Upgrading
Existing
Lagoons
Prepared by:
US Environmental
Protection Agency
Office of Research
& Development
Environmental
Research Center
Cincinnati, Ohio
Prepared for
US Environmental
Protection Agency
Office of
Technology Transfer
Design Seminar
Program
-------
UPGRADING EXISTING LAGOONS
Prepared for the
U.S. Environmental Protection Agency
Technology Transfer Design Seminar Program
by
Ronald F. Lewis Ph.D.
and
John M. Smith
October 1973
National Environmental Research Center
Advanced Waste Treatment Research Laboratory
Office of Research and Development
Cincinnati, Ohio
-------
TABLE OF CONTENTS
Page
INTRODUCTION 1
DISTRIBUTION AND CLASSIFICATION
OF LAGOONS 1
BASIC REMOVAL .MECHANISMS AND OPERATIONAL
CHARACTERISTICS OF LAGOONS 2
SUMMARY OF EXISTING LAGOON PERFORMANCE AND
CHARACTERISTIC EFFLUENT QUALITY 3
UPGRADING OBJECTIVES 16
TECHNIQUES AVAILABLE TO IMPROVE PERFORMANCE
OF LARGE LAGOONS 17
Process Modifications 17
Complex Tertiary Treatment Systems 18
TECHNIQUES SUITABLE FOR SMALL LAGOONS 19
Process Modifications 19
Simple Low Cost Polishing Techniques 20
slow rock filter 21
land application of lagoon effluents 24
intermittent sand filtration 26
Other Suggested Methods for Algal Removal 28
chemical addition 29
microstrainers 29
chlorination-clarification 29
biological predators of algae 30
-------
INTRODUCTION
This short discussion on upgrading lagoons will attempt to cover briefly
the description of the types of lagoons and numbers that are in use, the
advantages of using lagoons as a means of secondary treatment, the performance
problems associated with lagoons, and the adequacy of existing lagoons to
meet the new secondary treatment effluent standards (1). Both proven methods
and emerging technologies for upgrading lagoon performance will be discussed
along with case history information where available.
DISTRIBUTION AND CLASSIFICATION OF LAGOONS
Approximately 90% of the wastewater lagoons in the United States are
located in small communities of 10,000 people or less. During the period of
1940-1973 wastewater lagoons rapidly gained popularity as a means of treating
wastewaters from isolated industries such as meat packing plants and from
small rural communities. A recent report by George Barsom (2) shows that in
1945 there were 45 lagoons treating municipal wastes while by 1960 the number
of lagoons had increased to 4,476. To this number must also be added the
many privately owned lagoons treating wastewaters from individual motels,
schools, trailer parks, and feed lots that have not been listed in state or
national registers. The geographical distribution of lagoons as reported by
Barsom in 1973 is shown in Figure 1. The proliferation and acceptance of
lagoon treatment for small municipalities especially in the Western and
Southern portions of the United States is evident from this figure.
RETA
[i states indica
^ ting preference for
lagoons
H states indicating preference
away from lagoons
EXTENT. USE AND
ACCEPTANCE Of MUNICIBAL
LAGOONS
FIGURE 1. Geographical Distribution, Extent, Use, and
Acceptance of Municipal Lagoons
-1-
-------
The types of lagoons presently being used may be divided into five
distinct classes 1) high rate aerobic ponds, 2) facultative ponds,
3) anaerobic ponds, 4) maturation or tertiary ponds, and 5) aerated lagoons.
These are described in detail in the Brown and Caldwell report on upgrading
lagoons (3). Lagoons have also been classified according to depth; rate of
organic loading; inlet, flow-through and inlet-outlet arrangements; number
of divisions of the total lagoon area and the flow-through pattern of the
wastewater among these cells; and the method of effluent disposal.
BASIC REMOVAL MECHANISMS AND OPERATIONAL CHARACTERISTICS OF LAGOONS
In order to determine whether upgrading methods are needed and what types
of upgrading might be successful, we should first understand the basic bio-
logical and physical removal mechanisms that take place in typical facultative
lagoon systems.
As raw wastewater enters a facultative lagoon, the solids in the waste-
water usually settle in an anaerobic layer on the bottom of the pond. Some
of these solids will undergo anaerobic decomposition similar to that in an
anaerobic digester with subsequent release of methane gas, while a portion of
the solids always remain as incompletely digested material. The soluble
organic material and colloidal solids which are either brought in fresh by
the incoming wastewater or scoured from the bottom of the lagoon by intra-
pond mixing due to wind, or water turnover caused by seasonal temperature
changes of the waters, are broken down by bacterial action in the aerobic
upper layers of the lagoon according to the following generalized equation:
CH20 + 02 bacteria»C02 + H20
(organics)
Some of this material is incorporated into the bacterial cells that
grow and with their settling add to the organic matter at the bottom
anaerobic zone of the lagoon. The C02 given off by the bacteria, along with
the bicarbonate of the incoming wastewater and the C02 introduced into the
lagoon by surface reaeration by wind action is utilized by algae in the
presence of sufficient sunlight and inorganic nutrients such as phosphorus,
nitrogen, and iron to produce oxygen and additional algae cells according
to the following equation:
C02 + 2H20 + energy + nutrients alftae».CH20 + HoO + 02
(algae)
This photosynthesizing action takes place during the daylight hours.
At night the algae use oxygen and oxidize some of the compounds they have
produced and stored while photosynthesizing. The net effect of this carbon
cycling mechanism, especially with the long detention times usually associated
with wastewater lagoons, is 1) to cause a considerable deposition of the
solids originally present in the raw wastewater, 2) cause some loss of the
organic load of the raw wastewater as C0~ or methane lost to the atmosphere,
-2-
-------
and 3) cause a conversion of much of the soluble inorganic and organic
material into the formation of bacterial and algal, cell material.
Surprisingly, both the advantages and disadvantages of using lagoons
for wastewater treatment are intimately connected with this "natural"
functioning of the system. The advantages of lagoons as a secondary treatment
system are that they do not require full time control by men with extremely
high technical skills, and when properly designed, they can handle considerable
variations in organic and hydraulic loadings with little effect on the effluent
quality.
The disadvantages are 1) the large surface area and volumes required for
this complex biological process, 2) the odors that can develop if anaerobic
conditions occur either consistently due to overloading, or at certain periods
of time when cold temperatures and ice cover have prevented significant algal
development and surface reaeration, or after massive algal growths have occurred
resulting in decaying algal mats on the surface and 3) the severe problem of
excessive algae in the effluent creating a significant BOD and suspended solids
load on the receiving waters.
SUMMARY OF EXISTING LAGOON PERFORMANCE AND CHARACTERISTIC EFFLUENT QUALITY
A comprehensive analysis of the performance of lagoons is very difficult
because of the lack of consistent, reliable information and analytical data.
