PII: S0043-1354(00)00105-6
Wat. Res. Vol. 34, No. 14, pp. 3580±3590, 2000
7 2000 Elsevier Science Ltd. All rights reserved
Printed in Great Britain
0043-1354/00/$ - see front matter
www.elsevier.com/locate/watres
CALIBRATION AND VALIDATION OF ACTIVATED
SLUDGE MODEL NO. 3 FOR SWISS MUNICIPAL
WASTEWATER
G. KOCHM, M. KUÈHNI, W. GUJERM and H. SIEGRIST*M
Swiss Federal Institute for Environmental Science and Technology (EAWAG) and Swiss Federal
Institute of Technology (ETH), CH-8600, DuÈbendorf, Switzerland
(First received 13 September 1999; accepted in revised form 14 December 1999)
AbstractÐASM3 was tested against experimental data from aerobic and anoxic batches as well as fullscale experiments from various WWTPs treating Swiss municipal wastewater. A set of kinetic and
stoichiometric parameters emerged from these tests. The calibrated ASM3 allows the sludge production
and the denitri®cation capacity to be successfully modeled with a standardized set of parameters. The
readily degradable inlet substrate SS,o was estimated from respiration measurements by curve ®tting.
This contradicts the suggestion of the IAWQ task group that SS,o in ASM3 may be approximated by
the total soluble COD as determined by 0.45 mm membrane ®ltration. Aerobic and anoxic respiration
of storage products is insigni®cant compared to growth on these products. 7 2000 Elsevier Science
Ltd. All rights reserved
Key wordsÐActivated Sludge Model No. 3, ASM3, kinetics, stoichiometrics, full-scale experiments,
batch experiments
NOMENCLATURE
A
C
H
I
o
ir
ini
NH
NO
O, O2
r
S
STO
X
autotrophic organisms
component with soluble and particulate fractions
heterotrophic organisms
inert organic material
input
internal recirculation
initial condition
ammonium nitrogen
nitrate+nitrate nitrogen, anoxic
oxygen, aerobic
return sludge
organic substrate, soluble component
cell internal storage product
particulate component
INTRODUCTION
Thanks to today's better scienti®c insights into the
biological processes of wastewater treatment, the
IAWQ Task Group on Mathematical Modeling for
Design and Operation of Biological Wastewater
Treatment Processes was able to introduce Activated Sludge Model No. 3 (ASM3) (Gujer et al.,
*Author to whom all correspondence should be addressed.
Tel.: +41-1-823-5054; fax: +41-1-823-5389; e-mail:
[email protected]
1999). ASM3 corrects some de®ciencies of ASM1
(Henze et al., 1987). It includes the storage of organic substrates as a new process and lysis is
replaced by an endogenous respiration process. As
a result, the hydrolysis becomes less dominant for
the rates of oxygen consumption and denitri®cation
compared to the ASM1 and is now independent of
the electron donor. Furthermore, all processes
(except for hydrolysis) run at a reduced rate under
anoxic as compared to aerobic conditions. The
ASM3 also takes smaller anoxic yield coecients
into account.
A set of kinetic and stoichiometric parameters for
the reliable prediction of the nitri®cation and denitri®cation rates in wastewater treatment plants
(WWTPs) treating Swiss municipal diluted waste
water is proposed in this paper. The most important parameters of ASM3 are ®rst estimated on the
basis of batch experiments with activated sludge
from di€erent WWTPs. For the parameter estimation and the sensitivity analysis, ASM3 was
implemented in AQUASIM (Reichert, 1998). Sensitivity analysis are necessary to check, which model
parameter can be determined with the aid of the
available batch experiments. Based on the multitude
of experiments with di€erent carbon sources (single
substrate and mixed substrate), di€erent electron
acceptors (nitrate and oxygen) and di€erent time
constants (long term and short term experiments),
the most important model parameters could be esti-
3580
Calibration and validation of ASM No. 3
mated. The uncertainty of parameter estimation is
reduced by simultaneously evaluating all the experiments. With multiple experiments at di€erent temperatures or with activated sludge from di€erent
plants the uncertainty could be further reduced.
Nevertheless, it is very likely that the same dynamic
behavior can be used to explain several parameter
combinations. It should be considered that in this
paper only a possible way to calibrate ASM3 is
suggested and that the experiments were initially
designed to calibrate ASM1 and not ASM3.
Further experiments will have to be performed in
future, speci®cally for calibrating ASM3 more accurately (e.g. heterotrophic storage of organic substrate).
ASM3 was then validated for the heterotrophic
processes with a wide variety of experimental data
from pilot- and full-scale experiments. The experiments were used to calibrate the nitri®cation rates
and the sludge production. For these parameters a
real validation was not possible. The initial sludge
composition of all the batch experiments (the heterotrophic biomass XH,ini, the storage products
XSTO,ini and the slowly degradable substrate XS,ini)
was simultaneously estimated from the simulations
of the full-scale experiments.
