1

Nitrogen Removal in Wastewater Stabilization Lagoons

By

E. Joe Middlebrooks a, Sherwood C. Reed b, Abraham Pano c

and V. Dean Adams d

Presented at6th National Drinking Water and Wastewater Treatment

Technology Transfer WorkshopKansas City, Missouri 64105

August 2-4, 1999

____________a Environmental Engineering Consultant, 360 Blackhawk Lane,Lafayette, CO 80026; b Principal of Environmental EngineeringConsultants (E.E.C.), Norwich, Vermont; c EnvironmentalEngineer, Ha Oniyah St 21, Rishon-Lezion, Israel; d Professor ofCivil Engineering, University of Nevada, Reno, Reno, Nevada80057.

2

Nitrogen Removal in Wastewater Stabilization Lagoons

E. Joe Middlebrooks, Sherwood C. Reed, Abraham Panoand V. Dean Adams

INTRODUCTION

Stabilization lagoons have been employed for treatment of wastewater for over 3000

years. The first recorded construction of a lagoon system in the United States was at San

Antonio, Texas, in 1901. Today, over 7000 lagoon systems are used in the United States for the

treatment of municipal and industrial wastewater, under a wide range of weather conditions

ranging from tropical to Arctic. Large numbers of lagoon systems are used throughout the

world. The lagoon systems can be used alone or in combination with other wastewater

treatment processes.

More lagoon systems are being planned and constructed every year. The major reasons

for their popularity are the basic simplicity of the concept and the low cost and energy

requirements. Lagoons also are used as a preliminary treatment/storage component in many

land treatment systems. Detention time in most facultative lagoons ranges from about 20 days

to over 150 days depending on the functional intent of the system and the climate. Partial mix

aerated lagoon detention times will vary from 3 to 20 days. Complete mix aerated lagoons

have detention times of 1 to 3 days. All detention times are a function of temperature,

geometry, and other environmental conditions.

The BOD and suspended solids removal capability of lagoon systems has been

reasonably well-documented and reliable designs are possible; however, the nitrogen removal

capability of wastewater lagoons has been given little consideration in system designs until the

3

past 10 years or so. Nitrogen removal can be critical in many situations since ammonia nitrogen

in low concentrations can adversely affect some young fish in receiving waters, and the addition

of nitrogen to surface waters can cause eutrophication. In addition, nitrogen is often the

controlling parameter for design of land treatment systems. Any nitrogen removal in the

preliminary lagoon units can result in very significant savings in land and costs for the final land

treatment site.

FACULTATIVE LAGOONS

Nitrogen loss from streams, lakes, impoundments, and wastewater lagoons has been observed

for many years. Extensive data on nitrogen losses in lagoon systems were insufficient for a

comprehensive analysis of this issue until the early 1980's, and there was no agreement on the

removal mechanisms. Various investigators have suggested algae uptake, sludge deposition,

adsorption by bottom soils, nitrification, denitrification, and loss of ammonia as a gas to the

atmosphere (volatilization). Evaluations by Pano and Middlebrooks (1982), USEPA (1983),

Reed (1984) and Reed, et al. (1995) suggest that a combination of factors may be responsible,

with the dominant mechanism under favorable conditions being volatilization losses to the

atmosphere as shown by the relative size of the arrows in Figure 1.

The USEPA sponsored comprehensive studies of facultative wastewater lagoon systems

in the late 1970's (Bowen, 1977; Hill and Shindala, 1977; McKinney, 1977; and Reynolds et al.,

1977). These results provided verification that significant nitrogen removal does occur in

lagoon systems. Table 1 summarizes the key findings from those studies. These results verify

the consensus of previous investigators that nitrogen removal was in some way related to pH,

detention time, and temperature in the lagoon system. The pH fluctuates as a result of the algae-

carbonate interactions in the lagoon, so wastewater alkalinity is important. Under ideal

4

conditions, up to 95% nitrogen removal can be achieved from facultative wastewater

stabilization lagoons.

Several recent studies of nitrogen removal have been completed, but the quantity of data

are limited. A study of 178 facultative lagoons in France showed an average nitrogen removal

of 60 to 70 percent; however, there was a limited quantity of data from each lagoon system

(Racault, et al., 1993). Wrigley and Toerien (1990) studied four small-scale facultative lagoons

in series for 21 months and observed an 82% reduction in ammonia-N, but an extensive

sampling program similar to those conducted by the USEPA in the late 1970's was not carried

out.