Since many of our existing lagoons are located in small communities that do
not have .highly trained operators, very few laboratory analyses are performed
on either the influent or effluent from these lagoons. Typical operational
reports from lagoon treatment works will include subjective statements such
as "odor problems are not present" or "the lagoon is performing satisfactorily."
The Barsom survey (2) reported that only 28 of 50 states required routine
monitoring of influent loading parameters. The problems most often cited by
state engineers were odor problems (all 50 states) followed by short circuiting
(23 states) and finally by algae problems (21 states).
One of the major obstacles in improving the application of lagoon tech-
nology in the past has been the failure of engineers to relate lagoon perfor-
mance to causative factors, and to modify established design criteria
accordingly. This has created a lack of confidence in the treatment technique
in general, and a reluctance on the part of regulatory authorities to endorse
new applications of lagoon treatment systems.
The state of the art report on lagoon technology by Barsom (2) is the
most comprehensive study of lagoon performance presently available. Information
was assembled during this study by questionnaires and direct contact of all
state water pollution control agencies, municipalities, and independent
researchers. The investigation evaluated data on lagoon performance for all
50 states and approximately 3,000 lagoon installations. Data of even marginal
validity was available from less than 200 of these installations. Figure 2
shows the national average median effluent values for the BOD and suspended
solids of facultative lagoons, aerated lagoons, oxidation ditches, and
tertiary lagoons.
-3-
-------
The average median effluent BOD ranged from 23 mg/1 to 42 mg/1 and the
average median effluent suspended solids ranged from 37 to 67 mg/1. Figures
3 and 4 indicate the BOD and suspended solids levels in facultative lagoons in
different geographical areas of the United States showing the average median
in each area and the range of values found in that area. The BOD ranges from
10 to 200 mg/1 with the average median ranging from 25 to 75 mg/1. The average
median effluent suspended solids ranged from 40-540 mg/1. For aerated lagoons
(Figures 5 and 6) the average median BOD values by geographic region varied
from 30-80 mg/1, and the average median suspended solids varied from 60 to
210 mg/1. For tertiary lagoon systems (Figures 7-8) the average median BOD
values for the nine geographical areas varied from 10 to 100 mg/1 and the
average median suspended solids varied from 20 to 250 mg/1. Nitrogen and
phosphorus values were around 20 mg/1.
£ «0
Ditch Lvgoon
I BOD
1 S S
FIGURE 2. Average Median Lagoon Effluent Values
-4-
-------
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Test Location
FIGURE 3. Facultative
Lagoon Biochemical
Oxygen Demand
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Test Location
FIGURE 4. Facultative
Lagoon Suspended
Solids
LEGEND
1. Southwest Region
2* South Central Region
3. Southeast Region
4. Ohio Basin
5. Great Lakes Region
O)
E
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6
5
4
3
2
1
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6. Missouri Basin
7. Middle Atlantic Reg
6. Northeast Region
9. Northwest Region
! Range
Average Effluent
Median
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Test Location
FIGURE 5. Aerated
Lagoons Biochemical
Oxygen Demand
01
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Test Location
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rest Location
FIGURE 6. Aerated
Lagoons Suspended
Solids
FIGURE 7. Tertiary FIGURE 8. Tertiary
Lagoons Biochemical Lagoons Suspended Solids
Oxygen Demand
-5-
-------
One of the most important observations in examining facultative lagoon
effluents is the consistently demonstrated contribution of effluent algae
on both effluent BOD and suspended solids. Studies by Neel et al. (4) have
shown that approximately 65% of the effluent BOD from a facultative lagoon
is due to suspended solids, the majority of which is algae. The variability
of effluent BOD, and increase in BOD due to algae is supported by studies
of McKinney, Dornbush and Vannes (5) as shown in Table I, and also by studies
conducted at Fayette, Missouri (4) in 1957-1958 as shown in Table II. These
investigations illustrate that the BOD of lagoon effluents are generally
higher during the summer than during the winter periods due to the higher
concentration of algae discharged during the summer months. Table II also
shows that the coliform bacteria are greatly reduced during the low algae
discharge or winter time periods. Disinfection will probably be needed
however for most lagoon effluents to insure that the secondary effluent
standard of 200 fecal coliforms/per 100 ml is consistently met.
The case history of the lagoon treatment plant at Logan, Utah does show
that an extremely well designed series of facultative lagoons can meet the
secondary effluent standards for BOD. This system treats the wastes from the
city of Logan, Utah which has a population of about 40,000 including some
light industry, and Utah State University which has an enrollment of about
8,000 students. The system was completed in late 1967 and has been operating
as a continuous flow unit since March of 1968. There are 465 acres of
lagoons divided into 7 cells as shown in Figure 9. Cells Al-Bl and A2-B2 are
dual parallel systems each receiving half of the incoming waste; the flow
from both Bl and B2 combine in cell C and the series continues through cells
D and E and then to the chlorination facility before discharge. The average
raw sewage influent rate varies from 5.9 to 14.7 mgd depending on the rainfall
variations and the extent of lawn watering.
The operational results for an 18 month period are shown in Table III.
These results indicate that this type of system can constantly meet the
secondary effluent requirement of less than 30 mg/1 of BOD. Although no
suspended solids data is available from this initial study period, data taken
in July through October of 1973 indicate a wide variation in effluent suspended
solids, varying from as low as 6.7 mg/1 to as high as 103 mg/1. This raises
the question as to whether the lagoon system had reached equilibrium during
the earlier study period.
Although facultative lagoons have been shown to typically discharge
higher effluent suspended solids and BOD than single-stage aerated lagoons,
the seasonal discharge pattern for the aerated lagoons is quite different than
for the facultative lagoons. The typical discharge pattern for a single-cell
aerated lagoon is illustrated by the following performance case history for
the city of Winnipeg, Canada (6).
The investigation of aerated lagoon performance in Winnipeg was conducted
by the Waterworks and Waste Disposal Division of the Metropolitan Corporation
of Greater Winnipeg from January 1, 1968 through September 30, 1969. The
objective of this lagoon demonstration project was to determine the feasibility
-6-
-------
TABLE I
BOD Data Collected at Five California Oxidation Ponds (5)
Pond
BOD Load
(Ibs/acre/day)
BOD Influent
(mg/1)
BOD Effluent
(mg/1)
Woodland
Winter
Summer
Esparto
Winter
Summer
Shastina Sanitary
Winter
Summer
Los Banos
Winter
Summer
Or land
Winter
29
25
16
15
District
50
161
77
78
17
125
67
119
165
85
135
295
265
145
42
26
11
25
19
2
38
26
20
TABLE II
Cell 1 - Average Lagoon Effluent Results at a Lagoon
Loading of 20 Ibs. BOD/Acre/Day
Moiilb
1057
May
Juno
July
Aug.
Sept
Oct.
Nov.
Dec.
