1. Internship Report
October 2014 - January 2015
At
Environmental Dynamics International. Inc
Student: Can Cui
Program: Modeling of Partially Mixed Zone
Supervisor: Tim Canter
January 19 2015

2. 1
Acknowledgement
It was a great opportunity for me to do a three-month internship at Environmental
Dynamics International (EDI). First of all, I would like to thank Mr. Tim Canter, the
Global Product Manager of Lagoon Solutions at EDI, for giving me the opportunity. For
me, it was a unique experience at the last stage of my graduation study. I was able to
apply what I have learned in courses and obtain invaluable hand-on experiences in
biological wastewater treatment modeling. My abilities of problem solving,
communicating, independent learning and attention to details also improved greatly.
I would also like to thank Dr. Chris Bye at EnviroSim Associates Ltd., Dr. Zhiqiang Hu
and Dr. Enos Charles Inniss at University of Missouri-Columbia, for providing technical
support during my internship.

3. 2
Summary
The internship was concentrated to tackle ammonia rebound issue in a lagoon
system when temperature starts to rise from January to late May. The system consists of
two lagoons, IDEAL™ followed by a polishing lagoon. The IDEAL™ (Intermittently
Decanted Extended Aeration Lagoon), is a fully aerated lagoon and operated like
extended SBR system. The first part of the polishing lagoon, also known as partially
mixed (PM) zone, receives effluent water and MLSS from upstream IDEAL lagoon and
is hired for solids separation and sludge storage. After further solids removal in quiescent
zone, the final clean water is discharged out of the treatment system.
The internship was a step-by-step process. The accuracy of data can never be overstated
so I first reviewed the sample storage, preservation and measurement and provided my
suggestions to increase the data reliability. With all the proceeding preparation and data
at hand, I started to build a model for PM zone to analyze the rebound of ammonia. Two
approaches were proposed. One is mathematical approach and the other is BioWin
simulation approach. Results from both approaches indicate that the system is very
complicated and more data of PM zone and temperature and other parameters were
needed for better modeling.

4. 3
Contents
1. Modification of current sample storage, preservation and measurement methods......... 4
2. Model building................................................................................................................ 7
2.1 Introduction........................................................................................................................7
2.2 Conceptual model ..............................................................................................................9
2.3 Nitrification in PM zone...................................................................................................10
2.4 Basic calculation of PM zone ..........................................................................................11
3. BioWin simulation approach ........................................................................................ 13
3.1 Introduction......................................................................................................................13
3.2 Parameters of simulation.................................................................................................16
3.3 Simulation results and discussion....................................................................................18
4. Mathematical approach................................................................................................. 20
4.1 Mass balance of ammonium in PM zone .........................................................................20
4.2 Total biomass accumulated in PM zone ..........................................................................21
4.3 Ammonia released to water from settled biomass ...........................................................21
4.4 Nitrification in water column...........................................................................................21
4.5 Challenges about mathematical model............................................................................22
5. Conclusion .................................................................................................................... 22
5.1 Possible explanations of ammonia rebound ....................................................................22
5.2 Additional parameters .....................................................................................................24

5. 4
1. Modification of current sample storage, preservation and
measurement methods
The first step of the internship is to scrutinize the sample storage, preservation and
analysis methods, which the company hired, and compare the methods with standard
methods to ensure reliability.
Appropriate storage and preservation are vital for obtaining reliable data. For
wastewater samples, the nature of sample changes with high temperature and exposure to
air. Microbiological activities also affect the nitrate-nitrite-ammonia content if the
samples are not well stored. However, I found some activities of sample storage,
preservation and measurement are improper and need to be corrected in the future. They
are summarized as followed.
1) The samples should be stored at low temperature and insulated from air
during transportation.
To minimize the volatilization or biodegradation of samples before analysis,
water samples should be kept at 4 °C in refrigerator or in ice water mixture for
transportation from the treatment plant to the lab, especially in summer, when
temperature is high and bacteria are very active. Besides the temperature, water samples
should also be isolated to prevent bacteria contamination. The operator didn’t keep the
samples at low temperature and isolate the samples, so it might cause some adverse effect
on the measurement.
2) The samples should be refrigerated as soon as possible if they are not
analyzed immediately.

