NITRIFICATION AND DENTTRJFICATTON OF WASTE WATER
                     Final Report
Investigation Sponsored by  Research Grant Number WP 01028
            Environmental Protection Agency
         Federal Water Quality Administration
                       by
       Walter K. Johnson, Principal Investigator

                         and

                   Oeorge B. Vania




       Sanitary Engineering Report Number 175 S

                   January 1, 1971
             Sanitary Engineering Division
      Department of Civil and Mineral Engineering
               Institute  of Technology
               University of Minnesota
               Minneapolis, Minnesota
                   January 1971

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    NITRIFICATION AND DENITRIFICATION OF WASTE WATER
                     Final Report
Investigation Sponsored by Research Grant Number WP 01028
            Environmental Protection Agency
         Federal Water Quality Administration
                        by
        Walter K. Johnson, Principal Investigator

                          and

                    George B. Vania




        Sanitary Engineering Report  Number 175 S

                    January 1, 1971
              Sanitary Engineering Division
       Department of Civil and Mineral Engineering
                Institute of Technology
                University of Minnesota
                Minneapolis, Minnesota
                     January 1971

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                            ACKNOWLEDGEMENT



This project was supported by Research Grant Number  TCP 01028 from the

Brvironmental Protection Agency, Federal Water Quality Administration.

Special appreciation is extended to the Metropolitan Sewer Board for

the use of facilities and assistance from personnel at the Minneapolis-

St.Paul Wastewater Treatment Plant.

Students at the University of Minnesota who participated in the project

included:
          Bruce Bonde                           George Kriha
          Wallace Borene                        Loren Leach
          Leon Flemembaum                       Ching Wu
          Brian Ireeberg

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                            TABLE OF CONTENTS
I.    NEED FOR NITROGEN REMOVAL                                       1

II.   DEVITRIFICATION PROCESS FOR NITROGEN REMOVAL                    2

      A.  Description of Process                                      2

      B.  Kinetics of the Denitrification Process                     2

          1.  Development                                             2

          2  Oxygen Equivalent Available from Nitrates               6

          3.  Yield                                                   6

          4.  Growth Rate                                             7

          5  Oxygen Equivalent Required Per Unit of Substrate
                Removed                                               8

          6*  Endogenous Coefficients                                 9

          7.  Rate of Nitrate Reduction                               9

          8*  Ratioss Substrate Metabolized/Nitrate Reduced          10

          9  Example of Use of Kinetic Equations                    12

      C.  Process Economics                                          14

III.  EXPERIMENTAL RESEARCH PROGRAM                                  15

IV.   ANALYTICAL PROCEDURES                                          16

      A*  General                                                    16

      B.  Mxed Liquor Suspended Solids                              16

      C.  Dissolved Oxygen                                           16

      D.  Nitrate Nitrogen                                           16

      E.  Total Phosphorus                                           16

V.    REA.CTOR TESTS                                                  17

      A*  General Conditions                                         17

      B.  Equipment                                                  17
                                   iii

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C,  Procedures                                                 18



    1.  General                                                18



    2.  Substrate                                              19



        a.  Nitrification Tests                                19



        b.  Denitrification Tests                              20



            (1)  Nitrate Solution                              20



            (2)  Carbon Source                                 20



B*  Experimental Results of Reactor Tests                      21



    1.  General Teat Conditions                                21



    2.  Tests 1, 2, 3 and 4                                    23



    3.  Tests 5 and 6                                          24



    4.  Tests 7 and 10                                         25



    5.  Tests 8 and 11                                         25



    6.  Test 9                                                 26



    7.  Test 12                                                26



    8.  Tests 13a and 13b                                      27



    9.  Test 14                                                27



   10.  Tests 16 and 17                                        27



   11.  Test 18                                                28



   12.  Tests 19a, 19b, 19c                                    28



   13.  Tests 20 and 21                                        29



   14.  Tests 22Aa and 22Ab                                    29



   15.  Test 23                                                30



   16.  Test 24                                                32



   17.  Tests 25a, 25b, and 25c                                33



   18.  Tests 26a and 26b                                      34

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         19.   Tests 27a,  27b,  2?o,  and 2?d                           34



         20,   Tests 28a and 28b                                      35



         21.   Discussion  of Reactor Test Results                     36



              a.  Nitrification                                      36



              b.  Denitrification                                    36



              o.  Ibur-Stage Operation                               38



         22.   Analyses of Process Over 24-Hour Period                38



              a.  Sampling                                           38



              b.  Discussion                                         38



                  (0  Nitrification                                 38



                  (2)  Denitrification                               40



VII.  DEMONSTRATION PLANT TESTS                                      42



      A.  Test Program                                               42



      B.  Equipment                                                  43



          1.  General                                                43



          2.  Reaction Tanker                                        43



          3.  Air Supply                                             44



          4.  Pumps and Feed apparatus                               44



          5.  Deaeration Tank                                        45



          6.  How Metering                                         45



          7.  Sludge Wasting                                         46



          8.  Sampling                                               46



      C.  Procedures                                                 47



      D.  Experimental Results of  Demonstration Plant  Tests          48



          1.  General Test  Conditions                               48



          2.  Test  1                                                 50



          3.  Test  2                                                 50

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                                                           Page
 4.  Test 3                                                 50
 5.  Test 4                                                 50
 6.  Test 5                                                 51
 7.  Test 6                                                 51
 8.  Test 7                                                 51
 9.  Test 8                                                 51
10.  Test 9                                                 52
11.  Test 10                                                52
12.  Test 11                                                52
13.  Test 12                                                52
14.  Test 13                                                52
15.  Test 14                                                53
16.  Test 15                                                53
17.  Test 16                                                53
18.  Test 17                                                53
19.  Test 18                                                54
20.  Test 19                                                54
21.  Discussion of Test Results                             54
     a.  Overall                                            54
     b.  Nitrification                                      54
     c.  Denitrification                                    55
     d.  Two-Stage                                          56
22.  Process Variations Over 24-Hour Periods                57
     a.  Sampling                                           57
     b.  Discussion                                         58
                          vi

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                 (l)  General Observations                           33




                 (2)  Nitrification Process                          58



                 (3)  Denitrification Process                        59



VII.  CONCLUSIONS                                                    62



VIII. BIBLIOGHAPHT                                                   64
                                 vii

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LIST OF TAW.B5
umber

1.
2.
3.
4.
5.
6.
7.
8.

9.

10.

11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Following
Page
Composition of Dry Milk Solids
Average Analysis of Synthetic Wastewater
Listing of Reactor Tests
Reactor Test Operational Data
Reactor Test Analytical Data
Reactor Denitrification Test Data
Equilibrium Nitrogen Data, Test 23
Test 20 - Nitrification - Feb 19, 1968. Hourly
Variable Flow Data
Test 20 - Nitrification - Mar 18, 1968. Hourly
Variable Flow Data
Test 22Ab - Denitrification - Mar 18, 1968. Hourly
Variable Flow Data
Listing of Demonstration Plant Test Periods
Demonstration Plant Operational Data
Demonstration Plant Analytical Data
Demonstration Plant Denitrification Plant Test Data
Demonstration Plant Effluent Ammonia and Organic Nitrogen
Demonstration Plant Hourly Data* Jan 6-9, 1969
" ' " ' i April 7-9f May 21-22, 1969
" " " " t May 22-231 June 4-6, 1969
"  " " : June 16-20, 1969
" " "  : June 19-20, 1969
 " " " : July 10-11, 1969
18
19
21
21
21
22
30

38

38

38
48
48
49
49
49
57
57
57
57
57
57
   viii

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                             LIST OF FIGURES



Humber                                                          Following
  1.      Flow Diagram for Denitrification                          3



  2.      Nitrate Reduction Rate in Continuous Flow                10



             Denitrification



  3.      Flow Diagrams                                            17



  4.      Reactor Tanks - Construction Details                     18



  5,      Assembly of Reactor Tubes and Equipment                  18



  6.      Equipment for Variable-Rate Pumping                      18



  7.      24-Hour Sampling: Test 20 Nitrification. Feb 19,  1968    38



  8.      24-Hour Sampling: Test 20 Nitrification. Liar 18,  1968    38



  9.      24-Hour Sampling: Test 22Ab Denitrification Mar 18, 1968-38



 10.      Nitrate Reduction Rates in Reactor Tests                 36



 11*      Demonstration Plant Tanks - Construction Details         43



 12*      Demonstration Plant: General Tank Assembly               44



 13.      Demonstration Plant: Nitrification Tanks, Primary Feed



             Pump and Sampler                                      44



 14.      Demonstration Plant: Denitrification Tanks and



             Effluent Siphon Barrel                                44



 15      Demonstration Plant: Air Metering Apparatus              44



 16.      Demonstration Plant: Primary Feed Pump                   45



 17      Demonstration Plant: Deaeration Tank                     45



 18.      Nitrate Reduction Rates in Demonstration Plant Tests     56



 19.      24-Hour Sampling Data: Jan 6-7,  1969                     57



 20.         "               i Jan 7-8,  1969                     57



 21.         "               : Jan 8-9,  1969                     57

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22. 24-Hour Sampling
23. " "
24.  
25. "
26. " "
27. " "
28. " "
29- " "
30.  
31 . "
32. " "
33* 24-Hour Sampling
34.
35.
36.
37. " "
38. " "
39.
40. " 
41. " "
42. " "
Data: Apr 7-8, 1969
11  Apr 8-9, 1969
" : May 21-22, 1969
" : May 22-23, 1969
" : June 4-5, 1969
" : June 5-6, 19&9
" : June 16-17, 1969
" : June 17-18, 19&9
11 : June 19-20, 1960
" : June " , 19 &9
" : July 10-11, 1969
Data Summary* Primary ML-1T, Constant How
" " * " , Variable Flow
" " : Nitrification Nfl^-N, Constant Flow
" " : ' " , Variable Plow
11 " : Denitrification NHj-N, Constant "
" H . it  f Variable "
" " i Nitrification NO^H, Constant ' "
H ii : ii ii f Variable "
" " : Denitrification " , Constant "
" " : ' " , Variable "
43. Load Curves* June 5-6, 1969
44. w " : "
45. " " * "
46. COD and TOG Load
47- Nitrogen "
17-18, "
19-20, 
Curves: June 19-20, 1969
11  July 10-11, 1969
48. Phosphorus Load Curves: July 10-11, 1969
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57
57

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                      I. NEED FOR NITROGEN REMOVAL



     Nitrogen in various forms is one of the more abundant constituents of



municipal wastewater and is only partially removed in conventional treatment



processes   .




     Incomplete nitrogen removal may contribute to the degradation of



receiving waters in several ways.  Ammonia oxidation by nitrifying bacteria



may result in serious oxygen deficiencies, and the general problem of



eutrophication nay be enhanced by making nitrogen more readily available for



the growth of aquatic plants.  In recognition of these possible effects



water quality and effluent standards often include limitations on nitrogen



concentrations,  the consequence of which is to require higher removal



percentages than now obtained from conventional treatment processes.

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            II. DSNITRIFICATION PROCESS FOR NITROGEN REMOVAL



A. Description of Process



     Denitrification in waste-water treatment has been studied by a number of



investigators^ '**' ' ' ' f  '   , and several process schemes have been



proposed to utilize microbial denitrification for nitrogen removal.



Denitrification for nitrogen removal requires the reduction of nitrates to



nitrogen gas, and such reduction is the "true dissimilatory nitrate reduction"


                               (12}
pathway as defined by Verhoeven   '.  Reduction is accomplished by hetero-



trophic facultative anaerobic species of bacteria which have the ability to



replace oxygen with nitrate as the essential hydrogen acceptor in their



metabolic processes^   .  These ubiquitous microorganisms include many genera



and the overall reaction by which nitrogen is removed is as follows:



                         2HN03 + 10H = N2 + 6H20.



     Because municipal wastewaters seldom contain appreciable concentrations



of nitrogen in the nitrate form the nitrogen removal process by denitrifica-



tion must be preceded by a nitrification process whereby essentially  all



of the nitrogen is converted to the nitrate form.  It is generally accepted



that the conventional activated sludge process should be used to produce a



nitrified effluent, and the operating conditions required with the process



to obtain such an effluent have been established by Downing, Painter and



Knowles^ ^.and by Johnson & Schroepfer^1 '.



B. Kinetics of the Denitrification Process



1. Development



     The denitrification process investigated in this research work



involved a continuous flow reactor, gravity solids-liquid separation and


                                  (2)
sludge recycle.  It has been shownv ' that rapid denitrification requires



an external carbon source which may be a portion of the raw wastewater or
                                  -  2 -

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an externally supplied organic compound.  The flow diagram used is shown

as Figure 1.


     The similarity of the flow diagram to that of the activated sludge

process is obvious and the two processes also usually have a common

objective to yield an effluent having a low biochemical oxygen demand (BOD).


The processes differ, however, in the dependency of input quantities.  In


the activated sludge process a carbon-containing substrate is an independent

variable while dissolved oxygen, the hydrogen acceptor, is a dependent


variable.  Prom an economic standpoint an effort is made to minimize the

oxygen input.  In denitrification the roles of carbon and hydrogen acceptor


are reversed.  The nitrate ion as the hydrogen acceptor is an independent

variable and the carbon substrate must be supplied in proportion to the

nitrate.

     With these comparisons between the two processes the generally accepted

theories of microbiological growth used to describe the activated sludge

process may be applied to the denitrification process as proposed.  Many

investigators have described activated sludge kinetics in continuous flow

cultures including McKinney    , Eckenfelder & O'Connor    ,  Schulze^   ,

Downing, Painter and Knowles     and Smith and Silers    .  Three differen-

tial equations may be used to describe the interaction in a biological

treatment process.  The net rate of growth of microorganisms is usually

given as:

                           (1) f|= klX  - bx

where x. is the concentration of microorganisms, k. is the specific growth


rate constant, and b is a decay constant.

     The rate of disappearance of substrate may be described as:


                                 $.     1 ft*
                                 dt " " Y dt
                                   - 3 -

-------
x*
So
                 r

              COMPLETELY

               Re/!CTOfZ
                                     F//VAL

                                    SETTUK6
       x,
       s,
                        J
                  SLUDGE
                          Q
      X, ,
  FLOW
FOR  DEMirR/FJCATION

-------
where s is the substrate concentration and Y  is  the yield of microorganisms

in terms of grams of microorganisms produced  per gram of substrate used.

     In an aerobic process the oxygen uptake  rate nay be presented as:
                          / .. \  dO    .  ds   , ,
                          (3)  at ' a  d"t  + *  X
where dO/dt is the rate of change of the  dissolved oxygen concentration,

a1 is a constant describing the oxygen uptake proportional  to  the substrate

removal, and b1 is the endogenous oxygen  denand  constant.   In  the denitri-

fication process a nitrate concentration  or the  oxygen equivalent of nitrate

is substituted in the above equations for the oxygen  concentration.

     Although these three equations describe  fundamentals of microbial

growth, modifications are necessary when  applying them to continuous flow

denitrifying cultures in completely mixed systems when recycle is employed

as shown in Figure 1 .

     Referring to Figure 1, a  material balance for microbiological cell

growth may be written as follows:

                 Change = Input - Output  + Growth - Decay


               V || = QxQ



                tr=v[xo + rx3- d*')^]* Vi -bxr
                                      j
For steady state and complete  mixing,  rrr = o,  and assuming  XQ  = 0:

                     (4) (Ur) x1 - rx3 = t^x-taj)
                                             y
where V is the volume of the reactor and  t =  ^,  the reactor detention time.

     Referring again to Figure 1, a material  balance  for substrate is as

follows:
                 Change = Input - Output  - Removed

                                  - 4 -

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For steady state and complete nixing, ds/dt = o:
                                         tk x
                           (5) 80 - 8, . -LI.
     Using the notation from Figure 1, a material balance for oxygen
(nitrates) is written as:
                    Change = Input - Output - Removed

                                           S1) - bx1V
For steady state and complete mixing, dO/dt = 0, and assuming 0, = 0:
                       (6) OQ = a'CS^) + b'Xlt
where a1 and b1 are oxygen (nitrate) use coefficients.  It is assumed
in the above equation that all oxygen added to the system is as an
equivalent concentration in the raw flow.
     Equations (4), (5), and (6) are the counterparts of the general
equations (l), (2) and (3), and may be used directly in the analysis of
the denitrification system under consideration.  The design and operation
of a denitrification system requires the determination and/or assumption
of a number of parameters in the equations.  Usually the unknown and the
known or assumed values would be listed as follows:
     Unknown parameters:
        t   SB  reactor detention time, days
        x.  =  mixed liquor volatile suspended solids (MLVSS)
               concentration, mg/1
        S   =  substrate concentration as the 5-day 20C BOD (BOD,.), mg/1
                                 - 5 -

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     Known or assumed parameters:



        Q  = total inflow excluding recycle, I/day



        r  = return sludge flow rate as fraction of raw flow



        S  = effluent BOD ,  mg/1




        x> = VSS concentration in return sludge, mg/1



        0  = equivalent oxygen concentration in raw flow, mg/1
        Y  = yield coefficient, rag VSS/mg BOD_ removed




        a1  = coefficient of oxygen use by substrate, mg 0/mg BOD,., removed




        b1  = coefficient of oxygen use by endogenous metabolism,




             mg 0/mg VSS/day




        b  = VSS decay rate, days'




        k1  = specific growth rate, days"




     Assuming the validity of equations (4), (5) and (6), the unknown




parameters  may be determined from the solution of thesa equations




simultaneously.  This must be preceded, however, by assigning appropriate




values to the remaining parameters, the most critical of which are 0 , Y,




k1 , a1 , b1  and b.




2. Oxygen Equivalent Available from Nitrates




     Although the nitrate ion is used as the hydrogen acceptor the oxygen




analogy may be used, and McCarty^  ' and Barthr   have shown that on an




equivalent  basis only 5/6 of the oxygen in the nitrate is available as an




equivalent  amount of dissolved oxygen.  Consequently the 0  value is ^j x 5/6




of the nitrate-N concentration \vhich is to be reduced.




3. Yield




     In a study of nitrate respiration by Aerobncter aerogenes using



                                           (19)
glucose as  the carbon source by Hadjipetrou    , yield coefficients v;ere




determined  for three environments: anaerobic; annerobic with nitrntos;




and aerobic.  The respective yields were 0.1/!, 0.25, ."-nd O./JO j cjlln/c





                                  - 6 -

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The relative magnitude of yields was particularly noted by Painter   ':



that anaerobic systems have the lowest yields; and that yields from



nitrate systems are less than those from aerobic systems and greater than



anaerobic systems.  Although no specific data from mixed cultures and



wastewater substrates are available it is reasonable to assume that yield



coefficients less than those from aerobic systems are appropriate.  On



this basis Y values of 0.2-0.4 would seem reasonable.



     McCarty'  ' studied the characteristics of several pure organic



compounds with respect to denitrification and determined consumptive ratios



for each.  The consumptive ratio was defined as the ratio of the total



quantity of an organic chemical consumed during denitrification to the



stoichionetric requirement for denitrification and deoxygenation alone.



The greater the ratio the greater chemical requirement for biolojiccl



growth (synthesis).  Because net synthesis does not directly require the



uptake of nitrate, the lov;er t!'
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Maximum rate constants determined from  the  data  v;ere  11. /]  and  6.3  d::ys~
respectively.  Studies by Schroeder  Busch   "'  compared  tho  rate  of



disappearance of glucose by dissolved oxygen  and nitrate  syotjir..;   nd  the



rates of glucose uptake were quite similar.   It  is  possible to  estimate a



maximum rate constant of approximately 14  days'   from the data.  For


                                      (23)
activated sludge Downing; and 'Vheatland     estimated  a maximum  rate



constant of 4*8 days"  and Smith   ' found with  activated sludge and  under



particular conditions of analysis that the maximum  rate constant varied



from 3 to S days' .  The Michael is-llenten  expression  for  the  microbial



growth is usually used to relate specific  growth rate (k. ) to maximum specific



growth rate (km) :

                                     k  S
                                1 - K  + s
                                     8


Y/here K  is the Llichaelis constant and S the substrate concentration.
       s

       (23)                                            (18)
Downing^  ' found it reasonable to assume, as  did Siaitlr    ,  a  value for K
                                                                          S


for sewage of 150 ng/1 BOD,, where S also is in terms  of BOD,..   If  it is



reasonable to assume k  and K  values of 4*8 days'  and 150 mg/1 BOD..
                      m      s           TV              u/     ij



respectively for aerobic systems, corresponding constants may be estimated



at 2.5 days'  and 150 mg/1 BOD  for nitrate systems.  Therefore in this



analysis:



                               k1 = 150+S



5. Oxygen Equivalent Required Per Unit of Substrate Removed



     The utilisation of a carbon substrate in  biological treatment processes



is accomplished through a combination of oxidation to carbor.  dioxide and



synthesis to ne,v cells.  Oxygen or nitrate is  used in direct  proportion to



the oxidized substrate and in a nitrate respiration system it is particularly



advantageous to minimize the ratio: substrate-used/nitrate-reduced.  It v;as
                                   - 8 -

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                                          (19)
shown earlier from the work of Hadjipetroir Jl that for a given amount



of substrate utilized the yield is less with nitrate respiration than



with oxygen.  Consistent with this observation it is appropriate that



greater a1 values should be used for nitrate systems than for aerobic



processes.  The a1 values usually used with conventional activated sludge



systems are of the order of 0.4 to 0.6 and consequently corresponding



values for nitrate systems should be somewhat greater.



6. Endogenous Coefficients



       No directly applicable data are available for the decay coefficient b,



but a value of 0.1 as used in the activated sludge process should be



reasonable.  More critical is the endogenous nitrate reduction coefficient.


                                                           (2)
In terms of oxygen equivalent, work by Johnson & Schroepferv   shows that



the endogenous demand coefficient b1 is of the order of 0.04.



7. Rate of Nitrate Reduction



       The rate of nitrate reduction was expressed in equations 3 and 6 as



a function of the rate of substrate removed and the weight of mixed liquor



solids.  As with oxygen uptake, the contribution of the endogenous demand



to the rate of nitrate reduction is small compared to the nitrate demand



of an actively metabolizing sludge.  Therefore, the only way to maintain a



high rate of nitrate reduction, which is desirable from an economic



standpoint, is to have a high rate of substrate removal.  McKinney^1



observed that growth rates are controlled by the Food/Microorganisms ratio,



and since substrate removal rates are proportional to growth rates, the rate


                                                                     (2&}
of nitrate reduction should be a function of this ratio.  Eckenfelder^



expressed the rate of nitrate removal (R) in terms of mg nitrate-N removed/


                                              (2)
g MLSS/hr, and data after Johnson & Schroepferv ' presented in Figure 2



show this rate to be a linear function of the Food/Microorganisms ratio
                                   - 9 -

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expressed as P or BOD/^ILVSS: weight of BOD  applied to the reactor per day



divided by the weight of MLVSS in the reactor.  Milk solids were used as



the carbon or BOD source.  A line of regression through the points has the



equation:



                            R = 6.92 F + 0.06



and the correlation coefficient is 0.969.  The intercept is essentially



the endogenous nitrate reduction rate for this particular set of data.



The data for the two enclosed points on Figure 2 were not considered in the



calculations since they were obtained under conditions when excessive amounts



of substrate were being applied to the reactor.  It is apparent that at a



given nitrate reduction rate the use of increasing concentrations of



substrate would shift the data point progressively to the right and beyond



equilibrium considerations as shown in Figure 2.



     When effluent quality standards require nitrogen removal it is usually



the case that effluent BOD 's must also be low.  Because both effluent



quality and rate of nitrate reduction are functions of the BOD/MLVSS ratio,



it is incompatible to expect high rates of nitrate reduction and yet obtain



low effluent BOD's.



8. Ratios: Substrate Metabolized/Nitrate Reduced



     The basic equations 3 and 6 require determining a constant relating



the rate of degradation of substrate to the rate of nitrate reduction.



Neglecting the endogenous demand this constant is an equilibrium ratio



between the substrate utilized (to reduce the nitrates) and the nitrates



reduced.  The slope of the curve in Figure 2 is essentially that ratio.



The BOD value used in Figure 2 includes that used for deoxygenation and



consequently the BOD used only in the reduction of the nitrates cannot be


                                                           (7)
obtained directly from the graph.  Barth, Brenner and Lewis^ ' in their
                                  - 10 -

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         ^
            m
                  -~







         -


                              p

                                 
                                __
                     tea rra:
                                                          timm
                                                            m

                                                                           m
                                                                           _
..:;:

m
                                                      : ::
                                                         .-

                                                         
                                                             -
                                                            	


                                                                
                                                               ttn
                                                                              -






                                                               I

':''


               


                                                                                 :-T

:::-
                                      itttt tttfi
:::

                                        m ;

I



          ffl S

                                          ttttittt


                                                                                 1i
                                       -


                                                                    




               TT~"
                                              .



            :r::
         ~

                                       :.::



                                       "~

                                           ::
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                  tit

                                              , _










                                         r -::
-


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               ffl ffl

                                            : ti:
                                                    ra A/

-------
work with methanol expressed this as a methanol/nitrate-N ratio and



concluded that a value of approximately 4 was required.  Work reported by



McCarty*  ' showed that in semi-continuous operation of denitrification



units using detention times of 10 to 30 days the nethanol to nitrate ratio



was only 2.48.  The difference was in part attributed to the fact that the


     (7)
Barthx ' work may not have deducted that methanol required for deoxygenation.



