WATER POLLUTION CONTROL RESEARCH SERIES
17050 DVO 10/71
Supplementary Aeration
of Lagoons
in Rigorous Climate Areas
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes
the results and progress in the control and abatement
of pollution in our Nation's waters. They provide a
central source of information on the research, develop-
ment, and demonstration activities in the Environmental
Protection Agency, through inhouse research and grants
and contracts with Federal, State, and local agencies,
research institutions, and industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications
Branch, Research Information Division, Research and
Monitoring, Environmental Protection Agency, Washington,
D.C. 20460.
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SUPPLEMENTARY AERATION OF LAGOONS
IN RIGOROUS CLIMATE AREAS
Robert L. Champlin
Associate Professor
Department of Civil Engineering
University of Wyoming
Laramie, Wyoming 82070
for the
ENVIRONMENTAL PROTECTION AGENCY
Project #17050 DVO
October 1971
For sule by tile Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 75 cents
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents neces-
sarily reflect the views and policies of the
Environmental Protection Agency, nor does mention
of trade names or commercial products constitute
endorsement or recommendation for use.
n
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ABSTRACT
A field investigation, using a pilot scale unit, was carried out to
determine the effects of supplementary aeration on Waste Stabilization
Lagoon performance. The tests were conducted at Laramie, Wyoming during
the winter and spring months. The climate can be considered rigorous
and lagoon performance indicative of low temperatures and high altitudes.
Both complete mix and batch experiments were conducted. Air flow was
constant, but loading rates, both hydraulic and process were changed from
160 Ibs. five-day BOD/acre/day (0.725 Ibs./I,000 ft 3/daY) to 90° 1bs-
five-day BOD/acre/day (4.08 Ibs./I,000 ft 3/day). Loading below about
8 Ibs./I,000 ft 3/day can be considered as supplementary aeration. The
air supplied by the INKA system performed the two functions of mixing and
aerating the sewage.
The BOD reduction varied from 72% to 85% under three different loadings.
The temperature of the aerated sewage was below 12°C. Solids removal was
significant. No settleable solids resulted from the system, indicating no
bioflocculation. The change in total bacterial counts were roughly
proportioned to the change in loading.
Tests on a second cell, functioning as a batch process, indicated increase
of oxygen levels to saturation values. Significant algae production also
occurred at temperatures of 6°C. Coliform bacteria were reducted to about
10 per ml in the second cell. Total bacteria counts remained about the
same as indicated in first cell tests.
This report was submitted in fulfillment of Project No. 17050 DVO, under the
partial sponsorship of the Environmental Protection Agency.
iii
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CONTENTS
Section Page
I Conclusions 1
II Recommendations , 3
III Introduction - 5
IV The Pilot Aerated Lagoon 13
V Operational Features of the Pilot Lagoon 21
VI Results - The Aerated Pilot Lagoon 31
VII Summary and Conclusions ,. 59
VIII Acknowledgments 71
IX References 73
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FIGURES
Number Page
1 Operational Features of Lagoons 6
2 Location Map 8
3 Dissolved Oxygen in Laramie Lagoon 10
4 BOD Reduction in Laramie Lagoon 11
5 Detention Structure 14
6 Hydraulic System 15
7 Aeration System 17
8 Aeration and Hydraulic System 19
9 Hydraulic Flow 20
10 Flow Through Curve-Dye Test 23
11 Sampling Stations in Pilot Lagoon 2:
12 DO and BOD Levels in Pilot Lagoon at 320 Ibs./Acre/
Day Loadi ng 26
13 DO and BOD Levels in Pilot Lagoon at 990 Ibs./Acre/
Day Loadi ng 27
14 36 Day BOD Curve for Laramie Municipal Sewage 29
15 Effluent BOD and Temperature in the Pilot Lagoon 34
16 Effluent BOD Reduction and Temperature in the Pilot Lagoon.. 35
17 Effluent DO and Temperature in the Pilot Lagoon 36
18 Dissolved Oxygen Deficiency vs. Loading Intensity 38
VI
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FIGURES
Number Page
19 Fl ow Pattern 39
20 Effluent BOD (5-day 20°C) vs. Loading Intensity 53
21 Percent Reduction of Effluent BOD (5-day 20°C) vs. 54
Loading Intensity
22 Air and Lagoon Temperature (°C) Loading Intensity 55
23 Total Bacteria and Coliform Counts vs. Loading Intensity... 56
24 Dissolved Oxygen and Oxygen Saturation Values vs. Loading.. 57
Intensity
Vll
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TABLES
Table No. Page
1 Loading Intensity and Detention Time (First Cell) .......... 41
2 Steady State Test Results, Aerated Lagoon Loading -
Equals 160 1 bs. /Acre/Day. - ............................... 43
3 Steady State Test Results, Aerated Lagoon Loading -
Equals 160 Ibs. /Acre/Day ................................. 44
4 Steady State Test Results, Aerated Lagoon Loading -
Equals 320 Ibs ./Acre/Day ................................. 47
5 Steady State Test Results, Aerated Lagoon Loading -
Equals 320 1 bs ./Acre /Day ................................. 48
6 Steady State Test Results, Aerated Lagoon Loading -
Equals 900 Ibs. /Acre/Day ................................. 50
7 Steady State Test Results, Aerated Lagoon Loading -
Equals 900 Ibs. /Acre /Day ................................. 51
8 Summary of Average Biochemical Oxygen Demand
Aerated Pilot Lagoon - First Cell ........................ 60
9 Total Bacteria and Coliform Counts - First Cell ............ 61
10 Summary of Average Physical Test Results
Aerated Pilot Lagoon - First Cell ........................ 62
11 Summary of Average Chemical Test Results
Aerated Pilot Lagoon - First Cell ........................ 63
12 Summary of Average Biochemical Oxygen Demand
Aerated Pilot Lagoon - Second Cell ....................... 65
13 Total Bacteria and Coliform Counts -
Second Cell .............................................. 66
14 Summary of Average Physical Test Results
Aerated Pilot Lagoon Second Cell ....................... 68
15 Summary of Average Chemical Test Results
Aerated Pilot Lagoon - Second Cell ....................... 69
Vlll
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SECTION I
CONCLUSIONS
1. Modification of existing lagoon systems can be accomplished in order
to exert more positive control.
2. Supplementary aeration loading indicated high efficiencies of BOD
removal even at low temperatures.
3. Aeration provided both mixing and oxygen in order to increase
metabolism rates.
4. No settleable solids were found in the effluent from the aerated
system.
5. Series operation will dampen variations in quality parameters,
provide for shock loading and reduce coliform count to minimum
levels.
6. Loading below 320 Ibs./Acre/Day and secondary cell operation
produced significant algal growth even at temperatures around 6oc.
7. Short detention periods take advantage of the warmer influent
temperatures in order to satisfy easily oxidized organic material.
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SECTION II
RECOMMENDATIONS
Algae production seems to occur in many environs of treatment and after-
growth. More research should be extended into removal methods and growth
factors.
Present aeration equipment is designed to both mix and aerate the sewage.
In order to perform both functions neither is maximized. Separation of
functions and maximizing of separate efficiencies needs development.
A standarized test procedure or test location, preferably under severe
conditions, for evaluation of aeration equipment is needed.
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SECTION III
INTRODUCTION
One of the most popular sewage treatment units in the western and mid-
western United States is the sewage lagoon. The number of these units
increased from about 1,400 in 1960 to 3,500 in 1968 (1). There are
several reasons why the lagoon is a popular treatment unit, especially
with the smaller communities. First, the capital expense for construction
is very low compared with other forms of treatment. It does require,
however, a large land area near the community. Second, little supervision
of the process is required. Daily inspection checks generally include
water levels, lagoon color, odor, weed control, and hydraulic units.
Third, supervisory personnel require little training. There is a critical
lack of trained sewage treatment operators, especially in small communities.
Because of this shortage of trained operators, state and city officials
have promoted use of a treatment system requiring little technical
knowledge - the sewage lagoon.
There are several overlapping classification systems for lagoons. A flow-
through Waste Stabilization Lagoon, classified as a lagoon that treats raw
sewage (2), was used for comparison purposes in this project. A Waste
Stabilization Lagoon can operate in three different or combined ways.
This is illustrated in Figure 1.
Under the best operating conditions (sufficient oxygen = aerobic, Figure
la), a quasi-steady state symbiotic condition exists between heterotrophs
and autotrophs. It is not a true steady state condition because at night
or during reduced sunlight periods the autotrophs (algae) are reduced to
a heterotrophic cycle increasing the demand for oxygen. In fact an excess
of oxygen must be gained during the afternoon in order that the increased
oxygen demand of the night can be met. If sufficient oxygen is not present
the system approaches anaerobic conditions in the early morning hours.
With this condition it is possible that a reduction in autotrophic activity
will occur during the daylight hours and recovery to full aerobic conditions
during daylight hours will be retarded.
Under the least acceptable conditions (no oxygen = anaerobic, Figure Ic),
there is insufficient physical or autotrophic activity to maintain or
satisfy the oxygen demand. Under these conditions obnoxious odors are
given off, a poor effluent is produced, and public reaction is rapid.
Under conditions of varying load or varying sunlight an intermediate state
(variable oxygen = facultative - Figure lb) can exist. This condition can
produce biochemical reactions of both an aerobic and anaerobic nature.
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Complex
organics
+ 02
organic
acids
H0S ~
— CO
2 '
so4-2
Light = Algae+02
Nutrients
Figure la Aerobic Lagoon
ice
aerobic zone
oaded./''
anaerobic zone
moderately overl
insufficient mixing,
limited algae, or
reduced sunlight
sludge
Figure Ib Facultative Lagoon
Complex
organics
organic _
acids
mercaptans
peptides -
C02 + CH4
H2S
sludge
Figure Ic Anaerobic Lagoon
Figure 1 Waste Stabilization Lagoon - Reactions
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At the present time design loading criteria for flow-through Waste Stabiliza-
tion Lagoons varies from 50 Ibs. of five-day BOD per acre in the southern
states to about 15 Ibs. of five-day BOD per acre in the northern states.
This reduced loading is used in order to minimize problems of odor due to
anaerobic conditions. This minimizing generally results in about one to
three weeks of odor after ice break-up in the spring. In the past, public
reaction to this odor was unsatisfactory but not sufficient to finance a
better treatment system.