1058
Jan.
Feb.
Mor.
Apr.
May
Tra'-
21
29
33
20
22
16
8
3
3
2
0
14
20
i>ll
7.8- 0.2
H.'l-HUi
8.8-11.4
8.0- 0.11
g.7- 0.8
8.7-10.5
8.5- 0.1
7.0- 8.0
8.0- D.2
7.0- 8.0
8.4- 0.0
7.0- 8.0
8.0- O.S
00,
/Ik.
(inp^l)
07
122
54
70
80
32
12
32
10
CO
14
58
ncoi
Alk.
dim/I)
80
10
101
85
80
131
175
170
188
127
10-1
131
Oi (mi/1)
Av«
21
10
31
17
10
18
14
8
19
10
20
11
20
Mu
20
20
41
38
20
27
18
12
21
15
:io
20
30
Min
0
7
1
&
11
10
0
3
10
8
0
3
3
O. Bat. (%)
AVI
258
135
2HI
222
181
1'Jl
117
02
140
72
104
100
242
Mu
310
203
500
491
307
283
150
00
'174
100
245
200
3G8
Min
CO
00
10
02
125
02
74
21
73
58
75
25
30
HOD
-------
Cell
Al
A2
B|
B2
C
D
E
Totol
Woter
Surfoce
Area (Acres)
95.1
95.0
70.9
72.3
64.4
39.4
28.3
465.4
Effective Vol.
6' depth
24,542,000 ft.3
24,532,000
I8-,274,000 "
18,648,000 "
16, 194,000 "
10, 104,000 "
7, 242,000 "
119,536,000 ft.3
B2
Diffusers
Raw Sewage
Chlorination
Facilities
Effluent
FIGURE 9. Flow Diagram of Logan, Utah Lagoon
-8-
-------
I
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TABLE III
Summary of Lagoon Operating Data
Logan, Utah, August 1968 - October 1969
Based on Weekly Samples and Observations by Utah State University (a)
W
C
tn 0
U «
s |
W «
r«
0°
Z oS
Ave.
Flow
MGD
Raw
1968
Aug. 4 '13.2
Sept. 5 11.0
Oct. 4 8.3
Nov. 4 7. 2
Dec. 5 6.0
1969
Jan. 4 7. 6
Feb. 4 7.0
Mar. 5 5.9
Apr. 4 7. 1
May 4 11.5
June 5 13.3
July 4 14.5
Aug. 4 14.7
Sept. 4 12.6
Oct. 4 8.7
Effl.
MPN Coliforms/100 ml
Lagoon Effluent
Ave Range
Biochemical Oxygen Demand
(BOD5) -
Raw Sewage
Ave
12.5 12,483 230-24,000 28.9
9.0 98 15-240 83.0
8.1 31 2-38 73.5
6.6 4 2-9 109
5.9 ' 2 i-
c
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J 1! T3
o >- £
ca u
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> '£ d
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< _: w
0.0-6.6 68 16.7 22.0
0.0-24.0 81 40.0 17.5
0.0-2.9 108 26.8 11.5
1.0-3.4 124 34.5 5.7
1.4-6.4 149 43.7 3.0
0.4-3.6 118 30.3 2.1
0.4-6.0 128 27.3 . l.f
6. 8-21. b 1 13 28. 1 2. I
6.6-19.2 126 32.5 11.7
5. 4-1 5. 0 78 43. 6 19. 8
1 1. 4-41. 9 67 80. 6 20. 6
10.8-16.9 62 56.1 25.2
7.2-37.3 61 59.8 26.0
4.8-19.3 71 33.3 20.0
0.0-8.4 103 26.4 9.4
a Jones, Norman B. , Personal Communication
b 2 Samples Only - Deep Snow Prevented Access for Sampling
Notes: 1. Lagoon Operation Began Nov. 1967 with effluent discharge beginning in March 1968.
2. Chlorination facilities provided but not yet operated.
-------
of aerated lagoons for the complete treatment for the south area of Winnipeg,
and to determine the best of three alternate methods of lagoon aeration. The
general layout and aeration details of the demonstration lagoons which are
located adjacent to a conventional 3.0 Imgd(Imperial gallons) stabilization
lagoon in Charleswood are shown in Figures 10 and 11 respectively. Under
mormal operating conditions 1.5 Imgd of raw sewage flow is divided equally
into the three parallel 0.5 Imgd demonstration lagoons. The average effluent
BOD and suspended solids for the 21 month demonstration period are summarized
in Table IV. The design criteria for the three lagoons is shown in Table V.
The variation in effluent BOD and suspended solids from each of the three
lagoons over the 21 month test period is shown in Figures 12 and 13 respectively.
This data clearly illustrates the typical discharge pattern for this type of
lagoon. Both the effluent BOD and suspended solids tend to increase during
the winter months and decrease during the warmer summer periods.
While these figures indicate better general performance for this type of
lagoon than for facultative lagoons, the aerated lagoon effluent would not meet
the secondary treatment standard of 30 mg/1 of suspended solids on a consistent
year round basis without filtration or further treatment.
TABLE IV
Effluent Concentrations for Charleswood Demonstration Lagoons - 21 Month
Average
Air-Aqua
Surface Aerator
Air-Gun
BOD mg/1
37
38
34
SS mg/.l
34
39
34
In addition to the continuous discharge facultative and aerobic lagoons
that predominate in the Southwest and Southeastern portions of the United
States there are the no-discharge and intermittent discharge lagoon systems
that are commonly used in the North and Northwestern portions of the country.
The non-discharging lagoons that have an evaporative loss equal to or
greater than the sewage influent will meet and exceed the present secondary
effluent requirements. However, it is sometimes difficult to prevent odors
from occurring with these lagoons due to the noxious vegetative growths in
the shallow areas as the pond area expands and contracts during the wet and
dry periods.
-10-
-------
EXISTING EFFLUENT
CONTROL CHAMBER-
OUTFALL
-*
EFFLUENT TO^
ASSINIBOINE RIVER
/
FROM CONVENTIONAL
CELL f
/*
EFFLUENT CONTROL CHAMBER
(LIQUID LEVEL CONTROL, AUTOMATIC SAMPLING)
(AND FLOW MEASURING)
RECIRCULATION
PIPING
SURFACE AREA'3.4AC.
LIQUID DEPTH. 10 FT.
'
AIR A
AQUA
CELL No.
SURFACE AREAt S.SAC
LIQUID DEPTH IO FT
SURFACE
AERATOR
SURFACE
AREA.4.SAC.
LIQUID
DEPTH HIFT.
INFLUENT CONTROL CHAMBER
{AERATED CELLS)
FORCEMAIN
t M-a-D-
CONVENTIONAL CELLS
PUMPING STATION
NOTE
M-G-D- - IMPERIAL UNITS
SCHEMATIC OF AERATED
LAGOON PROCESSES
FIGURE 10. Charleswood Demonstration Lagoons
-11-
-------
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NOTE
AT BASIN FLOOR.
