United States
Environmental Protection
Agency
Risk Reduction Engineering
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-88/065 Apr. 1989
&ER& Project Summary
Oxygen Utilization in Activated
Sludge Plants: Simulation and
Model Calibration
C. Robert Baillod
The objective of this study is to
apply recent advances in activated
sludge process modeling to the
simulation of oxygen utilization rates
in full-scale activated sludge
treatment plants. This is done by
calibrating the International
Association for Water Pollution
Research and Control (IAWPRC)
Model and associated SSSP
(Simulation of Single-Sludge
Processes for Carbon Oxidation,
Nitrification, and Denitrification)
micro-computer software to
operating data at six full-scale
activated sludge treatment plants.
Field data were used to calibrate the
key biological parameters contained
in the model so that the oxygen
utilization rates, dissolved oxygen
concentrations, mixed liquor volatile
suspended solids concentrations,
and process performance simulated
by the model matched the
corresponding quantities observed in
the treatment plants.
The results showed that the model
and associated software package
provide a useful capability to analyze,
simulate, and predict oxygen
utilization rates. It was possible to
obtain reasonable agreement
between the measured and simulated
values of oxygen uptake rate,
dissolved oxygen concentration, and
other process parameters at most of
the plants studied. The key model
parameters were the heterotrophic
yield coefficient, heterotrophic decay
constant, and autotrophic maximal
specific growth rate constant
This information is of value to
engineers in the cost-effective design
and operation of wastewater
treatment systems because it
provides a data base of applicable
stoichiometric and kinetic model
parameters that the engineer can
use, with appropriate judgment, to
similate and predict the behavior of
oxygen transfer systems in
wastewater treatment
This Project Summary was
developed by EPA's Risk Reduction
Engineering Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
The activated sludge process is the
most widely used method for secondary
wastewater treatment in the United
States, and its popularity is increasing.
Providing oxygen to the active organisms
through aeration is the most energy
intensive aspect of activated sludge
process operation and consumes 60%to
80% of the total energy requirements in
wastewater treatment. Moreover, the
performance of the biological treatment
system is intimately linked to the proper
design and operation of the aeration
system. Thus, it is important that the
oxygen demands of the biological system
and the oxygen transfer capability of the
-------
aeration equipment be accurately
predicted. Over the past few years,
significant progress has been made in
measuring and modeling the oxygen
transfer capability of aeration equipment
under clean water and process
conditions. This study is concerned with
improvements in the techniques used to
simulate and predict oxygen utilization in
activated sludge wastewater treatment
systems.
The objective of this study is to apply
recent advances in activated sludge
process modeling (Grady et al., 1986)
(Bidstrup and Grady, 1987) to the
simulation of oxygen uptake rates in
full-scale activated sludge treatment
plants. This is done by calibrating the
International Association for Water
Pollution Research and Control
(IAWPRC) Model and associated SSSP
software to operating data at six full-
scale activated sludge treatment plants.
Models Applied to Oxygen
Utilization in Activated Sludge
Applying predictive models that can
mimic the performance of biological
waste treatment systems can aid in their
design and operation. Because biological
waste treatment systems are inherently
complex, the model must be somewhat
simpler than the actual system. Over the
past several years, various conceptual
models ranging from single substrate,
single biomass aerobic models to
multiple substrate, multiple biomass
anaerobic models have been applied to
biological waste treatment.
Conventional Approach to
Heterotrophic Oxygen
Utilization
The conventional approach represents
an activated sludge treatment system by
a single completely mixed reactor and
separator and applies overall process
oxygen, substrate, and biomass balances
to estimate carbonaceous oxygen
demand. The substrates, processes, and
pathways involved in this model are
illustrated in Figure 1.