Another, and possibly more important factor contributing to the difference,



is the fact that where long contact times are used there is always a greater



proportion of net oxidation over synthesis resulting in the reduction of



more nitrate per unit weight of substrate metabolized.



     7ork reported by Tamblyn and Sword^' and Seidel and Crites'  ' with



the anaerobic filter confirmed McCarty's^  ' work with respect to the



required methanol/nitrate-N ratio.  They were able to accomplish complete



nitrate reduction with contact times of less than 2 hours and methanol/



nitrate-N ratios of 2.5.   The anaerobic filter may well be a more efficient



unit for nitrate reduction than the completely mixed methanol system used


        (?)
by Barthv '.operating with a holding time of 3 hours and a methanol/nitrate-N



ratio of 40.  The difference in methanol requirements is most likely



attributable to the differences in process yield.  In nitrate reducing



systems the yield from the anaerobic filter may be less than that from the



completely mixed system just as trickling filter yields are less than those


                               (27)
from activated sludge processesv    .  Lower yields are characteristic of



anaerobic systems and the anaerobic layer adjacent to the media in filter



systems may account for the lower net yields.
                                 - 11  -

-------
     From the discussion it is evident that a carbon source must be supplied



to denitrify at a reasonably high rate, and a constant weight ratio of



substrate to nitrate must be supplied.  Carbon sources ranging from pure



organics to municipal wastewaters may be used, and the substrate portion of



the ratio may be expressed as actual weight of chemical, carbon content, COD



or BOD.  To enable the use of a common parameter for all carbon sources,



a ratio of BOD  applied/nitrate-N removed (BOD/N) has been used in this work.



The mean ratio required in the work presented in Figure 2 was 4.5 (range



4.0-4.9).  The methanol/nitrate-N ratio converted to similar units using a



BOD5 of methanol of 0.835 S/g     is 3.3 from the work by Barth^' and 2.1



after McCarty^   .  It is likely that the ratio depends both on the substrate



used and the biological system employed.  With a particular system and



substrate, one or two pilot tests would establish this ratio and the linear



relationship between loading and rate of nitrate removal for use in the



design of facilities.



9. Example of Use of Kinetic Equations



     Using a flow diagram as presented in Figure 1  and data given previously


                       (2}
by Johnson & Schroepf erv ' : Test 30-3:



     Assumed Values



        S,  =  10 ng/1 30DC
         1         w      5


        r   =  0.35



        x^  =  8000 mg/1 MLVSS




        o  =  19'1 X ft X 6 =


        Y   =  0.4 mg VSS/mg BOD,.



        a1  =  0.65 mg 0/mg BOD^



        b1  =  0.04 mg 0/day/mg MLVSS



        b   =  0.10 days"


        ,       2.5 x 10   n .,- ,   -1

        k1  "  150 + 10 = -1
                                   - 12 -

-------
    Unknown:




       SQ, x, ,  t



    Equations :




       (4) (1 + r)  x1





       (5) (3   -  S  ) .
              o     i
        (6) Oo  =  a'(SQ- S,,)  + b'Xlt



     Subst  in equations (4),  (5)  & (6):



        Ua)  1.35 X,  -  2800  = 0.16 Xjt - 0.1  3^  t = 0.06




        (5a)S  = Oj^V^ 10

             0     0.4



        (6a)  55 = 0.65(SQ  -  10) + 0.04 x^




     Subst  5a in  ^a:



             55 = 0.26  x^ ^ 0.04 x.,t




           x^ = 183



     Then S , x- , and t are :




             S  = 83 mg/1
              Q




             Xl = |21| = 2o80 mg/1




             t  = .089 days = 2.1  hrs

                       BOD        8



     Then:    Ratio - nitrate-H = 19J = 4'4



     The actual data reported included a I.'ILSS concentration of 2360 rag/1,




a detention time of 2.2 hours and a 30D/N ratio of 4.2.  Although the



computed data compare well with the experimental data it is recognized that




changes in the magnitude of the constants used in the equations may alter




the results considerably.  Nevertheless the values for the constants used in




the equations are reasonable with respect to the data available at the




present time, and the equations show a sound kinetic basis for describing




characteristics of the denitrification process.





                                  - 13 -

-------
C. Process Economics



     The carbon source and choice of process used for denitrification are



the key factors in an engineering design situation and in a cost analysis.



If no external carbon source is used and endogenous respiration is used for



denitrification, large contact tanks and high capital costs are required.



Reliance on endogenous respiration alone for dentrification has the additional



disadvantage that aimnonia-N is continually released as cellular solids are



decomposed.  The use of an additional carbon source will reduce the capital



costs but may increase operating costs.  If a raw municipal waste is used as



the carbon source the percent nitrogen removal will be limited, and the



purchase of organics such as methanol are costly.  In any local situation it



may be possible to obtain nitrogen deficient organics at a low cost and in




turn alter the economics of the process.



     Ideally, of course, a local supply of a nitrogen-deficient wastewater



should be used, and in such situations the economic aspects of yield become




important only with respect to sludge disposal considerations.
                                  - 14 -

-------
                      III.  EXPERIMENTAL RESEARCH PROGRAM



     The objectives of the test program were to more explicitly define the



factors affecting nitrification and denitrification such as the effect of



variable rates of flow, temperature, mixed liquor solids concentrations,



reaction time, and dissolved oxygen in the system.  Initially continuous



flow tests were conducted in the laboratory with a synthetic wastewater to



obtain sufficient information to design and operate a larger scale demonstra-



tion plant using a municipal wastewater as a substrate.  Although factors



affecting nitrification have been investigated previously by Johnson and



Schroepfer^ ' and particularly by Downing, Painter and Knowles^   , it was



felt that the nitrification process for these particular operating conditions



should be investigated as a preliminary to denitrification.  The principal



goal, however, was to study denitrification.



     The initial tests are referred to as the Reactor Tests and the later



tests are called the Demonstration Plant Tests.
                                  - 15 -

-------
                           17.  ANALYTICAL PROCEDURES



A.  General



     Whenever possible, analyses of the waste-waters were conducted in


                                                        (29)
accordance with procedures published in Standard Methods    .  Where several



procedures were given and when the procedure used was not as presented in


                (09)
Standard ifethods    , the particular methods employed are described in the



following paragraphs.  Coloriinetric work was conducted with a Coleman Llodel 14



spectrophotometer.



B.  Mixed Liquor Suspended Solids



     Mixed liquor suspended solids were measured using 11.0 cm diameter



glass fibre filter paper, JJurlbut Paper Go. No. 934-AH.  The paper is non-



hygroscopic and as such did not require drying prior to initial weighing.



After obtaining the tare weight of the paper, the paper was placed in a Buchner



funnel having a 91 cm Inside diameter in order to form a cup with the paper.



The measured sample was then filtered with the usual vacuum.  The use of the



glass paper enabled the determination of volatile content by burning at



600 C.  Each paper was conveyed on a flat porcelain dish.



C.  Dissolved Oxygen



     Dissolved oxygen concentrations were obtained with a Precision Scientific



Co. galvanic cell oxygen analyzer.



D.  Nitrate Nitrogen



     The phenoldisulfonic acid method was used.



E.  Total Phosphorus



     The procedure used was essentially that described b5^ Menzel and Corwin   '



and Gales, Julian and Kroner^  ' in which potassium persulfate is used.  The


                                                                   (29)
orthophosphate was analyzed by the aminoaphtholsulfonic acid method^ 7'.
                                - 16 -

-------
                            V.   REACTOR TESTS




A.  General Conditions




     The Reactor Tests were conducted in the Sanitary Engineering Laboratory




at the University of Minnesota.  All tests were conducted with a synthetic




wastewater under controlled temperature conditions and with continuous flow.




     The basic process for studying nitrification was the activated sludge




process.  Similarly, the denitrification process was studied as an anaerobic




version of the activated sludge process.  These basic flow diagrams are shown




in Figure 3  The activated sludge process needs no explanation but the




denitrification process should have some clarification.  The reaction tank




of the denitrification process receives the nitrified effluent from the




activated sludge process together with a limited amount of raw waste or other




carbon-source material.  Both the reaction tank and settling tank of the




denitrification unit were sealed off from the atmosphere and interconnected.




The gases taken off at the tope of the tubes were compressed and recirculated




to the bottom of the reaction tank to provide mixing.  After the initial use




of oxygen in the system the recirculation gases were essentially molecular




nitrogen (N_) and the system was kept anaerobic.




B.  Equipment




     All reactor tests were conducted in a constant temperature room measuring




6 ft x 10 ft and as manufactured by the Hotpack Corp.




     The reactor units were all plexiglass tubes, each either 2 inches or




3 inches in diameter, 4. ft long and having a wall thickness of 1/8 in.  The




bottom of each tube has a machined cone-shaped configuration.  The bottom and




several positions along the side were drilled and tapped with a -^ in pipe




thread.  Caps were made to fit both the 2 and 3 inch diameter tubes to enable




sealing the tubes from the atmosphere.  The details of the tubes and cap are
                                 -  17 -

-------
                                 SETTLING
       
                      SLUDGE-
SOURCE
           FLOW  DIAGRAMS
                                   FIGURE 3

-------
presented in Figure 4  The tubes were made for use either as aeration



tanks or settling tanks and several tanks could be connected in series to



increase total residence times.  Tubes were interconnected with soft plastic



vinyl tubing.  Aeration was accomplished by insertion of a porous stone aerator



at the bottom of the tube.  The tubes were assembled on a rack to permit



adjustment up or down according to the head requirements for gravity flow.



A typical arrangement of the tubes and equipment is shown as Figure 5-



     For the denitrification tests, mixing in the reaction tank was provided



by recalculating the effluent gases in a closed system through the use of a



Cole-Farmer Bantam Dyna-Vac laboratory pump.



     All feed pumps and sludge recirculation pumps were of the Sigraamotor type



with Zero-Max speed reducers.  For variable flow operation the lever operator



of the Zero-Max was interconnected with a clock-timer assembly such that the



pumping rate varied in a sinusoidal pattern having one cycle over a 24-hour



period.  The equipment is as shown in Figure 6.  The operation of the entire


                                               (32)
unit has been described and analyzed by Johnson    .



C.  Procedures



1.  General



     Initially tests were conducted at 20 C to obtain background information



on independent operations of the nitrification and denitrification processes.



The majority of these tests were conducted with constant rates of flow, but



for a few days variable flow was used.



     After conducting these initial tests, the nitrification and denitrification



processes were then run in series at both constant and variable flow conditions



at 20C.  Later, series tests of nitrification and denitrification at 10 C were



conducted.



     To be assured of having a supply of activated sludge solids on hand at all



times a Continuous flow conventional activated sludge "pilot plant" was kept
                              - 18-

-------
    A
    t-
 I   I
Z"OR.
      PLAN
    ELEVATION
    WALL

1



2. " 0*. 3
PLEXIGL A
n

^^

ELE\/
i '
i4
,, .
LJ
'AT ft
tt
5
i.1 'i '

IhfJ
Ij  i!
)/V
CAP FOR TVdES
                                    0-RIN6
SECTION A-A
REACTOR TANKS - CONSTRUCTION

-------
  GAS
OUTLET
          DENITRIFIC&7ION
NITRIFICATION
                                                              FEED
  ASSEMBLY  OF REACTOR  TUBES  AND EQUIPMENT

-------
                  CLOCK TIMER.
                              _ SHQFT
                               TO Pl/MP
                 ELEVATION
EQU/PMENT FOR  I/ARABLE-RATE  PUMPING
                                   FIGUK. E

-------
in operation throughout the period of testing.  The mixed liquor solids from
this unit were used in the reactors.  This equipment was described previously



     Unless otherwise shown, all physical, chemical and biological analyses



were done using 24-hour composite samples.  This was easily accomplished since



the entire volume of effluent from any reactor system for a 24 -hour period was



collected in one container from which the samples were obtained.



     All analytical work was done in the Saflitary Engineering Laboratories.



2.  Substrate



    a. Nitrification Tests



     Solutions of dry milk solids were used as the basic raw waste and at



times were supplemented with other constituents.  Characteristics of dry milk



solids are as shown in Table 1*   .





                    Table 1.  Composition of dry milk solids
                                                                             (2)
Constituent
Butterfat
Protein
Lactose
Total solids
Organic solids
BOD (5-day, 20C)
Total nitrogen (N)
Total phosphorus (P)
Per cent
by weight
0.9
36.9
50.5
96.7
88.6
75.0


Concentration in
solution: 1g/gal
-
-
-
-
-
198 rag/1
15-4 mg/1
2.6 mg/1
     The raw waste for the nitrification tests was a supplemented solution of



dry milk solids consisting of:



          Dry milk solids -   26lf mg/1 (lg/gal)



          Sodium bicarbonate - 264 mg/1 (lg/gal)



          Ammonium sulfate   -  56 mg/1




          Dechlorinated City of Minneapolis tap water
                                 - 19 -

-------
This mixture is referred to as the standard milk solution (SM) with characteris-
tics as shown in Table 2.

  Table 2.  Average analysis of synthetic wastewater (standard milk solution)
                                                    Pr.
Chemical oxygen demand, COD
Biochemical oxygen demand, BOD, 5-day, 20"C
Ammonia and organic nitrogen-N
Total alkalinity as CaCO
Total residue
Total phosphorus, P
291 mg/1
198 mg/1
 27 mg/1
200 mg/1
517 me/1
  2.6 mg/1
     The waste was mixed and stored in plastic barrels from which it was
pumped into the units.
b.  Denitrification Tests
     (1)  Nitrate Solution
     When separate denitrification tests were conducted  the nitrate feed was
in  the form of a solution of sodium nitrate.  The  exact  concentration varied
between tests.
     (2)  Carbon Source
     The carbonaceous material used as feed  to the denitrification reactor
was either a  solution of milk solids  or methanol.   The milk solids were not
supplemented  with either sodium bicarbonate  or ammonium  sulfate.  All  solutions
were made in  dechlorinated City of Minneapolis tap water.  The  exact concentra-
tions used varied between the tests.
     The characteristics of methanol  were  assumed  as follows:
          Density:         0.791  g/nl
          COD:             1.500  g/g
           BOD5(28):
                 0.835 g/g
                                - 2O -

-------
Table 3.  Listing of Reactor Tests
Test
No.
1
2a,b
3a,b,c
4
5
6
7
8
9
10
11
12
13a
13b
14
15
16
17
18
19a
b
c
20
21
22
22Aa
22Ab
23
23
23
23
24
24
Dates
Start
7.10.67
7.10,67
7.15.67
7.27.67
9.12.67
9.12.67
10.13.67
10.13.67
10.25.67
10.27.67
10.27.67
11. 7.67
11.14.67
11.30.67
12. 5.67
12.18.67
12.19.67
12.19.67
1.16.68
1.23.68
2.10.68
3. 8.68
1.23.68
2. 7.68
3.18.68
2.14.68
3. G.68
4. 3.68
4. 3.68
4. 3.68
4. 3.68
5.10.68
5.10.68
End
9. 8.67
9. 8.67
9. 8.67
8.11.67
10.13.67
10.13.67
10.26.67
10.26.67
10.31.67
10.29.67
10.29.67
11.22.67
11.30.67
12.11.67
12.14.67
1. 1.68
1. 6.68
1. 1.68
2.14.68
2. 9.68
3. 7.68
3.13.68
4. 1.68
4. 1.68
3.29.68
3. 7.68
4. 1.68
5. 9.68
5. 9.68
5. 9.68
5. 9.68
5.28.68
5.28.68
Type*
of
test
N
N
N
N
11
N
N
N
D
N
N
D
N
N
D
N
D
D
D
D
D
D
IT
N
D
D
D
K1
31
E2
D2
111
D1
Tggp
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
Typey
of
flow
C
C
c
c
c
c
c
c
c
c
c
c
c
V
c
c
c
c
c
c
c
c
C & Y
c
c
c
C & Y
c
c
n
c
V
Y
Feed2
solution
SM
SM
SM
SM
SM
SM
SM
SM
HN
SM
SM
LIN
SM
SM
MN5
SM
MN1
10T2
MN3
MN3
MN4
MN3
SM
SM
MN3
:.3T4
I.IN3
SM
SM
-
SM
SM
s:.:

-------
                   Table 3 (continued)
Test
No.
24
24
25a

25b

25c

26a

26b

27a

2?b

2?c

2?d

28a
28b
Dated
Start
5.10.68
5.10.68
5.29.68

8. 9.68

8.19.68

9.26.68

11. 8.68

12. 2.68

2.13.68

3.15.69

4. 5.69

6.13.69
8. 4.69
End
5.28.68
5.28.68
8. 8.68

8.18.68

9.24.68

11. 7.68

12.18.68

2.12.69

3.14.69

4. 4.69

6.11.69

8. 3.69
8.19.69
Type*
of
test
N2
D2
N
D
N
D
N
D
N
D
N
D
N
D
IT
D
N
D
N
D
D
D
Tenn
V
20
20
20
20
20
20
20
20
20
20
15
15
20
20
10
10
10
10
10
10
10
10
Type7
of
flow
V
V
V
V
V
Y
V
V
V
Y
Y
V
Y
Y
Y
Y
V
Y
Y
Y
C
C
Feed2
solution
_
SM
SM
SM
SM
ML1
SM
L1
SM
L1
SM
L1
SM
L1
SM
L1
SM
L1
SM
L1
L2
L3
x  Type of Test:
           N     - Nitrification;  D - Denitrification
           N & D - Nitrification and Denitrification operated  in series
y  Type of Flow:
           C     - Constant Flow;  V - Variable Flow
z  Feed solution:
   SM  -  Standard Milk Solution as described in Table  2
   MN  -  120 mg/1 milk solids; 120 mg/1 NaNO^
   MN1 -  112 mgA     "        151 mg/1 NaJT(>3
   MN2 -  56 mg/1      "        151 mg/1 NaNC>3
   MN3 -  120 mg/1     "        129 mgA    "
   MN4 -  120 mg/1     "        155 mg/1    "
   MN5 -  240 ng/L     "        257 mg/1    "
   ML1 -  120 mg/1     "        0.16 ml/1  or  127 mg/1 methanol
   L1  -                        0.32 ml/1  or  253 mg/1 methanol
   L2  -  Effluent from a  nitrification plant plus L1
   12  _         "               "          "     "  0.25 ml/1  or
                                                   199  mg/1 nethanol

-------
                  Table 4.  Reactor Test Operational Data
  11
  12
  13a
  13b
  14
  15
  16
  17
  18
  19a
  19b
  19c
  20
  21
22Aa
22Ab
23:N1
23JD1
23:N2
23:D2
24:N1
24:D1
24:N2
24:D2
25a:N
  D
25b:N
  D
Reaction Tank*
Vol
1
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
DT
hrs
4.2
4.2
4.1
4.1
4.2
4.4
4.4
6.4
Loading
BOD/MLVSS
0.34
0.49
0.47
0.70
0.73
0.72
1.32
0.26

SA
3.3
2.2
2.5
1.6
1.6
1.7
0.8
4.6
V.>1
l
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.3
Settling Tank
DT
hrs
1.9
1.9
1.8
1.3
1.9
2.0
2.0
2.9
3SR
gpd/sf
362
358
366
366
359
344
342
237
No Data Analyzed
5.0
5.0
2.3
4.0
4.0
2.0
0.34
0.29
1.42
3.2
3.8
-
2.3
2.3
2.3
1.3
1.3
2.0
377
375
358
No Data Analyzed
No Data Analyzed
5.0
5.0
5.0
5.0
5.2
6.4
6.5
4.5
0.17
0.16
0.18
0.31
6.3
6.9
6.0
3.5
2.3
2.3
2.3
2.3
2.3
2.9
2.9
2.0
287
237
233
233
No Data Analyzed
5.0
5-0
5.0
5.0
5.0
5.0
5.0
5.0
2.3
2.3
7.3
5.0
2.3
2.3
7.3
5.0
2.3
2.3
7.3
5.0
7.3
5.0
4.6
4.8
6.0
8.3
4.7
4.7
7.2
7.4
2.3
2.6
8.2
4.0
1.8
1.6
10.6
5.1
2.2
1.8
8.1
3.9
8.9
4.2
0.20
0.08
0.15
0.20
0.20
0.15
0.17
0.21
0.34
0.31
0.20
0.26

0.14
0.13
0.19
-
-
5.1
12.6
8.9
6.7
5.9
7.6
7.4
5.8
3.6
3.7
5.9
6.0
-
8.3
9.2
5.8
-
-
0.12 10.5
0.32
0.18
0.25
3.5
6.5
4.7
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.3
2.3
5.0
5.0
2.3
2.3
5.0
5.0
2.3
2.3
5.0
5.0
5.0
5.0
2.1
2.1
2.7
3.8
2.1
2.1
3.2
3.3
2.3
2.6
5.7
4.0
1.3
1.6
7.3
5.1
2.2
1.8
5.5
3.9
6.1
4.2
326
315
250
130
322
323
208
202
295
265
117
167
377
410
92
136
307
350
121
169
110
157
         * For Nitrification Tests: Aeration Tank

         * For Denitrification Tests: Tank Mixed Without Air

-------
25c:N
  D
26a:N
  D
26b:N
  D
2?a:N
  D
27b:N
  D
2?csN
  D
27d:N
  D
28a:D
28b:D
                  Table 4.  Reactor Test Operational Data

                            Reaction Tank*             Settling Tank
Vol
1
7.3
5.0
7.3
5.0
7.3
5.0
7.3
5.0
7.3
5.0
7.3
5.0
7.3
5.0
5
5
DT
hrs
8.2
4.1
7.6
3.4
8.8
4.0
7.5
3.3
8.6
3.8
17.1
7.5
7.5
3.4
3.0
2.7
Loading
BOD/MLVSS
0.22
0.32
0.14
1.45
0.13
0.66
0.21
0.86
0.24
0.81
0.15
0.16
0.32
0.49
0.27
0.43

SA
5.2
3.6
7.9
0.8
8.7
1.6
5.5
1.5
4.8
1.4
7.7
6.8
3.6
2.3
4.0
2.4
Vol
1
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
DT
hrs
5.6
4.1
5.2
3.4
6.1
4.0
5.2
3.3
5.9
3.8
11.8
7.5
5.2
3.4
3.0
2.7
SSR
gpd/sf
119
161
124
191
110
168
125
193
109
170
44
87
125
191
224
244
          * For Nitrification Tests: Aeration Tank

          * For Denitrification Tests: Tank Mixed Without Air

-------
           Table 5   (



REACTOR TEST ANALYTICAL DATA
Test
No.
Test
Rate
of
Flow
rol/mln
Mixed
Liquor
mg/1
SS
vss
Effluent Concentrations, mg/1

TKN

NH3-N N02-N

N03-N

DO

SS

VSS

TP
1: July 10-29, 1967- N, C, 20
No. of Obs.
Mean
Mln.
Max.
Test



20
20.1
17.7
23.3
15
3755
3050
U720
15
3395
28l<0
U330
1
6.2


2a July 10- Aug. 8, 1967- N,
No. of Obs.
Mean
Kin.
Max.
Test
19.8
16.2
21.9
2bi Aug. 2l|
No. of Obs.
Mean
Mln.
Max.
Test
15
20.3
18.5
22.8
3a: July 15
No. of Obs.
Mean
Mln.
Max.
Test
No.
Mean
Mln.
Max.

19
20.3
11.5
26.2
3b: Aug. 2tt
of Obs.
10
19.9
18.7
21.li
25
2526
1910
3130
25
2336
1630
2820
1
1.0
- Sept. 8, 1967- N
16
2935
2220
Itl60
- Aug.
15
1800
960
3070
. Sept
11
1850
1210
23UO
16
2U70
1930
3600
2
1.3
D.lt
2.2
7, 1967. N,
15
1655
950
2870


. 3, 1967.
11
1555
1060
1980
2
2.6
2.0
3.2
2 
0.3
0.0
0.6
C, 20
2 "-
0.7
0.0
1.U
, C, 20
2 2
9.9 0.3
6.2 0.0
13.6 0.5
C, 20
..