Shilton (1995) quantified the removal of ammonia-N from a facultative lagoon treating

piggery wastewater, and found that the rate of volatilization varied from 355 to 1534 mg/m2-

day. The rate of volatilization increased at higher concentrations of ammonia-N and TKN.

Soares, et al., (1995) monitored ammonia-N removal in a wastewater stabilization

lagoon complex of different geometries and depths in Brazil, and the ammonia-N concentrations

were lowered to 5 mg/L in the maturation lagoons making the effluent satisfactory for discharge

to surface waters. It was found that the ammonia removal in the facultative and maturation

lagoons could be modeled by the equations based on the volatilization mechanism proposed by

Pano and Middlebrooks (1982).

Theoretical Considerations

Ammonia-N removal in facultative wastewater stabilization lagoons can occur through the

following three processes:

• Gaseous ammonia stripping to the atmosphere,

• Ammonia assimilation in algal biomass, and

5

• Biological nitrification.

The low concentrations of nitrates and nitrites in lagoon effluents indicate that

nitrification generally does not account for a significant portion of ammonia-N removal.

Ammonia-N assimilation in algal biomass depends on the biological activity in the system and is

affected by temperature, organic load, detention time, and wastewater characteristics. The rate

of gaseous ammonia losses to the atmosphere depends mainly on the pH value, temperature, and

the mixing conditions in the lagoon. Alkaline pH shifts the equilibrium equation NH3 + H2O ↔

NH4+ + OH- toward gaseous ammonia; whereas, the mixing conditions affect the magnitude of

the mass transfer coefficient. Temperature affects both the equilibrium constant and mass

transfer coefficient.

At low temperatures, when biological activity decreases and the lagoon contents are generally

well mixed owing to wind effects, ammonia stripping will be the major process for ammonia-N

removal in facultative wastewater stabilization lagoons. The ammonia stripping lagoons may be

expressed by assuming a first-order reaction (Stratton, 1968, 1969). The mass balance equation

will be

VdC/dt = Q(Co - Ce) - kA(NH3) (1)

where

Q = flow rate, m3/d;

Co = influent concentration of (NH4+ + NH3), mg/L as N;

Ce = effluent concentration of (NH4+ + NH3), mg/L as N;

C = average lagoon contents concentration of (NH4+ + NH3), mg/l as N;

V = volume of the pond, m3;

k = mass transfer coefficient, m/d;

6

A = surface area of the pond, m3; and

t = time, days.

The equilibrium equation for ammonia dissociation may be expressed as

where Kb = ammonia dissociation constant.

By modifying Equation 2, gaseous ammonia concentration may be expressed as a

function of the pH value and total ammonia concentration (NH4+ + NH3) as follows:

where

pKW = -log KW, and

pKb = -log Kb

Assuming steady-state conditions and a completely mixed lagoon where Ce = C,

Equations 1and 5 will yield the following relationship:

[ ] [ ]

)5(101

)4(

)3(

3

34

pHpKpK

W

bW

CNH

NHNHC

OH

KH

−−

+

−+

+=

+=

=

[ ][ ][ ] ( )2

3

4

NH

OHNHKb

−+

=

7

This relationship emphasizes the effect of pH, temperature (pKW and pKb, are functions

of temperature) and hydraulic loading rate on ammonia-N removal.

Experiments on ammonia stripping conducted by Stratton (1968, 1969) showed that the

ammonia loss-rate constant was dependent on the pH value and temperature (T = 0C) as shown

in the following relationships:

Ammonia loss rate constant ∝∝ e1.57(pH-8.5) (7)

Ammonia loss rate constant ∝∝ e0.13(T-20) (8)

King (1978) reported that only 4% nitrogen removal was achieved by harvesting floating

cladophora fracta from the first lagoon in a series of four receiving secondary effluents. The

major nitrogen removal in the lagoons was attributable to ammonia gas stripping. The removal

of total nitrogen was described by first-order kinetics, using a plug-flow model (Nt = N0 e-0.03t

where Nt = total nitrogen concentration, mg/L, and N0 = initial total nitrogen

concentration, mg/L and t = time, days).