PLAN
SEC.'I-I*
AIR AQUA
AIM AOUA TUBING-
AERATED LAGOON PROCESSES
EQUIPMENT DETAILS
FIGURE 11. Charleswood Demonstration Lagoons Aeration
and Equipment Details
-------
TABLE V
Design Criteria - Charleswood Demonstration Lagoons
Parameter
Average Design Flow (each lagoon)
Influent 5-Day BOD 20°C
Influent Suspended Solids 20°C
Oxygen Utilization Factor a1
(Ibs. oxygen required per Ib.
5-day BOD removed)
Operating Dissolved Oxygen
Effluent Temperature - Winter
- Summer
Influent Temperature - Winter
- Summer
Mean Ambient Air Temperature
- Winter
- Summer
Treatment Efficiency Required
Retention Time - Air-Aqua
- Surface Aerator
- Air-Gun
Operating Depth - Air-Aqua
- Surface Aerator
- Air-Gun
Volume - Air-Aqua
- Surface Aerator
- Air-Gun
Mixing Requirements for Surface Aerators
Process Loading - Air-Aqua
- Surface Aerator
- Air-Gun
Value and Units
0.5 Imgd
250 mg/1
180 mg/1
1.50
2.00 mg/1
32°F
75°F
48 °F
65°F
-16°F
+75°F
90%
30 days
20 days
20 days
10 ft.
11 ft.
17 ft.
15 x 106 gal.
10 x 100 gal.
10 x 106 gal.
0.016 HP/1000 gals.
0.52 Ibs. BOD5/1000 ft3/day
0.78 Ibs. BOD5/1000 ft3/day
0.78 Ibs. BOD5/1000 ft3/day
-13-
-------
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LAGOON PERFORMANCE BO Dg
FIGURE 12. Variation in Effluent BOD
Demonstration Lagoons
- Charleswood
-14-
-------
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APR
MAY
JUNE
_ _-
-
k _ .
_ .
JULY
1
AUO.
SEPT.
LAGOON PERFORMANCE
SUSPENDED SOLIDS
FIGURE 13. Variation in Effluent Suspended Solids
Charleswood Demonstration Lagoons
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Another system that appears to meet the secondary effluent standards is
the controlled, intermittent discharge type of lagoon treatment practiced in
Michigan and North Dakota. Here, the facultative lagoons are operated in
series. Sufficient capacity is planned so that all the wastes can be held in
the lagoons for a period of six months to one year. During the spring and/or
fall period, when algal growth is at a low level, and after the lagoon contents
have stabilized (recovered from the effects of low dissolved oxygen during the
ice cover of winter to early spring), the final cell is isolated from the
preceding cells. This insures no subsequent short circuiting of any raw sewage
for this period of time. The level of dissolved oxygen is measured in the
final cell and in the stream along with the volume of flow in the stream.
When all conditions are considered correct the effluent line to the receiving
water is opened and the contents of the final cell are discharged in a period
of two weeks to one month.
Information presented at the Second International Symposium for Wastewater
Treatment Lagoons by Richmond (7) indicated that the statistical mean effluent
BOD for thirty three intermittent lagoons in the state of Michigan ranged from
9 to 19 mg/1 over a four year period from 1965 to 1969. The statistical mean
effluent suspended solids ranged from 26 to 47 mg/1 over this same period.
UPGRADING OBJECTIVES
The foregoing discussions and analysis of the effluent characteristics of
the most commonly employed lagoons clearly demonstrate the wide variability and
marginal effluent quality that can be expected from these systems. Although
there are a number of isolated cases where both facultative and aerobic lagoons
have performed satisfactorily, the overwhelming majority of the existing lagoons
in the United States must be upgraded to meet the new Environmental Protection
Agency standards for secondary and best practicable treatment.
The first consideration in examining the available lagoon upgrading.
technology is to evaluate the techniques that can be employed to meet the new
secondary treatment standards.
The new regulations describing the minimum level
of effluent quality attainable by secondary treat-
ment in terms of the parameters of biochemical
oxygen demand (BOD), suspended solids (SS), fecal
coliform bacteria, and pH are given in the Federal
Register (1). These regulations state that the five
day BOD and suspended solids shall not exceed an
arithmetic mean value of over 30 mg/1 for effluent
samples collected in a period of 30 consecutive days.
For effluent samples collected in a period of seven
consecutive days the arithmetic mean of the values
shall not exceed 45 mg/1. The arithmetic mean of the
value of the effluent samples collected in a period
of 30 consecutive days shall not exceed 15% of the
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arithmetic mean of the values for influent samples
collected at approximately the same times during the
same period (85% removal). The geometric mean of the
value for fecal coliform bacteria for effluent samples
shall not exceed 400 per 100 milliliters for samples
collected in a period of seven consecutive days. The
effluent values for pH shall remain within the limits
of 6.0 to 9.0.
In addition to examining upgrading technology capable of meeting secondary
treatment standards we must also consider techniques capable of meeting the
proposed best practicable treatment standards, and of eventually meeting the
national goal of non-pollution discharge by 1985. In many cases removal of
phosphorus and nitrogen will be required to meet specific stream standards
that in some locations are much more stringent than the national standards of
secondary or best practicable treatment.
The subsequent sections of this report will discuss the upgrading techniques
that are currently being used, along with a short discussion of some of the
newer emerging technologies that may soon become practical.
TECHNIQUES AVAILABLE TO IMPROVE PERFORMANCE OF LARGE LAGOONS
Process Modifications
In general, process modifications should be viewed as the first approach
in providing moderate increases in lagoon efficiency, and in eliminating or
reducing the most common operating problems or design deficiencies of existing
lagoons. Process modifications such as 1) deepening the pond, 2) decreasing
or redistributing the BOD loading, 3) increasing the number of ponds in the
system, 4) pond recirculation, 5) improvement of the feed and withdrawal methods,
6) special methods for construction and operation of lagoon transfer inlets
and outlets, 7) improved pond dike construction and maintenance procedures and,
8) supplemental aeration and mixing have been shown to be successful and are
discussed in some detail in the Brown and Caldwell report (3). The primary
purpose of these modifications are to:
1) prevent short circuiting of the wastewater
2) prevent organic overloading leading to anaerobic
conditions and odors
3) provide supplemental aeration when the climatic
conditions are unfavorable for algal development
and oxygen production, or when specific industrial
wastes such as canneries will periodically introduce
a very high load into an otherwise satisfactory
municipal lagoon system
4) allow a longer detention period for the sedimentation of
the bacterial and algal cells formed in the lagoon system.