6. 5
After arriving in lab, the samples should be refrigerated as soon as possible if not
analyzed immediately because at high temperature the bacteria will biodegrade the
nitrogen and cause error to the results. The action that the operator left the water samples
at room temperature should be avoided in the future.
3) The samples should be stored by containers of the same material (all
plastic or glass).
When taking samples, the operator sometimes use containers of different material.
It is unknown whether different material causes difference in the results, but to increase
the accuracy to a max extend, I suggest the operator use the same material.
4) The samples need to be filtrated before analysis.
Before analyzing the ammonia concentration, the water samples should be
filtrated with 0.45µm pore size membrane filter to remove the solids. If the membrane
filter is not available, filter paper (fine pores) can serve as an alternative. Filtration is
necessary because turbidity may interfere with the final results. Thus fine solids should
be removed for future measurement.
5) The samples should be analyzed within 24 hours after reaching lab or
preserved at 4°C up to 7 days for ammonia measurement.
For ammonia measurement, Standard Methods suggests measurement carried out
as soon as possible. If samples can be analyzed within 24 hours of collection, the lab
operator can store the samples at 4 °C and unacidified. However, if preservation is
required or necessary, the operator can preserve samples by adding sulfuric acid to the
samples to pH <2 and storing at 4 °C up to 7 days. Burke et al’s research indicates that
after 7 days of preservation (acidification by sulfuric acid and stored at 4 °C), it is

7. 6
impossible to obtain reliable results. The third party lab used 25% (percentage by volume)
of sulfuric acid for preservation more than 7 days. This should be avoided in the future to
get more accurate results.
Table 1 shows container, sample size, and preservation suggestions from the
Standard Methods.
Table 1: Nitrogen species guidance for sample size, container type, and preservation
method
6) Duplicate or triplicate water samples should be obtained from lagoon and
duplicate or triplicate measurements should be carried out for each sample.
While sample storage and preservation are crucial for data accuracy, the
measurement is of same importance. Duplicate or triplicate samples and measurements
help to eliminate the chance of unexpected disturbance and calculate the standard
deviation. If the results deviate from each other too much, the lab operator may consider
repeating the measurement or changing new samples until the results are reasonable. The

8. 7
sample and measurement are only taken once during the operator’s sampling and
measurement. This should be corrected in the future.
In conclusion, to ensure reliable results, I recommend the operator strictly follow
the requirements and avoid contamination and deterioration of samples. After samples
reach the lab, the lab operator should take the measurement as soon as possible or
preserve at 4 °C up to 7 days. The samples and measurement should be taken duplicate or
triplicate for statistical analysis.
With all the preparation work completed, a model of PM zone is built for further
analysis of rebound. In the following paragraphs, the model will be presented in three
aspects: considerations of model building, BioWin simulation model and mathematical
model.
2. Model building
2.1 Introduction
The lagoon process for municipal wastewater treatment has been used in the
United States for over 40 years with merits of low cost, easy maintenance and high-
efficiency to remove COD. The drawbacks are obvious too: lagoons have limited ability
to remove nutrients and in cold weather conditions effluent water quality deteriorated. As
the requirement of effluent water quality proposed by US E.P.A (United States
Environmental Protection Agency) is more and more stringent, especially the nitrogen
concentration, upgrade of lagoon technology becomes necessary.
The IDEAL™ (Intermittently Decanted Extended Aeration Lagoon) Solution
proposed by EDI is an innovative approach to provide full nitrogen removal under low
temperature condition. The IDEAL is a fully aerated lagoon and the treatment mode is

