WATER POLLUTION CONTROL RESEARCH SERIES • I3O3OELY 6/71-IO
REC -R2-7I-IO
DWR NO. 174—13
BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEY, CALIFORNIA
TECHNIQUES TO REDUCE NITROGEN IN
DRAINAGE EFFLUENT DURING TRANSPORT
ENVIRONMENTAL PROTECTION AGENCY0RESEARCH AND MONITORING
UNITED STATES BUREAU OF RECLAMATION
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BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEY, CALIFORNIA
The Bio-Engineering Aspects of Agricultural Drainage
reports describe the results of a unique interagency
study of the occurrence of nitrogen and nitrogen removal
treatment of subsurface agricultural wastewaters of the
San Joaquin Valley, California.
The three principal agencies involved in the study are
the Water Quality Office of the Environmental Protection
Agency, the U. S. Bureau of Reclamation, and the
California Department of Water Resources.
Inquiries pertaining to the Bio-Engineering Aspects of
Agricultural Drainage reports should be directed to
the author agency, but may be directed to any one of
the three principal agencies.
THE REPORTS
It is planned that a series of 12 reports will be
issued describing the results of the interagency study.
There will be a summary report covering all phases of
the study.
A group of four reports will be prepared on the phase
of the study related to predictions of subsurface
agricultural wastewater quality — one report by each
of the three agencies, and a summary of the three
reports.
Another group of five reports has been prepared on the
treatment methods studied and on the biostimulatory
testing of the treatment plant effluent. There are
four basic reports and a summary of the reports. This
report, "REMOVAL OF NZPROGEN FROM TILE DRAINAGE", is
the summary report.
The other three planned reports will cover (l) techniques
to reduce nitrogen during transport or storage,
(2) possibilities for reducing nitrogen on the farm,
and (3) desalination of subsurface agricultural
wastewaters.
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BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEY, CALIFORNIA
TECHNIQUES TO REDUCE NITROGEN IN
DRAINAGE EFFLUENT DURING TRANSPORT
Prepared by the
United States Bureau of Reclamation
Region 2
The agricultural drainage study was conducted under the direction
of:
Robert J. Pafford, Jr., Regional Director, Region 2
UNITED STATES BUREAU OF RECLAMATION
2800 Cottage Way, Sacramento, California 95825
Paul DeFalco, Jr., Regional Director, Pacific Southwest Region
WATER QUALITY OFFICE, ENVIRONMENTAL PROTECTION AGENCY
760 Market Street, San Francisco, California 94102
John R. Teerink, Deputy Director
CALIFORNIA DEPARTMENT OF WATER RESOURCES
1416 Ninth Street, Sacramento, California 95814
June 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 60 cents
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REVIEW NOTICE
This report has been reviewed by
the Water Quality Office, Environ-
mental Protection Agency and the
California Department of Water
Resources, and has been approved
for publication. Approval does
not signify that the contents
necessarily reflect the views and
policies of the Water Quality Office,
Environmental Protection Agency, or
the California Department of Water
Resources.
The mention of trade names or
commercial products does not
constitute endorsement or recom-
mendation for use by either of the
two federal agencies or the Cali-
fornia Department of Water Resources.
ii
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ABSTRACT
Three methods to remove nitrates from the agricultural drainage
water from the San Luis Service Area were investigated. One
method was a theoretical evaluation of nitrate removal by algae
during the transport of the drainage water in the San Luis Canal
or during storage in the Kesterson Reservoir. The other methods
were designed to promote anaerobic bacterial denitrification in a
continuous flow of drainage water. One method used barley straw
and the other water grass grown in shallow ponds as the carbon
energy source. The barley straw was placed in a trench about 10
feet deep and the nitrate removal rate determined under various
flow and detention rates. The water grass was grown in ponds
under a continuous flow of water of about 4 to 6 inches depth.
Under optimum conditions both methods reduced the nitrate -N con-
centration of the drainage water from a maximum of about 30 mg/1 to
less than 2 mg/1. The cost of nitrogen removal by the shallow grass
plot systems, the most economical and feasible of these methods,
was estimated to be $6.50 per acre foot or $20.00 per million
gallons.
111
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BACKGROUND
This report is one of a series which presents the findings of in-
tensive interagency investigations of practical means to control
the nitrate concentration in subsurface agricultural wastewater
prior to its discharge into other water. The primary participants
in the program are the Water Quality Office of the Environmental
Protection Agency, the United States Bureau of Reclamation, and the
California Department of Water Resources, but several other agencies
also are cooperating in the program. These three agencies initiated
the program because they are responsible for providing a system for
disposing of subsurface agricultural wastewater from the San Joaquin
Valley of California and protecting water quality in California'a
water bodies. Other agencies cooperated in the program by provid-
ing particular knowledge pertaining to specific parts of the overall
task.
The ultimate need to provide subsurface drainage for large areas of
agricultural land in the western and southern San Joaquin Valley has
been recognized for some time. In 1954, the Bureau of Reclamation
included a drain in its feasibility report of the San Luis Unit.
In 1957, the California Department of Water Resources initiated
an investigation to assess the extent of salinity and high ground
water problems and to develop plans for drainage and export facili-
ties. The Burns-Porter Act, in 1960, authorized San Joaquin Valley
drainage facilities as part of the State Water Facilities.
The authorizing legislation for the San Luis Unit of the Bureau of
Reclamation's Central Valley Project, Public Law 86-488, passed in
June 1960, included drainage facilities to serve project lands.
This Act required that the Secretary of Interior either provide for
constructing the San Luis Drain to the Delta or receive satisfactory
assurance that the State of California would provide a master drain
for the San Joaquin Valley that would adequately serve the San Luis
Unit.
Investigations by the Bureau of Reclamation and the Department of
Water Resources revealed that serious drainage problems already
exist and that areas requiring subsurface drainage would probably
exceed 1,000,000 acres by the year 2020. Disposal of the drainage
into the Sacramento-San Joaquin Delta near Antioch, California, was
found to be the least costly alternative plan.
Preliminary data indicated the drainage water would be relatively
high in nitrogen. The then Federal Water Quality Administration
conducted a study to determine the effect of discharging such
drainage water on the quality of water in the San Francisco Bay and
Delta. Upon completion of this study in 1967, the Administration's
report concluded that the nitrogen content of untreated drainage
waters could have significant adverse effects upon the fish and
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recreation values of the receiving waters. The report recommended
a three-year research program to establish the economical feasibil-
ity of nitrate-nitrogen removal.
As a consequence, the three agencies formed the Interagency
Agricultural Wastewater Study Group and developed a three-year
cooperative research program which assigned specific areas of
responsibility to each of the agencies. The scope of the investi-
gation included an inventory of nitrogen conditions in the potential
drainage areas, possible control of nitrates at the source, predic-
tion of drainage quality, changes in nitrogen in transit, and
methods of nitrogen removal from drain waters including biological-
chemical processes and desalination.
VI
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Introduction 5
IV Objectives 7
V Methods, Materials and Results 9
Nutrient Removal by Algae Growth Within the Transport
System 9
Utilizing San Luis Canal 9
Utilizing Kesterson Reservoir 10
Nutrient Removal by Field Denitrification Processes 11
Sample Collection and Analytical Techniques 13
Deep Trench Study 13
Methods and Materials 14
Results 14
Detention Time 20
Temperature 20
Energy Source Requirements 20
Electrical Conductivity 21
Grass Plot Study 22
Methods and Materials 22
Results 23
Dissolved Oxygen 27
Temperature 29
Percolating Water Studies 29
VI Cost Analyses 35
VII Discussion 41
VIII Acknowledgements 45
IX References 47
VI1
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FIGURES
Number Page
1 Plans of Denitrification Plots 12
2 Deep Trench - Nitrate Concentrations and Temperatures 15
3 Deep Trench - Dissolved Oxygen 16
4 Grass Plot - Nitrate Concentration - October 1968 -
September 1969 24
5 Grass Plot - Nitrate Concentration - October 1969 -
April 1970 25
6 Deep Trench Nitrate Reduction Ponds 39
7 Shallow Nitrate Reduction Ponds 40
Vlll
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TABLES
Number Page
1 Chemical Analysis of Supply Water 13
2 Nitrate Concentration, Dissolved Oxygen and Detention
Time of Water in Deep Pond Studies 15
3 The Concentration of the Various Nitrogen Forms, pH,
Electrical Conductivity and Temperature of the Supply
and Discharge Water at Various Times During the Deep
Trench Experiment 20
4 Flow Rates, Detention Times and Straw Requirements of
Deep Pond 22
5 Calculated Inflow Rates and Theoretical Detention
Times of the Various Checks in the Grass Plot 26
6 Algae Count at Several Sampling Sites in Grass Plots -
February 26, 1970 27
7 Concentration of Various Nitrogen Forms, Temperature,
pH and Electrical Conductivity at Four Locations in the
Plot 28
8 The Nitrate -N Concentration of the Soil Extract from
Several Depths Below the Grass Plot 30
9 Quantity of Surface Flow, NC-3-N Concentration and Deep
Percolation in the Grass Plot for an Average 24-hour
Period 31
10 Estimated Cost for Removal of Nitrogen by Deep Pond
Method 37
11 Estimated Costs for Removal of Nitrogen by Shallow
Grass Plot Method 38
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SECTION I
CONCLUSIONS
1 - The two methods, deep trench and the shallow grass ponds,
investigated at the San Luis Wasteway are technically feasible
and capable of removing nitrates to varying degrees.