This public apathy has changed. Now there is public demand for water
quality in our streams and lakes, a push by hundreds of groups for better
sewage treatment and a realization among ourselves as design engineers that
better positive-control treatment systems are necessary.
If we consider all indices of water quality, in addition to odor, there are
some decided drawbacks to lagoon-type treatment. First, under the best
operating conditions (balance of heterotrophs and autotrophs), few Waste
Stabilization Lagoons (except holding ponds = percolation and evaporation)
remove the algal biomass from the effluent. This biomass is approximately
equivalent to the influent organic mass. The algal biomass is a more
stable organic form and records a lower five-day BOD value but ultimately
an equal or greater total demand for oxygen is recorded. This demand
occurs at a slower rate and over a long stretch of the river, but it does
occur. In effect a rapid demand waste has not been treated - we simply
changed it to a slower demand waste and passed it on down the river.
Many people test the BOD of the effluent after filtering out the algae and
record this as the efficiency of the treatment. This is a delusion. There
have been suggestions of using the algae as a treatment technique for
removal of nutrients from the sewage (3). Algae, in effect, do remove the
excess phosphate from sewage but at present no effective, economical algae
removal method has been found.
Considering all the indices of quality, there is a decided pollution of
the river downstream from the lagoon. The river is green, sludge banks
form, decomposition occurs, poisoning of livestock can occur from some
toxic algae forms, and a section of the river is lost for community
aesthetic enjoyment.
Second, if the balanced aerobic system could be considered sufficient
treatment, its state is indeed a fragile one. Its existence depends
entirely on climatic and atmospheric conditions. This lack of positive
control produces other conditions over the year, especially in the northern
states, that are far from acceptable.
Testing and evaluation of a flow-through Waste Stabilization Lagoon were
conducted at Laramie, Wyoming (Figure 2). These ponds operate in parallel
and series as shown. The ponds were loaded at an average rate of 35 Ibs.
of five-day BOD per acre. These ponds have since been modified with
addition of supplementary aeration equipment.
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Waste Stabilization Lagoon
0123
Scale V' = 1 mile
Figure 2 Location Map
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In the Laramie area, a northern climate, lagoons become thickly covered
with ice during the winter. Photosyntheses and reaeration are insufficient
to maintain aerobic conditions (sufficient oxygen) and the slower anaerobic
process becomes predominant (Figure 3). The colder temperatures during the
period further reduce the microorganisms' activity. Since the loading
rate is fairly constant during the year, the lagoon is overloaded in the
winter. This results in the formation of a sludge blanket of only partially
treated sewage deposited on the lagoon floor and only about 50% BOD removal
efficiency in the effluent (Figure 4).
In the spring after the ice breaks up, the more active aerobic conditions
prevail at the surface but the benthal deposits as well as the normal
loading must be metabolized. Strong winds, lagoon overturn or obnoxious
gas release can resuspend the benthal deposits causing an excess demand
for oxygen and the lagoon will again turn anaerobic. This is reflected
in the dissolved oxygen values during March on Figure 3. This phenomena
can occur for several weeks until the oxygen production is greater or
equal to the demand. In effect the summer period is used to treat part
of the winter load. The lagoon changes from completely aerobic in late
summer to completely anaerobic in winter with facultative processes in
intermediate times.
Effluent variables from this type of Waste Stabilization Lagoon vary from
color = bright green, five-day BOD = 40 ppm (80% efficiency), and saturated
with oxygen in summer to color = brown, five-day BOD = 100 ppm (50%
efficiency), and no oxygen in winter. The winter effluent carries an
additional problem in the western states. During the winter, minimum
stream flow occurs in our streams. This also is the period where the
quality of lagoon effluent is the poorest. In some cases the entire
stream flow consists of effluent from the lagoon. Significant degradation
of the stream occurs with fish death, organic deposits on the river bed
and the odor nuisance spread downstream.
In order to partially counteract the effects of ice cover and low tempera-
ture, to maintain aerobic conditions throughout the winter months, and to
exert some positive control on the system, the technique of supplementary
mechanical aeration was investigated. Although mechanical aeration
devices of many kinds have been used as methods for supplying additional
oxygen to overloaded treatment units, little research has been done on
their efficiency in rigorous climates. The research presented here
identifies several variables that affect performance of an aerated lagoon
in a rigorous climate. The research was conducted on a pilot scale aerated
lagoon located near Laramie, Wyoming, adjacent to the city sewage lagoon
system (Figure 2).
Laramie, Wyoming, is a small college town (23,000 population) located in
southeastern Wyoming at an elevation of 7,200 feet. Air temperatures
range from -200F to 90°F during the year. The high altitude and variable
climate are ideal for pilot scale studies of biological treatment systems.
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OPEN
FORMING
ICE COVER
OPENING
en
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CD
X
O
O
to
•r-
O
11 -
10 -
9
8
7
6
5
4
3
2 -
1 -
0
October ' November ' December I January I February I March
Figure 3 - Dissolved Oxygen in Laramie
Lagoon's Effluent
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OPEN
TQRMINGL
ICE COVER
OPENING
cioo -,
I 75 ^
1 50
§ 25
CQ
0
OctoberINovemberI DecemberIJanuary
I February I March
20 -I
c
13
£ 10
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0
October
November
December
January
February
March
Figure 4 - BOD Reduction and Temperature in the
Laramie Lagoon's Effluent
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SECTION IV
THE PILOT AERATED LAGOON
This project was initiated to indicate possible modifications of present
Waste Stabilization Lagoon design in order to improve treatment efficiency.
This required incorporation of several operational features in the design
of the pilot lagoon. First, the system must treat average raw sewage from
the city collection system. Second, in order to vary loading rates over
the supplementary aeration range and still secure a representative sample
over the total time period, a variable timing device was required on the
influent pump. Third, the severe icing condition required an aeration
system which introduced the air under the ice and was not affected by the
ice. Fourth, the unit must be large enough to reduce or eliminate possible
scale-up effects.
Construction of the pilot lagoon began in June of 1968 and was substantially
complete by the following October. The pilot unit was located adjacent to
the City of Laramie's lagoon system (Figure 2). The pilot lagoon used in
this study consists of four major components. They are the detention
structure, the hydraulic system, the aeration system, and the baffle system.
The Detention Structure
The lagoon was formed by a rectangular, earth-fill dike with a berm of
five feet, face slopes of three to one and backslopes of two to one. The
bottom dimensions of the lagoon were 150 feet by 75 feet. The lagoon was
designed to operate at a water level of about five feet. The aeration
system required a depth of five feet for proper operation. A schematic
diagram of the completed pilot lagoon is shown in Figure 5.
After construction of the dike, attempts were made to fill it with sewage.
However, due to the high permeability of the earth fill and lagoon floor,
seepage rates were unacceptably high. In order to seal the lagoon, a
vinyl plastic membrane lining was used. This covered the bottom, sides
and berm. No further seepage problems were encountered.
The Hydraulic System
The hydraulic system consists of influent piping, a centrifugal sewage
pump, a discharge line to the lagoon through a measuring weir and outlet
structure, an effluent weir and discharge piping (see Figure 6). An 18-
inch city sewer line was used as a source of raw sewage. This 18-inch
city sewer line conducts sewage to the city lagoon system. This line
13
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Figure 5 Detention Structure
14
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--«< ft—Manhole
Pit
Influent Line
3" Plastic
Jorth
8" Steel Header
Compressor House
Influent Weir
Influent Lines
6" Effluent Line
^XxParshall Flume
[Dlnstrument House
Waikway
Effluent Weir
Aerators
- Baffles
1" = 60 feet
0 20 40 60 80
Figure 6 Hydraulic System
15
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makes a sharp turn at a manhole near the pilot lagoon. A three-inch
steel pipe was tapped into the bottom of the line at the manhole and
connected to the centrifugal pump. This allowed a constant static head
on the pump. An automatic shutoff device was installed which shuts the
pump off if the pressure on the discharge side falls below a preset value.
In order to vary the loading applied to the lagoon and still maintain a
representative sample from the city sewage system, a timing system was
connected to the centrifugal pump. This allowed the pump to operate at
periods of varying times and then shut off. By changing the time of
pumping, the rate of hydraulic loading was changed. The pumping time
varied from five minutes per hour to 50 minutes per hour. Since the
pumping times operated 24 hours a day, an incremental representative
process organic load was applied to the lagoon.
Since raw sewage (not comminuted) was used, clogging of the pump was
expected. In order to provide some cleaning, the three-inch discharge
lines were installed at a positive slope from the pump. This line dis-
charged into an outlet tank and weir assembly. At times when the pump
shut off, enough static head was present in this discharge line to back-
flush the line and clean out the pump.
The discharge line from the centrifugal pump was a three-inch diameter
plastic pipe. It was buried 30 inches below ground level. This line
discharged into a stilling basin and flowed over a V-notch weir into two
four-inch diamater plastic discharge lines (Figure 6). Flow rates were
determined by use of a float type gauge height recorder mounted above the
V-notch weir. Effluent from the lagoon discharged over a V-notch weir
mounted on the outlet structure. The effluent discharged back to the
city lagoon system through a six-inch vitrified clay effluent line. A
walkway was constructed to provide access to the effluent weir so that
samples could be collected and the discharge monitored.
The Aeration System
The mechanical aeration system used for the pilot lagoon was of the INKA
type as designed by Industrikemiska Aktiebologet of Stockholm, Sweden.
Major components of the system are a 10 horsepower radial air compressor,
an eight-inch diameter air header and support frames, and three stainless
steel INKA type air diffusors (Figure 7). The support frames were
fabricated of two-inch steel pipe and set in concrete about two feet
deep. Five sections of eight-inch diameter % inch steel pipe were welded
together to make a continuous air header. Three-inch diameter holes were
cut in the header and short pieces of three-inch pipe were welded to the
header to facilitate connection of the aeration units. A concrete plat-
form was poured and the air compressor was attached to it by anchor bolts,
A five-foot pipe transition section was used to connect the five-inch
discharge head of the compressor to the eight-inch diameter air header
16
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AIR HEADER
E3 Eva rill " •" fsa '
0 5 10
Scale 1" = 10'
Figure 7 Profile of the Aeration System
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line. The compressor was placed in a prefabricated steel shelter house
for protection from the weather. A differential pilot tube was inserted
into the header and connected to a U-tube monometer inside the compressor
house for monitoring of air quantities.