This model considers only two
processes: aerobic growth of
heterotrophic biomass and oxidative
decay of heterotrophic biomass. The
decay process is termed "oxidative"
because it uses oxygen. It is important to
distinguish this decay process from the
hydrolytic decay process incorporated
into the IAWPRC Model. The hydrolytic
process uses no oxygen, and because of
this, the magnitude of the oxidative
decay coefficient is roughly 38% of the
hydrolytic decay coefficient. The model
assumes that each unit of biomass that
undergoes decay is partially oxidized
and partially converted to paniculate
products, which are resistant to further
decay. The observed fraction of biomass
converted to resistant particulate
products, XD, has been reported to be
0.2.
The conventional approach can be
applied to a wastewater treatment plant
by viewing the aeration tank as a
completely mixed reactor. Material
balance equations for biomass, substrate,
oxygen, particulate products, and inert
particulates can be written over the plant
and combined to express the
carbonaceous oxygen utilization rate, Rc
as,
Rc =
(1)
/ 1 + b 0 - ¥„ - f Yub 9 \
/ c c H o H c c \
\ i + b e /
c c
where:
Rc = mass of oxygen required
per unit time for the carbon
oxidation processes, M/t
Q = flow rate entering and
leaving the process, L3/t
Srjl,Sc2 = total carbonaceous oxygen
demand (ultimate BOD) of
the flows entering and
leaving the process, M/L3
bc = conventional decay coeffi-
cient for oxidative decay of
biomass, 1/t
YH = yield coefficient, mass of
volatile suspended solids
COD produced per unit
mass of carbonaceous
oxygen demand use
©c = solids retention time (SRT)
at steady state conditions,
defined as the biomass in
inventory divided by the
rate of biomass wasting, t
f0 = fraction of biomass yielding
nonbiodegradable
particulate products upon
oxidative decay, generally
taken as 0.2
The decay coefficient, bc, and yield
coefficient, YH, are biological
parameters characteristic of the biomass
itself, whereas the solids retention tin
Qc, is the key parameter that controls t
process operation and performanc
Typical values of solids retention tir
range from 3 to 12 days. Numerk
values of Y depend on the units in whi
biomass and substrate are expresse
Typical values for Y range from 0.45
0.7 mass of VSS COD produced per u
mass of feed COD utilized. Typic
values of the oxidative decay coefficie
bc, range from 0.04 to 0.4 per day.
Conventional Approach for
Nitrogenous Oxygen Utilization
The overall nitrogenous oxygi
utilization rate can be calculated basi
on the stoichiometric requirements that
mg of ammonia or Kjeldahl nitrogi
requires 4.57 mg of oxygen f
conversion to nitrate, and denitrificatii
of 1 mg of nitrate nitrogen provides ,
equivalent oxygen credit of 2.86 m
Therefore, the nitrogenous oxyg<
demand, Rn, can be expressed as:
where:
NTN = the amount of total nitrog<
converted to nitrate, mass/tim
determined by subtracting tl
total Kjeldahl nitrogen (TKN)
the effluent from the tot
nitrogen available for nitrificatic
The amount of nitrogen availab
for nitrification
-------
Substrate
Organics. Sc
Oxygen, S0
Decay
Products, Xp
Pathway
Process
Aerobic
Heterotrophic
Biomass Growth
Heterotrophic
Biomass Decay
/Negative Growth)
Mediated by
Biomass XB
Biomass XB
Figure 1. Substrates, pathways, and processes included in the conventional carbonaceous
oxygen utilization model.
TKN and nitrate concentrations in the
effluent. It does not provide any
capability to simulate or predict these
concentrations based on wastewater or
process parameters.
IAWPRC Model
In 1986, the IAWPRC task group on
"Mathematical Modeling for Design and
Operation of Biological Wastewater
Treatment" developed a model
applicable to an activated sludge system
performing simultaneous carbon
oxidation, nitrification, and denitrification.
This IAWPRC Model is described by
Gradyetal. (1986).
The substrates, pathways, and
processes included in the IAWPRC
Model are described in Figure 2.