It is well understood that large-scale facultative wastewater stabilization lagoon systems

only approach steady-state conditions, and only during windy seasons will well-designed lagoons

approach completely mixed conditions. Moreover, when ammonia removal through biological

activity becomes significant, or ammonia is released into the contents of the lagoon from

anaerobic activity at the bottom of the lagoon, the expressions for ammonia removal in the

)6(

101

11

1

++

=

−− pHpKpKo

e

bWk

Q

AC

C

8

system must include these factors along with the theoretical consideration of ammonia stripping

as shown in Equation 6.

In the following paragraph, mathematical relationships for total nitrogen removal based

on the performance of three full-scale facultative wastewater stabilization lagoons are developed

considering the theoretical approach and incorporating temperature, pH value, and hydraulic

loading rate as variables. Therefore, rather than using the theoretical expression for ammonia-N

stripping (Equation 6), the following equation is considered for TKN removal in facultative

lagoons:

where

K = removal rate coefficient (l/t), and

f (pH) = function of pH.

The K values are considered to be a function of temperature and mixing conditions. For

a similar lagoon configuration and climatic region, the K values may be expressed as a function

of temperature only. The function of pH, which is considered to be dependent on temperature,

affects the pK, and pKb values, as well as the biological activity in the lagoon. To incorporate

the effect of the pH function on ammonia-N stripping (Equation 6), the pH function was found

to be an exponential relationship. The selection of an exponential function to describe the pH

function was based on statistical analyses indicating that an exponential relationship best

described the data. Also, most reaction rate and temperature relationships are described by

exponential functions such as the Van't Hoff-Arrhenius equation; therefore, it is logical to

( ))9(

1

1

0 pHfKQ

AC

Ce

•+=

9

assume that such a relationship would apply in the application of the theoretical equation to a

practical problem.

Design Models

Data were collected on a frequent schedule from every cell at all of the lagoon systems listed in

Table 1 for at least a full annual cycle. This large body of data allowed quantitative analysis with

all major variables included, and several design models were independently developed. The

following two models have been shown to be the most accurate in predicting nitrogen removal

in facultative lagoon systems. These have been validated using data from sources not used in

model development. The two models are summarized in Tables 2 and 3, and details on the

theoretical development of the models were presented above. Further validation of the two

models can be found in Reed et al. (1995), Reed (1985), USEPA (1983) and Reed (1984). Both

are first order models, and both depend on pH, temperature, and detention time in the system.

Although they both predict the removal of total nitrogen, it is implied in the development of

each that volatilization of ammonia is the major pathway for nitrogen removal from wastewater

stabilization lagoons. The application of the two models is shown in Figure 2, and the predicted

total nitrogen in the effluent is compared to the actual monthly average values measured at

Peterborough, NH. Both of these models are written in terms of total nitrogen, and they should

not be confused with the still valid equations reported by Pano and Middlebrooks (1982) which

are limited to the ammonia fraction. Calculations and predictions based on total nitrogen should

be even more conservative

High rate ammonia removal by air stripping in advanced wastewater treatment depends

on a high (> 10) chemically adjusted pH. The algae-carbonate interactions in wastewater

lagoons can elevate the pH to similar levels for brief periods. At other times, at moderate pH

10

levels, the rate of nitrogen removal may be low, but the long detention time in the lagoon

compensates.

Figure 3 illustrates the validation of both models using the same data from lagoon

systems not used previously. The diagonal line on the figure represents a perfect fit of predicted

versus actual values. The close fit and consistent trends verify that either model can be used to

estimate nitrogen removal. In addition, the models have been used in the design of several

lagoons systems and have been found to work well.

Applications

These models should be useful for new or existing wastewater lagoons when nitrogen

removal and/or ammonia conversion is required. The design of new systems would typically

base detention time on the BOD removal requirements. The nitrogen removal that will occur

during that time can then be calculated with either model. It is prudent to assume that the

remaining nitrogen in the effluent will be ammonia and then design any further

removal/conversion for that amount. If additional land is available, a final step can be used to

compare the provision of additional detention time in the lagoon for nitrogen removal with the

costs for other removal alternatives.

Use of these models is particularly important when lagoons are used as a component in

land treatment systems since nitrogen is often the controlling design parameter. A reduction in

lagoon effluent nitrogen will often permit a very significant reduction in the land area needed

and, therefore, the costs for land treatment.