The diffused aeration grids are approximately three by eight feet with
3/16 inch orifices located on the bottom of the grill. Three of these
units were used in the pilot lagoon. The grids were placed at a depth
of 2.67 feet below the water. Since the aerator units were under the
water, they were not affected by icing (Figure 8).
The Baffle System
A baffle system consisting of corregated plastic sheets was attached to
the two-inch structural pipes. In order to give the sheets longitudinal
flexural strength they were supported by chainlink fence. The purpose of
the baffling along the sides of the aerator created a flow pattern that
insured mixing and immediate aeration of the incoming sewage. The aeration
grids and baffling form a type of air pump (Figure 9). The longitudinal
baffling promotes a clockwise circulation pattern in the lagoon. The
aeration units perform two operations - mixing of the sewage and aeration
of the sewage.
18
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AIR HEADER-
DISCHARGE LINE
EFFLUENT
WEI!
TRANSVERSE
BAFFLES
0 5 10
Scale 1" = 10'
Figure 8 Longitudinal Cross-Section of the Lagoon
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ro
o
MIXING
Figure 9 Hydraulic Flow
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SECTION V
OPERATIONAL FEATURES OF THE PILOT LAGOON
With the installation of the diffused aeration device and considering the
baffling and shape of the lagoon, it was hoped that the pilot lagoon would
approach a complete mixed system. In order to evaluate the mixing char-
acteristics of the lagoon and the rate constants of the raw sewage, several
tests were conducted.
Tracer Study
In order to test the hydraulic characteristics of the lagoon, a dye test
was used and a flow-through curve was plotted. To obtain a flow-through
curve, a slug of tracer is injected in the influent and the concentration
of tracer is monitored in the effluent at timed intervals. From this data
a flow-through curve (concentration of dye in the effluent vs. time after
injection) is plotted.
The flow-through curve indicates the statistical distribution of the flow
times of individual water molecules as they pass through the system. In
reality, the curve only approximates this distribution as tracers do not
necessarily follow the path lines taken by the water or waste water mole-
cules. Even with this imperfection, a flow-through curve obtained with a
good tracer and measuring device will yield valuable information about the
hydraulic characteristics of the detention structure.
All ideal flow-through curves have two fundamental characteristics: 1) the
average concentration of the dye in the effluent as computed from the curve
is equal to the average concentration applied and 2) the centroid of the
curve with respect to time occurs at the theoretical detention time. The
theoretical detention time is equal to the volume of the tank divided by
the flow rate.
Observed curves generally never fully satisfy these characteristics. The
tracer recovery ratio, defined as the ratio of the observed average con-
centration to the average applied concentration is generally less than one.
Any sorption, fading of dye, or decay of radioactivity (radioisotope tracer)
will cause the ratio to be less than one.
Several features of the flow-through curve indicate the hydraulic char-
acteristics of the system. High peaks close to the injection time
indicate short-circuiting. Long tails on the curve at low concentrations,
seemingly asymptotic to the zero concentration line, indicate zones or
21
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spaces which are hydraulically stagnant with little fluid exchange. Sharp
peaks near the theoretical detention time indicate plug flow or flow with
little longitudinal mixing. Curves which are flat with little peaking
indicate good mixing characteristics. Good mixing, which brings food,
oxygen, nutrients and bacteria together, is essential to proper, efficient
treatment.
Rhodamine WT, a fluorescent dye, was selected for use in this study. This
dye is easy to detect, has a low sorptive tendency and good diffusion
properties. A detailed explanation of fluorescent dye and their relative
merits has been presented by Wilson (4). The detection device used was
a Turner Model III Fluorometer.
The dye was injected through the influent line of the lagoon. Sampling of
the effluent began immediately with samples taken at approximately one
minute intervals. The one minute interval was continued for about one
hour and was changed only after the curve was defined.
All samples were tested in the field with temperature corrections made
according to Wilson (4).
The flow-through curve for a hydraulic loading of 210,000 gallons per day
is shown in Figure 10. The theoretical detention time is 2.5 days with a
tested detention time of 1.94 days. The tracer recovery ratio is 0.90.
The first peak, occurring only minutes after dye injection, indicates some
short-circuiting directly to the effluent weir (samples were collected at
effluent weir). The effluent weir should be located at the opposite end
of the lagoon which would allow more mixing time before exit. The second
slight peak indicates a return of the general flow from the clockwise
pattern of the lagoon. The height of the peak also indicates that after
only one pass the influent dye is about completely mixed in the lagoon.
If the first peak is neglected the actual detention time will be closer
to the theoretical time. Also with the extrapolation of concentration
values to infinite time, a recovery ratio approaching one will occur.
Considering the computed values and the general shape of the flow-through
curve, the tank can be seen to approach a complete mixed unit.
DO and BOD Values in the Lagoon
From the tracer studies it appears that the lagoon functions hydraulically
as a complete mix tank. In order to investigate the mixing properties in
a chemical and biological sense, Dissolved Oxygen (DO) and Biochemical
Oxygen Demand (BOD) values were tested at several locations in the pilot
lagoon.
22
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100
Q.
Q.
o
4->
fO
o
o
CJ
80 -
60
O
40 ~
20 ~
0 .5
1.2" = 1 hr
1.75
I-
1.2" = 96 hr
Figure 10 Flow-Through Curve
Dye Test
23
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Initial testing showed no variation in DO and BOD values as a function of
depth at any of the sampling stations. Therefore, samples were secured
from a depth of about 18 inches below the surface in all further testing.
A two-man rubber raft was used as a platform to secure the samples. A
rope system was used to stabilize the position of the raft at each site.
All samples were tested according to approved methods outlined in "Standard
Methods" (5).
Dissolved Oxygen and Biochemical Oxygen Demand tests were carried out under
two different process loads (320 and 990 Ibs. of five-day BOD per acre/day).
Samples were taken in 300 ml BOD bottles and tested in the laboratory. No
difference between field and laboratory testing was noted and therefore the
more convenient laboratory procedures were used.
Figure 11 shows a plan view of the pilot lagoon with the numbered sampling
sites. Flow is generally clockwise as viewed in Figure 11. Figures 12
and 13 give the Dissolved Oxygen (DO) values in mg/liter and Biochemical
Oxygen Demand (BOD values (five-day 20°C) in mg/liter for the process loads
respectively of 320 and 990 Ibs. of five-day BOD per acre/day.
The test process loading of 320 Ibs. of five-day BOD per acre/day, as shown
in Figure 12, indicates several features. The average DO is 7.3 mg/liter
with little significant deviation from this value. A slight increase is
noted passing the influent line.
The test process loading of 990 Ibs. of five-day BOD per acre/day, as shown
in Figure 13, indicates features different from the 320 Ib. loading. The
average DO value is 2.0 mg/liter. There is little significant deviation
from this value except below the point where the sewage influent line is
placed. Here the DO value drops to 0.0 mg/liter. After the aerators the
value is again 2.3 mg/liter. The average BOD value is 47 mg/liter. Again
little variation is shown except at the point below the influent line.
The values change from 45 mg/liter above to 77 mg/liter below the influent
line to 67 mg/liter below the aerators.
Considering the values of DO and BOD under the two process loadings, it is
apparent that the pilot lagoon approaches a complete mixed unit chemically
and biologically.
An attempt was made to determine how the oxygen was utilized around the
clockwise pattern. The differences appear to be random and no pattern
except across the aerators could be established.
BOD Constants
In order to evaluate the sewage used in the test periods, the BOD constants
were computed. The BOD test as set forth in "Standard Methods" (5) was
24
-------
o
LO
8
20
75'-
10
11
12
13
14
INFLUENT
LINE/
19
18
INKA AERATORS
17
16
15
EFFLUENT WEIR
SAMPLING STATIONS IN PILOT LAGOON
Figure 11
BOTTOM
OF
DIKE
25
-------
7-1
44
DO (mg/1)
BOD (mg/1)
6-0
48
7-2
38
7-5
37
7-5
40
6-8
41
7-2
41
7-5
45
8-1
44
8-0
42
7-9
42
7-0
41
7-3
40
o
6-9
35
6-6
43
7-5
43
6-9
37
7-9
42
6-9
40
8-1
40
DO AND BOD LEVELS IN PILOT LAGOON AT
320 Lbs./Acre/Day Loading
Figure 12
26
-------
1-9
43
2-1
49
1-6
44
1-9
44
1-7
37
2-1
40
1-8
45
o
2.3
45
0-0
77
2.0
45
2-3
40
1-7
42
1-6
45
2-3
67
1.6
40
2-1
46
2-3
50
1-6
40
2-4
44
2-0
47
DO and BOD Levels in Pilot Lagoon at
990 Lbs./Acre/Day Loading
Figure 13
27
-------
used with the following modification. The raw sewage was diluted to a
10% concentration with normal dilution water. This solution was thoroughly
mixed to insure homogeneity. All dilutions for testing were taken from the
10% solution. The test was conducted for a 36-day period with four dilutions
used for each test day. The "method of moments" developed by Moore, Thomas
and Snow was used to determine the first stage constants (6).
Figure 14 shows the results of the 36-day BOD tests. It shows that the
first stage BOD is the controlling reaction until the eighth day. From
the eighth day nitrification plays the dominant role. The figure shows a
five-day BOD value of 190 mg/liter and an ultimate oxygen demand of 450
mg/liter.
Evaluation of the first stage constants using the "method of moments" gave
values of k]Q = 0.19 (ke - 0.44) days -1 and L (initial demand) equal to
207 mg/liter. Assuming the second stage demand follows the same sort of
curve as the first stage with BOD = 0 and t = 0 for t = 8 days on the
first stage curve, and using the "method of moments" as before yields
kio = 0.13 (ke = 0.3) day -I and L of 240 mg/liter for nitrification.
The total ultimate (36-day) oxygen demand (207 + 240 = 447 mg/liter) is
in close agreement with the laboratory testing.
