Academic Session 2003 12004 September/October 2003
IEK
3O9E- CIIEMODYNAMICS
Time:3
hoursPlease check
that the
examination paper consistsof TEN printed
pages before you commence this examination.Answer
FIVE
questionsonly.
Students are allowedto
answerall
questionsin
English OR Bahasa Malaysia OR combinations of both.IEK
30eE]-2-
l. A
natural stream 0.8m
deep flowswith
an average velocity at 0.10 m/s.At
a pointwhere the waste outfall enters the stream after
homogeneousmixing
the concentration of the oxygen demanding organic materialsis
30 mglL. The oxygen demanding materials decays andutilizes
oxygen accordingto the given
equationpaz at 0.5 per day;
paz =
porrexp(-k)t*)
&
=p)r-
po*tkor: (
$azv *lh)'''
Ln=
p)r:8.84mg/l @20oC
$az:1.8 E-5
cmz/st--
Lv2
Calculate what is the:
(a) Liquid
mass transfer coefficient,(b)
The dissolved oxygen concentrationat
15 kilometers downsffeamif
the aftermixing
homogeneous concentration at theoutfall po* = 6
mg/L.Assume the stream water temperature is 20oC ....)t-
I.
S-ebqnng sungai semulajadi kedalamannya 0.8 m mengalir dengan kelajuanpurata 0'10 m/s' Pada satu titik
dimana terdapat satutitik
puncayang meidiscas
sisa lredalam sungai dimana didapati bahowa kepekatan oksigenseteih air
bercampur secarahomogen ialah
30 mg/L.Jika
tradar reputanbaian
sisaialah
0.5per hari
dan lreperluan oksigenbagi
bahan sisa mereput mengilatt persamaanseperti
pnz yang diberikan ;pBz =
pfrexp(-kut*)
Lo^=
P)z-
P?,Kirakan berapakah:
(a)
Koefisien pemindahanjisimfasa
cecair^ n =
ffil *onot, - *r(+)l . o, *r(+)
p)r:
8.84ng/l
@20'C
9,a2
:1.8
E-5 cm2/s Lv2
'knr : ( Spvr/h)o
@
Kepelratan oksigen padajarak
15 kilometerdari
titek puncajika
kepetcatan oksigenpada titek
punca percampuraniatah pfl, = 6 mg/L.
Anggapknn bahawa suhuair
sungai ialah pada 20oC .(100 markah)
...4/-
IEK
30eE]-4-
2.
Referringto
the equation and data givenin
questionI
and base onthe following
given equations:L's
=
Lotpsz
- P|z At
t=0 atinitial
conditions;t,
=(,+,
_ k;"l
^-, ^t(!o+ n*:)rl
Calculate what is:
(a)
Concentrationof the
remaining wastein mg/L at the point
mentioned in question 1 part a).(b)
The critical time t" and distance in kilometer where the oxygen concentration is at a minimum level ?(c)
Show and express graphically the mentioned values.2.
Berpanduknnpada
persamaandan data yang di berikan dalam soalan I
danpersamaan yang diberikan:
A,,
=
Lo,Pr, - Porz Bila t:0
sebagai situasi permulaan;t - =
+, hl lL
o-
o'"( C t' ^' !n>^-t")r]
.
t'rn,rn)-*,lhk;' ^( krpX, f )
Kirakan berapaknh:
(a)
Kepelratanbaki bahan
sisa dalam mg/L padajarak
yang seperti disebutkan pada soalanI
bahagian a).5/-
3.
(b)
Masa knitil(nl t" danjarak
dalam kilometer dimana kepekatan olcsigen adalah pada tahap minima ?(c)
Lalrarlcannilai nilai
tersebut dalam bentuk gambarajah.what is the
hydraulic radius(ffl, the
interfacial air-water per average surface velocity (u"u) for the followingcondition
where:Given
,u =Vr'/3St/2 Where: U =velocity,mps
nn:
coefficient offriction
, 0.0316= hydraulic radius ,
A/p
mA:Cross
Section area, m2P:
wetted perimeter, mSo:
slope m/m((
10,)(100 markah)
uolu*e bau
and
Kirakan
jejari hidrautik (/1), Iuas
antaramukaair-udara per isipadu bau
purqta halaju permukaan
(u*)
untuk keadaanberilai
dimana: danu
=l'49 ,''tg'''
n
Di
beri bahawa:Di mana: U =halaju,
mpsn:
laefisien geseran, 0.03 16:jejari hidraulik,,Up
mA:Luas
x sekqten, m2P :
perimeter basah, mSo:kecerunan m/m (<10"
)
The depth h of the river
is
12 meter (ma,rimum) and the 'Satu sungaiyang
mempunyai kedalamanh
sebanyak dan panjangnya b ialah 40 meter.length b
is
40 meter.12
meter (malcsimum) (50 markah)3.
