Land Treatment
of Municipal Wastewater
Effluents
Case Histories
625476010
.Technology Transfer Seminar Publication
-------
EPA-625/4-76-010
LAND TREATMENT OF MUNICIPAL
WASTEWATER EFFLUENTS
CASE HISTORIES
ENVIRONMENTAL PROTECTION AGENCY •Technology Transfer
JANUARY 1976
-------
ACKNOWLEDGMENTS
This seminar publication contains materials prepared for the U.S.
Environmental Protection Agency Technology Transfer Program and has
been presented at Technology Transfer design seminars throughout the
United States.
The information in Chapters I-IV was prepared by Frank M. D'ltri,
Ph.D., Michigan State University, East Lansing, Michigan, with assistance
from Thomas P. Smith, P.E., City of Tallahassee, Florida; Herman Bouwer,
Ph.D., U.S. Dept. of Agriculture, Phoenix, Arizona; Earl A. Myers, Ph.D.,
Williams and Works, Thomasville, Pennsylvania; and Allen R. Overman,
Ph.D., Univerisity of Florida, Gainesville, Florida. The information in
Chapter V was prepared by Gordon Gulp, Culp/Wesner/Culp, El Dorado
Hills, California.
NOTICE
The mention of trade names or commercial products in this publication is for
illustration purposes, and does not constitute endorsement or recommendation for use
by the U.S. Environmental Protection Agency.
-------
CONTENTS
Page
Introduction 1
Chapter I. The Michigan State University Water Quality Management Program 3
The WQMP Facility and Its Operation 3
Chemical, Physical, and Biological Monitoring Program 5
Microbiological and Viral Monitoring 10
Scope of Research 12
Crop Management 14
Chapter II. The City of Tallahassee Spray Irrigation Project 19
The Tallahassee Facility and Its Operation 21
Chemical, Physical, and Biological Monitoring 22
Nitrogen Uptake By Selected Grasses 24
Phosphorus Uptake By Selected Grasses 25
Crop Management 27
Chapter III. The Flushing Meadows Project 29
Flushing Meadows Facility and Its Operation 30
Operational System and Economic Aspects 34
Chapter IV. The Pennsylvania State University Wastewater Renovation
and Conservation Project 37
The Pennsylvania State University Facility and Its
Operation 37
Monitoring 40
Scope of the Research 40
Chapter V. The City of Boulder Colorado Project 43
Advance Wastewater Treatment Considerations 43
Land Treatment Considerations 45
Cost Comparison Summary 66
References 77
111
-------
INTRODUCTION
With the advent of the Water Quality Amendments of 1972, which require that all
discharge of pollutants into the nation's waterways cease by 1985, major technological
advances have become necessary. New methods of wastewater treatment must be devised, and
responsible development will hinge on learning much in a short time.
A number of experimental/operational systems have been designed to renovate wastewater
by land application.1 Where sufficient land is available and the hydrological conditions are
favorable, wastewater can be renovated through infiltration basins, ridge and furrow, overland
flow, or sprinkler systems, all of which recharge groundwater and are viable alternatives to
chemical or biological tertiary treatment systems. In a properly managed system, the
wastewater, as it moves through the soil, removes or greatly reduces suspended solids,
biochemical oxygen demand, microorganisms, phosphorus, fluorides, heavy metals, nitrogens,
and many other substances.
This publication presents case histories of five properly managed systems of land
application of municipal wastewater. In terms of purpose, natural conditions, and problems of
implementation, the projects presented have somewhat different histories. The design criteria
and operation of each facility are described, as well as the soil characteristics and the
monitoring schedules used to assess the chemical and biological parameters. The five facilities
considered are:
• The Michigan State University Water Quality Management Project (WQMP)
• The City of Tallahassee Spray Irrigation Project (TSIP)
• The Flushing Meadows Project (FMP)
• The Pennsylvania State University Wastewater Renovation and Conservation Project
(WRCP)
• The City of Boulder Colorado Project (BCP)
Several points differentiate the five facilities. The most significant is that three of them
were designed initially as pilot plants to provide alternative methods of wastewater removal
from currently operating sewage treatment facilities.
The Michigan State University WQMP was designed exclusively as a research and
development project to study alternative aquatic and terrestrial applications of wastewater to
utilize the components as food for plants and animals. Because the facility was created with
research in mind and did not fit into an existing sewage treatment plan, except that the
effluent is pumped from the East Lansing sewage treatment plant after being given secondary
-------
treatment, the land could be studied in its natural state before the project was implemented
and can be charted as time goes on to determine whether changes occur in the groundwater,
soil, or other variables at the site. For this purpose and because the site is experimental, the
quantity of waste can be carefully monitored and controlled.
At Boulder, Colorado, local conditions were such that land treatment showed an
economic advantage. Local conditions have a major effect on applicability and cost. Although
estimated costs for one locale may not be applicable elsewhere, the techniques used to reach
the cost estimates and other conclusions generally apply. The purpose of the BCP presentation
is to describe the factors to be considered in evaluating alternative treatment approaches. The
costs presented are based on July 1974 price levels and are obviously outdated. However, the
elements to be considered in making such estimates are unchanged and are more important in
this context than are the precise values.
Both WQMP and WRCP have seasonal variables that affect their operations, whereas
year-round operation is possible at TSIP and FMP. The latter has no spray irrigation system.
Instead, the water is pumped into infiltration basins, from which it is rapidly absorbed into
the soil.
All three of the pilot plant programs were begun to determine whether land disposal
could provide an alternative for or addition to the conventional sewage treatment systems, and
all are now being expanded to meet the demand of the increasing population. At Tallahassee,
it was decided to apply all of the city's wastewater to the land by sprinkler irrigation as soon
as possible. At Penn State, the expansion plan drawn up in 1968 provided for land
application of all of the wastewater, but budget constraints limited construction to only
three-quarters of the system, which will be operational in the spring of 1976. Phoenix has
recently constructed four 10-acre rapid infiltration basins to renovate approximately 15 mgd
of secondary effluent for unrestricted use by an irrigation district. The design of the project
was based on data from the FMP to plan the hydraulic loadings and anticipated quality of
the renovated water. If this project is also successful, a third and larger rapid infiltration basin
system will be constructed. Although Boulder has two secondary trickling filter treatment
plants with capacity adequate to handle projected 1985 flows., they cannot provide treatment
required to meet pending discharge requirements.
-------
Chapter I
THE MICHIGAN STATE UNIVERSITY
WATER QUALITY MANAGEMENT PROJECT
After the initial concept was developed, financial support and approval to implement the
design were received from the Michigan State University Board of Trustees in December,
1966. In 1968, the 500-acre project site was designated on the south end of the campus.
Shortly thereafter, the Rockefeller, Ford, and Kresge Foundations pledged $1.2 million in
support of the project. During the summer of 1972, funding approval was also received from
the Environmental Protection Agency and the State of Michigan through the Clean Water
Bond Act. Construction began in April, 1973. In September, 1973, the lakes were filled with
wastewater and a number of types of aquatic plants were sown. The Water Quality
Management Project (WQMP) facility was completed in the spring of 1974 and officially
dedicated that October.
THE WQMP FACILITY AND ITS OPERATION
This $2.3 million outdoor laboratory on the Michigan State University campus consists of
four artificial lakes with a total surface area of 40 acres and an average depth of 8 feet. The
site also includes three 1-acre marshes and 320 acres of land, 150 acres of which are equipped
for spray irrigation (see figure 1-1). Municipal wastewater undergoes primary and secondary
treatment at the East Lansing sewage treatment plant before being delivered to the lakes
through 4.5 miles of 21-inch asbestos-concrete pipe. Up to 2 million gallons can be
transported per day. The wastewater undergoes chemical, biological, and physical renovation
over 30 to 60 days while it passes sequentially through the four lakes. The water can then be
released into surface streams or sprayed onto the land.
The prime challenge of wastewater treatment is to concentrate and remove pollutants
from very dilute solutions. The WQMP offers the opportunity to evaluate the potential for
productive waste removal by a number of individual and combined natural aquatic and
terrestrial ecosystems. The great flexibility of this project allows researchers to test various
methods of using fields, forests, marshes, and lakes to produce more food and fiber from
wastewater in a manner that will protect public health. Moreover, the risk of causing new
problems by adding more chemicals for treatment is diminished because most of the treatment
is biological. By themselves, plants and sediments remove substantial quantities of the waste
constituents from the solutions.
For example, one aspect of the project takes advantage of the fact that solar energy
generates photosynthesis in algae and rooted aquatic plants. As these plants grow in the lakes,
they take up the abundant nutrients in the wastewater and alter their chemical composition
to accelerate the physical and chemical removal of the remaining pollutants. They settle to
-------
SECONDARY EFFLUENT FROM EAST LANSING
SEWAGE TREATMENT PLANT 2 M.G.D.
LAKE SYSTEM
186 ACRES INCLUDING
40 ACRES OF LAKES
PUMP
STATION
I-96
TO IRRIGATION
PUMP STATION
FOREST RESEARCH AREA
A IRRIGATION SYSTEM
314 ACRES
Figure 1-1. Michigan State University Water Quality Management Project.
-------
the bottom of the lakes and then are pumped through the irrigation system to the terrestrial
site where the concentrated wastes accelerate plant growth. Both aquatic and terrestrial plants
are to be harvested for animal food or soil conditioners.
CHEMICAL, PHYSICAL, AND BIOLOGICAL MONITORING PROGRAM
The WQMP Laboratory is monitoring over 50 chemical, physical, and biological
parameters as the effluent passes through various stages from the treatment plant through the
lake and irrigation site. These parameters and the sampling timetable are presented in table
1-1. The average concentrations and ranges of selected chemical parameters for the system are
presented in tables 1-2 and 1-3. This analytical program will provide a data base for all
scientists conducting research on the project.
Daily 24-hour composite samples are collected to represent raw, primary, and secondary
effluent at the East Lansing sewage treatment plant. At the site of the WQMP, 24-hour
composite samples are collected from the influent to each lake and the final effluent
concentration from Lake 4. The aquatic plants and sediments are also sampled periodically.
From these data, the percentage of elements for each parameter can be ascertained to
facilitate tracing their translocation into either the sediments or the aquatic plants.
Possible groundwater contamination at both the lakes and spray irrigation sites is
monitored by monthly analyses of well water. Forty-one drift wells, 14 shallow rock wells,
and 4 deep rock wells have been positioned throughout the study area (figure 1-2). All wells
are 4 inches in diameter and have a 3-foot copper screen point and sanitary seals to prevent
bacteriological contamination. The drift wells, the shallowest of the three, are positioned in
the glacial drift between 40 and 60 feet deep. Samples are obtained by pressurizing the drift
wells and forcing the water through a plastic pipe which extends to the bottom of the well.
Both shallow and deep rock wells extend into the aquifer which provides the water supply for
the university. The shallow rock wells are approximately 85 feet deep on the average, and the
deep rock wells average about 180 feet. All are equipped with submersible pumps for
sampling. Guarding against contamination, particularly from potential sources of viruses, was
the most severe constraint in planning the sampling program from these wells. Comparing
post-operational data with background levels should detect contamination from the lake or
spray irrigation water.
A little surface runoff in the study area is channeled into Felton Drain. Although it now
flows only in the spring and summer, this will probably increase significantly when spray
irrigation begins. Therefore, monthly samples will also be analyzed to determine the chemical
characteristics of this water. Effluent from Lake 4 can be discharged from an experimental
stream into the Red Cedar River via Herron Creek. At present this creek, like Felton Drain,
has an intermittant flow, but operational flow levels will also be monitored. After the effluent
has been sprayed on the irrigation site, analyses will be conducted of water collected in soil
suction infiltrometers and plant tissue. These data will indicate how much of the remaining
nutrients is absorbed by the soil and terrestrial systems after the water has gone through the
lake system.
A data management system is being implemented to handle the large volume of data that
are generated. This system is designed to:
• Store, retrieve, prepare, manipulate, and display all data
-------
Table 1-1.—The Michigan State University Water Quality
Management Project monitoring program experimental analyses design
Chemical, biological,
or physical
parameter
1. Temperature
2. pH
3. Dissolved oxygen
4. Specific conductance
5. Turbidity
6. Light penetration
7. Redox potential
8. Ammonia
9. Nitrate
10. Nitrite
11. Kjeldahl nitrogen
12. Ortho phosphate
13. Total inorganic phosphorus
14. Total phosphorus
15. Chloride
16. COD
17. Silicon
18. Hardness
19. Cyanide
20. Sulfide
21. Alkalinity
22. Phenol
23. Dichromate
24. Fluoride
25. Sulfate
26. Boron
27. Total carbon
28. Total filterable carbon
29. Filterable organic carbon
30. Total organic carbon
31. BOD5
32. Suspended solids
33. Settleable solids
34. Dissolved solids
35. Hexane extractables
36. Aluminum
37. Arsenic
38. Cadmium
39. Calcium
40. Chromium
41. Cobalt
42. Copper
Sampling frequency
STP
CONT
CONT
CONT
CONT
CONT
CONT
CONT
D24C
D24C
D24C
D24C
D24C
D24C
D24C
D24C
D24C
W168C
D24C
W168C
W168C
D24C
W168C
W168C
W168C
W168C
D24C
D24C
D24C
D24C
D24C
D24C
D24C
D24C
D24C
D24C
W168C
W168C
W168C
W168C
W168C
W168C
W168C
Lake
water
CONT
CONT
CONT
CONT
CONT
CONT
CONT
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
W168C
2D12C
W168C
W168C
D24C
W168C
W168C
W168C
W168C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
2D12C
W168C
W168C
W168C
W168C
W168C
W168C
W168C
Lake
sediments
4Y
4Y
NSR
4Y
NSR
NSR
4Y
4Y
4Y
4Y
4Y
4Y
4Y
4Y
4Y
4Y
NSR
NSR
NSR
4Y
NSR
NSR
NSR
NSR
4Y
4Y
4Y
NSR
NSR
4Y
4Y
NSR
NSR
NSR
4Y
4YDC
4YDC
4YDC
4YDC
4YDC
4YDC
4YDC
Campus
and
test
wells
MIS
MIS
MIS
MIS
MIS
NSR
MIS
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
MG
Felton
and
Herron
Creek
MIS
MIS
MIS
MIS
MIS
NSR
MIS
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
Soil
samples
2Y
2Y
NSR
NSR
NSR
NSR
2Y
2Y
2Y
2Y
2Y
NSR
NSR
2Y
2Y
2Y
NSR
NSR
NSR
NSR
NSR
NSR
NSR
2Y
2Y
2Y
2Y
NSR
NSR
2Y
NSR
NSR
NSR
NSR
2Y
2Y
2Y
2Y
2Y
2Y
2Y
2Y
Analyses
per
year
1032
1032
828
924
828
-0-
1032
5777
5777
5777
5777
5669
5669
5777
5777
5777
1244
5573
1244
1340
2748
1244
1244
1352
1448
5777
5777
5573
5573
5777
5669
5573
5573
5573
5777
1400
1400
1400
1400
1400
1400
1400
-------
Table \A.—The Michigan State University Water Quality
Management Project monitoring program experimental analyses design (Continued)
Chemical, biological,
or physical
parameter
43. Iron
44. Lead
45. Magnesium
46. Manganese
47. Mercury
48. Nickel
49. Potassium
50. Sodium
51. Residual chlorine
Sampling frequency
STP
W168C
W168C
W168C
W168C
W168C
W168C
W168C
W168C
D24C
Lake
water
W168C
W168C
W168C
W168C
W168C
W168C
W168C
W168C
SAR
Lake
sediments
4YDC
4YDC
4YDC
4YDC
4YDC
4YDC
4YDC
4YDC
NSR
Campus
and
test
wells
MG
MG
MG
MG
MG
MG
MG
MG
NSR
Felton
and
Herron
Creek
M168C
M168C
M168C
M168C
M168C
M168C
M168C
M168C
SAR
Soil
samples
2Y
2Y
2Y
2Y
2Y
2Y
2Y
2Y
NSR
Analyses
per
year
1400
1400
1400
1400
1400
1400
1400
1400
365
KEY
Type of Sampling
c
G
DC
= Composite
= Grab
= Core sampling
SAR
NSR
IS
= Sample as required
= No sample required
= In situ analysis
Frequency of Sampling
CONT = Continuous
H - Hourly
D = Daily
W
M
Y
Weekly
Monthly
Yearly
Integers preceding the frequency code letter designate the numbers of samples taken within that period.