Considering the first stage demand of 207 mg/liter, the rate constant of
kio = 0.19 (ke - 0.44) days -1 and a five-day BOD value of 190 mg/liter,
it appears the sewage is of average type.
28
-------
450 -
400 -
300 i
200 J
TOO ~
10
15
20
25
TIME (DAYS)
36 Day BOD Curve for Laramie Municipal Sewage
30
i
35
Figure 14
-------
SECTION VI
RESULTS - THE AERATED PILOT LAGOON
The pilot lagoon was operated during two winter periods. The operation of
the pilot lagoon during these two periods was considerably different. In
order to understand the results and reasons for the testing and operational
procedures each test period is considered separately. ' A final summary is
included in order to collate all the results but each set of data must be
considered in light of operational conditions.
Test Period One
Although the pilot lagoon was put into operation in October of 1968, the
sewage pump did not operate reliably enough to obtain meaningful data
until the latter part of January, 1969. Period one presented here was
from February 2 to April 21, 1969. By February 2 the lagoon was considered
to have attained biological steady state and the pump was giving satis-
factory performance. The lagoon was operated at high (800 Ibs. of five-
day BOD per acre/day = 3.625 Ibs./I,000 ft3/day), intermediate (320 Ibs.
per acre/day = 1.450 Ibs./1,000 ft3/day), and low loadings (160 Ibs. per
acre/day = 0.725 Ibs./I,000 ft3/day) during the study. Since the aerated
pilot lagoon was a complete mix tank, a loading intensity based on volume
and not surface area is probably more appropriate. However, a comparison
to normal lagoon loadings is necessary and important for engineering
evaluation. Samples were taken four days per week. The parameters
selected for testing were: influent BOD and temperature, hydraulic load-
ing, effluent BOD, temperature and dissolved oxygen (DO). All tests were
conducted in accordance with "Standard Methods," 12th Edition.
Average Influent BOD and Rate Constant
Several composite, influent samples were taken over a three-week period.
The maximum BOD value observed was 226 mg/1, and the minimum was 154 mg/1.
The average value for influent BOD was computed to be 190 mg/1, and this
value was'used in computations for period one. The composite samples were
obtained by a gravity feed device that fed 40 ml/hour of influent sewage,
twenty-four hours per day, into a container held at 4°C to retard bacterial
activity. Composite samples were required to obtain an average because of
the variability in composition of the sewage over a twenty-four hour period.
The temperature of the influent sewage varied from 10° to 12°C during the
period of study.
A value at the rate constant (k) was computed by the "method of moments"
on the basis of results from a three-day series of BOD tests run at 20°C.
31
-------
The value was Iqo = °-19 (ke = 0-44) days -1. This is in agreement with
the mean value reported by Fair and Geyer (7).
These loading rates on the lagoon were held constant by use of an automatic
timer on the pump to regulate the pumping time to a specific number of
minutes on each hour's flow. For a given pump discharge rate, lagoon
area and influent BOD, the surface intensity loading is established by:
Q(Y!) 8.34
i =
A
where i = loading intensity in Ib. BOD/acre/day
Q = influent flow in million gallons per day (mgd),
Y-|= five-day 20°C BOD of the influent sewage in mg/1, and
A = surface area of the lagoon in acres.
For a typical example, surface loading intensity is illustrated by:
YI= BODc of 200 mg/1,
Q = 0.108 mgd (150 gpm pumped for 30 minutes/hour for 24 hours),
A = 0.32 acres, and
i = 0.108 (200)8.34 = 565 Ibs.BOD/Acre/day
0.32
Since the aerated lagoon is a complete mix basin from a physical mixing
standpoint, the volume factor can be utilized to determine a volume
intensity loading from the formula:
QT(24)Y1 8.34
i =
V X 103
where i - loading intensity in Ib. BOD/1,000 ft3/day,
Q = influent flow in gallons per minute,
T = time of pump operation (minutes) per hour,
Y]= five-day 2QOC BOD of the influent sewage in mg/1, and
V = volume of lagoon in cubic feet
For a typical example, volume loading intensity is illustrated by:
YT = five-day 20°C BOD of 200 mg/1
Q = 160 gal./min.
V = 71,125 ft3
T = 16 min./hr. (pump period during day)
(160) (16) (24) (200) (8.34) =
i = 71 1?^ Y VnV i. HJU i Db. DUU
1 "''^ X 1JJ 1,000 ft3/day
32
-------
Air Quantities
The quantity of air introduced through the diffusors was essentially
constant throughout the period of study. Air velocity was measured with
a differential pilot tube and manometer, and from this air flow was
calculated. Six different measurements were made and the average flow
was determined to be 900 cfm.
Sludge Deposition
In the second week of May, 1969, the lagoon was drained in order to
examine sludge deposits. Estimation of sludge quantities were difficult.
The lagoon bottom was not allowed to dry to any extent, because of time
considerations for other studies being conducted. However, it was
estimated that the sludge blanket was three to four inches in depth. The
sludge was fairly uniformly distributed over the lagoon bottom, except
the northeast quadrant of the lagoon. This area is hydraulically behind
the aeration units, and the higher velocities here prevented the deposition
of significant amounts of sludge (see Figure 9).
Discussion of Results
Field data taken during the study are presented in graphical form in
Figures 15 through 17. The parameters are plotted in pairs for ease of
comparison.
Some interesting effects can be noted upon examination of Figures 15 through
17. Although no consistent relationship is apparent between temperature
and effluent BOD, Figure 15 shows that three BOD values in the vicinity of
100 mg/1 occurred at low temperatures ranging from 0° to 3°C. Since
influent BOD was taken as a constant for the period of study loading
intensity and detention time were both functions of hydraulic loading.
Examination of Figures 15 and 16 shows that there was no correlation be-
tween detention time and effluent BOD (or percentage BOD reduction), and
correspondingly no correlation between loading intensity and effluent BOD
reduction). With few exceptions, effluent BOD values, and corresponding
percentage BOD reduction values, were consistently in the range of 55 to 75
mg/1, and 70 to 55 percent respectively. Figures 15 and 16 indicate that
a five to six fold increase of detention time, from three up to 17 days,
does not produce an appreciable change in lagoon performance with regard
to BOD reduction in the effluent. Figures 15 and 16 indicate a corollary
to the above statement; that is, an 80 percent reduction in loading in-
tensity, from 800 Ibs. BOD/acre/day to 160 Ibs. BOD/acre/day does not
produce an appreciable change in lagoon performance with regard to BOD
reduction in the effluent. These facts suggest that the bacteria are
able to oxidize some constituents of the sewage within three days, but
33
-------
12
10
UJ
-P-
CJ
o
QJ
0)
C-L
0
no
100
90
en
g 80
ZJ
^ 70
Q
O
OQ
0 60
50
40
800
320
160
Loadings Ibs. BOD/Acre/Day
i r
5 10 15 20 25 1 5 10 15 20 25 30 1
February 1969 March
Effluent BOD and Temperature in the Pilot Lagoon
Figure 15
10 15
Apri 1
-------
O)
s_
O)
Q.
O)
12
10 1
800
320
160
Loading Lbs. BOD/Acre/Day
Ul
80 -i
J 70 1
TD
O)
O
CQ
60
50
40
February 1969
10
"T
25
T
T
March
T~
~r
20
~T
30
Apri 1
15 20 25 1 5 10 15 20 25 30 1
Effluent BOD Reduction and Temperature in the Pilot Lagoon
Figure 16
T"
10
15
-------
12-f*
o
o
cu 8~
£ £
0)
Q_
§ 4-j
2-1
0
12'
10-J
800
320
160
CD
E
cu
en
>> 6-
o
o
oo 0
to £•
Loading Lbs. BOD/Acre/Day
5 10 15 20 25 1
February 1969
10 15 20 25 30 1 5 10 15
March April
Effluent DO and Temperature in the Pilot Lagoon
Figure 17
-------
that remaining organic matter requires detention times in excess of 17
days for stabilization at temperatures observed during the study. Opera-
ting temperatures in the range of 20°C should produce considerably lower
effluent BOD values. Another possible explanation of the lack of correla-
tion between loading and efficiency is that possibly large amounts of
sludge were deposited at the high loading intensities at the beginning
of the study, producing a secondary load on the lagoon throughout the
remainder of the study.
Figure 17 shows that at no time during the study did the dissolved oxygen
content fall to zero. This implies that oxygen for bacteria was never a
limiting factor and that aerobic conditions were maintained in the system
throughout the period. Figure 17 also suggests that there is a correla-
tion between loading intensity and dissolved oxygen content. Figure 18
shows the correlation, as a plot of dissolved oxygen deficiency (saturation
DO value minus observed DO value) versus loading intensity. Assuming a
requirement of 6 mg/1 DO in the effluent, and assuming a critical tempera-
ture of 20°C (saturation = 7.1 mg/1 at Laramie), the curve indicates that
a loading of about 100 Ibs. BOD/acre/day would meet the DO requirements.
Tests on effluent samples showed that settleable solids were consistently
less than 1/2 ml/1. The pH values are not included here because they were
essentially constant and had no apparent variation. The pH values of the
influent sewage varied from 8.0 to 7.4 and values of the effluent ranged
from 8.2 to 7.1.
The samples and temperature measurements taken at the effluent weir are
felt to be representative of conditions in the lagoon because of the mixing
provided by the aerators. The lagoon was probably operating in a bacterial
log growth phase. Two facts lead to this conjecture. First, mixing by
the aerators provides a system in which bacteria and substrate are dis-
persed, and secondly the absence of significant settleable solids in
effluent samples indicates that no floes were formed by bioflocculation.
The reason for the absence of bioflocculation could be due to either
shearing effects caused by the violent mixing at the aerators or the
absence of endogenous growth.
The foaming of detergents present in the sewage was observed on several
occasions. Agitation of the incoming sewage by the aerators caused foam,
which at times was two feet above the water surface behind the aerators.
The foaming does not appear to be a serious operational problem. The flow
pattern in the lagoon, illustrated in Figure 19, was borne out by observ-
ing the pattern formed by foam on the lagoon surface. The aerators showed
no appreciable physical deterioration at the conclusion of the study.
Some trash accumulated on them, but the trash build-up was not large enough
to affect operation.