CALIBRATION OF ASM3 WITH BATCH EXPERIMENTS
Endogenous respiration under aerobic and anoxic
conditions
Batch experiments with sludge from the TuÈffenwies pilot plant (Fig. 6) showed a considerably
reduced decay rate of the autotrophic and heterotrophic organisms under anoxic compared to
aerobic conditions (Siegrist et al., 1999). This e€ect
can be reproduced in ASM3 by taking into account
an aerobic and a slower anoxic endogenous respiration rate for the biomass XH and XA. The decay
rates bH,O2 and bH,NO for the heterotrophic biomass
at 208C (Table 3) were estimated with AQUASIM
from the decrease of the total COD at 14 and 208C,
3581
respectively (Fig. 1). The sensitivity analysis shows
that both, the decay rate bH and the initial sludge
composition XH,ini, are sensitive in these experiments and strongly correlated with each other.
Therefore XH,ini was estimated simultaneously from
pilot plant steady state simulation. The determined
decay rates bH,O2 and bH,NO for the heterotrophic
biomass at 208C were 0.30 and 0.10 dÿ1, respectively. From the decrease of the maximal autotrophic respiration rate also bA,O2 and bA,NO for the
autotrophic biomass at 208C were estimated to 0.20
and 0.10 dÿ1, respectively (Siegrist et al., 1999).
Sensitivity analysis with both batch and pilot-scale
experiments showed, that the respiration rate bSTO
for the internal storage products is insigni®cant
compared to growth on these products and could
not be estimated from the batch tests. Therefore,
bSTO was set equal to the endogenous respiration
rate analogous to the original ASM3.
Aerobic degradation of acetate
A tailing-o€ of the oxygen-consumption curve is
often observed in respiration tests (Fig. 2). This
phenomenon can be modeled with the storage products XSTO introduced in ASM3. A set of stoichiometric and kinetic parameters for the aerobic
storage and growth of the heterotrophic biomass
XH could be estimated (Fig. 2) on the basis of
aerobic batch experiments with activated sludge
from the ZuÈrich±Glatt WWTP (Siegrist et al., 1995)
and acetate as the substrate. The parameters
YSTO,O2 and kSTO are most sensitive after acetate
addition during substrate respiration and could be
uniquely determined based on the oxygen consumption curve (Fig. 2). Before and after substrate respiration mainly YH,O2, KSTO and mH are sensitive.
The saturation constant KS could be determined
during the sudden decrease of the oxygen consumptive rate. The initial sludge composition results
from the steady state WWTP simulation. For both
experiments, the net (true) yield of heterotrophic
biomass produced per unit of substrate removed
results
in
Ynet; O2 ˆ YSTO; O2 YH; O2 ˆ
Fig. 1. Decrease of activated sludge COD from the TuȀenwies pilot plant in anoxic and aerobic batch
experiments. CCOD,ini=3500 gCOD mÿ3, XH,ini=1200 gCOD mÿ3. Best ®t with bH,O2=0.30 dÿ1,
bH,NO=0.10 dÿ1, yT=0.078Cÿ1 (values at T = 208C).
3582
G. Koch et al.
Fig. 2. Heterotrophic oxygen-consumption rate in batch experiments (T = 158C) from 27 November
1992 (left) and 8 December 1992 (right). Acetate addition at 0.053 and 0.081 d, XH,ini=1300 and 1100
gCOD mÿ3, respectively. Sludge from the ZuÈrich±Glatt WWTP, pre-aerated for several hours. Best ®t
for both experiments with YH,O2=0.80 gXH gÿ1XSTO, YSTO,O2=0.72 gXSTO gÿ1SS, KS=4.0 gCOD mÿ3,
mH=3.0 dÿ1, KSTO=0.1 gXH gÿ1XSTO and kSTO=5.0 dÿ1 (values at T = 208C).
0:72 0:80 ˆ 0:58gXH g ÿ1 SS , which is about 8%
higher than the value suggested by Gujer et al.
(1999) (Table 3).
Aerobic degradation of soluble COD from primary
sludge acidi®cation
The characteristic of the oxygen-consumptive
curve depends strongly on the available substrate.
An aerobic batch experiment with activated sludge
from the Neugut±DuÈbendorf WWTP (Fig. 9) and
soluble COD from primary sludge acidi®cation as
the substrate (Moser-Engeler et al., 1999) was therefore performed (Fig. 3) and con®rmed twice by
identical experiments. The net yield from the readily
degradable fraction of the total soluble COD
Ynet; O2 ˆ YSTO; O2 YH; O2 ˆ 0:80 0:80 ˆ
0:64gXH g ÿ1 SS is considerably higher than that
observed from the acetate batch and suggested by
Gujer et al. (1999) (Table 3). To obtain a good ®t
Fig. 3. Heterotrophic oxygen-consumption rate in the
batch experiment from 19 December 1996. Substrate addition at 0.042 d, XH,ini=880 gCOD mÿ3. T = 108C.
