CLEA
WATER POLLUTION CONTROL RESEARCH SERIES * 13030 ELY 06/7! 14
REC-R2-TI -1
DWR NO.
BIO-ENGINEERING ASPECTS OF AGRICULTURAL, DRAINAGE
SAN JOAQUSN VA LLEY, CALI FORN I A
DENITRIFICATION BY ANAEROBIC
PI I TFRQ
r I Li Li\D
PHASE H
JUNE I9TI
_ „-.'x
ENVJRONMENTAL PROTECTION AGENCY^RESEARCH AND MONITORING
-------
BIO-ENGTSEERIlfG ASPECTS OF AGRICULTURAL DRAIHAGE
SAN JQAQUIH VALLEY, CALIFORNIA
Bio-Engineering Aspects of Agricultural Drainage
reports describe the results of a unique interagency study
of the occurrence of nitrogen and nitrogen removal treat-
ment 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 United States 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
The first, three-year phase of the interagency study is
to be reported upon in a series of twelve reports.
The second, one-year phase of the interagency study vas
limited to continued work on the two principal treatment
methods. The second phase work develops design criteria
and operational parameters for full-scale treatment
facilities.
This report, "DESITKEFICATIOH BY ANAEROBIC FILTERS AHD
POHDS ~ PHASE II", and the companion report, "REMOVAL
OF HITRATE BY AN ALGAL SYSTEM — PHASE U", contain the
results of the second phase of the interagency study.
These two reports are numbered sequentially, after the
first twelve, in the series entitled "Bio-Engineering
Aspects of Agricultural Drainage, Sen Joaquin Valley,
California".
-------
BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEI, CALIFORNIA
DENITRIFICATION
BY
ANAEROBIC FILTERS AND PONDS
PHASE II
Study Conducted by
Robert S. Kerr Water Research Center
Treatment and Control Research Program
Ada, Oklahoma
The agricultural drainage study was coordinated by:
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
PROGRAM #13030 ELY
June 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00
-------
REVIEW NOTICE
This report has been reviewed by the
Water Quality Office of the Environmental
Protection Agency, U. S. Bureau of
Reclamation, and the California Depart-
ment of Water Resources and has been
approved for publication. Approval does
not signify that the contents necessarily
reflect the views and policies of the
reviewing agencies nor does mention of
trade names or commercial products con-
stitute endorsement or recommendation for
use by either of the reviewing agencies.
-------
ABSTRACT
Operational criteria, design and operating costs for a treatment
facility to remove nitrogen from agricultural tile drainage in the San
Joaquin Valley were further investigated during 1970 at the Interagency
Agricultural Wastewater Treatment Center (IAWTC) near Firebaugh,
California. The year-long study is identified as Phase II. Based on
projected nitrate-nitrogen concentrations for valley tile drainage water,
the research in this phase extended earlier Phase I studies on the feasi-
bility of bacterial denitrification by filters and covered ponds. The
anaerobic filter with 1-inch rounded aggregate was capable of reducing
influent nitrate-nitrogen from 30 mg/1 to 2 mg/1 at water temperatures
from 12° to 16°C at a 6-hour detention time, and from 15 mg/1 to 2 mg/1
at water temperatures of 20° to 24°C at 1-hour detention time. Long-term
operation of filters resulted in accumulation of bacterial mass which
caused the deterioration of the hydraulic regime and nitrogen removal
efficiencies. Air scour accompanied or followed by flushing with water
was capable of controlling the bacterial mass. The consumptive ratio,
a method to quantify the organic carbon source needed for the anaerobic
bacterial process, was affected by temperature and influent nitrogen
concentration and was found to vary between approximately 1.2 and 2.4.
The anaerobic covered pond reduced influent nitrate-nitrogen from 30 mg/1
to 2 mg/1 at water temperatures of 12° to 16°C with a 60-day detention
time and from 15 mg/1 to 2 mg/1 at 20° to 24°C with a 10-day detention
time.
This report is submitted in partial fulfillment of Project No. 13030 ELY
under the sponsorship of the Environmental Protection Agency.
111
-------
BACKGROUND
This report is one of a series which presents the findings of intensive
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 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's
water bodies. Other agencies cooperated in the program by providing par-
ticular 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 investi-
gation to assess the extent of salinity and high groundwater problem and
to develop plans for drainage and export facilities. The Burns-Porter
Act, in 1960, authorized San Joaquin Valley drainage facilities as a part
of the California Water Plan.
The authorizing legislation for the San Luis Unit of the Bureau of Recla-
mation'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 Environmental Protection Agency 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 Agency's report concluded that the nitrogen content of
untreated drainage waters could have significant adverse effects upon the
fish and recreation values of the receiving waters. The report recommended
a three-year research program to establish the economic feasibility 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 investigation included an inventory of
nitrogen conditions in the potential drainage areas, possible control of
nitrates at the source, prediction of drainage quality, changes in
nitrogen in transit and methods of nitrogen removal from drain waters,
including biological-chemical processes and desalination.
VI
-------
CONTENTS
SECTION PAGE
Abstract iii
Background v
Contents vii
Figures viii
Tables ix
I Summary and Conclusions......... 1
Anaerobic Denitrification 1
Anaerobic Filters 1
Anaerobic Covered Ponds 2
II Introduction 3
III Methods and Materials 5
IV Results and Discussion 7
Anaerobic Denitrification Filters 7
Temperature and Detention Time 7
Organic Nitrogen and Ammonia 10
Organic Carbon Source 10
Biomass Control 13
Scale-Up Factors 16
Phosphorus 18
Filter Media 19
Anaerobic Covered Deep Ponds 22
Summary of Operation 22
Effect of Temperature and Detention 24
Time on Nitrogen Removal
Hydraulic Studies 25
Recirculation 27
Recommended Design and Cost Estimates 28
V Acknowledgment 29
VI References 31
VII Publications 33
VI1
-------
FIGURES
NO. PAGE
1 Predicted Drainage Flow and Nitrate-Nitrogen Concentration 5
For Tile Drainage
2 Predicted Annual Effect of Detention Time on Total Effluent 8
Nitrogen in Agricultural Tile Drainage
3 Consumptive Ratio at Different Influent Nitrogen 10
Concentrations and Temperatures
4 Seasonal Variation in Required Methanol Injection and 12
Influent Nitrate-Nitrogen Concentration
5 Nitrate-Nitrogen Removal Response to Methanol Injection 12
in Anaerobic Filters
6 Required Influent Water Pressure to Filters with Interval 14
Flushing
7 Filter Recovery after Bacterial Removal at Intervals 15
8 Results of Hydraulic Tracer Studies Performed on 17
Pilot-Scale Filter
9 Theoretical Phosphorus Concentration Requirement and 19
Actual Influent Phosphorus Concentration for
Facultative Bacteria
10 Hydraulic Tracer Results for the 2-Hour Detention Filter 21
11 Predicted Detention Time Requirement for Covered Pond to 25
Meet Effluent 2 mg/1 Nitrogen Criterion and Tile Drain
Nitrogen Concentration
12 Hydraulic Tracer Results for the Covered Deep Pond 26
Vlll
-------
TABLES
NO. PAGE
1 Summary of Sampling Frequency and Methods of Analysis 6
? Nitrate-Nitrogen Removal in Artificial Medium Filter 9
3 Characteristics of Filter Media 20
4 Summary of Operation and Effluent Nitrogen Concentration 23
for the Covered Deep Pond
IX
-------
SECTION I
SUMMARY AND CONCLUSIONS
Anaerobic Denitrification
Bacterial denitrification in anaerobic filters and anaerobic covered
ponds is a feasible means of removing to a level of 2 mg/1 or less as
total nitrogen, the nitrates that vary seasonally between 14 mg/1 and
34 mg/1 from agricultural tile drainage in the San Joaquin Valley. This
finding, demonstrated earlier in Phase I of the investigation, was
further supported by research resulting from Phase II. Moreover, data
collected during Phase II showed that no Operational problems would
impair the successful treatment of the waste by these methods. Cost
estimates as developed in Phase I of $92 per million gallons for anaerobic
filters and $88 per million gallons for covered ponds are still considered
applicable.