Integer preceding the letter C indicates that the number of hours of the sample is composited
-------
Table 1-2.—Average concentrations (ppm) and ranges
(within parentheses) or selected chemical parameters in East
Lansing wastewater during the period of October, 1973 - March, 1975
Chemical parameter
Total phosphorus
mg/l-P
Soluble phosphorus
mg/l-P
Ammonia nitrogen
mg/l-N
Nitrate nitrogen
mg/l-N
Nitrate nitrogen
mg/l-N
Kjeldahl nitrogen
mg/l-N
Total carbon
mg/l-C
Total organic carbon
mg/l-C
Boron
mg/l-B
Calcium
mg/l-Ca
Sodium
mg/l-Na
Magnesium
mg/l-Mg
Manganese
mg/l-Mn
Raw
7.0
(3.6-9.5)
3.0
(2.7-5.7)
9.3
(4.1-32)
0.005
«0.005-0.03)
0.54
(0.16-3.1)
25.3
(4.4-38)
183
(67-202)
73
(43-105)
0.33
(0.49-0.19)
108
(95-125)
103
(58-295)
25
(20-29)
0.16
(0.10-0.39)
Primary
5.0
(2.6-10.5)
1.1
(2.1-3.8)
16
(8.6-25)
0.25
KO.005-0.13)
0.2
(0.09-2.33)
26.3
(18.7-45)
171
(55-215)
50
(38-97)
0.31
(0.35-0.29)
110
(85-125)
110
(59-295)
26
(20-30)
—
Secondary
2.6
(0.5-9.1)
1.1
(0.3-7.9)
9.7
(5.2-22)
0.25
(0.07-0.90)
1.07
(0.16-7.0)
12.7
(8.5-28)
120
(60-227)
30
(12-111)
0.33
(0.42-0.21)
113
(90-129)
119
(63-300)
24
(20-28)
0.09
(0.03-0.18)
-------
Table \-3.-Average concentrations
(ppm) and ranges (within parentheses) of selected chemical
parameters in the WQMP lake system during the period of October, 1973 - March, 1975
Chemical parameter
Total phosphorus
mg/l-P
Soluble phosphorus
mg/l-P
Ammonia nitrogen
mg/l-N
Nitrite nitrogen
mg/l-N
Nitrate nitrogen
mg/l-N
Kjeldahl nitrogen
mg/l-N
Total carbon
mg/l-C
Total organic carbon
mg/l-C
Boron
mg/l-B
Calcium
mg/l-Ca
Sodium
mg/l-Na
Magnesium
mg/l-Mg
Manganese
mg/l-Mn
Lake 1
1.91
(0.86-3.23)
1.49
(0.55-2.66)
4.87
(0.36-9.7)
0.15
(0.006-0.33)
1.64
(0.06-12.3)
9.75
(1.16-21)
55
(27-80)
14
(6-48)
0.33
(0.41-0.26)
49
(39-71)
82
(68-111)
20
(14-32)
0.05
KO.05-0.10)
Lake 2
1.34
(0.57-2.62)
1.24
(0.57-2.62)
4.91
(0.26-10.6)
0.09
(0.03-0.18)
1.64
(0.06-10.9)
9.45
(3.30-15)
47
(24-69)
8.6
(0-11)
0.25
(0.30-0.20)
46
(30-70)
79
(49-108)
19
(13-32)
0.05
«0.05-0.09)
Lake 3
1.37
(0.55-3.35)
1.06
(0.51-2.32)
3.77
(0.27-8.1)
0.16
(0.02-0.15)
1.02
(0.10-1.72)
8.53
(4.50-15)
43
(24-60)
g
(4-13)
0.25
(0.31-0.23)
45
(34-68)
78
(60-108)
19
(14-32)
<0.05
«0.03<0.05)
Lake 4
0.54
(0.22-1.27)
0.34
(0.12-0.80)
3.36
(0.10-8.3)
0.06
(0.20-0.09)
0.77
(0.10-1.25)
5.73
(2.0-14)
31
(10-46)
7
(3-20)
0.25
(0.29-0.19)
33
(15-51)
59
(16-79)
12
(4-20)
<0.05
«0.03<0.05)
-------
DRIFT WELL MONITORS
SCREENED IN FIRST WATERBEARING
SAND OR GRAVEL LEWS, WITHIN 5 FT
OF WATER SURFACE
SHALLOW ROCK-WELL MONITORS
PENETRATING 25 FT INTO ROCK
WHICH MUST BE MAINLY SANDSTONE
CASED AND SEALED THROUGH DRIFT
DEEP ROCK-WELL MONITORS
ABOUT 200 FT IN DEPTH CASED
AND SEALED THROUGH THE DRIFT
Figure I-2. WQMP study area.
• Transfer data from the producer to all authorized users
• Prevent its loss, destruction, or unauthorized use
The data are stored in the Michigan State University CDC 6500 computer under the
mnemonics and code acquisition numbering of the STORET data management system
whenever it can be used.
MICROBIOLOGICAL AND VIRAL MONITORING
Microbiological and Viral Studies2
At the East Lansing plant, the wastewater treatment does not remove all of the
pathogens from the sewage, especially the viruses which are difficult to destroy even by
chlorinating the treated water. Forty percent of the samples still contained viruses after the
effluent was chlorinated at the East Lansing plant. They remained in water that was
discharged into the Red Cedar River just downstream from the Kalamazoo Street bridge.
10
-------
Viruses also remained in 44 percent of the samples of river water taken as far as 500 feet
downstream from the chlorinated effluent. The samples ran as high as 70 percent when the
effluent was not chlorinated.3
The WQMP microbiological and viral research program is designed to find methods of
preventing public health hazards when municipal wastewater is eliminated and/or reused. The
primary objectives of the program are to:
• Measure the pathogens, bacteria, and viruses in the East Lansing wastewater, in the
WQMP lakes, and on the land after spray irrigation.
• Determine the rate and efficiency of removing these pathogens during processing by
the East Lansing wastewater treatment plant and as the water passes through the
WQMP wastewater renovation system.
• Monitor the water from the wells drilled around the WQMP lakes to detect
contamination of the aquifer.
• Monitor the purity of the University's water supply.
Analyses for viruses will be accomplished with methods that have been used at the East
Lansing wastewater plant for many years to isolate pathogenic Salmonella and Shigella*
Studies at the original5 and present water treatment plant have authenticated the value of one
method for isolating viruses in wastewater.6 Pad samplers, 4-inch squares of absorbent cotton,
are placed between two layers of cheesecloth and are held in place by sewing the three layers
together. They will be used on all flowing water to trap bacteria and virus particles. After the
pad accumulates and concentrates the bacteria and viruses, they can be isolated with standard
methods.7 Careful concentration and strict culture procedures are required to isolate the
complex viruses. The fluid in the pad is expressed and approximately 100 ml is concentrated
by ultracentrifugation. The resulting "sediment" is then suspended in approximately 3 ml of
the supernatant fluid in about a 1:95 volume concentration. After the bacteria are eliminated
with antibiotics, the sample is centrifuged at slow speeds. If the bacterial sterility controls are
then negative, the sample is introduced on cultures of African green monkey kidney cells. The
isolated viruses are subsequently passed into secondary cultures to be identified by serological
methods if that is necessary.
Water samples from the monitoring wells are collected in gallon volumes and are passed
through the continuous flow ultracentrifuge to remove the viruses. Specific polyethylene
imines are added to the water sample to enhance survival of the infective virus particles. After
concentration, the samples are tested for sterility and introduced into the cell cultures as
previously described. If samples of water from the monitoring wells contain viruses, the
quantity will be determined by plaque counting. These methods are routinely used in this
laboratory for the isolation of viruses from sewage and water.3'5
More enteric bacteria and viruses are in wastewater in the late summer and early fall.4
Therefore, more water samples are collected during these periods. Pad samples will be taken at
various stages of treatment in the East Lansing wastewater plant as well as from the inflow
and outflow of the WQMP lakes to compare the recovery of pathogens. In both systems,
more effort will be exerted to recover and analyze viruses than the pathogenic bacteria which
are more readily destroyed.
While water samples from all the monitoring wells will be tested for bacteria and viruses,
those wells located close to the WQMP lakes will be tested the most frequently. By recovering
11
-------
the coliform organisms, bacterial slippage through the soil will be detected. If this occurs,
repeated tests will be initiated to determine the amount of slippage and the radial spread of
the viruses.
Aerosol samples will be collected for bacterial studies with such sampling devices as the
Anderson sampler,8 silt sampler,9 all glass impinger,1 ° and syringe sample. Since no
satisfactory method is now available to sample enteric viruses in aerosols, it will be necessary
to develop methods at the spray irrigation site. Exposing live animals to the aerosol is
probably the only solution at this time. Studying the animals' immunity response before and
after exposure will give evidence of infection from enteric viruses in the aerosol, as exposing
the animals at various times and distances from the aerosol jets will determine the relative
hazards, if any.
SCOPE OF RESEARCH
The project site on the Michigan State University campus was designed to encourage
maximum cooperative research by scientists from such diverse areas as limnology, botany, crop
and soil sciences, economics, engineering, entomology, fisheries, forestry, horticulture,
hydrology, geology, sociology, zoology, and chemistry.
The research can characterize the dynamics of wastewater constituents in an integrated
system of wastewater treatment and nutrient recycling. First, the magnitude and direction of
the biotic and abiotic factors are being identified to determine how they affect the movement
of phosphorus, nitrogen, and carbon in aquatic and terrestrial systems. The movement of these
nutrients, especially phosphorus, is being monitored through several significant subunits of the
WQMP.
The Aquatic System
In the aquatic system, the nutrients and other pollutants are being stripped from the
water by various chemical, biological, and physical methods.
• Some of them are adsorbed onto particulates which are sedimented or directly
adsorbed onto bottom sediments.
• Some wastes are removed by direct chemical precipitation whenever photosynthesis
by algae and plants causes the pH of the system to increase.
• Some of these materials are taken up by photoplankton and algae which die and
transport them to the sediments. A unique feature of the aquatic system is the
marsh area located between Lakes 2 and 3. This was included to investigate how a
marsh ecosystem removes nutrients, especially through denitrification.
• Some nutrients have a secondary uptake into aquatic animals such as zooplankton,
insects, crayfish, tadpoles, minnows, and fish.
12
-------
Aquatic macrophytes also remove nutrients as they grow. This, in turn, provides vast
adsorptive surfaces which also remove these pollutants. To take advantage of these
removal mechanisms, the following 10 species of aquatic macrophytes were
transplanted into the lake system: Potamogeton foliosus, P. pectinatus, P. crispus,
Elodea canadensis, E. nuttallii, Myriophyllum spicatum, Najas flexilis, Ranunculus
sp., and Vallisneria americana. Preliminary studies of these macrophytes indicate that
ash-free dry weight net yields of approximately 2.1 kg/m2 can be expected over a
6-month growing season. The phosphorus and nitrogen content of the harvested
plants are typically about 1.5 and 5 percent, respectively.11
The Terrestrial System
Research on the terrestrial system involves delinating the short- and long-term effects of
wastewater effluent on soil hydrology, texture, and composition. In conjunction with these
research programs, the survival and growth of various types of trees, weeds, and cultivated
crops are also being investigated.
Hydrologic Studies
1 2
Studies are underway at the terrestrial site to explain the hydrological response as the
watershed receives spray irrigation with treated municipal wastewater. Inasmuch as major
producing wells are situated nearby, the groundwater flow beneath the WQMP must be
carefully monitored to assess the impact of the spray irrigation and lake operations on the
aquifer system. A comprehensive groundwater study has been underway for over 2 years with
the ultimate objective of being able to predict and monitor the dispersive nature of water
with varying degrees of quality in the flow regions of the aquifer.
A digital computer program has also been developed and implemented to make use of
triangular finite elements.13 With the Galerkin method, the space variables can be
distinguished in the basic unsteady flow equation. Coupled with a central difference time step
formulation, this can solve the resulting systems of algebraic equations. The computer model
is designed to handle a variety of regional situations, including steady or unsteady and
confined or unconfmed flows. Finite element methods have definite advantages to model
complex boundaries and variable inputs such as recharge, pumping, and field properties.
Numerical solutions for single-well systems can be compared with known analytical results to
show some of the limitations of the model. Applications to field situations emphasize flow
analyses at the WQMP site. A 6-year simulation of the hydrodynamic response of the aquifer
is also being compiled with historical pumping data.
In another aspect of this project, flows are being analyzed in the glacial drift overlying
the aquifer. Once these flows have been traced more accurately, the percolation of recharged
water downward into the main aquifer can be estimated and its response studied. In addition,
the unsteady flow model will be coupled with the convective-dispersion equations to predict
water quality in the aquifer. In the future, isoparametric elements in the flow model will be
used to ease data input manipulation and reduce the required computer storage. At the same
time, the available numerical techniques will be reviewed to solve the convective dispersion
equations and determine which ones are best suited for the present system. Then
13
-------
comprehensive analyses of surface hydrology and runoff will be combined with subsurface
flow at the spray irrigation site to explain the total movements of irrigation water.
The piezometric surface and water table conditions at the site are now being monitored
so that future flow predictions can be correlated with field data. Six automatic water-level
recorders were installed on selected test wells for continuous monitoring. At specified time
intervals, water levels in all of the test wells are manually recorded by means of drop lines.
Well borings have been analyzed and the coordinates of all the test wells in the system have
been determined.
Another hydrologic study is underway to assess the feasibility and potential of a winter
spray operation. The first overall objective is to study the hydrologic balance of both natural
and wastewater added to the subwatershed for the winter months. Continuing investigations
will monitor the same parameters for an entire water year to determine water quality for
both surface runoff and infiltration.
The 10-acre subwatershed is located in the southwest portion of the spray region and
drains into Felton Creek. Normal drainage is probably through the subsurface with some
runoff directly into the stream during both periods. Approximately 4 inches of wastewater is
applied to the area per week on an intermittant schedule that started in January, 1975. This
research project should determine the impact of ice accumulation, infiltration characteristics
beneath the spray area, runoff response, and the fate of nutrients in the runoff and infiltrated
water. The integrated data computed from these hydrologic studies will provide integrated
data on the water quantity and quality balance at the spray irrigation site.
CROP MANAGEMENT14
The objectives of this research program are as follows:
• To compare annual crops with perennial forage crops that produce the high yields
needed to feed livestock over several years without having to be reestablished. When
the crops are irrigated with high levels of sewage effluent, they can be harvested
under varying time frequencies to obtain the maximum biomass per acre.
• To determine how soils and plants fix minerals and the fate of heavy metals when
wastewater effluent is applied on perennial forage crops and annual crops.
• To estimate the in vitro digestibility as an indicator of in vivo digestibility to secure
maximum biomass and adsorption of nutrients.
The field plots were established on 2 acres and irrigated from early May to late
November with 1, 2, and 3 inches of wastewater effluent each week. Table 1-4 gives the
estimated soil loading per acre with an application of 1 inch of secondary effluent from the
East Lansing plant. The soil was categorized in October, 1973, as a uniform Miami loam by
taking 45 samples in 1-foot increments to a depth of 10 feet.
The eight perennial legumes and eight perennial grasses were established in August, 1973,
by seeding with a precision planter. In one area, rye was sown in early September to serve as
a winter cover crop. The annual crops—two varities of hybrid corn, one forage sorghum, and
14
-------
Table 1-4.—Estimated soil loadings per acre on application
of 1 inch of East Lansing sewage treatment plant secondary effluent
Chemical parameter
Organic nitrogen
Nitrate nitrogen
Nitrite nitrogen
Ammonia nitrogen
Soluble phosphorus
Total phosphorus
Total carbon
Total organic carbon
Dissolved organic carbon
Suspended solids
Volatile solids
Chlorides
lronb
Manganese
Zinc
Nickel
Copper
Mercury
Concentration in
secondary effluent
(mg/l)
2.2
3.07
0.25
9.70
1.1
4.9
150
30
20
63
25
261
0.81
0.09
0.19
0.11
0.06
0.00005
Grams per
acre
inch
227
317
26
1,261
143
637
15,450
3,090
2,060
6,489
2,575
26,883
83
9
20
11
6
0.005
Pounds per
acre
inch
0.5
0.7
0.06
2.77
0.3
1.4
34
6.8
4.5
14.3
5.7
59.1
0.18
0.02
0.04
0.025
0.013
0.00001
Pounds per
acre
per year3
36
50
4.1
200
23
101
2,445
489
326
1,027
408
4,254
13.2
1.5
3.1
1.8
1.0
0.0008
aAt a rate of 2 inches per week between March and November (36 weeks).
blron is being added for chemical phosphorus removal at the East Lansing sewage treatment plant.
one sorghum sudangrass—were established in mid-May with a no-till planter after the rye was
treated with Paraquat herbicide to kill the top growth (see table 1-5).
Because of technical problems, the wastewater effluent was not available until July 16,
1973. Then effluent spray levels of 1, 2, and 3 inches per week were started and continued
for 14 weeks until October 21, when the final plots were harvested and the soil was sampled.
The unfilled soil absorbed the effluent rapidly. One inch was absorbed in an hour without
any runoff, even on plots that received 3 inches per week in three applications of 1 inch each
on Monday, Wednesday, and Friday.
Yields of the first annual grass crop and three harvests of perennial grasses were lower
than expected, probably because in the 14-week irrigation period, only approximately 27, 54,
and 91 pounds of nitrogen were applied per acre at the 1-, 2-, and 3-inch levels of effluent,
respectively. At least 150 pounds of nitrogen per acre are necessary for a good yield of
perennial grasses and annual grass crops such as corn. Even at the high rate of effluent spray
with 91 pounds of nitrogen per acre, annual and perennial grasses were deficient by about 60
pounds per acre. However, the legumes yielded well and showed no symptoms of mineral or
nitrogen deficiency. Apparently the legumes obtained enough nitrogen symbiotically from the
15
-------
Table \-5.-Plants irrigated with municipal wastewater effluent for
forage crop production (planted August 1973, harvested 1974)
Perennials
Grasses
Smooth bromegrass (Bromus inermis Leyss) cultivar Sac (southern)
Smooth bromegrass (Bromus inermis Leyss) Canadian source (northern)
Orchardgrass (Dactylis glomerata L.) cultivar Nordstern
Tall fescue (Festuca arundinacea Schred.) cultivar Ky. 31
Timothy (Phleum pratense Leyss) cultivar Verdant
Kentucky bluegrasss (Poa pratensis Leyss) cultivar Park
Creeping foxtail (Alopecurus arundinaceus Poir) cultivar Garrison
Reed canarygrass (Phalaris arundinacea L.) Commercial
Legumes
Alfalfa (Medicago sativa L.) cultivar Saranac
Alfalfa (Medicago sativa L.) cultivar Agate (Phytophthora resistant)
Alfalfa (Medicago sativa L.) cultivar Vernal
Alfalfa (Medicago sativa L.) cultivar 520
Alfalfa (Medicago sativa L.) cultivar Iroquois
Alfalfa (Medicago sativa L.) cultivar Ramsey
Birdsfoot trefoil (Lotus corniculatus L.) cultivar Viking
Birdsfoot trefoil (Lotus corniculatus L.) cultivar Carrol
Red clover (Trifolium pratense) cultivar Arlington
Annuals
(planted each spring starting 1974, harvested the same year)
Corn (Zea mays L.) cultivar Funk G-4444
Corn (Zea mays L.) cultivar Mich. 560-3X
Sudangrass (Sorghum sudanense P. Stapf) cultivar Piper
Sorghum-sudangrass hybrid (Sorghum bicolor L. Moench x S. sudanense P. Stapf)
cultivar Pioneer 908
Forage sorghum (Sorghum bicolor L. Moench) cultivar Pioneer 931
air to meet the requirement of around 200 pounds per acre, because the effluent was
deficient in applied nitrogen.
