Nitrification
Symbol
Unit
Value at 20'C Value at lO'C
Stoichiometric parameters
Y A
g cell COD formed (g N oxidizedr 1
0.24
0.24
YH
g cell COD formed (g COD oxidizedr 1
0.67
0.67
fr
dimensionless
0.08
0.08
ixB
g N (CoDr 1 in biomass
0.086
0.086
iXE
g N (CODr 1 in endogenous mass
0.06
0.06
Kinetic parameters
~H
day- 1
6.0
3.0
Ks
gCOD m- 3
20.0
20.0
Ko,H
g02 m- 3
0.20
0.20
KNo
g N03-N m - 3
050
0.50
bH
day- 1
0.62
0.20
T]g
dimensionless
0.8
0.8
T]h
0.4
0.4
kh
g slowly biodegradable COD (g cell COD · dayr 1
3.0
1.0
Kx
g slowly biodegradable COD (g cell CODr 1
003
O.Dl
~A
day- 1
0.80
0.3
KNH
g NH3-N m - 3
1.0
1.0
Ko,A
g 02-N m- 3
0.4
0.4
k,
m 3 · COD (g · dayr 1
0.08
0.04
Table3.7
Set of reaction rate constantx and stoichiometric coefficients and their temperature dependency /9 I.
(fp ~ fJ, ixs ~ fs,N, ixE ~ fJ,N , ~H ~ ~max)
The process for the ammonium oxidizing bacteria is
+ 3
+
NH4 + 2 02 --. N02 + H20 + 2H
(3.22)
~G 0 (W) = -270 kJ/mol NH;l:-N
The process for the nitrite oxidizing bacteria is
{3.23)
~G 0 (W) = -80 kJ I mol N02-N
The nitrifying bacteria are a homogenous group of bacteria, characterized for
example by a low growth rate. This is due to the low energy yield which is linked
to the oxidation of ammonium and nitrite, respectively. The slow growth is a major
problem for the nitrification in biological treatment plants.
76