11

Summary

Nitrogen removal occurs in facultative wastewater stabilization lagoons, and it can be

reliably predicted for design purposes with either of two models presented above. Nitrogen

removal in lagoons may be more cost-effective than other alternatives for removal and/or

ammonia conversion. Nitrogen removal in lagoons used as a component in land treatment

systems can influence the cost effectiveness of the project.

NITROGEN REMOVAL IN AERATED LAGOONS

At a pH value of 8.0, approximately 95 % of the ammonia nitrogen is in the form of

ammonium ion; therefore, in biological systems such as aerated lagoons where the pH values are

usually less than 8.0, the majority of the ammonia nitrogen is in the form of ammonium ion.

Total Kjeldahl nitrogen (TKN) is composed of the ammonia nitrogen and the organic

nitrogen. Organic nitrogen is a potential source of ammonia nitrogen because of the deamination

reactions during the metabolism of organic matter in wastewater.

Ammonia and TKN reduction in aerated lagoons can occur through several processes:

(a) Gaseous ammonia stripping to the atmosphere,

(b) Ammonia assimilation in biomass,

(c) Biological nitrification,

(d) Biological denitrification, and

(e) Sedimentation of insoluble organic nitrogen.

The rate of gaseous ammonia losses to the atmosphere depends mainly upon the pH value,

temperature, hydraulic loading rate, and the mixing conditions in the lagoon. An alkaline pH

value shifts the equilibrium equation NH3 + H2O ↔ NH4+ + OH-

12

toward gaseous ammonia, while the mixing conditions affect the magnitude of the mass transfer

coefficient. Temperature affects both the equilibrium constant and mass transfer coefficient.

Ammonia nitrogen assimilation into biomass depends upon the biological activity in the

system and is affected by several factors such as temperature, organic load, detention time and

wastewater characteristics. Biological nitrification depends upon adequate environmental

conditions for nitrifiers to grow and is affected by several factors such as temperature, dissolved

oxygen concentration, pH value, detention time and wastewater characteristics.

Within bottom sediments under anoxic conditions, denitrification can take place, and

temperature, redox potential and sediment characteristics affect the rate of denitrification. In

well-designed aerated lagoons with good mixing conditions and distribution of dissolved oxygen,

denitrification will be negligible.

USEPA sponsored comprehensive studies of aerated wastewater lagoon systems

between 1978 and 1980 provided information about nitrogen removal in aerated lagoon systems

(Earnest C. M., et al. 1978; Englande A. J. Jr. 1980; Gurnham C. F., et al. 1979;

Polkowski L. B. 1979; Reid G. W.; Russel, J. S., et al., 1980: and Streebin L. 1979). Tables 4

and 6 summarize the key findings from those studies. These results verify the consensus of

previous investigators that nitrogen removal was in some way related to pH, detention time, and

temperature in the lagoon system.

Comparison of equations

Table 5 contains a summary of selected equations developed to predict ammonia

nitrogen and TKN removal in diffused-air aerated lagoons (Middlebrooks and Pano, 1983). All

of the equations have a common database; however, the data were used differently to develop

several of the equations. The "system" column in Table 5 describes the lagoons or series of

13

lagoons that were used to develop the equation. An explanation of the "system" combinations

was presented above. These combinations of data were analyzed statistically, and the equations

presented in Table 5 were selected based upon the best statistical fit of the data for the various

combinations that were tried. The combinations of data are not directly comparable, but the

presentation in Table 5 takes into account the best statistical fit of the data.

A comparison of the hydraulic detention times calculated using the various formulas for TKN

removal show that the maximum deviation between the maximum and minimum detention times

calculated from the equation is 14%. In view of the wide variation in methods used to develop

the various relationships, this is a very small deviation. All of the relationships are statistically

significant at levels higher than one percent. Because of the small difference in detention times

calculated using all of the expressions, there is a good basis to apply any of the relationships in

design of lagoons to estimate TKN removal. Because of the simplicity of the plug flow model

and the fraction removed model, it is recommended that these two be employed with the others

used as a check to ensure adequate removal in the event that unusual loading rates or BOD5

loading rates are encountered.

Using any of the above expressions will result in a good estimate of the TKN removal that is

likely to occur in diffused-air, aerated lagoons. Unfortunately, data are not available to develop

relationships for surface aerated lagoons.