The soil was sampled in 45 locations in 1-foot increments to a depth of 10 feet for soil
profile data on pH, conductivity, extractable P, K, Ca, Mg, Na, Cl, NO3, N, Ca, Cd, Co, Cu,
Fe, Mn, Ni, Pb, and Zn, plus Kjeldahl N and total C. Samples of plants were analyzed for
these elements with micro-Kjeldahl, emission spectrographic, atomic absorption, ion electrode,
and colorimetric analyses. Certain elements, such as Cl, Cd, Co, Ni, and Pb, are determined in
plant tissues only if spot checks show them to be a potential problem. Samples were collected
in the fall of 1973 for baseline data and in 1974 after 1 year of cropping. The first year's
samples have been analyzed, and the 1974 samples are being analyzed now. Plant samples
16
-------
have been ground up and are being analyzed for nitrogen and minerals and for in vitro
digestibility.
In 1975, the same annual crops are again being planted. Soybeans have been added
because the other legumes performed so well in 1974. The first effluent was applied in
mid-April to be continued for 26 weeks. Approximately 70, 140, and 210 pounds of nitrogen
are being added per acre at 1-, 2-, and 3-inch levels in 1975. This should generate differential
yields of the annual and perennial grass crops.
In addition to research into design and management criteria for the successful operation
of this type of wastewater treatment, the WQMP has inspired a multitude of innovative
ancillary research projects. Those factors which interact to control aquatic fertility will be
evaluated as well as hydroponics and high-rate fish culture. The terrestrial research will
enhance food and fiber production through the use of wastewater while basic land resources
are protected and improved. Another research area is the economic and social evaluation of
this form of waste recycling adjacent to a large urban population. For this, the maximum
public recreation potential of the WQMP will be assessed.
17
-------
Chapter II
THE CITY OF TALLAHASSEE
SPRAY IRRIGATION PROJECT
Tallahassee's two treatment plants, the Lake Bradford Plant (4.5 mgd) and the Dale
Mabry Plant (0.5 mgd), were placed in operation during the 1940's. Their effluent was
discharged to a natural drainage stream which flows into Lake Munson. Since this stream also
receives most of the storm runoff water from the city, it has become heavily laden with silt
during the past 30 years and shows the typical signs of accelerating eutrophication. Because
no rivers flow through Tallahassee, a city located 16 miles from the coast, Lake Munson is
the only receiving water within Tallahassee's major drainage basin. Therefore, it will continue
to receive runoff water and any treated wastewater which is discharged to a surface stream
(figure II-1).
In 1961, the city began operating a 60,000-gpd high-rate trickling filter plant to serve the
municipal airport. Over a 6-month period during 1961-1962, field experiments at this plant
demonstrated that the effluent could be satisfactorily disposed of on land by irrigating at the
rate of 4 inches per day over 8 hours.
When Tallahassee's two plants reached their planned capacity in 1965, the new southwest
wastewater treatment plant was constructed near the airport where soil and groundwater
conditions were similar to the experimental irrigation plot. The high-rate trickling filter plant
has a comminuter, degritter, primary clarifier, trickling filter, final clarifier, chlorine contact
tank, holding pond, a wastewater irrigation field, and a surface outlet to Lake Munson.
Florida state law requires that treated effluent be chlorinated before it is released into
receiving waters or applied to the land by spray irrigation. Because local citizens have
continued to complain about the appearance of Lake Munson, the city is in the process of
developing an alternative 850-acre effluent disposal site 1.5 miles north of the lake, where
land irrigation of the entire combined flow of 11 mgd has been shown to be feasible. The
Bureau of Sanitary Engineering, Florida State Board of Health, permitted one mgd effluent
spray irrigation system in lieu of the surface outlet. If this irrigation system proves
satisfactory, permission for additional irrigation capacity is to be granted. The system has been
operating continuously since the initial flow of 0.25 mgd began in the summer of 1966. Daily
flows were gradually increased to 1 mgd by the summer of 1969. Plant effluent BOD and
suspended solids averaged 15 to 20 ppm during this period.
Plans called for the effluent to flow through the holding pond and be applied to the
irrigation fields on an "as needed" basis to control the pond water level. After 6 months
operation, less than one-third of the holding pond bottom had become wetted, so none of the
effluent was available for irrigation. The pond was then bypassed, and during the spring of
1967, the plant effluent was applied directly to the irrigation plots.
In 1972, the Environmental Protection Agency funded a 3-year study to be conducted
by Dr. A. R. Overman of the Department of Agricultural Engineering at the University of
19
-------
DALE MABRY
TREATMENT PLANT
0.5 MGD
\
LAKE BRADFORD
TREATMENT
PLANT
4.5 MGD
850 ACRE
SPRAY
IRRIGATION
SITE \
0 0.5 1.0
O MONITORING WELLS
AIRPORT
TREATMENT
PLANT
0.06 MGD
fc-l - \ ^
y/ A CAPITOL CIRCLE SOU
I •••••••••••••••
TALLAHASSEE
MUNICIPAL AIRPORT
APALACHICOLA
NATIONAL
FOREST
SOUTHWEST
TREATMENT PLANT AND
SPRAY IRRIGATION SITE
6.5 MGD
Figure 11-1. Tallahassee Spray Irrigation Project.
20
-------
Florida. Various crop responses are being determined as a function of the wastewater loading
and the groundwater quality is being monitored. This research will provide design and
operational criteria for other Florida municipalities as well as Tallahassee.
THE TALLAHASSEE FACILITY AND ITS OPERATION
Site Selection
The treatment plant is located on land which was once part of the Apalachicola National
Forest. Geologically, it is part of Lake Munson Hills, a 40-square-mile area at the western
edge of the Woodville Karst Plain. The 200-acre plant site is 50 to 70 feet above mean sea
level, and the normal static water level is 40 feet below ground surface.
The soil is mostly lakeland fine quartz sand with a depth to water table and limestone
aquifer of approximately 50 feet. This soil typically has an infiltration capacity of 3 to 4
inches per hour. Usually it has 1- to 2-percent organic matter and less than 5-percent clay.
The low natural fertility of the soil is reflected in the native vegetation. Besides scrub oak
and similar plants, slash pine grow rather slowly in the area. Furthermore, the soil has a poor
moisture-holding capacity with an available water content of about 1 inch per foot of soil.
The extensive citrus farming in central Florida demonstrates that these soils can be very
productive with proper fertilization and irrigation. Their deep rooting zone and high
permeability are conducive to intense production.
Sieve analyses on samples collected 1 foot below ground surface show an average
effective size of 0.15 mm and a uniformity coefficient of 2.3. These characteristics provide an
almost unlimited hydraulic absorption capacity, ensuring that flooding and the attendant
runoff will not be a problem.
Soil samples collected as drilling cores throughout the 200-acre site show a general
pattern of 20 to 25 feet of yellow quartz sand below the surface. Under that is a clay lens
varying in thickness from a few feet to more than 10 feet, followed by 10 to 12 feet of
white quartz sand and then limerock.
Pumping Station and Irrigation Field Layout
The pumping station that supplies the irrigation field is located near the chlorine contact
chamber. It was designed to pump effluent into the wet pit from either the contact chamber
or the holding pond. When the flow from the contact chamber exceeded the pump capacity,
the excess spilled into the holding pond. The centrifugal pump was designed for an output of
720 gpm at 160 feet of total head driven by a 50-hp, 3-phase motor. An inline meter
measures how much effluent has been pumped and automatically shuts it off at a
predetermined number of gallons.
The irrigation pipe system is composed of 6- to 8-inch aluminum main lines and 2-inch
aluminum lateral lines. The sprinklers are spaced on 100-foot centers, and each one delivers
21
-------
45 gpm at an application rate of 0.45 inches per hour. The system was designed to operate at
between 55 and 60 psi at the sprinkler head. The piping system is valved so that 16
sprinklers can be operated at one time to apply effluent at the rate of approximately 1 mgd
to 4 acres. Altogether, 16 acres are under irrigation in four 4-acre tracts. One or a
combination of the four plots can be sprinkled at any time. It was soon established that all
16 acres did not have to be irrigated simultaneously. Only 8 acres were necessary for the
1-mgd flow except to observe how the grass responded to municipal wastewater irrigation. To
determine which grasses responded best, the four plots were seeded with Pensacola Bahia,
Argentina Bahia, Centipede, and mixed wild grasses.
In the spring of 1971, a bypass line was completed from the Lake Bradford Plant to
carry the overload to the Southwest Plant. A gun-type sprinkler was then installed and
positioned to irrigate both undisturbed forest land and a plowed field. After 7 continuous
days of irrigation at the rate of 250,000 gallons per acre per day, the forest land showed no
signs of ponding. However, the plowed ground started ponding after the 2nd day. Therefore,
four big sprinkler guns were installed on 400-foot centers in a rectangular plot to irrigate the
forest land. Each gun delivers 1,060 gpm in a 555-foot circle. They are operated in pairs and
alternated every other day. Each pair of sprinklers applies 2 million gallons daily. Neither the
spray operation nor the residual field emit much odor. Nor have there been any signs of
solids building up on the irrigation field surfaces.
Design Factors
At Tallahassee, the design of this spray irrigation field has demonstrated the reliability of
both the equipment to move the effluent and the irrigation field to accept it without ponding
or runoff. Under the initial experimental design, the aluminum farm irrigation pipe was laid
on the surface so that it could be rerouted with a minimum of effort if the system failed.
The aluminum pipe has proven to be unsatisfactory; the exposed lines have been bent,
broken, or corroded by external mechanical damage and internal wear from abrasion.
Therefore, underground cast iron pipe will be used when the irrigation field is expanded.
Alternate pumps are being installed to eliminate downtime for pump repair unless both of
them fail simultaneously.
Managerial procedures have evolved primarily from experience. The system was designed
so that fields can be dosed alternately, but the appropriate dosing cycles had to be
determined by operating the irrigation fields in accordance with their immediate purpose. For
example, if crops are grown that only require mowing, the closing periods can be much
shorter than if they require harvesting. The sprinkler heads were protected from stoppages by
placing a self-cleaning traveling screen with 1/4-inch openings in front of the pumps to remove
suspended debris, and this problem has very seldom arisen.
CHEMICAL, PHYSICAL, AND BIOLOGICAL MONITORING
Selected chemical and biological parameters are monitored throughout the system. The
wastewater is tested for pH, chlorides, orthophosphate, BOD5, COD, TOC, nitrate nitrogen,
nitrite nitrogen, Kjeldahl nitrogen, ammonia nitrogen, conductivity, and total and fecal
22
-------
coliform. To determine cause and effect relationships, groundwater samples from 23 monitor
wells undergo the same analytical tests as the effluent samples.
Soil solution sampling tubes were also installed throughout the irrigation plots at depths
ranging from 6 inches to 18 feet. The soil solution was difficult to collect when the wells had
low rates of loading, but not at high rates. At 300,000 gallons per acre per day loading rates,
laboratory analyses indicated that the concentration of orthophosphate dropped from 25 ppm
at the surface to 0.04 ppm at a depth of 10 feet.
Most of the ammonium nitrogen was converted to nitrate nitrogen in the upper 24
inches of soil. At loading rates high enough to collect solution samples in the 18-foot sample
tube, there was no clear evidence of denitrification or that the plants absorbed any
appreciable amount of nitrate nitrogen as the effluent percolated downward through the soil.
While density of fecal coliform bacteria in the influent was normally in the range of
10s-106 per 100 ml, the density in water from the monitoring wells was usually zero or
occasionally one or two bacteria per 100 ml. Additionally, because the nearest residences were
more than a mile away from the well-buffered spray irrigation site, the aerosol viral and
bacterial hazard was considered to be minimal and was not monitored.
Effluent Characteristics
From a pollution standpoint, the two primary nutrients are nitrogen and phosphorus. To
calculate their loading rates, the effluent is assumed to contain 25 ppm of total nitrogen
(nitrate + ammonia + organic nitrogen) and 10 ppm of total phosphorus. These values convert
to loading rates of 5.7 pounds of nitrogen per acre per inch and 2.3 pounds of phosphorus
per acre per inch, respectively. Previous work15 has shown that all nitrogen is converted
microbially to nitrate within the first 1 or 2 feet of well-drained soil. While microbial
denitrification takes place, the extent of denitrification has not been determined under
effluent irrigation. Loading rates for effluent containing the nitrogen and phosphorus
concentrations noted above are shown in table II-1.
Table 11-1.—Nitrogen and phosphorus loading rates
Irrigation rate
(inches/week)
1
2
3
4
Nitrogen applied
(pounds/acre/year)
300
600
900
1,200
Phosphorus applied
(pounds/acre/year)
120
240
360
480
23
-------
NITROGEN UPTAKE BY SELECTED GRASSES
Coastal Bermuda Grass—Rye Grass
According to Burton's data,16 presented in table 11-2, crop yields of up to 10 tons of
coastal bermuda grass per acre can reasonably be expected to remove 450 pounds of nitrogen
per acre. Nitrogen uptake by rye grass can be estimated from Overman's work15 presented in
table II-3. Burton also reported similar results.16 Therefore, based on crop yields of 3 tons
per acre, the removal of approximately 150 pounds of nitrogen per acre appears feasible. A
crop rotation schedule of coastal bermuda grass in the summer and rye grass in the winter
can potentially remove about 600 pounds of nitrogen per acre per year. Assuming an
irrigation rate of 3 inches per week and 25 ppm nitrogen, about 900 pounds of nitrogen
would be applied to the soil. The combination would have a 67-percent recovery efficiency.
Nitrogen uptake data for rye are presented in tables II-2 and II-3. Assuming a crop yield
of 2 tons per acre, a nitrogen uptake of approximately 200 pounds per acre per year could
be expected. Therefore, the coastal bermuda grass—rye grass combination could be expected to
utilize about 650 pounds of nitrogen per acre per year. With a nitrogen loading rate of 900
pounds per acre per year, the recovery efficiency would be 72 percent.
Table 11-2.— The uptake of nitrogen by selected grasses9
Nitrogen applied
(pounds/acre)
Dry weight of crop
(tons/acre)
Nitrogen content
(percent)
Nitrogen harvested
(pounds/acre)
Coastal bermuda grass*3
300
600
900
9.6
12.2
12.5
1.34
1.74
1.85
259
424
466
Rye grass"
400
3.5
2.16
150
Rye1
400
2.8
3.39
189
aAdapted from G. W. Burton, 1973.
bFor one cutting only.
24
-------
Table 11-3.—The uptake of nitrogen applied to the so/I in wastewater by rye and rye grass9
Irrigation
rate
(in. /week)
0.25
0.50
1.00
2.00
Nitrogen
applied
(Ib/acre)
12
25
50
100
Rye Grassb
Dry weight
of crop
(ton/acre)
1.06
0.87
0.93
1.03
Nitrogen
content
(percent)
1.97
2.03
2.35
1.75
Nitrogen
harvested
(Ib/acre)
47
39
49
64
Ryeb
Dry weight
of crop
(ton/acre)
0.60
0.69
0.90
1.00
Nitrogen
content
(percent)
4.21
4.61
4.62
4.79
Nitrogen
harvested
(Ib/acre)
57
71
93
107
aAdapted from G. W. Burton, 1973.
^For one cutting only.
Residual Nitrogen
With a crop rotation of either coastal bermuda grass and rye grass or coastal bermuda
grass and rye, efficiency of nitrogen recovery would be approximately 70 percent, leaving
about 7.5 ppm of residual nitrogen. Some of this remains in the root system of the plants
and is released when the roots decay. Carbon is also released during microbial decomposition.
It appears likely that some carbon moves down to the water table where it can be
metabolized by denitrifying bacteria to convert nitrate ions to nitrogen gas, which then
escapes. If 10 percent of the original nitrogen was lost by this process, then approximately
2.5 ppm would be denitrified. Under these conditions, no more than 5-ppm nitrate nitrogen
would remain in groundwater. The degree of denitrification under these conditions at
Tallahassee is not yet known.
PHOSPHORUS UPTAKE BY SELECTED GRASSES
Coastal Bermuda Grass—Rye Grass
Phosphorus uptake by coastal bermuda grass has been reported by Adams et al. and
some of their data are presented in table II-4.17 Assuming a crop yield of 10 tons per acre
with a phosphorus content of 0.25 percent, approximately 50 pounds of phosphorus would be
removed per acre per year. Parks and Fisher18 reported the phosphorus content of rye grass
to be approximately 0.25 percent. With crop yields of 3.5 tons per acre, about 18 pounds of
phosphorus would be removed per acre per year. Therefore, the crop combination of coastal
bermuda grass and rye grass would remove about 68 pounds of phosphorus per acre per year.