Comparison of Figure 2 with Figure 1
shows the comprehensive nature of the
IAWPRC Model. The model contains
nine substrates inolved in eight
processes mediated by two active
biomass fractions. This model is more
complex than the conventional
carbonaceous model because
autotrophic nitrification and other
nitrogenous pathways are included and
because two classes of carbonaceous
substrate are recognized: readily
degradable (soluble) organics and slowly
degradable (particulate) organics.
Solution of the IAWPRC Model
Using the SSSP Software
Package
Bidstrup and Grady (1987) developed
the SSSP computer software package
based on the IAWPRC Model. This
oftware, written for the IBM Personal
Computer or compatible machines
performs steady state and dynamic
simulations of activated sludge systems
based on the IAWPRC Model. Both the
program and user's manual may be
copied freely. The program is versatile in
that it allows the user to define the
system configuration by using up to nine
completely mixed reactors in series.
Additional flexibility is provided by the
capability to define the influent addition,
return sludge recycle, and mixed liquor
recirculation flow diagrams between the
various reactors.
The program contains "default"
values of the stoichiometric and kinetic
parameters required by the IAWPRC
Model. These serve as reasonable
starting points for simulations and
calibration. One valuable feature of the
program is that it allows the user to
specify either reactcr dissolved oxygen
concentration or the reactor volumetric
mass transfer coefficient, KLB. The mode
in which the K|_a value is specified is
particularly useful for calibrations in
which the reactor K(_a is known. When
K|_a is specified, however, the program
uses identical values for the dissolved
oxygen half-saturation constants for
autotrophs and heterotrophs, and where
different values for these parameters are
in the input file, they are averaged to
select the value used. For this study, the
default values of the DO half-saturation
constants were set at 0.1 mg/L, which is
the normal default value for the
heterotrophic organisms.
Activated Sludge Plants
Studied
Six municipally owned and operated
wastewater treatment plants located in
Wisconsin and Michigan were selected
for calibration of the oxygen uptake
model. Table 1 summarizes the process
and flow characteristics of the plants. A
wide range of plant sizes, configurations,
industrial contributions, and SRT were
represented. The percent of plant studied
indicates the portion of the plant flow
passing through the aeration basins
monitored during the field studies. The
seventh column gives the length/width
ratios of the aeration basins, and these
values are related to the basin residence
time distribution.
All six of the plants were concurrently
being studied as part of the ASCE-EPA
Fine Bubble Diffused Aeration Design
Manual Project, and because of this,
background information on process
configuration and operation was readily
available. Moreover, frequent off-gas
measurements of oxygen transfer were
being made at five of the six plants as
part of the ASCE-EPA project. These
measurements were particularly valuable
because they produced accurate
estimates of the process volumetric mass
transfer coefficients for oxygen (K(_a).
The 24-hr studies conducted at each
of the plants were designed to acquire
information necessary to calibrate the
IAWPRC Model. The steady state model
solution, based upon flow weighted
average conditions, was used to calibrate
key parameters, and these parameters
were later used in the dynamic solution
to simulate diurnal variations in oxygen
uptake rate (OUR). By comparing the
simulated and measured diurnal ranges,
the usefulness of the dynamic solution
for design purposes could be assessed.
-------
Table 1. Plants Included in Field Study
cs
c
SF
L/W
Plant
Portage Lake
Green Bay
Madison
Monroe
Jones Island
South Shore
= Contact Stabilization
= Conventional
= Step Feed
= Length/Width
Average
Flow
m3/day
8,700
182,000
151,000
8,300
288,000
371,000
Annual
BOD-5
mg/L
150
375
170
418
300
162
- Percent of
Plant
Studied
50%
33%
13%
33%
4%
5%
Process
SRT Days
10.6
3.1
16.4
8.4
2.8
4.3
Configuration
CS
CS
C
SF
C
SF
Aer., UW
1.5
3.4
26
8.2
15
6.5
Industrial Contribution
Flow %
<5%
30%
6%
17%
11%
6%
BODS %
<5%
50%
15%
50%
38%
18%
Oxygen Uptake Rate
Measurement
OUR was measured in two ways: by
the conventional batch BOD bottle
technique and by off-gas measurement.
