EPA-R2-73-158
FEBRUARY 1973 Environmental Protection Technology Series
Field Study
of Nitrification
with the Submerged Filter
I
Office of Research and Monitoring
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
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2. Environmental Protection Technology
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5. Socioeconomic Environmental studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
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technology required for the control and treatment
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EPA-R2-73-158
February 1973
FIELD STUDY OF NITRIFICATION WITH THE SUBMERGED FILTER
by
Donald D. McHarness
Perry L. McCarty
Grant #17010 EPM
Project Officer
E. F. Earth
U.S. Environmental Protection Agency
National Environmental Research Center
Cincinnati, Ohio 45268
for the
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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EPA REVIEW NOTICE
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or recommendation for use.
11
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. '20402
Price If 1.25 domestic postpaid or $1 GPO Bookstore
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ABSTRACT
Successful and reliable nitrification of secondary activated sludge
plant effluent was demonstrated in this field study using laboratory
scale submerged rock filters and pure oxygen. The filter also opera-
ted as a highly effective polishing device reducing BOD and suspended
solids by as much as 80 to 90 percent to levels of less than 10 mg/1.
About 90 percent reduction in ammonia nitrogen was obtained with a
detention time of 60 minutes.
Two methods of oxygen introduction were evaluated. One system involved
preoxygenation with pure oxygen at 1 atm of pressure, and required
recycle of treated effluent because of limited oxygen solubility. This
system achieved the greatest efficiency of BOD and suspended solids
removal, and was most reliable, but greater efforts were required to
prevent clogging.
The other system, which employed direct bubbling of oxygen into the fil-
ter, was estimated to be less costly because of a lower oxygen equip-
ment requirement.
The respective estimated costs for treatment of 100 and 5 mgd are 2.8
and 4.8 cents per 1000 gal for a preoxygenation filter and 2.2 and 3-9
cents per 1000 gal for a bubble oxygenation filter.
This report was submitted in partial fulfillment of Research Grant No.
17010 EPM under the sponsorship of the Environmental Protection Agency
by the Civil Engineering Department, Stanford University, Stanford,
California 94305.
111
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CONTENTS
Section
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Conclusions
Recommendations
Introduction
Background
Nitrification
Results of laboratory studies on the
submerged filter
Experimental Procedures
The full-scale wastewater treatment plant
preceding the pilot plant facilities
Pilot plant apparatus
Operational procedures
Analytical techniques
Results of Field Studies
Characteristics of the influent wastewater
Preoxygenation filter with recycle
Bubble oxygenation filter
Diurnal variation in operation
Effluent nitrogen forms
Summary and Discussion
Operating results
Comparison of the results from the field
and laboratory studies
Recycle ratio
Advantages of the submerged filter
Disadvantages of the submerged filter
Estimated cost of treatment
Acknowledgements
References
Publications
List of Symbols
Appendices
Page
1
3
5
7
7
12
21
21
21
26
28
33
33
33
50
56
59
61
61
63
65
68
69
69
73
75
77
79
81
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FIGURES
Page
1 Heterogeneous system composed of substrate in aqueous
solution and microbial population in biological film. 10
2 Diffusion of major ions during nitrification in the
submerged filter (2). ^
3 Flow rates for submerged filter with recycle. 15
4 Rate of ammonia-nitrogen oxidation as a function of
pH for non-adapted culture (2). 17
5 Relative rate of reaction in the laboratory filter as
a function of the percent stoichiometric oxygen
requirement (2). 18
6 Schematic flow diagram of Union Sanitary Plant No. 3- 22
7 Schematic diagram of the submerged filter with pre-
oxygenation and recycle. 24
8 Percent ammonia removal versus time during filter
start-up (preoxygenation with recycle - 60 minute
detention time). 36
9 Nitrogen profile through filter (preoxgenation with
recycle of 2.75j 60 minute detention time; influent
NH_-N cone, of 10.6 mg/1). 38
10 Profile of dissolved oxygen, ammonia, and nitrite
in the preoxygenation filter (60 minute detention
time). 39
11 Rhodamine dye tracer study of the preoxygenation filter. 43
12 Recovery of preoxygenation filter from anaerobic and
idle aerobic conditions. 51
13 Percent ammonia removal versus time during start-up
(Bubble oxygenation system - 60 minute detention time). 53
14 Profile of DO, alkalinity, NH^-N, and NOg-N concentra-
tions in the bubble oxygenation filter (60 minute
detention time). 55
VI
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15 Recovery of bubble oxygenation filter from anaerobic