25
-------
Table 11-4.—The uptake of phosphorus by coastal bermuda grass3
Phosphorus applied
(pounds/acre)
0
21
42
84
Phosphorus crop content
(percent)
0.20
0.21
0.22
0.25
Phosphorus harvested
(pounds/acre)
7
16
25
36
aAdapted from Adams et al., 1967.
Since an irrigation rate of 3 inches per week of wastewater with a 10-ppm phosphorus
concentration would apply 360 pounds per acre per year, this combination would have a
recovery efficiency of 19 percent.
Coastal Bermuda Grass and Rye
The phosphorus uptake by rye is calculated to be approximately 14 pounds per acre per
year based on a crop yield of 2.8 tons per acre (table II-2) with a phosphorus content of
0.25 percent. The crop rotation combination of coastal bermuda grass and rye would utilize
approximately 64 pounds per acre per year of the 360 pounds applied by spraying. This is
equivalent to an uptake efficiency for this combination of 18 percent.
Residual Phosphorus
Whereas nitrate is highly mobile in soil, phosphorus is readily fixed as precipitates of
aluminum, iron, and calcium. The fixation capacity of lakeland fine sand appears adequate for
an estimated 75-year life span at the Tallahassee site.
If 360 pounds of phosphorus are applied to each acre of soil every year, and only 20
percent of it is removed with the crops, a residual phosphorus loading of 228 pounds per acre
would be added to the soil each year. The fixation capacity of 23,250 pounds of phosphorus
per acre to a 50-foot depth has been calculated on the assumption that the soil has a bulk
density of 1.70 gm/cm3 and can adsorb 100 ug of phosphorus per gm. Fiskell19 has shown
that for every application of 100 ug of phosphorus per gm of soil, (1) this same amount is
fixed, and (2) the solution would concentrate 1 ppm. Other values are shown in table II-5.
Field measurements of phosphorus movement in lakeland fine sand showed that of 3,200
pounds of phosphorus per acre applied over a 6-year period, all of it remained in the upper 4
feet of soil.19 This would be equivalent to 40,000 pounds of phosphorus per acre per 50
feet, which corresponds to the range shown in table II-5. Finally, it does not appear likely
that the fixation of phosphorus would cause soil clogging. For example, fixation levels of
100-, 200-, and 300-ug phosphorus per gm of soil have corresponded to mass increases of
only 0.01, 0.02, and 0.03 percent.
26
-------
Table \\-5.-Phosphorus fixation by lakeland sand3
Solution phosphorus
(ppm)
1
5
15
Adsorbed phosphorus
(ug/gm soil)
100
200
300
Phosphorus capacity
(pounds/acre/50 feet)
23,000
46,000
69,000
Life of siteb
(years)
75
150
225
aAdapted from J. G. A. Fiskell and R. Ballard, 1973.
"Assuming 3 inches/week, 10-ppm phosphorus, and residual phosphorus of 288 pounds/acre/year.
CROP MANAGEMENT
Cover crops for the fields were planned for year-round yields, a factor that is
considerably more important in the northern than in the southern regions of the state. Forage
crops are commonly grown year-round in the southeastern states. At Tallahassee, a practical
combination is coastal bermuda grass (summer) and rye grass or rye (winter). Both of them
have shown excellent growth and production under proper fertilization and irrigation. They
have the best uptake of nitrogen among all crops in common use today. Extensive
information is available on their management and utilization.
Overman's study15 indicates that coastal bermuda grass interseeded with winter rye will
utilize 600 pounds of nitrogen per acre per year. With 25 ppm as the concentration of total
nitrogen, 2 inches per week of effluent are required. This nitrogen will be removed from the
site when the crop is harvested. The phosphorus is expected to have minimal agricultural use.
However, the soils exhibit very high phosphorus fixation capacities. Therefore, this mechanism
will probably remove almost all of the phosphorus.
Cropping Practices
To maximize crop yields from grass, it is very important to establish a level sod. This
enables the harvester to clip closely at fast ground speeds without gouging the sod. A cutting
height of approximately 4 inches is recommended for both summer and winter crops. To
avoid damage to equipment, all tree roots and debris should be cleared from the land before
the grass is established. The land should also be disked thoroughly.
Grass should be planted on the site before any effluent is applied. Otherwise, native
grasses will grow and inhibit the establishment of a uniform sod. This is particularly true for
the summer season. Once established, either coastal bermuda grass, rye grass, or rye will
provide effective competition against weeds.
The summer coastal bermuda grass crop will have a growing season from May until
November. Either rye grass or rye can be overseeded for a winter crop and will have a
growing season from November until May. The coastal bermuda grass then will regenerate in
May following the last winter harvest.
27
-------
A cutting frequency of 6 to 8 weeks is recommended. This should provide a satisfactory
balance between high yields on the one hand and lodging on the other. The quality of forage
should also be adequate with this practice.
Irrigation Management
Experience has shown that to irrigate at a rate of 3 inches per week, one continual
application is more suitable than split applications, as the following analysis demonstrates.
Experiments at Tallahassee have shown that lakeland sand drains to a water tension of
60 to 70 cm. This corresponds to a water content of about 0.10. From experiments by
Overman and West,20 it may be deduced that at an irrigation itensity of 0.5 inches per hour,
the water content would rise to approximately 0.25. Hence, during the 6-hour irrigation
period, the 3 inches of effluent will be distributed over a soil depth of approximately 12
inches (3 inches/0.25) and will gradually redistribute over a depth of 30 inches (3
inches/0.10), which is still within the root zone of these forage crops. This should allow
adequate time for nutrient uptake in the root zone.
There are advantages to using one application each week. Less effort is required to rotate
the valves. Problems with plant disease and lodging are reduced by minimizing the time for
wetting the crops. Finally, harvesting operations are .made smoother with fewer irrigations, and
field drying is also facilitated.
28
-------
Chapter III
THE FLUSHING MEADOWS PROJECT
The Salt River Valley in central Arizona is an irrigated agricultural area undergoing rapid
urbanization. An acre of urban land does not use much less water than an acre of agricultural
land. However, whereas the agriculture is essentially consumptive, about 50 percent of the
water for urban use is returned as sewage. Approximately two-thirds of the water for
irrigation and municipal supplies comes from surface reservoirs on the Salt and Verde Rivers.
The remaining one-third is supplied from groundwater, essentially a nonrenewable resource.
While this groundwater level is presently dropping at a rate of about 10 feet per year, the
depletion could be reduced if the groundwater could be recharged with renovated wastewater
from the sewage effluent.
The main sewage treatment plants in the valley are the Phoenix 91st Avenue and 23rd
Avenue plants. Both are activated sludge plants that discharge their effluent into the Salt
River bed. Their combined flow is presently about 80 mgd. Each year, the flow increases by
about 5 to 6 mgd, mainly due to population growth. Thus, a flow of about 240 mgd or
about 270,000 acre feet per year can be expected by the year 2000. At an application rate
of 4.5 feet per acre per year, this source could irrigate some 60,000 acres of agricultural land.
In other words, at the current rate more water will be available for irrigation than agricultural
land will require to absorb it. The remaining municipal effluent can be reclaimed for other
purposes, such as industry and recreation.
To treat the effluent for unrestricted irrigation and recreation on a large scale necessitates
expanding the system beyond the present conventional activated sludge process. According to
Arizona standards,21 tertiary treatment is required to decrease the BODS and suspended solids
content to less than 10 ppm, and disinfectants must be applied as needed to keep the fecal
coliform density below 200 per 100 ml. Some of the nitrogen should also be removed from
the municipal effluent for large scale irrigation to avoid undesirable effects on the crop
quality or harvesting schedule. The nitrogen and phosphorus must be removed if the effluent
is used for recreational lakes. In a densely populated region such as the Salt River Valley,
large scale reuse of the effluent requires that it be treated to be aesthetically acceptable.
Because the hydrogeologic conditions in the Salt River bed are favorable for groundwater
recharge by surface spreading, high-rate infiltration from basins in the river bed can produce a
renovated effluent of the desired quality to be pumped out of the ground. To investigate the
feasibility of renovating the effluent in this manner, a pilot project was constructed in 1967
as a cooperative effort between the U.S. Water Conservation Laboratory, the Salt River
Project, and the city of Phoenix. For the first 3 years, the project was partially supported by
a grant from the Environmental Protection Agency.
29
-------
FLUSHING MEADOWS FACILITY AND ITS OPERATION
Description of Project
The pilot Flushing Meadows Project (FMP) is located in the Salt River bed about 1.5
miles downstream from the 91st Avenue sewage treatment plant. Secondary effluent is
pumped from the effluent channel into six parallel, horizontal basins that are each 20 feet by
700 feet and 20 feet apart (see figure III-l). Usually, 1 foot of water is held in the basins by
an overflow structure at their lower end. The infiltration rate is measured from the difference
between the inflow and outflow rates by critical depth flumes at each end of the basins.22
The infiltration rate for the 2-acre system is approximately 0.5 mgd.
Most of the soil in the basins is fine loamy sand to a depth of about 3 feet, then coarse
sand and gravel layers extend to about 250 feet, where a clay layer forms the lower boundary
CONSTANT-HEAD
STRUCTURE
SUPPLY LINE'
FLUME•
GRAVEL DAM
.PERMANENT
X EFFLUENT POND
r^a
=1 H
BASIN NS '
1
• 1-2
9
|=
»=^ I/I 2 |=
—^ jy 3 f—*
^^^
p^j pjl
WCW»* ECW
4
I=H
=i M
M w
5
• 5-6
6
F=
F=
C
_L
i it
50
1 I 1 1 1 1 1 I
100 200
• WELL
I
100 METERS
300 FEET
• 7
DRAINAGE LINE
LINED
PONDS
UNLINED
-TJ POND
•
EAST WELL
J
• 8
Figure 111-1. Flushing Meadows Project schematic.
30
-------
of the aquifer.23'24 The static water table is at a depth of about 10 feet. Observation wells
for sampling groundwater and renovated sewage water were installed in a line midway across
the basin area (figure III-l). All of the wells draw water from a depth of 20 feet except the
East Center Well and the West Center Well, which draw water from a depth of 30 and 100
feet, respectively.
Infiltration Rates
The infiltration rates in the basins generally decreased during flooding, but the rate was
restored during periods of drying.2 3 Maximum long-term infiltration or "hydraulic loading"
was obtained with flooding periods of about 20 days, alternated with drying periods of about
10 days in the summer and 20 days in the winter. With this schedule, from 300 to 400 feet
of water per year have been infiltrated from an average depth of 1 foot. At these rates, 3 to
4 acres of infiltration basin are required for each mgd of effluent.
Infiltration rates were higher in fully vegetated basins and lower in a gravel-covered
basin than in a bare soil basin.2 3 However, since the basins were flooded with a few inches
of water for a few days in the spring and early summer to allow the vegetation to develop,
less water was infiltrated in these basins than in the bare soil basin, where greater water
depths and longer flooding periods were maintained during the entire year. Thus, maximum
hydraulic loading is probably obtained in nonvegetated basins with water depths of several
feet. If the suspended solids content of the effluent can be kept below 20 ppm, little or no
sludge accumulates on the bottom of the basins, and they can be operated for several years
without having to be cleaned. On the other hand, annual or more frequent removal of
accumulated solids is necessary if the effluent has more than 20 ppm of suspended solids.25
WATER QUALITY IMPROVEMENT
Nitrogen
The average nitrogen content of the effluent is about 30 ppm, almost all of it in the
ammonium form. Since the annual infiltration is about 300 feet, the nitrogen load of the
system is in the order of 30,000 pounds per acre per year, much more than the few hundred
pounds per acre that can be removed from the soil each year by growing and harvesting
crops. These higher loads of nitrogen must be removed by biodenitrification in the soil.
Therefore, the system must be designed and managed to bring nitrate and organic carbon
together under anaerobic conditions. To do this, the flooding and drying periods of the basins
must be properly scheduled.
The effect of the flooding schedule on the form and concentration of the nitrogen in the
renovated water is shown in figure III-2. It applies to the renovated water from the East
Center Well which is located in the center of the basin area (figure III-l) and obtains water
from a depth of 30 feet. The renovated water from this well is mainly effluent that has been
infiltrated in basins 3 and 4. This water travels underground for about 40 feet over 5 to 10
days.
31
-------
40-
K
111
t 3
-------
take place during the dry period and after flooding is started because the nitrate will then
move down into the anaerobic zones with the newly infiltrating effluent. From the outlying
observation wells where the nitrate peaks are more dispersed, the overall nitrogen removal for
the 2- to 3-week flooding and drying periods was estimated to be about 30 percent. Figure
III-2 shows, however, that after the nitrate peak passes, the total nitrogen level in the
renovated water is nearly 90 percent less than that in the effluent. The 30-percent overall
nitrogen removal agrees with the results of laboratory studies.26
When long flooding and drying periods stimulate nitrogen removal by denitrification, care
has to be taken that more ammonium is not adsorbed by the soil during flooding than can be
nitrified during drying.27 If all the adsorbed ammonium is not nitrified during the drying
cycle, the cation exchange complex in the soil may become saturated with ammonium during
the subsequent flooding. This further reduces the adsorption of ammonium. Consequently, its
percentage will increase in the renovated water. When this is observed, a sequence of short
flooding periods, 2 days wet and 5 days dry for example, should be used to convert adsorbed
ammonium in the soil to the nitrate form. Some of these nitrates can then be denitrified,
particularly if a crop is grown. When the capacity of the soil to adsorb ammonium is
restored, longer flooding and drying periods can be used again to maximize nitrogen removal.
Nearly all of the nitrogen in the effluent can be converted to the nitrate form during
short flooding periods when the effluent is used for irrigation. Normally, several inches of
water are applied every 2 or 3 weeks. With such an application schedule, aerobic conditions
prevail in the soil profile, and the nitrogen in the effluent is converted to the nitrate form.
Because the water moving downward from a root zone of an irrigated crop has a salt
concentration several times that of the irrigation water,2 8 nitrate-nitrogen concentrations can
be higher in the deep percolation below sewage-irrigated fields, and can be higher than the
total nitrogen concentration in the sewage effluent itself. In fact, increased nitrate levels in
the groundwater below sewage irrigation fields are commonly observed.29'30
Phosphate
The concentration of phosphorus measured as orthophosphate in the effluent was about
15 ppm in 1969. It decreased to around 10 ppm in 1970 and remained the same in 1971
and 1972. Perhaps it stabilized because more low phosphate detergents were used. The
renovated water from the East Center Well contained about 50 percent less phosphate; and
Well 1, 100 feet north of the basin area, had about 80 percent (90 percent in 1972) less
phosphate than the effluent. The renovated water from Well 7, 100 feet south of the basins,
had somewhat more phosphorus than Well 1. This may have been because Well 7 is much
more permeable and hence has much coarser aquifer material than Well I.24
The phosphate removal has been fairly constant over the more than 5 years the project
has operated, while a total of about 1,400 feet of effluent were applied. Most of the
phosphate is probably removed when the calcium phosphate compounds precipitate in the soil
and underlying sands and gravels.
33
-------
Fluoride
Normally, 4 to 5 ppm of fluoride are present in the effluent. About 50 percent of the
fluoride is removed from the renovated water from the East Center Well and 70 percent from
Well 1. This parallels the phosphate removal and suggests that fluorapatities are formed in the
soil.
Boron
The boron concentration of the effluent has increased from about 0.4 ppm in 1968 to
about 0.8 ppm in 1971 and 1972. Boron is not removed as the effluent moves through the
sand and gravel layers of the Salt River bed. Instead, it concentrates in excess of 0.5 ppm in
irrigation water and could affect the yield of some of the more boron-sensitive crops in sandy
soils.3'
Salts and pH
The total salt content of the effluent and of the renovated water is usually in the 1,000-
to 1,200-ppm range. Evaporation from the basins would cause the salt concentration of the
renovated water to be about 2 percent higher than that of the effluent. The pH of the
effluent is generally around 8, decreasing to about 7 as it becomes renovated water.
Oxygen Demand
The BOD5 of the renovated water is usually less than 0.5 ppm, compared with a range
of 10 to 20 ppm for the effluent. The total organic carbon content of the effluent ranges
from 10 to 30 ppm, and that of the renovated water is from 2 to 7 ppm. Thus, while the
suspended solids and biodegradable carbon are essentially all removed as the effluent moves
through the soil, some organic carbon still remains in the renovated water.
Fecal Coliform Bacteria
The fecal coliform density in the effluent is normally in the range of 10s to 106 per
100 ml. This is usually reduced to about 0 to 10 per 100 ml in the renovated water from
the East Center Well although, occasionally, densities of several hundred per 100 ml have been
observed, particularly when newly infiltrated water reached the well when a long flooding
period began after a long drying period. The coliform density decreased as the renovated
water traveled further underground. No fecal coliforms have been detected after 300 feet of
lateral movement below the water table. Almost all of the coliform bacteria were removed in
the first 3 feet of soil.
34
-------
OPERATIONAL SYSTEM AND ECONOMIC ASPECTS
To renovate the present flow of about 100 mgd from the two Phoenix treatment plants,
about 375 acres of infiltration basins would be required, and this would have to be expanded
to about 900 acres if the projected 240-mgd flow were renovated in the year 2000.