The BOD bottle technique required that a
mixed liquor sample be rapidly
withdrawn, aerated, and transferred to a
BOD bottle. The DO concentration in the
bottle was monitored, and the OUR was
calculated from the rate of DO decrease.
Although, this method itself gives an
accurate and precise in-vitro measure
of the oxygen utilization rate that occurs
in the BOD bottle, this may not represent
the in-situ OUR occurring in the reactor
from which the sample was withdrawn.
Two conditions, oxygen limitation and
soluble substrate limitation, can cause
the OUR measured by the BOD bottle
method to differ significantly from the
in-situ value.
Oxygen limitation arises when the in-
situ DO is near zero; this causes the in-
situ OUR to be limited by the availability
of oxygen. A sample subjected to the
BOD bottle method is exposed to high
DO concentrations and will respire at a
higher rate. Consequently, when in-situ
DO concentrations are near zero, the
OUR indicated by the BOD bottle
method will be its potential maximal
value, which will be greater than the in-
situ OUR. Substrate limitation arises
when the in-situ exogenous substrate
concentration is near zero; this causes
the OUR of a withdrawn sample to
decrease between the time of withdrawal
and the time at which the BOD bottle
OUR is measured. To avoid these
limitations, the BOD bottle OUR values
measured on samples taken from
regions where the DO was less than 1.5
mg/L were not used in model calibration,
and more weight was given to bottle
OUR values measured under
endogenous conditions.
Off-gas measurements made at five
of the six plants were used in the gas-
side oxygen balance to estimate the
process water volumetric mass transfer
coefficient (K|_a). These coefficients
were then incorporated into the liquid-
side oxygen balance in the IAWPRC
Model to relate the DO concentration to
the OUR. Therefore, when the model was
calibrated to simulate a DO value in
agreement with the measured DO value,
the simulated OUR agreed with the OUR
measured by the off-gas measurement.
Theoretically, this enabled the in-situ
OUR to be determined from DO
measurements and served as a check on
the BOD bottle OUR. However, even
though the off-gas measurements were
made simultaneously with the 24-hr
studies at two of the plants, changes in
wastewater characteristics cause the
alpha factor to change continuously and
make it impossible to determine the
process water K|_a with a precision
greater than 10%.
Model Calibration
Calibration of the IAWPRC Model
required that the wastewater feed
components required by the model be
determined from the plant data, that the
kinetic and stoichiometric parameters
required by the model be estimated, and
that criteria for calibrating the model to
the plant data be established. Thirteen
components are considered in the
IAWPRC Model and most of them may
be present in the feed wastewater.
During the 24-hr plant studies, samples
of the wastewater fed to and samples of
clarified effluent from the activated
sludge processes were analyzed for total
COD, soluble COD, ammonia, total
organic nitrogen, and nitrate. These d
were used to establish the concentrat
of feed components for model calibrate
A sensitivity analysis of the bionru
parameters showed that OUR was m
sensitive to the heterotrophic a
autotrophic yield and decay coefficier
Overall, the heterotrophic yield, YH, a
decay, bn, showed the most impact
the simulated values of OUR, DO, a
MLVSS. The autotrophic yield, Ya, dec;
ba, and maximal specific growth ra
Ham. had the most impact on simulal
values of ammonia and nitrate. Values
the more sensitive parameters we
determined by calibrating the model
the data. Parameters to which the moi
predictions were insensitive were set
the adjusted default values. In genei
these values were determined
applying a temperature correction to 1
default kinetic parameters given in I
SSSP program.
This study was primarily concern
with the oxygen utilization aspects of I
model. Because the IAWPRC moc
simulated many other system respons
(e.g., MLVSS, DO, nitrate) in addition
OUR, an effort was made to calibrate 1
model so that it simulated MLVSS, C
nitrate, and ammonia as well as OL
Primary emphasis was placed
matching the OUR and DO. Less
weight was placed on matching t
MLVSS and nitrogen concentrations.
