Bài giảng công nghệ môi trường_29 ppt

1
SPECIALIZED ENGLISH-SEMESTER 5
VAN LANG UNIVERSITY
DEPARTMENT OF ENVIRONMENTAL TECHNOLOGY AND
MANAGEMENT
Chapter 29Chapter 29
FUNDAMENTALS OF BIOLOGICAL FUNDAMENTALS OF BIOLOGICAL
Dr. Tran Thi My Dieu
Sep. 2011
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WASTEWATER TREATMENTWASTEWATER TREATMENT
Biological denitrificationBiological denitrification
CONTENTSCONTENTS
Process descriptionProcess description
MicrobiologyMicrobiology
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Stoichiometry of biological nitrificationStoichiometry of biological nitrification
Environmental factorsEnvironmental factors
PROCESS DESCRIPTIONPROCESS DESCRIPTION
Nitrogen transformations in biological treatment processes
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PROCESS DESCRIPTIONPROCESS DESCRIPTION
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(a) substrate driven (preanoxic denitrification)
Substrate denitrification
Most common process used
BOD
inf
provide electron donor
PROCESS DESCRIPTIONPROCESS DESCRIPTION
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(b) endogenous driven (postanoxic denitrification)
Electron donor is from endogenous decay
Postanoxic denitrification
Much slower rate than preanoxic process
Add exogenous carbon source: CH
3
OH
MOCROBIOLOGYMOCROBIOLOGY
Heterotrophic bacteria
Achromobacter, Acinetobacter, Agrobacterium,
Alcaligenes, Arthrobacter, Bacillus,
Chromobacterium, Corynebacterium,
Fl b t i H i bi M ll
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Fl
avo
b
ac
t
er
i
um,
Hyp
om
i
cro
bi
um,
M
oraxe

ll
a,
Neisseria, Paracoccus, Propionibacterium,
Pseudomonas, Rhizobium,Rhodopseudomonas,
Spirillum, and Vibrio
Autotrophic bacteria
Nitrosomonas europaea
2
MOCROBIOLOGYMOCROBIOLOGY
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Pseudomonas Pseudomonas
MOCROBIOLOGYMOCROBIOLOGY
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Agrobacterium
MOCROBIOLOGYMOCROBIOLOGY
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Rhizobium
STOICHIOMETRY OF BIOLOGICAL STOICHIOMETRY OF BIOLOGICAL
DENITRIFICATIONDENITRIFICATION
NONO
33

NONO
22

 NO NO  NN
22
O O  NN
22
Several steps in nitrate reduction reactions

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Clarifier
Electron donor
bsCOD
inf
bsCOD
decay
methanol or acetate
STOICHIOMETRY OF BIOLOGICAL STOICHIOMETRY OF BIOLOGICAL
DENITRIFICATIONDENITRIFICATION
C
10
H
19
O
3
N + 10NO
3
-
 5N
2
+ 10CO
2
+ 3H
2
O + NH
3
+ 10O
H
Organic materials


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Clarifier
5CH
3
OH + 6 NO
3
-

3N
2
+ 5 CO
2
+ 7 H
2
O + 6 OH
-
5CH
3
COOH + 8NO
3
-
 4N
2
+ 10CO
2
+ 6H
2
O + 8OH
-

Metanol
Acetate
GROWTH KINETICSGROWTH KINETICS
dn
n
nm
n
k
NK
N














n
= specific growth rate of nitrifying bacteria, g new cells/g cells.d
VAN LANG UNIVERSITY DENTEMA
Clarifier

nm

= maximum specific growth rate of nitrifying bacteria,
g new cells/g cells.d
N = nitrogen concentration, g/m
3
k
n
= half-velocity constant, substrate concentration at one-half
the maximum specific substrate utilization rate, g/m
3
k
dn
= endogenous decay coefficient for nitrifying organisms,
g VSS/g VSS.d
3
GROWTH KINETICSGROWTH KINETICS
SK
kXS
r
S
su



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= fraction of denitrif
y
in
g
bacteria in the
biomass, g VSS/gVSS

 = 0.20 to 0.80 for preanoxic denitrification
GROWTH KINETICSGROWTH KINETICS































DOK
K
NOK
NO
SK
kXS
r
o
o
NOSS
su
'
'
3,
3
3
Effect of DOEffect of DO
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

3
K
o
’ = DO inhibition coefficient for nitrate reduction, mg/L
K
S,NO3
= half velocity coefficient for nitrate limited reaction, mg/L
ENVIRONMENTAL FACTORSENVIRONMENTAL FACTORS

Less concern about pH influence
pH
opt
= 7.0-8.0
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pH decrease from 7.0 to 6.0  decrease rate
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Fluid mechanism in Fluidized
Bed Reactor
Fluidized Bed Reactorn used
for denitrification
RBCs for denitrification is similar to that for
aerobic processes except the medium is totally
submerged to avoid oxygenating the liquid
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