Infiltration basins could be located along both sides of the Salt River bed, and the renovated
water could be pumped from wells in the center (figure III-3). This system should be designed
to avoid spreading the renovated water into the aquifer outside the Salt River bed, to ensure
a minimum underground travel time of several weeks and a distance of several hundred feet,
and to keep the water table from rising to more than about 5 feet below the bottom of the
basins during infiltration.24 The preceding data indicate that such a system would produce
renovated water of more than sufficient quality to permit unrestricted irrigation and
recreation.
The hydraulic properties of the aquifer were evaluated with an electric analog by
measuring water levels in the observation wells after infiltration.24 On the basis of these data,
water table profiles and underground detection times were projected for the system (figure
III-3) with different model layouts of infiltration basins and wells.24
The total cost to filter the effluent underground and the renovated water out of the Salt
River bed was estimated at about $5 per acre foot,32 or about $15 per million gallons in
May 1973, and today's cost may be 50 percent higher. Nevertheless, this is still much less
than the cost of equivalent tertiary treatment at a conventional sewage plant.
RIVER BED
INFILTRATION
BASINS
IMPERMEABLE
LAYER
Figure 111-3. Infiltration basins system on both sides of river bed with
center wells for pumping renovated water.
35
-------
Chapter IV
THE PENNSYLVANIA STATE UNIVERSITY WASTEWATER
RENOVATION AND CONSERVATION PROJECT
The Pennsylvania State University Wastewater Renovation and Conservation Project
(WRCP) was initiated in 1962 to evaluate alternative methods of preventing further
eutrophication of a stream that received effluent from a sewage treatment plant. A group of
scientists weighed a number of alternatives, including the feasibility, possible environmental
impact, and economics of applying treated municipal wastewater on the land by spray
irrigation. Other possible ways to protect the stream were to modify the existing sewage
treatment plant to remove more phosphorus and nitrogen, to dispose of the effluent in deep
wells, or to construct a new outfall to Bald Eagle Creek 10 miles away for an estimated cost
of $10 million. Instead, wastewater renovation was combined with conservation, and the term
"Living Filter" was coined to describe the concept of renovating and reusing municipal
wastewater by land application. The experts involved in planning the system included
agricultural, civil, and sanitary engineers, as well as agronomists, biochemists, ecologists,
foresters, geologists, hydrologists, limnologists, microbiologists, and zoologists.
Initially, approximately 0.5 of the 3.7-mgd flow of the plant was diverted to irrigate and
fertilize crops and woodlots. In 1968, plans were initiated to apply the entire plant flow of
approximately 4 mgd to the land. After a 4-year delay, the living filter system was expanded
to approximately 500 additional acres in the gameland area. However, the capacity of the
system was reduced to 3 mgd to stay within the allocated budget because construction costs
increased after this expansion was proposed in 1968. Presently, most of the wastewater
pumping plant and the 18-inch steel force main to the gameland have been completed. The
proposed solid set irrigation system is projected to be in operation by the end of 1975 or the
spring of 1976.
THE PENNSYLVANIA STATE UNIVERSITY FACILITY AND ITS OPERATION
The sewage treatment plant located on the eastern edge of the campus serves the
university and much of the borough of State College. The wastewater undergoes primary
treatment and either trickling filter or activated sludge secondary treatment. After secondary
treatment, the flows are combined before chlorination. The average concentrations as well as
the minimum and maximum values for selected chemical parameters are reported for 1971 in
table IV-1.33 The last column in the table shows the value of applying 2 inches of this
wastewater per week as fertilizer.
The chlorinated secondary effluent is pumped through a 6-inch asbestos-cement force
main at a rate of 350 gpm (0.5 mgd) to either the agronomy and forestry areas
approximately 2.5 miles away or the gameland area 2 miles farther away. Since the agronomy
and gameland spray areas are at ground elevations 180 feet and 280 feet higher than the
37
-------
sewage treatment plant, the effluent is pumped at 226 psi and delivered to the farthest
distribution head at approximately 40 psi, with correspondingly greater pressures at locations
closer to the pumping station (figure IV-1).
Table IV-1.—Chemical composition of sewage effluent applied during 1971 33
Constituent
PH
MBASb
IMitrate-N
Organic-N
NH4-N
Phosphorus
Calcium
Magnesium
Sodium
Boron
Manganese
Range
Minimum
(mg/l)
7.4
0.03
2.6
0.0
0.0
0.250
23.1
9.1
18.8
0.14
0.01
Maximum
(mg/l)
8.9
0.88
17.5
7.0
5.0
4.750
27.8
15.1
35.9
0.27
0.04
Average
(mg/l)
8.1
0.37
8.6
2.4
0.9
2.651
25.2
12.9
28.1
0.21
0.02
Total amount
applied3
(pounds/acre)
—
5
128
36
13
39
375
192
419
3
0.2
aAmount applied on areas which received 2 inches of effluent per week.
klvlethylene blue active substance (detergent residue) values are for 1970; constituent not included in analyses in 1971.
Approximately 60 acres of crop and forest land with various kinds of soil are irrigated
with the wastewater. In the agronomy-forestry area, the soil layer ranges in depth from 5 to
80 feet over a dolomite bedrock. The clay-loam is less permeable than other nearby soils. In
the forest, the mulch layer and undercover plants were not disturbed. The soil in the
gameland area is a deeper, sandy loam. Here, the soil overlay ranges from 20 to 160 feet
above beds of sandstone, dolomite, and quartzite. The depth of the groundwater varies from
about 100 to 350 feet.
The solid set sprinkler irrigation system has a flexible design that spaces the sprinklers
from 40 feet by 60 feet to 80 feet by 100 feet. After some experimentation with application
levels as high as 6 inches per week, most of the spray irrigation has been applied at a level of
2 inches per week in one continuous 12-hour period, with 6.5 days between sprayings. This
38
-------
WEATHER
STATION
1 MILE
TO UNIVERSITY
AIRPORT
INFILTRATION
PONDS
FORESTRY
AREA
UNIVERSITY WELLS
0 © 0
ARMY RESERVE
CENTER
NITTANY
LION INN
OLD MAIN
BEAVER STADIUM
! SEWAGE
j PLANT
L
TO SPRING CREEK
VIA THOMPSON RUN
CHLORINE
CONTACT
TANK
Figure IV-1. The Pennsylvania State University
Wastewater Renovation and Conservation Research Project.
39
-------
application level was maintained because the flow remained well below the infiltration
capacity of the soil, thus permitting good renovation.
The spray irrigation areas are surrounded by a buffer zone, but the buffer distance varies
and no attempt has been made to maintain any minimum buffer zone. In the gameland area,
some residences and a store are less than 300 feet from a spray area. Additionally, a new
community called "Toftree" is located along the gameland property line and in general
proximity to the spray areas that will be used when the expanded spray irrigation system
becomes operational in early 1976. Opinions have been expressed that aerosol pollution
hazards are minimal or absent.1
MONITORING
The chemical quality of a composite of the chlorinated, secondary treated wastewater
was analyzed as it was pumped through the sprinklers during each irrigation sequence. The
most consistently monitored chemical parameters and their average concentrations measured
for 1971 are presented in table IV-1, along with the range between minimum and maximum
values.
As the wastewater percolated through the soil, changes in its quality were measured by
taking samples from suction lysimeters 6 inches to 15 feet deep and from shallow monitoring
wells 6 to 50 feet deep. In addition, deep wells (150 to 300 feet) were installed to monitor
changes in the groundwater aquifer that supplies potable water to the university.
SCOPE OF THE RESEARCH
Crop Responses to Wastewater Effluent
At Penn State, several factors made the perennial grasses the most suitable crops for
lands receiving wastewater effluent. In general, they have fibrous root systems and form sod
that helps control erosion but still allows a high rate of infiltration. The grasses are tolerant
of a wide range of ecological conditions. They have a high uptake of nutrients over a long
period of growth. In 6 years, 2,127 pounds of nitrogen were applied to the reed canary grass
in 536 inches of sewage effluent and sludge. Of this, 2,071 pounds were removed in the
harvested crop, a 93-percent renovation efficiency. The average concentration of nitrate
nitrogen was 3.5 ppm in the percolate at the 4-foot depth in the effluent-irrigated areas and
0.2 ppm in the control areas. During the same period, 797 pounds of phosphorus were
applied in the wastewater, and 279 pounds were removed when the crop was harvested. The
overall crop renovation efficiency was 35 percent for phosphorus. Individual annual renovation
efficiencies varied from 24 to 63 percent for phosphorus removal by crops.34
40
-------
Forest Responses to Wastewater Effluent
The forests consisted of a red pine plantation (Pinus resinosa) and a sparse white spruce
plantation (Picea glauca) as well as mixed hardwood. The spray application rate was 0.25 inch
per hour, and the level ranged from 1 to 6 inches per week in spraying sequences that varied
from 23 weeks during the growing season to 1 full year. The forested areas were highly
efficient in removing phosphorus. For all application levels, the forest biosystem decreased the
phosphorus concentrations more than 90 percent at the 2-foot depth. However, the forest
biosystem was not as consistently efficient in reducing the nitrogen concentrations. A 6-year
average of the mean annual concentration of nitrate nitrogen was collected at the 48-inch soil
depth. Where varying total depths of wastewater were received, the soil measured from 0.2 to
0.6 ppm in the control areas and from 3.9 to 24.4 ppm of nitrate nitrogen in areas that
received 2 inches of effluent per week. The difference was due in part to the organic
character of the forest mulch, which promotes a higher degree of denitrification.
The growth of the trees varied considerably, depending on the species and the level of
application of the effluent. The white spruce and the young hardwoods grew the most when
they were irrigated at the level of 2 inches per week. In general, hardwood forests are not as
efficient as agronomic crops in removing the nutrients. For example, a corn silage crop
removed 145 percent of the nitrogen applied in the sewage effluent. In contrast, the trees
removed only 39 percent, and most of it was returned to the soil in falling leaves. The silage
corn crop also removed 143 percent of the phosphorus from the sewage effluent, 34>35 while
the hardwoods removed only 19 percent.
Wildlife Response to Wastewater Effluent
The leader deer technique was initiated to determine the animal's preference for or
avoidance of irrigated areas. The deer grazed on irrigated sites as readily as on the control
sites. In winter, wild deer rested and grazed within the ice-covered areas that had been
irrigated. Moreover, in the irrigated areas the winter carrying capacity for rabbits appeared to
be much greater than in the control areas, presumably because of improved living conditions
in "caves" under ice-covered brush. Here they could also eat the terminal branches of the
bent-over brush. Rabbits trapped in the irrigated areas were larger and healthier than those
taken in the control areas.36
41
-------
Chapter V
THE CITY OF BOULDER COLORADO PROJECT
Although Boulder has two existing secondary (trickling filter) plants with adequate
capacity to handle projected 1985 flows, the existing plants cannot provide treatment
sufficient to meet pending discharge requirements. The regional water quality management
plan for the area including Boulder calls for secondary treatment plus nitrification of ammonia
to a concentration less than 4.3 mg/1. In addition, Boulder wished to consider higher levels of
treatment than required by the state and federal regulations and asked.that treatment systems
be evaluated which would be capable of providing an effluent with the following
characteristics:
• BOD 5.0 mg/1
• Total nitrogen 5.0 mg/1
• Total phosphorus 0.1 mg/1
Boulder also requested that other treatment systems providing effluents of lesser quality
be evaluated. Thus, the resulting study considers a wide range of land treatment and Advanced
Wastewater Treatment (AWT) systems.
The design flow conditions for the Boulder Colorado Project (BCP) were:
Design Average Peak
daily, daily, rate,
Year mgd mgd mgd
1975 17.0 13.0 29.8
1985 20.0 15.3 35.0
1995 27.5 21.0 46.8
ADVANCED WASTEWATER TREATMENT CONSIDERATIONS
There are three AWT alternatives which have been examined. They are shown in table
V-l and described in the following paragraphs.
43
-------
Table V-1.—Alternatives—Boulder, Colorado
AWT-1 processes
AWT-11 processes
AWT-III processes
aPretreatment
aPrimary clarification
Oxygen-activated sludge
Secondary clarification
Flow equalization
Lime clarification (2 stage)
Filtration
Activated carbon
Selective ion exchange
Disinfection
aPretreatment
aPrimary clarification
aTrickling filters
Secondary clarification
Flow equalization
Nitrification
Denitrification
Lime clarification (1 stage)
Filtration
Disinfection
aPretreatment
aPrimary clarification
aTrickling filters
Secondary clarification
Nitrification
Disinfection
Effluent quality (maximum values, mg/l)
BOD
SS
NH3-N
NO3-N
Total N
Total P
TDS
AWT-I
3
1
1
1
2
0.1
500-600
AWT- 1 1
10
5
3
3
6
1
500
AWT-III
20
20
3
23
26
20
400
Existing treatment units.
Alternative AWT-I provides the highest degree of treatment of the AWT alternatives. The
existing pretreatment process, primary clarifiers, and final clarifiers would be used. A pure
oxygen-activated sludge system is used in lieu of the existing trickling filters to maximize the
reduction of soluble BOD. Phosphorus removal would be accomplished by two-stage lime
clarification, and suspended solids removal would be accomplished by mixed-media filtration.
44
-------
Carbon adsorption follows. Nitrogen removal would be accomplished by the selective ion
exchange process, with ammonium salts being recovered from the regenerate stream.
Disinfection would be accomplished by ozone generated from oxygen-enriched air from the
oxygen generation system required for the activated sludge process. Organic sludges would be
applied to the land while lime sludges would be recalcined and reused.
AWT-I1 utilizes the existing primary and secondary treatment process with minor
modifications to improve performance and hydraulic capacity. Flow equalization would be
provided prior to biological nitrification, followed by denitrification. Nitrification would be
accomplished by a pure oxygen-activated sludge system, followed by an anaerobic filter for
denitrification. Phosphorus removal would be accomplished by single-stage lime clarification,
followed by mixed-media filtration for further suspended solids removal. Disinfection would be
accomplished by ozone generated from oxygen-enriched air supplied by the onsite oxygen
generation system required for nitrification. Organic and chemical sludges would be disposed
of on the land.
AWT-III uses the existing primary and secondary treatment system with minor
modifications to improve performance and hydraulic capacity. Nitrification would be
accomplished by a pure oxygen-activated sludge system, and disinfection would be by ozone
produced from oxygen-enriched air supplied from the onsite oxygen generation equipment.
The organic sludges would be disposed of on the land.
AWT-I and II would exceed the pending discharge standards, while AWT-III closely
corresponds to these standards.
Table V-2 summarizes the cost projections (July 1974 basis) for the AWT alternatives.
These estimates are based on construction of all AWT processes to a capacity of 20-mgd raw
sewage flow in 1975 with an expansion of 27.5 mgd (the 1955 design flow) in 1985.
LAND TREATMENT CONSIDERATIONS
The eastern part of Boulder County is a semi-arid area with insufficient precipitation for
peak crop growth and a limited supply of surface water. In addition, there are extensive
irrigation systems in the area and much of the wastewater discharge is diverted. Flooding
(rather than spray irrigation) is the present method of irrigation and is the technique used in
evaluating the potential land treatment systems. Water rights involved in new diversions of
wastewaters are complex on the eastern slopes of the Rockies but, for the purposes of this
publication, it is not necessary to discuss the details of the water rights in the Boulder area.
The reader is cautioned that, in many parts of the country, the evaluation of water rights can
be an important aspect and competent legal advice should be sought.
Alternate Irrigation Systems
The alternatives of irrigation, high-rate irrigation, and infiltration-percolation (as defined
in table V-3) were considered. All have been used for treatment of municipal wastewater,
both in this country and elsewhere. The objectives and characteristics of each of the processes
are distinctly different. The quality of the water returned to the stream or groundwater will
45
-------
Table \J-2.-Cost of AWT Alternatives (BCP)
AWT-I
Total capital costs3
Maximum annual 0 & M costs
1975 expansion
to 20 mgd
$28,975,000
1,893,000
1985 expansion
to 27.5 mgd
$17,181,000
2,474,000
All costs, present value
All costs, present value
All costs, present value
$53,334,000
AWT- II
Total capital costs
Maximum annual O & M costs
$18,500,000
1 ,404,000
$11,777,000
2,004,000
$37,187,000
AWT-I II
Total capital costs
Maximum annual O & M costs
$10,415,000
821,000
$ 7,292,000
1,232,000
$21,752,000
Includes 20 percent construction contingency, 12 percent
legal, and administrative fees (cost on July 1974 basis).
for construction financing, and 15 percent for engineering.
differ within a process depending on loading rate, soil characteristics, crop type, and
operation. The loading rate should be considered carefully since it influences the quality of
return flows. Loading rates and land area requirements overlap for the different processes,
making clear distinction difficult. The irrigation alternative is compatible with existing
irrigation practices in the Boulder area and effluent could be supplied to existing private
irrigation ditches. The high-rate process conflicts with local practices because the disposal of
effluent takes priority over crop production. It was concluded that the city would have to
own the land to make the high-rate system practical. Table V-4 summarizes the effluent
quality projected for each of these systems when applied in the Boulder area in accordance
with the criteria discussed herein. All of the land treatment processes produce an effluent
quality which exceeds pending discharge standards.
46
-------
Table V'-3.—Characteristics of land application processes considered for the BCP
Irrigation
High rate
irrigation
Infiltration-
percolation
Annual
loading
<1 to >5
ft/yr
1 to >10
ft/yr
11 to 500
ft/yr
Land area
requirement
for 1 mgd
flow
<225 to >1,100
acres plus buffer
areas, etc.
<110 to 1,100
acres plus
buffer areas.
etc.
