| > :@> & = PROCESS DESCRIPTION Nitrate feed fd Return activated sludge Effluent e Most common process used _siudge @®BOD,,, provide electron donor LL» Substrate de
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VAN LANG UNIVERSITY PARTMENT OF ENVIRONMENTAL TECHNOLOGY AND
MANAGEMENT
br CIALIZED ENGLISH-SEMESTER 5
Chapter 29 FUNDAMENTALS OF BIOLOGICAL
: ® Biological denitrification
F PROCESS DESCRIPTION
`
Âm transformations in biological treatment processes
mI]
Return activated sludge
® Electron donor is from endogenowgjdecay
@ Postanoxic denitrification
@ Much slower rate than preanoxic process
e Add exogenous carbon source: CH,0H _
q -
@ Process description
® Microbiology
® Stoichiometry of biological nitrification
@ Environmental factors
1 | >
:@>
& = PROCESS DESCRIPTION
Nitrate feed
fd
Return activated sludge
Effluent
e Most common process used _siudge
@®BOD,,, provide electron donor
LL» Substrate denitrification
o substrate _— (oreanoxic denitrificatiom=
—-
` MOCROBIOLOGY
Heterotrophic bacteria Achromobacter, Acinetobacter, Agrobacterium, Alcaligenes, Arthrobacter, Bacillus,
Chromobacterium, Corynebacterium, Flavobacterium, Hypomicrobium, Moraxella,
Neisseria, Paracoccus, Propionibacterium,
Pseudomonas, Rhizobium,Rhodopseudomonas, Spirillum, and Vibrio
Autotrophic bacteria
1 ty |
Nitrosomonas ropes , 4
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4 ` MOCROBIOLOGY
Pseudomonas
4 ` MOCROBIOLOGY
Rhizobium
» ‘STOICHIOMETRY OF BIOLOGICAL
DENITRIFICATION
C 19H, 50;N + 10NO, > 5N; + 10CO; + 3H;O + NH; + 100H
Organic materials
5CH,OH + 6 NO, > 3N, +5 CO, +7H,0 + 6 OH
Metanol
5CH,COOH + 8NO; > 4N; + 10CO, + 6H,O + 80H:
Acetate
IÍÏ©Erarrval
4 ` MOCROBIOLOGY
Agrobacterium
» STOICHIOMETRY OF BIOLOGICAL
DENITRIFICATION Several steps in nitrate reduction reactions NO; >NO, > NO>N,O DN,
bsCOD, ‹
methanol or acetate
aa
$ = GROWTH KINETICS
H,, = specific growth rate of nitrifying bacteria, g new cells/g cells.d
Lam = Maximum specific growth rate of nitrifying bacteria,
g new cells/g cells.d
N =nitrogen concentration, g/m?
k, =half-velocity constant, substrate concentration at one-half
the maximum specific substrate utilization rate, g/m?
k,, = endogenous decay coefficient for nitrifying organisms,
g VSS/g VSS.d
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:@
4 ` GROWTH KINETICS
n= fraction of denitrifying bacteria in the
biomass, g VSS/gVSS
7 = 0.20 to 0.80 for preanoxic denitrification
E ENVIRONMENTAL FACTORS
$ "`
® Less concern about pH influence
@ pH, = 7.0-8.0
e pH decrease from 7.0 to 6.0 > decrease rate
'@
aà»
q RBCs for denitrification is similar to that for
aerobic processes except the medium is totally
submerged to avoid oxygenating the liquid
HE GROWTH KINETICS
Effect of DO
K,’ = DO inhibition coefficient for nitrate reduction, mg/L
Kg xo3 = half velocity coefficient for nitrate limited reaction, mg/L
k `
`= 3 CS
bs )
-
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fl
ne
J
md
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ee
Fluid mechanism in Fluidized
Bed Reactor
Fluidized Bed