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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(l) General Observations 33
(2) Nitrification Process 58
(3) Denitrification Process 59
VII. CONCLUSIONS 62
VIII. BIBLIOGHAPHT 64
vii
-------
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
-------
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
-------
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
-------
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.
-------
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 -
-------
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 -
-------
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 20°C BOD (BOD,.), mg/1
- 5 -
-------
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 -
-------
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!'
-------
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 -
-------
(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 -
-------
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 -
-------
•^
m
-~
-—
±p
——
__
tea rra:
timm
m
m
_—
..:;:
m
: •::
.-
—
-
•
ttn
-
I
':'•'
—
:-T
:::-
itttt tttfi
:::
m ;
I
ffl S
ttttittt
1i
-
•
TT~"
.
:r::
~
:.::
"~
::
...:
tit
, _
r •-::
-
__.
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 4«0. 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 9«1 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 20°C. 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, 20°C)
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°
8—2
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
i»75
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
na»o
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
3«b
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 20°C to 15°C. 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 15°C. 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 20°C 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 10°C 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 -
-------
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 7»0-7»5 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 3«4- 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 3•86. 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 3«3 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 3«4 produced an effluent nitrate-N
concentration of 0.6 mg/1 whereas in a parallel test using a ratio of 4«0 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-
-------
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
ir°r
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 -
-------
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
-------
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
-------
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
-------
FIGURE 7
-------
-------
-------
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 -
-------
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.
-------
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 -
-------
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 -
-------
PORT-
HOLES'
VS
TANK-ELEVKTICN
TANK PLAN\ PORT-HOLE DETAIL
DEMONSTRATION PLANT TANKS- CONSTRUCT/ON DETAILS
FIGURE //
-------
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
J»xO7 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 nitrate—N 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. 16«1
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 2»5
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.8jl£9' — 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
1»i
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 12.8°C 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 7»5 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 4»04 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 3»58 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 20°G. 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 12°C. 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 v«as 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 organic—N 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. Two—Stage 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
3«30
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
3I»1
—
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
-------
$
rJWs
p.
v^
^ z*e
$ 1&6
r\
O
•
m*-~
w /
! ! ! ! ! 1 ; !
1
1
: : :
! ;
-
; ;
1 i i i t i
IN L 4 £ S to
- Tft 7"A /
:
.
£>0JM. TO
I 1 1 1 1
ZAf Z 4 * &
a
c,
flN
T
2,
T- -T
6 *
'T/MS
1+-HOVR SAMPUMG DATA
QPRIL &-9, 19&9
F/GUZE 23
-------
JfVt
JtAnr,
r*w
y*n
yt*t
tfffO
tvv\
A
1
'. '.
•
'•
'
.
1 1
-
1
1
,
1
•
1 1
r/\Jf^f 77}
N/T
. 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 4—SJ&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 10-12°G. 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 20°C and in 2.6 hours at 10°C 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.
22nd Ind. W. Conf., Purdue Univ. Eng. Ext. Series No. 129, 1967, p.203.
7. Barth, E. F., Brenner, R. C., and Lewis, C. F., "Chemical-Biological
Control of Nitrogen and Phosphorus in VTastewater Effluent". Jrnl Water
Poll. Cont. Fed.. 40, 12, 2040, (1968).
8. Ludzack, F. J., and Ettinger, H. B., "Controlling Operation to Minimize
Activated Sludge Effluent Nitrogen. Jrl. Water Poll. Cont. Fed.. 34,
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.
20. Painter, H. A. "A review of Literature on Inorganic Nitrogen Metabolism
in Microorganisms". Water Research, 4, 393, (1970).
21. Chang, J. P. and Morris, J. G. "Studies on the Utilization of Nitrate
by Micrococcus denitrifications". J, Gen Microbiol. (1962), 29,
301-310.
22. Schroeder, E. D. and Busch, A. W. "The Role of ITitrate Nitrogen in Bio-
Oxidation". Jrl. Water PoLL Cont. Fed.. 40, 11, (1968) R445-
23. Downing, A. L. and Wheatland, A. B. "Fundamental Considerations in
Biological Treatment of Effluents". Trans. Instn. Chem. Sngrs.. 40.
(1962).
24. Eckenf elder, W. W. "A Design Procedure for Biological Nitrification and
Denitrification". Chemical Engineering Progress Symp. 3er.. No. 78,
63, p.230-234, 1967.
25. Tamblyn, T. A. and Sword, B. R. "The Anaerobic Filter for the Denitrifica-
tion of Agricultural Subsurface Drainage". Presented at the Twenty-
fourth Annual Purdue Ind. Wastes Conf., Purdue Univ., Lafayette, Ind.,
1969).
26. Seidel, D. F. and Crites, R. W. "Evaluation of Anaerobic Denitrification
Processes". Jrnl of the San. Engr Div.. ASCE, 96, SA2 (1570).
27. Bruce, A. M., Boon, A. G. "Aspects of High-Rate Biological Treatment of
Domestic and Industrial Waste Waters". Presented at Congress of Public
Works and Llunicipal Services, London, 1970.