Sludge from the aerobic compartment of the Neugut±
DuÈbendorf WWTP. Best ®t with YH,O2=0.80 gXH
gÿ1XSTO, YSTO,O2=0.80 gXSTO gÿ1SS, KS=10 gCOD mÿ3,
mH=3.0 dÿ1, KSTO=0.1 gXH gÿ1XSTO and kSTO=11 dÿ1
(values at T = 208C). Some 80% of the soluble COD were
volatile fatty acids.
of measured data, the aerobic storage rate constant
kSTO has to be increased by about 100%. The maximum oxygen-consumption rate based on dissolved
fermentation products is obviously much higher
than that based on single-substrate acetate. This observation is in agreement with the measurements of
maximum denitri®cation rates on di€erent single
substrates and mixed fermentation products
(Moser-Engeler et al., 1998). Because of the wide
variety of substrates in the fermentation products
and their individual uptake rates, the saturation
constant for substrate SS is greater than that for the
single-substrate acetate. It is assumed that fermentation products tend to induce oxygen-consumption
curves which are more similar to wastewater than
to acetate as a single substrate.
Aerobic degradation of COD from wastewater
The aerobic yield coecients for storage and
growth as well as the high aerobic storage-rate constant kSTO calculated from the batch with fermentation products was con®rmed by 14 analyzed
respiration curves with sludge and wastewater from
the TuȀenwies pilot plant (eight batch experiments,
two of them shown in Fig. 4) and the Neugut±
DuÈbendorf WWTP (six batch experiments). In contrast to the original ASM3 (Gujer et al., 1999)
where the readily degradable inlet substrate SS,o
may be approximated by the total soluble inlet
COD SCOD,o as determined by 0.45-mm membrane
®ltration, the SS,o was estimated from respiration
measurements by curve ®tting (all estimated SS,o
and measured SCOD,o are summarized in Table 1).
Otherwise, completely di€erent aerobic yields for
the municipal wastewater components (mainly colloidal rather than soluble degradable COD) and
di€erent fermentation products (mainly fatty acids)
as the substrate are required. The level of the basic
respiration (respiration after consumption of readily
degradable substrate) could only be modeled by a
Calibration and validation of ASM No. 3
3583
Fig. 4. Typical heterotrophic oxygen-consumption rates for diluted (SS,o=30 gCOD mÿ3, left) and concentrated (SS,o=75 gCOD mÿ3, right) un®ltered wastewater. Measurements from 20 November 1996.
The ratio of sludge to wastewater volume in the batch reactor was 1:3 (left) and 1:4 (right), respectively. T = 158C. Activated sludge from the TuȀenwies pilot plant. Best ®t for eight experiments in total
with YH,O2=0.80 gXH gÿ1XSTO, YSTO,O2=0.80 gXSTO gÿ1SS, KS=10 gCOD mÿ3, mH=3.0 dÿ1,
KSTO=0.1 gXH gÿ1XSTO, kSTO=13 dÿ1 and kH=9.0 dÿ1 (values at T = 208C).
substantial increase of the hydrolysis rate constant
kH .
Anoxic degradation of soluble COD from primary
sludge acidi®cation
To quantify the reduction of the anoxic yield and
the reduction factor for storage and growth, an
anoxic batch experiment with activated sludge from
the Neugut-DuÈbendorf WWTP and soluble COD
from primary sludge acidi®cation as the substrate
was analyzed (Fig. 5). From parameter identi®cation with AQUASIM, an anoxic net yield of
Ynet; NO ˆ YSTO; NO YH; NO ˆ 0:70 0:65 ˆ
0:46 gXH g ÿ1 SS was estimated, which is about 30%
lower than the net aerobic yield. On the basis of
thermodynamic calculations, a 15% lower net yield
can be predicted (Maurer and Gujer, 1998; Orhon
et al., 1996). Copp and Dold (1998) determined an
average reduction in net yield of about 38% from
batch experiments with di€erent organic substrates
and biomasses. McClintock et al. (1988) and
Purtschert and Gujer (1999) observed a reduction
of 45 and 25%, respectively, which clearly also con®rms the signi®cant reduction of the anoxic compared with the aerobic yield. The calibrated
reduction factor for storage and growth ZNO ˆ 0:50
is slightly lower than that suggested by Gujer et al.
(1999). The saturation constant KS for the fermentation products as the substrate was found to be
identical under aerobic and anoxic conditions (compare the calibrated parameters in Fig. 3 and Fig. 5).