9. 8
like extended SBR system. After 4-hour operation in IDEAL lagoon, clean effluent water
is discharged to partially mixed (PM) zone. In the case of Miner, MO the sludge is
wasted through the decanters to a downstream polishing lagoon, which consists of a PM
zone followed by a quiescent zone. The PM zone receives effluent water and MLSS from
upstream IDEAL lagoon and is hired for solids separation and sludge storage. After
further solids removal in quiescent zone, the final clean water is discharged out of the
treatment system.
Figure 1. Plan view of IDEAL and polishing lagoon
The performance of IDEAL is stable and highly efficient even during severe cold
winter. However ammonia rebound was observed from late April to early May 2014
when temperature rose. Effluent ammonia from IDEAL is below the method detection
limit (0.05 mg/L), so it is believed that excess ammonia is from PM zone where large
quantity of sludge is stored.
In order to find out where excess ammonia comes from and to better understand
the biological activities in PM zone, a conceptual model is developed. In this chapter, the
model will be presented as well as analysis of nitrification activities in PM zone so that
based on the discussion of model and biological activities we can come up with possible

10. 9
mechanisms for ammonia rebound. The calculation of PM zone is covered at the end of
the chapter in preparation for discussion of BioWin and mathematical approaches.
2.2 Conceptual model
A conceptual model of the PM zone is presented in figure 2. This model shows a
sludge deposit dividing into three layers based on oxygen distribution. Dissolved oxygen
(DO) in water is saturated due to aeration from bottom and partial agitation makes the
oxygen in water gradually penetrate into the sludge deposit. So from layer one to three,
they can be viewed as in aerobic, anoxic and anaerobic conditions. Layer one, the aerobic
layer, because of ample oxygen around, has nitrifying bacteria attaching to the surface
and conducting nitrification. Layer three, completely isolated from oxygen, undergoes
anaerobic fermentation and thus releases ammonia. Layer two, in anoxic condition, have
both biological activities.
Besides autotrophic bacteria, heterotrophic bacteria also contribute to the changes
of nitrogen concentration through assimilating ammonia for growth but ammonia
removed by assimilation is much less than nitrification and is assumed negligible in
consideration of nitrogen changes.
The MLSS concentration in the PM zone is 150 mg/L. As nitrifying bacteria
comprise a very small portion of biomass, it is reasonable to assume no nitrification and
weak biomass decay are occurring in the water column.
When it comes to biological activities, temperature should always be emphasized
for their crucial effect. During the sampling period, December 2013 to June 2014,
temperature range was between 13°C and 2.3°C in the IDEAL reactor. Low temperature

11. 10
will inhibit the activities of nitrification and decay so in the model it will be set as the
limiting variable to affect ammonia concentration.
Figure 2. Conceptual model of PM zone
2.3 Nitrification in PM zone
Nitrifying bacteria are autotrophic microorganisms that obtain their energy from
the oxidation of reduced nitrogen. Two types of bacteria are involved in nitrification,
ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). They are very
sensitive to low temperature and low oxygen. Research has shown that oxygen
concentration below 2.0 mg/L begin to have a strong negative effect on nitrifying bacteria
and those below 0.5 mg/L have an even stronger negative effect. Low temperature also
greatly inhibits the activity of nitrifying bacteria and causes some loss of the population.
Once temperatures begin to increase, the population should begin to recover.
The growth of nitrifying bacteria can be expressed by the Monod equation (1):
(1)
where,
µ is the specific growth rate of the microorganisms;
µmax is the maximum specific growth rate of the microorganisms;