Anaerobic Filters
1. The most feasible medium in terms of nitrogen removal efficiency
cost was 1.0-inch diameter rounded aggregate.
2. Experimental work over extended periods of operation with 1.0-inch
rounded aggregate indicated that filters will produce an effluent
which meets the criterion of 2mg/1 of total nitrogen. The anaerobic
filter was capable of reducing influent nitrate-nitrogen from 30 mg/1
to 2 mg/1 at water temperatures from 12° to 16°C at a 6-hour detention
time and from 15 mg/1 to 2 mg/1 at water temperatures of 20° to 24°C
at a 1-hour detention time. Detention times of 1 to 6 hours were
required during the remainder of the year as the water temperature
varied from 16° to 20°C and the influent nitrate-nitrogen varied
from 15 to 30 mg/1.
3. Long-term operation necessitated the removal of bacterial mass from
the medium beds of the filters. Air injection of air at 10 scfm/ft
for 5 to 30 minutes with or followed by flushing with water was the
most promising method tested.
4. The consumptive ratio for anaerobic filters, which determines the
quantity of required organic source, varies with water temperature and
influent nitrogen concentration. At 12° to 16°C, the ratio varies
from about 1.5 to 2.4, while at 20° to 24°C the ratio varies from
about 1.2 to 2.0.
—1—
-------
Anaerobic Covered Ponds
1. The anaerobic covered pond was capable of reducing influent
nitrate-nitrogen from 30 mg/1 to 2 mg/1 at water temperatures from
12° to 16°C at a 60-day detention time and from 15 mg/1 to 2 mg/1
at water temperatures of 20° to 24°C at a 10-day detention time.
During the remainder of the year as the influent nitrate-nitrogen
varied from 15 to 30 mg/1 and the water temperature varied from
16° to 20°C, detention times between 10 and 60 days were required.
2. Recirculation of 25 percent of the effluent was necessary to give
the results presented in Item 1 for most of the year. However, when
the water temperature is above 20°C, the recirculation appears
unnecessary.
-2-
-------
SECTION II
INTRODUCTION
This report covers the Phase II experimental studies on bacterial
denitrification of San Joaquin Valley agricultural tile drainage waters
at the Interagency Agricultural Wastewater Treatment Center (IAWTC) near
Firebaugh, California. Phase I of the studies, which ended in December
1969 was devoted to determining whether or not the processes under study
were technically feasible methods for removal of nitrate-nitrogen from
agricultural tile drainage. The purpose of Phase II was to develop
operational criteria and to substantiate treatment cost estimates.
This report presents only new information obtained during Phase II, the
1970 calendar year. The reader should refer to the Phase I report
Denitrification By Anaerobic Filters and Ponds (1) for literature review,
description of units, and Phase I results and conclusions.
-3-
-------
SECTION III
METHODS AND MATERIALS
The description and methods of operation for the anaerobic denitrification
units used in Phase II studies were essentially unchanged from those
described in the Phase I report (1). When pertinent, minor modifications
in unit design and operations are described in the "Results and Discussion'
of this report. A summary of sampling frequency and methods of analysis
is presented in Table 1.
Phase I results, except for several cases, were obtained using a constant
influent nitrate-nitrogen concentration of 20 mg/1. For Phase II studies,
in order to approximate conditions expected in a treatment plant for San
Joaquin Valley tile drainage, the influent nitrate-nitrogen concentration
was adjusted to conform to the predicted tile drainage flow as presented
in Figure 1 (2).
o
3 10
z
z
o
1-5-
Ul
O
(E
30 —
•«*
9
25 —
U>
,5g
O
o
10 IT
JANUARY FEBRUARY MARCH APRIL ' MAY ' JUNE ' JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER
FIGURE I-PREDICTED DRAINAGE FLOW AND NITRATE-NITROGEN
CONCENTRATION FOR TILE DRAINAGE
-------
TABLE 1
SUMMARY OF SAMPLING FREQUENCY AND METHODS OF ANALYSIS
PARAMETERS
FREQUENCY
FILTERS
PONDS
METHODS
Nitrate-Nitrogen 6-12/week
Nitrite-Nitrogen 6-12/week
Total Kjeldahl Nitrogen 2-4/month
Ammonia Nitrogen 1-2/month
Organic Nitrogen 1-2/month
Orthophosphate I/month
pH I/week
Alkalinity I/month
Dissolved Oxygen Daily
Suspended Solids I/week
Volatile Suspended Solids I/week
Methanol 3/week
Electrical Conductivity I/month
Chlorides as needed
Rhodamine B Dye
3/week
3/week
2-4/month
1-2/month
1-2/month
1/month
I/week
1/month
Daily
I/week
I/week
3/week
I/month
as needed
Specific Ion Electrode and Modified
Brucine
Diazotization, Standard Methods
12th Edition
Kjeldahl Method
Distillation Method
Kjeldahl Method
Modified Stannous Chloride
pH Meter Glass Electrode
Titration, Standard Methods
Winkler Method, Azide Modification
GFA Glass Paper, 103°C
GFA Glass Paper, 560-580°C
Gas Chromatograph, Carbowax Column
Conductivity Cell, Standard Methods
12th Edition
Silver Nitrate Titration, Standard
Methods, 12th Edition
Fluorometric Determination
-------
SECTION IV
RESULTS AND DISCUSSION
The primary objectives of Phase II prepilot scale studies to be
discussed in this report were to: (1) determine the effect of extended
operation on treatment efficiency, (2) further define the relationship
of detention time and temperature to nitrogen removal, (3) determine
the effect of periodic flushing of filters on nitrogen removal rate
and hydraulic regime, (4) determine the effect of seasonal variation of
influent nitrate-nitrogen, (5) refine preliminary cost estimates for
treatment facilities, and (6) refine design criteria for pilot plant
facilities. The Phase I results indicated uncovered ponds would not
meet required nitrogen removal efficiencies and studies were discontinued.
Anaerobic Denitrification Filters
Field evaluation of anaerobic denitrification filters was initiated
in October 1967 using 4-inch diameter PVC filters. Use of these small
filters was subsequently discontinued and the 18-inch diameter and
36-inch diameter filters were constructed to study start-up procedures,
temperature effects, nitrogen loading, long-term operation and filter
media. In May 1969, a pilot-scale unit 10 feet square and 6 feet deep
was built to study the effect of increased unit size and to further
study effects of temperature and long-term operation. Phase II studies
involved use of the 18-inch diameter and the pilot-scale units. The
medium used was one-inch rounded aggregate with the exception of one
unit which utilized artificial medium. Unless otherwise noted, this
discussion refers to units with the aggregate medium.
Temperature and Detention Time
Temperature changes, length of hydraulic detention time, and influent
nitrogen concentrations are major interrelated variables which affect
nitrate-nitrogen removal in anaerobic filters. As the temperature
decreased or the influent nitrogen concentration increased, longer
detention times were required to meet an effluent total nitrogen
criterion of 2 mg/1. In Phase I studies, it was demonstrated that when
water temperatures were in the range of 14° to 20°C a 1-hour detention
time was necessary to reduce an influent nitrate-nitrogen concentration
of 20 mg/1 to 2 mg/1 total nitrogen. When the water temperature dropped
to 12° to 14°C, a 2-hour detention was required to produce the same
water quality. In Phase II, the temperature-detention time relationship
was more complicated because the influent nitrate-nitrogen concentration
was varied to approximate concentrations expected in tile drainage.