VALIDATION OF ASM3 WITH PILOT AND FULL-SCALE
EXPERIMENTS
ASM3 is validated with a number of pilot- and
full-scale experiments on the basis of the kinetic
and stoichiometric parameters determined from
batch experiments (Table 3). The sludge production
in the various WWTPs is calibrated with the fraction of inert particulate COD XI,o from the waste-
Table 1. Wastewater characterization based on 14 respiration experiments with sludge and wastewater from the TuȀenwies pilot plant
and the Neugut±DuÈbendorf WWTPa
WWTP
TuȀenwies pilot plant
TuȀenwies pilot plant
TuȀenwies pilot plant
TuȀenwies pilot plant
TuȀenwies pilot plant
TuȀenwies pilot plant
TuȀenwies pilot plant
TuȀenwies pilot plant
Neugut±DuÈbendorf
Neugut±DuÈbendorf
Neugut±DuÈbendorf
Neugut±DuÈbendorf
Neugut±DuÈbendorf
Neugut±DuÈbendorf
a
Experiment
T
(8C)
CCOD,o
(gCSB mÿ3)
SCOD,o
(gCSB mÿ3)
SI,o+SS,o
(gCSB mÿ3)
SI,o+SS,o/SCOD,o
29 October 1996, 10:00
29 October 1996, 13:30
30 October 1996, 10:00
30 October 1996, 13:30
19 November 1996, 10:00
19 November 1996, 14:30
20 November 1996, 10:00
20 November 1996, 13:30
28 February 1996, 16:00
3 August 1995, 11:00
4 August 1995, 03:00
4 August 1995, 10:00
18 July 1995, 11:00
21 July 1995, 09:00
16
16
16.5
16.5
14.5
15
15
15
13
20.5
20.5
20.5
19
19
390
400
390
565
330
435
345
545
480
315
140
520
280
350
170
190
170
190
140
210
135
195
250
185
65
205
±
120
25+15=40
25+35=60
25+40=65
35+55=90
20+30=50
25+70=95
20+30=50
35+75=110
30+160=190
20+85=105
10+35=45
30+35=65
15+70=85
20+60=80
0.24
0.32
0.38
0.47
0.36
0.45
0.37
0.56
0.76
0.57
0.69
0.32
±
0.67
CCOD,o=total COD inlet concentration (primary e‚uent), SCOD,o=total soluble COD inlet concentration determined by 0.45-mm membrane ®ltration, SS,o=readily degradable inlet substrate determined by curve ®tting, SI,o=inert soluble COD inlet concentration
(about 0.06CCOD,o, Table 4).
3584
G. Koch et al.
taken from di€erent zones of the pilot plant (Fig. 8).
The simulation with the calibrated ASM3 corresponds well to the measurements.
WWTP Neugut±DuÈbendorf
Fig. 5. Denitri®cation rate in the batch experiment from
12 December 1995. Substrate addition at 0.021 d,
XH,ini=700 gCOD mÿ3. T = 208C. Sludge from the
aerobic compartment of the Neugut±DuÈbendorf WWTP.
Best ®t with YH,NO=0.65 gXH gÿ1XSTO, YSTO,NO=
0.70 gXSTO gÿ1SS, KS=10 gCOD mÿ3, mH=3.0 dÿ1,
KSTO=0.1 gXH gÿ1XSTO, kSTO=11 dÿ1, ZNO=0.50 (values
at T = 208C).
water (Table 4), the observed nitri®cation rate with
the maximum autotrophic growth rate mA and the
saturation constant for ammonium KA,NH (Table 2).
TuȀenwies pilot plant
Tracer experiments showed that the ¯ow characteristic of the TuȀenwies pilot plant (total volume
of activated sludge tank 1.2 m3) can be simulated as
a cascade of eight CSTRs, corresponding to the six
anoxic and two aerobic compartments. The sludge
blanket was characterized with reactors R1 and
R10 (Fig. 6). Ammonium and nitrate were added to
the in¯uent to avoid nitrate limitation in the anoxic
compartments.
A maximum growth rate mA ˆ 1:8 d ÿ1 …T ˆ 20 ^ C†
and a saturation constant for ammonium KA, NH ˆ
1:0 gN m ÿ3 best ®ts the measured ammonium concentrations (Fig. 7) and oxygen-consumption rates
(results not shown) of the nitri®ers. The high mA is
probably due to the relatively high air ¯ow in the
pilot plant, leading to improved CO2 stripping and
increased pH. A good prediction of the nitrogen
elimination can be observed (Fig. 7).
Pro®les of the heterotrophic oxygen-consumption
could be determined with activated sludge samples
The experimental lane at the Neugut±DuÈbendorf
WWTP treats the wastewater for about 15,000
population equivalents (p.e.) and consists of six
reactor compartments (R2±R4 anoxic, R5±R7
aerobic, Fig. 9). The ¯ow regime of the activated
sludge tank behaves almost like a cascade of six
CSTRs. This could be concluded from tracer experiments. Besides the composite samples from the
in¯uent and e‚uent, the variation of the denitri®cation capacity within the tanks was also observed
with on-line nitrate, nitrite and ammonium equipment. To avoid nitrate limitation in the anoxic compartments and to simulate the e€ect of the
nitrogen-rich supernatant from the sludge digestion
that will be built on Neugut in future, nitrogen fertilizer with 25% NH4-N, 25% NO3-N and 50%
urea, respectively, was added to the in¯uent.
