Biomedical Engineering Reference
In-Depth Information
3.4. Modeling of Uncoupled Energy Metabolism
To date, several models have been developed to evaluate the yield of activated sludge
under uncoupling conditions. Liu [82] developed a growth yield model to describe the effect
of the substrate concentration normalized to the biomass concentration (S
0
/X
0
) on the
observed growth yield in a substrate-sufficient batch culture of activated sludge:
1
1
1
S
X
=
+
0
0
(2)
Y
(
Y
)
(
Y
)
S
/
X
+
K
obs
obs
max
w
min
0
0
S
X
Where (Y
obs
)
max
is the maximum observed growth yield under substrate-limited conditions;
(Y
w
)
min
is the minimal energy spilling-related growth yield; S
0
and X
0
are initial substrate
concentration and initial biomass concentration, respectively; K
S/X
is the S
0
/X
0
ratio-related
saturation constant.
According to the point of view of energy uncoupling, Liu [83] extended the above
equation to a general expression :
1
1
1
C
X
=
+
u
0
Y
(
Y
)
(
Y
)
C
/
X
+
K
obs
obs
max
w
min
u
0
u
X
(3)
where C
u
is initial uncoupler concentration in the culture medium; K
u/X
is a C
u
/X
0
-related
contant.
Based on growth yield, Liu et al. [84] put forward the concept of energy uncoupling
coefficient to describe the observed uncoupling between anabolism and catabolism:
(
Y
)
−
Y
E
=
obs
max
)
obs
u
(
Y
obs
max
(4)
where E
u
is the energy uncoupling coefficient.
In the study of Chen et al. [85], a model was developed to evaluate the yield of activated
sludge in the presence of 2,4-dinitrophenol (DNP):
1
1
k
=
+
d
⋅
θ
(5)
Y
Y
'
Y
'
obs
max
max
where Y'
max
is the maximum observed sludge yield with a consideration of energy
requirement maintenance; K
d
is specific endogenous respiration rate and θ is SRT.
Chen et al. [80] also analyzed the energy uncoupling and inhibition at the presence of
DCP. In regard to energy uncoupling, the difference in the observed growth yield between the
DCP-free culture and that dosed with DCP could represent the degree of metabolism
uncoupling and be expressed using Equation 4. From the aspect of inhibition, they
modified
Monod model as the follows:
