IMPROVED DENITRIFICATION SYSTEM FOR

PINGREE PARK

FINAL PROJECT

CIVE 540

ASHWIN DHANASEKAR

BING BAI

KEERTHIVASAN VENKATAPATHI

May 11, 2011

1

Table of Contents

List of Figures .......................................................................................................................................... 1

List of Tables ........................................................................................................................................... 1

Executive Summary .................................................................................... Error! Bookmark not defined.

Background ............................................................................................................................................. 3

Description of Design Alternatives ........................................................................................................... 4

Design Summary...................................................................................................................................... 8

Additional Considerations........................................................................................................................ 9

References ............................................................................................................................................ 10

Appendix A: Calculation of Denitrification parameters (spreadsheet) ................................................... 11

Appendix B: Calculation of BOD5 for both Denitrification and No Denitrification (spreadsheet) ........... 14

Appendix C: Calculation of proposed weir/orifice design……………………………………………………………….………17

Appendix D: Schematic of WWTP ......................................................................................................... 18

Appendix E: Pingree Park Maps ............................................................................................................ 19

List of Figures

Figure 1: Bardenpho or Predenitrification Design Schematic ................................................................... 4

Figure 2: Recommended Design schematic ............................................................................................. 7

Figure 3: Schematic of Weir/Orifice design ............................................................................................. 7

List of Tables

Table 1: Recycle Ratio Alternatives for sludge vacuum (R1) and sump pump (R2) ................................... 5

Table 2: BOD5 and Nitrate Effluent Concentrations Design flow ............................................................. 6

Table 3: BOD5 and Nitrate Effluent Concentrations Peak flow ................................................................ 6

2

Executive Summary

Pingree Park is the mountain campus of Colorado State University. It is located about 53 miles west of

Fort Collins. It is operational from mid-May to mid-October. It is used by companies for retreats, high

school camps and class for students from CSU and houses around 130 people.

The campus has an existing Wastewater treatment plant with a capacity to treat 20000 gallons per day.

It is housed in a closed roof. This treatment plant has Grit chamber, aeration tank, settling tank, and

chemical addition, rapid mix, settler, sand filter, and leach field.

The influent wastewater has average BOD5 of 888 mg/L, Nitrate 12 mg/L, Ammonia 39mg/L, Phosphorus

(total) 130 mg/L, Dissolved Solids 411 mg/L, Suspended Solids 2543 mg/L. The average flow rate to the

treatment plant is 12500 gal/day with a maximum flow rate of 15150 gal/day.

The present treatment plant achieves removal efficiency 95% for BOD and 95% for TSS. The system is

not very efficient in removing the nutrients and often exceeded their CDPHE PELs regulations. Since they

release the effluent to leach field there is the possibility of containment of the ground water, they have

South Fork river right next to the plant. CDPHE is concerned that releasing the effluent water into leach

field may contaminate the South Fork River which is the head water for Cache Le Poudre River.

Therefore CSU decided to improve the present treatment plant by adding extra treatment unit for

denitrification system. We are focused in optimizing the previous proposal to achieve maximum

denitrification possible. This will be achieved by splitting their present aerobic reactor into an anoxic

chamber and aerobic chamber. The volume ratio between anoxic and aerobic as 1.5, that is aerobic zone

will be designed to have 1.5 times the volume of anoxic zone.

The earlier design had a priority of including a denitrification reactor to meet nitrate effluent standards

of 10mg/L or less. It employed a pre-denitrification process in the form of an aeration basin containing

an anoxic denitrification reactor. The Bardenpho or the Pre-denitrification process requires the recycling

of nitrates, which were produced from the nitrification of ammonia, from the anoxic chamber. The

earlier proposed design did significantly lower effluent nitrate concentrations.

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The current effluent standards are:

In order to meet these standards, we need to optimize it. To address the problem of managing

increased flow rates, we might involve the usage of flow control valves.

Background

Situated in a beautiful location atop hills, Colorado State University’s Pingree Park campus

operates only for a six-month period from May to October each year. The wastewater production rate is

nearly 7800 gallons per day. Since it’s remotely located, Pingree Park is required to process and treat

their own wastewater on-site. It might be a little impractical because of the huge population being

served and a relatively small septic system possessed.

The current system is constituted by an aeration basin followed by two settling basins with a 100% solids

recycle flow back into the aeration basin. Chlorination is employed for disinfection and the treated

wastewater is let into a leach field. Temperature fluctuations are avoided as all reactors are placed

indoors. There is no wasting of cells as the mean cell residence time, θx, is equal to the duration of

operation for the system (normally six months approx.,). This is a unique feature of Pingree Park. The

design of the aeration basin is done in such a way that a hydraulic retention time of approximately 3.5 to

5 days is maintained depending on the influent flow rate. Nitrate removal from wastewater is important

to prevent Eutrophication in surrounding water bodies. It precedes algal blooms which can disrupt the

normal functions of the ecosystem and can deplete oxygen levels in water thereby affecting various

aquatic species.

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Description of Design Alternatives

Pingree Park wastewater facility releases its effluent water to leach field after disinfecting with chlorine.

To keep the nutrient level within regulation limit,it was decided to use predenitrification or bardenpho

process. There current aeration tank is big enough to be split in to two as aeration and anoxic zones.

The plant is currently recycling sludge 10 times there influent flow. With the new configuration they will

be recycling both RML and RAS. This reduces the flow of sludge back in to the basin.

The current aeration basin has a volume of 36855 gallons (39’ X 12’ X 10.5’). The basins are split in such

a way that the aeration tank will have 1.5 times the volume of anoxic tank. This is a typical design for the

bardenpho process. With the new configuration the aeration tank will have a volume of 22005 gallons

(24’ X ’12’ X 10’). The anoxic chamber has a volume of 14850 gallons (15’X12’X11’). With this design

there will be difference of one foot height between anoxic and aerobic chamber. This arrangement is to

allow the water to flow from anoxic to aerobic through a weir by gravity. The two chambers will be

separated by a steel wall that will be at distance of approximately 15 feet from the starting of basin. The

steel wall was chosen to avoid corrosion problem in future and it will be easy to install. This is described

in figure 2 in Appendix B

Figure 1: Typical Bardenpho Process Design Schematic.

The first step in the pre denitrification process is the use of carbon from raw wastewater in the anoxic

zone to convert Nitrate to Nitrogen gas. This process helps in reducing the BOD. The water then flows to

the aerobic zone which is separated by a submerged Weir so as to have a side water depth of one foot

less then the side water depth of anoxic zone. This is to prevent the back flow of water from aerobic

zone to anoxic zone. Recycling Mixed Liquor and Activated Sludge to the anoxic zone is needed for the

denitrification process to take place in the anoxic zone.

Alternatives with regards to the recycle rates R1 (recycled sludge ratio) and R2 (recycled mix

liquor ratio) were developed for the system. Upon visiting the facility it was understood that

the current R1 value was roughly ten times the maximum influent flow rate. This was

determined based on the fact the sludge recycle vacuum pump for the main clarifier was run

Anoxic Denitrification

NO3 N2

Aerobic Carbon Oxidation

NH3 NO3 SC

RAS

RML

5

simultaneously with the aeration pumps that operated 30 to 45 minutes on the hour, 24 hours

a day (total of 12-18 hours/day). So in this case, the recycle rate of the mix liquor suspended

solids (R2) would essentially be negligible as a sufficient amount of liquids would be recycled in

the sludge vacuum pump.

Then we came to know that this pump can be run separately from the aeration system. So in

this case we will be able to save significant energy by reducing the time for which the sludge

pump is operating and install a new pump in the rear of aeration basin for recycling the mixed

liquor.So with the above assumptions, calculations where made utilizing the formulas in

Rittman & McCarty Appendix A for denitrification. The calculations were used to get a effluent

Nitrate value of less than or equal to 5 mg/L

Since the treatment plant does not waste any cells, we will be having a Mean Cell Residence

Time(MCRT) of 150 days at the last working day of the treatment plant. The calculations where

made taking MCRT at four different cases as 25, 75,125,150.The design calculations is made for

MCRT 75 days and design flow of 8272 gallons.

The R1 and R2 are calculated at this MCRT and the duration of operation of pump is calculated

corresponding to different R1 and R2.We used 1HP sump pump with a capacity of 5000 gal/hr

for recycle of mixed liquor. Table 1 shows the different R1 and R2 for current and future design

and peak flows and pumping duration for each of them.

Table 1: Recycle Ratio alternatives for sludge vacuum (R1) and sump pump (R2)

6

Calculations were made for effluent BOD5, Oxygen requirement, power for the system. This is shown in

Table 2 and Table 3. This calculations are made for deisgn flow of 8272 gallons is shown in Table 2 and a

peak flow of 19150 gallons is shown in Table 3. We used a R1 of 5 and R2 of 0.83.

Table 2:Effluent Characteristics for MCRT 75 days and flow 8272 gallons

R1=5 R2=0.83

MCRT NO3 BOD5 P O2

requirement Power days mg/L mg/L mg/L kg/day kw 25 4.13 9.22 1.76 34.5 1.41 75 5 10.56 1.36 38.3 1.56

125 5.21 11.15 1.22 39.4 1.61 153 5.28 11.36 1.18 39.6 1.62

Table 3:Effluent Characteristics for MCRT 75 days and flow 19150 gallons

R1=5 R2=0.83

MCRT NO3 BOD5 P O2

requirement Power days mg/L mg/L mg/L kg/day kw 25 4.13 9.23 1.76 79.9 3.26 75 5 10.56 1.36 89.8 3.67

125 5.21 11.15 1.22 92 3.68 153 5.28 11.37 1.18 92.6 3.78

The red values indicate that those values exceeded the effluent values for nitrate. This happens at

higher MCRT. So to contain the effuent values within 5 mg/L we need to increase the R2 to 1.2.The

comparision between the above tables shows that Nitrate and BOD5 value do not change much

depending on the flow. Oxygen requirement and power increases with increase in flow.

There will be rotary lobe pump in the anoxic zone to get the mixing of the RML and RAS with the raw

wastewater equally. Design mixing power for an anoxic tank is between 0.3HP and 0.5 HP per 1000 cubic

feet. Thus based on the volume of 14850 gallons , a required power of 1HP.

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The design system is shown below. The existing tank is separated into two parts for anoxic zone

and aerobic zone. The size of the anoxic zone is 15’ (L) x 12’ (W) x 11’ (H), and the size of

aerobic zone is 24’ (L) x 12’ (W) x 10’ (H). The volume is 14850 gallons for anoxic zone and

22005 gallons for aerobic reactor, and the ratio is 1:1.48 which is close to the recommended

value 1:1.5.

Figure 2: Design schematic

Denitrification can only occur under anaerobic condition, so a cover (roof) is need for the anoxic

zone. Also for the design of the submerged weir or orifice in the steel wall, we decide to use the

size from previous design. So the size of the weir is 1 inch height and 1.98 feet wide .

Figure 3: Schematic of weir design

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Design Summary

To achieve the effluent N standard, we design a Bardenpho or predenitrification process for

the current wastewater treatment process. This design requires an installation of a steel wall to

divide the existing aeration tank into two zones: anoxic and aerobic zone. The wall is about 15

feet from the influent chamber and 11 feet high, also the overflow weir is needed to allow the

water run from the anoxic zone to aerobic zone. The modified water level is 11 feet in anoxic

zone and 10 feet in aerobic zone.

For the current system the ratio of recycled activated sludge is 10, and also due to an

extremely long mean cell residence time, the calculated ratio of recycled mixed liquor is 0. Since

there should be mixed liquor recycled back from aerobic zone to anoxic zone to maintain the

denitrification system working well, we change the R1 value to 5 and choose R2 value to 0.83.

So a pump is needed to recycle the liquor and we use the pump from previous design, 1 HP

5000gal/hour sump pump being installed near the surface at the end of the aeration chamber.

And the required running time for the sump pump is about 2 hours/day and for the existing

sludge pump is 6.5 hours/day.

The effluent BOD5 and N concentration all meet the new standard from CDPHE by putting

into the proposed Bardenpho process. The design can be easily achieved by modifying the

existing aeration basin and also the maintenance of the design is easy. All of these

modifications can be achieved during the seasons when the treatment system is offline, and it

will turn out to be the most efficient and cost effective way to meet the new discharge

regulations for the Pingree Park.

The materials needed for this design basically is the same as the list from previous design,

and the cost for the design could be estimated based on the materials and equipments.

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Other considerations

The R1 and R2 value chosen for the design is based on the current peak flow and an average

mean cell residence time of 75 days, which will lead to an increase of effluent nitrate

concentration under the actual mean cell residence time of 153 days. So a modification of R2

value is needed to maintain the effluent nitrate concentration under 5mg/L.

This design is focusing on the removal of BOD and nitrate to meet the effluent standard, but

CDPHE also provides the limit for effluent phosphorus concentration, which should be

considered in the future design and modification.

A pilot test may be conducted if possible, and also the cost for the design can be variable,

including the materials, equipment and labors.

The source of activated sludge that is used for both denitrification and nitrification is hard to

determine, so tests on microorganism are essential for choosing the most effective sludge.

Further improvements could be made through consulting experts like Dr. Sharvelle, Dr. Richards

and Susanne Cordery-Cotter.

Also for the end of each open season, tons of sludge needs to treated and currently CSU hires

trucks to haul out the sludge. This could lead to a big cost for the whole system and therefore

more efficient ways to treating the sludge could be considered.

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References

Pingree Park Map, Colorado State University. http://map.colostate.edu/old/oc-

pingree.aspx. Date Accessed: 4/10/2011.

Cordery-Cotter, Susanne. Interview, Site Visit: 12 April 2011.

Kroemer, Rex. Interview, Site Visit: 12 April 2011.

Rittman, B. E., and McCarty, P. L. Environmental Biotechnology: Principles and

Applications. Boston: McGraw-Hill, 2001.

Colorado Department of Public Health and Environment.

http://www.cdphe.state.co.us/regulations/wqccregs/index.html, Date Accessed:

4/10/2011.

Qian Liang, Ian Maycumber and Thomas Walsh. Denitrification reactor design for

Pingree Park. Colorado State University, Fort Collins, CO. May 2009.

Sharvelle, Dr. Sybil. Class Lectures. CIVE 540: Advanced Biological Wastewater

Processing, “Nitrification.” Colorado State University, Fort Collins, CO. April 2011.

Sharvelle, Dr. Sybil. Class Lectures. CIVE 540: Advanced Biological Wastewater

Processing, “Denitrification.” Colorado State University, Fort Collins, CO. April

2011.

11

Appendix A: Calculation for current system without denitrification

Note: Volume was given 36855 gallons, and mean cell residence time was actually 153 days.

Example of the calculation was based on the current design flow Q=8272 GPD, influent BOD5 is 888 mg/L.

Step 1 – 12:

BOD Removal without Denitrification (R=10)

Current design flow

Q = 8,272 gal/day

Step 1&3 (Given Values): Q = 0.008272 MGD

S0 = 888 mg/L BODL

Se = 18 mg/L BOD5

SS = 18 mg/L

To = 18 Co

Table 3.1

Step 2 (Table 3.1): q = 23.58 g BODL/g VSS-d q20 = 27 g BODL/g VSS-d

b = 0.13 /d b20 = 0.15 /d

fd = 0.8

Y = 0.45 gVss/g BODL

K = 10 mg BODL/L

Step 4: [qxmin]lim 0.095 days

Smin = 0.125 mg BODL/L

SF = 30

Step 5: qx = 2.86 days

qx (rounded)= 153 days

Step 6: Se = 0.131 mg BODL/L

Step 7, Table 6.2: MLSS = 3000 mg MLSS/L

Xv = 3780.74 mg MLVSS/L

Xi0 = 15 mg VSS/L

q = 4.46 days q = 4.46 days

Step 8: V = 0.03686 MG V = 36855 gal

Xa = 652 mg/L

Step 9: Inorganic Sol = 687 mg/L

MLSS = 4888 mg MLSS/L

Step 10: DXss/Dt = 4 Kg MLSS/day

DXa/Dt = 1 Kg/day

DXv/Dt = 3 Kg MLVSS/day

(DXv/Dt)biol = 3 Kg MLVSS/day

Step 11: Xve = 15 mg VSS/L

Xae = 2.59 mg/L

Xsse = 11.90 mg MLSS/L

Xvr = 10,000 mg VSS/L

Step 12: Q = 31268.16 L/day

Qw = 0 L/day

Qw = 0.0000 MGD

Mass rate = 0 Kg VSS/day

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Step 13 – 18 (cont.)

Table 3.1 from Environmental Biotechnology textbook.

Step 13: N = 11.789 mg N/L

Typical

SMP

Values

used:

P = 2.377 mg P/L k1 0.12 g CODp/g CODs

Step 14: rut = -199.28 mg BODL/L-d k2 0.09 g CODp/g VSSa

UAP = 2.040 mg COD/L qUAP 1.8 g CODp/g VSSa

BAP = 102.577 mg COD/L qBAP 0.1 g CODp/g VSSa

SMP = 104.617 mg COD/L KUAP 100 g CODp/L

Step 15: VSS = 21.3 mg COD/L KBAP 85 g CODp/L

CODe = 126.0 mg COD/L

VSSa = 2.938339 mg BODL/L

BODL = 107.69 mg BODL/L

BOD5 = 15.91 mg BOD5/L

Step 16: R = 10.000

QR = 0.083 MGD

Step 17: O2 Input = 28432138 mg/day

O2 Output = 8163624 mg/day

O2 Uptake = 20.26851 kg/day

Step 18: SOTE = 2 Kg O2/KW-hr

a = 0.7

b = 0.95

Cg = 0.168 atm

Cl* = 7.74 mg/l

Cl = 2 mg/l

FOTE = 0.76 Kg O2/KW-hr

Power = 1.11 KW

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Equations used for calculation

Q = 8272 gal/day

Step 1&3 (Given Values):Q = =D3/10^6 MGD

S0 = 888 mg/L BODL BODL0 = =D5/0.68 mg BODL/L

Se = 18 mg/L BOD5

SS = 18 mg/L

To = 18 Co

Table 3.1

Step 2 (Table 3.1):q = =I10*(1.07)^(D8-20) g BODL/g VSS-d q20 = 27 g BODL/g VSS-d