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The recently formed EPA lagoon task force (8) has recognized the advan-
tages of three-celled lagoon systems and is considering making this a require-
ment for newly constructed continuous discharge lagoons. This will allow
some flexibility in the operation as the individual cells can be operated in
series or with cells 1 and 2 in parallel while 1-3 and 2-3 are in series.
Also, if it is necessary to repair the dike or perform any other operation
that would require emptying of one cell, there would be at least two cells
to operate in series.
The added flexibility and advantages of multi-celled lagoons have been
recognized by several states. In Utah for example, some lagoon systems have
up to six cells. Modification of the withdrawal outlet from the final cell
to allow the effluent to be withdrawn at various depths has also been recommended
since there are times when the concentration of algae is different at various
depths of the final cell.
Complex Tertiary Treatment Systems
The more complex tertiary upgrading techniques are considered applicable
to large secondary lagoons that must produce a relatively high quality effluent
for discharge to a receiving stream or for a particular water reuse application.
In many cases nitrogen and phosphorus removal may be required in addition to
low BOD and effluent suspended solids. These tertiary techniques normally
require a significant capital investment, are costly to operate, and require
the attention of highly skilled operators supported by a well equipped analytical
laboratory.
The preferred treatment methods are usually chemical coagulation with
either alum or lime followed by sedimentation or dissolved air flotation and
either pressure sand filtration or dual media gravity filtration to reduce the
final effluent turbidity. A detailed account of the development of a system
for the wastewater treatment plant at the City of Stockton, California is given
in the Brown and Caldwell report (3). Tertiary treatment studies of the 240
acre oxidation ponds at Lancaster, California presented by Dryden and Stern (9)
summarize the results of a series of coagulation studies along with a cost
analyses for a tertiary treatment system that includes alum coagulation followed
by gravity sedimentation, dual media filtration, and chlorination. Table VI
shows that for this system the suspended solids was reduced to 6 mg/1, BOD
to below 10 mg/1, and coliform bacteria to less than 1.8 MPN/100 ml. For a
500,000 gpd facility the capital cost of the plant was estimated at $150,000
and operating costs at $184 per million gallons. Chemical costs account for
about $70 of the $184. For a larger facility of 3 million gallons per day,
the total capital, operation, and maintenance costs were estimated to be about
$150 per million gallons. This processed water was to be used for recreational
lakes in place of imported water that would have cost about $200 per million
gallons.
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TABLE VI
Results of Tertiary Treatment of
Lancaster Oxidation Pond Effluent'3)
Comparison of Pond 3 and Processed Water Characteristics
Characteristics Pond 3 Water Product Water
pH
Turbidity (JTU)
Total Alkalinity (mg/1 as CaC03)
Hardness (mg/1 as CaCC^)
Suspended Solids (mg/1)
Dissolved Solids (mg/1)
Chemical Oxygen Demand (mg/1)
Biological Oxygen Demand (mg/1)
Dissolved Oxygen (mg/1)
Ammon ia -N (mg/ 1 )
Organic-N (mg/1)
Nitrate-N (mg/1)
Nitrite-N (mg/1)
Total Nitrogen (mg/1)
ABS (mg/1)
Phosphate (mg/1)
Algae (counts/ml)
Confirmed Coliform (MPN/100 ml)
Chlorine Residual (mg/1)
Sulfate (mg/1)
8.3
90
260
80
75
575
250
38
0.1-40
0.1-20
7-20
1-4
0.1-12
7-20
3
40
200,000
7,900
-
60
6.7
4
95
100
6
575
50
<10
7-15
0.1-20
1-3
1-4
0.1-12
3-20
3
0.25
7,000
<1.8
0.2-0.5
240
a - In this study Pond 3 is the final cell of a
four stage pond system that receives primary effluent
TECHNIQUES SUITABLE FOR SMALL LAGOONS
Process Modifications
The process modifications previously described for large lagoon systems
may also be employed for small systems. Where the climate, receiving water
conditions, and volume of wastewater to be treated are suitable, enlargement
and modification of small lagoons to intermittent discharge or complete
retention (zero discharge) may be considered. The intermittent discharge
lagoons in Michigan are planned on a basis of 1 acre of lagoon surface per
100 people served and with a loading of 20 Ib. of BOD/acre/day. Thus, it is
possible to provide for complete retention of the wastewater during all but
two weeks in the fall and two weeks in the spring. A lagoon system, capable
of storage through the long spring-summer-fall period, has plenty of capacity
for the winter period when the lagoon process is least effective because of
the ice and snow cover, drastically lowered water temperatures, and reduced
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effects of sunlight. In fact, sufficient storage is normally planned to extend
the retention period long enough beyond the time when the ice breaks up to
permit recovery of the water quality from any effects such as anaerobic condi-
tions or water turnover caused by the subsequent rewarming of the lagoons.
This type of lagoon facility must have a capability of 1) controlling water
levels through a wider than usual range, 2) must have a controlled drawoff
capability, and 3) must have flexibility permitting feeding, or withdrawal from
any single cell. The drawoff from the final cell is normally planned for a
time of low algal growth and best possible water quality.
It is not surprising that the intermittent discharge lagoon systems have
been used most extensively in North Dakota, Michigan, and parts of Canada. As
well as having the need for retention during the winter when treatment capabili-
ties are reduced, these areas may be described as regions without excessive
rainfall and where algal growth takes place predominantly during the late spring
to early fall. At these northern latitudes there is much less algal growth in
early spring or late fall. This would not necessarily be true for lagoon systems
located in Mississippi or South Carolina. Extensive rainfall either by direct
runoff into the lagoons or by large volumes of infiltration/inflow into the
sewers would make the size of the lagoons required for intermittent discharge
or complete containment too large for practical application. This also explains
why complete containment has been practiced primarily in western Kansas and
desert regions. For complete containment facilities, care must be exercised to
prevent extensive growth of mosquitoes or flies, and to prevent nuisance odor
conditions. These plants should be located well away and preferably down-wind
from residential areas.
Simple Low Cost Polishing Techniques
As was mentioned earlier, an effective method of algae removal from effluents
is required for continued use of oxidation ponds as secondary treatment facilities.
For small communities, the financial resources and operator sophistication needed
for the successful use of the tertiary treatment methods suggested for the large
lagoon systems does not exist. To be effective for a small community the algal
removal system employed must 1) be either self operating or require operator
attention for only short periods of time at regular intervals (i.e. weekly);
2) require only equipment commonly used by the utility department of the small
community that operates and maintains the facility; and 3) use as expendable
materials in the process only inexpensive materials that are safe and convenient
to handle, and easy to dispose of after use.
In early 1973 the Environmental Protection Agency's Office of Research and
Development requested proposals for developing such an inexpensive, reliable
method for algae removal from lagoon effluents from small communities. After
reviewing over 25 separate proposals, a decision was made to fund three
proposed methods; 1) a slow rock filter to be studied at University of Kansas,
2) a land application system at Utah State University, and 3) an intermittent
sand filtration system at Utah State University. A description of each of these
approaches is given below.