2 - The shallow grass pond method, except for a one - or - two month
period in the late fall or early winter, was more efficient than
the deep trench methods.
3 - The shallow grass pond method offers the potential for costs
which are substantially lower than other nitrogen removal
treatment processes studied by the Interagency Group, if it
can be demonstrated that sustained operations, under field
conditions, will yield the desired qualities of effluent.
4 - The cost of treating the projected tile drainage effluent from
the San Luis area by the shallow grass pond method, based on
information developed in this study, would be approximately
$20 per million gallons or $6.50 per acre foot.
5 - Further investigations are required before a full-scale
operation of this method should be employed.
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SECTION II
RECOMMENDATIONS
The investigations to date indicate that the shallow pond method
has a potential for nitrate removal at a reasonable cost therefore
it is recommended that further studies be conducted on this method
and variations of this method to gain additional data on optimum
operating conditions and design criteria. When the San Luis Drain
and the Kesterson Reservoir go into operation it is further
recommended that a full scale plot be set up in the Reservoir.
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SECTION III
INTRODUCTION
The San Luis Canal-California Aqueduct, a joint Federal and State
of California water operation, will import large quantities of
water into the westside of the central and southern San Joaquin
Valley. This importation of water will permit more intensive
surface irrigation of the lands and will reduce the amount of
pumping from the groundwater. These factors combined with the
relatively slowly permeable and stratified soils will promote the
formation of saline, high ground-water in much of the area. A
system of on-farm subsurface drains will be required to maintain
the groundwater at an acceptable level if land productivity is to
be maintained.
To provide an outlet for the farm drain effluent from the San Luis
Service Area the United States Bureau of Reclamation has started
construction of the San Luis Drain. During the first stage of
operation this Drain will terminate at the Kesterson Reservoir.
Ultimately the Drain is designed to discharge into the Sacramento-
San Joaquin Delta near Antioch. When conditions warrant, the State
of California plans to construct a drainage canal to serve the
remainder of the Valley which is also planned to discharge into
the Delta. The water collected from these subsurface drains and
carried by the drainage canals is expected to contain relatively
high concentrations of nitrate-nitrogen. Recent studies (1,2)
suggest levels of approximately 20 milligrams per liter (NOj-N)
and this may have a potential for causing undesirable algae
blooms in the receiving water of the Delta.
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SECTION IV
OBJECTIVES
An objective of the project was to determine changes in N-forras
during transit to treatment systems. One of the original plans
was to evaluate the change in N in drainage waters as they moved
through an operating canal system. A search was made in areas
which have climatological, soil and irrigation conditions somewhat
similar to those in the San Joaquin Valley. A check of the nitrogen
concentration in the drainage systems in the Wellton-Mohawk, Gila
and Imperial Valley service areas, did not reveal any systems which
had quantities of nitrogen sufficiently high to give any significant
evaluation.
To satisfactorily duplicate the anticipated nitrate levels of the
San Luis Drain water would involve prohibitive costs for addition
of nitrates to a system of similar size. The reduction to experi-
mental scale would result in smaller costs for nitrate addition;
however, the biological environment might then be poorly duplicated
and the results would be of questionable value. Consequently
measurements of this type, were postponed until sections of the
San Luis Drain are completed. At that time, any changes in nitrogen
in the drainage water from the San Luis service area during trans-
port from Westlands Water District to the Kesterson Reservoir can
be monitored.
Therefore, in lieu of the study of changes in transport, the emphasis
of this project was shifted to determine what changes could be
effected in the drainage waters by using facilities similar to the
designed transport and storage system facilities and the use of
agricultural waste products.
Two separate studies were made to accomplish these objectives. One
was a plan to combine nutrient removal by promoting algae growth
within the transport system, the San Luis Drain and the Kesterson
Reservoir. This method of treatment was proposed by a team from
the Firebaugh Waste Water Treatment Center (3). The evaluation
of this proposal was based primarily on theoretical calculations
rather than on an experimental model. The second study was concerned
with nitrate removal in the transportation system by the denitrifi-
cation process. This later study was in two phases, one utilized
an elongated,relatively deep pond somewhat similar to a section of
the San Luis Drain and the other a broad relatively shallow pond,
similar to a cell of Kesterson Reservoir.
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SECTION V
METHODS, MATERIALS AND RESULTS
This section describes the method and materials used in the study
of techniques to reduce nitrogen concentrations in drainage effluent
during transport or storage and discusses the result of the findings
of the investigations.
Nutrient Removal by Algal Growth within the Transport System
A study was prepared by Joel C. Goldman, James F. Arthur and others
(3) on the possibility of using the San Luis Drainage transport and
storage systems as a means to remove nutrients by the growth and
harvesting of algae in these facilities. The plan was proposed on
the premise that, under favorable environmental conditions, there
will be a natural growth of algae within the San Luis Drain and
Kesterson Reservoir, and that if, maximum algal growth was promoted
it could serve as a dual treatment - transport system. The study
was based primarily on basic assumptions and theoretical calculations
rather than on an experimental model.
Some of the criteria, particularly the projected flow of the San
Luis Drain and the size of Kesterson Reservoir have been changed
since the report was published, however, the basic theories, cal-
culations and conclusions in the study remain valid.
Calculations in the study indicated that the biomass required to
remove 90 percent of the estimated 25 mg/1 of nitrogen in the
drainage water would be 280 mg/1. It was postulated that a portion
of this quantity that could be grown in the Drain or the Reservoir
would reduce the land requirements for nutrient removal in the
treatment facilities thereby reducing the total nitrogen removal
costs. The study suggested that any action which could reduce the
acreage requirements in the Antioch area where land values are high
would be especially effective in reducing the overall project costs.
Utilizing the San Luis Drain
The studies indicated that the actual algal concentrations that will
be in the Drain are almost impossible to predict. When flow in the
San Luis Drain reaches its projected capacity it will have a surface
area of about 770 acres and a mean detention time of 6.3 days.
Algal cells will multiply rapidly, doubling about \ to 1 times per
day, thus there would probably be 4 or 5 doublings during transit.
Based on Dr. William Oswald's calculations and his most conservative
estimate of an original concentration of 1 mg/1 of algae and 4
doublings during transit to the Delta, then 16 mg/1 of algae would
be present at discharge. His less conservative estimate assumed
that the water started with 2 mg/1 of algae and there were 5 dou-
blings, then the final concentration would be 64 mg/1. Theoretically,
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based upon Dr. Oswald's calculations, the Drain has the capability
of supporting about 100 mg/1 of algae considering light limitations
only. Shallow ponding would be required to attain any further
increment of growth.
An approximation of the amount of nitrogen removed from the drain-
age water through the growth of the algae can be calculated by
making several assumptions:
1. Final algal concentration - 16 to 64 mg/1.
2. Nitrogen content of algal cells * 8-10 percent (use 8 percent)
3. Total nitrogen concentration in drainage water - 20-25 mg/1
(use 25 mg/1)
Thus the amount of nitrogen removed from drainage water and con-
verted into algal cell material can be calculated as follows:
16 mg/1 X 0.08 - 1.28 mg/1 (minimum estimate)
64 mg/1 X 0.08 - 5.12 mg/1 (maximum estimate)
or approximately:
1.28 X 100 - 5 percent (minimum estimate)
2!
100 « 20 percent (maximum estimate)
of the incoming nitrogen will be removed.
Since the amount of nitrogen removed will be directly proportional
to the concentration level of algae, nitrogen removal could be
increased by increased algal growth in the Drain. Methods to gain
increased growth would be to seed the Drain to get as high an
initial algal concentration as practical and then encourage as many
doublings as possible to occur during transit. Doublings could be
increased by modifying the Drain to create greater turbulence and
effective surface area by placing baffles in the Drain, aerating or
adding gases.