(a)
(a)
IEK
30eE]-6-
(b) A river
having a triangular bottom shape an angleof
45owith
depthh,
12 meter (ma:rimum) and the bottomwidth b,40
meter.(b)
Satu sungai yang berbentuk tigasegi bersudut 45o mempunyai kedalaman h, 12meter
(maksimum) dan lebar dasarnya,b
40 meter.(50 markah)
4. (a)
Derive the equation for the desorption process in a plugflow
reactor (plugflow
basin). Start the derivation based on the mass transferof
a speciesA.
Refer to the given figure below.Where:
h= depth
ofreactor
0):
width of reactorX6:
molar average speciesA A=Area =(Az)W
8",
:
Interfacial area per unit volumeWe: vhrrrc2
(b)
Intergrate the derived equation in part a) Using the boundary condition values wherer0,
atXa: Xal andrL at X6: Xrz
to generate the equation given below.Xaz
:Xar
exp [ -rk62&
v/
We].a.y,.l
=
0wao
plug flow basin.
r lf r
Water4' (a)
Terbitkan persamaan bagi satu proses penjerapan didalam satureahor aliran plug (plugJlow
basin). Mulalcan dengan imbanganjisim
bagi bahan A. Rujukrajahyang
diberilmn di bawah.Dimana:
h:
kedalamanreahor A):lebar
reaktorX1 = mole purata bahan A
A: luas :
(Az)WQ,
= Iuas antaramukaper
isipaduV[n: vhax2
(b) Kamirkan persamaan yang diterbitkan pada bahagian a)
dengan menggunakannilai
tertentu z=0 pado XA = X.qt dan z=L padaX1 :
Xe2 untukmenghasilkan persamenn seperti dib aw ah.
X.ez
:
X.4 expI J
k12 Ct"v/
WaJ.r_/..1
=
o(100 markah)
I lr I
Water3
0lrectronlrEK
309E1-8-
5.
Refer to the given figure 5.1 below. Prior to a second downstream sewage treatmentplant (STP) coming on-line during which time septic system were used,
abacteriological study had been conducted
for total E.Coli
andthe result of
the survey is given in the table as follows:MPN = most probable number bacteria
If
thetotal coliform
countsin
both STP effluents are 3x106 MPN/100m1 without chlorine disinfection,what
percentkills
mustbe
achievedby
disinfectionat
the treatment plant to meet a beach totalcoliform
standardof
2000MPN/100m1 so that the beach can be used for bathing and beach activity.Assume that equal reduction at both treatment plant and neglect STP
flows in
theflow
balance.5. Lihat
rajah 5.1 yang diberikandi
bawah. Sebelum titik punca kedua yang berunsureffluen
domestikdi discas
kedalamsungai satu kajian baheria
menunjukkan bahawajumlah
E.coli di dalam sungai berknitan ialah seperti di dalamjadual:
MPN
:
most probable number bacteria.Jilra jumlah
purata
bilangan E. colipada
kedua-dualoji
pengolahanadalah
3x106 MPN/100m1 tanpa rawatan pengklorinan, berapakah peratus penurunan dicapai menerusipengHorinan di loji rawatan
supayajumlah bilangan
balderia pada lra,vasanpantai
dibahagianhilir
tapakloji
adalah 2000MPN/I00ml dan selamatuntuk
berkelah dan mandi manda.Anggaplcan setiap ra,eatan
Horin
memberi lcesan yang samqpada
kedua dualoji
rswatan
air
htmbahan....91-
--'Beach 0.5
f\4 G D| :::'
I
lsrer
I e' = 1.0 h4cD
Y
Q=50cfs
U = 0.7 fps t- 3knn I 2'r4flr
I_i--__-_--
STP
=
SewageTreatment plant cfs = cubj-c feet per
secondfps = feet per
secondMGD
= Million gallon per
dayRAJAH
5.I
(100 markah)
6. The given
equationbelow
showsthat the
rateof
decayof the
organic material follows the first order.S = S,
exp(-Kt*)
(a)
Plot the figures for S versus t on a Cartesian coordinate.(b)
Plot the figures for ln S versus t on a semi- loe.lrEK
30eEl-10-
(c)
Show on the figure that indicates the waste input into a river or a canalwith
avelocity U using the above equation.
(d)
What is meant by the parameterK
in the above equation.6.
Persamaandi
bawah menunjukkan kadar bahan organik mereput mengihtt tindak balas order pertama.S = S,
exp(-Krx)
(a)
Plotkan rajah parameter S lawan t pada graf kartesan.(b)
Plotlcan rajah ln S lawan t pada kertas semi- log.(c)
Tunjukkan denganrajah yang
menggambarkan input suatu lepasanair
sisayang
mengalir mqsuk ke dalam sungai ataualur pada halaju U
berhubung dengan persamaan di atas.(d)
Apakahyang dimaksudlaan dengan parameterK
dalam persamaan di atas.(100 markah)
ooo000ooo