N, C, 20
2 2
8.1 0.3
2.1 0.0
lluO 0.7
12
UU
11.8
17.5

22
7.7
0.7
16.0

16
8.6
0.2
20.0

19
5.8
0.2
16.5

11
3.7
0.1
7.2
2
6.3
6.0
6.5

6.5
6.2
6.7

3
6.2
5.5
7.2

6.6
5.2
6.7

6.8
5.9
7.U
13
99
21
260

21
100
15
220

15
109
20
500

12
193
30
396

10
13U
70
270
13
77
22
210

21
80
12
170

15
90
0
U55

12
166
30
396

10
117
50
225
3
1.3
1.3
1.3

3
1.1
1.0
1.2

3
0.7
0.1
1.7




2
0.2
0.1

-------
           Table 5  J-



REACTOR TEST ANALYTICAL DATA
Test
No.
Rate
of
Flow
ml/rain
Kioed
Liquor Effluent Concentrations,

SS
mg/j.
VSS TKN NH3-N
N02-N N03-N DO
SS
mg/1
VSS

TP
Test 3ct Sept. ii-8, 196? . N, C, 20
No. of
Mean
Min.
Max.
Test lit
No. of
Mean
Min.
Max.
Teat 5t
No. of
Mean
Min.
Max.
Test 6:
Test 7:
No. of
Mean
Min.
Max.
Test 8:
No. of
Mean
Min.
Max
Obs. U
19.1
18.0
20.0
July 27
Obs. 10
19.0
15.6
21.7
Sept. 12
Obs. 9
13.1
11.8
15.1
Sept. 12
Oct. 13
Obs. 12
20.9
19.3
22 Ji
Oct. 13
Obs. 12
20.8
17.9
21.5
1852
1510
2120
- Aug
9
912
610
1220
51-
1526 2.0
1270
1800
. 11, 1967  N, C, 20
82
819 13.9
580 13.6
1050 11* .2
- U 1
10.0 7.2
8.2
11.7
2 13 3
0.0 1.U 5.2
0.0 0.1 Iu2
0.0 5.3 6.2
'k
159
70
295
6
120
70
212
U
30
215
5
100
U5
188
1

-Sept. 22, 1967. N, C, 20
10
3U30
2780
liOOO
10 
2920
2310
3370
- Oct. 13, 1967 No Data
- 25, 1967. N, C, 20
10 10
3837 3lt75
3330 2990
1*370 Ii090
-25,
10
Ii525
loio
U870
1967. N, C, ?0
10
3780
 9 
15.5
12 Ji
19.2
Analyzed
10 1
18.6 h.6
16.0
22.0
10 1
18.5 5.0
16.0
22.0
9
139
10
i75
7
ko
16
86
9
35
h
116
10
102
10
lilO
7
16
6U
9
29
h
92

~
~

-------
           Table 5  ->



REACTOR TEST ANALYTICAL DATA
Rate KJbced
of Liquor Effluent Concentrations,
Test Flow ing/L
No. ml/min SS VSS TKN NH3-N NC^-N
Test 9: Oct. 25-30, 1967*. D, C, 20
No. of Obs. 5 1 1 111
Mean 19.3 880 760 5.6 3.U 0.1
Min. 11*.6
Max. 22.7 All effluent analyses
Test 10: Oct. 27-?9, 196? No Data Analyzed
Test 11: Oct. 27-29, 1967 No Data Analyzed
Tesi 12 t Kov. 1U-22, 1967 . D, C, 20
No. of Obs. 6 5 U
Mean 16.0 2630 2385
Min. 11* .9 2300 201*0
Max. 16.5 3100 2910
Test 13a: Nov. U*-30, 1967. N, C, 20
No. of Obs. 13 13 13
Mean 13.1 5165 1*710
Min. U.7 1*500 1,100
Max. U*.5 61*50 601*0
Test 13b: Nov. 30-Dec. U, 1967. N. V, 20
No. of Obs. 10 10 10 --
Mean 12.9 1*1*18 1*030
Min. 9.7 3390 3030
Max. H*.8 5080 1*620
Test 11*: Dec. 5-Ut, 1967. D, C, 20
No. of Obs. 9 11-
Mean 18.5 3bOO 3000
Min. 13.7
Max. 20.5

N03-N DO

1*
0.2 28

on 10/30/67



9
0.3
0.1
1.7

13
18 J*
8.0
22.3

10
18.3
13.5
22.5

8
0.1
0.1
0.2

SS


(BOD)





8
Ih
16
81*

13
1*7
1*
116

9
hi
30
58

9
36
5U
16
ng/1

VSS TP

1
0.9





7
35
16
76

12
37
1*
96

9
37
30
U8

9
33
50
16

-------
                                Table 5  A

                     REACTOR TEST ANALYTICAL DATA
 Test

  No.
Rate
of
Flow
Mixed
Liquor
mgA
Effluent Concentrations, rog/1

          ral/min    SS    VSS   TKN   NH3-N   N02-N   N03-N  DO   SS   VSS    TP
Test 151  Dec. 18,  196? - Jan. 1, 1968
                                           No Data Analyzed
Test 16:  Dec.  19, 1967 - Jan. 6, 1968   D, C, 20

No. of Obs.   15     2     2
Mean         18.1  2UOO   2220
Mln.         Ui.2  1390   1270
Max.         19.6  31*10   3170
                                                      U.5
                                                      3.U
Test 17:  Dec. 19,  196? - Jan. 1, 1968.  D, C, 20

No. of Obs.  12      82                             8
Mean         17.5   ?&<>   2U30                          I5.li
Min.         13.2   1870   1690                           9.0
Max.         20.0   31*10   3170                          20.0
Test 18:  Jan. 25 - Feb. Hi, 1968.  D, C, 20
No. of Obs.  15
Mean        13.8
Mln.

Max.
                   uuii       i
                  3230  2350   7,8   U.i     .01
            11.6    1610  1130

            17.3    5810  3980
13    1    11    11
 -3<&79    *
 0.0 .52 %  12    12
1.1*
           21*0  230
                     1
                     1.3
                     0*6
                     (OP)
Test 19a:  Jan. 23  - Feb. 9, 1968.  D, C, 20C
No. of Obs.  13    10    10
Mean        10.0  1751  1335
Min.         7.8  1230   950
Max.        11.5  28UO  2060
1
2.6


1
0.03


11
0.3
0.1
2.6
8 8
81 6k
32 16
560 U70
Test 19b:  Feb. 10 - Mar. 7, 1968.  D, C, 20C

No. of Obs.  25    16     16
Mean        17.9  2750 2350
Mln.        13.2  18UO 1590
Max.        23.2  3670 3170
                                                      17     1   13    13
                                                      0.6  ,123.  51    1*5
                                                      0.0  (COD)   h     U
                                                      2.3       120   112

-------
           Table 5



REACTOR TEST ANALYTICAL DATA
Bate
of
Test Flow
No. ml/rain
Test 19c: Mar. 8 -
No. of Obs. 6
Mean 17.9
Min. 17.3
Max. 18.5
KtJted
Liquor
mgA
SS VSS TKN
. Mar. 13, 1968 .
3 3
3550 3030
3110 2660
U170 3510
Effluent Concentrations,
NH3-N N02-N N03-N
D, C, 20
3
0.1
0.1
0.2
DO SS
3
71
28
96
ing/1
VSS TP
3
U5
16
8U
Test 20t Feb. 1U - April 1, 1968 . N, V, 20
No. of Obs. hO
Mean 11.6
Min. 10.2
Max. 17.2
25 25 1
Ii885 3800 1.2
3860 2920
63UO 5050
Test 21: Feb. 13 - April 1, 1968 
No. of Obs. U5
Mean 11.2
Min. 7.3
Max. 18.0
Test 22s March 18
Test 22Aat Feb. lb
No. of Obs. 20
Mean 16.3
Min. 10.6
Max. 20.5
Test 22Abs March
No. of Obs. 13
Mean llt.7
Min. UuO
Max. 15.7
25 25
3700 3050
2000 1610
6660 5830
- March 29, 1968
- March 5, 1968.
12 12
3390 2810
17UO U*80
U700 U100
12 - April 1, 1968
8 8
3165 2800
2750 2300
3590 3200
21
20.0
16.5
25.8
, C, 20
22
20.6
5.5
29
No Data Analysed
D, C, 20
13
0.6
0.1
1.2
. D, V, 20
3
0.2
0.1
0.3
22
50
h
21
52
0
536
11
U5
0
76
1 U
,39 , 52
(COD) j^
6k
22
37
0
108
21 1
38 1.1
0
1*20
n
uo
0
76
h
144
2U

-------
           Table 5   I



REACTOR TEST ANALYTICAL DATA
Test
No.
Rate
of
Flow
ml/min
Test 23: April 3
V
No. of
Mean
Min.
Max.
No. of
Mean
Min.
Max.
No? of
Mean
Min.
Max.

No. of
Mean
Min.
Max

Obs. 16
lli.7
10.5
2U.O
Obs. 29
20.6
__

Obs. 29
20.6
...

(April 28
Obs. 8
2iuO

~
Mi
Liq
ng
SS
- May 9

16
3l|)|Q
1520
U720
16
nao
700
2050
16
2300
1310
2660
-May 9,
9
350
UtO
880
zed
uor
A
VSS TKN NH3-N
, 1968 . C* 20

16
2920
1330
1*130
16
1290
620
1920
16
1990
1100
2260
1968)
9
310
90
800
Effluent Concentrations,

N02-N N03-N DO


28
20.6
1U.O
21; .5
2U
0.6
0.1
2J,
28
7.8
2.8
15.6

11
0.6
0.1
2 Ji

SS


3
13
7
16
U
72
25
128
5
32
10
52"

1
29


TOgA

VSS TP


3
13
7
16
h
57
22
76
5
21
9
Uo

i
23



-------
                                Table  5  H

                     REACTOR TEST ANALTTICAL DATA
           Rate        Mixed
            of        Liquor                 Effluent Concentrations,  rog/1
 Test      Flow
  No.     nl/win    SS    VSS   TKN   NI^-N   N02-N   N03-N COP   S3  VSS   TP  pH
                              
Test 23.;  May 3, 1968   C, 20

 HI i
Ho. of Obs.  1       1111       lllllll
            13.9   3120  2720   2.8    1.8     0.7    17.3   UO    7      7    1.8   7.7


N^'of Obs.  1       111      1       1      1      11111
            20.3   1700  1590   8.8    $.U-     0.0    0.1    57   *5     23    1.8   7.8

 Not
No. of Obs.  1       111      1       11      1    1      1     1    1
            20.3   2570  2220   2.9    0.5     0.0    6.3    35   10      9    1.7   8.0


No^'of Obs.  1       1111       111111010
            2U.O    UOO   380   6.5    3.1     0.1    0.1    56   29     23    1.8   7.8

 Test 21 1  May 10 - May 28, 1968.   V,  20
No. of Obs.  7      U     11                          10
Mean        11.1*  UlliO   3500                         22.9
Mln.         9.7  3M>0   2781                         17.3
Max.        13.2  5200   U263                         25.0
No. of Obs.  5      U     11                           8
Mean        17.0  1830   1630                          OJi
Min.            3580   11*1*0                          0.1
Max.            2100   18UO                          0.7
No. of Obs.  5      U     11                          10
Mean        17.0  1760   U*60                          8.5
Min.            1280   1000                          6.3
Max.            21*00   2020                         11.0

 D2:
No. of Obs.  5                                          9
Mean        19.5   (Wash                               2.3
Min.                 Out)                            0.1
Max.                                             1*.3

-------
           Table 5   



REACTOR TEST ANALmCAL DATA
Test
Rate
of
Flow
No. ral/min
Test 25:
NJ
No. of Obs,
Mean
Mln.
Max.
D:
June 10

. 57
15.1
11.0
21.0

No. of Obs. 56
Mean
Min.
Max.
Test 25bJ
NJ
21.3
19.3
26 Ji
August

No. of Obs. 10
Mean
Min.
Max.
D:
13.7
12.1
16.2

No. of Obs. 10
Mean
Mln.
Max.
Test 25cj
NJ
No. of Obs
Mean
Mln,
Max.
DJ
No. of Obs
Mean
Min.
Max.
19.7
18.8
20 J
August

. 2U
Hu9
12.1
16 Jt

. 2U
20.2
18.5
21.9
Ki
Liq
Dig
SS
, 1968

38
U730
3200
61i20

38
12?0
1*00
1900
9, 1968

5
3500
2920
3890

5
158U
1070
2220
xed
uor
A
Effluent

VSS TKN NH3-N N02-N
- Aug. 8, 1968

37
3900
2680
5U10

35
1130
520
1680
- August 18,

5
2980
2U20
3280

5
1362
880
1870
19, 1968 - Sept. 13,

16
3130
2360
3590

16
1150
380
2670

16
2715
2080
3160

16
1000
320
2330
. V, 20






19 2
1.9 0.0
3.8 0.0
8.8 0.1
1968 . V, 20






6
3b
1.8
U.9
1968 . V, 20





13
0.7
0.2
1.3
Concentrations ,

N03-N DO



(20.0)



31 1
0.3 .30 %
0.1 (COD)
0.7



(20.0)



6
0.3
0.1
o.5


(19.5)



18
0.2
0.1
OJt

SS


32
20
h
U5

31
6U
25
11*0


5
liO
10
70

5
U5
27
65


12
25
6
61

15
U5
15
68
Ttlg/1

VSS TP


27
15
2
35

28
1;9
10
128


5
30
8
57

5
35
25
56


11
20
6
50

13
38
lit
Sh

-------
           Table 5



REACTOR TEST ANALYTICAL DATA
Test
No.
Test 25at

D


Test 25c:
N

D


w
Test 26a:
N:
No. of Obs
Mean
Min.
Max.
Dt
No. of Obs
Mean
Min.
Max.
Test 26b:
N:
No. of Obs
Mean
Min.
Max.
No. of Obs
Mean
Min.
Max.
Bate
of
Flow
ml/rain
August

Hi .2
(20.5)

Sept. 5
HiJi

20.3


Ki
Liq
ing
SS
6, 1968

830


, 1968
3160

700


aed
pior
'A
VSS TKN
Effluent Concentrations,

NH3-N N02-N
(Supplementary Data) . V,

790 9.6



U.9 0.1


(Supplementary Data) , V,
2720 U.9

580 h.5


Oct. 27 - Nov. 7, 1968.

. 11
16.0
Ui.l
17.7

. 11
2li.6
22 M
2^.8
Nov. Hi

. 17
13.7
11 J
15.6
. 17
22.2
20 Ji
23.8

U
Ii970
U7UO
5530

h
390
250
560

h
Ii350
U080
U820

U
360
210
500
i - Dec. 3, 1968.

5
U690
3620
5360
5
820
700
1000

5
Iil80
3360
It8l0
5
770
590
1000
0.1 0.0

0.8 0.0


V, 20

6
0.6
O.U
0.8

li
IJi
1.1
2.0
v, 15

li
O.U
0.3
O.U
5
1.1
0.1
1.8

N03-N DO
20
29
0.3 (BOD)
63
(COD)
20
19.5 -
27
0.1 (BOD)
68
(COD)


6
23.6
21.5
26.5

6
0.2
0.0
0.6


5
20.2
16.0
2li.O
5
0.3
0.1
0.6

SS


Ui



20

38




li
2U
11
lil

U
17
12
22


5
3li
Hi
60
5
18
7
23
mg/1

VSS TP


 2.1



17 

3li l.li




li
20
10
37

li
16
9
20


5
19
10
51i
5
15
0
22

-------
           Table 5  / "



REACTOR TEST ANALYTICAL DATA
Test
Rate
of
iriou
&O0 u AT Awn
No. ml/min
Test 27a:
NJ
No. of Obs
Mean
Min.
Max.
D:
No. of Obs
Mean
Min.
Max.
Test 27bt
N:
No. of Obs
Mean
Min.
Max.
D:
No. of Obs
Mean
Min.
Max.
Test 27c:
N:
No. of Obs
Mean
Min.
Max.
D:
No. of Obs
Mean
Min.
Max.
Mixed
Liquor
 /i

SS
lUg/A
VSS TKN
Jan. 13 - Feb. 12, 1969. V

. 29
16.1
13.2
I8.lt

. 31
25.2
19.5
31* .5
March

. 11
llt.l
13.1
15.7

. U
21.3
19.7
25.9
March

. 20
7.1
5.7
9.3

. 19
11.0
6.3
12.6

15
31*80
2820
U050

13
830
Uio
1710

U*
3020
2ltlO
3880

11 2
61*0 2.5
31*0 2.0
1390 3.0
3 - March lit, 1969.

It
261tO
2280
281tO

It
600
520
700

1*
2350
2090
2500

h
5fco
1*30
620
15 - April It, 1969.

3
2UtO
1550
2570

2
1600
1560
161*0

1*
1825
1390
2050

2
31*1*0
1390
11*90
Effluent Concentrations,
NH3-N N02-N 
, 20

17
0.3
0.0
0.9

11*
1.0
0.6
1.6
V, 10

5
0.8
O.lt
1.8

5
1.0
0.8
1.6
V, 10

6
0.7
0.3
1.3

9
0.7
o.U
1.2
N03-N DO


18
16.1
12.lt
21.1

18
0.1
0.0
0.3


5
11* .8
13.6
15.8

5
0.3
0.1
0.6


8
16.6
iu.it
19.8

9
0.1
0.0
0.2
SS


8
12
2
23

13
22
10
33


It
10
7
13

h
18
U
27


2
10
9
12

2
12
12
13
rag/1
VSS TP


It
8
1*
13

11
20
12
29


1*
7
1*
12

It
15
9
2lt


l
8



1
12



-------
                             Table 5



                  REACTOR TEST ANALYTICAL DATA
Rate Mixed
of Liquor
Test Flow Etg/1
No. nl/mln SS VSS TKN
Effluent Concentrations, ng/1

KH3-N JK>2-N

N03-N DO SS VSS TP
Test 27d: April 17 - May Ui, 1969. V, 10
N:
No. of Obs. 26 3 3
Mean 16.2 2300 1980
Min. 13.0 1990 17ltO
Max. 18.3 251*0 211*0
D:
No. of Obs. 2h 3 3
Mean 2lu8 1220 1065
Min. 20.3 665 585
Max. 27.9 I81i0 1590
Test 28a: June 13 - June 22, 1969.
(Nt) *
No. of Obs. 9
Mean 19Ji
Min. 12.6
Max. 22.7
No. of Obs. 9 2 2
Mean 28.0 2275 1965
Min. 19.7 I960 1710
Max. 32.0 2590 2220
Test 28b; August h - August Id, 1969
(Nt)*
No. of Obs. 15
Mean 21.5
Min. 16.6
Max. 23.6
D:
No. of Obs. 15 U 11
Mean 30.5 1010 863
Min. 21*. 9 550 U70
Max. 33.3 1390 1113

5
0.7
O.U
1.2

5
0.9
0.8
1.1
C, 10

5
0.5
0.2
0.9
5
0.5
0.2
1.2
. C, 10

U
0.5
Oj*
o.5
U
0.7
0.3
1.3

5 22
lii.3 8 7
10.8 U 3
16.6" 12 12

5 21
0.2 11 15
0.1 6
0.2 16


6
21.1
19.8
22.2
6
0.3
0.2
0.5


U
23.6
2U.2
U
0.3
0.3
OJi
* See discussion section for significance of these data.

-------
D.  Experimental Results of Reaction Tests




1.  General Test Conditions




     A list of the reaction tests including the period of operation, type of test,




temperature, and type of flow is presented in Table 3, Listing of Reactor  Testa.




The tests have been numbered chronologically and it is apparent that, at times,




two or more tests were conducted simultaneously.  For the l?ype of Test, the N




or D designates nitrification or denitrificqtion respectively.  For the Type of




Flow, C represents a constant rate of flow while V is for variable flow




conditions.  Peed Solution designations described at the bottom of the table




represent concentrations of various substances mixed with dechlorinated City of




!inneapolis tap water for use as raw feed solutions for the reactors.




     Operational data from all of the reactor tests are shown in Table 4.




The Reaction Tank is the aeration tank when used with a nitrification test and



is a mixed  anaerobic tank with the denitrification process.   The reaction  tank




volume is given in liters, detention time (DT) in hours, and loading in terms




of either of two ratios.  The ratio, BOD/MLVSS, is actually the pounds of




5-day 20 C BOD of the raw feed added to the reactor per day divided by the




pounds of mixed liquor volatile suspended solids in the system.  The term SA




is a similar ratio but in the weight of mixed liquor suspended solids in the




system over the weight of 5-day 20 C BOD fed per day with the raw feed.  The




settling tank operational data are given as the tank volume in liters, the




detention time (DT) in hours, and the surface settling rate (SSR) as gallons




per day per square foot.  This latter unit is found by dividing the rate of flow




by the surface area of the tank.




     Included in Table 5 Reactor Test Analytical Data, are flow data, mixed




liquor total and volatile suspended solids data, and the effluent analysis




data.  Effluent concentrations are given as follows:
                                 - 21  -

-------
     TKN:   total Kjeldahl nitrogen as N




     NIL-N: ammonia nitrogen as N




     NOp-N: nitrite nitrogen as N




     NCL-N: nitrate nitrogen as N




     DO:    dissolved oxygen




     S3:    suspended solids




     VSS:   volatile suspended solids




     TP:    total phosphorus as P




Some effluent BOD (5-day, 20 C) and COD data also have  been included in the




DO column and are specifically so designated.  Some ortho-phosphate concentra-




tions are shown as OP in the TP column.  Because of operational difficulties




encountered during the tests, the data were analyzed  only when it was




considered that equilibrium conditions had been reached.  Consequently the




time period of each test as shown in Table 3 and the  dates  shown in Table 5




may not be the same.  The dates shown in Table 5 represent  the periods over




which the listed data were collected.  The letters and numbers following the




dates designate the temperature of operation in degrees centigrade, the




pattern of flow as being constant (C) or variable (V), and  whether the




objective of the test was to achieve nitrification (N) or denitrification (D).




     Additional denitrification data are presented in Table 6, Reactor




Denitrification Test Data.  For each denitrification  test the influent nitrate




concentration is given and the carbon source (BOD) is given as either milk




solids (M) or methanol (L).  Three characteristics of the reactor tank opera-




tion are presented:  the organic loading rate (For BOD/MLVSS) as listed




previously in Table 4,  the nitrate reduction rate as mg nitrate-N removed




per hour per g of I.ILSS in the reaction tank (mg N/g;.IL3S/hr);  and the ;catio




of BOD,- in the carbon source added to the reaction tank to  the nitrate-IJ
                                  - 22 -

-------
             Table 6.  Reactor Denitrification Test Data

Test
No.


9
12
14
16
17
18
19a
19b
19c
22Aa
22Ab
23 :D
23 ^
24 :K
25a1
25a
25b
25c
25c
26e
26b
27a
2?b
2?c
27d
28a
28b
t

Peed
Nitrate
mg/l-N


19.9
19.9
42.3
24.9
24.9
21.3
21.3
25.5
21.3
25.5
21.3
20.6
7.8
22.9
(20.0)
20.0
(20.0)
(19.5)
19.5
23.6
20.2
16.1
14.8
16.6
14.3
21.1
23.6

Carbon*
source


M
11
M
M
M
M
M
M
M
K
M
M
M
M
M
M
ML
L
L
L
L
L
L
L
L
L
L
Reaction Tank
Loading
BOD/ML VSS
F

1.42
0.17
0.31
0.20
0.08
0.15
0.20
0.20
0.15
0.34
0.31
0.26
0.14
0.19
0.32
0.46
0.25
0.41
0.43
1.45
0.66
0.86
0.81
0.16
0.49
0.27
0.43
Nitrate
reduction rate
mg N/g MLSS/hr
R

11.2
1.4
2.8
1.5
0.3
1.1
1.5
2.0
1.3
3.1
2.6
2.4
1.1
1.7
2.8
4.4
2.0
2.9
5.0
11.3
4.0
3.7
4.1
0.9
1.4
2.1
6.0
Ratio:**
BOD /Nitrate-N
BOD/NA
Applied
4.22
4.22
4.11
3.13
1.45
3.94
3.94
3.29
3.94
3.29
3.94
3.41
3.25
3.82
3.80
3.73
4.02
3.50
3.85
4.39
5.96
6.78
6.66
6.35
11.60
4.40
2.58
BOD/N
Removed
4.26
4.28
4.12
3.82
3.79
4.01
4.01
3.37
3.96
3.37
3.98
3.52
3.52
3.90
3.86
3.78
4.08
3.54
3.97
4.52
6.07
6.82
6.80
6.39
11.80
4.46
2.59
 * Carbon source: il Milk solids
                  L Methanol
** BODj. corrected to that available to the nitrates after
      *      depletion of D.O.

-------
applied (BOD/Ml) QC nitrate-N removed (BOD/N).  It should be noted that the

BODS in the BOD/N ratio computations has been corrected to that available to

the nitrates after deducting an amount required to deoxygenate the incoming

flows.  The rates of nitrate reduction and organic loading rates are plotted

as Figure 10.

2.  Tests 1, 2, 3 and 4

     These tests were conducted simultaneously for the purpose of determining

the concentration of mixed liquor suspended solids (ilLSS) necessary to maintain

a nitrifying activated sludge system when the aeration time was approximately

4 hours.  The test data and conditions shown  in Tables 3> 4 and 5 show that the

hydraulic loadings for each system were approximately the same.  The only

essential difference in the systems was in the concentrations of LILSS in each

of the reactors to give varying reaction tank loading parameters.

     It was difficult to control the solids in these tests because of sludge

bulking, and these poor sludge settling conditions were indicative of similar

operating problems which would be encountered throughout the reactor test

program.

     Of these four tests only in Test 1 was there any significant degree of

nitrification.  Downing and Hopwood^  ' showed the minimum residence time  (tj,)

of the mixed liquor to achieve nitrification  as:

                          tp = AS
                           ^   kS

                          AS = change in concentration of IvILSS

                            S = concentration  of MLSS

                           k = growth rate constant of nitrosomonas.