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Slow Rock Filter
Research on the possibility of utilizing a slow rock filter as a means
of removing algae from the final effluent of wastewater lagoons is being
conducted by Dr. W. O'Brien and Dr. R. McKinney, both from the University of
Kansas at Lawrence, Kansas at the wastewater lagoon system in the town of
Eudora, Kansas which is about 32 miles west of Kansas City. Eudora is a town
of 2200 people. The experimental lagoon system utilizes 2 of 3 existing cells
at the Eudora plant site as shown in Figure 14. The average dry weather flow
is 120,000 gallons per day and the BOD load is approximately 32 Ib. of BOD
/acre/day.
ROCK FILTER EFFLUENT
SECONDARY
LAGOON
10" INFLUENT LINE
FIGURE 14. Eudora, Kansas Existing Lagoons and
Experimental Filter
Preliminary studies with various sized gravel and rock set up as an upflow
slow filtration unit in the laboratory or in 55 gallon barrels at the lagoon
site have given encouraging results for the removal of BOD and suspended solids
from the final effluent. Table VII shows the average performance for this
upflow submerged rock filter operated on a 24 hour hydraulic detention time
at a surface loading rate of 0.008 gpm/ft2.
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TABLE VII
Average Performance of a Submerged Rock Filter
Operated on a 24-Hour Hydraulic Detention Time
by the University of Kansas
Characteristic
COD, Total mg/1
COD, Soluble mg/1
PH
% Transmittance at 425 Microns
Ammonia Nitrogen mg/1*
Nitrite Nitrogen mg/1*
Nitrate Nitrogen mg/1*
Total Phosphorus mg/1**
Influent
109
71
7.8
70
4.74
0.37
0.07
0.77
Effluent
69
52
7.7
81
3.63
3.57
0.18
0.73
Note: Samples collected over 44 days of operation
* Nitrogen measurements mg/1 as N collected over
last 22 days of operation
** Total phosphate mg/1 as P
Algae removal by the filter is brought about by a combination of
physical and biological mechanisms. The voids between the rocks produce
numerous small settling chambers while the rock surfaces provide a large
area for biological growth. When the algae settle from solution they become
attached to the rocks and undergo endogneous metabolism. This releases
soluble substances that can be used by other microorganisms which colonize
the rock surfaces. The net rate of sludge increase is very slow because of
the extremely small supply of available nutrients. The tests with the upflow
filter for a 44 day period showed almost no solid material in the effluent
and very little sludge on the rocks when the unit was disassembled after the
experiment. It has been postulated that possibly zooplankton and microcrustaceans
forms help consume the bacteria and algae. Additional sludge build-up would
undoubtedly occur over extended periods of time. However, this sludge would
be primarily non-biodegradable organic and inorganic material and would not
pose a significant oxygen demand if inadvertently discharged to a receiving
water.
In order to provide 24 hours detention time for the effluent from a
lagoon assuming that the volume of effluent is equal to 80 gallons per day per
capita, approximately 21 cubic feet of filter volume would be needed per
person. Construction of an upflow filter of this size would be impractical,
but a plan view of the horizontal filter that is being used in this study is
shown in Figure 15. In this figure, the unit is divided into two parts so
that two separate sizes of rock may be tested; river run gravel between 1/2
to 2 inches, and crushed rock between 2-3 inches. The horizontal flow path
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through this experimental filter will be approximately 28 feet at the 5' water
depth and increase to 58' at the lagoon bottom. The experimental system is
designed hydraulically to provide a range in flow between 3-7 gallons/day/
cubic feet of submerged filter volume.
VALVE
f '"
,!
TOPOFBERMa. 816.3
-V
SAMPLE COLLECTION SITE #1,
H
/
BOTTOM a. 808.3,
5 FT. WIDE
SAMPLING PLATFORM-,
^
INLET STRUCTURE
NOTCH FLOW\
MEASURING WEIRS\
_L I
,/WOODEN DIVIDING
~ WAI I I
WALL
,y>" -2" RIVER RUN
GRAVEL FILTER
SAMPLE COLLECTION SITE H2*a
2" - 3" CRUSHED
ROCK FILTER
WATER LEVEL a. 813.3
0 10 20 30
SCALE IN FEET
MEASUREMENT MANHOLE -\
LT
FIGURE 15. Plan View of Horizontal Slow Rock Filter
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For the convenience of this experiment, the rock filter is being placed
in a separate basin as previously shown in Figure 14. This will aid in measure-
ments and will allow the effluent side of the filter to be tested as a chlori-
nation basin. However, if the system does perform satisfactorily, it is
envisioned that the rock filter will be built as the dike or part of the dike
along one or two sides of the final cell of a lagoon treatment system. If
it is found that over a long period of time the rock filter gradually becomes
plugged, this rock could be removed with equipment available to municipal
maintenance crews, spread on available land, and fresh rock could be added to
create a new filter.
This project was funded in July of 1973. The experimental facilities are
now under construction. The analytical testing of the effectiveness of this
system will continue for the next 16 months.
Land Application of Lagoon Effluents
The past few years have seen a marked increase in the use of sewage or
treated effluent for reclamation of land or irrigation of crops and recreational
facilities such as parks or golf courses. The 1972 Municipal Waste Inventory
lists over 160 lagoons followed by land application. Most of these systems
have been application to land to support cropping operations, and has been
been practiced most extensively in the Southwestern portion of the United States.
In July of 1973 the Environmental Protection Agency's Office of Research
and Development funded a project at Utah State University in Logan, Utah to be
supervised by Dr. E. J. Middlebrooks. The objective of this study is to
conduct extensive investigations on the effectiveness of the land application
of sewage lagoon effluents, and to determine the effects of this effluent on
the crops and soil.
The lagoon waste treatment plant of the City of Logan is quite large; 465
acres which are divided into 7 cells. Cells Al and Bl and A2 and B2 operate
as two series systems in parallel. The remaining three cells operate in
series receiving flow from both of the two parallel systems. The arrangement
of these cells was previously shown in Figure 9. The average daily sewage
flow varies from 6 to 14 mgd depending on water usage and rainfall.
The land application studies will be conducted at the Utah State University
reclamation farm located near the lagoon treatment system. This farm is almost
flat with a slope of 0.077= to the west. The top soil is extremely thin (1-2 feet)
and is composed mainly of a silty clay loam. Below this the soil is a tight
impermeable clay.
The experimental design will consist of eight 50 x 50 foot test plots
irrigated at three different rates (2, 7, and 14 inches/week). The test plots
are shown in Figure 16. The effluent from the lagoon will be pumped approxi-
mately 1/2 mile to the test site and applied through an automated solid set
spray irrigation system. This test plot for each application rate will consist
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2 inches/week
7 inches/week
14 inches/week
Oxidation pond
7 inches/week
oxidation pondl 1
efflue nt algal
cells removed
3
K*J
w
]
V
3
orage crop Soil
treatment treatment
±«
TV 1
1
1
+ 1
K4.