2 to 100
acres plus
buffer
areas, etc.
Objective
Maximize agricul-
tural production.
Maximize water
and treatment by
evapotranspiration
and percolation
with crop produc-
tion as a side
benefit.
Recharge water or
filter water; crop
may be grown with
little or no benefit.
Suitable
soils
Suitable for irri-
gated agriculture.
More permeable
soils suitable for
irrigated agricul-
ture; many use
soils marginal be-
cause of coarse
texture.
Highly permeable
sands and gravels.
Dispersal of
applied water
Most to evapor-
transpiration. Some
to groundwater;
little or no runoff.
Evapotranspiration
and groundwater;
little or no runoff.
To groundwater.
some evapotrans-
piration; no runoff.
Impact on
quality of
applied water
BOD and SS re-
moved. Most
nutrients consumed
in crop or fixed.
TDS greatly
increased.
BOO and SS
removed.
Nutrients reduced.
TDS substantially
increased.
BOD and SS
reduced. Little
change in TDS.
Table V-4.—Effluent quality associated with land treatment alternatives
BOD
SS
NHs-N
NO3-N
Total N
Total P
TDS
Pretreatment
Maximum values, mg/l
Irrigation
1
1
0.5
4.5
5
0.1
2,000
Aerated lagoon treat-
ment of existing
effluent
High-rate irrigation
1
1
0.5
4.5
5
0.2
860
Existing treatment
only
Infiltration-percolation
5
5
I
9
10
2
770
Existing treatment
only
47
-------
General Design Criteria
The criteria used to establish potential areas for the various land application processes
were:
• Site should not endanger rare and endangered plant or animal species.
• The site should not conflict with present land use and should reinforce the adopted
land use plans.
• Presently irrigated areas should be used as much as possible to minimize the water
rights problem.
• The site should minimize the socio-economic impact on the community and the
traveling public. The number of dwellings, other buildings, and miles of road on the
site should be considered.
• Emphasis should be given to the use of greenbelt lands when practical.
• Preference should be given to soil groups which are most suitable for the various
land application processes as shown in table V-5.
Table V-5.—Soil suitability for land application processes
Soil group
1
2
3
4
5
Irrigation
Very suitable
Very suitable
Suitable
Low suitability
Unsuitable
High-rate irrigation
Maximum
High
Moderate
Low
Unsuitable
Infiltration-percolation
Moderate
Moderate for high permeability
Very low
Maximum for high permeability soil
Unsuitable
Soil suitability for the irrigation and high-rate irrigation processes is very similar, as
shown in table V-5. A considerable area of the most suitable soils, Groups 1 and 2, are
available in the study area. The soil most suitable for the irrigation and high-rate irrigation
processes also has the highest capacity for adsorption and removal of various pollutants,
including nutrients, heavy metals, etc. The least suitable group (4) and unsuitable group (5)
soils coincide with grassland and other uncultivated areas.
The infiltration-percolation process requires highly permeable soil and surficial geology
capable of transmitting large volumes of water. This material will not provide the degree of
treatment possible with the irrigation and high-rate irrigation processes. Soil which is suitable
for irrigation or high-rate irrigation will not be suitable for infiltration-percolation and vice
48
-------
versa. The material most suitable for the infiltration-percolation process is the coarse-textured,
most permeable portions of alluvial material characteristics of Class 4 soil.
Site Evaluation
The potential irrigation or high-rate irrigation sites and two potential infiltration-
percolation sites were identified and evaluated by the following criteria:
• Loading rate—Detailed soil information from the Soil Conservation Service was used
to evaluate soils on the potential sites. The following design and evaluation criteria
were used:
— Well-drained or easily drainable soil
— Intermittent application to provide ample opportunity for soil aeration
— Soil profile depths of 5 feet or more
— High absorptive capacity for pollutant removal
— Choice crop suitability and/or high denitrification rates to maximize nutrient
removal
— Maximum loading rate for high-rate irrigation of 7 feet during April/October
season loading rate (This rate is reduced proportionately by shallow root depth,
rock in the soil, and low permeability.)
- Infiltration-percolation process loading rates proportional to 12.5 percent of the
permeability
— Gross area based on the net area required plus areas for roads, buffers,
operation, and unsuitable land (as a percent of total area)
• Area considered—Only sites within the study area and within the Northern Colorado
Water Conservancy District boundary were considered. Preference was given to sites
entirely within Boulder County.
• Power requirements—To reduce the power requirements, the differential elevation
between the treatment plant and the potential site should be minimized.
• Buffer areas—Buffer width requirements are dependent on the irrigation method and
degree of pretreatment prior to application. The buffer width required for surface
(flooding) irrigation methods selected for this study may be less than 50 feet.
• Slopes—Land slopes greater than 15 percent were considered unsuitable for any
waste water application. Slopes greater than 6 percent were considered unsuitable for
surface (flooding) irrigation methods.
49
-------
• Site treatment capacity—To foster economics of scale and to obviate additional
water rights analyses, only sites capable of treating the 1995 design flows on a
contiguous area were considered.
• Storage—Because of the requirement for winter storage of effluent, the site selected
should be in proximity to a suitable storage location. The storage of secondary
effluent also will require storage rights, so existing storage facilities were considered.
• Site area—The costs for development of an irrigation site are proportional to the
area required for treatment. Thus, sites with the highest treatment capacity per unit
area were given preference.
• Water rights-In order to minimize problems regarding the water rights, preference
was given to sites within the Boulder Creek watershed and to sites where ditches
terminated within site boundaries.
Area! Requirements
In the Boulder area, the average annual effective precipitation is 10 inches/year. The
potential evapotranspiration (ET) was determined for several types of crops and is shown in
table V-6. Based on the assumed cropping pattern shown in table V-6, a mean
evapotranspiration of 25.8 inches per year was determined. Using a 70-percent irrigation
efficiency (consistent with irrigation design procedures and local practices), a requirement of
22.6 inches per year was determined for the irrigation alternate which maximizes crop
production. This is equivalent to about 590 acres/mg treated for the irrigation alternate.
The allowable hydraulic loading for the high-rate irrigation process is dependent only
upon the soil's capacity for transmitting water and not on crop irrigation requirements. The
maximum hydraulic loading is the sum of soil moisture depletion plus that quantity which
can be transmitted through the root zone. The soil moisture depletion was determined to be
12.3 inches for the season. The soils in the potential sites were classified using the hydraulic
loading criteria shown in table V-7. The best site had an allowable average loading rate of 6
feet per year, which is equivalent to an irrigated area requirement of 186 acres/mg.
The loading rate for the infiltration-percolation process is dependent on the soil and
surficial geology for infiltration and treatment. As loading rates increase, the treatment
provided will generally decrease; thus, a balance between treatment and loading rates is
important. A soil classification for high loading rates was developed from detailed soil maps.
Weighted average loading rates for the sites were estimated at 30 feet per year.
Irrigation Season
Climate is a constraint on the timing of effluent application on land. Soil temperature
data indicated that the soil in the study area may be frozen during parts of some years from
November through March. For the irrigation and high-rate irrigation processes, effluent would
not be applied during periods of frozen ground because runoff directly to the surface waters
could occur. The April through October period was used as the maximum effluent application
50
-------
Table V-6.—Crop evapotranspiration and irrigation requirements (in inches)
Month
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Total
Study area
mean
effective
precipitation
0.2
0.3
0.6
1.2
2.1
1.4
1.1
1.0
0.8
0.7
0.4
0.2
10.0
Mean
potential
ETa
0.2
0.3
0.6
1.2
3.0
5.5
7.0
4.5
1.8
1.1
0.4
0.2
25.8
Average
supplemental
irrigation
requirement'3
0.0
0.0
0.0
0.0
1.3
5.9
8.4
5.0
1.4
0.6
0.0
0.0
22.6
ET
corn
(silage)
0.1
0.2
0.3
0.5
1.9
4.8
7.6
4.0
0.8
0.5
0.2
0.1
21.0
ET
pasture
0.3
0.5
1.0
2.0
3.8
5.3
6.5
5.8
3.4
2.0
0.7
0.4
31.7
ET
alfalfa
0.4
0.6
1.2
2.3
4.5
6.5
7.9
6.8
3.9
2.3
0.9
0.4
37.7
ET
spring
grain
0.1
0.2
0.3
1.1
4.4
7.3
4.3
1.8
0.8
0.5
0.2
0.1
21.1
aBased on an assumed cropping pattern of 1/2 corn, 1/4 pasture, 1/8 alfalfa, and 1/8 spring grain.
"(Mean potential ET minus mean effective precipitation) divided by 70-percent irrigation efficiency.
season. Maximum effluent loading will also be limited to the active growing season. Plant and
soil microorganism activity is greater during this time, so treatment of the effluent would be
most effective.
For the infiltation-percolation process, the soil is much coarser to allow higher loadings.
Because of the coarse soil required to make this process successful, applications of warm
effluent may keep the soil from freezing for all but the most severe portion of the winter.
Applications would be made for 10 to 11 months of the year. Water would be applied for 5
days, followed by 10- to 20-day rest periods.
Alternate Land Treatment Considerations
Alternative L-I involved the irrigation process as defined in table V-3. Secondary effluent
would be distributed by existing ditches to privately-owned land. Water would be applied by
surface irrigation, mostly furrows, as commonly employed in the area. The irrigation ditches
and all irrigated land would remain in private ownership, with the ditch company maintaining
management and operation of the system. A long-term contract between the city and the
ditch company would provide the basis for continuing operation of the system. Secondary
effluent would be delivered directly to a winter storage reservoir, where it would be stored
51
-------
Table V-7. —Estimated maximum hydraulic loading of wastewater
effluent for various soil textures (ideal conditions)3
Very coarse textured sands and fine sands
Coarse textured loamy sands and loamy fine
sands
Moderately coarse textured sandy loams and
fine sandy loams
Medium textured very fine sandy loams, loams,
and silt loams
Moderately fine textured sandy clay loams and
silty clay loams
Fine textured sandy clays, silty clays, and clays
Basic
infiltration0
0%-4% slope
1.0+
0.7-1.5
0.5-1.0
0.3-0.7
0.2-0.4
0.1-0.2
Movement through
soil root zonec
in./day
20
10
4
2
1
0.5
in./yr
600
300
150
90
40
10
Proportionate reductions must be made for various problems such as percentage of rock, soil depths less than 5 feet,
or restrictive layers (frangipans, claypans, etc.).
^Values shown are for bare soil; for good vegetative cover, increase tabled values by 25 to 50 percent; for slopes
between 4 to 8 percent, reduce tabled values by 25 percent; for slopes greater than 8 percent, reduce tabled values by 50
percent.
cPrecipitation plus effluent less evapotranspiration.
during the winter and released for irrigation during the peak demand periods. For the
projected 1995 flow of 7,665 mg/year, approximately 15,000 acres (12,000 acres net
irrigated) are required for this alternative. A suitable site was found.
For Alternative L-I, the city would be required to provide restitution for additional
expenses incurred by the ditch company. This would include:
• Limited future development within the site area
• Increased maintenance
• Increased reservoir capacity
• Control of return flows from canals and irrigated farms
• Correction of drainage problems developed as a result of the increased water supply
52
-------
Although Alternative L-I would produce the highest level of wastewater treatment
possible with land application, management and operation of the system will be out of the
city's direct control, thus reducing reliability.
Alternative L-II involves the high-rate irrigation process on city-owned and city-managed
land. Storage of secondary effluent would be necessary during the winter months.
Approximately 5,000 acres (4,060 acres net irrigated) are required for this alternative.
Alternative L-II would provide an intermediate level of treatment but may approach the
level of treatment in Alternative L-I. Because management and operation of the system will be
under the city's control, the reliability of operation would be improved over Alternative L-I.
However, because loading rates would be higher, there is a corresponding higher risk of
polluting the soil and groundwater. Salt loading may be increased with high-rate irrigation
because of the increased leaching through a highly calcareous subsoil. The salt concentrations
of the subsurface drainage would be lower than with the irrigation process because less total
volume of water would be consumed by evapotranspiration. Effluent would be applied by
surface irrigation utilizing both borders and furrows for this alternative. Automation would be
provided to reduce labor requirements and improve control of the water.
Alternative L-IH is the infiltration-percolation process on a site owned and managed by
the city. The application season for this alternative will extend over more than 10 months,
requiring minimal storage. Approximately 1,120 acres (815 net irrigated) are required for this
alternative.
Secondary effluent for Alternative L-III would be applied on flood plain land which is
presently partly within proposed greenbelt land. This alternative would minimize land area
requirements and the necessary storage capacity, thus minimizing the environmental impacts.
Secondary effluent would be applied using the basin method of surface irrigation on land
adjacent to the sewage treatment plant. A lower level of treatment would be provided by this
land application alternative than for Alternatives L-I and L-II. However, it would exceed the
quality required for discharge into the stream. The proposed site has a high water table and
would necessitate a subsurface drainage system to prevent water logging of the soil. This
drainage system would collect and return to the surface water virtually all effluent applied to
the site. There would be no flow of effluent outside of the site boundary within the
groundwater system. Drainage water would be monitored before discharge to surface water.
Land Treatment Alternative Evaluation
ALTERNATIVE L-I. Figure V-l presents a schematic representation of Alternative L-I
which was partly described earlier. As shown in figure V-2, 65 percent of applied water is
consumed by crop evapotranspiration. An estimated 27 percent of applied water would
percolate to the groundwater system. Approximately one-tenth of this percolated water would
be collected by subsurface drainage and discharge to surface streams. In addition to the crop
consumptive use, there is an 8-percent nonbeneficial evaporation and evapotranspiration of
water from reservoirs, canals, and the surface runoff collection system. This 8 percent includes
water lost from the soil surface and phreatophyte vegetation adjacent to the surface water
bodies.
In Alternative L-I, the effluent would be delivered from the treatment plant to storage
by gravity through 43,600 feet of 66-inch buried concrete pipe. The pipe would be lined to
53
-------
UJ
2
O
P
m
£
to
E
tr
HI
i
O
CO
•
CO
2
2 £ 1 2
S
TORAGE FACILIT
RELEASE
EASUREMENT M
CONTROL
co S
^
BUTION
DISTRI
1
1
1
185..
^
ODIFICAT
STRIBUTI
ANAGEME
»•
c . . .
g
LJ
LI
1
SOSZ %
^
i O
^ r™ t ~i
SYSTEM
->
HEADGATE
MEASUREMENT
-+
IRRIGATION OF
PRIVATE FARMS
z
-<
-<
^v
•<
-<
-<
r v
Ul U.
U U.
< 0
? =
3tt
<
K
O
<
5
o
o
to
O5
CD
CO
OJ
•o
CO
>
£J
s>
54
-------
z
o
H
03
tt
cc
111
O < o
2$*.
UJ < Z
<
o
CO
en
ii uj
i- tt
33
= 2
£ 5
O
HI
O
"- Z
O <
< o Q
cc i: ui
1 t~ z
I < £
OOg
Zl ^
- t
O
o
z
o
o
cc
o
UJ
f- UJ
O O
UJ <
O ui
Z y
«• 2
"I
1^
0 D
Z V)
o £
u
tr
O
<
5
I
u.
OJ
03
<->
03
CD
(O
CN
OJ
u.
UJ
O "J
< g
u. <
CC Z
<
OL
o Q
cc
^
z
o
I s
UI
^
-------
prevent corrosion and would be sized to carry the peak 1995 flow. A total storage capacity
of 17,000 acre feet is required by 1995 and would be achieved by a combination of enlarging
an existing reservoir to 12,000 acre feet and adding a new 5,000-acre foot reservoir in 1985.
The effluent would be released from the reservoir(s) by pumping to the portion of the
distribution system above the reservoir and by gravity flow to distribution systems below the
reservoir. The existing irrigation system would be used wherever possible to distribute effluent
to the farms. The effluent flow from the reservoir would be measured to meet the irrigation
demands.
The irrigation return flow water from field runoff (including a 10-year storm runoff) and
irrigation ditch operational spills would be collected and returned for reuse by a runoff
collection system. The initial stage return flow would be collected by about 14 miles of 1- to
3-cfs unlined ditches. These ditches would drain into sumps and the effluent would then be
pumped through concrete pipe to the reservoir and various canals for recycling. Additional
ditches and return pumps would be required by 1985. It was estimated that the improved
water supply would result in the requirement for subsurface drainage of about 10 percent of
the total area. The drains would be 3- to 6-inch corrugated polyethylene agricultural drains at
a depth of 8 feet and spaced at 200 feet. Larger collector drains would collect this drain
water and discharge it into Boulder and Dry Creeks.
For the 1985 flows (step 1 development), a total area of 10,000 acres, with
approximately 8,400 irrigated acres, will be required. The total area required for step 2 at the
1995 level of development will consist of 15,000 acres, with approximately 12,100 acres
irrigated.
ALTERNATIVE L-II. Figure V-2 summarizes this alternative. Because of the higher
application rates, a much larger portion of the applied wastewater returns to the streams
rather than being lost to the atmosphere. As in Alternative L-I, the wastewater would be
delivered to the storage facility by gravity. Storage would again be provided by expanding an
existing reservoir and adding a new reservoir in the future. The existing distribution ditch
capacity would be inadequate for this alternative and would be enlarged. Many of the
irrigation sublaterals, structures, and on-farm systems would be enlarged and rehabilitated to
create greater capacity and reliability for the higher irrigation rates. Considerable site
preparation would be required to effectively control flows and ensure reliability. Surface
runoff would be collected in 2- to 3-cfs capacity unlined ditches and recycled to the irrigation
system in a manner similar to Alternative L-I.