Some icing occurred during the period March 10 to March 15. This was the
only time that ice was formed and even during this period the ice covered
37
-------
7 H
6 H
00
o;
CD
o
4 J
3 H
x
o
O
I/O
GO
2 H
i H
TOO 200 300 400 500 600 700 800 900
Loading Intensity (Pounds BOD/Acre/Day)
1000
Figure 18 Dissolved Oxygen Deficiency vs. Loading Intensity
38
-------
»
t
\
\
o
/ \
I \
\
Figure 19 Flow Pattern
39
-------
only about 75 percent of the lagoon surface and was less than an inch
thick. The area behind the aerators remained open during this period.
The mean air temperature during this period was 3°F- The average daily
low temperature for the period was -15°F-
Test Period Two
Several questions concerning operation and data occurred during the first
test period. Since the initial process load for period one was 800 Ibs./
acre/day (the highest loading), it was possible a sludge deposit was
formed. This deposit could have been metabolized during the two lower
loadings and masked the effect of load and detention time variation.
Therefore, the pond was operated starting at the lower loadings (160 Ibs./
acre/day) for Test Period Two.
A second question regards the bacterial concentration. If the rate of
loading varies and no appreciable sludge build-up occurs and the final
BOD is comparable, then organic material must be metabolized at a faster
rate. Since temperatures were not significantly changed, the bacterial
population or kind must change. Bacterial counts therefore were secured
during Test Period Two.
A third question was the possibility of improvement of effluent quality
by the use of aerated cells operated in series. Since only one pilot
lagoon was constructed, a second cell was simulated by shutting off the
influent and monitoring the change in several parameters with time. The
aeration system remained constant (900 cfm) during this period. This
type of test obviously is not a true picture of series operation. The
second cell actually operates as a batch or slug type flow cell. However,
the results from the testing indicates some significant operational
problems associated with series operation.
All physical, chemical and biological testing was performed at the Environ-
mental Engineering Laboratory, Civil Engineering Department, University of
Wyoming. Testing and sampling procedures were in accord with the Thirteenth
Edition of "Standard Methods" for the Examination of Water and Waste-Water.
Tests to determine total bacteria and coliform bacteria were performed in
the laboratory of the Veterinary Medicine and Microbiology Department of
the University of Wyoming.
In addition to testing procedures from "Standard Methods," analytical
determinations for nitrate nitrogen, nitrite nitrogen, orthophosphate and
sulfate were made using the Hach DR-EL "Direct Reading" Portable Laboratory
as manufactured by the Hach Chemical Company.
Samples were routinely collected and tested from the influent and effluent
of the pilot lagoon. Samples were collected four times a week. Additional
40
-------
testing was performed when the loading was changed in order to determine
steady state conditions.
Operation Test Period Two
The test series in the first cell was conducted with loadings of 160 Ibs./
acre/day (.725 Ibs. BOD/1,000 ft3/day), 320 Ibs. BOD/acre/day (1.450 Ibs.
BOD/1,000 ft3/day), 700 Ibs. BOD/acre/day (3.15 Ibs. BOD/1,000 ft3/day),
and 900 Ibs. BOD/acre/day (4.08 Ibs. BOD/1,000 ft3/day), a maximum loading
rate. The 160 Ibs./acre/day and 320 Ibs./acre/day test functioned as
planned; however, the maximum loading varied considerably from a low 700
Ibs./acre/day to a maximum of 900 Ibs./acre/day due to the large fluctua-
tion of the influent BOD. At the time that the final test series was
started, infiltration from the flooded Laramie River was at a peak and the
influent BOD dropped from an average value of 200 mg/1 to an average value
of 160 mg/1. Using the loading intensity equation, the hydraulic loading
was adjusted in an attempt to hold the planned maximum load of 900 Ibs./acre/
day. This attempt was not successful since the increased head of water
above the aeration grid reduced the flow of air supplied to the lagoon
which in turn reduced the dissolved oxygen level. A maximum rate of
700 Ibs./acre/day was then established and continued for seven days until
the loading could be increased.
Detention time in the first cell based on the loading rates is as listed
in Table 1 below.
TABLE 1
LOADING INTENSITY AND DETENTION TIME
(FIRST CELL)
Loading Calculated Detention Time
Lbs. BOD/acre/day Days
160 17.0
320 8.5
700 3.9
900 3.0
41
-------
After changing the intensity loading,
of at least twice the detention time.
state conditions. It is difficult to
conditions. It was assumed that when
(including biological
was attained.
the test series was of a duration
This allowed establishment of steady
determine the ecological steady
the values for several variables
variables) remained constant a steady state condition
The efficiency of lagoon treatment at the test loading conditions is based
on percentage BOD reduction as computed from the equation:
,00
where E = efficiency or % BOD reduction,
YI= five-day 20°C BOD of influent sewage, and
Y2= five-day 20°C BOD of effluent
Physical and chemical changes at various test loadings are compared using
a similar percentage calculation as the BOD reduction equation above. The
general percent reduction equation is:
R -
100
where R
S] and $2
percent reduction, and
concentrations in influent and effluent, respectively.
160 Lbs. BOD/Acre/Day Loading
A loading intensity of 160 Ibs. BOD/acre/day (.725 Ibs. BOD/1,000
day) was initiated in February 1970. The theoretical detention period
for this loading is 17 days. Aeration was a constant of 900 cfm for the
period. After the onset of steady state conditions, the system was
operated for a period of about four weeks.
Toward the end of March the influent loading to the aerated lagoon was
stopped. This was done in order to assess the performance of a second
cell in series. Since the second cell received no constant influent, a
series operation was only simulated. This batch process however did
indicate several operational features. Aeration was continued at 900 cfm
during second cell operation.
A summary of data acquired during cell one and cell two testing is shown
in Tables 2 and 3. Four values are shown for each parameter. Each of
these values represents an average of several samples. Those of cell two
(the batch process) also indicate testing on a three or four day subsequent
time period.
42
-------
TABLE 2
STEADY STATE TEST RESULTS
AERATED LAGOON LOADING
160 Lbs./Acre/Day
TESTS
Temperature (°C)
TS (mg/1)
TVS (mg/1)
TSS (mg/1)
VSS (mg/1)
Settleable Solids
(ml/1)
Alkalinity (mg/1)
as CaCO-
3
Hardness (mg/1 )
as CaC00
3
PH
FIRST
Influent
12
12
12
12
1198
1534
1264
1164
407
465
425
356
304
422
_ _
- -
223
262
- -
9
9
9
9
340
337
340
337
610
516
500
7.6
7.5
7.3
7.5
CELL
Effluent
2
3
0
1
1065
1039
1068
1071
268
197
251
267
46
57
_ _
- -
42
32
- -
0
0
0
0
306
317
318
314
690
572
568
7.8
7.8
7.6
7.6
SECOND CELL
Effluent
0
0
3
5
1027
1081
1053
1041
226
206
202
208
43
36
48
61
28
38
47
0
0
0
0
314
334
316
311
564
572
568
8.0
8.1
8.4
8.2
43
-------
TABLE 3
STEADY STATE TEST RESULTS
AERATED LAGOON LOADING
160 Lbs./Acre/Day
TESTS
SO"2 (mg/1)
H
NO "] (mg/1 )
j
PO/3 (mg/1 )
H
DO (mg/1 )
COD (mg/1 )
Biochemical Oxygen
Demand (BOD)
(mg/1 )
Col i form Bacteria
(Number/ml )
Total Bacteria/ml
Henri ci 's Agar*
TSA**
FIRST
Influent
460
300
500
400
8.0
8.0
6.0
10.0
22
30
35
15
0
0
0
0
506
560
500
399
217
214
202
183
3 A III
3 A 1 U
- -
— —
CELL
Effluent
450
400
500
400
8.0
8.0
5.0
10.0
12
12
25
18
7
7
7
7
119
70
85
133
32
38
44
20
*2
7.5 X 10
7
1.2 X 10'
1.9 X 106
SECOND CELL
Effluent
500
400
400
- -
6.0
0.0
0.0
8.0
15
22
25
- -
9
11
11
12
128
44
54
111
23
33
38
39
10
c.
7.2 X 10b
1.8 X 106
*Henrici's Agar incubated at 30°C (dilute medium with a wide variety
of carbon and energy sources).
**TSA incubated at 30°C (rich nutrient medium), Trypticase Soy Agar-
BBL Division of Bioguest, Cockeysville, Maryland.
44
-------
Several features are apparent from the data of Tables 2 and 3. The
temperature of the influent, which was true for all test periods, averaged
12°C. The temperature of the effluent was modified by detention time and
ambient air temperature.
Even at temperatures close to 0°C, significant BOD, COD, and volatile
solids reduction is experienced for the 160 Ibs. BOD/acre/day loading.
BOD reduction averaged about 85% reduction in cell one and no change in
cell two. Apparently further biological reduction in BOD would require
larger periods of time or warmer temperatures.
At a loading of 160 Ibs. BOD/acre/day no settleable solids were produced
in the effluent from cell one or cell two. The biological process would
not be improved by the introduction of a sedimentation tank in series
operation.
The dissolved oxygen level varied from 6.7 to 7.5 with an average of 7 mg/1
during the loading of cell one. When the influent loading was stopped,
the dissolved oxygen increased and approached saturation levels.
Both coliform and total bacteria counts were secured for cell one and
cell two. The total count as determined on Henrici's Agar should be
considered the base count with the TSA count used as a check of magnitude.
The second cell bacteria values reported in Table 3 were from a sample
taken two weeks after the beginning of cell two operation. The total
count apparently does not change significantly from cell one to cell two
during this period. The coliforms, however, were reduced to a value of
about 10/ml after two weeks in cell two. This value apparently was a
minimum since additional detention time (greater than two weeks) did
not reduce it.
Changes in hardness and sulfate are due to the ionization of CaS04 (gypsum)
dissolved from the berm by wind and wave action. Toward the end of the
test period for cell two significant algae were produced in the aerated
pond. This became a significant parameter in the next test series.
320 Lbs. BOD/Acre/Day Loading
A loading intensity of 320 Ibs. BOD/acre/day (1.450 Ibs. BOD/1,000 ft3/day)
was initiated following the test on cell two (160 Ibs. BOD/acre/day) in
early April. The theoretical detention period for this loading is 8.5 days.
