㐱4

浧/L†
瑨楳⁩猠⁕sO䐩

䑥瑥t浩湥⁴桥‱
-
摡y BO䐺
-
††

B佄
t

= L0 (l
-
e
-
kt
)



B佄
2

=‴㄰


-
e
-
〮㈳0
2
⤠)
ㄵㄮ1

浧/L

䑥瑥t浩湥⁴桥‵
-
摡y BO䐠D琠㈵


-

䭔‽⁋
3

⠱⸰㐷.T
-
㈰2


䬲㔠K‰⸲ 
ㄮ〴㜩


-
2
3

=‰⸲

B佄㔠= L‰⠱
-
e
-
歴⤠k
㐱0


-
e
-
〮0
5
x㔩‽
293

mg/L



5. Why we use by the
BOD
5
as a standard

measurement of organic matter?





6

Describe the arrangement of single processes in a typical municipal WWTP?
(Sketch)?