The relationships developed to predict ammonia nitrogen removal yielded highly significant

(1% level) relationships for all of the equations presented in Table 5. However, the agreement

between the calculated detention times for ammonia nitrogen removal differed significantly from

that observed for the TKN data. This variation is not surprising in view of the many

mechanisms involved in ammonia nitrogen production and removal in wastewater lagoons, but

14

this variation in results does complicate the use of the equations to estimate ammonia nitrogen

removal in aerated lagoons.

Statistically a justification exists to use either of the expressions in Table 5 to calculate

the detention time required to achieve a given percentage reduction in ammonia nitrogen.

Perhaps the best equation to use in design to predict ammonia nitrogen removal is the

relationship between the fraction removed and the detention time. The correlation coefficient

for this relationship is higher than the correlation coefficient for the plug flow model, and both

equations are equally uncomplex.

Rich (1996, 1999) has proposed continuous-feed, intermittent-discharge (CFID) basins for

use in aerated lagoon systems for nitrification and denitrification. The systems are designed to use

in-basin sedimentation to uncouple the solids retention time from the hydraulic retention time.

Unlike sequencing batch reactor (SBR) systems, the influent flow is continuous. A single basin

with a dividing baffle to prevent short-circuiting is frequently used.

Some CFID systems have experienced major operational problems with short-circuiting

and sludge bulking; however, by minimizing these problems with design changes the systems can

be made to function properly. CFID design modifications can be made to overcome most

difficulties and details are presented by Rich (1999).

The basic CFID system consists of a single reactor basin divided into two cells with a

floating baffle. The two cells are referred to as the influent (Cell 1) and effluent cell (Cell 2).

Mixed liquor is recycled from the Cell 2 to the headworks to provide a high ratio of soluble

biodegradable organics to organisms and the oxygen source is primarily nitrates. This approach is

used to control bulking. Although some nitrification will occur in the influent cell, the system is

designed for nitrification to occur in the effluent cell. To learn more about the operation of the

15

CFID systems, consult the book by Rich (1999). A brief summary of the design procedures

extracted from Rich (1999) is presented in the following paragraphs.

1. The initial step is the selection of the Monod parameters for nitrification at the design

temperature. Equations 10 and 11 are used to estimate the parameters.

Where µm= maximum specific growth rate, d-1

KN = half-saturation constant for ammonium nitrogen, mg/L

T = water temperature, 0C

2. Next, determine the specific growth rate.

Where N = concentration of ammonium ion, mg/L

O2 = concentration of dissolved oxygen, mg/L

KO2 = half-saturation constant for dissolved oxygen, mg/L

3. Estimate the ratio of nitrifier biomass in Cell 1 to Cell 2.

)11(10

)10(10158.1015.0

944.00413.0

−

−

=

=T

N

Tm

K

µ

( )[ ] )12(2.783.012

2

2

pHOK

O

NK

N

ONm −−

++= µµ

)13(2

1

R

R

N

N

QQ

Q

X

X

+=

16

Where Q = average flow rate through the basin, m3/d

QR = recycle flow rate, m3/d

XN1/XN2 = ratio of nitrifier biomass concentration in Cell 1 to that in Cell 2

4. Estimate the fraction of the solids retention time that will be aerobic. It was assumed

that all nitrification would occur in Cell 2. A proposed operating schedule over the

24-hr cycle must be developed, i.e. four settling and four discharge periods, each

lasting one hour. The fraction of the solids retention time that will be aerobic for

nitrifiers will be 16/48 or 0.33.

5. Determine the solids retention time required to nitrify at T.

Where θs = solids retention time, d

Fs = safety factor

fO2 = fraction of solids retention time that is aerobic to the nitrifiers

XN1/XN2 = ratio of nitrifier biomass concentration in Cell 1 to that in Cell 2

6. Estimate the heterotrophic biomass concentrations in the two cells.

Where XH2 = heterotrophic biomass concentration in Cell 2, mg/L

YH = heterotrophic growth yield, mg biomass/mg CBOD5

)14(

12

12

µ

θ

+

=

N

NO

ss

X

Xf

F

( ) ( )( )( ) )15(

// 12

1

1

102

++

−++=

RR

RssoHH QQVVQ

VQQ

QV

FXSYX

θ

17

S0 = soluble CBOD5 of untreated wastewater, mg/L

Xso = particulate CBOD5 of untreated wastewater , mg/L

F1 = solids decay factor [from table provided by Rich (1999)]