12. 11
S is the concentration of the limiting substrate for growth;
Ks is the half-saturation coefficient, the value of S when µ/µmax = 0.5.
Equation 1 explicitly shows that when S is small, µ is linearly proportional to S.
In the PM zone, ammonia is the limiting substrate for growth of AOB and NOB.
2.4 Basic calculation of PM zone
For partially mixed (PM) zone, there is no sludge accumulation at the bottom
because of benthal aeration. Sludge is mainly accumulated on the inlet side. Assume
sludge accumulate on levee and occupy all the space above the levee as illustrated in
Figure 3.
Figure 3. Side view of PM zone
1) Volume of PM zone (Figure 4):
VPM zone = [(150 ft) × (350 ft) × (25 ft) × (1/3) – (90 ft) × (290 ft) × (15 ft) × (1/3)] – [(150
ft) × (120 ft) × (17 ft) × (1/3) – (90 ft) × (90 ft) × (13 ft) × (1/3)]
= 307000 ft3
– 66900 ft3
= 240100 ft3

13. 12
Figure 4. Calculation of volume of PM zone
2) Assume sludge all accumulate on the inlet side(Figure 5):
Volume of sludge deposit:
Vsludge deposit = (150 ft) × (30 ft) × (25 ft) × (1/3) + (90 ft) × (25 ft) × (0.5) × (30 ft) × (1/3)
= 37500 ft3
+ 11250 ft3
= 48750 ft3
Figure 5. Calculation of volume of sludge deposit
3) Volume of water:
Vwater = VPM zone – Vsludge deposit
= 240100 ft3
–48750 ft3
= 191350 ft3

14. 13
3. BioWin simulation approach
3.1 Introduction
Since the biological activities in PM zone are very complicated, I used BioWin
software for simulation of the PM zone. In BioWin, lagoon is not a primary treatment
process so we need to combine other primary processes to simulate the lagoon treatment.
The following chart (figure 6) is a lagoon process developed by EnviroSim. The
water column and sediments stand for water phase and sludge phase in a lagoon
respectively. The Water Column, an aerated reactor in BioWin, simulates the biological
activities under aerated condition in lagoon water phase. While the Sediments, an
anaerobic digester in BioWin, undergoes anaerobic digestion of the sludge, just like the
same process at the bottom of a real lagoon. The point clarifier is used to retain solids and
itself has no volume. Because of internal agitation in real lagoon, some solids will go
back and forth between water phase and settled sludge phase. These solids will finally
settle down at the bottom thus no obvious solids loss occurs in real lagoon. The point
clarifier in the flow-chart functions to retain solids in Sediments and prevent solids loss.
Although I proposed three layers of the sludge deposit in the conceptual model, to
make it easier to adjust the parameters in simulation, I decide to adopt this model and not
to add Sediments configuration, which may have a more accurate simulation of the
sludge deposit.
So the goal of BioWin simulation is through adjusting the parameters of
temperature, DO, AOB and NOB concentration and their kinetics of growing to get the
effluent ammonia concentration pattern similar to the one monitoring by the company.

15. 14
Figure 6. Flow chart of BioWin simulation
Each configuration in the BioWin simulation is explicitly presented in following
paragraphs.
1) Influent: the influent in this simulation system is effluent from IDEAL lagoon.
The N-species concentration from IDEAL effluent is unknown. To simulate the influent
to PM lagoon, I use the final effluent concentration. Random grab samples form the
IDEAL near the decanter at the time of decant returned ammonia-nitrogen concentrations
of <0.05 ppm. So it is reasonable to assume influent ammonia to PM zone is zero. As for
nitrate, nitrite and total COD, the total average concentration of final effluent is used.
Influent water quality parameter:
Flow: 849 m3
/d
Total COD: 19 mg/L
TSS: 1400 mg/L
VSS: 980 mg/L (70% of TSS)
Ammonium: 0 mg/L
Nitrate: 8.39 mg/L
Nitrite: 0.76 mg/L

16. 15
TKN: 98 mg/L (10% of VSS)
2) Water column: used to simulate water portion in PM zone. The volume of water
column is as calculated before. The water column configuration is a bioreactor and will
conduct COD removal and nitrification.
Volume of Water Column: 191350 ft3
= 5418 m3
HRT = V/F = 5418/849 d = 6.4 d
3) Sediments: used to simulate sludge deposit in PM zone. The volume is calculated
before. Sediments configuration is an anaerobic digester and will release ammonia
through decay process.
The volume of sediment equals to the volume of sludge deposit
Volume: 48750 ft3
= 1380 m3
TSS concentration of sediment: 100 g/L = 105
g/ m3
= 100 kg/ m3
Mass of sludge deposit: (1380 m3
) × (100 kg/ m3
) = 1.38 ×105
kg
4) Point clarifier: point clarifier is an ideal reactor. It has no volume and is employed to
retain solids which go back and forth between water column and sediments, just like what
happens in real lagoon. Otherwise, solids will be eventually washed out from sediments.
In the conceptual model, sludge deposit is divided to three layers. The reason why
only anaerobic sludge layer is modeled in BioWin simulation is for simplicity of
modeling. The aerobic layer contacting with water is incorporated into water column to
carry out nitrification in simulation. Anoxic layer is assimilated in both water column and
anaerobic digester. The current model with two reactors is easy and simple for adjusting
parameters and analyzing the results.

17. 16
3.2 Parameters of simulation
In BioWin simulation, all biological activities rely heavily on temperature. The
influence of temperature is reflected by the Arrhenius coefficient Θ. Besides temperature,
the value of each parameter is also significant for simulation. So it is necessary to explore
the effect of each parameter on effluent ammonia.
First of all, a simulation is processed with default settings and these results will be
saved for control and contrast. Then each of the parameter of interest is changed while
keeping others the same.
1) Hydrolysis rate value
Figure 7. The effect of hydrolysis rate on effluent ammonia (2.1 is default number)
The simulation results show that hydrolysis rate has no effect on effluent
ammonia in BioWin simulation.
2) Arrhenius coefficient of hydrolysis rate

18. 17
Figure 8. Effect of Arrhenius coefficient on effluent ammonia in BioWin simulation
(1.029 is default number)
As seen from the figure, when Arrhenius coefficient of hydrolysis rate increases,
effluent ammonia decreases.
3) AOB growth rate
Figure 9. Effect of AOB growth rate on effluent ammonia (0.9 is default number)
As shown in figure, when AOB growth rate increases, effluent ammonia
decreases.
4) NOB growth rate
Figure 10. Effect of AOB growth rate on effluent ammonia (0.7 is default number)

19. 18
The above figure shows that effluent ammonia in simulation decreases when
AOB growth rate increases.
5) Arrhenius coefficient of AOB and NOB
Figure 11. Effect of Arrhenius coefficient of AOB and NOB on effluent ammonia (1.072
is default number)
The above figure shows that when Arrhenius coefficient of AOB and NOB
decreases, effluent ammonia decreases.
3.3 Simulation results and discussion
Simulation results from BioWin differ from each other greatly with different
parameters setting. The result that fits the pattern of data set from Minor project is shown
below.
Figure 12: BioWin simulation results for variable parameters

20. 19
Although the pattern is similar, the peak value of effluent ammonia from
simulation is up to 30 mg/L, which is much higher than practical data. The time of peak
showing is postponed in simulation. What is more, instead of back to normal in Minor
project, the effluent ammonia starts to increase again from late May.
Here are the possible reasons:
1) More data is needed for better modeling
First of all, PM zone temperature is absent. The temperature at hand is air
temperature and water temperature in IDEAL. Compared to air temperature, water
temperature has smaller range. And because aeration in IDEAL lagoon is much higher
than in PM zone, the temperature in PM zone should be lower than IDEAL lagoon
temperature. At present this set of data is absent.
Secondly, sludge deposit temperature is also needed. Sludge deposit in PM zone
undergoes anaerobic digestion. The energy released from sludge deposit will be trapped
in sludge so the temperature of sludge deposit should be higher than ambient water. We
may want to consider measuring the sludge temperature in the future.
Thirdly, effluent water from IDEAL lagoon is not monitored on a regular basis. I
suggest taking effluent water from IDEAL lagoon and track the water quality for quality
control. The data will also be useful for better modeling of PM zone.
2) Limitation of Biowin software
Finally, it is still not clear whether the hydraulic disturbance inside the PM zone
has a significant contribution to excess ammonium. Monitoring the suspended solids (SS)
concentration near the sludge deposit may be advisable when temperature starts to rise in
late March. If there is significantly increase in SS near sludge deposit, it is likely that