Aeration was a constant of 900 cfm for the period. After the onset of
steady state conditions, the system was operated for about two weeks.
Toward the end of April the influent loading was stopped. A batch process
resulted. This indicated possible operational features of a cell in series
but since it received no influent from cell one it is only a simulation.
45
-------
A summary of the data acquired during cell one and cell two operation is
shown in Tables 4 and 5. Four values are reported for each parameter.
Each of these values represents an average of several samples. The data
of cell two (the batch process) also indicates testing on a three or four
day subsequent time period.
Several features are apparent from the data of Tables 4 and 5. The
temperature of the influent averaged about 12°C. The temperature of the
effluent from cell one or two is modified by the ambient air temperature.
The shorter the detention time the closer the effluent temperature will
be to the influent temperature.
During this test period an increase in algae concentration was noted. The
increase was significant during cell two operation. The BOD data indicates
a reduction to about 37 mg/1 (filtered) but about 60 with the algae.
During cell two operation a further increase in BOD to around 75-80 is
noted. The filtered also increased to 51 perhaps due to non-filterable
algae waste.
At the loading intensity of 320 Ibs. BOD/acre/day no settleable solids
were produced in the effluent from cell one or cell two. Sedimentation
would not improve efficiency.
The dissolved oxygen level remained at about 7 mg/1 during this loading.
When the influent flow was stopped again the dissolved oxygen approached
the saturation levels. Dissolved oxygen samples were taken at 12 noon.
Under cell one operation the dissolved oxygen level varied from about
2 mg/1 at daylight to about 10 mg/1 in middle afternoon. A noon sample
was selected as representative of the average value.
Both coliform and total bacteria count were secured for cell one and cell
two. The total count was determined on Henrici's Agar should be con-
sidered the base count with the TSA method used to check reliability.
The second cell bacteria values in Table 5 were from a sample taken two
weeks after the beginning of cell two operation. The total count appears
to be in the same magnitude range in cell one and cell two. The coliform
count is reduced to 5/ml in test two. Under the environmental conditions
of cell two, coliforms are unable to compete and die-off is rapid.
900 Lbs. BOD/Acre/Day Loading
A loading intensity of 900 Ibs. BOD/acre/day (4.08 Ibs. BOD/1,000 ft3/day)
was initiated in late May. Due to infiltration from snow melt a loading
of 700 Ibs. BOD/acre/day was the maximum attainable until June 5. At
that time a uniform loading intensity of 900 Ibs. BOD/acre/day was
achieved and maintained. The system was operated at this level for
about four weeks. The detention time was 3.0 days.
46
-------
TABLE 4
STEADY STATE TEST RESULTS
AERATED LAGOON LOADING
320 Lbs./Acre/Day
TESTS
Temperature (°C)
TS (mg/1)
TVS (mg/1)
TSS (mg/1)
VSS (mg/1)
Settleable Solids
(ml/1)
Alkalinity (mg/1)
as CaCO.,
3
Hardness (mg/1)
pH
FIRST
Influent
12
12
12
12
1430
1504
1859
1486
409
355
- -
364
606
- -
1327
575
324
- -
_ _
305
9
10
8
7
304
360
282
346
632
612
624
628
7.5
7.9
7.5
7.5
CELL
Effluent
5
6
7
6
1264
1337
1325
1279
298
350
- -
312
87
- -
136
100
87
- -
- -
98
0
0
0
0
296
279
287
300
772
752
780
784
8.0
8.0
8.2
8.2
SECOND CELL
Effluent
7
10
11
9
_ _
1195
1372
1440
_ _
317
288
251
_ _
288
188
208
- -
152
144
142
0
0
0
0
- -
268
280
- -
732
780
- -
8.6
8.7
8.8
8.4
47
-------
Coliform Bacteria
Total Bacteria
Henrici's Agar*
TSA**
TABLE 5
STEADY STATE TEST RESULTS
AERATED LAGOON LOADING
320 Lbs./Acre/Day
rrryc FIRST
TESTS Influent
SOA"2 (mg/1 ) 800
^ 600
500
600
NO ~] (mg/1) 0.0
J 8.0
6.0
0.0
PO/3 (mg/1 ) 3
4 8
18
18
DO (mg/1 ) 0
0
0
0
COD (mg/1) 313
339
338
- -
Biochemical Oxygen 223
203
224
165
CELL SECOND CELL
Effluent Effluent
1200
800
700
800
5.0
8.0
2.0
0.0
10
12
28
12
6.6
6.6
7.0
7.0
156
131
202
- -
56 (filtered)
CO
/ q-y \
r *\ \ O / )
DO
50
1250
1000
750
750
3.0
0.0
0.0
0.3
25
23
9
7
8.6
8.0
7.6
8.2
_ _
200
185
173
72(filtered)
76 ,,,*
91 (bl)
75
5 X
9 X 10'
2.2 X 10'
1.1 X 10'
4 X 10'
1.1 X 10;
*Henrici's Agar incubated at 30°C (dilute medium with a wide variety
of carbon and energy sources).
**TSA incubated at 30°C (rich nutrient medium), Trypticase Soy Agar-BBL
Division of Bioguest, Cockeysville, Maryland.
48
-------
At the end of this period the influent loading to the aerated lagoon was
stopped. This provided a means for assessing the performance of a second
cell in series.
Since the second cell received no loading the second cell operated under
batch type conditions and only simulated series operation. This batch
process did indicate several operational conditions. Aeration was con-
tinued at 900 cfm during both cell operations.
A summary of data acquired during cell one and cell two testing is shown
in Tables 6 and 7. Four values are shown for each parameter. Each of
these values represents an average of several samples. The data of cell
two (batch process) also indicates testing on a three or four day sub-
sequent time period.
Several features are apparent from the data of Tables 6 and 7. The
temperature of the influent remains, as in the other test periods, at
12°C. The effluent temperatures however are now equal to or greater than
the effluent because of high ambient temperatures.
Significant BOD and COD reduction was experienced for the 900 Ibs. BOD/
acre/day loading. BOD reduction averaged about 80% to 88% in cell one.
At this loading intensity the algae produced in cell two from the 320 Ibs.
BOD/acre/day load were rapidly reduced and they did not significantly
reappear until the 900 Ibs. BOD/acre/day loading was stopped and cell
two operation was begun.
At a loading of 900 Ibs. BOD/acre/day no settleable solids were produced
in the effluent from cell one or cell two. The biological process would
not be improved by sedimentation tank in series operation.
The dissolved oxygen level varied from about .5 mg/1 at daybreak to about
4.4 mg/1 during the rest of the day under cell one operation. Under cell
two operation the dissolved oxygen varied from zero at daybreak to about
6.8 mg/1 in late afternoon. A noon sample gave an average value for
this variation. The influence of heavy loading and algae is apparent.
Both coliforms and total bacteria count were secured for cell one and
cell two. The total count as determined on Henrici's Agar should be
considered the base count with TSA count used for magnitude check. The
second cell bacteria reported in Table 7 were from a sample taken two
weeks after the beginning of cell two operation. The total count indicates
the total bacteria population remains constant for cell one and cell two
operations. However, coliforms are not competitive in this environment
and are reduced to about 15/ml after two weeks.
Increase in VSS, BOD, COD and average pH in cell two indicate algae
production. Increase in TS, hardness and S04 indicates solution of
gypsum from berm of lagoon.
49
-------
TABLE 6
STEADY STATE TEST RESULTS
AERATED LAGOON LOADING
.900 Lbs./Acre/Day
TESTS
Temperature (°C)
TS (mg/1 )
TVS (mg/1)
TSS (mg/1 )
VSS (mg/1)
Settleable Solids
(ml/1)
Alkalinity (mg/1)
as CaCO-
•J
Hardness (mg/1 )
as CaCO,
•J
pH
FIRST
Influent
12
12
12
12
1991
1918
1833
1910
331
365
386
361
255
200
269
241
158
108
159
142
9
8
7
9
248
254
268
280
1240
900
1040
1068
7.7
7.4
7.3
7.5
CELL
Effluent
11
11
12
14
1022
1366
1469
1540
325
267
300
286
65
59
71
74
60
50
71
68
0
0
0
0
240
220
240
244
820
800
880
980
7.7
7.7
7.6
7.7
SECOND CELL
Effluent
19
18
20
--
1751
1812
2134
- -
335
411
676
- -
104
127
296
340
130
132
172
120
0
0
0
-
228
220
246
224
1140
1160
1160
1150
7.7
8.6
8.3
8.6
50
-------
TABLE 7
STEADY STATE TEST RESULTS
AERATED LAGOON LOADING
900 Lbs./Acre/Day
TESTS
S°4~ (mg/1 )
NO'1 (mg/1 )
PO."3 (mg/1 )
T1
DO (mg/1 )
COD (mg/1 )
Biochemical Oxygen
Demand (BOD)
(mg/1 )
FIRST
Influent
1500
850
1250
1000
0.0
0.5
0.0
0.0
5
10
7.5
10
0.5
0.0
0.0
0.0
164
300
279
368
225
175
199
200
CELL
Effluent
1000
750
1250
1000
0.5
0.0
0.0
0.0
15
7.5
5.0
6.0
1.5
4.4
3.5
3.0
40
80
65
98
51
54
30
25
SECOND CELL
Effluent
1000
1500
1500
1500
0.0
0.0
1.0
0.0
10.0
10.0
10.0
- -
5.5
5.5
5.5
- -
163
259
269
- -
40 (filtered)
45 (40)
90
125
Coliform Bacteria
(Number/ml)
Total Bacteria
(Number/ml)
Henrici's Agar*
TSA**
5 X
1.7 X
15
5 X 10'
8.6 X 10e
2.8 X 10'
2.1 X 10'
*Henrici's Agar incubated at 30°C (dilute medium with a wide variety
of carbon and energy sources).
**TSA incubated at 30°C (rich nutrient medium), Trypticase Soy Agar-BBL
Division of Bioguest, Cockeysville, Maryland.
51
-------
A summary of curves indicating values of several parameters identified
under the various loadings and conditions is illustrated in Figure 20
through 24.