Utilizing Kesterson Reservoir
The study points out that the Kesterson Reservoir, an integral part
of the Drain system, could be utilized as a combined reservoir and
algae growth treatment plant. If the algae growth system was designed
for the optimum operating depth and a storage capacity depth of two
feet, the system would have the capability for essentially 100
percent treatment and still serve as an emergency storage reservoir.
10
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This system could be designed to minimize the power required for
mixing by taking advantage of the natural land slope to the north.
The design would entail a series of equally spaced channels running
along the length of the reservoir in the direction of the slope.
If it was necessary, pumps could be used to produce the required
initial mixing velocities. Any desired detention time could be
maintained by recirculating a portion of the effluent.
Research at Firebaugh indicates that both the "bacterial denitrifi-
cation" and the algae "growth and harvest" are technically feasible,
therefore, a combination of the two systems in a series type opera-
tion might give the best results. The algae growth and harvest
could take place in the Drain and Kesterson Reservoir followed by
anaerobic filters for final treatment.
Nutrient Removal by Field Denitrification Processes
The denitrification studies were based upon the principle that in
the presence of an adequate concentration of a degradable organic
material and restricted aeration bacteria will utilize the available
dissolved oxygen. Then, in the absence or near absence of oxygen,
denitrification is accomplished by facultative anaerobic bacteria
which are capable of using NO? in place of oxygen as a hydrogen
acceptor. The reactions which take place in this reduction process
are subject to a certain amount of controversy and speculation.
Nightingale (4) suggests a basic simplified multi-step reaction
pathway as follows:
„ 0~ ^ N-OH N ^ N
N - 0 + 2H-»N + 2H20 6H » + 2H20—« 0+H20 2H ill + H20
55 0 *0 "" N-OH N " """ N
Nitrate Nitrite Hyponitrite Nitrous Oxide Nitrogen Gas
The denitrification studies were carried out in two phases. One,
at the Firebaugh Center, had the main responsibility for anaerobic
denitrification with methanol. The other, conducted near the San
Luis Wasteway, main interest was denitrification with natural
carbon sources. In the latter projects, barley straw was used as
the carbon energy source in the deep trench study and water grass
grown in place was the source in the shallow pond study.
The plots were set up on Bureau of Reclamation owned land near the
San Luis Wasteway approximately 5 miles northwest of Los Banos.
The soils in the area are classified as Orestimba clay loam (5).
These soils are developed on alluvial material derived from the
softly consolidated calcareous, gypsiferous sandstones and shales
of the Coast Range Mountains. They are moderately to strongly
saline with slight to moderate compaction in the subsoil. Plans of
the systems are shown in Figure 1.
11
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GROUND
SURFACE
(SUPPLY ~~~<2-5 MIL POLYETHYLENE
DITCH BAFFLES
TRENCH DETAILS
DRAIN
DITCH)
I
r
5C
-25'— 1
)' ..
£\J*J •- — - — —
4
/ 0
CvJ
-Suction Probe Sites ->r/
T
SUPPLY'
TANKS,
X-DRAIN DITCH
DEEP
/"TRENCH
- y
^Csu
SHALLOW PLOT
SUPPLY DITCH
FIG I - PLAN Of DENITRIFICATION PLOTS
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The water supply for the investigations was pumped from the San Luis
Wasteway which contains a mixture of groundwater and imported Delta-
Mendota Canal water. The total quantity and the distribution of
various ions in the water varied with the season. A representative
analysis of the water is listed in Table 1.
Table 1
Chemical Analysis of Supply Water
pH conductivity Ca Mg Na NO, CO, HC03 Cl 804 T.D.S.
ECX106 mg/1
7.6
1400
37 42 172 4
378 203 48 884
The nitrate concentration of the supply water normally was less than
5 mg/1. Because of this low nitrogen level, for purposes of this
study, it was necessary to supplement the water with nitrates. This
was accomplished by dissolving calcium nitrate in a large supply
tank and then running this through a small balancing tank into
the supply ditch. It was planned to maintain a NO-j-N level of approx-
imately 9 mg/1 in the deep trench and 14 mg/1 in the shallow ponds.
However, maintaining this desired level proved to be difficult due
primarily to clogging of the outflow valve by precipitated salts
and foreign matter.
Sample Collection and Analytical Techniques
Samples were collected from the plots and analyzed by the methods
listed below:
Analysis
Nitrates
Total Nitrogen (Kjeldahl)
Ammonia
Organic Nitrogen
Dissolved Oxygen
pH
Electrical Conductivity
Mineral Constituents
Method
Specific Ion Meter (6) and/or
Brucine (7)
Micro Kjeldahl
Distillation
Micro Kjeldahl
Winkler (Hach)
Glass Electrode
Conductivity Bridge
Laboratory Procedures (8)
In addition to the chemical analysis the temperatures were monitored.
The rate of inflow and outflow was measured by a Parshall flume
equipped with a continuous stage water recorder.
Deep Trench Study
This investigation was conducted in a trench designed to simulate
a section of the San Luis Canal.
13
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Methods and Material A trench approximately 10 feet deep, 20
feet wide at the top and 200 feet long was excavated. The trench
was filled with drainage water supplemented with calcium nitrate
and covered with a layer of barley straw approximately six inches
thick. Additional straw was added periodically as open spots
appeared in the straw cover. The barley straw was the degradable
organic material used as the energy source for the bacteria.
The system was planned to operate as simply as possible with water
entering the trench from a supply ditch flowing through the straw
covered trench. However soon after the start of the experiment it
became obvious that the inflow water was short-circuiting through
the trench without completely displacing the water in the trench.
Two five mil polyethylene plastic curtains were suspended across
the trench 25 feet and 50 feet downstream from the inlet to alleviate
this problem. These curtains acted as baffles to force the water
flow downward. Although there were still stagnant areas in the
system, especially near the botton, the baffles did increase the
percentage of the water that was displaced.
A dissolved oxygen sampler was used to collect samples from the
middle of the trench 2 feet below the water surface at the inlet
and outlet and at stations 10, 25, 50, 60, 100 and 175 feet down-
stream from the inlet. At the 175-foot station, near the outlets
of the trench, samples also were collected at depth of 4 and 8 feet.
All samples were analyzed for nitrates,' dissolved oxygen, pH and
electrical conductivity.
In addition some of the samples were analyzed for nitrites, ammonia
and organic nitrogen.
Results - Samples were collected from the trench between
October 1967 and July 1968. The nitrate concentrations of the
drainage water at sampling points and for various dates as the
water moved through the trench are listed in Table 2. The variabil-
ity of the nitrate concentration of the supply water at the inlet
was due to fluctuations in the flow from the supplemental nitrate
supply system. The amount of nitrate removal ranged from almost
complete removal of the nitrate to less than 50 percent. Although
the removal rate varied widely, the reduction that did occur normally
took place within the first 50 foot lengths of the trench.