Figure 2 illustrates the effect of detention time on nitrogen removal
throughout the year. In March when temperatures were approximately
14° to 16°C and the influent nitrate-nitrogen concentration was approxi-
mately 34 mg/1, a detention time of one hour will result in an effluent
-7-
-------
total nitrogen of about 22 mg/1, while the detention time would have
to increase to 6 hours to produce an effluent of 2 mg/1. In August,
with temperatures of 24° to 26°C and an influent nitrate-nitrogen of
14 mg/1, a one-hour or longer detention time produced effluent con-
taining a total nitrogen concentration of 2 mg/1. The curves shown
in Figure 2 are considered conservative in their depiction of removal
efficiency because they are based on averages which fluctuated daily.
For example, although in August the effluent nitrogen averaged 2.9 mg/1
with the detention time at one-half hour, in a significant number of
instances the nitrogen concentration was as low as 1.1 to 1.5 mg/1 at
this detention time. With better operational control, such as methanol
injection and its dispersion in the wastewater, the predicted detention
time requirement may be significantly reduced. In addition, the data
^cerebased on the theoretical detention time and not on actual detention
time. The actual detention was less than the theoretical detention
time due to reduced void volume caused by excessive bacterial mass as
shown in a latter section of this report.
An artificial medium, Koch FLEXIRINGS, was installed in an 18-inch
diameter filter in order to evaluate their effectiveness. The filter
was placed into operation in February 1970, however, consistent
nitrogen removal did not develop until June. A summary of results is
presented in Table 2. At water temperatures of 20° to 22°C, influent
nitrate-nitrogen concentrations of about 15 mg/1 were reduced to less
than 2 mg/1 total nitrogen at a 3-hour detention time. However, with
1 1
JANUARY FEBRUARY MARCH APRIL
JUNE
AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER
FIGURE 2- PREDICTED ANNUAL EFFECT OF DETENTION TIME ON TOTAL
EFFLUENT NITROGEN IN AGRICULTURAL TILE DRAINAGE
-8-
-------
TABLE 2
NITRATE-NITROGEN REMOVAL
ARTIFICIAL MEDIUM FILTER
EFFLUENT
DETENTION
TIME
(hrs)
4
4
3
3
3
3
3
6
6
8
8
TEMPERATURE
°C
22-24
24-26
22-24
24-26
20-22
20-22
18-22
16-18
14-16
12-14
10-12
TOTAL
INFLUENT
NITROGEN
(mg/1)
12.53
14.69
14.60
12.41
15.42
20.51
21.81
23.08
22.41
20.44
20.44
NITRATE
+
NITRITE
(ing /I)
1.77
.19
.53
.20
1.08
5.51
3.84
8.60
8.68
4.85
7.84
TOTAL
NITROGEN
(mg/1)
2.35
0.83
1.13
0.90
1.82
5.86
4.19
9.23
9.44
5.76
8.98
water temperatures between 18° to 22°C and an influent nitrate-nitrogen
concentration of about 22 mg/1, an effluent of 4.19 mg/1 was produced at a
3-hour detention time. At 10° to 12°C and an influent nitrate-nitrogen
concentration of 20 mg/1, an effluent of 8.98 mg/1 total nitrogen was
produced at an 8-hour detention time. The reason for the extended period
required to obtain the desired nitrogen reduction is not completely
understood, although it most likely was due to the low water temperatures
when first started. The physical characteristics, such as the configuration
and surface of the medium may have effected the bacterial buildup. In
general, the detention times required for denitrification were about twice
as long as were required with the use of 1-inch aggregate filters. However,
because the void volume is 96 percent for the artificial medium compared to
about 40 percent for 1-inch aggregate medium or about 2.4 times greater,
the actual hydraulic loading and nitrogen loading on :t--t> two media were
comparable.
-9-
-------
Organic Nitrogen and Ammonia
Concentrations of organic nitrogen and ammonia in the anaerobic filter
effluent are related to nitrogen loading and temperature. A portion of
the bacterial growth will be washed from the filter and the remaining
bacteria will eventually decompose and organic nitrogen and ammonia will
be released. In addition, any algae growth or suspended material
occurring in the drainage will be retained in the filter. Decomposition
of this material will increase organic nitrogen and ammonia in the
effluent. It has been shown that with the influent at an assumed
nitrate-nitrogen concentration of 20 mg/1, the nitrogen would be assimilated
and the production of cellular biomass would be 12.1 mg/1 (1). Effluent
volatile solids normally range from 2 to 6 mg/1 indicating a buildup of
organic matter within the filter. This organic matter decomposes and
is then removed in the effluent as ammonia. The effluent from filters
operated for less than one year normally varies seasonally from 0.8 to
1.5 mg/1 total Kjeldahl nitrogen. The effluent ammonia normally ranged
from 0.1 to 0.4 mg/1 ammonia-nitrogen or about 25 percent of the total
Kjeldahl nitrogen. The effluent from filters that were allowed to
operate without being disturbed for more than one year had effluent
Kjeldahl-nitrogen concentrations of up to 2.0 or 2.5 mg/1. The increase
which occurred at the higher water temperatures was due almost entirely
to increased ammonia-nitrogen from bacterial decomposition.
Flushing the filters to physically disrupt the bacteria resulted in an
increase in total Kjeldahl-nitrogen for a period of 10 to 40 detention
times following the disruption. This short-term increase in nitrogen was
in the organic form and varied from 0.5 mg/1 to 3.0 mg/1. Effluent from
units flushed at regular or irregular intervals were not characterized
by the higher ammonia-nitrogen concentrations experienced during warmer
temperature periods.
Organic Carbon Source
An organic carbon source is necessary for the dissimilatory nitrate-nitrogen
reduction process. Methanol was the source selected for the Interagency
Agricultural Wastewater Treatment Center. McCarty (3) evaluated acetic
acid, ethanol, acetone and methanol as organic carbon sources. He found
acetic acid to be the most efficient but also the most expensive of those
tried. Methanol and acetone were the least expensive, with overall results
favoring the use of methanol.
The consumptive ratio is defined as one obtained by dividing the actual
quantity of organic carbon source required to denitrify and deoxygenate
a waste plus the carbon required for cell growth by the stoichiometric
requirement for denitrification and deoxygenation of the waste (1). It is
used to quantify the carbon source needed to complete the denitrification
process. The original assumption for the consumptive ratio in the deni-
trification of tile drainage with methanol as the carbon source was 1.3.
Phase I studies found that the actual ratio was 1.47, with a standard
-10-
-------
deviation of +.36. This was based on a constant influent nitrate-nitrogen
concentration of 20 mg/1. With variable nitrate-nitrogen concentration
and temperature, the consumptive ratio varied as indicated in Figure 3.
At water temperatures between 18° and 24°C, the consumptive ratio for
an influent nitrate-nitrogen concentration of 25 mg/1 was about 1.2,
while at 15 mg/1, it was about 2.0. At temperatures below 16°C, the
increase in the consumptive ratio may be from 25 to 50 percent. The
seasonal variation in influent nitrate-nitrogen concentration and the
methanol concentrations required to denitrify the influent are shown in
Figure 4. The values for the consumptive ratio are generally higher
than expected for the denitrification process. These higher than normal
values may have'resulted when excess methanol in the system was consumed
through methane fermentation and thus not detected in the effluent.