A substantial nitrite accumulation occurred in
compartment R6 due to the high temperatures prevailing during the investigated period (T = 20±
228C). On the basis of a nitrogen balance over the
anoxic zone (R1±R4), the fraction of the denitri®ed
nitrite bNO2 in the total denitri®cation capacity
(equation (1)) was about 20%. Due to the signi®cantly smaller COD equivalent of nitrite SNO2 compared to nitrate SNO3 …iCOD, NO2 ˆ ÿ3:43 and
iCOD; NO3 ˆ ÿ4:57 gCOD gN ÿ1 , respectively), the
denitri®cation potential increases. In ASM3, this
can be considered in conjunction with a reduced
COD equivalent iCOD, NO for nitrate plus nitrite
(SNO) within the composition matrix (equation (2)),
leading to increased stoichiometric coecients
nj,SNO and therefore to about 8% higher anoxic storage and growth rates.
bNO2 ˆ
Qo SNO2, o ‡ Qir SNO2, R6 ‡ Qr SNO2, R7
Qo SNO, o ‡ Qir SNO, R6 ‡ Qr SNO, R7
ˆ 0:20
…1†
Table 2. Maximum autotrophic growth rate (T = 208) and saturation constant for ammonium from pilot and full-scale experimentsa
WWTP
TuȀenwies pilot plant
Neugut±DuÈbendorf WWTP
Neugut±DuÈbendorf WWTP
ZuÈrich±WerdhoÈlzli WWTP
ZuÈrich±WerdhoÈlzli WWTP
ZuÈrich±WerdhoÈlzli WWTP
ZuÈrich±Glatt WWTP
a
Experiment
mA [dÿ1]
KA,NH [gN mÿ3]
Remarks
11±12 March 1997
26±27 August 1997
3±4 February 1998b
8 March 1998c
2 December 1993c
4±5 December 1996
9±10 November 1992
1.8
0.9
1.4
1.0
1.0
1.0
2.0
1.0
1.0
1.0
2.0
1.5
1.0
2.0
No chemical precipitation
No chemical precipitation
No chemical precipitation
Fe(II) addition in aerobic zone
Fe(II) addition in aerobic zone
Fe(II) addition in aerobic zone
Fe(II) addition in anoxic zone
bA,O2=0.20 dÿ1.
Experiments not shown.
c
Experiments discussed in Siegrist et al. (2000).
b
Calibration and validation of ASM No. 3
3585
Fig. 6. Flow scheme and operating conditions of the TuȀenwies pilot plant. The total sludge retention
time yX,tot (incl. R1 and R10) was 17 d. The oxygen concentration in the reactors R8 and R9 was controlled.
iCOD,
NO
ˆ bNO2 iCOD,
iCOD,
NO3
NO2
‡ …1 ÿ bNO2 †
‡ ÿ4:34‰gCOD gN
ÿ1
Š
…2†
With a maximum growth rate mA ˆ 0:9 d ÿ1 (T =
208C) and a saturation constant for ammonium
KA, NH ˆ 1:0 gN m ÿ3 , the modeled ammonium pro®le (Fig. 10) and autotrophic oxygen-consumption
rates (results not shown) ®t the measurements best.
With the kinetic and stoichiometric parameters calculated from the batch experiments, the heterotrophic oxygen-consumption rates (results not
shown) as well as the total denitri®cation rate
(Fig. 10) are slightly underestimated.
WWTP ZuÈrich±WerdhoÈlzli
The ZuÈrich±WerdhoÈlzli WWTP (600,000 p.e.) is
split up into two lanes, north and south. Both lanes
have six parallel activated-sludge tanks (6 5000 m3) and six rectangular clari®ers with transverse ¯ow. The activated sludge tanks have a 28%
anoxic volume (Fig. 11). The Kjeldahl-nitrogen
load of the digester supernatant is about 20% of
the load in the primary e‚uent.
Here, ASM3 was tested with three experiments (8
March 1988, before installation of anoxic zones; 2
December 1993; 4±5 December 1996) performed at
the ZuÈrich±WerdhoÈlzli WWTP with respect to process optimization in the water lane. The ¯ow
scheme and the simulation results with the calibrated ASM3 of the ®rst two experiments are discussed in Siegrist et al. (2000). Figure 12 shows the
simulation of the third experiment with the calibrated ASM3 (best reproduction of the nitri®cation
capacity with mA=1.0 dÿ1 and KA, NH ˆ
1:0 gN m ÿ3 at T = 208C). The measured and modeled denitri®cation rates correlate well without any
adjustments of the calibrated ASM3. The same experiment could also successfully be modeled with a
slightly modi®ed ASM1 (Koch et al., 1999).