and no feed conditions (30 minute detention time). 57
16 Ammonia nitrogen variations over 24-hour periods. 58
17 Comparison between ammonia removal efficiencies
obtained in the laboratory and in the field studies
with the preoxygenation filter. 64
18 Flow through submerged filter with recycle. 66
Vll
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TABLES
?aee
1 Results of preoxygenation with single pass operation. 12
2 Results of preoxygenation with recycle operation. 14
3 Results of bubble oxygenation operation. 19
4 Design parameters for Union Sanitary District No. 3- 23
5 Summary of analytical errors. 31
6 Typical characteristics of treated effluent from Union
Sanitary District Plant No. 3. 34
7 Ammonia nitrogen removal in the preoxygenation filter. 37
8 Typical influent and effluent nitrogen concentrations in
the preoxygenation filt'«r. 37
9 BOD removal in the preoxygenation filter. 41
10 COD removal in the preoxygenation filter. 41
11 Suspended solids removal in the preoxygenation filter. 41
12 Suspended solids balance in the preoxygenation filter. 45
13 Suspended solids accumulation in the preoxygenation filter
based on a COD, nitrogen and oxygen balance. 46
14 Suspended solids (S.S.) accumulation based on trapped S. S.
and S. S. production due to nitrification and the oxidation
of organic matter. 48
15 Correlation between carbonaceous oxygen demand and BOD,-
removal. 49
16 Ammonia nitrogen removal in the bubble oxygenation filter. 54
17 Typical influent and effluent nitrogen concentrations in
the bubble oxygenation filter. 54
18 BOD, COD and suspended solids removal in the bubble oxygen-
ation filter. 54
19 Effluent nitrogen forms remaining after nitrification. 60
20 Comparison of laboratory and field results. 65
21 Estimate of filter cost. 71
IX
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SECTION I
CONCLUSIONS
1. Successful nitrification of secondary activated sludge plant efflu-
ent has been demonstrated in this field study with a laboratory
scale submerged rock filter using pure oxygen.
2. The submerged filter not only achieved nitrification, but also acted
as an efficient polishing device to reduce BOD, COD, and suspended
solids from the activated sludge plant effluent.
3. The efficiency of ammonia nitrogen oxidation was mainly a function
of detention time (based on void volume and the untreated influent
flow rate) and the fraction of nitrifying bacteria relative to other
suspended solids in the filter.
4. The oxygen required for nitrification can be added either by pre-
oxygenation of the wastewater at one atmosphere partial pressure
just before entering the filter or by direct bubbling of oxygen
into the filter.
5. For the preoxygenation system the following conclusions can be
drawn:
a. Recycle of nitrified effluent is required for the preoxygen-
ation system because of the limited solubility of oxygen in
waterj the minimum required recycle ratio (recycle flow rate
divided by untreated wastewater flow rate) is a function of
temperature and wastewater BOD and ammonia concentrations.
b. An influent ammonia nitrogen concentration of 14.3 +2.6 mg/1
was reduced 93+3 percent with a recycle ratio of 2.75 and
a detention time of 60 minutes at temperatures ranging from
21 to 27 °C.
c. Under the above conditions, influent BODq values of 35 + 6 mg/1
were reduced about 86 percent to values of 5 + 3 mg/l5 while
influent suspended solids concentrations of 27 + 3 mg/l were
reduced about 87 percent to values of 3-5 + 4 mg/1.
d. In order to prevent clogging, backwashing twice per week at
rates (gravity draining) of 6 to 20 gal/ft^/min were satis-
factory with 60-minute detention-time operation.
e. Clogging became a problem even with the above backwashing pro-
cedure at higher suspended solids loading rates which occurred
at detention times of 30 to 40 minutes.
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f. Although many suspended solids forming and destroying reac-
tions take place within the filter, the rate at which sus-
pended solids accumulate in the filter is mainly a function
of secondary effluent flow rate and suspended solids con-
centration.
6. For the bubble oxygenation system the following conclusions can
be drawn:
a. The nitrification performance of the bubble oxygenation system
at a given detention time was nearly equivalent to the pre-
oxygenation filter, except the starting times and recovery
times after adverse conditions were somewhat longer.
b. Because of turbulence caused by rising bubbles, BODj- and
suspended solids removals were lower and more variable than
in the preoxygenation system; at a 60-minute detention time
the BODc removal was 74+7 percent and suspended solids
removal was 48+40 percent.
c. Clogging problems were less severe than in the preoxygenation
system because the rising bubbles prevented a heavy suspended
solids increase in the filter pore spaces; partial gravity
draining once per week at rates of 6 to 20 gal/ft^/min were
sufficient to prevent clogging.
7- Oxygen consumption within the filter equals about 4.5 pounds per
pound of ammonia nitrogen removed plus about 1 pound per pound
of BODc- removed.
8. Suspended solids interfere with the nitrification process so that
at a given detention time, increased suspended solids concentra-
tions in the influent resulted in decreased efficiency of ammonia
removal.