Calculations of required methanol concentration were based on the assump-
tion that dissolved oxygen concentrations averaged 8.0 mg/1. This finding
may not be valid when drain waters are treated because algae growth in
the drainage canal may cause the water to contain a higher level of
dissolved oxygen.
The results of a study on the response of denitrifying bacteria to
changes in methanol addition are summarized in Figure 5. A filter
operated on a 1.5-hour theoretical detention time (65 minutes actual
detention time) was used to measure the effect of eliminating methanol
injection for approximately 4 detention periods and then returning the
filter to normal operation. The nitrate-nitrogen concentration of the
10
15 20
INFLUENT NITRATE-NITROGEN (mg/1)
FIGURE 3-CONSUMPTIVE RATIO AT DIFFERENT INFLUENT NITROGEN
CONCENTRATIONS AND TEMPERATURES
-11-
-------
PREDICTED NITRATE-NITROGEN CONCENTRATION
PREDICTED METHANOL CONCENTRATION REQUIREMENT
JANUARY FEBRUARY MARCH APRIL MAY JUNE JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER
FIGURE 4-SEASONAL VARIATION IN REQUIRED METHANOL INJECTION
AND INFLUENT NITRATE-NITROGEN CONCENTRATION
o
o
EFFLUENT NITRITE
MINUTES
FIGURE 5-NITRATE-NITROGEN REMOVAL RESPONSE TO METHANOL
INJECTION IN ANAEROBIC FILTERS
-12-
-------
influent to the filter was about 18 mg/1, the initial effluent nitrate-
nitrogen concentration was essentially zero, and the water temperature
was 22°C. Within minutes after turning off the methanol, a decrease
in nitrogen removal was evident at the first quarter-point sample port.
The decline became progressively evident throughout the filter. After
one detention time the effluent nitrate-nitrogen concentration stabilized
at about 9.5 mg/1 and remained at that concentration until the end of
four detention periods. The return to normal methanol injection resulted
in a return to zero nitrate-nitrogen in the effluent within one detention
period. The fact that about 60 percent of the influent nitrogen was
removed when the methanol supply to the filters was stopped indicated that
the denitrification process can still proceed for a period after the
organic carbon source injection is terminated. The continuation of this
dissimilatory process may be related to the endogenous respiration of the
bacteria. Another possibility is that the denitrification was brought
about in conjunction with the decay of bacteria.
Biomass Control
Short-term operation of anaerobic filters in Phase I studies indicated
that 1-inch diameter aggregate was a more suitable medium than was gravel
or sand because it was not readily plugged by bacterial cells. However,
if filters containing 1-inch aggregate were operated continuously for
more than one year, bacterial growth did significantly affect the
nitrogen removal efficiency. Increased total Kjeldahl-nitrogen in the
effluent, increased required influent pressure, and short-circuiting
through the filter indicated a significant bacterial buildup. Methods
which might kill the entire bacterial population, such as enzymes or
toxic materials, were not considered in that it was desirable to leave a
healthy seed to restart the unit. In Phase II, the problem of biomass
removal was solved by a systematic program designed to stabilize the
active bacterial population and maintain a constant usable void volume.
The method selected was one in which the filters were physically disturbed
but normal long-term filter operation was not disrupted.
The bacterial mass in the 18-inch filters was shaken loose with the use
of air injection for regular 15-minute periods at a rate of 0.6 standard
cubic feet per minute per square foot (scfm/ft^). The biomass was then
drained or flushed at intervals of 300, 600 or 1200 detention times.
Tracer studies were made before and after each flushing operation to study
the hydraulic regime. The filters were started and run for 8 months with
the interval flushings.
In analyzing the hydraulic tracer studies of the three flushing filters,
no definite conclusions can be made on the effect of the method used or
of the length of intervals between flushing. There were instances when
the hydraulic regime was definitely improved by removing a significant
amount of bacterial growth. On the other hand there were instances
when the hydraulics were impaired by a reduced plug flow and usable void
volume. In these cases it was assumed the bacterial mass was disturbed
-13-
-------
by the scour but not sufficiently removed from the filter by the flush.
In Phase I studies, operational problems due to accumulated bacterial
mass did not become noticeable until one year of continuous operation
was concluded. At least one year's operation appears necessary to
identify any significant results in nitrogen removal from flushing at
regular intervals.
Required pressure of influent water is directly related to an increase
in plugging by an accumulated mass of bacteria. Figure 6 indicated that
this pressure will be reduced by interval flushing. The filters showed
an immediate reduction in required influent pressure after flushing
followed by a rapid recovery during the next approximately 100 detention
times which in turn was followed by a leveling off of pressure.
6-
2-
18-INCH DIAMETER FILTER
WITHOUT FLUSHING
FILTER WITH FLUSHING EACH
600 DETENTION TIMES
-STATIC HEAD
5O
100
DAYS OF OPERATION
200
235
FIGURE 6-REQUIRED INFLUENT WATER PRESSURE TO FILTERS
WITH INTERVAL FLUSHING
There was a general increase of required pressure associated with
long-term operation. After 235 days of operation, the filter flushed
at 600 detention intervals was operating at pressures of 1 to 2 psi less
than the unit not flushed. Interval flushing at 1200 detention times
did not cause the reduction in pressures except for short periods following
the flushing.
With the exception of the recovery period after flushing, no significant
change in nitrogen removal efficiency was noted between filters. The
recovery period, as shown in Figure 7 with representative examples, varied
from several days at temperatures of 18° to 24°C to about two to four
weeks at temperatures below 18°C. The restarting process usually involved
increasing the detention time to four times as long as that in normal
operation, and then reducing it in stages when satisfactory nitrate-nitrogen
removal efficiency had again been attained. There were several occasions
when the detention time was not varied from the operating detention and
-14-
-------
the filter regained acceptable nitrogen removals within reasonable
time periods. During the 235 day period no difference was noted in
total Kjeldahl nitrogen for filters operated the same length of time and
either not flushed or flushed at intervals. As stated in the Phase I
report, long-term operation without disturbing the filter can result in
increases of ammonia-nitrogen up to 2.5 mg/1 at the higher temperatures.
If the unit had been flushed, effluent ammonia-nitrogen concentrations
were rarely above 0.2 or 0.3 mg/1 during the summer months.
The pilot-scale filter unit was flushed several times in the fall between
days 529 and 555 in response to the deterioration of the hydraulics caused
by accumulation of biomass. This unit had last been flushed in March
at day 311. Several rates of air injection were tried along with either
draining the filter or increasing the water flow through the unit. The
initial air injection was 0.5 scfm/ft2 and increased in several stages to
10 scfm/ft2. Between each air injection and flushing the filter was
operated at least 5 days to evaluate pressures and hydraulic regime. By
observation, 10 scfm/ft2 of air applied in diffusers spaced 5 feet on
center was required to thoroughly scour the medium. Large masses of
bacteria were forced to the top of the unit and removed by water flowing
through the unit. It was also observed that the smooth sidewalls of
the filter unit allowed significant amounts of water or air to flow
unrestricted up the sides. The overall effect would be reduced as unit
size increased and would probably be remedied by incorporating a roughly
textured surface or a system of baffles.