21. 20
excess ammonium come from solids. However, in BioWin, there is no specific
configuration for lagoon. The model showed above is convenient to simulate the
biological activity but not hydraulics. The limitation may be a key factor in BioWin
simulation.
4. Mathematical approach
4.1 Mass balance of ammonium in PM zone
Due to the limitation of BioWin software, I also proposed mathematical approach
to simulate the nitrogen activities. The fundamental idea of mathematical approach is to
set up an ammonia mass balance (equation 2) in PM zone. By calculating and comparing
the amount of ammonia released from sludge and oxidized by AOB and NOB, we can
find how the ammonia rebound is related to temperature or other factors we didn’t
recognize before.
Mass balance equation:
Accumulation = Influent + Reaction - Effluent (2)
Influent: ammonia coming into PM zone is assumed to be zero because ammonia
in effluent water from IDEAL lagoon is below detection limit so it is reasonable to
assume influent ammonium to PM zone is zero.
Reaction: releasing from sludge deposit and nitrification will both affect
ammonia concentration. Each of these reactions will be articulated in the following
paragraphs.
Effluent: effluent ammonia is a term to be calculated.
Accumulation: assume no ammonia is retained in PM zone and all ammonia in
water is discharged out of the system. So accumulation is zero.

22. 21
Thus a simplified mass balance equation is:
Reaction - Effluent = 0 (3)
4.2 Total biomass accumulated in PM zone
Mass of sludge deposit (sludge already settled in PM zone)
M = 1.38 ×105
kg
Total biomass coming into PM lagoon
MLSS to PM lagoon: 1400 mg/L = 1.4 g/L = 1.4 kg/m3
Average flow rate: 0.2 MGD = 757 m3
/d
So biomass discharging rate to PM lagoon: 1060 kg/d
Thus total biomass accumulated in PM lagoon is M = (1.38 ×105
+ 1060t) kg,
where t is operation time with a unit of day
4.3 Ammonia released to water from settled biomass
Assume the rate of ammonia releasing to water from sludge deposit is rN. This
number should be obtained from experiment with sludge from PM zone. Once get this
number, the ammonium released can be calculated as:
MNH4-N = M﹒rN (4)
4.4 Nitrification in water column
Nitrification is expressed by the equation:
OHHNOONH 2324 22 ++→+ +−+
(5)
For nitrification the reaction rate (first order) will be in the range 0.01-0.3 (1/day).
A typical value of 0.05 (1/day) and a temperature coefficient of 1.088 are suggested.

23. 22
From proceeding discussion, it is assumed that aerobic sludge layer comprise 10
percent of total sludge mass. And empirical composition of nitrifying bacteria in biomass
is 8 percent. So highest nitrification is achieved when both of the population and
nitrification rate of nitrifying bacteria reach maximum.
Highest nitrification= M×10%×8%×0.3
4.5 Challenges about mathematical model
At this point, the releasing rate of ammonia from sludge to water needs to be
identified. To increase the accuracy of the rate, I suggest taking sludge from different
layer and measure at different temperature conditions.
In this mathematical model, I initially assume that no ammonia is accumulated in
PM zone. However, this may not be the case in IDEAL operation, especially during the
ammonia rebound period. Thus in next sampling cycle, I recommend taking more water
samples for ammonia measurement in PM zone.
5. Conclusion
5.1 Possible explanations of ammonia rebound
Combining all the discussion above, I proposed two possible explanations for the
period of Dec 2013 to early April during which time the ammonia concentration in PM
zone is low. One explanation is that: decay of biomass and releasing of ammonia takes
place year round. The decay coefficient is temperature dependent, so when temperature
varies, the amount of ammonia released will also vary. The reason why ammonia
concentration in effluent water is observed below 0.05 mg/L from Dec 2013 to early
April is that the released ammonia acts as a substrate for AOB and NOB so that nitrifying