b = =I11*(1.07)^(D8-20) /d b20 = 0.15 /d

fd = 0.8

Y = 0.45 gVss/g BODL

K = 10 mg BODL/L

Step 4: [qxmin]lim =(D13*D10-D11)^-1 days

Smin = =D14*D11*D15 mg BODL/L

SF = 30

Step 5: qx = =(D17*D15) days

qx (rounded)= 153 days

Step 6: Se = =D14*(1+D11*D19)/(D19*(D13*D10-D11)-1) mg BODL/L

Step 7, Table 6.2:MLSS = 3000 mg MLSS/L

Xv = =(D19/D24)*(D23+(D13*(D5-D20)*(1+(1-D12)*D11*D19))/(1+D11*D19))mg MLVSS/L

Xi0 = 15 mg VSS/L

q = =H24 days q = =H25/D3 days

Step 8: V = =H25/10^6 MG V = 36855 gal

Xa = =(D19/D24)*D13*(D5-D20)/(1+D11*D19) mg/L

Step 9: Inorganic Sol = =20*(D19/D24) mg/L

MLSS = =D22+D22*(10/90)+D27 mg MLSS/L

Step 10: DXss/Dt = =(D28*H25*3.785/D19)/10^6 Kg MLSS/day

DXa/Dt = =(H25*D26/D19*3.785)/10^6 Kg/day

DXv/Dt = =D22*D25/D19*3.78 Kg MLVSS/day

(DXv/Dt)biol = =D31-D3*3.785*D23/10^6 Kg MLVSS/day

Step 11: Xve = 15 mg VSS/L

Xae = =D33*(D26/D22) mg/L

Xsse = =D33*D21/D22 mg MLSS/L

Xvr = 10000 mg VSS/L

Step 12: Q = =D4*3.78*10^6 L/day

Qw = 0 L/day

Qw = 0 MGD

Mass rate = 0 Kg VSS/day

Step 13: N = =0.124*D32*10^6/D37 mg N/L

Typical

SMP

Values

used:

P = = 0.025*D32*10^6/D37 mg P/L k1 0.12 g CODp/g CODs

Step 14: rut = =-(D5-D20)/D24 mg BODL/L-d k2 0.09 g CODp/g VSSa

UAP = =-(I44*D26*D24+I46+I42*D43*D24)/2+(((I44*D26*D24+I46+I42*D43*D24)^2-4*I46*I42*D43*D24)^0.5)/2mg COD/L qUAP 1.8 g CODp/g VSSa

BAP = =-(I47+(I45-I43)*D26*D24)/2+(((I47+(I45-I43)*D26*D24)^2+4*I47*I43*D26*D24)^0.5)/2mg COD/L qBAP 0.1 g CODp/g VSSa

SMP = =D44+D45 mg COD/L KUAP 100 g CODp/L

Step 15: VSS = =D33*1.42 mg COD/L KBAP 85 g CODp/L

CODe = =D20+D47+D46 mg COD/L

VSSa = =D34*D12*1.42 mg BODL/L

BODL = =D20+D49+D46 mg BODL/L

BOD5 = =D20*0.68+D49*0.4+D46*0.14 mg BOD5/L

Step 16: R = 10

QR = =D4*D52 MGD

Step 17: O2 Input = =D37*D5+1.42*D37*D23 mg/day

O2 Output = =D37*D20+D37*D46+1.42*D31*10^6 mg/day

O2 Uptake = =(D54-D55)/10^6 kg/day

Step 18: SOTE = 2 Kg O2/KW-hr

a = 0.7

b = 0.95

Cg = =0.21*0.8 atm

Cl* = =D60/(10^(0.914-(750/(273+D8)))) mg/l

Cl = 2 mg/l

FOTE = =D57*1.035^(D8-20)*D58*(D59*D61-D62)/9.2 Kg O2/KW-hr

Power = =D56/D63/24 KW

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Appendix B: Calculation for denitrification Note: For current system with R1=10

Example of the calculation was based on the current design flow Q=15150 GPD, influent BOD5

is 888 mg/L, TKN is 50 mg/L, and effluent nitrate is 5.0 mg/L. Mean cell residence time is 75

days.