... EFFLUENT
I/I NITRITE-NITROGEN
INFLUENT NITRATE-NITROGEN
U 3-HOUR *T*- 1.5-HOUR DETENTION TIME -»
• EFFLUENT NITRATE-NITROGEN
-EFFLUENT NITRITE-NITROGEN
0 5 10 15
DAYS OF OPERATION AFTER FLUSH
(WATER TEMPERATURE AT IO°-I2°C)
05 10 15
DAYS OF OPERATION AFTER FLUSH
(WATER TEMPERATURE AT 2Z°-24°C)
FIGURE 7-FILTER RECOVERY AFTER BACTERIAL REMOVAL AT INTERVALS
-15-
-------
In Figure 8 are plotted results of tracer studies performed on the
pilot-scale filter which indicate the effect of biomass buildup and
flushing. The analyses for days 311 and 406 bracket the flushing of day
318, while those on days 537 and 563 bracket the flushing on day 555. In
each case the curve was shifted to the right of the preceding curve,
which indicated a decrease in stagnant or plugged void volume and
improved hydraulics of the unit resulting from the flushing. However,
the gradual shift to the left shown by the curves for days 161, 406, and
563 indicates a gradual increase in plugging not completely removed by
vigorous flushing methods.
Due to seasonal variations of San Joaquin tile drainage and climatic
conditions, the greatest demand for treatment units is in the spring,
while during the summer and into the fall the demand is down resulting in
a reduction of filter units needed. Rather than having frequent scheduled
flushings, the filter units might annually be taken out of service for
several months at the slack period. At this time, a program of removing
all or a large part of the bacterial mass could be used and the units
could then be restarted during the period of warmer water temperatures.
Scale-up Factors
The major unknowns in the treatment of tile drainage by the anaerobic
filters at this time are the problems to be encountered in the operation
of a full-scale treatment unit. Such units may have a surface area of
about 40,000 square feet or nearly one acre. Data on the units tested
at the Interagency Agricultural Wastewater Treatment Center show that
a major problem in operating a full-scale plant will be to maintain the
desired hydraulic characteristics within the filter. If this problem
could be solved, then the nitrogen removal efficiencies and required
detention times determined by the pilot-scale studies could be extrapolated
to a full-scale treatment facility. The anaerobic denitrification process
itself is not affected by the size of the unit. Extensive profiles of
units of the various sizes indicate no differences in the manner in which
the nitrate is reduced to nitrites and then to gaseous nitrogen.
The pattern of accumulation of bacterial mass at the bottom of the filter
with the greatest nitrogen removal in this area is not altered in the
larger unit. In the larger units, even though they contain undoubtedly
larger stagnant areas in which decomposition may occur, ammonia-nitrogen
concentration (an indicator of bacterial decomposition) indicates no
difference between the performance of the various sized units. There is
no significant difference between the concentrations in the effluent of
total Kjeldahl nitrogen or of suspended and volatile solids of the
effluents from different size units.
The main problem in the operation of the large-scale anaerobic filters
will be in maintaining a desirable hydraulic regime within the unit.
Because of the confined volume of the smaller unit and the characteristics
of the bacterial growth, required influent pressures become less as the
-16-
-------
ANALYSIS AFTER 161
DAYS Of OPERATION
0.5 1.0 1.5
THEORETICAL DETENTION TIMES
t.O
FIGURE 8-RESULTS OF HYDRAULIC TRACER STUDIES
PERFORMED ON PILOT SCALE FILTER
-17-
-------
unit size increases. In the larger units the required pressure probably
would not exceed 6 pounds per square inch even if the unit were only
flushed annually. The lower required operational pressure was verified
in the pilot-scale unit. With less confinement or control of the flow
through the filter, more short-circuiting or following of paths of least
resistances took place.
The elimination of short-circuiting will depend on the ability to control
or remove the bacterial masses. As described in the section on biomass
control, air scrubbing, in conjunction with or followed by flushing with
water, now appears to be the best method to remove excess biomass. With
the larger units this process becomes more difficult. In the 18-inch
diameter unit with its confining side walls, it appears about 0.5 to 1.0
scfm/ft^ of air appears to be sufficient to break the bacteria loose
from the medium. However, in the pilot-scale unit, about 10 scfm/ft^
of air was necessary to give an even flow distribution. The air was
injected in the diffusers located about 5 feet on center in the pilot-size
unit. In a larger unit it might be necessary to decrease the distance
between the diffusers or increase the air injection rate. The larger
exposed area of the pilot-scale unit necessitated a greater input of air
per unit volume of filter than needed in the smaller unit because of their
closely confined exposed area. It should be noted that the pilot-scale
unit was not regularly flushed. It was approximately 2800 detention times
between flushing.
Study of larger units points to operational advantages of artificial medium
over aggregate. At this time the high cost of artificial media would
eliminate it from consideration. However, with more detailed studies on
the artificial medium than were conducted at the Interagency Agricultural
Wastewater Treatment Center, operational controls could be refined to
bring it more in line with aggregate medium.
Phosphorus
Based on the empirical chemical formulation of CcHyC^N for bacterial cells,
the nitrogen requirement is about 12 percent of the biological solids
produced. The phosphorus requirement of facultative bacteria is reported
to be about 2 percent of the solids weight (5). Thus if 12.1 mg/1 of
biological growth is produced at an influent concentration of 20 mg/1
nitrate-nitrogen (1), then about 1.1 mg/1 of nitrate-nitrogen and 0.24 mg/1
of phosphorus are assimilated in the growth process. The theoretical
ratio of required phosphorus to the influent total nitrogen, 1 to 84, is
plotted in Figure 9 along with actual influent phosphorus. The influent
phosphorus averaged about 0.09 mg/1, ranging from 0.0 mg/1 to .19 mg/1
and was only 10 to 30 percent of the theoretical required phosphorus.
Effluent phosphorus normally ranged from 0.0 mg/1 to 0.05 mg/1, with a
major portion of the concentrations approximating 0.0 mg/1. Actual phospho-
rus consumption averaged about 0.08 mg/1, which is significantly less than the
estimated requirement. It is entirely possible that the bacteria were
lacking phosphorus for their assimilatory processes. However, the.filters
were capable of denitrifying all the nitrate-nitrogen present, which indicates
-18-
-------
JANUARY FEBRUARY ^ MARCH APfilLMAY
FIGURE 9-THEORETICAL PHOSPHOROUS CONCENTRATION REQUIREMENT AND
ACTUAL INFLUENT PHOSPHOROUS CONCENTRATION FOR FACULTATIVE BACTERIA
that the bacteria were able to function without the theoretical phosphorus
requirement. A possible source of phosphorus may be recycled from decom-
posing bacteria. The limiting effect of low phosphorus concentration may
have masked the effect of some other parameter such as temperature or
detention time.
Filter Media
A primary objective of Phase I was to determine under field conditions
the best medium for anaerobic denitrification filters. Media evaluated
included activated carbon, sand, rounded aggregate, angular bituminous
coal, volcanic cinders, and Dow SURFPAC. The texture and the sorptive
quality of the medium surface did not appreciably affect removal
efficiencies. In addition, no significant difference was noted in com-
paring efficiencies of filters containing media less than one inch in
diameter and 1-inch diameter media. When operated for more than several
months, these small-media units were plagued with poor hydraulics and
pressure buildups that adversely affected efficiency. Aggregate media
with diameters greater than one inch apparently did not have enough
surface area to support a sufficient bacterial population. Dow SURFPAC,
because of its open design did not allow sufficient bacterial mass to
accumulate (1). Phase II research concentrated on filters with 1-inch
aggregate. Several units were operated continuously from Phase I to give
information on long-term operations. Other filters started during the
year were used mainly to provide additional data on operations.
-19-
-------
Early results from Phase I indicated that 1-inch aggregate medium would
be best mainly because bacterial plugging did not occur as had been the
case with small media. With long-term operation, i.e., longer than 12
months, bacterial plugging did occur to the detriment of the filter
efficiency. As indicated in Figure 10, after 17 months of continuous
operation with the 18-inch filter at 2 hours detention time, approximately
34 percent of the filter volume was stagnant. With 23 months of operation,
60 percent was stagnant. The stagnant zones appeared to increase each
month from 21to 2.5 percent of the total void volume.