Johnson and  Schroepfwr2' indicated  a loading rate of 0.35 Ibs/day/lb 1.ILSS

should not be exceeded to obtain continuous nitrification.  Only in Test 1 was

the  loading  rate within this limit and the computed minimum aeration time  was
                                   - 23 -

-------
4.1 hrs compared to an actual 4.2 hrs.  It was observed that the nitrate




concentration in Test 1 was gradually decreasing so that the fact that opera-




tion was very close to the limiting conditions was borne out by theoretical




and experimental results.



     In Teats 2, 3 and 4 the loading rates all exceeded the assumed maxiiaum




of 0.35 a*1** ^he computed minimum aeration times in all cases exceeded the




actual operating conditions.  The fact  that there was any nitrification at all




was because the sludge used initially did contain nitrifying bacteria.  Again




the general observation from these tests is that the minimum essential aeration




period and loading rate for nitrification as  defined in previous work is in




agreement with these results.




3.  Tests 5 and 6



     These tests were  conducted simultaneously using the  sludge remaining from




Testa 1 and 2 respectively.  It was  intended  to  operate each unit with an




aeration time of 6 hours and a  MLSS  concentration  of 3000 mg/1.  The difference




between the two systems was that  prior  to the start  of the  tests, the sludge




used for Test 6 was  chlorinated in an attempt to reduce  the sludge  bulking.




     With the lower  loading conditions  used in Test  5  compared to the previous




 tests, nitrification was maintained  at  a high concentration.   Severe bulking




 again occurred, and  the  sludge  was chlorinated with 75 Eg/I residual chlorine




 on September  22.   The  result  of chlorination was  to  inhibit the nitrifiers' as




 evidenced by  nitrate concentrations  near zero shortly thereafter.   The  sludge




 volume  index  of the  sludge did not improve  immediately but  stayed well  over




 200 for  about 10 days, and finally after about 20 days it had decreased  to  100.




 Assuming that the chlorine either killed or prevented further growth of




 (filamentous) organisms causing the  bulking,  it could take  a number of days to




 wash out the  undesirable cell debris.  By assuming a net specific  growth rate

-------
of the sludge of 0.20 per day, it may be shown that due to wash-out the sludge



would contain only 15 to 20 per cent of the original filaments after 10 days.



It is conceivable that this lower concentration was sufficient to allow the



solids to compact more.  After approximately 20 days the nitrate concentration



shored an increase indicating that the nitrifiers were not completely destroyed.



     The data from Test 6 were not analyzed but it was again shown that



chlorination did not completely destroy the nitrifiers, and the sludge volume



index did not show improvement until after approximately 15 days of operation.



Initially the nitrate concentration was less than 0.5 nig/1 and then gradually



increased to 1/4..0 mg/1 after 15 days.



4.  Tests 7 and 10



      ^ests 7 and- 10 were nitrification tests and an attempt again was made to



obtain nitrification at a 4-hour detention time.  Sludge from the pilot plant



was used and with a mean MLSS concentration of 3837 nig/1 the nitrate concentra-



tion was kept at an average value of 18.6 mg/1.  Again the actual detention



time exceeded the computed minimum and the load ratio of 0.30 was less than



the prescribed maximum.  The test was concluded on October 25.



     The sludge from Test 7 "as used for Test 10 and the operating conditions



were changed to a 6-hour retention time and a MLSS concentration of 2000 iag/1.



At the end of Test 7 the sludge volume index (SVT) had gone to 220, and after



only 2 days of operation with this sludge it was decided it was too difficult



to continue operations and the test was terminated.  No data were analyzed from



this period.



5-  Tests 8 and 11



     Test 8 was run in parallel with Test 7 and was a nitrification test



differing from Test 7 only in using a higher MLSS concentration.  With these



lower loadings the effluent nitrate concentration was high.  The effluent



concentrations were almost exactly the same as for Test 7 where the loading
                                -25-

-------
rate was somewhat higher.  Throughou-t this test the SVI was low and the test




was terminated on October 26 when a line broke.



     The sludge from Test 8 was used for Test 11 and it was intended to use




this sludge with a detention time of 4 hours and the ML33 concentration




reduced to 3000 mg/1.  The test was only operated for two days because of a




sudden increase in the .371.  It is not known why the SVI suddenly increased.




Although higher loadings often result in high SVI values, it is unlikely that




the response would come in only two days of operation.




6.  Test 9



     This was the first denitrification test and was operated with  a sodium




nitrate solution together wich a dry milk  solids carbon source.  For unexplain-




able reasons the mixed liquor  solids washed out of the reaction tank  and  the




test had to be  terminated after five,, days.



     During the five day period of  operation the effluent nitrate concentration




decreased gradually  to 0.2 mg/1 on  the day on  which the data are reported.




As shown in Table 6  the BOI>5/nitrate-N  (BOD/N)  ratio used was 4.26  and the




high sludge loading  resulted in a high rate of nitrate reduction.




 7.  Test 12



     This  test  was a denitrification test similar  to Test  9 whereby a mixture  of




 milk solids and sodium nitrate was  added to an aerobic mixed reactor.   The




 mixed  liquor  solids  were obtained  from a nitrifying activated sludge plant




 but adapted well to  denitrifying conditions after  only 2 days of  operation.




 The holding time in the  reaction tank was 5.2 hours in contrast to  2.0 hours




 in Test 9.   At this longer holding time the solids did not wash out of the




 system but there were signs of sludge bulking at the end of the test.   The




 BOD/N ratio was 4.28 and the nitrate reduction rate was low corresponding to




 the low sludge loading rate.
                                     - 26 -

-------
8.  Tests 13a and 13b



     Test 13a was a constant flow nitrification teat to develop a good sludge




to be used in the subsequent variable flow test, Test 13b.  The aeration time




and MLVSS were kept quite high so that the BOL/LILVSS ratio was only 0.1?.  As




expected, consistent nitrification was achieved.




     After 16 days of operation the feed pump was put on a variable flow cycle.




The variable flow cycle was approximately as shown in Figure 7 for Test 20.




The ratios of maximum to average and minimum to average flow were 1.7 and 0.5




respectively.  With the particular conditions used in these tests, the mean




nitrate concentration in the daily composite samples was the same as that




obtained with constant flow conditions.  It would appear that variable flow




in this case had no effect, but since there were a number of mechanical




equipment problems during the test and sludge bulking near the end of the




period, the results were not conclusive.




9.  Test 14



     During this constant flow denitrification  test the ratio of BOD/N was




4.12, and although somewhat less than that used previously, satisfactory




denitrification was achieved.  Inadvertently the sodium nitrate and milk




solids concentrations were made up to essentially twice the intended concentra-




tions which placed a higher load on the sludge in the reactor.  The BOD/MLVS3




and SA values were 0.31 and 3.5 respectively and very  similar to conventional




activated sludge.  The nitrate reduction rate of the sludge was 2.8 as shown




in Table -6.




10.  Tests 16 and 17



     These tests were denitrification tests using milk solids as a carbon  source




and sodium nitrate as the nitrate  source.  Lower ratios of BOD/N were used than




in previous  tests as shown  in Table 6.  Although the BOD/N-applied ratios  for
                                  -27-

-------
the two tests (computed using the nitrate N added) differed greatly, the



ratios were essentially the same when computed using the nitrate removed.



It would appear that the optimum ratio of BOD/N is approximately 3.80 and



that the magnitude of nitrate reduction is, therefore, primarily a function of



the BQD/N ratio.  The effect of a particular sludge loading rate is not to



effect a greater or lesser amount of substrate reduction but to determine the




effluent quality in terms of some parameter such as BOD,-.




11.  Test 18



     This was a denitrification test operated at a BOD/N ratio higher than



the estimated optimum, and good denitrification was achieved.  The effluent



obtained in this test was quite turbid as  indicated by the  S3 concentration.



BOD and COD data were obtained on one day  and it is evident that a good



quality effluent was being produced in terms of total BOD,,  and that the  soluble



BOD,, would certainly be  somewhat less than the 16 mg/1.  Complete nitrogen and



phosphorus data were also obtained on the  same day  as the BOD-COD data.



     The total of the organic and ammonia  nitrogen  (TKN) entering the  system



was 7.0 mg/1 while  the phosphorus in the feed was 1.2 mg/1. Because of  the



high effluent  solids the TKN of  the effluent exceeded that  of the influent but



the soluble ammonia was  4.1  mg/1.  The  total phosphorus  in  the  effluent  was



also high  because  of the effluent  solids but  the  ortho-phosphate (OP)  was



0.6 mg/1.   Some  loss of influent TKN  and TP were  evident but where  the sum



 of all forms  of  nitrogen in the  effluent must  be  low it is  evident  that  a



carbon source containing little or  no nitrogen is necessary.




 12.   'i'ests I9a,  I9b,  I9c



      These three tests were conducted in series with the same  sludge and same



 units.  The differences in the tests were in the hydraulic  and  organic  loadings



 and in the BOD/N ratios used in the feed.   Essentially complete denitrification




 was obtained in all tests.
                                 - 28 -

-------
           I9a and I9c were conducted with the same BOD/N ratio and with




similar sludge loading rates.  The principal difference was in the detention times




and mixed liquor solids concentrations in the reactors.  It is quite evident




that either combination of time and concentration -.vas satisfactory.




     Test 19b was operated at a similar sludge loading but at a reduced BOD/DI




ratio and the denitrification held up very well.  Consequently the ratio




considered optimum previously (3.8) should be modified to the ratio of 3.4.




     In all tests there was a high concentration of S3 in the effluent, but




it was noted on the log sheets that towards the end of Test 19b the character-




istics of the sludge changed suddenly  to produce a very clean effluent but a




very fluffy sludge.




13.  1'ests 20 and 21




     These two tests were nitrification tests run in parallel.  The plants




were started at approximately the same time with very similar operating conditions




and constant flow rates.  After a period of equilibrium operation the unit of




Test 20 was put on a variable flow cycle as shown on Figure 7 while the other




unit for Test 21 was continued with a constant flow rate.  For the variable flow




the maximum to average rate was 1.73 and the minimum to average rate was 0.49-




     The data shown in Table 5 offer no conclusive evidence of an appreciable




difference in nitrification in the two plants.  In both plants the effluent




solids were quite high but the nitrate concentrations uere about the same.




14.  Tests 22Aa and 22Ab




     The denitrifying sludge from Test 18 was used in these tests.  Test 22Aa




was conducted at a constant flow and then when the input flow rate was changed




to a varisble cycle the test period was designated as Test 22Ab.  Other




operating parameters during the tests were the same except that on March 8,




after the end of Test 22Aa and shortly before com/aencing Test 22Ab, the ratio of




BOD/N was changed.  It was considered at the time that denitrification was not
                                 - 29 -

-------
as complete as it should have been and therefore  the ratio was actually




increased.  The decision to do this was probably  a questionable one since the




mean value was 0,6 and the mean during Test  22Ab  with  the higher ratio was only




decreased to 0.2.  However, the variation during  the latter test was less.




     An analysis of the data from these tests  is  significant insofar as the




efficiency of denitrification is concerned and in comparing the two tests where




Test 22Aa was at a constant flow and Test 22Ab was operated at a variable flow.




Denitrification test data are shown in Tables  3,  4, 5  and 6 and overall there




seems little difference in the nitrate reduction  efficiency in either of the




two tests.  In both tests the mean effluent  nitrate concentration was less than




1.0 mg/1.  Satisfactory denitrification was  achieved in Test 22Aa at a BOD/N




ratio of only 3.4.but only slightly better reduction was achieved in Tests 22Ab




at a ratio of 4.0.  Under these conditions variable flow seemed to have little




effect.




15.  Test 23




     Test 23 was the first test where nitrification and denitrification plants




were operated in series.  Actually four plants were operated in series:  the




first was for nitrification;  the second was denitrification using milk solids




as the carbon source;  the third was for nitrification of the remaining aomonia




in the denitrified effluent;  and the fourth was  for final denitrification




using milk solids again as the carbon source.   Raw waste flows were added to the




first, second, and fourth reactors so that the total flow being processed




increased progressively through the plant as shown in  Table 5.




     As shown in Table 4, the low loading conditions used for the first unit




assured reasonably complete nitrification.   The usual  criterion of a low BOB/




MLVS ratio to assure nitrification was not applicable  for the third stage since




essentially a very low BOD concentration entered  the unit.  With the low BOD,




the growth in the third unit was very low and  the effluent solids loss was
                                    - 30 -

-------
sufficient to maintain a reasonably constant solids concentration.  Solids



carryover from the second stage also helped to maintain a sludge mass.  A



holding time of less than 2 hours was used in the second nitrification stage



and the optimum time may have been even less.  Denitrification loading conditions



are also shown in Table 4 and in Table 6.  The long detention time in the first



denitrification unit was very likely unnecessary but only 1.6 hours was used



for the second denitrification stage.  The BOD/N ratios were close to the



optimum based on previous experience.



     The analytical data shown in Table 5 consists of the usual mean values but



also includes a complete set of data for what is considered as an equilibrium



situation.  The progression of total nitrogen through the plant is also shown



in Table 7 where influent concentration in the total influent and effluent flows



are shown.  The tabulation of mean data are indicative of the overall general



performance but the equilibrium test data obtained on May 3 are most significant.



The data are summarized in Tables 5 and 7





            Table 7.  Equilibrium nitrogen data, Test 23 May 3, 1968


                         Nitrogen concentration, mg/1 N
Reactor No.
Influent
Effluent
Raw-waste
feed
Per cent
removal
N1
27.0
20.8
27-0
23
D1
22.6
8.9
7.7
67
N2
8.9
9.2
-
66
D2
11.7
6.7
3.8
86
     The ammonia-N from reactor N1 was higher than expected and it is certain



this could be maintained at less than 1.0 mg/1.  Approximately 0.7 ag/1 of the



effluent N concentration was in the SS.



     In the first denitrification stage the total removal by the system was


                              N
67 p
-------
     The second stage nitrification unit operated to produce a well nitrified
effluent and since it was estimated that the effluent solids accounted for all
solids growth there should be essentially no removal through the unit (actually
a slight negative removal is shown due to ordinary sampling variations).
     The second denitrification stage produced a low nitrate concentration
but because of the introduction of raw waste the total effluent N was 6.7 mg/1
for an overall removal of 86 per cent.  Actually the total soluble N was only
about 3.7 mg/1.  The effect of the first two stages was to remove 18.1 mg/1 N
and the remaining two stages removed an additional 2.3 i&gA ^ar a total of
20.3 mg/1-
     Phosphorus was affected only slightly through the plant and the effluent
COD values were indicative of well stabilized effluents.
16.  Test 2k
     Test 24 was a continuation of Test 23 but with variable flow conditions.
Denitrification was accomplished with milk solids as the carbon source as
shown in Table 3  Based on the results from Test 20 the expected maximum
nitrate concentration from the first reactor was assumed to occur 6 hours
prior to the time of maximum flow.  Consequently the variable flow cycle of
raw waste into the second unit was set such that the maximum flow rate (or
maximum carbon load) was set to occur 6 hours prior to the maximum flow
into the first reactor.  With this arrangement it was expected to match the
maximum carbon feed with the maximum nitrate load.
     As shown in Table 4 the first stage nitrification had a long detention time,
and this was due to the unintentional use of a low setting on the feed pump.
This also gave an unnecessarily long detention time in the second unit.  The
two hour holding times in the last two units were reasonable.
     The mean data shown in Table 5 indicate that reasonably good operation was
obtained from the first three reactors, but the last reactor gave poor results
                                -32-

-------
because of an unexplained tendency to lose the mixed liquor solids in the



effluent.  In general the system operated reasonably well under variable flow



conditions.  The problems with the fourth reactor cannot be attributed solely




due to the variable flow.



17.  Tests 25a, 25b and 25c



     These tests were two stage operations, the first stage being a nitrifica-



tion unit and the second a denitrification plant.  Variable flow was used to



both units with the maximum flow to the second unit lagging the first by 6



 hours.  The ratio of maximum to average flow was approximately 1.4 and the



ratio of minimum to average was 0.6.  As shown in Table 3> the main differences



in the tests were in the feed solutions to the denitrification plants.  Test



25a used a milk solids solution, Test 25b used a mixture of milk and methanol



and in Test 25c only methanol was used.  Reasonably long detention times were




used as shown in Table 4-



     It has been shown in previous tests that with the low loading and variable



flow completely nitrified effluents could be expected from the first stage unit.



For this reason few samples of  the effluent were taken and analysed for



nitrates.  It was estimated that 19.5-20.0 mg/1 nitrate-N was  available  consist-



ently from the conventional activated sludge plant.



     Reasonably good denitrification was achieved in Test 25a  as shown in



Table 5.  Data are shown in Table  5 for the entire test period and also  for  one



day when a complete effluent  analysis was  obtained.  The high  ammonia and



organic nitrogen contents are due  to a combination of a proportionately  high



effluent solids concentration and  the fact  that milk solids were being used




for the carbon source.



     In  Test  25b the reduction  of  milk  solids  and the partial  use of methanol



lowered  the ammonia  in tiio denitrified effluent.  Rates of denitrification and




ratios of  BOD-/N are  shown in Table 6.
                                   - 33 -

-------
     Test 25c was conducted using only methanol as the carbon source to the




denitrification unit and the data are shown both for the entire test period




and on one day, September 5, when a complete effluent analysis was obtained.




Complete denitrification was obtained but again the total effluent nitrogen




was high due to the organic nitrogen content of the effluent suspended solids.




The turbidity of the effluent seems to be a disadvantage of this particular




process.  Although not evident from the data tables the units were operated




through September 2k- while recording only a limited amount of data.  It was




shown, however, that complete denitrification was obtained with mixed liquor




solids concentrations as low as 350 mg/1.




18.  Tests 26a and 26b



     These tests were very similar to Test 25 except  that for Test 26b the




temperature was reduced from 20C to 15C.  As  shown  in Table 3 the  standard




milk solution was used as the input to the nitrification unit while  methanol




was used as the carbon source for denitrification.  Low load ratios  were




used for both  stages as shov/n in Table 4  and complete nitrification  was obtained




in both tests.  Variable flow was used as with  Test 25-



     Excellent denitrification was  obtained in  both tests  and the  ammonia




nitrogen concentrations were slightly  over  1.0  mg/1.   Effluent  suspended




solids  from  the denitrification  units were  less than  20 mg/1  and  although no




organic nitrogens were determined  the  concentrations  very  likely  were  less than




2 mg/1.  Insofar as  denitrification is concerned conplete  denitrification was




obtained at  the  temperature of  15C.   Unfortunately  too high  a  ratio of BOD/H




was  used  to  consider defining  any  optimum conditions.




19.   Tests 2?a,  2?b,  2?c  and 2?d



      These four  tests were two stage operations with  nitrification followed by




denitrification.   Test 2?a was conducted .-it 20C but  the  others were at  10 C.




All were conducted with variable flow  as described previously.   The main

-------
differences between Tests 2?b, 2?c and 2?d were in the rates of flow.

Sludge bulking encountered in the nitrification unit required lowering the

flow rates to somewhat unrealistic levels to provide very long detention times

as shown in Table if, particularly for Test 2?c.

     The data presented in Table 5 shows that reasonably complete nitrification

was obtained from each of the first stage units, and the ammonia concentrations

were generally less than 1.0 mg/1.  Although the nitrate concentrations were

lower than in previous tests there was no corresponding increase in  the ammonia.

The lower nitrate levels were probably due to decreases in  the endogenous

metabolism at lower temperatures resulting in less release  of nitrogen to the

solution to be converted to nitrates.

     Denitrification was essentially  complete in all  tests  and again the ammonia

concentrations were usually less  than 1.0 mg/1.  As shown in Table  6, the BOD/R

ratios  were too  high and undoubtedly  unoxidized methanol was leaving in  the

effluent.  It was demonstrated  previously  that  methanol may be used much more

efficiently than used  in  these  tests.

20.   Tests 28a and  28b

      In view  of  the sludge bulking problems encountered in operating a small

nitrification unit  in series  with the cienitrLfication tank it was decided to

 use effluent  from the  larger  "pilot plant" as the  source of nitrates.  Although

 a solution of sodium nitrate  could have been used it  was considered a bit more

 realistic to have an actual effluent.  These tests were conducted at constant

 flow and at 10C using methanol as the carbon source.

      It is evident from the data in Tables 5 and 6 that satisfactory denitrifica-

 tion was obtained in 3 hours or less.  In Test 28a a rather high BOD/N ratio

 was used compared to that used in Test 28b.  A significantly low BOD/N ratio of
                                                                      /j\
 2.58 was used in Test 28b while the corresponding ratio used by Barth  ; was

 3.3.   Since the work was not confirmed in further tests it  is not certain that
                                    -  35 -

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this low ratio is a completely reliable figure.  If it does prove reliable it is



even more significant because it was obtained at a temperature of 10 C.



21.  Discussion of Reactor Test Results



     a. Nitrification



     Although the investigation of nitrification was not the primary goal of the



research some conclusions may be made from the data obtained.  The requirements



established previously by Downing, Painter, and Knowles     and Johnson and


          (2)
Schroepferv ' for obtaining nitrification in the activated sludge process were



found to be sufficient.  It was observed in two tests that continuous nitrifica-



tion was maintained at 10 C when the aeration tanks were operated at retention



times of 7.3 hours and loading rates (BOD/MLVSS) of 0.21+ -0.32.  With aeration



tank holding times of 70-75 hours there was little difference in the degree



of nitrification whether the flow was held at a constant rate or varied over



a 24-hour period.  When chlorine was added in an attempt to control the



settleability of the sludge the effect was that settleability improved after



about 10 days and nitrification ceased for about 20 days.  Apparently the



nitrifying bacteria were not completely destroyed since the nitrate concentra-



tion showed an increase after 20 days.



     b. Denitrification



     An aerobic activated sludge was found to require at least 2 days to adapt



to anaerobic conditions and be capable of reducing nitrates at a reasonably



high rate.  Reactor detention times as low as 2.5 hours accomplished rapid



denitrification providing sufficient mixed liquor solids were present.  The



rate and extent of denitrification was found to be a function of both the



BOD/MLVSS ratio and the BOD/H ratio.  A BOD/MLVSS ratio as high as 1.0 was



used and the optimum BOD/N ratio was found to be 34-  Figure 10 has been



prepared from the data in Table 6 to show the relationship between the 30D/.ILVSS

-------

-------
ratio (F) and the rate of nitrate reduction (R).  Lines of regression have



been computed  for the data as follows:



       Substrate used       Equation        Correlation coefficient



       Milk solids      R = 7.98F + 0.13             0.9%




       Methanol         R = 7.35F + 0.91             0.043




The circled data points were not considered in the computations since it was



known that in these tests excessive amounts of substrate were used and



conditions were not representative of equilibrium considerations.  For both



substrates the data clearly show a linear relationship between the organic



loading rate and the rate of nitrate reduction.  This relationship shows that



there is a constant ratio between the carbon source used for denitrification



and the nitrogen lost by denitrification.  The mean BOD/N ratio from Table 6



for the milk solids data is 3.85 and for the methanol data is 386.  It is only



coincidental that these ratios are almost identical.  These ratios should not be



taken as absolute equilibrium ratios but only as the approximate BOD/N require-


                                            (7)
ments.  The work by Barth and his co-workers    reported a ratio of 33 for a



methanol system and unaer the most ideal conditions the optimum ratio nay be



found to be less than this value.  When using milk solids it was found that



operation at close to the optimum ratio of 34 produced an effluent nitrate-N



concentration of 0.6 mg/1 whereas in a parallel test using a ratio of 40 the



nitrate-N effluent concentration was depressed 0.2 mg/1.  These results indicate



that the higher ratios may produce effluents with slightly lov/er nitrate



concentrations.



     Although the effluent 33 concentrations were generally quite high it is



believed that this was a hydraulic problem which could be solved in a larger



scale operation.  The process was shown to be capable of producing low effluent



BOD concentrations and the effluent ammonia nitrogen concentrations were shown
                               -37-

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to be a direct consequence of the nitrogen in the carbon source added directly




to the denitrification reactor.  The process did not seem to be greatly




affected by temperature since denitrification was achieved in 2.6 hours at




irr
I u \j.




     c.  Pour Stage Operation




     It was shown that a four stage operation was feasible,  The first two




stages reduced the nitrogen by 67 per cent while the overall removal through




the four stages was 86 per cent.  Phosphorus removal through the units was




quite snail.



22.  Analyses of Process Over 21+ -Hour Period




     a. Sampling



     During Test 20 on February 19 and March 18 effluent samples were taken




every two hours.  Likewise for Test 22Ab on March 18, effluent samples v/ere




again taken every two hours.  The results of these  tests are presented in Tables




8, 9 and 10 and in Figures 7, 8 and 9-  The rate of flow cycle is shown




graphically in the figures.  The concentrations of  solids  in the synthetic




waste water was constant throughout the flow cycle.




     b. Discussion




         (1) Nitrification



             All samples taken during Test 20 were  from a  nitrification process,




and because there is a limited amount of data no conclusive observations may be




made.  However the data do indicate some possible trends.




     The variation in pH shown in Figure 7 shows two definite periods of differ-




 ences.  Very likely at the low flow condition   (and low load condition) there




 is both less CO  production  and higher ratios of air flow/waste  flow to cause




 a greater removal of CO. and cause a rise in pH.