The nitrate concentration of the supply and the discharge waters
and the temperature of the discharge water for data collected
between October 1967 and July 1968 are shown in Figure 2. Although
most of the nitrate reduction took place within the first 50 feet,
the detention times listed below were based on the water flowing
through the entire reach of the trench. The detention times used
in this study were theoretical times based on the volume of the
trench divided by the influent flow rates. These calculations
neglected possible short-circuiting and stagnant zones in the
14
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Table 2
Nitrate Concentration, Dissolved Oxygen and Detention Time of Water
In Deep Pond Studies at Several Sampling Points
Date
10/18/67
10/26/67
10/31/67
11/07/67
11/13/67
11/16/67
11/21/67
11/29/67
12/11/67
12/21/67
12/27/67
1/17/68
1/24/68
1/31/68
2/07/68
2/15/68
2/28/68
3/06/68
3/14/68
3/21/68
3/27/68
4/03/68
4/24/68
5/Ub/68
5/15/68
5/22/68
5/27/68
6/05/68
Inlet
N03-N DO
mg/1
7
6
8
5
7
7
7
9
6
10
7
10
8
14
11
9
7
9
7
7
9
8
9
7
7
16
14
22
7.2
7.4
6.6
7.7
8.2
8.6
8.6
8.8
9.6
6.0
7.0
8.6
8.6
8.0
7.6
9.6
6.8
8.0
8.4
8.0
8.4
8.0
8.4
8.8
8.0
8.4
9.0
6.0
10'
NOj-N DO
mg/l
1
1
11
1
5
3
2
3
5
7
5
6
7
7
6
5
6
9
7
7
8
6
9
7
6
12
17
7
0
0
0
0
2.4
2.6
0
l.i;
5.0
3.4
5.2
1.2
2.8
2.0
0
2.4
2.0
1.4
6.6
2.6
6.0
1.0
.8
5.4
3.4
-
.8
0
DT
Days
.30
.30
.30
.18
.18
.18
.18
.10
..17
.17
.17
.17
.17
.17
.17
.17
.17
.17
.10
.10
.10
.10
.17
.17
.22
.22
.22
.22
25'
N03-N DO DT
mg/ I Days
1
1
11
1
5
3
1
2
6
8
7
5
4
3
3
2
4
5
5
5
5
5
5
5
7
13
14
5
0
0
0
0
3.2
3.4
0
0.6
7.2
5.4
5.2
1.0
0
0
1.2
0
3.6
2.2
5.0
.4
2.2
-
-
.8
3.6
.4
1.0
.6
.75
.75
.75
.44
.44
.44
.44
.25
.41
.41
.41
.41
.41
.41
.41
.41
.41
.41
.25
.25
.25
.25
.41
.41
.56
.56
.56
.56
50'
N03-N DO
tng/1
1
1
1
1
5
3
1
2
5
9
6
6
4
2
3
1
1
1
4
2
4
3
7
6
6
11
10
5
0
0
0
0
1.8
5.0
0
0
5.0
5.4
1.8
2.0
0.8
.6
4.6
0
0
0
5.6
0.2
2.8
2.4
4.4
2.4
5.4
2.4
3.8
1.2
DT
Days
1.50
1.50
1.50
.88
.88
.88
.88
.50
.82
.82
.82
.82
.82
.82
.82
.82
.82
.82
.50
.50
.50
.50
.82
.82
1.12
1.12
1.12
1.12
100'
NOj-N DO
mE/1
1
1
1
1
4
2
1
2
3
9
5
5
4
2
3
1
1
1
4
3
2
2
6
4
5
8
9
5
0
0
0
0
0.8
3.0
0
0
1.6
4.4
2.8
2.4
1.8
.6
5.0
0
0
0
5.4
3.0
2.6
2.8
6.6
3.8
5.0
2.6
7.0
3.0
DT
Davs
3.0
3.0
3.0
1.75
1.75
1.75
1.75
1.00
1.65
1.65
1.65
1.65
1.65
1.65
1.65
1.65
1.65
1.65
1.0
1.0
1.0
1.0
1.65
1.65
2.25
2.25
2.25
2.25
175'
N03-N DO DT
mp/1 Davs
1
1
1
1
3
1
1
2
1
-
3
5
4
4
2
1
1
1
3
3
2
2
6
4
5
7
8
5
0
0
0
0
0
0
0
1.0
-
2.0
-
5.4
2.4
5.0
0
0
0
6.0
3.4
4.0
2.8
6.6
4.8
5.4
5.6
6.8
4.6
5.25
5.25
5.25
3.06
3.06
3.06
3.06
1.75
2.88
2.88
2.88
2.88
2.88
2.88
2.88
2.88
2.88
2.88
1.75
1.75
1.75
1.75
2.88
2.88
3.93
3.93
3.93
3.93
Outlet(200')
NOj-N DO DT
mg/1 Davs
1
1
1
1
4
2
1
-
2
9
5
5
4
5
2
1
1
1
3
3
2
2
6
4
5
7
9
6
0
0
0
0
0
0.2
0
.8
.8
5.0
2.6
3.8
6.2
6.0
7.2
0
0
0
6.6
4.0
3.0
2.8
6.8
5.2
5.0
6.8
7.6
5.6
6.0
6.0
6.0
3.50
3.50
3.50
3.50
2.00
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
2.0
2.0
2.0
2.0
3.3
3.3
4.5
4.5
4.5
4.5
-------
O)
I
UJ
16 —
14
12
10
Detention
Time 6.0
days
t^r-Dischorge Water
v.-„.!.«/1 .\-M ..... I ..... I . .V>^J_.J ... I I .
50
40
70
60
30
OCT.
NOV DEC. JAN. FEB. MAR APRIL MAY
1967 1968
FIG. 2-DEEP TRENCH -NITRATE CONCENTRATIONS AND TEMPERATURES
JUNE JULY
o
o
00
Ld
CE
ID
or
LU
CL
5
LU
-------
trench, therefore, the true values are probably less than those
listed here. Table 2 lists the detention times and the dissolved
oxygen concentrations at the various sampling stations in the trench
for several dates during the study.
During the first six months of the study the NO,-N concentration of
the supply water normally ranged between 5 and 9 mg/1 with an average
concentration of about 8 mg/1. During the last three months the
NOj-N concentration rate was increased to an average of about 14 mg/1.
During the first month of the experiment a detention time of 5.9 days
was maintained. At this rate the nitrate nitrogen concentration in
the discharge water was reduced to less than 1 mg/1. When the deten-
tion was reduced to 3.5 days the NO^-N concentration in the dis-
charge water was about 3 mg/1 or about 57 percent of the concentra-
tion of the supply water. When a fresh supply of straw was added
to the trench the N03-N in the discharge water was reduced to zero
with no change in the 3.5 day detention time.
A further decrease of the detention time to 2 days resulted in a
rise in the NO-j-N content of the discharge water to about 4 mg/1.
The detention time was increased to 3.3 days but no appreciable
change in the nitrate content of the discharge water was noted.
It was concluded that the reason for the lack of response to the
change was that the effective detention time was being reduced by
the short-circuiting of the water and the disappearance of the more
readily available energy source in the straw. The system was
redesigned to overcome this problem by installing the two baffles
and adding more straw.
After the system was changed and with approximately the same deten-
tion time, 3.3 days, the NC>3-N concentration in the discharge water
was reduced to less than 1 mg/1. The conditions were kept constant
and this near complete reduction rate was maintained for about a
month.
When the detention time was again reduced to 2.0 days the nitrate
concentration in the discharge water increased. Even though the
detention time was later increased to 4.5 days, the nitrate reduction
rate remained at about 40 percent.
It is postulated that the principle reason for the lower reduction
rate during the later part of the study was the lack of an adequate,
available organic energy source to maintain the bacterial population
required for removal of all the nitrates in the system. Fresh straw
was added routinely at the rate of about 300 pounds per week to
maintain a solid cover over the water. This quantity apparently did
not replenish the organic carbon source as rapidly as it was used.
In part this problem was the result of wind blown dust deposited in
the straw-water mixture. As this dust became mixed with the other
17
-------
components a soil-water-straw mixture was formed on the surface of
the water in the trench which was relatively unusable as an energy
source for the bacteria. This material floated on.or near, the
water surface and prevented much of the fresh straw from coming in
contact with the water in the trench.
The dissolved oxygen content of the supply water and the discharge
water at various dates during the period of the study are plotted
in Figure 3. The dissolved oxygen content of the supply water,
normally sampled near midday, ranged from 6 to 10 mg/1. The content
of the discharge water ranged from zero to 7 mg/1. There was a
very close correlation between the dissolved oxygen content reduc-
tion and amount of nitrate reduction. During those periods when the
nitrate levels were reduced to near zero the dissolved oxygen contents
were also near zero. This correlation is to be expected, however,
it is somewhat surprising that there was at least partial denitri-
fication although the dissolved oxygen apparently was not reduced
to zero. It was assumed that this denitrification occurred in some
local areas within the system where there was complete or near
anaerobic conditions which were not detected in our sampling pro-
gram.
Although no determinations were made, at times it was evident from
the odor of hydrogen sulfide that sulfate reduction was occurring.
As the presence of nitrates inhibits sulfate reduction the appear-
ance of hydrogen sulfide in the trench would indicate the removal
of most or all of the nitrates from the water (9). Several times
during the investigation the hydrogen sulfide odor plus those from
some of the other decomposition products of the straw caused a
rather unpleasant environment around the plot area.
A number of nitrite and ammonia analyses were made of the supply
and discharge water to determine if there was a build up of either
of these nitrogen forms in the water in the trench during the denitri-
fication process. Table 3 lists the quantities of NC>3-N, N02-N and
NHj-N found in the supply and discharge water at various times
during the experiment. Also included are the pH, electrical
conductivity and temperature of the water at the time it was sampled.
The N02-N did not increase significantly except during the coldest
weather. During this cold period the increase in nitrite accounted
for only about 4% of the nitrate reduction. Most data show that
there was a reduction in the ammonia. One reason for the relatively
high concentration of ammonia in the supply water is that there was
a small percentage of this salt mixed with the Ca(N03)2 which was
used as the nitrate source to supplement the native nitrogen in the
water.
There were several factors such as the energy source, detention time
and temperature which affected the reduction rate of the nitrates
and dissolved oxygen. These factors are inter-related or are masked
sufficiently to prevent the analyses made in this study from showing
the relative contribution of each.