Where XH1 = heterotrophic biomass in Cell 1, mg/L

7. Estimate the inert suspended solids concentrations in the two cells.

Where Xi0, Xi1, Xi2 = inert suspended solids concentrations (both organic and inorganic) in

the influent wastewater, Cell 1 and Cell 2, respectively, mg/L

8. Estimate the MLSS concentrations in the two cells.

XT1 = XH1 + Xi1 (19)

XT2 = XH2 + Xi2 (20)

Where XT1, XT2 = total MLSS in Cells 1 and 2, respectively

9. Estimate power required to keep solids in the two cells suspended. Rich (1999).

For low-speed mechanical surface aerators:

P = 0.004X + 5 (for X≤≤2000 mg/L) (21)

( ))16(102

1R

soHRH QQ

FXSQYXQX H

+

++=

( )

)18(

)17(

2

112

21

21

V

XVQXX

VQQVQ

QVQXX

iiosi

RR

sRioi

−=

+++

=

θ

θ

18

P = 8.125lnX-48.75 (for X>>2000 mg/L) (22)

Where P = power level, W/m3

X = total suspended solids concentration, mg/L

For diffused-air aeration devices:

Qa = 2.257x10-3 +0.244x10-6X-8.482x10-10X2 (23)

Where Qa = air flow rate at standard conditions, m3 air/m3 min

X = total suspended solids concentration, mg/L

10. Estimate value of specific decay rate.

Where kd20 = specific decay rate at 20 0C, d-1

Kd = specific decay rate at T 0C, d-1

11. Estimate aeration power intensities required for the delivery of oxygen by estimating

the oxygen uptake rates.

Where R021 and R022 = O2 uptake rates in Cells 1 and 2, kg/h

( ) )25(05.1

)24(48.020

415.0

20

20

−

−

=

=T

dd

sd

kk

k θ

( ) ( )[ ] ( )( )[ ] ( )

( )2810

2742.157.41016.4

2642.147.11016.4

2

2

2

32

22205

2

100005

1

NV

RP

XkVNNQxR

FXSYXSQxR

OO

HdO

sHsO

=

+−=

+−+=−

−

19

P02 = power intensity, W/m3

12. Determine the aerator capacities based on the volumes of the two cells.

Aerator capacity = p02Q

13. Establish controlling water surface levels in the reactor basin. See Rich (1999) for

details.

14. Establish capacity of decanting device. See Rich (1999) for details.

15. Establish operating cycle in Cell 2 (Effluent Cell). See Rich (1999) for details.

16. Determine the capacity of the mixed-liquor recycle pump.

17. Determine alkalinity that may be needed. It can be estimated by assuming that 7.2 mg

of alkalinity (as CaCO3) are required for each mg of ammonium nitrogen to nitrite.

The above presentation of Rich's (1999) design method for a CFID reactor basin is not

complete in all its detail and is presented to indicate the procedure. Rich (1999) must be

consulted to learn the limitations and constraints placed on the method.

Rich (1999) also has provided information on modifications to the CFID system for

nitrification-denitrification in an aerated lagoon system.

)30(

)29(2

221

w

Ts

TTw

QQCapacityPump

X

XVVXratewastingliquormixedQ

+=

+==

θ

20

Summary

Rich's (1999) method is one way to design for nitrification in an aerated lagoon. The

equations in Table 5 are empirical and may or may not apply to a general design; however, these

equations will serve as an estimate of what might be expected in terms of nitrogen removal.

Designing a lagoon system to nitrify a wastewater is not difficult if the water temperature and

detention time are adequate to support nitrifiers and adequate dissolved oxygen is supplied.

Obviously, providing recycle of the mixed liquor is a significant benefit. As with all treatment

methods, an economic analysis should be performed to determine the choice of a system.

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21

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23

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25

Figure 1. Nitrogen Pathways in Wastewater Lagoons UnderFavorable Conditions.

26

Figure 2. Predicted Versus Actual Effluent Nitrogen,Peterborough, NH.