The model parameters were estimat
by calibrating the model to the avera
plant data measured during the 24
studies. The process flow diagram w
modeled as realistically as possible
using a combination of completely mix
reactors and perfect clarifier/thickeners
steady state simulation was performed
using the SSSP software package w
default values of all parameters.
second steady state simulation w
-------
Substrate
Pathway
Process
Mediated by
Soluble
Organic Ss
Oxygen So
Ammonia SNH
Alkalinity SAik
Nitrate SNO
Soluble
Organic N SND
Paniculate
Organic N XND <-
Paniculate
Organic Xs
Decay
Products XE
Aerobic
Heterotrophic
Biomass Growth
Anoxic
Heterotrophic
Biomass Growth
Autotrophic
Biomass Growth
Hydrolysis and
A mmonification
(Non-Growth)
Heterotrophic
Biomass Decay
(Negative Growth)
Autotrophic
Biomass Decay
(Negative Growth)
Heterotrophic
Biomass XBH
Heterotrophic
Biomass XBH
Autotrophic
Biomass XB*
Heterotrophic
Biomass XBH
Heterotrophic
Biomass XBH
Autotrophic
Biomass, XBA
Figure 2. Substrates, pathways, and processes included in the IAWPRC Model.
performed by using temperature
adjusted default values for the kinetic
parameters contained in the model. The
model-simulated values of OUR, DO,
MLVSS, nitrate, and ammonia, based on
the temperature adjusted default
parameters, were then compared with
the measured average values, and the
model was calibrated to the measured
data by adjusting selected key model
parameters. In all but one case, where
the hydrolysis rate constant was also
changed, these adjustments were limited
to the heterotrophic yield and decay
parameters and the autotrophic maximal
specific growth rate. In addition, the
, autotrophic half saturation constant for
DO was made equal to the default value
of the heterotrophic half saturation
constant for DO (0.1 mg/L).
Dynamic simulations were also
performed with the use of the SSSP
software package with the calibrated
parameters determined from the steady
state simulation. This gave simulated
diurnal profiles for OUR and DO. These
were then compared with the measured
profiles to judge how usefully the model
simulates reasonable variations in
oxygen utilization.
Results
The average measured values
reasonably agreed with the steady state
simulated values for OUR, DO, MLVSS,
nitrate, and ammonia at most of the
plants studied. Only two of three key
parameters were calibrated to achieve
this agreement. The other 17 parameters
were set at their temperature adjusted
default values. Notable lack of
agreement between the simulated and
measured values was evidenced at the
Jones Island Plant where the simulated
and measured effluent ammonia
concentrations did not agree well, and at
the South Shore Plant where the
simulated and measured MLVSS values
did not agree well.
Table 2 summarizes the values of the
key parameters that resulted from model
calibration.
-------
Total Process Average Oxygen
Utilization Rates
An estimate of the total daily process
average oxygen utilization rate can be
made by multiplying the estimated OUR
values by the corresponding reactor
volumes. In the absence of direct
measurements of OUR values for all tank
regions, the best estimates of OUR for
the various reactor regions are given by
the SSSP simulation based on the
calibrated parameters. These estimates
are consistent with the measured OUR,
DO, off-gas, and solids data used to
calibrate the model. An example
calculation for the portion of the Madison
plant studied is shown in Table 3.
Values of the best estimates of the
total process average oxygen utilization
rates calculated in this manner for all six
plants are shown in column 2 of Table 4.
These quantities apply to that portion of
the plant included in the 24-hr studies.
Consequently, the magnitudes of the
utilization rates reflect both the size of
the plant and the fraction of flow treated
by the portion of the plant included in the
study. Thus, the utilization rates reported
for the Green Bay plant where the
portion under study treated 33% of the
plant flow are much greater than the
rates reported for the larger Jones Island
plant where the portion under study
treated only 4% of the plant flow.