18
-------
11
10
8
a
CO
Detention
Time
60
days
-3.5-
days
2.01
days
3.3
days
2.0
days
— 3.3
days
4.5
days
SUPPLY WATER
/
\
I
/ v
_>' l'vJ_Ll| I I
DISCHARGE
WATER
' * ',
/ \ 'I
/ \ I I
/ \ I I
/ ' ,A ,'
, I / \ '
It T~LJ -L/ I I I I
OCT NOV DEC JAN FEB MAR APRIL
1967 1968
MAY JUNE
FIG 3-DEEP TRENCH-DISSOLVED OXYGEN
-------
Table 3
The Concentrations of the Various Nitrogen Forms, pH,
Electrical Conductivity and Temperature of the Supply
and Discharge Water, at Various Times During the Deep
Trench Experiment.
N-Form
N03-N NO
mg/1
10-21-67
TT
11-13-67
tr
1-03-68
TT
3-06-68
tt
5-01-68
TT
7-10-68
TT
Supply
Discharge
Supply
Discharge
Supply
Discharge
Supply
Discharge
Supply
Discharge
Supply
Discharge
14
11
2
10
2
9
18
3
15
6
.5
0
.2
.0
.0
.3
.6
.1
.0
.0
.0
.2
0.
0.
_
-
0.
0.
0.
0.
0.
0.
0.
0.
2-N
3
1
4
7
05
00
08
29
1
4
PH
NH3-N
o.
0.
0.
0.
0.
0.
0.
0.
1.
0.
1.
0.
19
17
57
55
38
48
90
48
1
06
15
67
7
6
7
7
7
7
7
7
7
8
8
8
.4
.9
.3
.6
.9
.9
.6
.4
.8
.0
.3
.3
EC
mmhos
0.55
0.69
0.63
0.65
1.70
1.60
1.90
1.90
1.45
1.50
1.30
1.20
Temp.
°C
23
21
17
16
10
10
17
17
22
22
30
27
Detention Time - The calculated theoretical detention time
of the entire system for this study ranged from 2 to 6 days. Some
generalizations can be made about the effect of detention time on
nitrate removal from this system. First, when there were no other
limiting parameters almost complete reduction of the nitrates was
obtained with a detention time of 3.3 days. With detention times
of less than 3.3 days, there was never more than 80 percent reduc-
tion of the nitrates.
Temperature - The temperature of the discharge water ranged
from 27°C in July to a minimum of 8°C in January. Other studies
(7) have indicated that. 16°C may be the lower limit for efficient
denitrification. This experiment, however, did not show any
correlation between temperature and nitrate reduction or if there
was an effect it was masked by other factors.
Energy Source Requirements - The theoretical straw require-
ment can be calculated using a formula derived from work by P. L.
McCarty (10). A quantity of organic waste with an oxygen equiva-
lent (Oe) of 2.86 pounds would be required to convert one pound
of nitrate-nitrogen into nitrogen gas. However, in the biological
20
-------
process, a minimum of 25 percent of the added organic material, is
used by micro-organisms for cell synthesis and is therefore unavail-
able for denitrification. Where the organic source is not easily
broken down, such as the barley straw used in this study, probably
no more than 50 percent of the material will be available for deni-
trif ication. Thus in practice an organic waste with an Oe of 2.86/
.50 or 5.72 pounds is required per pound of nitrate-N. In addition,
some organic material must be added to create the anaerobic condi-
tions required for denitrification. This requires about 1.5 pounds
of Oe per pound of dissolved oxygen (DO) in the incoming drainage
water. In summary the organic oxygen equivalent required (Or) for
denitrification can be expressed as follows:
Or - 5.72 (N03-N) +1.5 (DO)
If we assume that there will be 20 milligrams per liter of NOj-N
and 8 parts per million of dissolved oxygen in the drainage water
theoretical barley straw requirement for denitrification of this
water can be calculated from the above formula as follows:
Or - 5.72 (pounds of N03-N per AF) +1.5 (pounds of
DO per AF)
Or - 5.72 X 54.4 + 1.5 X 21.7 =- 343 pounds per acre-foot
In a like manner the theoretical barley straw requirement for the
pond study can be calculated from the above formula. If we assume
that the average N03-N concentration was 10 mg/1 and the dissolved
oxygen content of the water was 8 parts per million the calculations
are as follows:
Or - 5.72 X 22.7 + 1.5 X 21.7
- 153 pounds per acre foot
Using this quantity and the various flow rates during the study
period the theoretical daily straw requirement ranged from 41 pounds
for the 60 gpm flow and the 2 days detention time to approximately
14 pounds for the 20 gpm and the 6 days detention time. The straw
requirements for all of the flow rates and detention times are
listed in Table 4. According to these calculations the amount of
straw, about 50 pounds per day, actually added to the trench should
have been more than adequate to provide energy for complete deni-
trification of the system. That complete removal did not always
take place can probably be attributed to the fact that a readily
decomposable form of the straw did not come into the contact area
because of the mat of soil and straw floating on the water surface.
Electrical Conductivity - The concentration of total dis-
solved solids as measured by the electrical conductivity of the
21
-------
water varied during the season from about 300 to 2900 micromhos
and was primarily dependent upon the concentration of the supply
water rather than any variation as a result of changes within the
system. The low concentrations were during the periods of large
water releases from the Delta-Mendota Canal into the wasteway and
the high concentrations were during periods when all the water in
the wasteway was from seepage. Although there were evapotranspira-
tion losses they were not large enough to be measured by the con-
ductivity method used in this study.
Table 4
Flow rates, detention times and straw requirements of deep pond.
Detention Straw
Time Requirement
Days Ibs/day (d 10 mg/1 N03-N
60 2.0 41
36 3.3
25
34 3.5 23
30 4.0 20
20 6.0 14
Grass Plot Study
The shallow pond investigations were made on an 8.3 acre plot
designed to simulate a section that could be incorporated into the
Kesterson Reservoir.
Methods and Materials - The plot was rough leveled, bordered
and checked at 0.3 foot contour intervals. A layout of the plot is
shown in Figure 1.
Water grass, Echinochloa crusgalli, was planted in the plot at the
beginning of the study.The grass was to be the carbon energy
source for the denitrification process. The first year it was
mowed and left in the field. The mowing did not appear to increase
the denitrification rate therefore the practice was discontinued.
The water source for this study was the same as that for the deep
trench. Supplemental nitrate was added to the supply water in the
manner detailed in the previous study. Sodium nitrate rather than
calcium nitrate was used as the nitrate source during a part of the
study in an attempt to reduce the percolation losses from the plot.
22
-------
During the greater part of the investigation the plans were to
maintain the nitrate -N levels at about 16 mg/1, however, due to
variations in the water and supplemental nitrate-N flows the actual
concentrations ranged from about 7 to 70 mg/1. In order to evalu-
ate the nitrate reduction rate of water of higher nitrate -N con-
centration the levels were increased to about 50 mg/1 for about
32 days between April 6 and May 8, 1970.
A continuous flow of water through the plot was maintained with an
average depth of approximately six inches. The rate of flow of the
water was monitored with Parshall flumes as it entered and left the
plot. The maximum flow to the plot was limited by the size and
gradient of the supply ditch and because of this the average depth
of water was not varied. This flow, approximately 400 gallons per
minute, was maintained throughout most of the study. As the water
moved through the plot there was a reduction in flow due to evapo-
transpiration, seepage, and percolation losses. These losses were
assumed to be constant through the plot and were taken into con-
sideration in calculating the detention times. The outflow varied
from about 30 gallons per minute during the peak evapotranspiration
period in the summer to about 140 gallons per minute during the
minimum evapotranspiration period in the winter. The inflow rates
and the theoretical detention time for each check during represen-
tative periods in the summer and winter are listed in Table 5.
Results - The concentrations of the nitrates in the water at
the inlet of the plot, the outlets of checks 2 and 4, and the out-
let of the plot are graphed in Figures 4 and 5. The data show
that as the water moved through the plot there was a reduction in
the nitrate concentration. This reduction continued until it
reached the outlet of check 4, after this point generally there was
no significant change. During the study the amount of nitrate
removal varied from almost complete reduction to only about 50 per-
cent reduction. The maximum nitrate -N removal occurred in the
summer and early fall months when there was maximum grass growth
and during the late winter months and spring after the grass had
died back, as a result of killing frosts and had fallen into the
water. The least reduction occurred during the months of November
and December.
The nitrate -N concentration during the maximum reduction period
was reduced from the average 16 mg/1 to less than 2 mg/1. During
the periods of lesser reduction the concentration at the outlet
at times ranged up to about 4 mg/1 of nitrate -N. The reduction
pattern and rates were relatively consistent for the two years that
the tests were conducted.