With the progressive increase in volume of stagnant zones, the hydraulics
of the unit deteriorated as was indicated by an increased mixed flow, a
decreased plug flow, and drop in filter efficiency. Filter back pressure
gradually built up to approximately 11 psi; however, pressures did not
appear to be the problem that they were in media less than one-inch in
diameter, where pressures exceeded 70 psig for the activated carbon medium
and 30 psig in sand medium.
Two artificial media, Dow SURFPAC and Koch FLEXIRINGS, were selected for
evaluation because their surface area and void volume were greater than
those in the aggregate media (Table 3). Due to the larger void volume,
the SURFPAC and the FLEXIRINGS required detention time at least two to
eight times longer than did the 1-inch aggregate medium for the same
level of nitrogen removed. The reason for the slower nitrogen removal
was the larger void volumes in relation to effective surface area. The
open design of the SURFPAC did not allow bacterial growth to accumulate
sufficiently because of sloughing that occurred. At 16-hours detention
TABLE 3
CHARACTERISTICS OF FILTER MEDIA
MEDIUM
SURFACE AREA
VOID VOLUME
1-inch aggregate
2-inch aggregate
Koch FLEXIRINGS, 1-inch
Dow SURFPAC
6.7
8.7
65.0
26.5
.40
.40
.96
.94
-20-
-------
0.5 1.0 1.5
THEOKCTICAL DETENTION TIMES
t.O
FIGURE 10. HYDRAULIC TRACER RESULTS FOR THE
2-HOUR DETENTION FILTER
-21-
-------
time and a loading rate of 2.4 gal/ft2/hr, the SURFPAC removed about 86
percent of the influent nitrogen compared to removal rates averaging 94
percent with the use of 1-inch aggregate medium at a 2-hour detention
and a hydraulic loading of 8.6 gal/ft2/hr. The FLEXIRINGS had a surface
area of 65 ft2/ft3 as compared to 26.5 ft /ftJ for SURFPAC. In addition,
the design of the FLEXIRINGS eliminated the direct flow-through experi-
enced in the SURFPAC. Within the 20° to 24°C temperature range, at a
3-hour detention time and a loading rate of 12.6 gal/ft2/hr, the
FLEXIRINGS removed 91 percent of the influent nitrogen. At the same
water temperature a 1.5-hour detention and 11.9 gal/ft2/hr loading rate,
the 1-inch aggregate removed 90 percent of the influent nitrogen.
The start-up of the FLEXIRINGS filter with inoculum from another filter
took about 120 days before consistently high nitrate-nitrogen removal
rates were obtained at the shorter detention times. This was considerably
longer than was the case when the filters containing aggregate media
were used. The long start-up may have been due to the fact that the
smooth surface of the PVC material may have failed to provide a good
surface for bacterial attachment. About 150 days elapsed before any
significant increase in influent pressure was observed. The pressure
then gradually increased, but did not exceed 6 psig during the 400 days
of operation. The increase in pressure coincided with an improvement in
nitrogen removal.
Anaerobic Covered Deep Pond
Field evaluation of anaerobic denitrification in large-scale ponds was
begun in September 1968 during Phase I. This research indicated that the
deep covered pond with a 15-day detention time could meet the effluent
criteria of 2 mg/1 total nitrogen when water temperatures were between
14°C and 22°C. Uncovered deep ponds were eliminated from further study
because the difficulty of maintaining anaerobic conditions prevented
them from meeting the effluent criteria. In Phase II, the covered pond
was evaluated with the objective of refining operational procedures and
determining removal efficiencies at various detention times when the
temperatures were below 14°C. A further objective of the Phase II
pond denitrification studies was to maintain the effluent total nitrogen
at 2 mg/1 or less by adjusting the hydraulic detention time to allow
for changes in nitrogen loading and prevailing or anticipated environmental
conditions.
Summary of Operation
The covered pond was placed on a continuously mixed flow-through operation
with a 20-day detention time in March 1969. The detention time was pro-
gressively lowered to 15-day, 10-day and finally to a 7.5-day detention
period to match the water temperature increase during summer months and
the maintenance of the effluent total nitrogen at 2 mg/1 or less. At the
7.5-day detention time, the average effluent total nitrogen increased to
approximately 4 mg/1. During the fall the detention time was lengthened
-22-
-------
ro
u<
I
TABLE 4
SUMMARY
OPERATION AND EFFLUENT NITROGEN CONCENTRATION FOR THE COVERED DEEP POND
DAYS OF
OPERATION
0-27
28-39
40-62
63-97
98-124
125-166
and
187-197
167-186
198-218
219-249
250-260
261-268
270-281
281-315
315-345
345-417
417-440
440-469
469-501
501-547
548-564
564-589
589-602
602-618
618-646
646-705
705- 715
715-736
THEORETICAL
AVERAGE EFFLUENT NITROGEN CONCENTRATION
HYDRAULIC WATER AVERAGE INFLUENT
DETENTION TEMP. NITRATE-NITROGEN NITRATE-NITRITE
(day) (°C) (me/1) (mR/l) *
20
15
15
15
15
10
7.5
10
10
10
10
15
20
33.5
20
15
10
10
10
15
30
30
48
60
45
30
14-16
14-16
16-18
18-20
20-22
20-22
20-22
18-20
16-18
14-16
12-14
12-14
10-12
12-14
12-14
14-18
18-20
20-22
20-22
20-22
20-22
20-22
18-20
14-18
10-12
12-14
12-14
20
20
20
20
20
20
20
20
20
20
20
20
32
31
33
—
16
14
12
14
25
25
27
24
31.5
26.9
35
1.05
0.51
0.35
1.08
.54
.29
2.48
1.39
3.03
2.44
6.83
(7.5)
17.42
3.08
3.86
—
(.2)
.27
(.2)
(.2)
.99
3.47
5.72
3.29
4.0
0.8
(0.4)
TOTAI NITROGEN
(mg/l) *
2.00
1.96
1.42
2.58
1.80
1.49
3.79
2.57
4.19
3.73
7.79
(9.0)
17.10
4.52
5.26
—
(1.5)
1.17
(1.5)
(1.5)
2.24
4.49
6.9
4.44
5.1
2.2
(1.6)
TOTAL
NITROGEN REMOVED REMARKS
(%)
90
90
92
87
91
92
86
92
79
82
61
55
47
85
84
91
87
87
89
91
82
71
82
84
92
93
End Phase I
Begin Phase II
No flow thru operation
No recirculatlon
No recirculatlon days
580 to 589
Numbers in parenthesis are approximate
-------
to 10 days and eventually to 15 days as the water temperature fell below
18°C. Throughout the winter months the effluent criterion of 2 mg/1 was
not met, although there were indications that it could be met at longer
detentions. Low water temperatures prevented the pond from regaining
the desired removal efficiency at a 33-day detention until March.
Through 1970, the detention time was adjusted to maintain effluent nitrogen
at 2 mg/1 or less, while the influent nitrate-nitrogen was varied to
approximate predicted tile drain flows.
Effect of Temperature and Detention Time on Nitrogen Removal
Nitrogen removal efficiency in covered ponds is affected mainly by tem-
perature and detention time. Because most of the bacterial cells are not
retained in the system, much longer detention times are required to
produce a sufficient bacterial mass. To meet the effluent criterion
throughout the year, detention times ranging from 8.9 days to 60 days were
required. The relationship between effluent nitrogen, temperature, and
detention time in covered ponds is indicated by the data presented in
Table 4. Nitrogen effluents of less than 2 mg/1 were obtained at 18°C to 22°C
and a detention time of 10 days. During the cooler months, when the water
temperatures were below 18°C and influent nitrogen concentrations were
25 to 35 mg/1, the average effluent nitrogen concentration ranged from
2 to 5 mg/1. However, at the lower water temperatures, nitrogen removal
was up to 30 mg/1 as compared to 10 to 12 mg/1 during times when the water
temperatures were warmer. Influent nitrogen loading in pounds per 1000
cubic feet of pond ranged from 0.03 pound per day at 48 days detention
to 0.10 pounds per day at 10 days detention.