1
1
1
X
Jo o
1 1
A i
T 3
1
1
A i
» *
i--
o 1
50
i
1
i i
f
Jc i
4 :
1
4
-T
i
ft
r
i
, X
[ ₯
i
i -£
" «^ ' -<»
r- - 1 i
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1
1
i 3
i T
t Y
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* *
J X
Drainage System
with algal cells
L-K "" i '
T
50 ft
^_l_
^{ I ,
Sprinklers spaced
30 feet apart on a
2" line
4" perforated drain
36" deep
:=:==*Sample port for drain
pipe to collect return
flow sample
FIGURE 16. Utah State University Effluent
Spreading Test Plots
-25-
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of a forage crop (alfalfa), and a (soil only) treatment plot. They will be
irrigated for six months out of the year for two years. A 4 inch drain pipe
will collect the return flow at a depth of 3 feet and a sample port outside
the plot will allow the collection and analysis of the return flow. It is
anticipated that only the 14 inches per week application rate will saturate
the soil to the point of producing a return flow on a continuous basis.
A slotted two inch coring device will be used to obtain samples from the
various plots on a weekly basis. This will allow analysis of the vertical strati-
fication of the soil and its associated water quality parameters. The upper
most section of the soil mantle will be most actively involved in the removal
of the algal cells. The other water quality parameters, BODc, N-forms, P-forms,
and dissolved organic carbon will be analyzed on a vertical basis to predict
return flow characteristics.
The objective of this work will be to determine the efficiency of algal
cell removal from oxidation lagoon effluents spray irrigated on one type of
vegetation and (soil only) plots. The effluent will be sprayed on the plots
measuring 1) initial algal cell concentrations, BOD, SS, N-forms, and P-forms;
2) continuous measurement of irrigation rates, soil moisture, drainage return
flow, and evaporation rates; 3) analysis of drainage return flow for algal
cells, SS, BOD, N-forms, and P-forms, and 4) measurement of the productivity
of the vegetation types at the three application rates. The storage capacity
of the soil will be determined as a function of algal cell removal and appli-
cation rate. Also, the effect of vegetation on algal cell removal will be
determined, along with the effect of seasons on the amount of algal cell removal
by the various experimental plots. An economic analysis of the system design
will be made based on cost of equipment, operating cost, and any economic
benefit from increased production.
The application of land disposal of lagoon effluents as an upgrading method
is limited by soil and ground water characteristics. However, most lagoons
are constructed in areas where land is available and thus capital investment for
land disposal is relatively low. Furthermore, this method does not create a
sludge disposal problem, has low maintenance and operation cost, and may provide
additional irrigation water in arid regions.
As mentioned earlier, this method has been primarily used in the arid
regions where there is a desperate need for water. However, many other areas
might consider using spray or flood irrigation or ground water recharge simply
as economical means of meeting the Environmental Protection Agency's consistently
increasing effluent standards. These systems must be designed in such a manner
to insure protection of underlying aquifiers as required by the proposed defi-
nition of best practicable treatment.
Intermittent Sand Filtration
Slow sand filtration of drinking water was recorded in the literature as
early as 1828 and an experimental intermittent sand filter was used to give some
improvement in wastewater as early as 1888 in Lawrence, Mass. Little further
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work had been done with this system until after World War II, when there was
a need for some easy inexpensive method to treat settled sewage from trailer
camps and other small facilities in Florida. Work initiated at the University
of Florida originated most of the modern day design and operational data by
studying such factors as temperature, hydraulic loading rates, dosing periods,
sand size, and depth of sand beds. The effects of these variables were monitored
by analyses of BOD, total nitrogen, and suspended solids. Another study was
also undertaken to describe the microbial populations and their influence in
the treatment of settled domestic sewage by intermittent sand filtration.
High rate filtration of lagoon effluents without previous chemical floccu-
lation of the algae has not generally been successful. The type of algae present
in lagoon effluents have fairly flexible bodies and after a period of time work
their way through the filter and appear in the effluent. Dr. Middlebrooks of
Utah State University in conducting laboratory experiments of various waste-
waters through intermittent sand filters found that these filters seemed to
work quite well for lagoon effluents. A series of 4 x 4 foot intermittent
prototype sand filters were installed near the Logan Lagoon Waste Treatment
Plant to study different filter media and loading rates.
The Environmental Protection Agency's Office of Research and Development
has funded an expanded project by Dr. Middlebrooks to construct and operate six
30 x 30 foot intermittent sand filters with a total surface area of 0.1242 acres.
These filters, shown in Figure 17, will be operated in pairs. Each pair of
filters will be operated alternately at a given loading rate for twelve months.
Alternate operation is required to permit resting periods for each filter.
The filters will contain 36 inches of filter media and have a 3 foot free-
board to permit loading rates up to 1 mgd. The filter influent will be distributed
into the filter bed through a system of pipes terminating at the bed surface.
Each outlet will be surrounded by a flat, 2 foot diameter concrete slab to
prevent erosion of the sand surface. Feeding of the distribution system will be
automatically controlled by pumps attached to a timer. The underdrain will be
vitrified clay pipe laid with open joints carefully covered with graded gravel
from 2 inches down to 1/4 inch in size to prevent entrance of sand into the
drain.
The filters will be operated until the headless becomes excessive at which
time the top 1/2 to 2 inches of sand will be scraped off and the solids removed
by washing. The solids or sludge will then be recycled directly to the primary
section of the wastewater lagoon or disposed of by land burial or other sludge
disposal methods. During cold weather periods, the filter surface will be
"plowed up" into ridges and valleys, so that the freezing influent will form a
ridge of ice on top of the furrows to allow subsequent influent to find its
way through the valleys under the ice.
The prototype filters are in operation at the present time. All of the
units have operated a minimum of 60 days without cleaning or scraping. The
effluent from the filters is excellent in quality and normally has a BOD of
5-10 mg/1 and a suspended solids of 4-8 mg/1. Dr. Middlebrooks has stated
-27-
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Wastewater Lagoon Effluent
Q,
J,
\
Loading
Rate
No. 1
Filter
No. 1
'
f
Filter
No. 2
© f' Effluent No. 1 '
*
t
'
Loading
Rate
No. 2
Filter
No. 3
i
f
Filter
No. 4
\ \
/
© f Effluent No. 2
-1
Sand
Washing
Equipment
tD
J,
>
Loading
Rate
No. 3
Filter Filter
No. 5 No. 6
W S \'
© ^Effluent No. 3
Sand Washing Effluent
Legend
Q) Sampling Station
FIGURE 17. Utah State Intermittent Sand Filter Test Plots
that the system of ponding the effluent on the filters each day, allowing it
to slowly sink into and through the filter, and then allowing the surface of
the filters to dry each day is the probable key to the success of this type
of filter. The algae in the effluent form a layer at the top of the liquid
in the freeboard of the filter. This layer is the last part to reach the
sand surface. As it dries, it forms a sort of natural filter much finer than
the sand itself. In fact Dr. Middlebrooks states that the best filtering
does not occur for the first few days until this surface mat becomes well
established. The results from these prototype filters leads him to believe
that a loading rate high enough to treat the entire effluent of a town of
1,000 population may be handled by a pair of 30 x 30 foot filters.