The main emphasis of the study was placed on the removal of nitrate,
the principle nitrogen form in the drainage water, however, any
treatment system must be concerned with the removal of the total
nitrogen content of the water. The concentration of other nitrogen
23
-------
to
AUG
SEPT.
OCT.
NOV
DEC.
JAN.
FEB.
MAR
FIG 4 - GRASS PLOT- NITRATE CONCENTRATION- 1968-1969
-------
50
40
x
o>
I
UJ 30
<
Q:
h-
20
10
50
40
30
\
o»
tu
<
or
I-
20
< ' ' -
J L
_L
AUG SEPT OCT NOV. DRC JAN FEB MAR
FIG 5 - GRASS PLOT - NITRATE CONCENTRATION - 1969-1970
itl«i P . \
-.^jblL/r-.-r.i
APRIL
-------
forms, nitrite, ammonia and organic N were generally low in both
the influent and effluent waters. However, there were periods
during the winter months when there was evidence, as noted in Table
9, that the total nitrogen content, especially the organic -N in
the effluent was greater than the allowable maximum nitrogen dis-
charge rate for the Delta of 2 mg/1.
Table 5
Calculated Inflow Rates and Theoretical Detention
Times of the Various Checks in the Grass Plot
Check No. Area
Acres
Ave. Flow Rates
GPM
Summer Winter
Detention Time (Days)
Per Check Accumulative
Summer Winter Summer Winter
1
2
3
4
5
6
Outlet
Total
0.27
1.31
-1.26
2.79
1.56
0.86
8.05
400
370
330
270
140
70
30
400
390
350
310
220
170
140
0.1
0.4
0.5
1.5
1.5
1.6
5.6
0.1
0.4
0.4
1.2
0.9
0.7
-
0.5
1.0
2.5
4.0
5.6
0.5
0.9
2.1
3.0
3.7
3.7
When the supply water in which the nitrate -N concentration had been
increased to 40 mg/1 moved through the plot, there was a gradual
reduction of the nitrate -N until at the outlet it had been reduced
to about 1-4 mg/1.
At this time we can only theorize as to the cause of the variation
in the removal rates, especially as to the greater reduction in the
colder winter months with the diminished grass cover. The best
explanation would seem to be that after the grass has died back and
lodged, much of the plant matter is deposited in the water near
the bottom of the ponds where the material is more rapidly decom-
posed thus resulting in a relatively large available carbon source.
As the grass decayed there were more open spaces on the water sur-
face which might be expected to encourage an increase in algae
growth thus accounting for some of the nitrate reduction by an in-
crease in organic nitrogen in the algae plant cells. Algal deter-
mination made in February 1970 indicated that there was a decrease
in the algal count as the water moved through the plot. The genera
26
-------
and the estimated number of cells per milliter at several stations
in the plot are listed in Table 6.
Tests for nitrite, ammonia and organic nitrogen indicate that, gen-
erally, there were small amounts of these N forms present however
with the exception of some of the winter months there were no signi-
ficant increase in these quantities as the water moved through the
plot.
Table 6
Algae Count at Several Sampling Sites
in Grass Plots - February 26, 1970
Sample Genus Cells/ml
Inlet Diatom-Nitschia 2,500
Diatom-Amphiprora 500
Diatom-Diatoma 3,000
Check 2 Diatom-Diatoma 4,000
Check 4 Diatom-Diatoma 1,000
Outlet Diatom-Diatoma 500
During the months in which there were increases in the total
organic N at the outlet as compared to the inflow water these
increased amounts were a relatively small portion of the total
losses. There was no evidence that at any stage of the study there
was a recycling of the lost nitrogen. This would suggest that
denitrification with its resultant loss of nitrogen gas accounts
for most of the nitrates removed. The concentration of various
forms of nitrogen at several dates during the study are listed in
Table 7.
Dissolved Oxygen - The changes in the dissolved oxygen
content of the water as it moved through the plot were inconsistent.
Generally, during the warmer periods when there was a good cover of
grass over the ponds there was a reduction of the dissolved oxygen.
During short periods of time when the reduction was at its peak,
the DO was reduced from an average of about 8 to about 1 mg/1.
Normally the reduction was at a lesser rate, with the maximum
removal about 60 percent of the total. After December when there
was very little grass still standing in the ponds the reduction
was negligible. There was a fair correlation between the percent
removal of DO and nitrates during the warmer months. At other
periods there was no obvious correlation between the two parameters.
During the late winter and early spring months there was almost
complete removal of the nitrates but there was no significant reduc-
tion in the measured DO content. This fact would appear to be a
27
-------
Table 7 - Concentration of various nitrogen forma, temperature,
pH and electrical conductivity at four locations in
the plot
ro
on
Date
First Period
8-14-68
11
II
II
9-11-68
ti
ii
ti
H-l-68
11
H
it
2-28-69
II
It
II
Second Period
8-29-69
ti
ti
ti
9-12-69
It
It
tl
10-9-69
ii
ti
it
Location
Inlet
Qheck #2
Check #4
Outlet
Inlet
Check #2
Check #4
Outlet
Inlet
Check n
Check #4
Outlet
Inlet
Check #2
Check #4
Outlet
Inlet
Check #2
Check #4
Outlet
Inlet
Check #2
Check #4
Outlet
Inlet
Check #2
Check #4
Outlet
N03
8.5
9.6
2.2
.6
14.4
9.7
.2
.2
12.1
9.5
3.4
1.1
38.6
29.5
.2
.2
18.0
8.0
.8
.8
15.0
19.3
.5
.5
11. 0
9.1
3.4
1.0
N-Form
N02
mg/l
.02
.90
.05
.01
.03
.5
0
0
-
.
-
-
-
•
.
-
2.8
5.6
0
.8
1.8
.1
.1
1.1
.5
.9
.6
NH3
.35
.03
.01
.3
.5
.5
.02
.02
-
.
.
-
4.76
.68
.68
4.76
.
-
-
-
.08
00
00
00
.21
.05
.06
.16
Org.N
.
.
-
-
_
.
.
.
6.6
8.3
5.6
4.3
1.68
2.26
5.34
6.72
1.0*
1.7*
2.0*
2.3*
.80
.64
.70
1.27
.85
.57
.88
.67
Temp.
•c
25.3
25.0
24.5
27.0
26.0
24.0
24.0
27.0
17.0
15.0
15.0
14.5
11.5
10.5
13.0
13.0
23.0
18.0
18.0
18.0
20.0
19.5
19.5
20.0
19.0
17.0
16.0
19.0
PH
8.3
8.3
8.0
8.2
8.1
8.1
8.2
8.0
7.8
7.8
8.1
7.4
8.3
7.9
7.6
7.6
8.0
7.8
7.4
7.8
7.6
7.8
7.9
8.0
7.6
7.0
6.9
7.0
EC
iranhos
1.4
1.35
1.3
1.7
1.3
1.1
1.5
1.0
2.1
2.0
1.8
1.3
1.9
2.0
1.9
1.7
1.6
1.4
1.4
1.5
1.4
1.4
1.4
1.4
.5
.5
.5
.5
* Total Organic N + NH3
-------
contradiction of the requirement of an anaerobic condition before
the denitrification process takes place. At this point we can only
postulate that the reaction takes place in local areas near the
ground or the stem surface of the plants where there are anaerobic
conditions but our sampling techniques were not sufficiently refined
to detect these conditions.
Temperature - The temperature of the supply water varied
from a maximum of 28°C in the summer to a minimum of 8°C in
December and January. The reduction in the removal rate of the
nitrates correlated reasonably well with the decrease in the tem-
perature of the water in the early winter months of November and
December- However, although there was no significant increase in
the water temperature in January there was a decided increase in
the nitrate removal rate.
Although not verified it may be that as the grass decayed, the
decomposition products provided a readily available energy source
that outweighed cool temperature effects. Regardless of the
cause almost complete removal of nitrate was obtained with tempera-
tures down to 8°C.
Percolating Water Studies - In August 1969 two sets of
small porous ceramic cups were installed in the soil at locations
near the inlets of checks 2 and 6. These cups were placed at 12
inch depth increments from 6 to 54 inches to get a nitrate concen-
tration profile of the percolating water as it passed downward
through the soil. Samples of the soil solution were collected
from these depths by applying suction to the instruments. All the
extracts collected were analyzed for nitrates, electrical conduc-
tivity and pH. For some extracts nitrite, ammonia and total organic
N were determined.
The results of these tests indicated that there was a rapid reduc-
tion of the nitrates as the water moves into the soil. Most of
the reduction took place before the water reached the 6 inch depth.
These results are similar to the findings of Mikkelson, et al (11)
in their studies of flooded soils. They found that there is only
a thin layer of soil, not more than \ of an inch where oxygen is
present. Below this, there is a reduction layer which changes the
nitrate -N by biological reduction to N gas which escapes into
the air.