52
-------
160
320
100
100 -
75 -
50 -
25
Loading Intensity Lbs. BOD/Acre/Day
—i r
10 20
Apri 1
—i 1—
10 20
May
T T
T 1 1 T
1 10 20 1
February
10 20
March
1
1
1
10 20
June
Effluent BOD (five-day 20°C) vs. Loading Intensity
Figure 20
-------
160
320
900
Loading Intensity Lbs. BOD/Acre/Day
c
o
o
Z3
-o
Ol
oc.
o
o
CD
90 .
80 -
70 -
60 -
10 20 1
February
10 20
March
10 20
April
1970
10 20
May
Figure 21 Percent Reduction of BOD
10 20
June
-------
Ln
O
o
tu
S-
S-
0)
ex
O)
o
o
CD
(X3
28
26
24
22
20
18
16
14
12
10
8
6
4 ~\
2
0
160
Loading Intensity Lbs. BOD/Acre/Day
0 320 0 900
Air
Lagoon
1 10 20
February
1 10 20 1 10 20 1 10 20 1 10 20
March April May June
1970
Air and Lagoon Temperatures (OG) vs. Loading Intensity
Figure 22
1
July
-------
Ln
ON
109 ^
108
10? -,
106
105 -
104
3 -
10
io2 J
ioi -I
0
160
D
D
Loading Intensity Lbs. BOD/Acre/Day
_ 0 .1. 320 .i.O i. 900
DDD
£± Total Count - Hentici's Agar
D Total Count - TSA
O Col iforms
0 10 20 1 10 20
February March
1 10 20 1 10 20 1 10 20 1 10
April May June July
Total Bacteria and Coliform Counts vs. Loading Intensity
Figure 23
JL_
i
20
-------
Loading Intensity Lbs. BOD/Acre/Day
15
g 10
(D
an
-------
SECTION VII
SUMMARY AND CONCLUSIONS
First Cell Summary
The data summarized in this section refers to loadings of 160, 320 and
900 pounds per acre/day used in the 1970 tests. Table 8 shows the percent
reduction in BOD between the influent of raw sewage and the effluent from
cell one. The influent five-day 20°C BOD was determined from a composite
sample. At the 160 Ibs./acre/day loading the effluent had a BOD of 34
mg/1 for an efficiency of 85% with no algae present. The average tempera-
ture was approximately 2°C. At the 320 Ibs. per acre/day loading the
temperature increased to about 6°C and an algae bloom developed. Tests
with algae shows an average BOD of 57. Tests after filtering the algae
gave a value of 37. At the 900 Ibs./acre/day loading, algae were still
present in the effluent but at a greatly reduced concentration. Effluent
BOD was 39 mg/1 in the filtered sample for an efficiency of 80 percent.
The average temperature in this test was 12°C. These values are slightly
better than data from 1969 testing. Since testing in 1969 was done in
reverse order of loading from high to low, better efficiency at lower
loadings in 1970 seems to indicate that some sludge setting in 1969 and
delayed metabolism masked lower loading values.
Table 9 shows the change in coliform count and total bacteria count at
the three loading conditions of the first cell. Of significance in this
table is the smaller increase (2.3 times) of coliform bacteria as com-
pared to a larger increase (4.2 times) in total bacteria as loading
increased from the low loadings of 160 Ibs./acre/day to the high loading
of 900 Ibs./acre/day (5.6 times). Apparently as loading increases the
coliform group is less able to compete and are reduced. Since Table 8
shows no significant difference in BOD reduction under different loadings,
a difference in bacterial population or kind must exist. Table 9 shows
an increase proportional to loading. Differences from exact proportion
can be rationalized from increased temperature at higher loadings.
Table 10 shows the removal of the physical variables the first cell
loadings. It is noted that values from influent samples at various
loadings are not consistent even though the values reported were averaged
over the period. Over the test period several influent parameter changed
in magnitude. This can possibly be explained by: (1) Laramie is a
college town resulting in fluctuations in sewage flow depending on student
presence, (2) variations in air temperatures resulting in changes in
infiltration rates.
59
-------
TABLE 8
SUMMARY OF AVERAGE BIOCHEMICAL OXYGEN DEMAND
AERATED PILOT LAGOON
FIRST CELL
Loading
Conditions
Influent Effluent reduction temperature
mg/1 mg/1 (percent)
160 Ibs./acre/day
(no algae)
320 Ibs./acre/day
(algae)
320 Ibs./acre/day
(algae filtered out)
900 Ibs./acre/day
(algae)
900 Ibs./acre/day
(algae filtered out)
204
203
203
200
200
34
57
37
40
39
85
2QC
72 6°C
82 6°C
80
12°C
80
60
-------
The reduction of TSS and VSS from influent to effluent samples was either
from solids settling in the lagoon or as a result of biological activity.
The solids settled were not significant based on deposits remaining in
the lagoon after the test program (lagoon drained).
Table 11 indicates the average value of chemical tests performed under
the three loading conditions. The table again shows a variation of
influent during the three loading periods. Hardness increased due to
the change in infiltration rate or ionization of wind-blown gypsum from
the berm. The hardness and sulfate concentration at the 900 Ibs./acre/
day load is indicative of gypsum.
TABLE 9
TOTAL BACTERIA AND COLIFORM COUNTS
(FIRST CELL)
Loading
Coliform Number/ml
Total Number/ml
Temperature
Average
160 Ibs./acre/day 7.5 x 103 (average) 1.2 x 10
(Henrici's)
1.9 x 106
(TSA)
320 Ibs./acre/day 9.0 x 103 (average) 2.2 x 10?
(Henrici's)
107
900 Ibs./acre/day 1.7 x 104 (average)
1.0 x
(TSA)
5.0 x 107
(Henrici's)
8.6 x 106
(TSA)
2°C
6°C
12°C
61
-------
TABLE 10
SUMMARY OF AVERAGE PHYSICAL TEST RESULTS
AERATED PILOT LAGOON
FIRST CELL
Aerated Lagoon
TS (mg/1) Influent
Effluent
TVS (mg/1) Influent
Effluent
TSS (mg/1) Influent
Effluent
VSS (mg/1) Influent
Effluent
Loading 160 IDS.
1290.0 %
1061.0
413.0 %
271.0
363.0 %
51.0
242.0 %
37.0
/acre/day
Removal
Removal
Removal
Removal
18
35
86
85
Aerated Lagoon
TS (mg/1) Influent
Effluent
TVS (mg/1) Influent
Effluent
TSS (mg/1) Influent
Effluent
VSS (mg/1) Influent
Effluent
Loading 320 Lbs.
1570.0 %
1301.0
376.0 %
320.0
836.0 %
107.0
223.0 %
92.0
/acre/day
Removal
Removal
Removal
Removal
17
15
87
71
Aeraged Lagoon
TS (mg/1) Influent
Effluent
TVS (mg/1) Influent
Effluent
TSS (mg/1) Influent
Effluent
VSS (mg/1) Influent
Effluent
Loading 900 Lbs
1917.0 %
1350.0
361.0 %
295.0
241.0 %
67.0
142.0 %
62.0
./acre /day
Removal
Removal
Removal
Removal
29
18
72
56
62
-------
TABLE 11
SUMMARY OF AVERAGE CHEMICAL TEST RESULTS
AERATED PILOT LAGOON
FIRST CELL
Aerated Lagoon 1
Loading
Alkalinity (mg/1)
Hardness (mg/1)
PH
S04-2 (mg/l)
N03~l (mg/1)
P04~3 (mg/1)
DO (mg/1)
COD (mg/1)
60 Ibs. /acre/day 320 Ibs. /acre/day
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
338
314
542
610
7.5
7.7
415
437
8.0
8.0
25
17
0
7
491
102
323
290
624
772
7.6
8.1
625
875
3.5
3.7
12
15
0
3.5
263
163
900 Ibs. /acre/day
260
236
1062
870
7.5
7.7
1150
1000
0.0
0.0
8.0
8.4
0.0
3.1
277
71
63
-------
The pH increased to 0.5 units at the 320 Ibs./acre/day load. This was due
to algal absorption of C02- Algal absorption of phosphate also occurred
in this loading. In order to evaluate this absorption, samples were
filtered and tested. Filtered samples contained no phosphate ions indica-
ting absorption in the algal mass.
Although the BOD test is an indication of biologically oxidizable organic
matter, a chemical oxidation test (COD) can also give valuable information
as to the effectiveness of treatment technique. Under the 160 Ibs./acre/
day process loading the BOD removal was 85% in comparison to a COD reduc-
tion of 80%. Under the 320 Ibs./acre/day process load the BOD removal
was 72% (with algae) and only 38% removal of COD. This clearly indicates
the inadequate nature of the BOD test as a lone criteria of treatment
efficiency. Under the 900 Ibs./acre/day process load, very little algae
were present and COD reduction of 75% again is significant.
First Cell Conclusions
Operation of the aerated first cell proved very successful both from the
stabilization efficiency of BOD removal and percentage reduction of the
physical and chemical parameters in the effluent. BOD removal in the
range of 75 to 85 percent for these loading rates at temperatures below
12°C was encouraging. At low loading intensities, common in normal
lagoon practice, a large surface area is required and an effluent at
best of 85 to 90% BOD reduction is produced. Although the algae do not
significantly affect the BOD test their effect is dramatic on the COD
test. Using the high loading of greater than 900 Ibs./acre/day corrects
both problems of large surface area and heavy algae production and release.
Second Cel1 Summary
The data summarized in this section refers to second cell operation after
successive process loadings of 160, 320 and 900 Ibs./acre/day used in the
1970 tests. These results indicate batch-type operation and not true
series operation. However, they do indicate several variations of boundary
conditions important for engineering consideration.
Table 12 shows the percent reduction in BOD between the steady state batch
condition and the effluent from cell two. It is apparent that as far as
BOD is concerned, little or negative results occurred. Again, algae
production under the 320 and 900 Ibs./acre/day loading increased the
effluent BOD.