Nitrate-nitrogen and organic nitrogen were the major components of the
total nitrogen present in the covered pond effluent. Nitrite-nitrogen
concentrations were normally less than 0.5 mg/1. Total Kjeldahl nitrogen,
which normally varied between 1.0 mg/1 and 2.0 mg/1, was predominately
organic in nature, with little or no ammonia-nitrogen. The absence of
ammonia-nitrogen in the effluent indicated that the bacterial growth was
being washed out of the unit before significant decomposition could occur.
Moore and Schroeder (6) stated the rate of nitrite reduction is slower
than that of nitrate and showed that in a mixed system with continuous
flow, nitrite will not accumulate and will be less than the nitrate con-
centration. This was verified in Phase I and II, as nitrite was essentially
absent in the covered pond effluent when the nitrogen removal efficiency
was high. In the instances where the level nitrite-nitrogen reached 2 to
10 mg/1, operational problems generally had occurred.
As noted earlier, the nitrogen concentration and flow rates from the
tile drainage will vary seasonally. Fortunately, the longer required
detention times will coincide with the low flows and the shorter detention
times with the higher flows. Figure 11 presents the predicted detention
times in covered ponds required for denitrification of agricultural tile
drainage from the San Joaquin Valley at the various nitrate-nitrogen
concentrations to be encountered.
-24-
-------
o
>-30.
020-
UJ
-------
o
7.5 DAYS THEORETI
DETENTION TIME
10 DAYS THEORETICAL
DETENTION TIME
10 DAYS THEORETICAL
DETENTION TIME
NO R€CIRCULATION
0.3 1.0 1.5
THEORETICAL DETENTION TIMES
2.0
FIGURE 12. HYDRAULIC TRACER RESULTS FOR THE
COVERED DEEP POND
-26-
-------
The hydraulic tracer studies, along with occasional temperature profiles
and weekly nitrate, nitrite and solids profiles, indicate that the pond
was normally an almost completely mixed system. There were instances in
which distinct stratifications appeared in the nitrate-nitrite on tem-
perature profiles which suggest plug flow. These cases of stratification
may have been caused by temperature differences between the pond and
influent waters.
Recirculation
Because of the small amount of cell production which occurs during
bacterial denitrification, recirculation of a portion of the total flow
was used to seed the influent to the covered pond with active bacterial
mass. If recirculation were eliminated, a reduction in capital cost
for pumps and operation cost could be realized. With the exception of
a short period during late summer, recirculation was used in the covered
pond. At that time, the effluent total nitrogen was about 1.2 mg/1 with
nitrate-nitrogen and nitrite-nitrogen essentially zero. On day 501 of
operation, with water temperatures at about 22.5°C and the detention
time at 8.9 days, recirculation was withheld for about six detention
times. No significant change was noted in the effluent nitrate, nitrite,
or total Kjeldahl nitrogen for several detention times. Nitrate-nitrogen
increased slightly at the influent end of the pond but at the middle of the
pond this had fallen to zero. However, as the water temperature in the
pond dropped below 21°C, the effluent nitrate-nitrogen plus nitrite-nitrogen
increased slowly to 1.5 mg/1 and total nitrogen rose to 2.7 mg/1. At this
time, the recirculation was restored. Following resumption, the effluent
nitrate-nitrogen showed decrease to about 0.5 mg/1 within 10 days.
At a time when the water temperature was about 18°C and the pond was on
a 15-day detention time, the recirculation pump was not operational for
about 10 days. During this time the total effluent nitrogen jumped from
about 2 mg/1 to 5.5 mg/1. When the pump was restarted, the nitrate
profiles of the pond showed a reduction in nitrates within several days,
and within 10 days the effluent total nitrogen was down to 2.5 mg/1.
It appears that denitrification can be achieved with the necessary
efficiency without recirculation if the detention period is sufficiently
long. Because essentially no nitrates or nitrites occurred in the effluent
when recirculation was suspended at the 8.9 day detention, a shorter
detention with recirculation might have been sufficient. During cold
water temperature periods, with a much slower growth rate of the bacteria,
a much longer detention time without recirculation would undoubtedly be
needed as opposed to the approximate 60 days needed with recirculation.
-27-
-------
Recommended Design and Cost Estimates
Results of Phase II indicate that only minor changes should be made in
the design criteria and operations of anaerobic filters and ponds as
presented in the Phase I report. These changes did not justify a
reevaluation of the cost estimates. Cost estimates from Phase I indicate
that denitrification by a plant operated at full capacity would cost
$92 per million gallons for anaerobic filters and $88 per million gallons
for covered ponds. The preliminary cost estimates were considered con-
servative and refinement of these estimates would most likely reduce the
expected treatment costs. Cost reductions of 20 to 25 percent might be
realized by designing a treatment system with a capability to store the
tile drainage during seasonally high flows and provide treatment when
higher water temperatures permit higher loadings to the units.
The changes in design and operational criteria for the anaerobic filter
are due to changes in biomass removal procedures. The filter box wall
height would be reduced from 14 feet to 6 feet because it was felt that
the extra hydraulic head was not necessary in the flushing operation. A
more extensive air injection system is needed with the full-size unit
divided into modules of approximately 40 feet square. No changes are
suggested for design and operational criteria of denitrification in
covered ponds.
-28-
-------
SECTION V
ACKNOWLEDGMENTS
Phase II of the field investigations concerned with bacterial denitri-
fication of tile drainage was performed under the joint direction of
Messrs. Donald G. Swain, Sanitary Engineer, U. S. Bureau of Reclamation;
Bryan R. Sword, Sanitary Engineer, Environmental Protection Agency; and
Douglas L. Walker, Civil Engineer, California Department of Water
Resources.
The field work and this report were the responsibility of James R. Jones,
Sanitary Engineer, U. S. Bureau of Reclamation. The cooperation and
assistance given by the interagency staff of the treatment center and
the consultants to the project were major contributions to the success
of the studies. These personnel were:
Bruce A. Butterfield Engineer, Department of Water Resources
James F. Arthur Biologist, Environmental Protection Agency
Robert G. Seals Chemist, Environmental Protection Agency
William L. Baxter Technician, Department of Water Resources
Dennis L. Salisbury Technician, Department of Water Resources
Gary E. Keller Technician, U. S. Bureau of Reclamation
Norman W. Cederquist Technician, U. S. Bureau of Reclamation
Clara P. Hatcher Laboratory Aid, Department of Water Resources
Elizabeth J. Boone .... Laboratory Aid, Department of Water Resources
Consultants to the Project
Dr. Perry L. McCarty Stanford University, Stanford
Dr. William J. Oswald University of California, Berkeley
Dr. Clarence G. Golueke University of California, Berkeley
-29-
-------
SECTION VI
REFERENCES
1. Sword, B. R., "Denitrification of Agricultural Tile Drainage in
Anaerobic Filters and Ponds", Agricultural Wastewater Study Group,
April 1971, 13030 UBH-4/71.
2. Glandon, L. R., "Nutrients from Tile Drainage System", California
Department of Water Resources, Bulletin No. 174-6 (To be published),
3. McCarty, P. L., "Feasibility of the Denitrification Process for
Removal of Nitrate-Nitrogen from Agricultural Drainage Waters",
Appendix California Department of Water Resources Bulletin No.