WWTP ZuÈrich±Glatt
The activated sludge system of the WWTP ZuÈrich±Glatt (110,000 p.e.) consists of four parallel
lanes (4 1810 m3) and four circular secondary
Fig. 7. Modeled (lines) and measured (dots) ammonium (left) and nitrate+nitrite (right) concentrations
in R7 and in the e‚uent of the secondary clari®er on 11±12 March 1997. The average total COD and
ammonium inlet concentrations during the previous three weeks were 290 gCOD mÿ3 and 38 gN mÿ3
(ammonium dosage).
3586
G. Koch et al.
Fig. 8. Modeled and measured pro®les of the actual heterotrophic oxygen-consumption rate. The time axis corresponds to the hydraulic retention time of a sludge package
in the TuȀenwies pilot plant (space time).
clari®ers with central inlets. The experimental lane
had a 33% anoxic volume (Fig. 13, see also Siegrist
et al., 1995). The Kjeldahl-nitrogen load of the
reject water from digester supernatant is about 15%
of the load in the primary e‚uent.
With the set of parameters obtained from the
batch experiments, the modeled nitrate pro®les
reproduce the measurements well (Fig. 14). The
maximum growth rate of the nitri®es mA has to be
increased to 2.0 dÿ1 for a best ®t, which is substantially higher than generally assumed. The relatively
high estimated saturation constant for ammonium
KA, NH ˆ 2:0 gN m ÿ3 partly compensates the high
maximum growth rate.
Adjustment of ASM3 after the pilot and full-scale experiments
The calibrated ASM3, validated with pilot and
Fig. 9. Flow scheme and operating conditions of the Neugut DuÈbendorf WWTP (experimental lane).
The total sludge retention time yX,tot (including the sludge blanket R1) was 20 d. The oxygen concentration in the reactors R6 and R7 was controlled.
Fig. 10. Modeled and measured ammonium (left) and nitrate+nitrite (right) concentration in di€erent
reactors on 26±27 August 1997. The average total COD and ammonium inlet concentrations in the previous three weeks were 320 gCOD mÿ3 and 15.7 gN mÿ3 (without N-dosage) respectively. The strong
variation in nitrogen dosage in the previous week was considered in the simulation. T = 218C. See
Table 4 for the COD inlet fractions and Table 3 for the model parameters.
Calibration and validation of ASM No. 3
3587
Table 3. Calibrated kinetic and stoichiometric parameters at T = 208 with exponential temperature dependence yT in parentheses
Symbol
Kinetic parameters
Hydrolysis rate constant
Hydrolysis saturation constant
Heterotrophic organisms XH
Aerobic storage rate constant
Anoxic reduction factor for growth/storage
Saturation/inhibition constant for oxygen SO
Saturation/inhibition constant for SNO
Saturation constant for substrate SS
Saturation constant for storage
Heterotrophic maximum aerobic growth rate
Saturation constant for ammonium SNH
Saturation constant for bicarbonate SHCO
Aerobic endogenous respiration rate of XH
Anoxic endogenous respiration rate of XH
(from batch and full-scale experiments respectively)
Aerobic respiration rate for XSTO
Anoxic respiration rate for XSTO
Autotrophic organisms (nitri®ers) XA
Autotrophic maximum growth rate
Ammonium substrate saturation constant for nitri®ers
Oxygen substrate saturation constant for nitri®ers
Bicarbonate saturation constant for nitri®ers
Aerobic endogenous respiration of nitri®ers
Anoxic endogenous respiration of nitri®ers
Stoichiometric parameters
Production of XI in endogenous biomass respiration
Aerobic yield of stored products per SS
Anoxic yield of stored products per SS
Aerobic yield of heterotrophic biomass growth on XSTO
Anoxic yield of heterotrophic biomass growth on XSTO
Yield of autotrophic biomass per g NO3-N
Nitrogen content of SI
Nitrogen content of SS