Studies at this scale should identify the best methods of maintaining
and cleaning the filters and provide cost estimates of the operating and
maintenance expenses.and manpower needs for this type of a system.
Other Suggested Methods for Algal Removal
Included in this section are a few methods that have been proposed for
algae and suspended solids removal from lagoon effluents. Some of these methods
have shown moderate success and are still in a process improvement or further
development stage.
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Chemical Addition
Addition of chemicals (alum, lime, or ferric chloride) either
directly into the wastewater feed of conventional or aerated lagoons, or
added by surface spreading on seasonal retention lagoons shortly before
discharge is under investigation. This work is being carried out by the
research branch of the Ontario Ministry of the Environment (10, 11).
Preliminary results show that with aerated lagoons, the resultant floe is
resuspended with very little, if any, improvement in effluent quality. For
conventional facultative lagoons, addition directly to the wastewater feed
only marginally improved the BOD and suspended solids reduction compared to
the control unit without chemical addition. Results on seasonal retention
lagoons have been highly successful with surface spreading of coagulants
from boats and subsequent mixing with the outboard motor to aid flocculation.
Effluent quality after treatment has been less than 10 mg/1 BOD and suspended
solids, 0.4-1.5 mg/1 total phosphorus, and 0.1-0.3 mg/1 of soluble phosphorus.
Best effluent quality is reached within 24-48 hours after treatment with a
gradual deterioration in quality from that time on. The investigators recom-
mended that provision be made for discharge of the treated pond contents
within 8-10 days after treatment. This method may be worth further investi-
gation as a means of permitting intermittent discharge even in southern
climates where algae occur almost year around. The possibility of treating
the contents of an isolated final cell once every 1-3 months and then discharging
the effluent would meet the requirements of not. requiring full time operation.
This approach of course requires that some provision be made to handle the
accelerated accumulation of chemical sludge. It has been suggested that the
final cell be designed at such a depth that the sludge would only have to be
removed once every 10-20 years. Another alternate is for the planned abandon-
ment, and reconstruction of new final cells as required. This approach would
only be feasible where sufficient low cost land is readily available.
Microstrainers
Work is continuing on the development of new synthetic fabrics with
finer meshes and improved methods of backwashing and cleaning the microstrainers
for use in polishing lagoon effluents. Preliminary tests have shown however,
that the costs would be high (10 micron pore size screen and low through rates)
to achieve secondary effluent standards of 30 mg/1 of BOD and suspended solids.
Chlorination-Clarification
It has been suggested that chlorination at a rather high dosage rate
(8-15 mg/1) followed by settling for 20 minutes in a baffled settling tank will
effectively remove algae and suspended solids from lagoon effluents. The
settled material is then removed from the bottom of the sedimentation basin and
disposed of by conventional means. Objections have been made that chlorine
doses high enough to cause the algae to die and settle will cause a significant
release of soluble BOD. For instance, studies by Horn (12) have confirmed that
unless both the chlorine dosage and contact time are rigidly controlled,
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significant BOD will be released to the receiving stream. Little real experi-
mental evidence has been given to demonstrate that the chlorination-clarifi-
cation system will effectively and consistently provide the effluent quality
required by the secondary treatment standards.
Another disadvantage of high level chlorination of lagoon effluents is
its potential toxicity to fish. This is especially important for lagoon
effluents high in ammonia nitrogen that will require higher than normal chlorine
dosages to meet the secondary effluent requirement of 200 fecal coliform/100 ml.
Biological Predators of Algae
It has been suggested that lagoons be seeded with a silver carp,
daphnia or other biological forms to graze on the algae. It may true that these
biological forms can reduce algae populations at times in some lagoons to a
level that might meet the secondary effluent standards. The difficulty with
this method is the lack of reliability and consistency in meeting the new
standards.
There is some interest in a few states to grow fish for sport or
food in sewage lagoons and further research in this field may be justified. A
great deal of additional studies are necessary, however, before this approach
can be considered a viable technique to upgrade lagoon effluent quality to the
desired levels.
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REFERENCES
1. Secondary Treatment Information, FEDERAL REGISTER, Vol. 38, No. 159
Part II pp. 22298-22299, August 17, 1973.
2. Barsom, G., "Lagoon Performance and the State of 'Lagoon Technology,"
Environmental Protection Technology Series, EPA-R-2-73-144
3. Upgrading Lagoons Manual, Prepared for the Technology Transfer Design
Seminar, Brown and Caldwell Consulting Engineers, San Francisco,
California.
4. Neel, J. K., McDermott, J. H., and Monday, C. A. Jr., "Experimental
Lagooning of Raw Sewage at Fayette, Missouri," J. WPCF, 33, 603-641
1961.
5. McKinney, Ross E., Dornbush, James N., and Vennes, John W., "Waste
Treatment Lagoons - State of the Art," Water Pollution Control Research
Series, 17090 EHX 07/71.
6. Penman, A., "Evaluation of Aerated Lagoons in Metropolitan Winnipeg,"
Staff report of the Waterworks and Waste Disposal Division of the
Metropolitan Corporation of Greater Winnipeg, March 1970.
7. Richmond, M. S., "Quality Performance of Waste Stabilization Lagoons
in Michigan," 2nd International Symposium "for Waste Treatment Lagoons,
Kansas City, Missouri, June 23-25, 1970, pp. 54-62.
8. Private Communication, EPA Task Force on Lagoon Design Criteria, Chaired
by Whittington, W., Meetings Held at Kansas City, Missouri, August 16
and September 27.
9. Dryden, F. D., and Stern, G., "Renovated Waste Water Creates Recreational
Lake," Environmental Science and Technology, 2, pp. 268-278.
10. Boyko, B. I., and Rupse, J. W. G., Technical Implementation of Ontario's
Phosphorus Removal Program, Ontario Ministry of the Environment Research
Branch.
11. Elert, N. G., "The Effects of Influent Alum Injection on the Effluent
from Continuous Discharge Lagoons, Publication No. W35, Ontario Ministry
of the Environment Research Branch.
12. Horn, L. W., "Chlorination of Waste Pond Effluents," 2nd International
Symposium for Wastewater Treatment Lagoons, June 23-25, 1970, Kansas
City, Missouri, pp. 151-158.
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