174-3 (June 30, 1966).
4. Milburn, W. F., "A Development and Evaluation of Theoretical Model
Describing the Effects of Hydraulic Regime in Continuous Microbial
Systems", a dissertation presented to Northwestern University at
Evanston, Illinois, in 1964 in partial fulfillment of the
requirements for the degree of Doctor of Philosophy.
5. McCarty, Perry L., "Anaerobic Waste Treatment Fundamentals", Parts
1 thru 4, Public Works, September thru December 1964.
6. Schroeder, Edward D. and Moore, Stephen F., The Effect of Nitrate
Feed on Denitrification, (1969).
-31-
-------
SECTION VII
PUBLICATIONS
SAN JOAQUIN PROJECT, FIREBAUGH, CALIFORNIA
1968
"Is Treatment of Agricultural Waste Water Possible?"
Louis A. Beck and Percy P. St. Amant, Jr. Presented at Fourth
International Water Quality Symposium, San Francisco, California.
August 14, 1968; published in the proceedings of the meeting.
1969
"Biological Denitrification of Wastewaters by Addition of Organic
Materials"
Perry L. McCarty, Louis A. Beck, and Percy P. St. Amant, Jr.
Presented at the 24th Annual Purdue Industrial Waste Conference,
Purdue University, Lafayette, Indiana. May 6, 1969.
"Comparison of Nitrate Removal Methods"
Louis A. Beck, Percy P. St. Amant, Jr., and Thomas A. Tamblyn.
Presented at Water Pollution Control Federation Meeting, Dallas,
Texas. October 9, 1969.
"Effect of Surface/Volume Relationship, C02 Addition, Aeration, and
Mixing on Nitrate Utilization by Scenedesmus Cultures in Subsurface
Agricultural Waste Waters"
Randall L. Brown and James F. Arthur. Proceedings of the
Eutrophication-Biostimulation Assessment Workshop, Berkeley,
California. June 19-21, 1969.
"Nitrate Removal Studies at the Interagency Agricultural Waste Water
Treatment Center, Firebaugh, California"
Percy P. St. Amant, Jr., and Louis A. Beck. Presented at 1969
Conference, California Water Pollution Control Association,
Anaheim, California, and published in the proceedings of the
meeting. May 9, 1969.
"Research on Methods of Removing Excess Plant Nutrients from Water"
Percy P. St. Amant, Jr., and Louis A. Beck. Presented at 158th
National Meeting and Chemical Exposition, American Chemical
Society, New York, New York. September 8, 1969.
"The Anaerobic Filter for the Denitrification of Agricultural
Subsurface Drainage"
T. A. Tamblyn and B. R. Sword. Presented at the 24th Purdue
Industrial Waste Conference, Lafayette, Indiana. May 5-8, 1969.
-33-
-------
SAN JOAQUIN PROJECT, FIREBAUGH. CALIFORNIA (Continued)
1969
"Nutrients in Agricultural Tile Drainage"
W. H. Pierce, L. A. Beck and L. R. Glandon. Presented at the
1969 Winter Meeting of the American Society of Agricultural
Engineers, Chicago, Illinois. December 9-12, 1969.
"Treatment of High Nitrate Waters"
Percy P. St. Amant, Jr., and Perry L. McCarty. Presented at
Annual Conference, American Water Works Association, San Diego
California. May 21, 1969. American Water Works Association
Journal. Vol. 61. No. 12. December 1969. pp. 659-662.
The following papers were presented at the National Fall Meeting
of the American Geophysical Union, Hydrology Section, San Francisco,
California. December 15-18, 1969. They are published in Collected
Papers Regarding Nitrates in Agricultural Waste Water. USDI, FWQA,
#13030 ELY December 1969.
"The Effects of Nitrogen Removal on the Algal Growth Potential of
San Joaquin Valley Agricultural Tile Drainage Effluents"
Randall L. Brown, Richard C. Bain, Jr., and Milton G. Tunzi.
"Harvesting of Algae Grown in Agricultural Wastewaters"
Bruce A. Butterfield and James R. Jones.
"Monitoring Nutrients and Pesticides in Subsurface Agricultural
Drainage"
Lawrence R. Glandon, Jr., and Louis A. Beck.
"Combined Nutrient Removal and Transport System for Tile Drainage
from the San Joaquin Valley"
Joel Goldman, James F. Arthur, William J. Oswald; and Louis
A. Beck.
"Desalination of Irrigation Return Waters"
Bryan R. Sword
/
"Bacterial Denitrification of Agricultural Tile Drainage"
Thomas A. Tamblyn, Perry L. McCarty and Percy P. St. Amant.
"Algal Nutrient Responses in Agricultural Wastewater"
James F. Arthur, Randall L. Brown, Bruce A. Butterfield, Joel
C. Goldman.
-34-
-------
1
Accession Number
w
2
Subject Field & Croup
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Title
Water Quality Office
Environmental Protection Agency
Washington, D.C.
DENITRIFICATION BY ANAEROBIC FILTERS AND PONDS ~ PHASE II
10
Avthorfe)
Jones, James R.
16
Project #13030 ELY
Noto
22
Citation
Bio-Engineering Aspect of Agricultural Drainage
Report Number #13030 ELY 06/71-14
Pages 34 Figures 12 Tables 4 References 6
23
Descriptors (Starred First)
*Agricultural Wastes, *Denitrification, *Irrigation Water, Return Flows,
Nitrate, Anaerobic Treatment'
25
Identifiers (Starred First)
*San Joaquin Valley, California, Bacterial Denitrification, Anaerobic Filters,
Anaerobic Ponds
Abstract..
Operational criteria, design and operations costs for a treatment facility to
remove nitrogen from agricultural tile drainage in the San Joaquin Valley were further
investigated during 1970 at the Interagency Agricultural Wastewater Treatment Center near
Firebaugh, California. The year-long study period is identified as Phase II. Based on
projected nitrate-nitrogen concentrations for valley tile drainage water, the research in
this phase extended earlier Phase I studies on the feasibility of bacterial denitrification
by filters and covered ponds. The anaerobic filter with 1-inch rounded aggregate was
capable of reducing influent nitrate-nitrogen from 30 mg/1 to 2 mg/1 at water temperatures
from 12° to 16°C at a 6-hour detention time, and from 15 mg/1 to 2 mg/1 at water temper-
atures of 20° to 24°C at 1-hour detention time. Long-term operation of filters resulted in
accumulation of bacterial mass which caused the deterioration of the hydraulic regime and
nitrogen removal efficiencies. Air scour accompanied or followed by flushing with water was
capable of controlling the bacterial mass. The consumptive ratio, a method to quantify the
organic carbon source needed for anaerobic bacterial process, was affected by temperature
and influent nitrogen concentration and was found to vary between approximately 1.2 and 2.4.
The anaerobic covered pond reduced influent nitrate-nitrogen from 30 mg/1 to 2 mg/1 at
water temperatures of 12° to 16°C with a 60-day detention time and from 15 mg/1 to 2 mg/1
at 20° to 2-°C with a 10-day detention time.
This report is submitted in partial fulfillment of Project No. 13030ELY under
the sponsorship of the Environmental Protection Agency
Abstractor
Institution
J. R.
Environmental Prnl-prt.inn
WR:I02 (REV. JUUY '969)
WRSI C
SEND WITH COPY OF DOCUMENT. TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
* U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 2C240
CPO: 1970 - 407 -B9I
U. S. GOVERNMENT PRINTING OFFICE : 1972-514-148/68
------- |