Nitrogen content of XI
Nitrogen content of XS
Nitrogen content of XH and XA
Unit
ASM3
(Gujer et al., 1999)
Calculated values
kH
KX
dÿ1
gXSgÿ1XH
3.0 (0.04)
1.0
kSTO
ZNO
KO
KNO
KS
KSTO
mH
KNH
KHCO
bH,O2
bH,NO
gSS gÿ1XH dÿ1
±
gO2 mÿ3
gN mÿ3
gCOD mÿ3
gXSTO gÿ1XH
dÿ1
gN mÿ3
mol mÿ3
dÿ1
dÿ1
5.0 (0.07)
0.6
0.2
0.5
2.0
1.0
2.0 (0.07)
0.01
0.1
0.2 (0.07)
0.10 (0.07)
bSTO,O2
bSTO,NO
dÿ1
dÿ1
0.2
0.1
0.3a
0.15a
mA
KA,NH
KA,O
KA,HCO
bA,O2
bA,NO
dÿ1
gN mÿ3
gO2 mÿ3
mol mÿ3
dÿ1
±
1.0 (0.105)
1.0
0.5
0.5
0.15 (0.105)
0.05 (0.105)
1.320.4 (0.105)
1.420.5
0.5
0.5
0.20 (0.105)
0.10 (0.105)
fXI
YSTO,O2
YSTO,NO
YH,O2
YH,NO
YA
iNSI
iNSS
iNXI
iNXS
iNBM
gXI gÿ1XH
gXSTO gÿ1SS
gXSTO gÿ1SS
gXH gÿ1XSTO
gXH gÿ1XSTO
gCOD gNÿ1
gN gCODÿ1
gN gCODÿ1
gN gCODÿ1
gN gCODÿ1
gN gCODÿ1
0.20
0.85
0.80
0.63
0.54
0.24
0.01
0.03
0.02
0.04
0.07
0.20
0.80
0.70
0.80
0.65
0.24
0.01
0.03
0.04
0.03
0.07
9.0 (0.04)
1.0
12 (0.07)
0.5
0.2
0.5
10
0.10
3.0 (0.07)
0.01
0.1
0.3 (0.07)
0.10 and 0.15 (0.07)
a
bSTO could not be calibrated with the experiments and is not sensitive to the change in respiration rates. Analogous to the original
ASM3 (Gujer et al., 1999). bSTO was set equal to the endogenous respiration rate bH.
full-scale experiments, reproduces the observed
nitrate+nitrite pro®les quite well. Nevertheless, the
denitri®cation capacity is systematically underestimated in all the experiments. From a sensitivity
analysis with AQUASIM (Reichert, 1998) performed with the TuȀenwies experiment from 11±12
March 1997 after model calibration, the most sensitive parameters with respect to the concentrations
SNH and SNO in the di€erent tanks could be estimated. The parameters most sensitive to the change
in denitri®cation capacity are the anoxic yields
(YSTO,NO, YH,NO), the inlet substrates XS,o and SS,o
and the endogenous respiration rate bH. By changing only bH,NO as the most sensitive kinetic parameter for reproducing the SNO pro®les of the
plant, the modeled concentrations of the batch experiments would change only slightly. Therefore
bH,NO is suitable for model adjustment. With a
50% higher anoxic endogenous respiration rate
(bH,NO=0.15 instead of 0.10 dÿ1 and the anoxic reduction factor 0.50 instead of 0.33, respectively) the
denitri®cation rates and thus the modeled nitrate
plus nitrite pro®les of all experiments produced a
better ®t (modeled pro®les not shown). With this
Table 4. Fractions of total COD inlet concentrations (primary e‚uent)
WWTP
TuȀenwies pilot plant
Neugut±DuÈbendorf WWTP
Neugut±DuÈbendorf WWTP
ZuÈrich±WerdhoÈlzli WWTP
ZuÈrich±WerdhoÈlzli WWTP
ZuÈrich±WerdhoÈlzli WWTP
ZuÈrich±Glatt WWTP
a
Experiment
SS,o
SI,o
XI,o
XS,o
XSTO,o
XH,o
XA,o
11±12 March 1997
26±27 August 1997
3±4 February 1998
8 March 1988a
2 December 1993a
4±5 December 1996
9±10 November 1992
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.06
0.06
0.06
0.06
0.06
0.06
0.06
0.20
0.20
0.15
0.20
0.20
0.20
0.25
0.55
0.55
0.60
0.55
0.55
0.55
0.50
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Experiments discussed in Siegrist et al. (2000).
3588
G. Koch et al.
Fig. 11. Flow scheme and operating conditions of the ZuÈrich±WerdhoÈlzli WWTP (experimental lane).
The total sludge retention time yX,tot (including the sludge blanket R1 and the inlet channel R7, Koch
et al., 1999) was 16 d. The oxygen concentration in the reactors R4 to R6 was controlled.
adjustment, bH,NO loses its physical meaning,
including any uncertainties in the model parameters
and the structure of ASM3.
To ®t the total inlet nitrogen CTN,o (equation (3))
and that total nitrogen content of the activated
sludge iN,CSB (equation (4)), iNXS and iNXI must
be 0:03 gN gX Sÿ1 and 0:04 gN gX Iÿ1 , respectively
(Table 3).