Subsurface drainage would require approximately 436,000 feet of 4-inch-diameter
corrugated plastic pipe, at a depth of 8 feet and spaced at 300 foot intervals, to drain the
step 1 area adequately for 1985 flows. The subdrainage would be collected by collector drains
8 feet deep. The collector drains would feed three sumps which vary in capacity from 3.5 to
9.5 acre feet. Step 2 construction (for 1995 flows) will require an addition of 145,000 feet
of subdrainage lines and additional subdrainage collection lines. Once the subdrainage water is
collected, a network of pumps and pipelines would deliver this drainage water back to
Boulder Creek and discharge it at a point near the existing treatment plant.
ALTERNATIVE L-III. Alternative L-III, the components of which are shown in figure
V-3, would require the least land area of any land application system considered. This
alternative consists of the application of the infiltration-percolation process to a city-owned
site located on alluvial material adjacent to Boulder Creek. Application would be made
throughout the year except during extremely cold weather, as noted earlier. A storage
reservoir with a storage capacity of 1.2 months average winter flow will be required. Loading
rates for this alternative would approach 30 feet per year.
56
-------
z
o
a
cc
O
CD
C
k_
CD
C
o
I
o
0)
Q.
C
O
o
I
UJ >
UJ <
u. <
SS
LU
Z
DELIVERY
SYSTEM
FACILITY
SE AND
FROL
STORAGE
RELEA
CON
TION AND
REMENT
DISTRIBU
MEASU
RATION-
VTION ON
JED LAND
INFILT
PERCOL/
CITY-OWM
k
SUBSURFACE
DRAINAGE
O UJ
LU CC
a Q
< z
2 <
<
cc
Q
cc
C5
<
5
0)
•*-•
CO
CD
TJ
C
CO
>
£
g>
u_
UJ
* a
tc 5
57
-------
A water balance (see figure V-3) for this alternative indicates that 92 percent of the
applied water would be returned to the surface stream via the subsurface drainage system.
Five percent of applied water would be beneficially used in growing crops. Three percent
would be lost to nonbeneficial evaporation from water surfaces and evapotranspiration from
phreatophytes.
In this alternative, the effluent would be delivered to the reservoir with a low lift pump
through 2,000 feet of pipe. The storage reservoir would consist of two cells totaling 135 acres
of surface with an average depth of 18 feet. A total storage volume of 2,400 acre feet would
be available. This is a storage capacity of 1.9 months in 1975 and 1.2 months in 1995. The
effluent would be pumped to a buried distribution system which would distribute the water
to the infiltration basins.
The infiltration basins would be leveled to a flat bottom and will range in size from a
few acres to over 30 acres. On the steeper slopes, the basins may be as narrow as 200 feet,
while for the flatter slopes the width would be as wide as 600 feet. Lengths would range
from 500 feet to 3,000 feet, with 2,000 to 2,500 feet being an average length. Berms with a
total width of about 50 feet and height of 3 feet would be provided between basins. Effluent
would be applied on the surface at a depth of approximately 1 foot for a time period of
several days, followed by several days rest period. The water would infiltrate the surface and
move to the ground water through permeable sand and gravel.
Corrugated polyethylene drainage pipe would be used to collect subsurface drainage. The
spacing for the drainage tiles would be approximately 95 feet and they would be buried to a
depth of 12 feet. Because of the high loading rates and the rapid percolation to the
groundwater with this alternative, drainage tiles up to 15 inches in diameter are required to
the 95-foot spacings to carry away the subsurface drainage water. The gravity subdrainage
collector system would collect the tile drainage and deliver it to pump stations or directly to
Boulder Creek.
Cost of Land Treatment Alternatives
A number of assumptions were made in making the economic evaluation:
• A 20-year planning period beginning in 1975 was selected for economic comparison
purposes. Capital costs were amortized over a 20-year period at a 7-percent interest
rate as required for Environmental Protection Agency facilities plans.
• As with the AWT alternatives, expansion or phasing of the proposed treatment
facility would be accomplished in two steps. For comparison purposes, the initial
step was assumed to begin operation in 1975 and the second step in 1985. The first
step of the expansion program would be able to provide adequate treatment until
approximately 1985 and the second step to 1995. Because of the implementation
time required, none of the alternative plans could actually be implemented by 1975
(as discussed later).
• All construction costs presented are adjusted to reflect the construction cost in the
Denver metropolitan area in July 1974.
• Operation and maintenance costs also have been adjusted to reflect July 1974 costs.
58
-------
• All construction costs include a 20-percent construction contingency allowance and
12-percent allowance for interim financing during construction, which is expected to
last at least 2 years.
• Engineering, legal, and administrative fees are estimated to equal 15 percent of the
total construction cost.
• In Alternative L-I, it was assumed that the city would purchase the development
rights for the privately-owned land at a cost of $1,500 per acre. In Alternatives L-II
and L-III, it was assumed the city would purchase the land at a cost of $2,500 per
acre.
• In Alternative L-I, the income was assumed to be $4.50 per acre foot of water
based on existing irrigation water costs. In Alternative L-II, the income was
estimated at $100 per acre based on typical lease rates of $50 per acre plus the
value of the nutrients in the effluent estimated at $50 per acre. In Alternative L-III,
the income was estimated at $50 per acre.
Tables V-8, V-9, and V-10 summarize the estimated costs of each of the land treatment
alternatives. Table V-l 1 compares the costs for the irrigation system in Boulder. The marked
effect of local conditions upon system costs is apparent from this table. Boulder represents
the favorable end of the spectrum in many regards.
Land Treatment Implementation Considerations
Alternatives L-I and L-II would necessitate a relocation of a state highway, which would
require extensive public hearings and approval of the Federal Highway Administration. In
addition, a special-use permit would be required for implementation, also involving extensive
public hearings. Detailed field studies of soil and surface geology and water rights would also
be required. It was estimated that 4.5 to 5.5 years would be required to completely
implement the land treatment alternatives.
The implementation of Alternative L-I would affect farmers living on the site for the
following reasons:
• Crop productivity per acre would increase due to an improved water supply.
• The reliability of the water supply would also increase, facilitating crop planning and
minimizing the dependence on precipitation.
• The gross agricultural productivity of the site would increase due to additional land
brought under irrigation.
If this plan were implemented, the production of root crops like sugar beets and onions
would be terminated. Farmers who are acclimated to growing these types of crops may resist
changing to forage crop production, irrespective of economics.
59
-------
Table V-8.—Cosfs of Alternative L-l
Cost item
Construction costs
Pretreatment
Flow equalization
Delivery
Storage
Distribution
Runoff collection/return
Drainage collection
Site preparation
Organic sludge disposal
Subtotal
Administrative and engineering
Land
Legal and administrative
Total capital costs
Maximum annual O & M costs
Annual income
Step 1
$ 1,325,000
890,000
5,302,000
2,496,000
621,500
846,200
562,000
10,000
3,127,000
$15,179,700
$ 2,376,300
15,000,000
667,000
33,123,000
903,000
( 77,000)
Step 2
$ 680,000
615,000
—
1,686,800
1,131,200
310,900
228,000
2,000
726,000
$ 5,378,900
$ 807,100
7,500,000
333,000
14,020,000
1,139,000
( 106,000)
Present worth of all costs = $40,637,000
60
-------
Table \f-9.-Costs of Alternative L-ll
Cost item
Construction costs
Pretreatment
Flow equalization
Delivery
Storage
Distribution
Irrigation
Runoff collection/return
Drainage collection
Drainage return
Site preparation
Organic sludge disposal
Subtotal
Administrative and engineering
Land
Legal and administrative
Total capital costs
Maximum annual 0 & M costs
Annual income
Step 1
$ -
890,000
5,250,000
814,000
603,400
819,000
372,500
3,011,300
2,110,200
211,000
3,127,000
$17,209,200
$ 2,581,800
12,500,000
1,800,000
34,091,000
881,000
( 500,000)
Step 2
$1,110,000
615,000
—
349,000
148,500
267,500
20,000
801,600
—
66,000
726,000
$4,104,500
$ 615,500
—
—
4,720,000
1,037,000
( 470,000)
Present worth of all costs = $35,099,000
61
-------
Table V-10.-Cosfs of Alternative L-lll
Cost item
Construction costs
Pretreatment
Flow equalization
Delivery
Storage
Distribution
Irrigation
Drainage collection
Drainage return
Site preparation
Organic sludge disposal
Subtotal
Administrative and engineering
Land
Legal and administrative
Total capital costs
Maximum annual O & M costs
Annual income
Step 1
$ -
890,000
244,600
1,261,000
2,249,000
1,935,600
3,549,600
1,507,000
82,700
3,127,000
$14,846,500
$ 2,226,500
2,785,000
1,000,000
20,868,000
732,000
( 41,000)
Step 2
$1,110,000
615,000
—
—
841,000
668,600
1,305,300
87,600
26,900
726,000
$5,380,400
$ 807,600
—
—
6,188,000
858,000
( 41,990)
Present worth of all costs = $27,277,000
62
-------
Table V-11.—Comparison of irrigation system costs
Distribution
Surface runoff collection/return
Subsurface drainage and return
Site preparation
Irrigation system
Total
Costs per mgd of capacity
Costs/irrigated acre
Alternative l_-lb
$ 146
96
66
1
a
$ 309
$134,836
Alternative L-llc
$ 185
97
1,458
68
268
$ 2,076
$306,493
aUses existing, privately-owned systems.
b12,000 irrigated acres, 27.5-mgd capacity.
°4,060 irrigated acres, 27.5-mgd capacity.
For reasons similar to those mentioned above, the adoption of Alternative L-II would
increase the agricultural productivity of the affected land; however, crop diversity will be
limited to forage crops. The economic value of the crops grown on the site would be as high
or higher than present due to higher yields per acre and high marketability.
Comparison of Treatment Alternatives
LAND REQUIREMENTS. Alternative L-I would restrict development on 15,000 acres of
privately-owned land; Alternative L-II would require 5,000 acres of city-owned land; and
Alternative L-III would require 1,120 acres of city-owned land. The AWT alternatives would
all be placed on the existing 80-acre treatment plant site.
EFFLUENT QUALITY. Tables V-l and V-4 present effluent quality data. None of
the land treatment and AWT alternatives produce precisely the same effluent quality. All
alternatives except AWT-III produce an effluent quality which exceeds the pending discharge
requirements. AWT-III would meet the pending requirements which call for nitrification of
ammonia. As noted earlier, Boulder wished to evaluate alternatives that would provide a very
high degree of treatment even if not required to do so.
TREATMENT RELIABILITY. Alternative L-I would be moderately reliable due to the
fact that the irrigation system would not be directly controlled by the city. Alternative L-II
would have better reliability because the city would own and control operation of the
irrigation system. The reliability of both Alternatives L-I and L-II are affected by potential
63
-------
stormwater runoff during storms which exceed the design capacity of the surface runoff
collection system (10-year storm runoff). Alternative L-III would have good reliability but
would suffer from lower nitrogen removals in the winter. Alternative AWT-I is the most
reliable system since it uses combined biological and physical-chemical treatment. AWT-II and
AWT-III are less reliable than AWT-I since they depend on biological processes for nitrogen
removal.
IMPLEMENTATION. The land treatment alternatives would require more time to
implement due to the delays associated with major land purchases and obtaining the necessary
use permits and other approvals. It was concluded that 4.5 to 5.5 years would be required to
implement the land treatment alternatives, while 3 to 4 years would be required for the AWT
alternatives.
WATER RIGHTS. The water rights implications of the land treatment Alternatives L-I
and L-II were greater than for the AWT alternatives or L-III and may require court action.
ENVIRONMENTAL IMPACTS. In the Boulder area climate, fog formation is possible in
the vicinity of the storage reservoirs associated with the land treatment alternatives, with
resulting travel hazards on adjacent roads. The higher application rates associated with
Alternative L-II could cause fog over the entire irrigation site in spring and fall. The furnaces
associated with the AWT alternatives are potential sources of pollutants but are controllable.
No significant effects on soils were projected for any of the alternatives. Alternatives L-I
and L-II could benefit soil tilth and fertility. Some buildup of heavy metals may occur with
L-II, but not to toxic levels due to the calcarious nature of the soil.
Alternative L-I would have a potential for health risks since people would continue to
reside on the irrigation site. The storage reservoirs would provide a favorable environment for
insect vectors.
The land treatment alternatives would inundate 150 to 400 acres of productive
agricultural land in the storage reservoirs. The diversity of vegetation would be reduced by
Alternatives L-II and L-III. The AWT alternatives would not significantly affect vegetation.
Alternative L-I would displace only 3 to 4 families in the reservoir site, while Alternative
L-II would displace 75 families who would also lose both their source of employment and
their homes. A highly negative public reaction to the land treatment alternatives (particularly
L-II) was anticipated. It was also expected that people living adjacent to the treatment plant
site would oppose the major expansion associated with AWT-I and AWT-II.
Alternatives L-I and L-II would require relocation of a state highway.
RESOURCE COMMITMENTS. It is very difficult to generalize on the relative power
consumptions of land treatment and AWT. The estimated electrical energy requirements are
shown in table V-12. The power requirements for land treatment are composed of the
following:
• Pretreatment
• Those required to transport the wastewater to the storage facility (zero for
Alternatives L-I and L-II)
64
-------
Table V'-12.—Electrical resource commitments of alternatives
Alternative
L-l
L-ll
L-lll
AWT- 1
AWT- 1 1
AWT-III
Electrical energy
106 Kwh/year
8.6
19.0
6.7
19.0
13.5
9.0
Kwh/mg
1,122
2,479
874
2,479
1,761
1,174
• Distribution of the effluent to the irrigation system (very low for Boulder due to
flooding system used for irrigation and gravity flow to portions of the system)
• Return of collected surface runoff to irrigation system
• Power required to transport the treated effluent from its point of collection to the
discharge point.
ECONOMICS. Table V-13 summarizes the costs of each of the alternatives. Other related
economic factors are that Alternative L-II would reduce the tax base by 5,000 acres and
Alternative L-III by 1,120 acres. Crop values are not expected to change significantly with the
land treatment alternatives although crop diversity will be lessened.
CURRENT STATUS. EPA has indicated to the city that the cost of alternatives which
exceed the required degree of treatment would not be fully grant-eligible. Only the portion of
the costs required to meet discharge standards would be grant-eligible. The added economic
burden of providing higher degrees of treatment than required has apparently deterred
selection of land treatment alternatives and AWT-I and II. Had very high degrees of treatment
been required, the land treatment alternatives would have been more cost-effective under the
conditions in Boulder than the AWT alternatives.
Since this study was made, the nitrification requirement has been dropped (at least
temporarily) and the City of Boulder has conducted a more detailed facilities plan based on
meeting secondary standards (30 mg/I BOD and SS) by options such as infiltration-percolation,
land application (similar to L-2), activated sludge (either before or after the trickling filters),
lagoons, chemical coagulation, and mixed media filtration. Based on this study, the City
Council has approved a facilities plan based on lagoon treatment of the trickling filter effluent
with the option of adopting the infiltration-percolation approach should EPA rule it fully
grant-eligible.
65
-------
Table V-13.—Cost comparison summary
Alternative
L-l
L-ll
L-lll
AWT- 1
AWT- 1 1
AWT-III
Capital costs
$47,143,000
$38,811,000
$27,056,000
$46,156,000
$30,277,000
$17,707,000
0 & M costs3
$1,139,000
$1,037,000
$ 858,000
$2,474,000
$2,004,000
$1,232,000
Present worth
of all costs
$40,637,000
$35,099,000
$27,277,000
$53,334,000
$37,187,000
$21,752,000
aFor 1995 flows.
COST COMPARISON SUMMARY
The preceding example is a good illustration of the effect that local conditions can
have on the relative costs of AWT and land treatment. For high degrees of treatment, land
treatment offered economic savings over AWT in Boulder, Colorado. In order to make some
general observations on the relative economic merits of AWT and land treatment, generalized
cost curves were prepared. (For detailed estimates, the EPA document, Cost of Land
Application Systems, should be used.) The following curves were prepared to reflect the
general nature of the effects of conditions ranging from relatively favorable to relatively
unfavorable on land treatment costs. Table V-14 summarizes the basic assumptions made.
These curves are for sprinkler systems since the flooding system is not as widely applicable.
There are obvious exceptions to any set of generalized conditions, and this is true for the
conditions in table V-14. For example, at Boulder there was one alternative where an existing
irrigation system could be used with virtually no modification so that the costs of the
irrigation system and site preparation would be reduced even further below those shown for
favorable conditions. However, these are unusually favorable circumstances. The total of $960
per acre shown for very favorable conditions (table V-14) is approximately the costs
experienced at Muskegon, Michigan, where conditions are favorable (flat, sandy soils, center
pivot irrigation). There will be cases where conditions may be even more favorable than
shown in table V-14 as very favorable, and also even more unfavorable than those shown as
unfavorable (i.e., subsurface drainage costs for the high-rate system in Boulder were
$l,458/acre as opposed to the $1,000 shown as unfavorable in table V-14). However, the
range of conditions shown in table V-14 does reflect a range of costs that spans circumstances
which would be described as favorable to unfavorable in many cases.