24. 23
bacteria growing in aerobic and anoxic sludge layer take up the released ammonia and
keep the ammonia concentration low.
During the coldest period, January to March, the rate of releasing ammonia to
water was minimized due to thermal dynamics decreased with temperature. The decline
in substrate leads to decrease in the population of nitrifying bacteria. At the same time,
nitrification rate also decreased, or even ceased, because of low temperature inhibition.
So the balance between ammonium released to water and oxidized is used to maintain the
low concentration of ammonium in water.
As for ammonia releasing to water phase, it is believed that because of long
Solids Retention Time (SRT) and long-time settling at bottom without agitation, large
quantities of ammonia are released but most of them are trapped inside the sludge deposit.
The trapped ammonia is slowly released from sludge deposit to water column.
In terms of the sudden increase of ammonia, there are two explanations for it: one
is that: starting from early April, the rising temperature greatly increases the amount of
ammonia released to water. However at this point, nitrifying bacteria have not recovered
from inhibition. They need time to grow on the substrate-ammonia. Then, in this lag
period, ammonia is built up and rebound is observed. But after some time of growing,
according to equation 1, nitrifying bacteria finally catch up to oxidize excess ammonia.
Another cause of increase of ammonia could be internal hydraulics disturbance of
the sludge deposit due to enormous diurnal temperature change, which moves more
solids to the water column. The enormous diurnal temperature change greatly affects the
density of water. Surface water, due to contact with air, has temperature changing faster
than bottom water. From afternoon, when ambient temperature starts to cool down, water

25. 24
of top layer cools down faster than bottom water. Then the colder surface water sinks to
bottom and causes hydraulic disturbance inside PM zone. The ammonia associated with
solids is released to water phase. While solids get removed at the end of PM zone or in
quiescent zone ammonia stays in water and causes ammonia concentration in water to
increase.
5.2 Additional parameters
After the modeling and calculation work, I realized that the lagoon system is
much more complicated than original expected. The data we have right now is not
enough to support the analysis. Thus we need additional parameters to effectively model
the system, and here are what those parameters:
1) Temperature of water and sludge in PM zone.
The temperature we have is ambient temperature and temperature of water in IDEAL
but they are improper to represent the temperature of water and sludge in PM zone.
While it is easy to understand that ambient temperature cannot represent the water
temperature, the discrepancy of operation condition between IDEAL and PM zone
indicates that the temperature in water is slightly different. The temperature of sludge
deposit at the inlet of PM zone is also different from that of water. Therefore, it is
necessary to monitor the temperature of water and sludge in PM zone.
2) Ammonia concentration of effluent water from IDEAL.
Even though the system proves stable and excellent performance during most of the
time and IDEAL is a high-efficiency reactor, without the ammonia concentration of
the effluent water from IDEAL, we are still not fully convinced that excess ammonia

26. 25
only from PM zone. This possibility might be very small but I still recommend
monitor the effluent ammonia from IDEAL.
3) Ammonia concentration of water around sludge deposit in PM zone.
If the ammonia coming into PM zone is zero, the excess ammonia is from sludge
deposit. Through the change of ammonia concentration of the water around sludge
deposit, we can clearly see the trend of ammonia concentration change with
temperature. I suggest measure the concentration under different temperature
conditions.
4) Suspended Solids (SS) concentration near sludge deposit in PM zone from
March to June when temperature starts to increase.
This data can help identify whether the internal hydraulic disturbance is a key factor
to cause ammonia rebound. If it is the case, BioWin simulation may not be suitable.