Table 13 shows the change in coliform and total bacterial count after
nine two-week periods in cell two. The average coliform count of cell
one (7.5 x 103 to 1.7 x 104) of about 10,000 per ml is reduced to about
64
-------
TABLE 12
SUMMARY OF AVERAGE BIOCHEMICAL OXYGEN DEMAND
AERATED PILOT LAGOON
SECOND CELL
Aerated Lagoon - No Influent - First Cell Loading Was
160 Lbs./acre/day
BOD
Influent 34 % BOD Reduction
Effluent 33
Aerated Lagoon - No Influent - First Cell Loading Was
320 Lbs./acre/day
BOD
Influent 57 with algae % BOD Reduction
37 with algae removed
Effluent 78 with algae -37 with algae
51 with algae removed -28 with algae removed
Aerated Lagoon - No Influent - First Cell Loading Was
900 Lbs./acre/day
BOD
Influent 40 with algae % BOD Reduction
39 with algae removed
Effluent 80 with algae -100 with algae
39 with algae removed 0 with algae removed
65
-------
TABLE 13
TOTAL BACTERIA AND COLIFORM COUNT
IN SECOND CELL TESTS
Loading
Condition*
Coliform Bacteria
Count
Total Bacteria
Count
160 Ibs./acre/day
320 Ibs./acre/day
900 Ibs./acre/day
Die-off to 10/ml in
two weeks
Die-off to 5/ml in
two weeks
Die-off o 15/ml in
two weeks
*Loading Condition preceded second cell.
7.2 x 106/ml
(Henrici *s)
1.8 x 106/ml
(TSA)
4.0 x 107/ml
(Henrici's)
1.1 x 107/ml
(TSA)
2.8 x 107/ml
(Henrici:s)
2.1 x 107/ml
(TSA)
66
-------
10 per ml in cell two. In this environment the coliform organisms
obviously fail to compete. A comparison of total bacterial counts from
all three loads shows that they tend to level off at around 2 x 10' ml
after two weeks.
Table 14 shows average values and percent removal of physical variables
in the second cell for the three loadings. Test results under the 160
Ibs./acre/day loading indicate no significant change in solids in the
second cell. Under the 320 Ibs./acre/day loading the percent removal
is generally negative indicating an increase in the second cell. The
removal is also negative at the 900 Ibs./acre/day load. These can be
attributed to an abundant growth of algae in the second cell.
The chemical tests shown in Table 15 indicate no significant changes
except in pH, DO and COD. The pH in the second cell system tends to
increase from 0.5 to 1.0 units as preliminary loading increases. This
is indicative of changes in C0£ concentrations due to algal growth. There
is a significant change in DO concentration in the second cell. From all
three loading systems of the first cell the DO increased to saturation in
cell two. Again the algal cycle produced a variation in DO during the
day as shown by testing in cell one. A sample secured at noon was
considered average.
The results of the COD test under second cell conditions indicate a
reduction of oxidizable organic matter only in the absence of algae. For
example, only after the 160 Ibs./acre/day loading was there a decrease in
COD. During this test loading no algae were produced. However, after the
320 and 900 Ibs./acre/day loading the COD increased. Under these loadings
significant algae production occurred.
Second Cell Conclusions
Test results from the second cell indicate little increase in efficiency
over the first cell performance. In addition, algal growth is not
inhibited in this cell; in fact, the rate of algal production was very
high. This is indicated by the increase in BOD and COD in this cell.
Table 12 indicates the difference in BOD readings with and without algae.
The BOD is higher if algae is included. Although the nuisance or
pollutional effect of releasing this large algal production into a
river is generally not considered serious, the esthetic value of the
river is considerably diminished for many miles downstream.
Although at first sight there seems to be little reason for second cell
operation, day to day testing indicates that the BOD, COD, DO and pH from
the effluent of the first cell vary from the average values given in the
Tables. A second cell operation without algae would tend to dampen out
this variation. A second and more important feature of the second cell
67
-------
TABLE 14
SUMMARY Of AVERAGE PHYSICAL TEST RESULTS
AERATED PILOT LAGOON
SECOND CELL
Aerated Lagoon -
TS (mg/1) Influent
Effluent
TVS (mg/1) Influent
Effluent
TSS (mg/1) Influent
Effluent
VSS (mg/1) Influent
Effluent
Aerated Lagoon -
TS (mg/1) Influent
Effluent
TVS (mg/1) Influent
Effluent
TSS (mg/1) Influent
Effluent
VSS (mg/1) Influent
Effluent
Aerated Lagoon -
TS (mg/1) Influent
Effluent
TVS (mg/1) Influent
Effluent
TSS (mg/1) Influent
Effluent
VSS (mg/1) Influent
Effluent
No Influent - First
160 Ibs. /acre /day
1061.0
1050.0
271.0
210.0
51.0
47.0
37.0
37.0
No Influent - First
320 Ibs. /acre/day
1301.0
1336.0
320.0
285.0
107.0
228.0
92.0
146.0
No Influent - First
900 Ibs. /acre /day
1350.0
1751.0
295.0
335.0
67.0
140.0
62.0
130.0
Cell Loading Was
% Removal
% Removal
% Removal
% Removal
Cell Loading Was
% Removal
% Removal
% Removal
% Removal
Cell Loading Was
% Removal
% Removal
% Removal
% Removal
1
22
8
0
-2
11
-110
-60
-30
-13
-no
-no
68
-------
TABLE 15
SUMMARY OF AVERAGE CHEMICAL TEST RESULTS
AERATED PILOT LAGOON
SECOND CELL
Aerated Lagoon - No Infl
Alkalinity (mg/1)
Hardness (mg/1)
PH
2
S04~ (mg/1)
N03-' <„/!)
P04~3 (mg/1)
DO (mg/1)
COD (mg/1)
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
uent - First Cell Loading Was
160 Ibs./ 320 Ibs./ 900 Ibs./
acre/day acre/day acre/day
314
319
610
568
7.7
8.2
437
430
8.0
4.0
17
20
7.0
11
102
84
290
274
772
756
8.1
8.6
875
940
3.7
1.0
15
16
3.5
8
163
186
236
230
870
1150
7.7
8.6
1000
1500
0.0
0.0
8.4
8.6
3.1
5.5
145
250
69
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concerns coliform reduction. As indicated in Table 13 the coliform count
is significantly reduced by second cell operations. This feature is
important assuming pathogenic organisms are reduced at the same or faster
rates. A third feature of second cell operation is the trend toward
saturated oxygen levels in cell two. Of course this varies in presence
of algae.
70
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SECTION VIII
ACKNOWLEDGMENTS
The support and advice of
Mr. Art Williamson -- State Sanitary Engineer,
Mr. Jim Nelson -- City Engineer, and
Mr. Ray Cheesebrough — Department of Water and Sewage
is noted and appreciated.
A special thanks is extended to Mr. Carl Hodgkinson, Control Sales,
Inc., of Denver, Colorado, who supplied the aeration equipment, proved
invaluable in operation, reviewed the data, and made many useful
suggestions.
Several graduate students were supported by this project and received
their Master's Degrees in Civil Engineering. Among these are: Mr.
Barrett L. Mint!ing, Mr. Harry Miller, Mr. David Bostrom and Mr. Robert
Kerr-
The support of the project by the Environmental Protection Agency and
the help provided by Dr. Robert L. Bunch, Project Officer, is noted
and appreciated.
71
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SECTION IX
REFERENCE
1. Middleton, P.M., Bunch, R.L., "A Challenge for Wastewater Lagoons"
a paper presented at the Second International Symposium for Waste
Treatment Lagoons, Kansas City, Missouri, June 1970.
2. Anon - Symposium on Waste Stabilization Lagoons, August 1960,
Kansas City, Missouri.
3. Stumm, Werner, Morgan, J.J. "Stream Pollution by Algal Nutrients"
Transactions of the Twelfth Annual Conference in Sanitary Engineering,
University of Kansas pp. 16-26 (1962).
4. Wilson, J.F., Jr. "Fluorometric Procedures for Dye Tracing", Techniques
of Water Resources of the United States, Geological Survey, Chapter
A12, Book 3, Applications of Hydraulics, 1968.
5. Standard Method for the Examination of Water and Wastewater. 12th
Edition, American Public Health Association, Inc. New York, 1965.
6. Moore, E.W., Thomas, H.A., and Snow, W.B., "Simplified Method for
Analysis of BOD Data" Sewage and Industrial Wastes 22_ pp. 1343-1353
(1950).
7. Fair, Gordon M., and Geyer, John C., Water Supply and Waste Water
Disposal. John Willey and Sons, Inc., New York, N.Y., 1954, pg. 525.
73
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
3. Accession No.
W
4. Title
SUPPLEMENTARY AERATION OF LAGOONS IN RIGOROUS
CLIMATE AREAS,
7. Author(s)
Champ1in, R. L.
9. Organization
The University of Wyoming
Laramie, Wyoming 82070
12. Sponsoring Organization
IS. Supplementary Notes
S. Report Date
6.
8. Performing Organization
Report No.
10. Project No.
17050 DVO
11. Contract/Grant No.
13. Type of Report and
Period Covered
16. Abstract
A field investigation, using a pilot scale unit, determined the effects of
supplementary aeration on Waste Stabilization Lagoon performance. The climate
can be considered rigorous (high altitude - cold temperatures). Both complete
mix and batch experiments were conducted. Air flow was constant, and loading
ratesj, both hydraulic and process, were changed from 160 to 900 Ibs BOD/acre/day.
INKA aeration system performed the two functions.
The BOD reduction varied from 72% to 85% under three different loading conditions.
The temperature of the aerated sewage was below 12°C. Solids removal was
significant. No settleable solids resulted from the system, indicating no bio-
flocculation. Change in total bacterial counts were roughly proportional to the
change in loading.
Tests on a second cell, functioning as a batch process, indicated an increase
of oxygen levels to saturation level. Significant algae production also occurred
at temperatures of 6°C. Coliform bacteria were reduced to about 10/ml in the
second cell. Total bacteria counts remained about the same as indicated in
first cell tests.
17a. Descriptors
^Oxidation Lagoons, Aeration
17b. Identifiers
*Waste Stabilization Lagoons, ^Supplementary Aeration, Biochemical Oxidation
Demand removal, Solids removal, Coliform Bacteria removal
17c. COWRR Field & Group
18. Availability
Abstractor Champ 1 in,
19. Security Class.
(Report)
20. Security Class.
(Page)
21. No. of
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 20240
R. L. institution University of Wyoming
WRSIC T02 (REV. JUNE 197l)
GPO 913.26!
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