When MCRT=75 days

Choose: Given:

MCRT 75 days BOD50 888 mg/L

fs (nit) 0.13 (Table 10.3) BODL0 1306 mg/L

g BODl/g NO3-N 3.21 (Table 10.3) TKN050 mg/L

R1 10 Q 15150 GPD

fs0 (nit) 0.11 Q 57267 L/day

b (nit) 0.1 /day (NO3)2 5 mg/L

fs0 (aer) 0.5 Xi 15 mg/L

b (aer) 0.13 /day

Variables: Term1 Term2

(NO3-)23.1175512 mg/L 1.6E-06 1963861

BODL1

104.125668 mg/L

R2 0

Calculated

fs (aer) 0.1372093

fs (nit) 0.030186

Y (aer) 0.0968698 g VSS/g BODL

Y (nit) 0.083 g VSS/g BODL

Y (denit) 0.08 g VSS/g BODL

∆Xv/∆t (aer) 6353941 mg/d

∆Xv/∆t (den) 735308.28 mg/d

∆Xv/∆t (nit) 164695.5 mg/d

Sludge loss rate ∆Xv/∆t (tot) 8112950 mg/d

V = 36855 gallons

HRT q = 2.432673 days

Xv = 4367.69 mg VSS/d

Xvr = 4790.292 mg VSS/d

waste flow ratio Rw = 0.029574 (should be 0 actually)

∆O2/∆t = 61.66056 kg/d

15

Required R2=0 to achieve the target nitrate value of 5 mg/L. Note: For design system with R1=5 and R2=0.83

Example of the calculation was based on the current design flow Q=15150 GPD, influent BOD5

is 888 mg/L, TKN is 50 mg/L, and effluent nitrate is 5.0 mg/L. Mean cell residence time is 75

days.

When MCRT=75 days

Choose: Given:

MCRT 75 days BOD50 888 mg/L

fs (nit) 0.13 (Table 10.3) BODL0 1306 mg/L

g BODl/g NO3-N 3.21 (Table 10.3) TKN050 mg/L

R1 5 Q 15150 GPD

fs0 (nit) 0.11 Q 57267 L/day

b (nit) 0.1 /day (NO3)2 5 mg/L

fs0 (aer) 0.5 Xi 15 mg/L

b (aer) 0.13 /day

Variables: Term1 Term2

(NO3-)25.0006588 mg/L 2.6E-06 1955926

BODL1

177.497929 mg/L

R2 0.83

Calculated

fs (aer) 0.1372093

fs (nit) 0.030186

Y (aer) 0.0968698 g VSS/g BODL

Y (nit) 0.083 g VSS/g BODL

Y (denit) 0.08 g VSS/g BODL

∆Xv/∆t (aer) 6725222.9 mg/d

∆Xv/∆t (den) 428684.73 mg/d

∆Xv/∆t (nit) 164030.03 mg/d

Sludge loss rate ∆Xv/∆t (tot) 8176943 mg/d

V = 36855 gallons

HRT q = 2.432673 days

Xv = 4402.142 mg VSS/d

Xvr = 5254.013 mg VSS/d

waste flow ratio Rw = 0.027177 (should be 0 actually)

∆O2/∆t = 64.72327 kg/d

16

Table 10.3 from Environmental Biotechnology textbook.

17

Appendix C: Calculation of proposed weir/orifice design

12 ft

12 ft

1 in (height)

Water level of anoxic tank

Water level of aeration tank

11 ft

10 ft

Orifice2.5 ft

Figure 1: Schematic of Weir/Orifice design

The weir/orifice should be designed to have the capacity to allow the maximum flow to go through,

which is the sum of the inflow of the wastewater plus the recycle flow from the effluent of the aeration

tank. The maximum Inflow rate is 19150 gpd, and the maximum recycle rate is R1=10.

Qtotal=Qmax+RQmax

To determine the dimension of the orifice, we design a tentative value of maximum flow velocity as 1

ft/s. Determine the area of the orifice: A=Q/V

Table 4: Calculations of Orifice

The designed dimension of the orifice is 1 inches

high and 1.96 feet wide.

The position of the orifice determines the water

level of the anoxic tank. It is designed that 1 foot

difference between the water surface and the

upper end of the tank.

18

Appendix D: Schematic of WWTP

RML

19

Appendix E: Pingree Park Maps