     Suspended solids concentrations on both days seemed to correspond directly




with the flow rates as might be expected.  There appeared  to be  more of a
                                 - 38 -

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              TABLE 8
teat 20 - NITRIFICATION - Feb. 19, 1968
     HOURLY VARIABLE FLOW DATA
Time
8:00
10:00
12:00
2:00
U:00
6:00
8:00
10:00
12:00
2:00
h:00
6:00
8:00
Flow
Rate
ml/min
18.1
19.3
18.6
16.0
13.0
8.6
6.2
6.2
5.3
5.6
7.5
11.8
16.0
Effluent Concentrations, mg/1
7.60
7.65
7.65
7.62
7.72
7.67
7.62
7.91
7.87
7.88
7.93
7.62
7.65
ss
53
68
68
76
2U
28
U
11
13
23
29
17
28
TP
2.9
2.5
2.2
2.5
1.8
1.9
2.2
2.0
.7
2J*
2.6
2.1*
2.3
COD
9U
79
65
65
60
U5
79
25
0
25
55
25
35
TKN
5.6
3.9
7.8
2.8

U.8
1*.2
3.1
2.8
U.5
8.1
3.2
3.8
NH3-N
1.9
0.7
0.6
0.6
0.8
0.7
0.8
0.5
0.6
0.6
0.7
0.7
0.8
N02-N N03-N
22.3
20.8
19.5
20.2
17.3
18.3
19.0
19.3
22.0
20.5
22.0
21.5
20.5

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              TABLE  9
Test 20 - NITRIFICATION - Mar. 18, 1968
     HOURLY VARIABLE FLOW DATA
Time
MMIM^^^HBIIHH-
fctOO
8:00
10:00
12:00
2:00
lj:00
6:00
8:00
10:00
12:00
2:00
1:00
Flow
Rate
ml/min
18.3
23.5
22.0
21.0
19.2
15.5
10.9
7Ji
7.9
60-
9.2
1U.U
Effluent Concentrations
pH SS
7.6 22
7.5 18
7.6 23
7.6 21
7.6 18
2U
12
13
12
12
12
22
TP
2.5
2.0
1.5
i.l
1.0
0.9
1.1
1.2
1.U
1.7
1.9
2.8
COD
30
39
39
32
32
32
20
20
17
17
2U
30
TKN
3.8
2.9
2.8
3.5
2.2
2.2
1.8
2.0
1.5
1.8
1.6
1.7
NH3-N
0.8
0.7
0.6
o.5
o.5
0.8
O.U
0.6
o.U
O.U
o.u
0.9
> mg/1
NO -N
o.ou
0.07
0.06
0.05
0.05
o.ou
o.ou
O.OU
0.05
o.ou
0.05
o.oU

NO -N
2U.8
2U.3
23.0
21.3
21.3
21.7
17.7
21.5
22.0
21.8
2U.8
25.5

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                TABLE 10



Test 22 Ab - BENITRIFICATION - Mar. 18, 1968



       HOURLY VARIABLE FLOW DATA

Time
boo
6:00
8:00
10:00
12:00
2:00
li:00
6:00
8:00
10:00
12:00
2:00
Flow
Rate
ml /tain
lli.O
17.3
20.6
22.8
23.0
22.0
19 Ji
15.7
12.3
8J
9.1
8.9
Effluent Concentrations, mg/1
_H_
7.7
7.5
7.U
7.6
7.5
7.U
7.5
7.9
7.6
7.6
7.7
7.6
ss

Ill
10
12
8
13
1U
15
18
20
Hi
16
TP
0.8
0.8
1.0
0.7
0.6
0.6
0.7
0.8
0.9
1.0
1.1
1.1
COD
20

17
22
20
20
27
3U
32
32
3U
37
TO
6.3
2.6
U.2
3.9
U.1
li.l
3.7
U.2
U.U
U.8
5.3
U.9
NH3-N
U.6
3.9
3.9
3.7
3.2
3.3
3.2
3.6
3Ji
U.o
U.6
U.7
N02-N
0.03
T
O.OU
o.ou
O.OU
0.03
0.03
0.03
o.ou
0.06
0.06
0.05
N03-N
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1

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FIGURE  7

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cyclic variation in  total phosphorus  on March  18  than on February 17 but never-




theless somewhat the same pattern existed  on both days.  With higher growth




rates during high-flow periods  the uptake  of phosphorus by the sludge was




likely to be greater and thereby diminish  effluent concentrations as shovm.




Although these values were for  total  phosphorus the values for soluble




phosphorus showed a  similar pattern.




     The COD showed  somewhat similar  variations on both days with one period




of minimum concentration and one of maximum concentration.  The data shown are




for total COD including S3 but  soluble COD concentrations were also determined




and showed a similar variation.  There appears to be a direct correlation of



COD with flow rate.




     Nitrogen variations are also shown and the TKN values are for total




nitrogen including that in the  33.  The TKH values showed a slight correlation




with the 33 concentrations as might be expected,  and the remaining soluble




fractions were so low that they were  of little concern.  Ammonia concentrations




were for the most part less than 1.0  ng/1  and  showed no apparent change with




the flow rate.  The fact that the ammonia  concentrations were reasonably




constant is significant when observing the nitrate variations.  The niirate




concentrations showed a cyclic pattern similar to the flow rate.  The minimum




nitrate concentration occurred approximately 6 hours following the maximum




flow, and the maximum nitrate concentration occurred i+-6 hours following the




minimum flow rate.  However, the total effluent nitrate variation may not be




significant since it was only 17-22 m~/l and 18/25 mg/1.  Despite the variation




in nitrates there was not a corresponding variation in am.ionia and from this it




is indicated that the variation of sludge growth  rate with load results  in




greater net nitrogen uptakes during these periods.  The consequence of this




is that less ammonia remains to be oxidized and consequently the actual




nitrate concentrations become less for a period following a high flow (or load).
                               - 39 -

-------
     (2) .Denitrification
          The data obtained during Test 22Ab was fron a denitrification test.
It is noted from Table 6 that the BOD/N ratio was reasonably low and
consequently the effluent BOD or COD should be quite low.
     The changes in pH over the 24-hour period are hardly worth noting although
the slightly higher values during the  low flow period may be due to the lower
rate of production of C0_ and higher ratios of mixing gas/waste flow.  The
S3, TP and COD changes were essentially directly correlated with one another.
Since the TP and COD values included the 33 one would expect this sort of
pattern.  Changes in the soluble fraction were, however, not evident.  Although
effluent S3 should normally vary directly with the flow rate,  the ..laximum
concentrations were found with  lower flows.   The total variation in 33
concentration, however, was only from  8  to  20 mg/1.  With a reasonable allowance
for the COD of the effluent S3  it is evident  that  the soluble  COD in the
effluent would be in the range  of only 10-30  mg/1.
     The milk solids and sodium nitrate  used  as  the  influent to the process
contributed the following concentrations  of nitrogen and phosphorus.
                                                 P,  mz/l        N, ng/1

                Milk solids:
                         TP  -                      1.8
                         TKN -                                     7.0
                3odiuia Nitrate:                                  2\ .2

                Total                             1.8             28.2

With some  allowance  for the uptake  of N and P in the sludge  it is  evident  that
the remaining quantities of N and P from the  milk solids are  found in  the
effluent.  Essentially all  of the nitrate nitrogen was  lost  due  to  denitrification
and the overall removal was approximately 85 per cent.
                                  -40 -

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     The amiaonia-N concentrations shown in Table  10  indicate a greater uptake




of nitrogen during the period of high flow (high  organic load).  The variation




is small but consistent and is likely due to  higher  net growth during the high




load periods.  The fact that the effluent nitrogen concentration variations are




small is a favourable output characteristic,  and  the low nitrate concentration




is attributed to the use of a BOD/N ratio of  the  proper order of magnitude and




maintaining the same ratio throughout the flow  cycle.

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                        VI. DEMONSTRATION PLANT T5STS



A*     Test Program




       With the background gained  from the reactor  tests using synthetic



feed solutions, it was decided  to  test the process  using a municipal



wastewater.  The significance of using a  municipal  waste is not only



that the composition differs from  that of the  synthetic waste, but there



also is an inherent time variation in concentration associated with it.



However, to completely simulate flow  in a small demonstration plant with



that of a municipal plant, it is necessary to  provide some means of



continuously varying the rate of flow.



       A demonstration  plant was  constructed and  located at LELnneapolis-



St.Paul Sanitary District (MSSD) Wastewater  Treatment Plant, and primary



effluent was used as the wastewater feed.  The device developed for the



variable flow reactor tests was used  to provide a continuously varying



rate of flow to the demonstration  plant.



       The objectives of the test  program were to determine whether or not



a municipal wastewater could be treated for  nitrogen removal using



processes and procedures similar to those defined in the reactor tests.



As such, the basic flow diagrams shown in Figure 3  were used where the



conventional activated sludge process was used for  nitrification.



Denitrification was achieved with  a mixed anaerobic reaction tank followed



by a settling tank with sludge  recycle to the  mixed tank.  Primary effluent



was used as the carbon source and  was fed to the denitrification unit together



with the nitrified effluent from the  nitrification  unit.



       Tests were conducted at  both constant and variable rates of flow.



Temperature variations were encountered as the seasonal variations in the



raw wastewater teciperature were experienced.
                                  - 42 -

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B.     Equipment




       1 .  General




       The demonstration plant was located in the aeration gallery of the



MSSD Treatment Plant.  It was fortunate  to obtain this location because



of the protection of the plant from  the  weather and the availability of



electrical power, compressed air, sampling facilities, and the primary



effluent feed for the demonstration  plant.  The plant v/as designed for



a nominal average flow of (l) one gallon per minute.



       Immediately adjacent to the gallery was a channel with primary



effluent, and fortunately there were valved pipes through the wall to



supply the demonstration plant with  a raw feed.




       2.  Reaction Tanks



       The reaction tanks consisted  of seven (?) 2I-0" diameter tanks and



two (2) 3I-0" diameter tanks.  Each  tank was 6l-6" high and constructed



of 16 gauge galvanized steel.  A typical tank is shown in Figure 11.  The



2'-0" diameter units had hopper bottoms  with 60  slopes while the 3'-0"




diameter units had bottom cones with 45  slopes.
            tank could be used either as  an aeration tank or settling tank.




When used as an aeration tank air was added to  the  tank at the bottom of



the cone and diffused through a  layer of  wire and saran fabric placed



between the two flanges located  approximately 6 inches above the cone



bottom.  The fabric and wire were removed when  the  tank was to be used as a




settling tank and the sludge was removed  at the cone bottom.



       Portholes were constructed as  shown in four  of the 2'-0" diameter




tanks in order to observe the sludge  mixing and sludge levels in the



tanks.  The port-holes were covered with  plexiglas  and served their purpose



well.  It would have been advantageous  to have  port-holes on all of the tanks.
                                 - 43 -

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PORT-
HOLES'
                   VS
    TANK-ELEVKTICN
                         TANK PLAN\ PORT-HOLE DETAIL
 DEMONSTRATION PLANT TANKS- CONSTRUCT/ON  DETAILS
                                          FIGURE  //

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       It was originally intended to interconnect the tanks with 1"




diameter vinyl tubing.  It was later found that air binding was occuring




in these lines and by switching to 1-jH1 diameter tubing most of these




operational problems were avoided.



       For denitrification the reaction tank required mixing without aeration.




Initially the reaction and settling tanks ware covered and sealed in order



to recirculate gases for mixing as done in the reactor tests.  For a number



of reasons this method of mixing was impracticable and straight mixing



with a propellor-type unit was used.  Despite the air-liquid interface and




the need for anaerobiosis, there was no apparent evidence that excessive




amounts of ocygen were being transferred across the interface.



       The tank assemblies and individual tanks are shown in photographs




as Figures 12, 13, and 14.



       3.  Air Supply



       The air was supplied from the MSSD plant and furnished to the




individual tanks through a series of valves as shown in the photograph,



Figure 15.  As shown in the photograph, four air lines were available for




the tanks and each supply was metered through the one rota-meter.




       4.  Pumps and Feed Apparatus



       All pumps were Sigmamotor pumps with the exception of one Moyno



pump.  The Moyno pump was equipped with a U.S. IJotor Vari-Drive but



operated at a constant rate of flow on the return sludge line for the




initial nitrification process.



       The Sigmamotor pumps were equipped with Zero-Max speed reducers.



All of the Sigmamotor pumps were Model T-6 units except for the raw feed




pump to the first nitrification unit which was a Model T-4   The T-4



unit was also equipped with an actuating lever to provide a continuously
                                 -  44 -

-------
>M0KSTf?ATt0N PLANT ASSEMBLY
                                        FtGUKE
. PLANT:
              . TANKS. P^.

-------
PLANT :  DENITRIFICAT/ON TANKS * SIPHON BARREL .  FIGURE.  /4
   PLhNT:  AIR METERING BOARD.
FIGURE,  75"

-------
varying x&te of flow.  Typical pomp installations are shown on Figures 12,




13 and 14,  and the T-4 Sigmamotor pump with the variable flow equipment




is shown as KLgure 16.



       Because there was a delay in obtaining the large feed pump the




initial method of supplying primary effluent was through the use of an




orifice.  The orifice was at the bottom of a plexiglas tube with an



inner tube used as an overflow.  The inner tube was adjustable in height




to provide a means of adjusting the rate of flow.  This system was only



temporarily used and was undesirable because of the tendency to clog.




       5.  Deaeration Tank



       With the release of nitrogen gas as one of the end products of




denitrification, some problems were encountered with gas-lifting in



the final settling tank.  To alleviate this condition a degasification



tank was constructed based on some aeration tests followed by settling.



It was concluded that a 4" diameter tank giving a nominal aeration period




of two minutes would be very adequate and hopefully would not add a great




deal  of dissolved oxygen.  The  tank as constructed was as shown in the



photograph, Figure 17, in the center  of the picture.  Air was introduced




at the bottom and the  flow was  from left to right.




       6.   How Metering



       Instantaneous rates of flow were measured volumetrically using a




large flask.  The raw waste  feed lines and return sludge lines were all




equipped to permit measurment in this way at  any time.  A record  of total



plant flow  was obtained by using a siphon barrel at  the  outlet end of the




 system.  The  final effluent  drained  into a  55 gallon drum equipped with a




 siphon which  would discharge when filled to approximately the  45  gallon



 level.  3y  using a level recorder in  the tank,  each  filling of the barrel
                                      -  45  -

-------
DEM.  PLANT: PRIMARY
                    PUMP.    FIGURE
PLAN'*'; DEt\E RAT'ON  r/4/.X.    FIGURE   /7

-------
nas noted by a high point on the recorder chart.  The number and spacing



of the points on the recorder chart was used as a record of the rate



of flow through the plant.  The equipment is shown in the photograph,




Figure 14.



       This effluent barrel also served as a means of providing a signal



for the samplers to operate.  Whenever the barrel was full a float switch



operated to actuate the composite samplers.



       7.  Sludge Wasting



       Sludge wasting from the nitrification process was accomplished by



wasting mixed liquor as suggested by Garrett^1    .   A flexible hose was



connected to the aeration tank and a rubber section of the hose was flattened



against a base board by a spring loaded bar.   The bar was connected to two



solenoid switches which periodically lifted the  bar to open the hose and



thereby waste mixed liquor.  A five-minute timer was used such tliat sludge



was wasted every five minutes and for any fraction thereof.  By adjusting



the time interval it was possible to maintain a  reasonably constant mixed



liquor solids concentration.



       8.  Sampling



       Sampling was usually accomplished through the use of automatic



samplers.  All samplers used were as manufactured by Sonford Products



Corporation of Minneapolis.



       The effluents from the nitrification and  denitrification plants



were  sampled using the Model HG-2 samplers and the primary effluent



was sampled with a Model TC-2 which was already  in place as part of the MSSD



equipment.  The samples taken with these samplers were composite samples and



operated on a signal from a float switch in the  effluent barrel.



       On several occasions samples ware taken hourly by use of Model NW-2




samplers from the Sonford Products Corporation.






                                 - 46 -

-------
C.     Procedures



       The demonstration plant was operated by personnel from the



University of Minnesota except for some equipment maintenance work and



general observations.   Bnployees of the MSSD on duty in the location



of the demonstration plant were very helpful in notifying the



investigators  of unusual operating conditions.  The analytical laboratory



at the MSSD did provide help in running some BOD's, but for the most part



the analytical work was conducted in the Sanitary Ehgineerinc Laboratories at



the University of Minnesota.



       The demonstration plant was visited at least once each day and



sometimes as often as three times during a 24-hour period.  These visits



were for performing routine preventive maintenance, taking samples, adjusting



operating conditions, and solving many unpredicted problems.  Mechanical



problems included*  clogged tubing due to solids or air binding? broken



tubes; pump and motor failure} samplers inoperative; frozen feed lines; and



power failure.  Operational problems included* rising sludge in settling



tanks; bulking sludge; and necessary shut-downs due to curtailing of



MSSD operations.   In explanation of the latter, it was necessary to curtail



the MSSD operations due to mechanical equipment failure and due to high



water conditions in the receiving river.  At one period the entire plant



was shut down because of the danger of flooding.



       The consequences of these mechanical and operational problems are



somewhat obvious.  Flow interruption of any sort cause upsets of



equilibrium situations, and the occasional loss of activated sludge solids



resulted in having to repeat certain test operations.
                                  - 47 -

-------
       Because of the many interruptions of the  operations the data have



been analyzed for the periods  shown  in Bible  11  during which times it



was considered that valid  data were  obtained.  It  is also noted in the



table whether or  not the primary  feed rate was constant or variable.



Also shown are the days on which  hourly samples  were taken.



D.     Experimental Results  of Demonstration  Plant Tests



       1.  General Test Conditions



       Data from  the demonstration plant tests were analyzed for test



periods shown in  Table 11.  Because  of the operational problems encountered



all of the data obtained were  not sufficient  for analysis.  In Table 11



the test number desigration  is shown,  each test  is shown to have been



operated with constant or  variable flow, and  data  are shown when hourly



samples were taken over 24-hour periods.



       The operational data  are presented in  Table 12 where mean, maximum



and minimum values are given.  Flow  is given  in  milliliters per minute



(ml/min).  Observations of concentrations in  the mixed liquor in milligrams



per litre (mg/l)  are given as  dissolved oxygen (DO), suspended solids (SS),



and volatile suspended solids  (VSS).   Air used is  expressed in cubic feet



per minute (cfm),  and detention times (DT) are given in hours (hrs).  The



organic load to the reactors is expressed as ratios of pounds of 5-day



20 C BOD per day  per pound of  mixed  liquor volatile suspended solids



under aeration (BOD/ilLVSS),  and as the weight of BOD per day per pound



of mixed liquor suspended  solids  otherwise known as sludge age (SA).



The sludge volume  index is given  (SVl)  together with the percent that the



rate of flow of return sludge  is  of  the raw flow.  Settling tank characteristics



are given in terms of detention time  (DT) in hours (hrs) and surface settling



rates (SSR) as gallons per day per square foot (gpd/sf).
                                  - 48  -

-------
Table 11  Listing of Demonstration Plant Test Periods
Constant(c) ^^ f
-------
                                  Table 12
                    DEMONSTRATION PUNT OPERATIONAL DATA
                                 Reactor
                Flow    Mixed Liquor  Air   DT
                                                    BOD
                                                     Ret
                                                      SI  DT
                                                    Sed Tank
                                                         SSR
               ml/min  DO   SS   VSS    cfro   hrs  MLVSS  SA   SVI  J
1. Nov. 1 - 7fl766 - u
II: No. of Obs.   7     16   6     6      7      7     7     7     6    7
                                                          hrs  gpd/sf
   Mean
   Min.
   Kax.
2629
21*00
2750
                                                   7     7
    1*703  359U  2.21  11.5  0.11  U*.3  52   53   2.2   318
0.6 1*200  3310        11.0  0.08  11.0  1*6   52   2.1
6.3 5350  U28U
12.6  0.13  13.9  6?   62
      290
2.1   33?
 Di No. of Obs.   6     3    5     5
   Mean         708   0.8  130U   913
   Min.         600   0.5   600   292
   Max.         950   1.2  2100  11*78
                               655
                               1.7  0.56   2.8
                               1.6  0.30   1.9
                               1.8  1.1*6   li.8
                                             666
                                             12   1.7   1*08
                                             10   1.6   387
                                             15   1.8   1*1*2
 11 No. of Obs.   6
   Mean        3337
   Min.        3200
   Max         3650
I. Nov. 9-lu, 1968 - C
H: No. of Obs.   6     20   U     h     5     6     1*     U    h    6     6     6
   Mean        2625   3.0  U877  3U76  2.U  11.6  0.13  13 .U  69   58   2.2   317
   Min.        2500   0.7  1O20  2988        10.8  0.11   8.2  63   50   2.1   302
   Max.        2800   U.9  5U70  3906        12.1  0.17  13.5  77   71   2.3   339
 Di No. of Obs.   6     k    3     3
   Mean         89   0.2  1980  1387
   Min.         7hO   0.1  11:50  1022
   Max.
                               6     3     3
                               1.7  0.60   2.6
                               1.6  O.l   1.9
                               1.7  0.80   3.6
                                             lj     6     6
                                            19.5  1.7   k25
                                            13.0  1.6   1*06
                                            28.14  1.7
 Tt No. of Obs.
   Mean        3515
   Min.        3360
   Max.        3610

-------
                                  Table  12
                   DEMONSTRATION  PLANT  OPERATIONAL DATA
                                 Reactor
               Flow   Mixed Liquor  Air  DT                   Ret    Sed Tank
                           Eig/j                   BOD              51  DT     SSR
               ml/min DO  SS  VSS  cfm  hrs  MLVSS  SA   SVI   3   hrs  gpd/af
I. Nov.17-21.1968 - C
HJ No.  of Obs.  U     20    33     5     ^     3     33     3   U     U
   Mean       2700   1.8  5UU2   3968   2.18  11.3  O.n  12.2  91   66  2.1   327
   Min.       2UOO   0.6  5360   39UO        10.1  0.10  11.0  82   61  1.9   290
   Max.       3000   2.6  5U50   U02U        12.6  0.13  Ui.5 103   7U  2.h   363
Dt No. of Obs.  h      333           U     3     3
   Mean         762    OJi  1169   836        1.7  0.72   2.1
   Min.         720    0.2   036   368        1.5  O.lt2   1.1
   Max.         800    0.6  1882  1350        1.8  1.23   3.3
 Ti No. of Obs.
   Mean
   Min.        3150
   Max         3800
It. WOT. 22- Dec. 1. 1968  - V
 It No. of Obs.   h    12    U     3     U     U     12     U    1    U     U
   Mean        2575  2.3  Ui21  3251  2.39   11.9  0.10  10.8   10U   76  2.3   312
   Min.        2100  OJ,  U07U  3000         10.1         9.2   86      2.1   25U
   Max.        2800  U.O  U598  3390         Ui.li        13.1   118      2.8   339
 D: No. of Obs.   5     2    2     2           3      22
   Mean         680  0.7   910   61*3          1.9  1.1    1.7
   Min.         6$  -5   5Hi   36U          1.7  0.6    0.9
                720  1.0  1306   922          2.1  1.5    2.U
 Ti No. of Obs.   3
   Mean        3255
   Min.        2750
   Max.        3U20

-------
                                  Table 12
                    DEMONSTRATION PUNT OPERATIONAL DATA
                                 Reactor
                Flow    Mixed Liquor   Air   DT
                                                   BOD
                                                              SVI
              ml/min  DO   SS   VSS    cfra   hrs  MLVSS  _SA	
. Dec. 6-ll,196  - V                               
           7~ 2     93     33     2     2     232
                                                                   Ret    Sed Tank
                                                                    SI  DT     SSR
                                                                    %   hrs  gpd/sf
H: MO. 01
  Mean
  Min.
  Max.
               2663   3.8  UW7  318?  2.23  ll.li  0-16  8.7   HI   65
 ?     2
2.2   322
               2600   3.^  M38  28714
               2725   U.7  1*706  3166
                                            11.1  0.15  8.5   89   60   2.1   311*
                                            11.6  0.17  9.2  133   70   2.2   329
D: No. of Obs.   3     3    3     3
   Mean         7UO   0.2  169k  1188
   Min.         700   0.1  101*0   690
   Max.         800   0.3  2050
                                             2     2     2
                                             1.8  OJ*7  3.2
                                             1.8  0.37  2.8
                                             1.8  0.52  3.8
                                                                   2     2
                                                                   29   1.8
                                                                   2h   1.8
                                                                   33   1.8
       2
      101
      399
TI No. of Obs.   2
   Mean        3300
   Min.        3275
   Max         3325
6. Dec. 12-18.  1968  -  V
H: No. of Obs.   1     93     2     2     1     1     131
   Mean        ?500   ?.5  Wt?6  3^25  2.18  12.1  0.12  11.5 137   56
   Min.               C.9  h!38  3328                         112
   Max.               U.3  ii70U  3522                         16U
                                                                         1
                                                                        2.3
                                                                               1
                                                                              302
 D: No. of Obs.   3     1    2     2
   Mean         706   0.2  1909  1397
   Min.         700        1908  1216
   Max.         720        1910  1576
                                             111
                                            1.8   0.145=  3.5
                                                                   1     1
                                                                   22   1.8
       1
      387
 T: No. of Obs.   1
   Mean        3206
   Min.
   Max.