A similar, more conventional estimate
may be made by viewing the process
aeration tank as a single completely
mixed reactor and applying the
conventional model given by Equation 1
to calculate the carbonaceous oxygen
utilization rate, Rc. The values of the
heterotrophic yield coefficient, YH, used
in the IAWPRC (SSSP) and conventional
models are identical. However, the
appropriate value of the oxidative decay
coefficient, bc, for use in the conventional
model was calculated as 38% of the
IAWPRC hydrolytic decay coefficient, b.
The total oxygen utilization rate is then
calculated according to Equation 2 after
determining the nitrogenous oxygen
demand from Equation 3.
Column 3 of Table 4 summarizes the
total process average oxygen utilization
rates calculated for all six plants using
the conventional model. For most of the
plants, the agreement between the
IAWPRC and conventional models was
excellent as the estimates generally
agreed within 10%. The exceptions to
this were the two Milwaukee plants,
Jones Island and South Shore, where the
conventional approach estimated an
oxygen utilization rate 15% greater than
the IAWPRC approach.
It can be concluded that, for given
values of the yield and decay
coefficients, the two approaches produce
estimates of the average process oxygen
utilization rate, which agree reasonably
well. In this study, the IAWPRC model
was calibrated to plant data and,
therefore, was judged to give the better
estimates of the process oxygen
utilization rates. There is some indication,
based on the Milwaukee plants, that the
conventional approach may slightly
overestimate the oxygen utilization rate.
These results show that the
conventional approach is useful but has
several disadvantages when compared
with the IAWPRC Model and SSSP
software package. Both approaches need
applicable values of the heterotrophic
yield and decay coefficients. The
conventional model, however, does not
distinguish between slowly and readily
degradable substrates and cannot easily
be adapted to simulate spatial and
temporal variations of OUR. Moreover,
the conventional approach can neither
simulate nor predict nitrogenous oxygen
demand. It can only calculate
nitrogenous oxygen demand based on
observed influent and effluent nitrogen
concentrations. On the other hand, it was
observed in this study that the IAWPRC
Model needs only one additional
calibrated parameter, the maximal
autotrophic specific growth rate, to
simulate the entire process. In almost all
cases, default values of all but two or
three parameters (heterotrophic yield,
heterotrophic decay, and autotrophic
maximal specific growth rate) were
adequate in model calibration.
Conclusions and
Recommendations
Based on the results of this study, it
can be concluded that:
I.The IAWPRC Model and related
SSSP microcomputer software
package provides a useful capability
to analyze and simulate the average
oxygen utilization rate in municipal
wastewater treatment plants.
2. It was possible to obtain reasonable
agreement between the average
measured and steady state
simulated values of OUR, DO
concentration, MLVSS, effluent
ammonia, and effluent nitrate
concentrations at most of the plants
studied. This agreement was
achieved by adjusting or calibrating
only 2 of 3 key model parameti
while keeping the other 17 mo<
parameters at their adjusted defe
values. The key model parameti
were the heterotrophic yie
coefficient, heterotrophic dec
constant, and autotrophic maxin
specific growth rate constant.
3. When provided with a realistic val
of the process water volumetric mz
transfer coefficient (Ki.a), t
calibrated model and software w<
normally able to simulate the spal
and temporal range of C
concentrations and oxygen utilizati
rates observed in the operati
treatment plants. Instances in whi
lack of agreement between simulat
and observed values occurred coi
possibly be explained by caus
other than model and/or softwe
inadequacy.
4.Under conditions of low C
concentration (below 1 to 2 mg/
in-vitro OUR values indicated I
the traditional BOD bottle meth'
tended to be greater than the in-s
OUR values determined from o
gas analyses. These differenc
were most evident in the inl
sections of long aeration tanks whe
OUR values were high and C
values were low.