27

Figure 3. Verification of Design Models

28

Table 1. Data Summary from EPA Facultative Wastewater Pond Studies(Annual Values) (Bowen, 1977; Hill and Shindala, 1977; McKinney, 1977; and Reynolds etal., 1977)

Detention Water Influent Time Temperature pH Alkalinity Nitrogen Removal (d) (oC) (median) (mg/L) (mg/L) (%)

Peterborough, NH 107 11 7.1 85 17.8 433 cells

Kilmichael, MS 214 18.4 8.2 116 35.9 803 cells

Eudora, KS 231 14.7 8.4 284 50.8 823 cells

Corinne, UT 42 10 9.4 555 14.0 461st 3 cells

29

Table 2. Model 1, Nitrogen removal in facultative lagoons-Plug Flow Model (Reed, 1984, 1985, Reed, et al. 1995).

where: Ne= effluent total nitrogen, mg/l

N0 = influent total nitrogen, mg/l

KT =temperature dependent rate constant

KT = K20 (θθ) (T-20)

K20 = rate constant at 20oC = 0.0064

θ = 1.039

t = detention time in system, d

pH = pH of near surface bulk liquid

See references USEPA (1983) or Reed (1984) for typical pHvalues or estimate with:

pH = 7.3e0.0005ALK

where: ALK = expected influent alkalinity mg/L [derived fromdata in EPA (1983) and Reed (1984)]

[ ])6.6(6.600

−+−= pHtKe

TeNN

30

Table 2. (cont.)

Mancini and Barnhart (1976) Equation to determine lagoonwater temperature.

daymrateflowluentQ

CetemperaturluentT

CetemperaturairambientT

mpondofareasurfaceA

where

QA

QTATT

oi

oa

ia

/,inf

,inf

,

,

:

5.0

5.0

3

2

=

=

=

=

++

=

31

Table 3. Model 2, Nitrogen removal in facultative lagoons -Complete Mix Model (Middlebrooks, 1985)

( ) ( )( )

liquidbulksurfacenearofpHpH

CreeswaterpondofetemperaturT

daystimeentiont

LmgnitrogentotalluentN

LmgnitrogentotaleffluentN

eTt

NN

e

pHTe

==

===

−+=

−−

deg,

,det

/,inf

/,

00028.0000576.01

0

6.6042.0080.1

0

32

Table 3. (Cont.)

Mancini and Barnhart (1976) Equation to determine lagoonwater temperature.

daymrateflowluentQ

CetemperaturluentT

CetemperaturairambientT

mpondofareasurfaceA

where

QA

QTATT

oi

oa

ia

/,inf

,inf

,

,

:

5.0

5.0

3

2

=

=

=

=

++

=

33

Table 4. Wastewater characteristics and operating conditions for the five aerated lagoons.

(Earnest C. M., et al. 1978; Englande A. J. Jr. 1980; Gurnham C. F., et al. 1979;

Polkowski L. B. 1979; Reid G. W.; Russel, J. S., et al., 1980: and Streebin L. 1979)

SystemParameter Pawnee Bixby Kosh- Windber North

konong Gulfport

BOD, mg/L 473 368 85 173 178COD, mg/L 1026 635 196 424 338TKN mg/L 51.41 45.04 15.30 24.33 26.5NH3-N mg/L 26.32 29.58 10.04 22.85 15.7Alkalinity mg/L 242 154 397 67 144pH 6.8-7.4 6.1-7.1 7.2-7.4 5.6-6.9 6.7- 7.5

Hydraulic loading rate 0.0213 0.0285 0.0423 0.0663 0.0873Meters/day

Organic loading rate 151 161 87 285 486kg BOD5/hectare-day

Detention time, days 143 107 72 46 22

34

Table 5. Comparisons of various equations developed to predict ammonia nitrogen andTKN removal in diffused-air aerated lagoons. (Middlebrooks and Pano, 1983)

Hydraulic Comparison detention with max

Equation used to estimate Correlation time, detentiondetention time coefficient days time (% Dif.) System

TKN removal

ln Ce/C0=-0.0129(det. time) 0.911 125 5.3 Ponds 1, 2 and 3mean monthlv data

TKN removal rate 0.983 132 0.0 Total systemTKN removal rate=0.809 (TKN loading rate) Mean monthly data

TKN removal rate 0.967 113 14.4 Total systemTKN removal rate=0.0946 (BOD5 loading rate) Mean monthly data