The NOj analyses of samples taken from the various depths are
listed in Table 8. These data indicate that in most instances
maximum reduction had been reached at the 6-inch depth and after
this depth there was very little change. The nitrate -N concentra-
tions of most of the analyses were under 1 mg/1 NC>3-N. With a
few exceptions all of the analyses were less than 2 mg/1 N03-N.
These values would meet the nitrogen standards established for the
discharge of agricultural waste water into the Delta.
29
-------
Date
7/09/69
8/07/69
8/15/69
8/19/69
8/27/69
9/05/69
9/17/69
9/24/69
9/30/69
10/08/69
10/20/69
10/30/69
11/05/69
11/12/69
11/19/69
11/26/69
12/03/69
12/10/69
12/17/69
12/23/69
1/02/70
1/07/70
1/15/70
1/21/70
1/28/70
2/05/70
2/11/70
2/18/70
3/03/70
Table 8
The Nitrate -N Concentration of the Soil Extract
From Several Depths Below the Grass Plot
Surface
6"
18"
Milligrams per Liter -
11.1
7.9
9.0
2.5
8.4
11.1
3.4
14.5
3.4
12.2
15.8
13.5
7.9
11.2
17.8
33.9
0.5
0.4
1.7
0.5
1.7
1.1
0.3
0.4
1.4
0.7
4.5
1.8
0.8
0.9
1.1
0.7
0.8
0.4
0.7
2.3
0.9
1.1
2.5
0.9
1.4
1.1
0.6
0.5
1.6
0.6
2.1
0.9
0.9
1.0
0.8
0.6
0.7
2.5
1.4
1.1
0.6
0.8
1.0
0.6
1.4
0.4
0.6
1.7
0.6
0.8
2.1
0.8
1.8
0.9
2,8
0.9
1.1
0.9
0.9
0.7
1.7
1.0
1.1
0.3
1.3
0.8
1.1
0.5
0.9
0.4
0.7
1.1
0.8
0.8
1.4
0.9
1.2
1.0
42"
0.3
0.4
0.6
0.5
1.4
0.9
1.3
0.9
1.4
1.1
0.7
0.9
1.4
1.1
0.8
0.4
0.6
1.7
0.8
0.7
1.0
1.2
1.2
0.9
1.3
1.1
1.3
0.8
.9
,7
54"
0.3
0.4
1.6
0.6
2.2
1.6
1.8
1.1
1.2
0.
0.
2.8
1.2
1.1
0.2
0.6
0.6
1.3
1.4
1.1
1.1
1.7
0.8
1.5
1.8
1.9
1.5
1.8
1.4
There were no drains installed under these plots, therefore, the
effect of moving the water out of the area on the nitrate concen-
trations could not be measured. This type of measurement would be
essential before definite recommendations could be made on this
system. A system with drain tiles installed should be set up.to
determine if there is a continuous removal of the nitrates to
permissible levels from the percolating water where there are
established drains. Any drains installed should be "under designed"
or so constructed that the drains are submerged to maintain con-
tinuous anaerobic conditions.
30
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A mass nitrogen balance for the grass plot could be calculated
employing the following equations:
nitrogen in (pounds)
nitrogen out (pounds)
nitrogen concentration of inflow (mg/1)
volume of flow (Ac. Ft.)
conversion factor to change units to pounds
N released from immobilized form (pounds)
Ds + Dp +Pd + I + 0
Where Ds - N denitrified in water - loss to air
N denitrified by plant decay - loss to air
loss by deep percolation
(a)
(b)
N± - NO
Where Ni -
NO «
Ni - Cn Qi k + ]
Where Cn -
k -
(c) N0
DP
Pd
N
I » N immobilized in organic forms
0 - N lost in discharge outflow
At this time we do not have enough data to separate that portion
of the nitrogen lost by denitrification and that lost by immobili-
zation in organic forms. However, it is of interest to note the
amount removed from the system by these combined processes. The
calculations were based on the average values of the various
parameters for a 24 hour period. The values used are listed in
Table 9.
Table 9
Quantity of Surface Flow, N03-N Concentration
and Deep Percolation in the Grass Plot for an
Average 24-hour Period
Location
Inlet
Check #1
Check #2
Check #3
Check #4
Check #5
Check #6
Outlet
Flow
A.F./day
1.8
1.68
1.50
1.28
.80
.54
.38
.38
Concentration
N07;-N, mg/1
16
15
13
10
5
3
2
1
Deep Percolation (1)
A.F./day
.11
.16
.19
.42
.23
.14
(1) Deep percolation « flow loss minus evapotranspiration.
31
-------
(b)
Cn Qi
Where
70 ppm NC>3 * 16 ppm N
Qi - 1.8 a.f.
k - 2.72
Ri - 0.2 Ibs. - ave. daily N release from
decomposition of plant material
(a)
(c)
* 16 x 1.8 x 2.72 + .2 - 78.5
M — M .
W0 Nl
N0 ~ 78.5 pounds
NO - Ds + Dp + Pd +1 + 0
Ds+ Dp+ I - N0 -r *" to >•" *••
»• C*«cr«i« Lnt*4 C«ll«ct*r OpviHt
0-0 Z t» »• Z« e ' »
0-S4 »»O c It
" 0 SH«< ».»•
If « '«»» 0'5«cC. H-3»2llt
L
\
. 4.
L
f * -
} \
AH LUIS 0**l*^ fUmf ^COMCOtTt LIMCO Tt»HIHtL OftIM
a- 5« 1 1 1 «• it - »»e t 1 1
TYPICAL 1200' UNIT
FIGURE 6 — DEEP TRENCH NITRATE REDUCTION PONDS
39
-------
LEGEND
I 4'
»*••»« »>M Q
Or».«
O-I4O rH '• *M> rH
4~ «• 14* 0«
i
) OU»I eft «• MO cf«
too 1000
FICURE 7 -SHALLOW NITRATE REDUCTION POND
TYPICAL »«. MILC SECTIOM
40
-------
SECTION VII
Discussion
These investigations were initiated as empirical studies to deter-
mine if denitrification could be induced by utilizing facilities
somewhat similar to the San Luis Drain and the Kesterson Reservoir
and using agricultural waste products or plants grown in place as
the organic carbon source. When it was determined that it was
possible to reduce the nitrate concentration by these means, the
investigation was extended and refined to more precisely define
parameters such as denitrification rates, optimum operating con-
ditions, design criteria and costs. Because of the problems in-
herent in quantifying data from a relatively large field-size study
the results were not always conclusive. However, although the
many ramifications of the processes could not always be explained,
it was evident that substantial percentages of the nitrates can be
removed by these methods.
Air pollution control regulations in Fresno County (12) designed
to promote environmental enhancement place restrictions on burning
of stubble. These regulations will undoubtedly become more restric-
tive with time and will force growers to find other means to dispose
of their straw. The use of the straw in a denitrification process
would serve as one means of disposal. Cost of the straw to the
project should be no more than baling, transportation expenses,
and residue removal after oxidation. When the estimated peak
drainage flow of 300 cubic feet per second is reached the daily
straw requirement would be approximately 100 tons per day. The
ultimate annual requirement for the estimated 155,000 acre-feet per
year outflow will be about 26,000 tons. This would be equivalent
to the straw yield from approximately 13,000 acres of grain.
Denitrification by the grass plot method or variation of this
method shows considerable promise. Although the lack of suitable
controls prevented precise evaluations of all causes and effects
in the system, the empirical results indicate that the denitrifica-
tion process will take place under the conditions studied. In the
simple system in which water flowed across a grass covered field,
it was demonstrated that the nitrate concentration during part of
the year can be reduced to less than 2 mg/1 nitrate -N. This level
would meet the minimum standards for discharge into the Delta. At
other times it would be necessary to store and recycle the water
or treat the effluent with a more precisely controlled method.
The investigations indicated that water could be treated in shallow
grass plots at the rate of .15 cubic feet per second per acre. At
this rate approximately 2,000 acres of ponds would be required to
service the 300 cubic feet per second of ultimate peak flow in the
San Luis Drain or approximately 6,000 acres to treat an outflow of
1,000 cubic feet per second, the projected ultimate drainage outflow
from the San Joaquin Valley. These estimates were based on the
41
-------
assumption that the experimental criteria derived from the test
site can be extrapolated to a large scale system. In addition
to the land required for the ponds additional areas will be required
for ditches, roads and other service areas. The total land require-
ment to treat the flow from the San Luis Service Area would be
approximately 2,500 acres.