S.When the IAWPRC Model ai
conventional approaches to estimj
average process oxygen utilizatii
rates were compared, the tv
approaches agreed reasonably w
for given values of the yield ai
decay coefficients. In this study, tl
IAWPRC Model was calibrated to tl
data and, therefore, was judged
give the better estimates of tl
process utilization rates. Moreovt
the IAWPRC Model was judged to I
advantageous because of its abili
to simulate nitrogenous oxyg<
demand.
This study relied on adjusting
calibrating key parameters to show th
the IAWPRC Model could be applied
analyze, simulate, and predict oxyg<
utilization and other activated sludc
process characteristics. Such informatk
is valuable because it provides a da
base of key parameters from whi<
engineers can draw information f
process design and operation. Howevt
this data base should be expanded
include information from more than tl
six plants of this study. Moreover,
would be of particular value
demonstrate the applicability
-------
Table 2. Summary of Model Calibration of Key Parameters"
Plant
Default (20°C)
Madison
Monroe
Portage Lake
Jones Island
South Shore
Green Bay
Heterotrophic Yield
Coefficient,
g COD/g COD
0.67
0.57
d
0.69
d
0.46
0.57
Heterotrophic Decay
Constant, 1/day
0.62
d"
0.80
1.10
0.35
0.50
d
Autotrophic Maximal
Specific Growth
Rate, 1/day
0.65
0.34
0.34
d
0.62
d
0.45
"All other parameters were set at temperature adjusted default values.
"Signifies temperature adjusted default value.
Table 3. Calculation of Total Process Average Oxygen Utilization Rate for Madison Plant
Based on Calibrated IAWPRC Model
Reactor Volume, m3
1 1,733
2 4,008
3 3,827
4 1,914
OUR, g/m3/day
468.7
541.1
404.8
341.3
Total
Utilization Rate,
kg/day
812.3
2,168.7
1,549.2
653.2
5,1 83.4 kg/day
Table 4. Comparison of Total Process Average Oxygen Utilization Rates Estimated by the
IAWPRC and Conventional Models
Oxygen Utilization Rate, kg/day
Plant
Madison
Monroe
Green Bay
Portage Lake
Jones Island
South Shore
IAWPRC
Model Total
5,183
822
29,350
593
2,544
3,079
Conventional Model
Total
5,001
845
30,600
633
2,925
3,532
*c
3,797
587
30,448
592
2,803
2,352
«n
7,204
264
752
47
722
7,780
Percent
Difference
+ 3.5
-2.9
-4.3
-6.8
-75.
-75.
techniques for key parameter estimation
based on direct measurements.
Accordingly, it is recommended that
additional in-depth studies applying the
IAWPRC Model and associated SSSP
software to well controlled, full-scale
wastewater treatment plants be
conducted. It is also recommended that
design engineers be encouraged to
apply the IAWPRC Model and associated
SSSP software to activated sludge
process design. Although other improved
models and software might be developed
in the future, this model and software are
available now and are easily usable by
any design engineer. With the aid of
engineering judgment and the parameter
data base given in this report, this
approach will facilitate more economical
and effective design and operation of
wastewater treatment plants.
References
Bidstrup, S.M., and Grady, C.P.L, Jr., "A
User's Manual for SSSP," Clemson
University, Clemson, South Carolina,
1987.
Grady, C.P.L., Jr., Gujer, W., Henze, M.,
Marais, G.v.R., and Matsuo, T., "A
Model for Single Sludge Wastewater
Treatment Systems," Wat. Sci.
Tech., 75:47-61, 1986.
The full report was submitted in
fulfillment of CR813162-01-2 by
Michigan Technological University under
the sponsorship of the U.S. Environ-
mental Protection Agency.
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C. Robert Baillod is with Michigan Technological University, Houghton, Ml
49931.
James A. Heldman is the EPA Project Officer (see below).
The complete report, entitled "Oxygen Utilization in Activated Sludge Plants:
Simulation and Model Calibration," (Order No. PB 89-125 9671'AS; Cost:
$T5.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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PERMIT No. G-35
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