1
SPECIALIZED ENGLISH – SEMESTER 5
VAN LANG UNIVERSITY
DEPARTMENT OF ENVIRONMENTAL TECHNOLOGY AND
MANAGEMENT
Chapter 26Chapter 26
FUNDAMENTALS OF BIOLOGICAL FUNDAMENTALS OF BIOLOGICAL
Dr. Tran Thi My Dieu
Sep. 2011
VAN LANG UNIVERSITY DENTEMA
WASTEWATER TREATMENTWASTEWATER TREATMENT
Modeling suspended growth Modeling suspended growth
treatment processtreatment process
CONTENTSCONTENTS
PurposePurpose
The completeThe complete

mix reactor without recyclemix reactor without recycle
VAN LANG UNIVERSITY DENTEMA
The

completeThe

complete
mix

reactor

without

recyclemix

VAN LANG UNIVERSITY DENTEMA
2
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Biomass mass balance
Rate of
accumulation of
ii
Rate of flow of
microorganism
ih
=
-
Rate of flow of
microorganism
fh
+
Net growth of
microorganism
ihi h
VAN LANG UNIVERSITY DENTEMA
m
i
croorgan
i
sm
within the system
boundary
i
nto t

dt
dX

dX/dt = rate of change of biomass concentration in reactor measured as g VSS/m
3
.d
V = reactor volume, m
3
Q = influent flow-rate, m
3
/d
X
o
= concentration of biomass in influent, g VSS/m
3
X = concentration of biomass in the reactor, g VSS/m
3
r’
g
= net rate of biomass production, g VSS/m
3
.d
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Biomass mass balance
'
0
.
g
VrQXQXV











 Xk
S
K
SX
VQX
d
S
m

00
VAN LANG UNIVERSITY DENTEMA


S
d
S
m
k
SK
S


1
1
1
1






d
dS
dm
dS
kYk
kK
k
kK
S




COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Substrate mass balance
Accumulation = inflow – outflow – utilization
Symbolic representation
VAN LANG UNIVERSITY DENTEMA

VQSQS
s
0
0
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Substrate mass balance










S
K
kSX
VQSQS
s
0
0
VAN LANG UNIVERSITY DENTEMA


s



kSX
VSSQ
s
0
VAN LANG UNIVERSITY DENTEMA


s
SK
kSXSS
S




0
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Substrate mass balance
S
SKSS
kS
SKSS
X
m
SS





1
1
00
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Determine model kinetic coefficient
kS
SK
S
S
X
S
K
kSXSS
S







0


VAN LANG UNIVERSITY DENTEMA
kS
S
S
S

S
1
k
1
4
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITHOUT RECYCLEWITHOUT RECYCLE
Dt i Y dk
fdlifth
VAN LANG UNIVERSITY DENTEMA
D
e
t
erm
i
ne
Y
an
d

k
d
f
rom mo
d
e
li
ng o
f


k
d
X
SS
o



tg
VAN LANG UNIVERSITY DENTEMA
Y
1

1
ASSIGNMENT 3ASSIGNMENT 3
No.
S
o
(mg/L) S
(mg/L)

(ngày) X (mg
VSS/L)
1 2000 250 0.4 800
2 2000 200 0.4 1000
VAN LANG UNIVERSITY DENTEMA
Determine k and K
s
3 2000 160 0.4 1300
4 2000 120 0.4 1600

rWee
c
X
Q
X
Q


XQXQ
VX
Wee
c



COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
In case of no return sludge In case of no return sludge
VAN LANG UNIVERSITY DENTEMA
SRT = HRTSRT = HRT
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Biomass mass balance
Accumulation = inflow – outflow + net growth
Symbolic representation
VAN LANG UNIVERSITY DENTEMA

V
rXQXQQQXV
dt

Assumed X
o
~ 0
(Q – Q
W
)X
e
+ Q
w
X
R
= r
g
V
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Biomass mass balance
(Q – Q
W
)X
e
+ Q
w
X
R
= r
g
V
S
VAN LANG UNIVERSITY DENTEMA