-------
                                 Table  12
                   DEMONSTRATION PLANT OPERATIONAL DATA
                                Reactor
               Flow
        Mixed Liquor   Air
            rag/1
DT
                                                  BOD
              ml/min  DO   SS   VSS   cfia   brs  MLVSS j>A
^rc^'oby?71'^11*9 rw
                                           Ret    Sed Tank
                                            SI  DT     SSR
                                      SVI   %   hrs  gpd/sf
   Mean
   Min.
   Max.
             2     12     2     1    221     2     2
3035   U.9  370U   3122  2.35  10.0  0.12   9.0  130   52   1.9   367
2970   U.2  32UU
3100   It .3  U16U
 9.8
10.2
                                 6.9
                                11 .h  Hi9
1.9
1.9
359
375
 D No. of Obs.    2221
   Mean         67$   0.3  2 71*7  2396
                650   0.3  22514
                700   0.3
                              212
                              1.6  0.16  6.2
                              1.5        U.5
                              1.6
                       12
                       U3   1.6
                           1.5   1438
                           1.6   U60
   No. of Obs.    2
   Mean        3710
   Min.        3620
   Max         3800
6. Jan.  6 - 9, 1969   V
8
 N: No. of Obs.    I
   Mean        2955
   Min.        2900   2.0  396U
   Max.        3000   5.9  UU61*
                              U
                             10.2
                             10.1
                             10 Ji
             2    2    1     h     h
            8.1  136   51   2.0   358
            7.9  121        1.9   351
            8.3  151        2.0   359
 DJ Ho. of Obs.    322
   Mean         657   0.1  33U6
   Min.         630   0.1  2816
   Max.         690   0.1  3876
                              3
                              1.8
                              1.6
                              2.3
             1
            lj.7
                                           133
                                           1*2   1.8   399
                                                1.6   312
                                                2.3   1*U6
 Ti No. of Obs.    3
   Mean        3612
   Min.        2580
   Max.        3690

-------
              Table  12
DEMONSTRATION PUNT OPERATIONAL DATA
Reactor
Flow Mixed Liquor
9. Jan. 10-19, 19<
N: No. of Obs.
Mean
Min.
Max.
Dt No. of Obs.
Mean
Min.
Max.
Tl No. of Obs.
Mean
Min.
Max
ID. Jan. 20-29,
N: No. of Obs.
Mean
Min.
Max.
D: No. of Obs.
Mean
Min.
Max.
Tt No. of Obs.
Mean
Min.
Max.
ral/min DO
>>  v
10
2870
2600
2890
2
71*0
720
760
2
3610
3610
3610
1969  V
10 2
2813 1*.6
2600 3.8
2960 5.1*
6
1*00
330
1*60

3213
3060
3320
SS
1
1*396


3
2290
181*2
3181*




3
3172
3128
3200
1*
1880
161*1*
2186




VSS
1
3266


1
1388






3
271*1
2376
21*36
1*
1383
1208
1600




Air DT
BOD
cfm hrs MLVSS SA SVI
3112
10.5 0.12 11.0 171*
10.5 166
10.6 181
212
1.6 0.35 U.I
1.6 3.8
1.6 1*.!*




12223
2.55 10.9 0.20 6.6 165
10.2 0.19 6.2 160
11.6 0.21 7.7 169
1* 3 3
1.8 0.28 5.1
1.8 0.19 i*.2
1.9 0.32 6.9




Ret Sed Tank
SI DT
% hrs
2 3
52 2.2
1*6 2.0
57 2.5
1 2
36 1.6
1.6
1.6




2 2
61 2.1
57 2.0
65 2.2
1*
1.8
1.8
1.9




SSH
gpd/sf
3
31*7
31*5
31*9
2
1*37 -
1*37
1*37




2
336
311*
358
1*
389
370
1*01





-------
              Table  12
DEMONSTRATION PLANT OPERATIONAL DATA

Nt NO. Of ObS.
Mean
Min.
Max.
Di No. of Obs.
Mean
Min.
Max.
Ti No. of Obs.
Mean
Min.
Max
12. Mar. 19-26,
H: No. of Cos.
Mean
Min.
Max.
Di No. of Obs.
Mean
Min.
Max.
Ti No. of Obs.
Mean
Min.
Max.

Flow
ml/min
JxO7 flM^
15
1*100
1*000
1*200
9
376
300
1*20
9
1*1*76
1*385
1*620
1969 
6
31*67
3200
3800
6
563
365
880
6
3832
3600
1*21*5


Reactor
Mixed Liquor Air
Big A
DO
IT
U.9
3.0
6.7
7
0.2
0.1
0.3




C
12
I* .6
3.0
5.8
6
0.5
o.l
O.6




SS
10
2915
2531*
3U38
9
1256
816
2095




6
3507
3212
3862
6
2361
171*8
2952




VSS cfra
9 10
2063 3.10
1850
21*02
8
938
622
11*30




6 6
2378 2.lh
2171*
261*8
6
11*91*
111*8
1556





DT
hrs
10
7.1*
7.2
7.6
9
1.3
1.2
1.3




6
8.7
7.9
9.1*
6
1.5
1.1*
1.6





Ret
BOD SI
MLVSS SA SVI %
9 10 10 10
0.3U l*.l 200 51*
0.29 3.9 136 1*3
0.1*1 5.5 270 70
7 8 1
0.39 3.7 21
0.19 2.2
0.52 7.8




66 66
0.21 7.0 161* 101*
0.15 5.9 103 100
0.26 8.6 21*0 109
66 1
0.28 6vl 28
0.15 3.6
0.1*3 11-0




Sed Tank
DT
hrs
10
1.1
1.1*
1.1*
9
1.3
1.2
1.3




6
1.7
1.5
1.8
6
1.5
iJj
1.6




SSR
gpd/sf
10
1*98
1*81*
518
9
51*1
530
558




6
1*19
387
1*60
6
1*70
1*36
513





-------
              Table 12
DEMONSTRATION PLANT OPERATIONAL DATA
Reactor
13. Mar.27-29,
N: No. of Obs.
Mean
Min.
Max.
Dt No. of Obs.
Mean
Min.
Max.
fl No. of Obs.
Mean
Min.
Max
111. Mar.31-Apr.
R: No. of Obs.
Mean
Min.
Max.
D: No. of Obs.
Mean
Min.
Max.
T: No. of Obs.
Mean
Min.
Max.
Flow Mixed Liquor
ing /I
ml/min DO SS VSS

3611
3101* I* .6 3Ui8 2396
3060 2.1
3150 6.1*
3 111
556 0.6 3321* 2256
500
590
3
3660
3560
371*0
3, 1969  C
1* 12 1* 1*
3212 3.7 291*6 2011
2850 2.1* 2910 1982
3650 5.0 2982 2022
h 3 1* 1*
600 Oj* 21*1*8 16?2
1*90 0.1* 1988 1388
730 0.5 3081 2221*
1*
3812
3560
U160
Air DT
BOD
cfra hrs MLVSS SA
6 3.1 1
2.39 9.8 0.16 8.8
9.6
9.9
111
1.6 0.16 9.3
1.5
1.6




1* 1* 1* h
2.39 9.5 0.21* 5.5
8.3 0.22 5.1*
10.6 0.27 6.5
1* 1* 1*
1.5 0.28 5.5
1.1* 0.22 l*.l*
1.6 0.31* 6.1*
' '



Ret Sed Tank
SI DT
SVI % hrs
123
250 112 1.9
111 1.8
113 1.9
3
1.6
1.6
1.6




1* 1* 1*
: 263 116 1.8
221* 99 1.6
303 130 2.0
1*
1.5
1.U
1.6




SSR
gpd/sf
3
375
370
381
3
1*1*3
1*31
1*52




1*
388
31*5
11*1
1*
1*61
1*33
?<9





-------
              Table 12
DEMONSTRATION PUNT OPERATIONAL DATA



Flow


Reactor
Mixed Liquor Air DT
mg/1
ml/min DO
15. Apr.7-9,1969
U: NO. 01 UDS.
Mean


Dt



n



16.
1:



DJ



I:


Min.
Max.
No. of Obs.
Mean
Min.
Max.
No. of Obs.
Mean
Min.
Max
May 12 - 15,
No. of Obs.
Mean
Min.
Max.
No. of Obs.
Mean
Min.
Max.
No. of Obs.
Mean
Min.
Max.
 C
3
2933
2900
3000
3
583
550
620
3
3516
3180
3550
1969
U
3325
3250
3UOO
h
623
530
670
h
39U8
3910
8
fc.3
3*9
5.2
2
0.7
0.7
0.7




 C
12
5.3
2.5
7.9
3
OJi
0.3
0.5



ss
3
2628
2li06
2896
2
1921
1858
199L




h
5063
1863
5218
U
2352
2310




VSS cfm hrs
32 3
1790 2.3Ji 10.3
1658 10.1
1936 10 .I*
2 3
1289 1.7
1232 1.6
1336 1.7




h 3 U-
3372 2.20 9.1
3272 8.9
3li6ii 9.3
li h
1610 1.5
1578 1.U
1.5




BOD
MLVSS
3
0.2U
0.23
0.26
2
0.3k
0.30
0.38




li
0.15
0.11*
0.15
U
0.30
0.23
0.31




SA SVI
3 3
6.1 291
5.6 208
6.5 32li
2
U.5
li.c
5.c




U h
10.1 175
9.6 170
11.0 182
h
5.2
li.7
6.2



Ret Sed
Tank
SI DT SSH
% hrs gpd/sf
3 3
66 2.0
62 1.9
75 2.C
1 3
30 1.7
1.6
1.7




li I
78 1.7
7li 1.7
81 1.8
1 h
25 1.5
l.li
1.5



3
355
351
363
3
U26
U21
U30




li
ii02
393
U12
k
1*78
ii69
1*73




-------
              Table 12
DEMONSTRATION PLANT OPERATIONAL DATA
17.
N:


Dt



Ti



IB.
V:



0:



TJ



May 19-
no. or
Mean
Min.
Max.
No. of
Mean
Min.
Max.
No. of
Mean
Min.
Max
May 2?
No. of
Mean
Min.
Max.
No. of
Mean
Min.
Max.
No. of
Mean
Min.
Max.

Flow
ml/ndn
26,1969 
Obs* 8
3900
3760
a500
Obs. 7
750
690
800
Obs. 7
1638
Ui30
5290
- July 22,
Obs . 19
363U
3230
aiOO
Obs. a9
82U
310
9UO
Obs. U9
.aa62
3710
U890


Reactor
Mixed Liquor Air
CTgA
DO
%
3.0
0.6
a. 8
a
0.3
0.1
0.6




1968
2a
3.2
0.3
6.9
6
0.3
0.2
OJ




SS
6
a258
ai38
a556
5
1717
iaa2
2082




 V
33
a326
3388
a980
30
1715
378
2396




VSS cfm
6 6
2909 2.13
2812
3132
5
1176
1012
ia&




33 6
303U 2.75
237?
3568
30
1210
298
I63a





DT
BOD
hrs MLVSS SA
866
7.7 0.19 7.6
6.7 0.16 6.6
8.0 0.22 9.3
7 5 5
1.3 O.U7 3.3
1.1 0.30 2.5
1.3 o.5a a. 9




a9 31 32
8.3 0.17 8.5
7.7 O.lli 5.1
8.9 0.28 11.9
a9 29 29
1.3 0.53 2.9
0.32 0.6
2.11, a.7






Ret Sed Tank
SI DT
SVI % hrs
688
I8a 68 1.5
160 59 1.3
196 73 1.5
1 7
23 1.3
1.1
1.3




27 a3 a9
99 58 1.6
70 a3 1.5
131 72 1.7
16 19
23 1.3
11 1.2
31 i.a




SSR
gpd/sf
8
a?6
U55
5a5
7
561
536
6ao




a9
U39
U12
U96
a9
529
U90
6ao





-------
                                  Table 12
                    DEMONSTRATION PLANT OPERATIONAL DATA
                Flow    Mixed Liquor   Air   DT                    Ret    Sed Tank
                            msA                   BOD              SI  DT     S3R
               ml/min  DO   SS   VSS   cfm   hrs  MLVSS  SA   SVI   %   hrs  gpd/sf
15. Julfr 2U-Aug.21.1969  C
 N: N6. 61 UbS   9"6     21    21   5     29    32    21   20   26    29    29
                                 Reactor
   Mean        2950    3.8  h020  2796   2.30  8.7  0.18  7.8   97   59    2.0  357
   Min.       26UO     0.8  2192  1526        6Ji  0.12  U.5   61   27    1.5  315
   Max.       3980     6.3  5612  3896        9.8  0.32  11.9  l8-2  91    2.2  h9h
 D: No. of Obs.  29          21    21         29    21    21    8   28    29    29
   Mean        782          19l3  1386       1.6  0.65   ?-2  397  33    1.6  U52
   Min.        660           356   2Jh       1.2  0.31   0.3  106  11    1.2  391
   Max.       1080          35H  2h32       1.8  1.60   U.3  886  h9    1.8  615
 Ti No. of Obs.  29
   Mean       3732
   Min.       3250
   Max        5080
   July 2U-.Aug. 21,  1969  C
 H: No. of Obs.  29     T  20     20   h     29    20   20    19   29    29   29
   Mean       3732    U.U  2517  17U1   0.63  1.6  0.32  U.6   121  30    1.6
   Min.       3250    1.2   656   U68   0.50  1.2  0.10  1.3    h6  21    1.2  391
   Max.       5080    6.2  fc928  3330   0.81  1.8  1.06  9.6   320  fcO    1.8  615
 DJ No. of Obs.  29          21    21         29    21   21    16   29    29    29
   Mean        ?53         ?020  U05         1.5  0.25  5.8   318  25    1.5  1*82
   Min.        200          59li   100         1.1  0.11  1.2   179  19    1.1  U31
   Max.	370         liOSli  2802	1.7  1.38  13.9  785  28    1.7  659
 T: No. of Obs.  29
   Mean       3986
   Min.       3U50
   Max.       5ii50

-------
       Analytical data for the demonstration plant are presented in



Table  13 and includes mean, minimum, and maximum values.  Temperature



of the raw flow and mixed liquor are given in degrees centigrade and



effluent concentrations  in milligrams per litre (mg/l).  Concentrations




included total Kjeldahl  nitrogen (TKN), ammonia nitrogen (NH-.-U), nitrate



nitrogen (NO,N), total  phosphorus  (Tp), 5-day 20 C biochemical oxygen




demand (BOD), chemical oxygen demand (COD), and dissolved osygen (DO).



       Table 14 has been prepared to show additional characteristics of




denitrification.  The feed characteristics have b.oen taken from Table 13



and the Reaction Tank loading values from Table 12.  The nitrate reduction



rate is given as the milligrams of  nitrateN lost per gram of MLSS per



hour.  In the ratio of BOD/&itrate-N the BOD is the 5-day BOD of that



portion of the raw waste applied directly to the reaction tank.  The



Nitrate-N value is either the amount applied or removed (as indicated)




in the reaction tank, and the respective ratios are shown as BOD/NA and



BOD/N.




       Table 15 is a comparison of  the expected ammonia and organic nitrogen



concentrations in the effluent which originated in the primary feed



compared with the actual concentrations.  Expected values have been



computed as the diluted  concentrations from the portion of the primary



effluent fed to the denitrification tank.




       Throughout the tests the ammonia nitrogen concentration in the



primary effluent feed to the units  was relatively low and ranged from



3-20 tag/I.  Because the  objective of the tests was primarily a study of



denitrification, no attempt was made to optimise the nitrification process.



Consequently to assure good nitrification relatively low loading rates were



used in the first stage.  Dissolved oxygen concentrations in the




denitrification effluent are not very meaningful because of the questionable



reliability of the meter used although there aay have been slight amounts of






                                  -  49 -

-------
               Table 13



DEMONSTRATION PLANT ANALYTICAL DATA
Temp, c
Haw ML
1. Nov. 1-7. 1968- iTr. 	
P: No. of Obs. 5
Mean 19.6
Min. 19.0
Max. 20.0
N: No. of Obs.
Mean
Min.
Max.
D: No. of Obs.
Mean
Min.
Max.
2. Nov. 9-U, 1968  C
P: No. of Obs. 5
Mean 19.1
Min. 19.0
Max. 19.5
K: No. of Obs.
Mean
Min.
Max.
.D: No. of Obs.
Mean
Min.
Max.

TKN NH3-N
6
13.5
11.0
19.2
5
0.8
0.7
1.3
5
3.2
2.3
h.7
h
10.3
7.0
13.6
h
1.0
0.8
1.2
u
U.i
3.0
5.6
Effluent Concentrations,
N03-N TP BOD COD
6 7
O.U 182
0.3 155
0.7 190
6
12.5
11.2
U.O
6
2.0
0,3
3.2
h 6
.O.U 200
0.3 150
O.h 2UO
h
12.5
11.0
Hi .8
h
0.2
0.1
o.h
mg/1
DO








3
0.7
OJi
1.2








h
0.8
0.6
1.0

-------
               Table 13



DEMONSTRATION PLANT ANALYTICAL DATA
Temp, c
Haw ML
3. Nov. 17-21, 196U-=-- C 	
P: No. of Obs. 2
Mean 18 Ji
Min. 18.0
Max. 18.8
N: No. of Obs. 3
Mean 19.2
Min. I6. 8
Max. 19.5
D: No. of Obs.
Mean
Min.
Max.
lu Nov. ?2-Dec. 1, 1968  V
P: No. of Obs.
Mean
Min.
Max.
H: No. of Obs. h
Mean 18.2
Min. 17.0
Max. 19.3
D: No. of Obs.
Mean
Min.
Max.
Effluent Concentrations, mg/1
TKN NH3-N
3
11.5
10.0
12 J
1 3
3.7 1.1
1.0
1.2
1 3
6.7 2.7
2.5
2.8
3
9.7
8.0
1U.8
3
1.8
0.7
U.o
3
U.5
2.14
8.5
3
0.5
0.5
0.5
5
11.0
10.0
12.0
u
o.U
0.2
0.7
3
o.5
0.3
0.7
3
7.6
2.7
9.8
3
1.1
0.7
1.7
TP BOD COD DO
3 5
3.2 196
3.2 188
3.3 230
311
1.8 17 70
1.6
2.1
3113
1.9 11 13 0-8
1.8 0.7
2.0 0.9
10
212
175
220
1
o


1 2
2li 0.8
0.5
1.0

-------
               Table 13



DEMONSTRATION PIANT ANALYTICAL DATA
Terap, c
Raw ML TKN
5. Dec. 6-11, 1968  V
P: ITb. of Obs. 2 l
Mean 16.3 23.2
Min. 15.7
Max. 16.8
: No. of Obs. 3 1
Mean 17 .6 3 .1
Min. 17.1
Max. 17.9
D: No. of Obs. 1
Mean b .6
Min.
Max.
6. Dec. 12-18, 1968 ~ V
P: No. of Obs. 3
Mean 15 .8
Min. 15.5
Max. 16.0
K: No. of Obs. 3
Mean l6-8
Min. 161
Max. 17-5
D: No. of Obs.
Mean
Min.
Max.

3
12.7
11.0
15.2
3
0.9
0.8
1.0
3
3.5
2.5
h.5
l
10.0


2
2.2
0.8
3.5
2
3.9
2.8
5.0
Effluent Concentrations, iag/1
N03-N TP BOD COD DO
3 1 6
0.5 h.6 218
0.3 165
0.6 235
ti 1 1 1
11.7 3.3 13 9h
9.0
Hi .8
h 1 1 1 3
1.3 3.8 8 88 0.7
0.6 0.5
2.5 1-2
2 7
0.3 205
0.2 175
O.h ?30
h
h.7
3.3
8.5
3' 1
0.8 O.U
0.3
1.7

-------
                                  Table 13



                   DEMONSTRATION PLANT ANALYTICAL DATA
Temp, c
7. Dec .31,1968- Raw ML TKN

P: No. of Obs. h
Mean 12.8
Min. U.5
Max. 13.8
N: No. of Obs. 2
Mean Hi .5
Min. 13.8
Max. 15.2
Dt No. of Obs.
Mean
Min.
Max.
*8 Jan. 6-9, 1969  V
Pt No. of Obs. 1 2
Mean 12.8
Min.
Max.
Nt No. of Obs. h
Mean *5.0
Min. U-3
Max. 15-5
Dt No. of Obs.
Mean
Min.
Max.

NH3-N
2
13.lt
8.8
18.0
2
1.1
0.9
1.2
2
3.5
2.7
h.2
1
19.6


1
1.0


1
5.1


_ 	 ,
Effluent Concentrations, mg/1
N03-N TP BOD COD DO
2 6
oM 170
0.3 115
0.1 185
2
10.3
5.6
15.0
2 2
1.5 0.9
0.3 0.9
2.6 0.9
1 U
0.5 220
215
230
1
9.6


1' 2
0.6 0.5
OJ
0.6
* Samples taken every 2 hours for certain 2li-hour periods.

-------
               Table 13



DEMONSTRATION PLANT ANALYTICAL DATA
Temp, c
Raw ML TKN
9.Jan. 10-19,1969  V
P: No. of Obs. 2 1
Mean 13 .U 22.0
Min. 13.0
Max. 13.7
N* No. of Obs. 2 1
Mean ^8 2*8
Min. Hi .3
Max. 15.2
D: No. of Obs. 1
Mean 5.5
Min.
Max.
10. Jan. 20-29, 1969  V
P: No. of Obs. 3 1
Mean 13.8 2U.6
Min. 13.0
Max. lb.5
N: No. of Obs. 2 1
Mean ^8 25
Min. 11* -0
Max. !5.5
D: No. of Obs. 1
Mean h .6
Min.
Max.

NH3-N
1
16.U


2
0.9
0.8
0.9
2
U.2
3.6
iu7
3
Uj.l
11.2
16 Ji
5
2.1
0.2
5.3
6
3.0
0.3
8.5
Effluent Concentrations, rag/1
N03-N TP BOD COD
1 1 10 1
0.5 5.3 212 hh2
165
2U5
21 1
9.5 3.6 79
6.1
12.6
21 1
OJi 3.9 108
0.3
OJi
3 10 1
O.U 210 152
0.3 175
0.5 215
5 11
8.0 16 88
6.0
9.6
6- 11
0.7 20 9U
0.3
1.5

-------
               Table 13



DEMONSTRATION PLANT ANALYTICAL DATA
Temp, c
Raw ML TKN
U.Feb.2ii-Har.8jl9'  C
P: No. of Obs. 9
Mean 13 .7
Min. 12.5
Max. 1^.5
N: No. of Obs. 10
Mean lU .6
Min. 13.0
Max. 15.7
D: No. of Obs.
Mean
Min.
Max.
12. Mar. 19-26, 196? ~ C
P: No. of Obs. 6
Mean 11.7
Min. 7.5
Max. 13.0
N: No. of Obs. 6
Mean 12-9
Min. H-
Max. 13.6
D: No. of Obs.
Mean
Min.
Max.

NH3-N
9
13.2
11.0
16.6
9
2.6
1.3
7.2
10
3.3
1.3
7.9
6
8.2
5.6
9.9
6
1.7
1.2
2.2
6
1.9
1.7
2.8
Effluent Concentrations, mg/1
N03-N TP BOD COD DO
9 13
0.5 216
l
0.3 165
0.6 235
9
3.3
2.3
Iu5
10 7
0.6 0.5
0.2 O.U
1.6 0.6
6 8
0.6 177
0.!4 120
0.7 195
6 1
8.3 2k
7.2
9.8
6 1 6
3.2 13 2.2
OJi 1.6
5.U 3.1

-------
               Table 13



DEMONSTRATION PIANT ANALYTICAL DATA
Temp, c
Raw ML TKN
13 Jlar. 27-29, 1969-=- V 	 	
P: No. of Obs. 2 1
Mean 10.1 20.9
Min. 9.2
Max. 11.0
Nt No. of Obs. 2 1
Mean 13.3 5-5
Xin. 12.5
Max. Ui.O
D: No. of Obs. 1
Mean 8.9
Min.
Max.
Uu Mar.31 - Apr. 3, 1969  C
P: No. of Obs. h
Mean 12.1
Min. 10
Max. 13.5
N: No. of Obs. h
Mean 13 M
Min. 10.7
Max. 15.7
D: No. of Obs.
Mean
Min.
Max.

NH3-N
1
10.8


1
2.7


1
3.3


I
7.6
2.6
12.0
1*
1.1
0.5
1.6
U
1.7
0.7
2.7
Effluent Concentrations, rag/1
N03-N TP BOD COD DO
1 31
0.7 165 372
150
185
1 1
6.5 18


1 111
0.7 35 162 0.9


h h
OJi 193
0.3 190
0.5 195
k
8.7
7.3
10.8
U
2.U
o.U
U.2

-------
                                Table 13



                 DEMONSTRATION PLANT ANALYTICAL DATA
Temp, c
ft Raw ML TKN
. Apr.7-9, 1969 -=~C 	 	
P: No. of Obs. 3
Mean 15.3
Min. 15.0
Max. 15.5
Ni No. of Obs. 2
Mean 16.0
Min. 15.0
Max. 16.5
D: No. of Obs.
Mean
Min.
Max.
16. May 12-15, 1969  C
P: No. of Obs. 3
Mean 17.6
Min. 16.8
Max. 19.0
N: No. of Obs. 3
Mean 18.0
Min. 17.0
Max. 18.9
D: No. of Obs.
Mean
Min.
Max.