Several variations of this plan might be implemented. At this
time the most feasible method would seem to be to incorporate the
shallow ponds into the Kesterson Reservoir area. This would
permit many of the facilities and structures, already designed into
the Reservoir to be used in the denitrification plan and yet not
essentially change the main purposes for which the Reservoir was
designed. Some supplemental facilities would have to be installed
such as additional contour checks, flow control structures, ditches,
and pumps. A layout of a typical section of ponds is shown in
Figure 7.
If no satisfactory arrangement can be worked out to use the Kester-
son facilities, it would be necessary to purchase additional lands
for the denitrification. The most logical location for these
would be in the Grasslands.
A variation of this plan would be a system in which denitrification
of surface flows was supplemented by denitrification in percolating
waters through the soils. In this plan a drain system would be
installed beneath the ponds.at a depth near 42 inches. These drains
would be designed so that they would be submerged at all times.
Infiltration would be encouraged and the percolating waters collect-
ed in the field drains and returned to main collector system. This
plan would require additional construction expenses for the drain
installations, however, the present studies indicate that this
method gives more consistent and complete nitrate removal than any
other type investigated.
Another alternative of this plan would be to reach an agreement
with the Grasslands Soil Conservation District to cooperate in
their "Master Plan for Land and Water Use in the Grasslands of
Western Merced County California" (13). This agency has authorized
a series of studies to investigate the feasibility of a program
to enhance the wildlife program of the area. The major objectives
of this plan are to import sufficient water of reasonable quality
to provide a year round program to assist in developing a grazing
plan consistent with wildlife and livestock and improve the
migratory waterfowl habitat vital to the maintenance of the Pacific
Flyway.
Studies have indicated that the area could use approximately 400,000
acre-feet of water during the peak use months of June, July and
August (14). The Grassland Soil Conservation District presently
42
-------
has a contract with the water districts of the area to the affect
that it will accept drainage water with total dissolved solids up
to 3,000 parts per million (14). If the waters in the San Luis
and master drain could meet these standards it might be advantageous
to seek an agreement with the Grasslands to deliver these waters
to that area. The nitrates in the water moving through the native
and pasture grasses on these lands should be reduced in essentially
the same manner as in the grass plots study.
After the water has moved through these grasslands any runoff
water could be collected into the Kesterson Reservoir. The
northern (lower) boundary of the Grasslands Water District joins
the southwest boundary of the Kesterson Reservoir, therefore, it
would be relatively easy to collect the excess and presumably
denitrified runoff water into Kesterson Reservoir.
At this point such a plan is purely speculative and may be in
conflict with some of the purposes of the drainage program, however,
it would appear to have sufficient merit to warrant further investi-
gation whenever all parties have firmed up their plans.
43
-------
Mr. Robert J. Pafford
Regional Director
Region 2
Bureau of Reclamation
U.S. Department of
Interior
SECTION VIII
ACKNOWLEDGEMENTS
Board of Directors
Mr. Paul De Falco, Jr.
Regional Director
Pacific Southwest Region
Water Quality Office
Environmental Protection
Agency
Program Coordinator
Mr. John Teerink
Deputy Director
State of California
Department of Water
Resources
Resources Agency
John Maletic Chief, Land Resources Branch
Engineering and Research Center, USER, Denver
Conducted By
John Williford Research Soil Scientist, USER, Fresno
Under Direction Of
John Bailey Chief, Land Resources Branch, USER, Sacramento
Doyle R. Cardon. . . Head, Land Use, Drainage, and Economic Section,
USER, Fresno
Assisted By
Joseph Cummings Natural Resources Specialist, USER
Ben Nakamura Soil Scientist, USER
Nels Edquist Natural Resources Specialist, USER
Dave Smolen Natural Resources Specialist, .USER
George Theiss Soil Scientist, USER
John Wessies Soil Scientist, USER
Don Nelson Physical Science Technician, USER
Maryellen Ceja Typist, USER
Gerry Smith Typist, USER
Buddy Smith Cartographic Technician, USER
Report Prepared By
John Williford Research Soil Scientist, USER, Fresno
Special Acknowledgement To
John A. McKeag . . . .Drainage Specialist (Retired), USER, Sacramento
45
-------
SECTION IX
REFERENCES
(1) Johnston, W. R., Ittihadieh, F., Daum, Richard M., Pillsbury,
Arthur F., "Nitrogen and Phosphorous in Tile Drainage Efflu-
ent," Soil Sc. Soc. Ameri. Pro., Vol. 29, p. 287-289, 1965.
(2) State of California, Department of Water Resources, "San
Joaquin Valley Drainage Investigations, San Joaquin Master
Drain," preliminary edition, Bulletin No. 127, Jan. 1965.
(3) Goldman, Joel C., Arthur, James F., Oswald, William J., Beck,
Louis A. "Combined Nutrient Removal and Transport System for
Tile Drainage from the San Joaquin Valley", Agricultural
Waste Water Treatment Center, Firebaugh, Calif., Dec. 1969.
(4) Nightingale, Harry, Personal Communication, ARS, U.S.D.A.,
Fresno, California, Sept. 1969.
(5) Cole, R. C., et al, "Soil Survey, The Los Banos Area, Califor-
nia", U.S.D.A., p. 58, 1952.
(6) Instruction Manual, Nitrate Ion Electrode Model 92-07, Orion
Research Inc., Cambridge, Mass., 1967.
(7) "Standard Methods for the Examination of Water and Wastewater",
American Public Health Association, Inc., New York, N.Y., 12th
Ed. 1965.
(8) Reclamation Instructions, Release No. 577-1 U.S. Department of
the Interior, Bureau of Reclamation, Office of Chief Engineer,
Denver, Colorado, 1967.
(9) Connel, W. E., and Patrick, W. H., Reduction of Sulfate to
Sulfide in Waterlogged Soils, Soil Sc. Soc. Amer. Pro. Vol.
33, 1969.
(10) State of California, Department of Water Resources, "Field
Evaluation of Anaerobic Denitrification in Simulated Deep
Ponds", Bulletin No. 174-3, May 1969.
(11) Mikkelson, D. S., Finfrock, D. C., Miller, M. D., "Rice
Fertilization", California Agric. Exp. Sta. University of
Calif., Davis, Leaflet 96, June 1958.
(12) Fresno County Air Pollution Control District, Rules and
Regulations, Fresno, Calif., June 2, 1969.
47
-------
(13) M & L Engineering "Master Plan for Land and Water Use in the
Grasslands of Western Merced County, California,"Phase III,
Los Banos, Calif., 1967.
(14) Dickey, G. L., "Master Plan for Land and Water Use in the
Grasslands of Western Merced County, California", Phase I,
U.S. Soil Conservation Service, Fresno, California, Unpublish-
ed Data.
: U. S. GOVERNMENT PRINTING OFFICE : 1972— 484-484/140
48
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1
5
Accession Nufnbcr
2
organization Department
'RiiT>e>an nf
Subject Field & Croup
OS-D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
of Interior
Penlamat--! rtn
Fresno Field Division
Fresno California
Title
TECHNIQUES TO REDUCE NITROGEN IN DRAINAGE
EFFLUENT DURING TRANSPORT
10
Authorfs)
l.l-i 1 1 -i f^-^A .T^Un t.l
16
Project Designation
13030ELY06/71-10
Cardon, Doyle R.
2] Note
22
Citation
Agricultural Wastewater Studies, 1971
Report No. REC-R2-71-1G"
Pages 4ft Figures 7 Tables 11 References 14
23
Descriptors (Starred First)
*Waste Water Treatment, *Nitrates, *Denitrification, *Agricultural Waste,
Algae, Anaerobic Bacteria, Dissolved Oxyge'n, Dissolved Solids, Cost Analyses
25
Identifiers (Starred First)
*San Luis Drain, California, *Kesterson Reservoir, *Nitrogen Reduction,
Detention Times
27
Abstract
Three methods to remove nitrates from the agricultural drainage water
from the San Luis Service Area were investigated. One method was a
theoretical evaluation of nitrate removal by -algae during "the transport
of the drainage water in the San Luis Canal or-during storage in the
Kesterson Reservoir. The other methods were designed to promote
anaerobic bacterial denitrification in a continuous flow of drainage
water. One method used barley straw and the other water grass grown
in shallow ponds as the carbon energy source. The barley straw was
placed in a trench about 10 feet deep and the nitrate removal rate
determined under various flow and detention rates. The water grass was
grown in ponds under a continuous flow of water of about 4 to 6 inches
depth. Under optimum conditions both methods reduced the nitrate -N
concentration of the drainage water from a maximum of about 30 rag/1 to
less than 2 mg/1. The~ceat of nitrogen removal by the shallow grass
plot systems, the most economical and feasible method investigated, was
estimated to be $6.50 per acre foot or $20.00 per million gallons.
Abstractor
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