TKN fraction removed = 0.959 129 2.3 Ponds 1, 2 and 30.0062 (detention time) Mean monthly data

Ammonia N removal

ln Ce/C0=-0.0205t 0.798 79 40.2 All dataMean monthly data

NH3-N removal rate 0.968 92 30.3 Total systemNH3-N removal rate = 0.869 (NH3-N loading rate) Mean monthly data

NH3-N removal rate 0.932 132 0.0 Total systemNH3-N removal rate = 0.0606 (BOD5 loading rate) Mean monthly data

NH3-N fraction removed 0.936 121 8.3 Ponds 1, 2 and 3NH3-N fraction removed = 0.0066 (detention time)

35

Table 6. Nitrogen removal in aerated lagoons. (Earnest C. M., et al. 1978; Englande A. J. Jr. 1980; Gurnham C. F., et al. 1979;

Polkowski L. B. 1979; Reid G. W.; Russel, J. S., et al., 1980: and Streebin L. 1979)

LOCATION PAWNEE BIXBY KOSHKONONG

WasteWaterConstit. Mg/L Influent Effluent Influent Effluent Influent EffluentTKN 51.41 5.04 45.04 8.44 15.30 7.60Range 24.93-80.20 2.21-12.74 36.33-64.80 3.04-22.20 6.37-21.34 3.38-13.83

NH3-N 26.32 1.27 29.59 3.46 10.04 5.26Range 12.00-37.00 0.19-5.47 23.71-40.35 0.11-14.76 4.40-16.12 0.66-12.51

N03--N - 0.81 - - 1.66 4.35Range - 0.15-1.54 - - 0.18-5.78 1.14-9.13

N02—N - 0.13 - - 0.08 -Range - 0.02-0.55 - - 0.02-0.17 0.03-1.05

Alkalinity 242 161 154 70 397 382

pH 6.8-7.4 7.8-9.3 6.1-7.1 6.7-9.2 7.2-7.4 7.4-7.9

Temp, 0C - 11.3 - 16.3 - 11.6Range - 3-22 - 5-29 - 1-25

DO, mg/L - 1.9-16.0 - 3.9-13.5 - 7.6-15.3

36

Table 6 (cont.). Nitrogen removal in aerated lagoons.

OPER. COND. PAWNEE BIXBY KOSHKONONG

Hydraulic Loading 0.023 0.0285 0.0423Rate, m/d

Organic Loading 151 161 87Rate, kg BOD/ha/d

Detention Time, d 143 107 72

Power Lever, CFM/MG - 29.8, 17.0 68,28,16

37

Table 6 (cont.). Nitrogen removal in aerated lagoons.

LOCATION WINDBER N. GULFPORT MT. SHASTAWASTEWATER

Constit. mg/L Influent Effluent Influent Effluent Influent EffluentTKN, mg/L 24.33 23.57 26.5 10.8 15.7 11.1Range 13.21-46.00 14.43-34.11 20.6-30.9 7.2-13.3 10.1-20.9 6.8-14.2

NH3-N, 22.85 22.92 15.73 5.1 10.3 5.4Range 12.32-37.24 12.04-32.75 11.6-20.0 0.9-9.7 4.5-17.5 0.5-12.0

N03-N, mg/L - 0.72 - 2.36 0.30 0.73Range - 0.11-2.63 - 0.12-6.46 0.01-0.86 0.04-2.32

N02-N - 0.24 - 0.64 0.15 0.49Range - 0.10-0.66 - 0.04-1.76 0.01-0.950 0.01-2.06

Alkalinity 67 82 144 102 93 74pH 5.6-6.9 6.8-8.5 6.7-7.5 6.8-7.5 6.5-7.6 7.4-9.7

Temp, C - 13.9 - 21.5 - 13.7Range - 2-24 - 11-29 - 2-27

DO, mg/L - 5.7-15.0 - 0.8-9.3 - 10.9-14.0

38

Table 6 (cont.). Nitrogen removal in aerated lagoons.

OPER. COND. WINDBER N. GULFPORT MT. SHASTA

Hydraulic Loading 0.0663 0.0873 0.0806Rate, m/d

Organic Loading 285 486 202Rate, kg BOD/ha/d

Detention Time, d 46 22 21+10 Fac.

Power Level, CFM/MG 34,14,6 7.7, 8.5 HP/MG -