SK
S
VX
XQXQ





VAN LANG UNIVERSITY DENTEMA
d
S
m
c
k
SK
S





1




1
1
1

dt
dS

0
.


su
rVSSQV
dt
dS

0

COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Substrate mass balance
VrQSQSV
dt
dS
suo

VAN LANG UNIVERSITY DENTEMA
dt
At steady state dS/dt = 0

















S
K
kXS
Q
V
SS
o
VAN LANG UNIVERSITY DENTEMA





S
K
Q
s
SK
kSX


1
VAN LANG UNIVERSITY DENTEMA

cd
c
k
SSY
X





1
0








S
S
Y
k
S
S

ki
ne
ti
c coe
ffi
c
i
en
t
s
f
rom
modeling of the complete-mix reactor
with recycle
7
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE

cd
c
k
SSY
X





1
0

1
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Design and operating parameters
Food to microorganism (F/M) ratio
iQS
VAN LANG UNIVERSITY DENTEMA
Total appl
i
ed substrate rate
QS
o
F/M = =
Total microbial biomass VX
F/M = food to biomass ratio, g BOD or bsCOD/g VSS.d
Q = influent wastewater flow-rate, m
3
/d
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Design and operating parameters
Organic volumetric loading rate
QS
VAN LANG UNIVERSITY DENTEMA
kggV
QS
L
o
org
/10

= oxygen required, kg/d
P
x,bio
= biomass as VSS wasted per day, kg/d
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Mixed liquor solids concentration and solids production
SRT
VX
P
T
VSSX
T

,
VAN LANG UNIVERSITY DENTEMA
SRT
P
XT, VSS
= total solids wastes daily, g VSS/d
X
T
= total MLVSS concentration in aeration tank, g VSS/
m
V = volume of rector, m
3
SRT = solid retention time, d
8
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE

QXV
dt
dX
ix
i
io
i
,,







X
o,i
= nbVSS concentration in influent, g/m
3
X
i
= nbVSS concentration in aeration tank, g/m
3
r
X,i
= rate of nbVSS production from cell debris, g/m
3
.d
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE

QX
iX
i
io ,,
0 
SRTXkf
SRT
XX
ddioi


,
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Mixed liquor solids concentration
X
T
= X + X
i


SRTX
SRT
X
k
f
SSYSRT
X
io
o

Cell
debris
nbVSS
inf
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Solid production


SRT
X
S
S
Y
SRT

SRT
VX
P
T
VSSX
T

,
VAN LANG UNIVERSITY DENTEMA



SRT
X





COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Solid production


iodd
d
o
VSSX
QXXVkf
SRTk
SSQY
P
,,
1










VAN LANG UNIVERSITY DENTEMA

d
odd
d
o
VSSX
QX
SRTk
SRTSSYQkf
SRTk
SSQY
P
,,
11







Heterotrophic
biomass
Cell
debris
nbVSS
inf
9
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Solid production


debris
n
bVSS
inf
AB
C

ooTSSX
VSSTSSQC
BA
P 
85.085.0
,
net waste activated sludge produced each day, measured in terms of TSS, kg/d
COMPLETECOMPLETE MIX REACTOR MIX REACTOR
WITH RECYCLEWITH RECYCLE
Solid production
Mass of MLVSS = XMass of MLVSS = X
VSSVSS
.V = P.V = P
X,VSSX,VSS
.SRT .SRT
VAN LANG UNIVERSITY DENTEMA
Mass of MLSS = XMass of MLSS = X
TSSTSS
.V = P.V = P
X,TSSX,TSS
.SRT .SRT
COMPLETECOMPLETE MIX REACTOR MIX REACTOR

SRTk
SRTYkf
SRTk
Y
Y
o
io
d
dd
d
obs







,
11
Y
obs
= g VSS/g substrate removed
Assignment 4
S
0
(mg COD/L)
S (mg COD/L) X (mg VSS/L)
400 50 1000
800 80 1500