28. Heukelekian, H. and Rand, ii. C. "Biochemical Oxygen Demand of Pure Organic
Compounds". Sewage and Ind. W. 27, 9, 1040 (1955).
29. Standard Methods for the Examination of Water and Waste-water. 12th Edition,
American Public Health Association, 1965.
-------
30. Uenzel, D. W., Corwin, N. "The Measurement of Total Phosphorus in
Seawater Based on the Liberation of Organically Bound Fractions by
Persulfate Oxidations". Limnology and Oceanography, Vol. 10, Ho. 2,
p.280, April 1965.
31. Qales, M. E. Jr., Julian, E. C. and Kroner, R. C. "Method for Quantitative
Determination of Total Phosphorus in Water". JAWWA, Vol. 58, No. 1»
p.1363, Oct. 1066.
32. Johnson, W. K. "Automated Variable Plow for Pilot Plants". Environmental
Science and Technology. Vo. 4» No. 1, p.68, Jan. 1970.
33. Johnson, W. K. and Schroepfer, G. J. Nitrogen Removal fron Wastewater by
Biochemical Nitrification and Denitrification. Final Report PHS Res.
Grant WP-225, University of Minnesota, April 1963-
34. Downing, A. L. and Hopwood, A. P. "Some Observations on the Kinetics of
Mtrifying Activated-Sludge Plants". Schweiz. Zeits. }{ydrol. 26, 271»
1964.
35. Garrett, M. T., Jr. "Hydraulic Control of Activated Sludge Growth Rate".
Sew, and Ind. W.. Vol. 30, No. 3, P.253, Mar 1958-
36. Moore, S. F., and Schroeder, E. D. "An Investigation of the Effect of
Residence Time on Anaerobic Denitrification". Water Research, Vol. 4»
Oct 1970, p.685-684-
37. Popel, F. "Criteria for Evaluating the Effect of Waste Waters on Receiving
Waters". Vatten, 1967, 23, 17-34-
38. Hama, A. "Nitrification and Denitrification in Biological Sewage Treat-
ment". Hunchn. Beitr. Abwass. -Fisch. -u. Flussbiol., 1968, 5, 331-338.
39. Nilsson, E. S. and Westberg, N. "Bacterial Denitrification of Kitrate
Containing Waste Waters". Vatten. 1967, 23, 35-40.
40. Schmidt,B. and Kampf, W. D. "The Influence of Oxygen in the Denitrifying
Efficiency of Pseudomonas Fluorescens". Arch. Hyg. Bakt., 1962, 146,
171-182; Lit Ber. Wass. Abwass Luft.u. Boden, 1962/63, 11, 275.
41. Bringinann, G. and Kuhn, R. "Semi-Technical Stabilization and Intensifica-
tion of Denitrification1.1 Gesundheitsing., 1964, 85, 19-22.
42. Bringmann, G. and Kuhn, R. "Controlled Denitrification of Surface Waters
by Hydrogen-Oxidation". Gesundheitsing.. 1963, 84, 213-215.
43. Haltrich, W. and JMger, B. "Observations on the Biological Treatment of
Nitrate-Containing Trade Waste Water by the Denitrification Process in
an Activated-Sludge Plant". Gas -u. Waaserfach, 1963, 1C4, 347.
44. Mudrack, K. "Nitre-Cellulose Industrial Waste". Proc. of 21st Ind. W.
Conf. Purdue Univ., Engng Extn Ser. No. 121, 1966, 656-664.
45- Sanple, W. R. "Removal of Nitrogenous Compounds from Waste Waters".
Chem. Engng Progr. Symp. Ser., No. 78, 63, p.223-229, 1967.
-66-
-------
46. Hunerl>erg, K. and Sarfert, P. "Experiments in the Elimination of Nitrogen
from Berlin Sewage". Gas -u. Wasa Fash. 108, 966-969, 1197-1205, 1967.
47- Echelberger, W. P. and Tentay, U. W. "Waste-Water Treatment for Complete
Nutrient Removal". Wat. Sewage Iks. 116, p.396-402, 1969.
48. Bringmann, G. and Kuhn, R. "Rapid Denitrification by the Negative-Pressure
Process". Geaundheitsingenieur. 1965, 86, 16-19.
49- Johnson, W. K. "Removal of Nitrogen by Biological Treatment". Univ. Tex.
Wat, ftesour. Symp.. 1968, No. 1, 178-189.
501 Das, A. C., Jhan, J. A. and Dutta, B. K. "Removal of Nitrogen from the
Fertilizer Factory Effluent by Biochemical Nitrification and Denitrifica-
tion". Technology. Sirdri, 1965, No. 1, 10-14.
51. Wuhrmann, K. "The Removal of Nitrogen and Phosphorus Compounds from
Domestic Sewage. Results of Experiments on a Technical Scale1*. Schweiz.
Z. Ifrdrol.. 1964, 26, 520-558.
52. Wuhnaann, K. "Nitrogen Removal in Sewage Treatment Processes11. Verb, int.
Ver. Lionel. 1962, 1964, 15, 580-596.
-67-
------- |