9. Sufficient alkalinity must be present in the secondary effluent
in order to prevent an unacceptable drop in pH during treatment;
measured alkalinity decreases during nitrification were close to
the theoretical value of 7.1 mg/1 per mg/1 of ammonia nitrogen
oxidized.
10. Estimated construction, operation, and maintenance costs for plants
ranging in capacity from 100 to 5 mgd, based on a 5.5 percent
interest rate and a 20-year design period, range between 2.8 and
4.8 cents per 1000 gal for a preoxygenation filter and between 2.2
and 3.9 cents per 1000 gal for a bubble oxygenation filter.
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SECTION II
RECOMMENDATIONS
A submerged filter with a capacity of about 5,000 or 10,000 gallons
per day should be constructed and operated to demonstrate the feasi-
bility of this process for full-scale operation and to develop more
adequately the technology required to operate and maintain the pro-
cess. Both the preoxygenation filter with recycle and the bubble
oxygenation systems should be evaluated as each has different oper-
ational characteristics which may be more advantageous for certain
treatment requirements. The following should be sought during this
demonstration:
1 . Technology should be developed for minimizing the potential clog-
ging problem, such as use of large rates of air flow to dislodge
solids, use of high backwash rates for disloding and removing
solids, or use of tall filters to promote the rate of downflushing
from the filter.
2. An optimum economical method to interject oxygen into the waste-
water for the preoxygenation system, .should be sought.
3. Possible methods of reducing oxygen requirements in direct bub-
bling systems should be evaluated such as recycle of oxygen,
staging of submerged filter systems, and increasing filter heights.
4. An evaluation of the effect of filter height on the operational
characteristics of the filter should be made.
5. A determination of the optimal distribution system for influent
wastewater, and collection system for treated wastewater should
be made.
6. The advantages of using filter stages should be explored for the
following reasons:
a. To aid in obtaining optimal oxygen transfer efficiency.
b. To investigate the possibility of operating a bubble
oxygenation filter with high effluent dissolved oxygen
concentration to be followed by a single pass preoxygena-
tion filter for obtaining greater efficiency of nitrifica-
tion, and suspended solids and BOD removal.
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SECTION III
INTRODUCTION
Processes for oxidation and/or removal of nitrogen compounds from waste-
waters are needed for several reasons. Compounds of nitrogen can in
certain cases increase the rate of eutrophication of rivers and lakes.
Nitrate-nitrogen, NOo-N, has been implicated as a cause of methemoglo-
binemia in infants. Ammonia-nitrogen, NHo-N, may be undesirable because
of its reactions with chlorine. Perhaps most important, reduced nitro-
gen compounds can exert a significant oxygen demand on receiving waters
through biological nitrification.
Controlled biological nitrification in a treatment system is one method
by which reduced compounds of nitrogen (NHo-N and NOo-N) can be oxidized
to nitrate nitrogen prior to waste discharge in order to reduce some of
the above adverse effects. It can also be used as a first step in the
nitrification-denitrification biological process for removal of nitro-
gen from wastewaters. Nitrification of wastewaters can be achieved
using the activated sludge or trickling filter processes. In order to
obtain nitrification in the activated sludge process, a long biological
solids retention time or sludge age (8C) is required, especially for low
temperature operation. This is sometimes difficult to achieve. The
trickling filter is more efficient at retaining microorganisms, but
suffers because there is no direct control over the retention time of
the wastes in the filter. Again, at low temperatures the process is
difficult to maintain (20).
A recognition of the above limitations led to the development of the
submerged filter for nitrification. This process combines the biologi-
cal solids retaining efficiency of the trickling filter with the hydrau-
lic control of the activated sludge process. This study was conducted
in order to determine the operational characteristics of the submerged
filter and to ascertain its advantages and limitations. The study was
conducted in two phases. The first was a laboratory evaluation of the
kinetics and operational parameters of importance for filter operation.
This study has been reported in detail in an August 1971 progress report
(2). A brief summary of the laboratory study is included in this report
for background information. The second phase was a study of the opera-
tional characteristics of the submerged filter while operating in the
field and receiving the activated sludge effluent from the Union Sanitary
District Plant No. 3, Union City, California. The results of this phase
are reported in detail in this report.
The submerged filter consists of a bed of stones, 1 to 2 inches in dia-
meter, through which wastewater passes in an upward direction. Organ-
isms grow on the surfaces of the stones or in the void spaces between,
and reach concentrations of several thousands mg/1, measured as total
suspended solids. Conditions within the filter are relatively quiescent
so that little loss of the biological solids occurs, permitting biological
-------
solids retention times of over 100 days. In addition, the upward and
submerged flow allows good control over the hydraulic detention time.