3
12.7
11.2
lii.O
3
IJi
1.U
1.5
3
2.8
2.5
3.2
3
13.3
13.1
lb.2
h
1.2
1.0
1J
h
2.8
2.5
3.1
Effluent Concentrations,
N03-N TP BOD COD
3 3
O.U 185
0.3 180
OJi 195
3
13.3
10.8
15.3
3
5.1
1.7
8.2
3 It
0.6 192
O.U 185
0.7 195
U
10.1
8.U
11.0
h
1.1
0.6
2.0
rag/1
DO








3
0.6
0.2
1.0








J
0.7
0.1*
0.9
* Samples taken every 2 hours  for certain 2U-hour periods.

-------
                                 Table 13



                  DEMONSTRATION PUNT ANALYTICAL DATA
Tenp, c
t Haw ML
LTJIay 19-26,1969 -^~c~ '
~P: NO. of Obs. I;
Mean 18.3
Min. 18.0
Max. 19.0
Ns No. of Obs. 5
Mean 17.6
Min. 17.2
Max. 18.2
D: No. of Obs.
Mean
Min.
Max.
18. May 27- July 22, 1969 V
P: No. of Obs. 32
Mean 20.7
Min. 17 .li
Max. 21.0
N: No. of Obs. 6
Mean 20.8
Min. 18.0
Max. 23.8
D: No. of Obs.
Mean
Min.
Max.
Effluent Concentrations, rag/1
TKN
1
18.9


1
3.2


1
luO


2
19.3
19.2
19 Ji
2
3.0
2.7
3.3
2
I* .2
3Ji
5.0
NH3-N
3
13.2
10.3
16 J
h
1.2
0.8
1.3
h
2.U
1.0
3.1
28
11.8
8.0
16.5
32
2.0
0.3
6.2
29
3.2
1.3
U.1
N03-N TP BOD COD
3 8
0.6 172
0.5
0.7
U
10.9
9.0
13.8
h
3.7
1.1
8Ji
29
0.6
O.U
0.8
33
9.9
0.5
17 .U
3U-
2Ji
0.3
5.5
165
205








57
175
125
215
h l
20 125
13
29
U 1
19 110
16
22
* Sanples taken evenr 2 hours for certain 2li-hour ceriods.

-------
               Table 13
DEMONSTRATION PIANT ANALYTICAL DATA
Temp, c
Raw ML
9. July 2lj-Aug. 2171969 C 	
P: No. of Obs. 17
Mean 22.6
Min. 21.5
Max. 23.5
Nt No. of Obs.
Mean
Kin.
Max.
D: No. of Obs.
Mean
Min.
Max.
July 2U - Aug. 21, 1969 
P: No. of Obs.
Mean
Min.
Max.
I: No. of Obs.
Mean
Min.
Max.
D: No. of Obs.
Mean
Min.
Max.
Effluent Concentrations, mg/1
TKN NH3-N
1 21
26.5 11.7
9.2
16.2
1 21
3.5 2.7
0.9
9.0
21
3.9
2.7
9.8
C




1 21
1.1 1.7
0.8
7.8
1 21
2.5 1.8
0.9
2.6
N03-N





21
7.8
14.2
13.8
21
0.5
0.2
2.9





21
U.3
0.5
9.3
21
0.8
0.3
2.1
TP BOD COD DO SS VSS

1 27 1 11
9.2 163 U82 255 18?
130
195
1 1311
5.2 132 3.3 55 U8
3.3
k.k
1 1 11
5.8 153 k9 Ul







1 1311
5.U 72 U.U 20 18
1.2
6,2
1 111
6.1 76 39 27



-------
    Table  14.  Demonstration Plant Denitrif ication Test Data
1
1
Test
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1i

Feed
Nitrate
mg/1 N
12.5
12.5
11.0
7.6
11.7
4.7
10.3
9.6
9.5
8.0
3.3
8.3
6.5
6.3
13.3
10.1
10.9
9.9
7.8
4.3

Peed
BOD
mg/1
182
200
196
212
218
205
170
220
212
210
216
177
165
193
185
192
172
175
163
163
Reaction Tank
Loading
BOD/MLVSS
0.56
0.60
0.72
1.10
0.47
0.45
0.16
-
0.35
0.28
0.39
0.28
0.16
0.28
0.34
0.30
0.47
0.53
0.65
0.25
Nitrate
reduction rate
mg N/g MLSS/hr
3.72
2.73
4.16
2.97
2.75
0.89
1.64
1.22
1.97
1.89
1.51
1.30
0.93
1.44
2.09
2.15
2.71
2.74
1.86
1.08
BOD/Hitrate-N Ratio
N-Applied
BOD/NA
3.62
5.12
4.63
6.90
4.85
11.50
3.30
4.71
5.35
3.27
4.85
3.63
3.97
3.71
2.49
3.20
2.68
3.62
5.07
1.71
N-Reiaoved
BOD/N.
*4.31
5.21
4.86
*8.06
*5.43
13.90
*3.87
5.02
5.59
3.58
5.93
*5.91
4.44
*4.86
4.04
*3.58
*4.06
*4.77
5.41
(2.09)
* Partial denitrification

-------
Table 15   Demonstration Plant Effluent Ajmaonia and Organic Nitrogen
Test
No
1c
2c
3c
4v
5v
6v
7v
8v
9v
10v
110
12c
13v
14c
15c
16c
170
18v
1
1*
Nitrification
effluent
0.8
1.0
1.1
1.8
0.9
2.2
1.1
1.0
0.9
2.1
2.6
1.7
2.7
1.1
1.4
1.2
1.2
2.0
2.7
1.7
Denitrification Effluent, mg/L
Expected Proportionate concentrations
M,-N
2.9
2.6
2.5
2.0
2.8
2.2
2.4
3.6
3.4
1.8
1.1
1.2
1.6
1.2
2.1
2.1
2.1
2.2
2.5
0.7
TEN




5.2



4.5
3.1


3.2



3.1
3.6

1.7

Actual concentrations
NH3-N
3.2
4.1
2.7
4.5
3.5
3.9
3.5
5.1
4.2
3.0
3.3
1.9
3.3
1.7
2.8
2.8
2.4
3.2
2.7
1.8
TKET


6.7

4.6



5.5
4.6


8.9



4.0
4.2

2.5

-------
oxygen introduced into the denitrification reaction tank.  Initially



with the gas recirculation mixing the tank seal may not have been tight




and some air may have been introduced by the recirculation of these gases.




Later, the degasifer may have provided some oxygen and also the mechanical




mixer used instead of gas recirculation may have introduced some oxygen.




       2.  Test 1



       This test period was the  first during which meaningful data were



obtained, and there was good nitrification but only partial denitrification.



Reasonable rates of nitrate reduction were obtained.  The BOD/N ratios were



close to optimum.  The best measures of optimum BOD/N ratios should be



when only partial denitrification is achieved.  In Table 15 it is evident



that the effluent ammonia nitrogen was essentially that from the primary




feed to the denitrification tank.




       3.  Test 2



       More complete denitrification was obtained in Test 2 by reason




of a higher BOD/NA ratio.  Very  likely an excess of BOD was being used.




       4.  Test 3



       Reasonably good nitrification and excellent denitrification were



achieved.  Probably a slight excess of BOD was applied to the denitrifying



unit when comparing the BOD/N ratio with that of Test 1.  The TKN value



in the effluent was particularly high due in part to the effluent SS.




The final effluent BOD was excellent at only 11 mg/1.




       5.  Test 4



       The ammonia nitrogen concentration in the feed was particularly




low in this test and only partial nitrification and denitrification was



achieved.  Although high BOD/H ratios should surely result in complete




denitrification such was not the case in this test and no explanation is

-------
evident.   Variable flow was first introduced with this test and the flow




variations were similar to those shown in Figure 19  The maximum flow



to the nitrification unit occured approximately 4 hours after the



maximum flow to the primary unit.




       6.  Test 5



       Nitrification was quite complete but the sludge was becoming less



settleable as evidenced by the rise  in the SVI.  The rising SVI coincides




with the lowering of the temperature of the incoming waste.  Only reasonably




good denitrification was obtained despite the higher BOD/N ratios.




       7.  Test 6



       Nitrification was incomplete  but denitrification was quite good.



Particularly high BOD/fa ratios were  used and consequently denitrification



should be quite complete.  Again the SVI in the nitrification process was




shown to be increasing.




       8.  Test 7



       Neither nitrification nor denitrification were quite complete



but were reasonably good.  Ratios of BOD/ft were the lowest obtained



to date and indicated optimum values of less than 4.0.  During this test



the mechanical mixer was substituted for gas recalculation in the




denitrification tank.



       9.  Test 8



       Despite the short duration of the test and minimal data, the




results were good in that good nitrification and denitrification were



achieved.  The BOD/N ratios used, however, were quite high.  Although the




raw waste temperature dropped to 12.8C in this test and Test 7 there was




not a corresponding rise in the SVI.
                                  - 51  -

-------
        10.  Test  9



        Low raw waste  temperatures  prevailed during this test and a rise



in the  S7I was observed.   Good nitrification and  denitrification was



obtained but a rather high BOD/N ratio was used.




        11.  Test  10




        Nitrification  in this  test  was marginal  but denitrification was




quite complete.   One  of the minimum BOD/N ratios  was  used for this test



and may be considered optimum (3.58).




        12.  Test  11



        Generally  speaking the highest SVT values  were found during this test



and the subsequent tests  numbered  12, 13  and 14*   Coincidentally the



temperatures of the raw waste were the lowest during  this period as well



with values as low as 75 C.   (Probably due to  ice melts).  Again



nitrification was incomplete  but denitrification  was  quite good as expected



with the rather high  BOD/N ratios.  Constant flow was again used and the




results seem to be little influenced by the flow  conditions.  Incomplete




nitrification may have been due to the high loading rates on the aeration



tank; the aeration tank was operated with the highest BOD/taLVSS ratio and




lowest  DT of any  test.  Similarly,  the denitrification reation tank was




operated with a mean  detention time of only 1.3 hrs,  the minimum used in any-



test.




        13.  Test  12



        Nitrification  was  somewhat  improved over Test  11 bat denitrification



was incomplete despite  a  rather high BOD/1! ratio.   A  low effluent BOD was




observed.




        14.  Test  13



        This test was  quite short and only a minimum of data were taken.




Nitrification was not complete  but  denitrification  was good.  The BOD of the
                                 - 52 -

-------
nitrification unit was good at 18 mg/L but that of denitrification was




rather high at 35 mg/1 and very likeXy due to high S3 in the effluent.




Reasonably low BOD/N ratios were used.  Variable flow was used and low




temperatures were encountered.




       15.  Test 14



       Because of the high SVT and  tendency for solids loss the flow was



changed to a constant rate.  Reasonably good nitrification was achieved



but only partial denitrification in spite of a reasonably high BOD/N ratio.



Very low ammonia nitrogen concentrations were found in the raw waste.




       16.  Test 15



       These data were the last obtained prior to shut-down due to high-



water conditions in the Mississippi River, the receiving waters for the



MSSD plant.  Reasonably good nitrification but only partial denitrification




was obtained.  A fairly low BOD/fa ratio of 404 was used.  Haw waste




temperatures were higher than encountered in previous tests.




       17.  Test 16



       After the shut-down period and a period of start-up data were a^ain




taken for Test 16.  Both nitrification and denitrification were quite



good and the minimum BOD/N ratio of 358 was used.   Constant flow was used.




       18.  Test 1?



       The constant flov; conditions were continued and the minimum mean




holding time in the denitrification tank of 1.3 hours was used.  Quite good



nitrification was obtained but only partial denitrification was found.



This is evident fron the low BOD/faA ratio used.  The BOD/N' ratio was close to



that considered optimum.  Next to the lowest nitrification DT was used, that




being 7.7 hrs.  The BOD/iILTSS ratio,  however, was quite low.
                                   - 53 -

-------
       19.  Test 18



       Variable flow v;as again used and ravr \/aste temperatures were




again over 20G.   This  test period v/as of 57 days duration and v/as the




longest of any period analyzed.  Nitrification v;as nob conp'eto and  ::iay




be due to the variable  flow imposed on the systeu.  A reasonable aeration




tank holding time  of 8.3 hours was used together with a lov; BOD/.IL7SS ratio.




Denitrification was not cooplete and v;as probably due to  the  '/.larginal




BOD/MA ratio used. The 30D/LIA ratio v/as higher than considered optimum.




Several effluent BOD's  v/cre taken and both nitrification  and  denitrification




units had average  SCO's of 20 mg/L or less.  Denitrification  v/as




accomplished in a  minimum holding time of 1.3 hours.




       20.  Test 19



       The last test period was for 29 days and involved  a four sta;;e




process.  T'le process  .v:is conducted at constant  "lov: rates.   I?or  tlie first




tv.'o ir-ajcs nitrification v/as noL conplete but denitrification v/as  very




complete.  The latter  v/c.s expected bein tliat high BOD/IIA. ratios v/ere used.




       In the last tv.-o stages nitrification a^ain \;as not quite complete




but the denitrification v/as.  Sctreaely lov; BOD/IIA ratios v/ere used  and




accomplished the desired denitrifications.




       21.  Discussion of Test Results




       a. Overall



       Overall, the  data shov; that nitrogen removal from  a cmnicipal




v/astev;ater by the  denitrification process is posc.'ble. Although in




these particular tests the arr.ionia and organic nitrogen concentrations  in  the




urir.iary effluent v/ere  rather lov/ the results of the tests sho-ild.  be  a^>-licabl




v^here higher nitrogen  concentrations prevail.




       b. Nitrification




       As mentioned previously, optimisation of tlie nitrification  process




v/as not the objective  of these tests and conse-.uieatly very conservative






                                   - 54-

-------
operation was used to assure reasonably co-iplote nitrification.  In those




tests nitrification was accomplished within the 30-)/177SS ratio limits




previously specified and  the niniaun mean aeration tank holding ti:ne




used v/as 8.3 hours.   Evidence of poor settloability of the sludge at




low teriperature v/as shov/n by the high SVT values observed at these




conditions.  Although high SVI values corrolatod w.'.th lov.' to. iperaLurcs




it is believed that temperature is a contributory but not solo cause of




sludge bulking.   Although the effect of to: :pcra ture on nitrification




v;as not thoroughly exa;p.ine:l, reasonably coculete nitrification v.;..s




:.iaintained with aeration  periods of 3.7 hours with noan teuperc-v'.ures as




lov; as 12C.  As  shown  in Table 15, "the ammonia nitrogen residual from the




nitrification process v/as seldom less than 1.0 ::ig/l and the hijhest noan




value v/as 2.7 :ig/l  There is so~ie indication fro::i the data sho,n that




variable flov/ r.iay yield soaov/hat higher residuals than constant flow ratoa.




i'Tevertheless it is believed that consistent concentrations of  ess than




i .0 ag/1 may be obtained  with better operating conditions.  Satisfactory




effluent BOD's were evident.




       c.  Denitrification




       Reasonably coroplete denitrification vas obtained with these lees than




ideal operating conditions.  Holding times in the reaction tank of 1.3 hours




were satisfactory to accoaplish denitrification and probably even shorter




detention times could be  used.  The variable flov; conditions iTiposed on the




process did not seen to have had an appreciable effect on the effluent as




compared to usinc constant flov/ rates.  Although effluent BOD's wore




generally satisfactory  at less than 20 ng/1 it is believed that the high.




effluent S3 concentrations could be reduced with a better designed final




settling tank.  The residual nitrogen from the. denitrification process under




optimum conditions consisted of less than 1.0 :jg/l nitrate nitrogen together
                                   -  55 -

-------
with some ammonia and organic  forms,   l.fost  of  the  organic  nitrogen was




associated with the effluent suspended solids  ail  tlio  aronionia was largely




from the primary effluent added  to the process as  the  carbon source.  In




Table 15 the expected Proportionate Concentrations of  131 j-H and  TKN were




conjputed as the respective amounts in the pri;-ia..y  feed to  the denitrification




unit diluted into the entire flow.  It is evident  fiat these XH,-N values v;ere




consistently and slightly less than the actual IHI^-IT concentrations found




by test.  Such a difference is expected in  view f the conversion of




some of the organicN from the pri:;iary feed to the ITH-,-iJ fora during




processing.  The conclusion to be drawn is  that the effluent nitrogen is




primarily a function of  the additional unoxidised  nitrogen forms added  to




the process when supplying the carbon source.   The use of  a carbon source




devoid of nitrogen would thereby eliminate  most of the nitrogen  from




the effluent.




       Important characteristics of the denitrification process  are




p/esented in Table 14 and Figure 18.    The  relatively  low  feed nitrate




concentrations were expected because of the low nitrogen concentrations in




the raw waste.  The organic loading ratios  (BOD/LXV3S) have been plotted




against the rates of nitrate reduction in terns of mg  nitrate-nitrogen




removed/g MLSS/nr and presented  in Figure 13.   The data in Figure  10  shov/




a relationship between the rate  of nitrate  reduction and the organic  loading




ratio.  By recognising the need  to maintain a  reasonably constant ratio between




the BOD of the carbon source and the substrate to  be reduced, the more




meaningful data should be those  where only  partial denitrification v/as




achieved.  The application of  high ratios would achieve denitrification but




would mean an excessive  use of the carbon source and would not indicate an




optimum and minimum ratio.  The  circled data designate those conditions when

-------

-------
known excesses of substrate were used and \rere not used in the calculation




of the regression line for the plot.  The relationship between R and F was




found to be:




                              R = 5.37? + 0.26




and the correlation coefficient was 0.95*




The linear relationship clearly show the dependence of H on F and that a




constant B03/N ratio should be used to achieve complete denitrification.




It is again noted that the optimum BOD/N ratio nay not be obta'ned directly




from this graph because of methods of averaging and tliat the BOD available




for nitrate reduction has been computed with an allowance for oxyjen




entrained in the denitrification reactor.




       d.  TwoStage Operation




       The operation of the two stage plant utilising tr:o nitrification processes




and two denitrification processes was operable and did result in decreasing




nitrogen concentrations through the  service of units.  Approximately 90^




reaoval of nitrogen was achieved.   It is recognized, however, that such a




process is very likely far more costly than to use one stage with an




external carbon source.



       22.  Process variations over  24-hour periods




       a.  Sampling



       For selected days  samples were taken every two hours and analyzed




primarily for amaonia and nitrate nitrogen, but on occasion samples were




also analyzed for phosphorus, COD and TOG (total  organic carbon).  All of the




data collected are presented  in Tables 16-21 and  Figures 19-42.  The tests




considered most reliable  in so far as the operating conditions and sampling




problems were concerned were  those  for June 5-6,  June 1?-18 June 19-20,




and July 10-11, 1969.  For these dates load curves have been constructed




which combine the now and concentration to give  mass flows.  The data are







                                     - 57 -

-------
             Table 16
DEMONSTRATION PLANT HOURLY DATA
                       Effluent Concentrations,  mg/1
Flow Pates, ml/min
Time Prira-N Prim-D Total
Primary
NH3-N
NC3-N
TP
Nitrification
NH3-N
Denitrification
N03-N TP NH3-N
January 6-7, 1969
9:30 am 2800
11:00 am 3l*OC
1:00 pm 3800
3:00 1*100
5:00 1*100
7:00 3700
9:00 3150
11:00 2500
1:OC are 1850
3:00 1500
5:00 1600
7:00 2150
January 7-8, 1969
9:30 am
11:00
1:00 pm
3:00
5:00
7:00 .
9:00
11:00
1:00 am
3:00
5:00
7:00
2800
3500
^ o^\^
1 S\^\J
1*150
1-100
^700
3150
21*50
2000
1550
1550
2250
January 8-9, 1969
9:30 am
11:00
1:00 pm
3:00
5:00
7:00
9:00
11:00
1:00 am
3:00
5:00
7:00
2800
3500
3900
1*150
1*100
3700
3150
2500
1850
1500
1600
2150
l*5o
500
600
800
1000
1200
1150
1000
750
550
1*50
L5o
Ii5o
500
600
850
1100
1200
1150
1000
750
550

1*50

1*50
500
600
850
1100
1200
1150
1000
750
550
1*50
1*50
3250
3900
1*1*00
1*900
5100
1*900
1*300
3500
2600
2050
2050
2600
3250
1*000
1*500
5000
5200
1*900
(1150)
(1000)
(750)
(550)
()'5o)
(b5o)

3250
iiooo
1*500
5000
5200
1*900
1*300
3600
2600
2050
2050
2600
16.1*
18.0
18.0
17.0
17.2
16:0
16.2
15.3
16.0
15.6
15.0
U*.l*
12.2
16.1*
20.8
23.2
25.2
19.6
20.0
16.8
18.1*
17.0
16.8
11* .8

12.0
lh.0
17.2
20.8
23.2
21.6
17.0
20.8
17.2
16.1*
16.0
13.2
0.1
0.2
0.2
0.3
0.3
0.3
0.3
0.1*
0.1*
0.5
0.7
0.5
o.5
0.6
0.6
0.6
0.7
0.6
0.6
0.6
0.6
0.6
0.6
0.6

0.5
0.6
0.6
0.5
0.1*
0.5
0.5
0.5
o.5
o.l*
o.5
0.7

5.1*
5.1*
5.5
5.1
5J*
5.9
ii.5
5.7
5.8
6.2
6.5
5.7














1.2
1.2
] .1*
1.7
1.6
1.7
2.6
2.0
1.6
1.6
2.7
2.7

1.2
1.0
1.0
1.5
2.1*
2.0
2.5
2.5
1.3
1.3
1.0
1.0

7.8
7.0
6.8
6.6
6.3
8.0
8.2
-
8.8
9.1*
5.8
5.1*

5.0
6.2
5.1*
6.8
3.0
3.6
6.0
5.6
8.6
e.u
a.ii
7.1*

5.6
5.7
5.2
1*.8
1*.5
I* .3
!*.!*
l*.l
1*.6
5.5
5.6
5.3














1*.3
3.3
3.0
3.2
l*.o
i*j3
5.3
5.3
5.9
5.1
h.2
1.9
3.1*
i*.l
3.7
5.3
1*.9
5.9
5.7
6.5
5.1*
7.1*

7.0
5.1*
3.3
3.0
1*.2
5.5
6.2
6.6
6.1*
6.0
5.5
5.0
NOo-N TP

0.5
0.5
0.7
1.0
o.s
1.?
0.9
0.3
0.3
0.8
o.5
0.2
0.3 6.3
O.t* 5.8
0.3 5.9
OJ* U.8
0.1* 1*.5
0' i i
U i* .1*
OJ* 1*.0
0.5 U.6
0.5 5.0
0.5 5.6
0.5 5.3
0.5 6.3
._ i
0.1*
o.5
0.1*
o.l*
0.1*
0.1*
0.1*
0.1*
0.1*
OJ*
0.1*
0.1*

-------
                           Table 17
              DEMONSTRATION PLANT HOURLY DATA




                                     Effluent Concentrations,  ng/1
Flew Rates, ml/min
Primary
Nitrification
Denitrification
Tin*
Priia-N
ioril 7-8, 1969
10:30 arc
12:00
2:00 pra
1:00
6:00

8:00
10:00
12:00
2:00 am
lj:00
6:00
8:00
ipril 8-9
10:00 am
12:00
2:00 pir
li:00
6:00
8:00
10:00
12:00
2:00 are
1:00
6:00
8:00
May ?l-?2
I0:00 am
12:00
2:00 pm
li:00
6:00
8:00
10:00
12:00
2:00 am
1:00
6:00
8:00
3000
n
n
it
n

n
w
n
n
n
it
n
, 1969
2800
n
n
n
ft
tt
tt
tt
it
n
n
it
, 1969
3780
n
it
it
n
n
n
n
it
n
n
ft
Priro-D
590
"
n
n
n
n

n
n
n
n
n
n
600
"
n
w
n
n
n
it
n
n
it
n

750
M
"
n
n
ft
ft
n
it
tt
it
n
Total
3590
n
"
n
"
n

"
n
"
n
11
n
3100
n
n

n
n
n
H
N
ft
n
n

1530
it
n
ft
tt
ft
n
tt
ft
ft
It
It
10.8
13.8
15.6
Hu2
H,.e
16.1>
12.2
12.0
1?.6
12.0
11.2
10 .U
12.0
12.2
9.2
10.0
13^8
15^2
15.8
15.?
13.8
12.8
12.0
Hj.5
17.1
17.8
17.1
1U.3
11.5
10.1
11.9
13.7
17.2
15-7
O.U
o.U
0.3
0.3
0.3
o.b
o.l,
o.l
0.1-
o.5
0.6
c.6
0.5
0.1
0.3
0.3
ell
Cl,
 M
0.1,
o.5
0.5
0.6
c.6
0.3
0.7
o.5
0.6
0.5
0.2
o.5
0.6
C.7
0.5
0.8
0.8






