CTN,
o
ˆ iNXI XI,
…XA,
o
o
‡ iNXS XS,
‡ iNBM
‡ XH, o † ‡ SNH ‡ iNSI SI,
‡ iNSS SS,
iNCSB ˆ
o
in
‡ SNO ‰gN m ÿ3 Š
in
…3†
iNXI XI ‡ iNXS XS ‡ iNBM …XA ‡ XH †
iCSBTSS XTS
‰gN gCSB ÿ1 Š
most sensitive kinetic parameters mA, bA,O2 and
KA,NH enable a good ®t of the measured and modeled ammonium pro®les to be obtained in all experiments. Nevertheless, the ®tted maximum growth
rates of the nitri®ers vary strongly in the investigated WWTPs. It is not clear whether the inhibition
e€ects to the nitri®es in the di€erent plants due to
Fe(II), digester supernatant, wastewater composition, etc. or the general uncertainties in parameter
ÿ1
estimation (especially if yX; aer mA;
net † are responsible for the wide variation in mA. The ®tted mA and
KA,NH correspond to a net growth rate of mA, net ˆ
0:25 d ÿ1 with a standard deviation of 20.1 dÿ1 at T
= 108C for 4.0 mM alkalinity, 3.0 gO2 mÿ3 and 10
gNH4-N mÿ3, which is similar to the values given
by Gujer (1986).
…4†
From ammonium pro®les and the autotrophic oxygen-consumption rate during peak ¯ow, the maximum growth rate mA and the saturation constant
for ammonium KA,NH were estimated in all fullscale experiments (summarized in Table 2). The
CONCLUSIONS
ASM3 was tested against a wide variety of experimental data. A set of kinetic and stoichiometric
parameters is proposed to describe the sludge production, the nitri®cation and denitri®cation ca-
Fig. 12. Modeled and measured ammonium (left) and nitrate+nitrite (right) concentration in di€erent
reactors on 4±5 December 1996. The average total COD and ammonium inlet concentrations during
the previous three weeks were 200 gCOD mÿ3 and 17 gN mÿ3, respectively. T = 148C. See Table 4 for
the COD inlet fractions and Table 3 for the model parameters.
Calibration and validation of ASM No. 3
3589
Fig. 13. Flow scheme and operating conditions of the ZuÈrich±Glatt WWTP (experimental lane). The
total sludge retention time yX,tot (including the sludge blanket R1) was 15 d. The oxygen concentration
in the reactors R4 and R5 was controlled.
pacity. Aerobic and anoxic batch experiments as
well as pilot- and full-scale experiments from di€erent WWTPs were successfully modeled with the
calibrated ASM3. To further improve the prediction
of denitri®cation capacity in full-scale experiments,
the anoxic endogenous respiration rate bH,NO
should be increased by 50% compared to the value
obtained from speci®c decay experiments in the
batch reactors. This adjustment leads to bH,NO
becoming less physically meaningful, including now
uncertainties in the model parameters and structure.
The respiration rate on internal storage products is
signi®cant compared to growth on these products.
This was concluded from sensitivity analyses with
both batch and full-scale experiments. Therefore,
this process was set equal to the endogenous respiration rate.
Readily degradable inlet substrate SS,o was estimated from respiration measurements by curve ®tting. This contradicts the idea of the IAWQ Task
Group, who assumed that SS,o may be approximated by the total soluble COD as determined by
0.45-mm membrane ®ltration. This de®nition would
lead to di€erent heterotrophic yields to be selected
for the simulation of batch experiments with wastewater and single substrates, respectively. Because of
the poor correlation between soluble inlet COD and
readily degradable inlet COD, respiration tests are
still recommended for WWTP simulation to
decrease model uncertainty.
The maximum autotrophic growth rate mA resulting from parameter estimation with full-scale data
during peak ¯ow varies greatly from one plant to
another. It is not clear whether the nitri®ers in
some plants are partly inhibited by the Fe(II),
digester supernatant or the wastewater composition.
In principle, uncertainties in parameter estimation
or model structure may also play an important role
in the wide range of the ®tted mA. The parameters
of the nitri®ers may be estimated more accurately
on the basis of inhibition tests and additional batch
experiments with activated sludge from di€erent
WWTPs. In any case, for unknown wastewater the
kinetics of nitri®cation should be investigated under
di€erent operation conditions in order to obtain
relief simulation results.
Obviously, ASM3 as well as ASM1 is capable to
describe the dynamic behavior in common WWTPs
satisfactorily. In situations where for example the
storage of readily degradable substrate is dominant
(e.g. batch tests or WWTPs treating industrial
waste water with a high amount of COD) or for
Fig. 14. Modeled and measured ammonium (left) and nitrateÿnitrite (right) concentration in di€erent
reactors on 9±10 November 1992. The average total COD and ammonium inlet concentrations during
the previous three weeks were 180 gCOD mÿ3 and 15 gN mÿ3, respectively. T = 158C. See Table 4 for
COD inlet fractions and Table 3 for the model parameters.
3590
G. Koch et al.
WWTPs with substantial non aerated zones, ASM3
generates better simulation results.
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