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

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     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".

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           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

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             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.

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                              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

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                               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.

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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

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                               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

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                                 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

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                                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

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                              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—

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                         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-

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                             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-

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                             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

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                                                 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

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                               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-

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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-

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                                 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-

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 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-

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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-

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                                  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-

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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-

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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-

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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-

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 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-

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                              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-

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 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-

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      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-

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             0.5        1.0        1.5

            THEOKCTICAL DETENTION TIMES
t.O
FIGURE 10. HYDRAULIC TRACER RESULTS FOR THE
          2-HOUR DETENTION FILTER
                     -21-

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 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-

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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

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 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-

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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-

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                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-

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                              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-

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                              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-

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                              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-

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 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-

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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

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