382
398
335
398
377
366
3U8
566
326
3U6
375
3U6
2.1
2.0
1.5
1.3
1.2
1.5
1.7
1.6
1.6
1.5
1.5
1.7
1.2
1.2
1.2
1.1
1.1
1.1
1.1
1.2
1.1
1.6
2.0
2.6
1.0
1.0
l.C
0.9
1.0
0.9
0.9
0.9
0.8
0.8
0.9
0.8
15.6
Ll.8
15.1
11* .8
ll.li
U.o
12.8
12.0
12.6
12 .0
8.8
7.C
7.L
8.0
9.2
9.1;
9.2
10.0
8.6
9.2
9.C
8.2
8.0
7.8
8.3
8.3
8.3
8.8
1C.1
11.5
12.2
11.6
11.1
10.9
10.6
10.2















95
82
814
87
89
81,
76
72
Bh
70
72
68
3.1'
3.7
3.6
2.6
3.5
3.?
3.0
2.7
3.0
2.8
2.U
2.5
2.5
2.5
9 1
 -'
2.1
2.1;
2.6
2.5
2.7
2.7
2.9
3.0
2.8
1.8
1.5
1.6
1.5
2.C
1.7
2.2
l.li
1.3
1.1
1.8
1.9
8.5
8.6
7.3
6.3
5.7
5.5
5.1
5.1
lul
2.2
3.1
2.1;
2.0
1.1
11,
 M
1.1,
1.1
0.8
0.7
0.8
0.8
0.7
0.7
1.1
0.6
0.7
0.6
0.6
0.9
0.6
1.7
1.8
2.7
2.2
2.h
2.0















93
119
128
130
128
Hj7
112
136
139
11*3
239
88

-------
                           Table 18
              DEMONSTRATION PIANT HOURLY DATA




                                     Effluent Concentrations, ng/1



Flew Rates, ml/rain
Primary
Time
fcy 22-2;
"9:30 am
11:30
1:30 pm
3:30
5:30
7:30
9:30
11:30
1:30 am
330
5:30
7:30
Jane U-5
9:30 am
11:00
1:00 pm
3:00
5:00
7:00
9:00
11:00
1:00 am
3:00
5:00
7:00
June 5-6
K:30 am
12:00
2:00 pm
!:00
6:00
8:00
10:00
12:00
2:00 am
li:00
6:00
8:00
Prim-N
3, 1969
3750
n
n
n
n
n
n
n
n
n
n
n
, 1969
3300
U900
5500
5600
5350
1850
3950
3150
2700
2liOO
2500
2950
, 1969
U150
5150
5600
5100
5200
UiOO
3600
2900
250C
2350
2650
3300
Priai-D
750
"
n
n
n
n
n
Total
b530
n
ft
n
n
n
n
MALFUNCTION
11
n
n
n

610
5UO
550
600
7UO
930
1110
1190
iiUc
970
850
730

580
560
570
750
820
1035
1170
1180
1060
920
770
660
n
n
n
n

3910
51&0
6050
6200
6090
5780
5060
U3liO
3810
3370
3350
3680

U730
5710
6170
5850
60?0
5ii^5
U770
1-.080
3560
3270
3120
3960
Nitrification



NHo-N  NO-j-N
Denitrification
10.1
12.9
15.14
16.2
16.0
15.7
16.0
16.0
114.8
15.7
Hi .8
1L.O
11.6
13.0
15 .h
15.0
15.1
Hi .6
13.7
13.9
1U.U
lli .7
Ui.ll
13.2
10.1
13.5
16.2
15.8
16.0
12.8
12.6
13.1
12.1
12.5
12.6
11.6
0.6
0.6
0.6
0.6
0.6
o.5
0.6
0.6
0.6
0.6
0.6
0.6
























1.0
l.C
1.0
1.0
1.1
1.1
1.1
10.0
8.8
8.6
8.6
8.8
10.2
9.h
1.14
1.3
1.3
iJi
1.3
1.3
1.3
1.14
1.14
iJi
1.14
1.14
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.1
1.2
11.8
9.6
9.2
9.8
9.2
10 .C
B.h
9.0
8.8
9.6
10.2
10. C
11.0
10.8
10.1
10.6
11.0
11.8
11.8
12.2
12.0
12 .h
12.6
13.6
2.3
2.1
2.1
2.2
2.3
2.3
2.1
2.0
2.2
2. a
2.5
2.8
2.6
IJi
1.2
1.2
1.2
1.2
1.3
1.2
iJi
3.1
3.6
14.3
1.9
1.3
1.14
1.5
1.6
1.7
1.9
2.3
2.5
3.14
3.6
3.1
1.8
1.5
T.I
3.14
3.1
li.l
Iu3
6.2
5.8
5.8
5.9
5.8
0.5
OJi
0.9
3.5
h.9
h.5
U.3
14.6
2.5
0.8
0.7
0.6
0.6
1.8
2.7
2.8
2.9
2.3
2.C
1.1
0.7
1.0
l.C
1.0

-------
DEMONSTRATION PLANT HOURLY DATA
                       Effluent Concentrations, mg/1
Flow Rates, ml/rain
Time Prim-N
June 16-17
9:30 am
11:00
1:00 pm
3:00
5:00
7:00
9:00
11:00
1:00 am
3:00
5:00
7:00
June 17-18
10:00 am
12:00
2:00 p
1*:00
6:00
8:00
10:00
12:00
2:00 am
14:00
6:00
8:00
June 19-20
8:30 am
10:00
12:00
2tCO pm
b:00
6:00
8:00
10:00
12:00
2:00 am
U:00
6:00
, 1969
3500
U75o
5300
5350
5150
1650
3850
3000
2150
2020
2200
2750
, 1969
3750
U800
51*00
5350
5150
UUoo
31450
2850
21*50
2200
21*00
2900
, 1969
3100
1*250
5100
5600
5550
5250
1*650
3750
2900
2500
2liOO
2600
Prte-D

61*0
600
610
700
830
1010
1220
1320
1290
1190
990
810

650
600
620
680
800
960
1160
1290
1320
1220
10UO
820

680
620
600
650
760
920
1130
1280
1310
121*0
1070
870
Total

l*lltO
5350
5910
6050
5980
5660
5070
1*320
371*0
3210
3190
3560

1*1*00
5Uoo
6020
6030
5950
5360
U610
1*11*0
3770
31*20
?l*l*o
3720

3780
hS70
5700
6250
6310
6170
5780
5030
1*210
37UO
31*70
3i*70
Primary
NH3-N N03-N

11.8
12.3
12.7
13.1
13.5
13.1
12.1
12.9
12.2
12.9
13.2
10.0

10.3
13.2
15.0
15.6
16.8
15.8
11* .2
H.J*
1* .3
13.7
12.7
10.8

10. C
10.8
13.6
12*. h
1U.8
15.2
15.2
15.2
HiJi
11* .8
16.0
11* .0
Nitrification
NH3-N

1.8
1.6
1.1*
1.3
1.0
1.0
1.1
1.2
1.2
1.2
1.2
1.1

1.1
1.1
1.1
0.9
1.1
1.0
1.2
1.0
1.0
1.1
1.0
1.1

C.9
0.9
1.0
0.9
1.0
1.0
0.9
0.9
C.9
0.9
0.9
0.8
N03-N

16.2
12.2
13.0
10.0
10. C
10.2
10.0
10.6
11.0
11.6
12.0
12.8

13.1*
11.8
11.2
9.8
10.2
9.2
10.0
10.2
11.0
11.2
12 ,C
11.2

9.6
8.1;
8.8
7.6
6.8
7.2
7.8
8.1*
10.1*
10.2
12.0
12.6
Denitrif ication
NH3-N

2.7
1.9
1.7
1.6
1.6
1.8
2.1*
3.0
3.8
3.8
U.2
1*.7

1*.7
2.8
1.1*
1.2
1.6
2.3
2.5
3.2
U.c
3.7
3.1*
i*.2

1.1
1.1*
1.3
1.3
1.2
2.0
2.2
2.1*
3.0
U.I
U.U
U.3
N03-N

2.1
U.o
3.1
3.8
2.7
1.U
0.5
o.U
0.3
o.U
oj*
0.1*

0.2
0.2
0.6
1.0
o.5
0.2
0.2
0.1
0.3
0.2
o.U
0.3

3.5
l.U
2.1
2.1
1.U
0.8
0.6
0.6
(U
0.6
0.6
0.6

-------
               Table 20



DEMONSTRATION PUNT HOURLY DATA
                          Effluent Concentrations, rag/1

TiJ
June 19-20
8:30 am
10:00
12:00
2:00 pm
U:00
6:00
8:00
10:00
12:00
2:00 an
U:00
6:00
Flow
Pri-N
, 1969
3100
U250
5100
5600
5500
5250
U650
3750
2900
2500
2hOO
2600
Rates, ml/Bin
PriJB-D

680
620
600
650
760
920
1130
1280
1310
121*0
1070
870
Total

3780
U870
5700
6250
6310
6170
5780
5030
Ii210
37UO
3U70
3U70
Priiiaiy
COD

3I1

338
338
368
356
315
35h
112
396
1,08
368
TOO

96
91
95
83
101
101
90
102
110
115
120
110
Nitrification
COD

U*

52


73
73
83
67
67
52
69
COD

20
20
21
20
19
19
17
18
18
18
17
17
Denitrification
COD

118
102
118
102
111*
108
106
Uli
91*
9k
78
98
TOO

30
32
31
30
30
26
26
31
36
33
31
33

-------
             Table 21



DEMONSTRATION PLANT HOURLY DATA



                       Effluent Concentrations,  mg/1
Flow Rates, ml/rain
Time Prim-N
July 10-11.
7*30 a
9*30
11:30
1:30 pn
3:30
5*30
7:30
9:30
11:30
1:30 am
3*30
5*30
. 1969
2200
2900
3700
U700
5300
5500
5000
U300
3300
2500
2000
1900
Prim-D

800
700
1000
1200
1300
1200
1200
1100
800
800
800
800
Total

3000
3600
U700
5900
6600
6700
6200
5200
Uioo
3300
2800
2700
Primary
NH3-N N03-N TP

6.8
5.8
5.6
8.2
7.U
8.8.
8.0
7.9
9.2
8.0
5.2
5.8

10.5
5.7
6.7
5.8
7.3
9.5
10.0
8.U
8.5
7.9
6.7
7.3
Nitrification Denitrif ication
NH3-N

0.9
0.8
0.8
0.8
0.9
0.9
0.8
0.9
0.9
0.9
1.0
0.9
N03-N

8.U .
8.8
9.6
9.8
8.2
9.2
8.8
8.8
9.0
9.6
9.6
11.U
TP 1

U.o
U.I
U.o
U.o
3.7
3.U
3.3
3.5
3.U
3.7
3.1
U.5
JH3-N

3.5
2.6
2.1
1.6
1.5
1.7
1.7
2.2
2.8
2.U
2.8
3.0
N03-N


o.U
o.U
o.U
o.U
o.U
o.U
O.U
o.U
o.U
0*
o.U
TP


2.8
2.5
2.5
2.2
3.2
3.5
3.U
U.2
3.6
U.I
U.2

-------
/ */  3      5~

-------
FIGURE

-------
"T
3
7
T
//
SAMPLING
    9-9,
                3

-------
i:
  to
  e
    iff

T
e
T~

                          SAMPLING
                            7-8 ,
                                                  6

-------

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         T
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T-  -T
6   *
'T/MS
          1+-HOVR  SAMPUMG DATA
                 QPRIL &-9, 19&9
                                       F/GUZE 23

-------
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r*w

y*n
yt*t
tfffO

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. PRIM, TO
1 L
JZ
&
0
                                               cot>
     At/V
      *   &   t*
       T/M OF  PAY
2 4--HOUR  SAMPL/A/G  DATA
      MAY 2/-22 ,
                                              FIGURE:

-------
   /f
   8

  )
   4

   /?

   0
is
         A///,-/
                  \
                  Z.
\
6
                  -HOUR SAMPLIM6 DATb
                             22-23
                                                          M>3->Y

                                                         /\/^-/
 \
8

-------
II
i    i    i   r   i^   i
S   7   9   H   /** 3
   T/M  OF
                 SAMPLING DATA
           JUME  4SJ&69

-------
FIGURE 2J

-------

-------
JUNE I7-I\I969
FIGURE

-------

-------

-------

-------
z&-Jtom s AM PUN 6
PRIMARY M#3-N , CONSTANT FLOW
                                    
-------
24-HDUR 5AMPLM&
 PRIMARY A///3
                                    F/GVKE

-------
  Z4-HQUR  SAMPLING >ATA SUMMARY
N/r&F/cmON A///3W,  CONSTANT FLOW



                                        F/GU&E

-------

    " /' V
    -> /

'PLI.N'$
    SUMMARY
VARlflBLE FLOW
            '

-------
   24-HOUR  S
OENITRIFICATION
                                       FIGURE  3/

-------
   Z4-HOLJK  SAMPLING J34TA SUMMaR.Y
DENITRIFICATION NH^N ,  VARIABLE FLOW


                                            3$

-------
 4-HOUR  SAMPLING DATA
N/TR/F/CAT/ON M03~M , CON$7AMT
                  T	   	\
                                       F/GURE 3?

-------
 24- -HOUR. SAMPLING DATA
N/TRIF/CATION NO^N ,  VARIABLE FLOW
                                        FIGURE

-------
  24-HOUR  SAMPLING  DATA  SUMMARY
DENlTR/FtCATtON  NO^N, CONSTANT FLOW
                                       FfGUZE  *H

-------
  24'HOUR.  SAMPLING DAT/)
DEN ITRIFICA TtON N03 -N ,
                                        FIGURE   4-1

-------
w/r

-------
.

-------

-------

-------

-------

-------
presented graphically in Figures 43-48.  Although all of the data collected



are presented in the tables and figures, the following discussion will be



liaited to the June and July data for variable flo'.. conditions only.




       b.  Discussion



       (1)   General Observation



       No attest at this tiae will be oade to describe the trends  in  the



data using a nathenatical model.  Only general observations with the




probable significance of such will be made.



       Output concentrations from the reactors are a function of the



input concentrations, physical and biological nechanisns effecting  treataent



in the units, and the flow variations to the processes.  In these tests  the



continuous use of a nunicipal wastewater at itc source provided continuously



varying input concentrations.  Flow variations were ioposed on the  process



by intentional and continuous variations in the puoping rates.



       The data froa each of four tests conducted in June and July  as



described above are shown graphically in Figures 27,29,30,31 and 32.



These data are also shor/n in Figures 34, 36, 33, 40 and 42, where they are



grouped together with similar data from other teats.  Since the January



data shown on these figures are not considered to be significant it should



be ignored when evaluating the data.  As described previously, mss flow



curves for these tests are presented in Figures 43, 44, 45 46, 4?  and 48



       Aside froa the low values found  on July 10, the amaonia-N concentrations



in the priaary effluent as presented in Figure 34 sho\7ed an unexpectedly



small diurnal variation, and the mean daily concentrations were quite  similar.



The majority of these concentrations varied between 12 and 16 mg/1.



       (2)  Nitrification Process



       As described above, the input ammonia concentrations to the  activated



sludge process which accomplished the nitrification were reasonably



constant.  It is inportant to note the  operating conditions of the  activated

-------
sludge plant as shown in Table 12 (Test 18).  A reasonably long mean



detention time of 8.3 hrs was used, and the BODA&VSS ratio was quite



low at 0.17.  With these very conservative operating parameters the effect




of now should be less evident that if shorter holding times and higher




BOD/EJLVSS ratios would be used.  Under these particular conditions of




operation the output ammonia concentrations wore generally less than 1.5



and quite constant throughout the 24-hour period.  Essentially complete




nitrification was being obtained.



       The nitrate concentrations showed more of a diurnal variation than




the ammonia.  Prom similar earlier tests it was observed that with a constant




input ammonia concentration the output nitrate concentrations seemed to




vary inversely with the flow rate.  A similar observation may be made with




these data.  The nitrate concentrations seem to be minimal during the high




flow periods and higher daring the low flow periods.  Again  this implies




an  increased assimilation of ammonia during the high  load period which



consequently leaves less retraining to be oxidized.  This observation is



somewhat reinforced by observing  the load  (or mass flow) curves where  the



ordinate difference between the input ammonia and output nitrate curves are




far more during the high flow period than  during the  low flow.



        The  COD and TOC concentrations were quite constant and of low




concentrations during the test on June  19-20.




        (3)  Denitrification



        Ercept for the test on July 10-11,  the primary effluent  pumped  to




the denitrifying unit as the carbon  source was  not in phase  with the flow



to  the nitrification plant.  On  the  basis  of  the load curves it may be said




in  retrospect  that  it would be desireable  to keep these floors  in phase.
                                   - 59 -

-------
Although the mean BOD/N ratio used in the tests was higher than that




considered optimum, the excess BOD applied was very likely not so much




as to mask the variation in the input nitrate load.  From the nitrate



output curves for the denitrification units it is evident that insufficient




carbon was supplied to the denitrification plant during these periods when




the input nitrate load was the greatest.  This is shown by the consistent




and incomplete denitrification during these periods.  When the main



plant flows were at a minimum sufficient carbon was supplied to miniaize



the output nitrates.  In the test on July 10-11 when the two flows were



in phase the nitrate concentration was consistently low at less than 1.0 mg/1.



       In all of the tests there was a cyclic variation in the output



aanionia concentration fron the denitrification process.  In the June



tests when the two flow rates were not in phase the aoaonia concentrations



varied approximately with the flow rate of the raw waste to the denitrification




unit.  It is possible that there was a deficiency in nitrate to satisfy the



higher rates of aetabolisn during the periods when the carbon load to the




denitrification unit was the greatest.  As a consequence of this the




growth and uptake of armonia was limited once the nitrates were depleted



(at a low level) and the effluent ammonia concentrations increased




accordingly.  In contract to this in the July test when the two flows were




in phase,  the growth process was not nitrate-limited during the high load



period and the effluent amnonia concentration showed considerably less




variation and, in fact was a minimum during the high load period.   With a



carbon source free of nitrogen (e.g. with methanol) such variations would




not exist,  but the implications of growth and effect on the effluent in terms



of COD,  or BOD,  or soluble carbon would be similar.
                                 - 60 -

-------
       Phosphorus data obtained daring the July 10-11 test show
similarities to the amaonia data.  Essentially little or no phosphorus
is removed in the denitrification process.  Effluent COD and TOG values were
higher daring the June 19-20 test in the denitrification process than in
the nitrification plant effluent.  This could very likely be remedied by
eoploying a lower BOD/fa ratio.
       Overall it nay be concluded that it is essential to use a proper
BOD/to ratio during the complete flow cycle, and if done properly a
completely denitrified effluent may be obtained.  The Bean holding time
used to accomplish this (see Table 12, Test 13) was  1.3 hours in the
airing tank and very likely an even shorter tioe could be used.
                                 - 61  -

-------
                              YII.  CONCLUSIONS



       It has been shown that complete miring biological waste treatment



systems may be operated in series with a municipal wastewater to remove



nitrogen by nitrification followed by denitrification.  The activated sludge



process used for nitrification was operated at non-critical loading



rates and consequently optimum operating conditions cannot be reconmonded.



Aeration times of 7-9 hours were used together with appropriate MLSS



concentrations to produce completely nitrified effluents at te.-aperafcures



as low as 10-12G.  Variable flow to the units did not change the



effluent quality from that obtained with constant flow conditions.  It is



virtually certain that a niunicipal treatment plant operated as described



above will produce an effluent in which the soluble nitrogen is in the



nitrate form, except for an anmonia-N fraction of less than 1.0 ag/1.  Even



with variable flow rates the ammonia-!! concentration should not exceed



1*0 rag/1 at any tiae.



       Denitrification was obtained with a raan reaction tank detention time



of 1.3 hours at 20C and in 2.6 hours at 10C teapera-ures.  Effluent



quality was essentially the same whether constant or variable flow was



used.  The effluent characteristically had a BOD concentration less than



20 mg/1 and although the SS concentration were generally higher it is



believed that these high concentrations were due to adverse hydraulic effects



in the particular separation facilities used.  The soluble amaonia-N in the



affluent was shown to be almost solely due to the nitrogen added with the



carbon source to the denitrification reactor.  By usin a nitrogen-free



carbon source an effluent practically devoid of nitrogen may be obtained.
                                   - 62 -

-------
       The extent of denitrification was shown to be dependent on




maintaining a constant BOD/& ratio to the denitrification system.  High



ratios would produce a high carbon (BOD) concentration in the effluent and




low ratios would result in incomplete denitrification.  The ratio should




be kept constant on an hourly basis and this nay be acconplished by



keeping the ratio of the two raw flow rates tho sane at all tines.  The



effluent nitrate concentration may be kept well bolov/ 1.0 mg/1.



       The rate of nitrate reduction in terms of mg N/g MLSS/hr was shown




to be a linear function of the sludge loading rate, BOD/^ILTSS.
                                  - 63 -

-------
                             BIBLIOGRAPHY"

  1.    Johnson, W.  K.,  "Nutrient Removals by Conventional Treatment Processes".
          Proc. 13th Ind. Waste Conf..  Purdue Univ.  Ext.  Ser.  96,  151  (1958).

  2.    Johnson, W.  K. and Schroepfer, G.  J.,  "Nitrogen Removal by  Nitrification
          and Denitrification".  Jrl Water Poll. Cont.  Fed., 36, 8, (1964)  p.105.

  3.    Christiansen, C. W., Rex, S.  H., Webster, W.  H., and Vigil, F.  A.,  "Reduc-
          tion of Nitrate Nitrogen by Modified Activated  Sludge".  U.S.  Atomic
          Energy Commission.  TID-7517  (Pt.1a), 264,  (1936).

 4.    Bringaann, G. and Kuhn, R.  "Rapid  Nitrification of Municipal Sewage  with
          Mineral Carrier Sludge".   Geaundhei tsingenieur,  68,  p.186-18?,  1967.

  5.    Wuhrmann, K., "Objectives,  Technology  and Results  of Nitrogen and Phosphorus
          Removal Processes.  Univ.  Tex.  Water Resour.  3ymp..  1968, No.  1,
          21-48.

  6.    Haltrich, W.,  "Elimination  of Nitrate  from  an Industrial Waste".   Prop.
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  7.    Barth, E. F., Brenner, R. C., and  Lewis, C. F.,  "Chemical-Biological
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          Poll. Cont. Fed..  40, 12,  2040,  (1968).

 8.  Ludzack, F.  J., and Ettinger,  H. B., "Controlling Operation  to Minimize
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          9, 920 (1962).

 9.    Balakrishnan, S., and Eckenfelder, W. W., "Nitrogen Relationships in
          Biological Treatment Processes.  III. Denitrification in the Modified
          Activated Sludge Process.  Wat. Research. 1969,  3, 177-178.

10.   Mulbarger,  M. C., Page, G.  L., Yates, 0. W.  and  Sharp, N. C., "Uajiassas Va.
          Adds Nutrient  Reaoval to Waste Treatment".  Wat. Wastes Sngng. 1969,
          6, No. 4, 46-48.

11.   McCarty,  P.  L., Beck,  L.,  and St. Amant, Percy,  "Biological Denitrification
          of Wastewater  by Addition of Organic Materials".  Presented at 24th
         Annual Purdue  Industrial Waste Conference, Purdue University,
         Lafayette, Indiana,  May,  1969.

12.   Verhoeven,  W. "Some Remarks  on Nitrate and Nitrite ^tabolism in Ilicro-
         organsms".  A  symposium  on  Inorganic Nitrogen ^tabolism.  The John
         Hopkins  Press,  Baltimore, 1956.

13-   3re;mer,  J.  M., and.  Shaw, K. ,  "Denitrification in Soil".  J. A,?ri. Sci. .
         51(1),  21-51,  (1958).

14.   Downing, A.  L., Painter, H.  A.,  and Knowles, G.  "Nitrification  in the
         Activated Sludge Process".   J. Proc. Inst.  Sew.  Purif..  1964, 130.
                                  -64-

-------
 15-   MoKinney, R.  E.   "Mathematics  of Complete-Mixing Activated  Sludge".
         Jrl.  San.  Bag. Div.. ASCE,  88,  SA3(l), 8?,  1962).

 16.   Eckenfelder,  W. W.  and O'Connor, D. J.  Biological Waste  Treatment.
         Pergamon Press (1961).

 17.   Schulze, K. L.  "The Activated Sludge Process  on a Continuous Flow
         Culture".  Water Sewage Works.  Dec '64, Jan '65.

 18.   Smith, R., and Eilers, R. G.   A Generalized Computer Model  fear  Steady-
         State Performance of the Activated Sludge Process.  U.S. Dept. Interior,
         PWPCA, Adv. Waste Treatment Br., Div. of Research, Cincinnati, Ohio,
         (1969).

 19-   Hadjepetrou,  L. P.  and Stouthamer, A. H.  "Energy Production During
         Nitrate Respiration by Aerobacter aerogenes".  J. Gen. Microbiol.
         (1965), 38, 29-34.

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