Tables V-15, V-16, and V-17 show the development of cost estimates for various capacity
systems under the range of conditions described in table V-14. These costs do not include
pretreatment costs, the costs to deliver wastewater to the irrigation site, or revenue from (or
costs to dispose of) crops. The purpose of this section is to compare costs of land treatment
with AWT techniques; thus, inclusion of costs to transport wastewater to the land treatment
66
-------
Table V-14.—Examples of impact of conditions on land treatment
costs per acre (1974)
Item
Land preparation
Surface runoff
control
Subsurface drainage
Irrigation system
Pumping station
and distribution
main
Laterals and
sprinklers
Land costs
Relocation costs
Totals
Unfavorable
conditions
Extensive earthwork
and clearing— $350
Rolling topography
and intense storms-
Si, 000
Extensive underdrain
system needed-$ 1,000
$ 700
Solid set-$2,000
$2,000
$ 50
$7,100
Moderately favorable
conditions
$ 150
$ 500
$ 400
$ 500
Solid set-$1,400
$1,000
$ 30
$4,030
Very favorable
conditions
Little earthwork and
clearing— $50
Relatively level site and
moderate rain-$200
None required
$ 400
Center pivot— $300
$ 500
$ 10
$1,460
site (which are totally site specific in any case) would be unfavorably biased against land
treatment. As noted earlier, the irrigated areal requirements can vary from 100 to 500
acres/mg. Because total costs are related to the area required, costs are shown for a range of
areal requirements for each flow condition. It was assumed that total areal requirements were
130 percent of the irrigated area to provide for buffer zones and to account for unusable
areas within the irrigation site. Land costs were assumed to be $500, $1,000, and $2,000 per
acre for the very favorable, moderately favorable, and unfavorable conditions, respectively.
Storage for 5 months flow was assumed. Engineering, legal, and contingency costs were
applied to the nonland costs only. Capital costs were amortized at 7 percent for 20 years.
In order to span a range of AWT alternatives, two levels of treatment were assumed.
"AWT-minimum" would consist of coagulation, sedimentation, and filtration. This would
reduce phosphorus, BOD, suspended solids, and coliform to levels comparable to that achieved
by a land treatment system where nitrogen removal is not of concern.
"AWT-maximum" adds biological nitrogen removal and activated carbon adsorption and
regeneration to the AWT-minimum approach. As with land treatment, secondary treatment and
raw sewage transport costs are not included. It was assumed that the chemical sludges would
be lime sludges which would be dewatered and recalcined. It is probable that AWT costs can
be reduced if dewatering and burial of lime sludges near the plant site are practical for a
67
-------
given locale. Recalcining costs are included, however, to ensure an adequately high AWT cost
estimate. AWT costs are also expressed in 1974 cost levels. Table V-18 summarizes the AWT
cost estimates which include costs for engineering and legal fees, and contingencies.
The AWT costs and land treatment costs are plotted in figures V-4, V-5, and V-6.
Although such generalized costs have limitations, they do indicate general trends in the
relative costs of AWT and land treatment. Increases in the degree of treatment required and
decreases in plant size improve the competitive economic position of land treatment with
conventional AWT processes.
68
-------
Table V-15.—Illustrative estimated costs for
a spray irrigation system—very favorable conditions
Capital costs
Total land purchase'3
Land preparation0
Surface runoff control0
Subsurface drainage0
Irrigation system0
Relocation costs
Storage lagoon
Subtotal
Costs, thousands of dollars
1 mgd
100a
65.0
5.0
20.0
0
70.0
1.3
180.0
341.3
200
130.0
10.0
40.0
0
140.0
2.6
180.0
502.6
500
325.0
25.0
100.0
0
350.0
6.5
180.0
986.5
10 mgd
100
650
50
200
0
700
13
900
2,513
200
1,300
100
400
0
1,400
26
900
4,126
500
3,250
250
1,000
0
3,500
65
900
8,965
50 mgd
100
3,250
250
1,000
0
3,500
65
3,000
11,065
200
6,500
500
2,000
0
7,000
130
3,000
19,130
500
16,250
1,250
5,000
0
17,500
325
3,000
48,325
Plus 25% for legal,
engr., contingencies (non land costs only)
Total capital costs
Annual costs
Amortization (20 yrs @ 7%)
Labor, operating
Power
Maintenance
Total annual costs
Total, rf/1,000 gals
410
38.7
10
7
25
80.7
22.1
595
56.1
13
7
30
106.1
29.0
1,152
108.6
18
9
40
175.6
48.1
2,978
280.9
20
50
160
510.9
14.0
4,832
455.8
30
60
200
745.8
20.4
10,394
980
40
70
300
1,390
38.0
13,019
1,228
75
240
480
2,023
11.1
22,288
2,102
100
270
550
3,022
16.5
50,094
4,725
140
300
750
5,915
32.4
Note: Costs not included in the above: secondary treatment, facilities to pump and transport wastewater to irrigation
site, disposal of crop (cost or revenue).
Irrigated land area requirements, acres/mg.
^Total land purchased =130 percent x irrigated land ($500/acre used).
GApplies to irrigated land only.
69
-------
Table V-16.—Illustrative estimated costs for
a spray irrigation system—moderately favorable conditions
Capital costs
Total land purchase"
Land preparation0
Surface runoff control0
Subsurface drainage0
Irrigation system0
Relocation costs
Storage lagoon
Subtotal
Cost, thousands of dollars
1 mgd
100a
130
15
50
40
195
3
200
633
200
260
30
100
80
390
6
200
1,066
500
650
75
250
200
975
15
200
2,365
10 mgd
100
1,300
150
500
400
1,950
30
950
5,280
200
2,600
300
1,000
800
3,900
60
950
9,610
500
6,500
750
2,500
2,000
9,750
150
950
22,600
50 mgd
100
6,500
750
2,500
2,000
9,750
150
3,200
24,850
200
13,000
1,500
5,000
4,000
19,500
300
3,200
46,500
500
32,500
3,750
12,500
10,000
48,750
750
3,200
111,450
Plus 25% for legal,
engr., contingencies (non land costs only)
Total capital costs
Annual costs
Amortization (20 yrs @ 7%)
Labor, operating
Power
Maintenance
Total annual costs
Total, d/1,000 gals
791
74
10
7
20
111
30.3
1,332
126
13
7
25
171
46.9
2,956
279
18
9
30
336
92.0
6,600
623
20
50
130
823
22.5
12,012
1,134
30
60
160
1,384
37.9
28,250
2,665
40
70
240
3,015
82.6
31,062
2,931
75
240
380
3,626
19.8
56,187
5,300
100
270
450
6,120
33.6
139,312
13,142
140
300
600
14,182
77.7
Note: Costs not included in the above: secondary treatment, facilities to pump and transport wastewater to irrigation
site, disposal of crop (cost or revenue).
Irrigated land area requirements, acres/mg.
'•'Total land purchased = 130 percent x irrigated land.
cApplies to irrigated land only.
70
-------
Table V-17.—Illustrative estimated costs for
a spray irrigation system—unfavorable conditions
Capital costs
Total land purchase^
Land preparation0
Surface runoff control0
Subsurface drainage0
Irrigation system0
Relocation costs
Storage lagoon
Subtotal
Costs, thousands of dollars
1 mgd
100a
260
35
100
100
270
5
220
990
200
520
70
200
200
540
10
220
1,760
500
1,300
175
500
500
1,350
25
220
4,070
10 mgd
100
2,600
350
1,000
1,000
2,700
50
1,050
8,750
200
5,200
700
2,000
2,000
5,400
100
1,050
16,450
500
13,000
1,750
5,000
5,000
1 3,500
250
1,050
39,550
50 mgd
100
13,000
1,750
5,000
5,000
13,500
250
3,500
42,000
200
26,000
3,500
10,000
10,000
27,000
500
3,500
80,500
500
65,000
8,750
25,000
25,000
67,500
1,250
3,500
196,000
Plus 25% for legal,
engr., contingencies (non land costs only)
Total capital costs
Annual costs
Amortization (20 yrs @ 7%)
Labor, operating
Power
Maintenance
Total annual costs
Total, d/l,000 gals
1,238
116
10
7
20
153
41.9
2,200
208
13
7
25
253
69.3
5,088
479
18
9
30
536
146.4
10,938
1,032
20
50
130
1,232
33.9
20,563
1,939
30
60
160
2,189
59.9
49,438
4,664
40
70
240
5,014
137.3
52,500
4,952
75
240
380
5,647
30.9
100,625
9,492
100
270
450
10,312
56.4
245,000
23,113
140
300
600
24,153
132.3
Note: Costs not included in the above: secondary treatment, facilities to pump and transport wastewater to irrigation
site, disposal of crop (cost or revenue).
Irrigated land area requirements, acres/mg.
'•'Total land purchased = 130 percent x irrigated land.
cApplies to irrigated land only.
71
-------
Table V-18.—XW7 system costs
1 mgd
Capital3
0 & Mb
10 mgd
Capital
0 & M
50 mgd
Capital
O & M
AWT minimum
Coagulation-sedimentation
Filtration
Sludge handling
Total
rf/1,000 galsb
0.23
0.32
1.80
2.35
0.016
0.026
0.040
0.082
82.9
0.65
1.30
3.20
5.15
0.11
0.12
0.17
0.40
24,2
2.4
3.0
6.5
11.9
0.38
0.34
0.50
1.22
12.8
AWT maximum
Coagulation-sedimentation
Filtration
Sludge handling
Nitrif.-denitrif.
Act. carbon
Total
il 1,000 gals
0.23
0.32
1.80
0.75
1.00
4.10
0.016
0.026
0.040
0.090
0.020
0.192
158.0
0.65
1.30
3.20
3.00
3.50
11.65
0.11
0.12
0.17
0.34
0.07
0.81
52.2
2.4
3.0
6.5
11.5
12.0
35.4
0.38
0.34
0.50
1.20
0.30
2.72
33.1
aS x 10".
b$ x 106 per yeai.
cCapital costs amortized, 20 years at
7%.
72
-------
150
4 5 6 7 8 9 10
CAPACITY, mgd
15
20
30 40 50
Figure V-4. AWT cost comparison-very favorable conditions for land treatment.
73
-------
150
4 5 6 7 8 9 10
CAPACITY, mgd
15
20
30
40 50
Figure V-5. AWT cost comparison-moderately favorable conditions for land treatment.
74
-------
150
5 6 7 8 9 10
CAPACITY, mgd
15 20
30 40 50
Figure V-6. AWT cost comparison—unfavorable conditions for land treatment.
75
-------
REFERENCES
1R. H. Sullivan, M. M. Cohn, and S. S. Baxter, Survey of Facilities Using Land
Application of Wastewater, U. S. Environmental Protection Agency, EPA-430/9-73-066, July
1973.
2 Walter N. Mack, research program conducted by Dr. Mack, Institute of Water Research,
Michigan State University.
3 Walter N. Mack, Institute of Water Research, unpublished data, Michigan State
University, 1969.
4W. N. Mack, W. L. Mallmann, H. H. Bloom, and B. J. Krueger, "Isolation of Enteric
Viruses and Salmonella from Sewage. I. Comparison of Coliform and Enterococci Incidence to
the Isolation of Viruses," Sewage and Industrial Wastes, 30, No. 957, 1958.
5W. N. Mack, J. R. Frey, B. J. Riegle, and W. H. Mallmann, "Enterovirus Removal by
Activated Sludge Treatment," /. Water Pollut. Cont. Fed., 34, 1133, 1962.
6W. N. Mack, "Poliovirus in a Water Supply," /. Amer. Water Works Ass., 65, 347,
1973.
7Standard Methods, Water and Wastewater, American Public Health Association, 13th
edition, New York, 1973.
8 A. A. Anderson, "Developmental Work on the Anderson Sampler," DPGRR Report 108,
Dugway Proving Ground, Utah, 1956.
9H. M. Decker and M. E. Wilson, "A Silt Sampler for Collecting Airborne
Microorganisms," Applied Microbiology, 2, No. 267, 1954.
10W. B. Cown, T. W. Kathley, and Z. L. Fincher, "The Critical-Orifice Liquid Impinger
as a Sampler for Bacterial Aerosols," Applied Microbiology, 5, No. 119, 1957.
11C. D. McNabb, Jr. and D. P. Tierney, "Growth and Mineral Accumulation of
Submersed Vascular Hydrophytes in Pleioeutrophic Environs," Technical Report No. 26,
Institute of Water Research, Michigan State University, 1972.
12 David C. Wiggert, research program being conducted by Dr. Wiggert, Department of
Civil Engineering, Michigan State University.
77
-------
13 David C. Wiggert, "Two-Dimensional Finite Element Modeling of Transient Flow in
Regional Aquifer Systems," Technical Report No. 41, Institute of Water Research, Michigan
State University, August 1974.
14Milo B. Tesar, research program being conducted by Dr. Tesar, Department of Crop
and Soil Science, Michigan State University.
15 A. R. Overman, "Research Experience in Florida," Proceedings, Workshop on Land
Renovation of Municipal Effluent in Florida, University of Florida, 1972.
16G. W. Burton, "Wastes—Forages—Animals—Man," Proceedings, Workshop on Land
Renovation of Municipal Effluent and Sludge in Florida, University of Florida, 1973.
17W. E. Adams, M. Stelly, H. D. Morris, and C. B. Elkins, "A Comparison of Coastal
and Common Bermuda Grasses in the Piedmont Region," Agronomy Journal, 59, 281, 1967.
18W. L. Parks and W. B. Fisher, Jr., "Influence of Soil Temperature and Nitrogen on
Rye Grass Growth and Chemical Composition," Soil Science Society of America, Proceedings,
22, 257, 1958.
19J. G. A. Fiskell and R. Ballard, "Prediction of Phosphate Retention and Mobility in
Florida Soils," Proceedings, Workshop on Land Renovation of Municipal Effluent and Sludge
in Florida, University of Florida, 1973.
20 A. R. Overman and H. M. West, "Measurement of Unsaturated Hydraulic Conductivity
by the Constant Outflow Method," Transactions of American Society of Agricultural
Engineers, 15, 110, 1972.
2' "Proposed Rules and Regulations for Reclaimed Wastes," Arizona State Department of
Health, Phoenix, Arizona, 1972.
22J. A. Replogle, "Critical-Depth Flumes for Determining Flow in Canals and Natural
Channels," Transactions of American Society of Agricultural Engineers, 14, 428, 1971.
23H. Bouwer, R. C. Rice, E. D. Escarcega, and M. S. Riggs, Renovating Secondary
Sewage by Ground-water Recharge with Infiltration Basins, U. S. Environmental Protection
Agency, Water Pollution Control Research Series, Project No. 16060 DRV, U. S. Government
Printing Office: Washington, D. C., March 1972.
24H. Bouwer, "Groundwater Recharge Design for Renovating Wastewater," /. Sanit. Eng.
Div., Am. Soc. Civil Eng. Proceedings, 96, 59, 1970.
25R. C. Rice, "Soil Clogging During Infiltration with Secondary Sewage Effluent," /.
Water Pollut. Cont. Fed., (in press).
26J. C. Lance and F. D. Whisler, "Nitrogen Balance in Soil Columns Intermittently
Flooded with Sewage Water," /. of Environmental Quality, 1, 180, 1972.
27J. C. Lance, F. D. Whisler, and H. Bouwer, "Oxygen Utilization in Soils Flooded with
Sewage Water," /. of Environmental Quality, (in press).
28H. Bouwer, "Salt Balance, Irrigation Efficiency, and Drainage Design," /. of Irrigation
and Drainage Division, Am. Soc. of Civil Eng. Proceedings, 95, 153, 1969.
78
-------
29W. G. Matlock, P. R. Davis, and R. L. Roth, "Sewage Effluent Pollution of a
Ground-water Aquifer," paper presented before the American Society of Agricultural Engineers,
Winter Meeting, Chicago, Illinois, December 1972.
30D. M. Wells, "Groundwater Recharge with Treated Municipal Effluent," Proceedings of
the Conference on Municipal Sewage Effluent for Irrigation, ed. C. W. Wilson and F. E.
Beckett, Louisiana Polytechnic Institute, Ruston, Louisiana, 1968.
3' "Water Quality Criteria," Environmental Protection Agency, Report of National
Technical Advisory Committee to Secretary of the Interior, Washington, D. C., 1968.
32J. L. Buxton, Determination of a Cost for Reclaiming Sewage Effluent by
Groundwater Recharge in Phoenix, Arizona, unpublished master's thesis, College of Engineering
Science, Arizona State University, Tempe, Arizona, 1968.
33W. E. Sopper and L. T. Kardos (eds.), "Vegetation Responses to Irrigation with
Treated Municipal Wastewater," Recycling Treated Municipal Wastewater and Sludge Through
Forest and Cropland, The Pennsylvania State University Press: University Park, 1973.
34W. E. Sopper, "Crop Selection and Management Alternatives—Perennials," Proceedings
of the Joint Recycling Municipal Sludges and Effluents on Land, National Associations of
State Universities and Land Grant Colleges, Champaign, Illinois, July 9-13, 1973.
35W. K. Murphey, R. L. Brisbin, W. J. Young, and B. E. Cutter, "Anatomical and
Physical Properties of Red Oak and Red Pine Irrigated with Municipal Wastewater," Recycling
Treated Municipal Wastewater and Sludge Through Forest and Cropland, ed. W. E. Sopper and
L. T. Kardos, The Pennsylvania State University Press: University Park, 1973.
36G. W. Wood, D. W. Simpson, and R. L. Dressier, "Effects of Spray Irrigation of
Forests with Chlorinated Sewage Effluent on Deer and Rabbits," Recycling Treated Municipal
Wastewater and Sludge Through Forest and Cropland, ed. W. E. Sopper and L. T. Kardos,
The Pennsylvania State University Press: University Park, 1973.
79
U S GOVERNMENT PRINTING OFFICE 1977-757-056/641! Region No. 5-11
------- |