The 20-month laboratory study of the submerged filter reported pre-
viously (2) was conducted using a synthetic waste consisting of tap
water containing ammonium sulfate. In general 90 percent oxidation of
20 mg/1 NHo-N was obtained with a detention time (based on raw waste
flow and filter void volume) of 30 minutes at 25 °C and 60 minutes at
15 °G. For the same percent removal, detention times of 90 and 120
minutes were, required at temperatures of 10 °C and 5 °C, respectively.
Oxygen was added to the waste either before it entered the filter or
during passage through the filter. The process was stable and responded
almost immediately to changes in temperature and flowrate without inter-
ruption of service. The filter could withstand unfavorable conditions
such as lack; of'oxygen or low pH, for a period of several days, resuming
operation when conditions become favorable.
The objectives of this field portion of the study were as follows:
1. To determine the applicability of the submerged filter to
the nitrification of a domestic activated sludge plant
effluent.
2. To evaluate a recycle system with prior oxygenation of the
waste-before entering the filter.
3. To evaluate oxygen addition by direct bubbling into the
filter.
4. To determine the influence of activated sludge effluent
suspended solids and carbonaceous BOD on the nitrification
ability of the filter.
5. To determine the applicability of laboratory results to
field conditions of operation.
6. To obtain an estimate of the cost for treatment.
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SECTION IV
BACKGROUND
This section contains basic information for this study. It also contains
a general description of the nitrification process and the results of the
original laboratory study of nitrification in the submerged filter (2).
Nitrification
Nitrifying Organisms and General Growth Factors. Nitrification is a two
stage biological process. A group of autotrophic bacteria represented
by the genus Nitrosomonas, employ nitrification of ammonium (NH^") as
their sole source of energy. In the presence of oxygen, ammonia is con-
verted of nitrite (NO^) plus water and hydrogen ions, with an energy
yield of approximately 65 kilocalories/mole:
Nitrosomonas
NH4+ + 3/2 02 N0~ + 2H+ + HgO (1 )
The second specialized group of microorganims represented by Nitrobacter
are capable of extracting additional energy by oxidation of the nitrite,
generated by Nitrosomonas, to nitrate yielding 17.5 kilocalories per
mole:
Nitrobacter
N0~ + 1/2 02 * N0~ (2)
The nitrifying bacteria employ the energy released from both of the above
reactions for assimilation of cell carbon (from carbon dioxide) as well as
for cell maintenance.
If C H ON is assumed as the empirical cell formulation for nitrifying
bacteria, then the assimilation reaction can be represented by the
following equation:
5 C0g + NH4+ + 2HgO C5H?02N + 5 0^ + H+ (3 )
Equations 4 and 5 describe the overall reactions of nitrification and
assimilation and were approximated by combining Equations 1,2, and 3
together with cellular yields reported for nitrifying bacteria (3).
Nitrosomonas 55 NH + + 5 CO + 76 0 ^
"l° ' "L ~ ^; £j £
C5H?02N + 54 N02 + 52 E^ + 109 H+ (4)
Nitrobacter 400 NO" + 5 CO + NH + + 1 95 0 + 2 HO
£j ^ 4t LI Ci
C5H7°2N + 4DQ N°3 + H+
-------
On this basis, nitrification of 20 mg/1 of ammonium nitrogen would pro-
duce only about 3 mg/1 of Nitrosomonas and about 1/2 mg/1 of Nitrobacter,
while consuming 85 mg/1 of dissolved oxygen and producing 2 moles of
hydrogen ion for each mole of ammonium oxidized. The cells would con-
tain approximately 2 percent of the original ammonium nitrogen (4).
The production of hydrogen ions during nitrification will result in
a decrease in alkalinity of 7.13 mg/1 as CaCOo for every 1 mg/1 NH^-N
oxidized to NOo. In order to maintain a pH above 6.0 some alkalinity
must remain in solution after nitrification has occurred. Calculations
(2) involving carbonic acid equilibria show that at an initial pH between
7.0 and 8.5, the ammonia nitrogen concentration that can safely be oxi-
dized is roughly equal to 1/10 of the alkalinity of the water. There-
fore, in a water with an alkalinity of 200 mg/1 as CaCO^, approximately
20 mg/1 NHs-N could be oxidized while maintaining a pH above 6.0. If
sufficient alkalinity is not present, then lime or some other alkaline
material must be added. In a subsequent part of this section the effect
of a pH value of 6.0 on bacterial growth will be discussed.
Stoichiometry (Equation l) indicates that 4.57 mg of oxygen is required
for complete oxidation of 1 mg NHo-N. Equations 4 and 5, which include
the effects of COg assimilation to cells (Equation 3)5 predict a reduced
requirement,of 3.9 mg of oxygen per mg NIb-N oxidized. The actual oxygen
requirement in practice will be between these values because of long cell
residence time and organism decay, which tends to reduce the actual cell
yield below that given by Equations 4 and 5.
It has been found that nitrification will occur in the presence of high
concentrations of organic matter (50-110 mg/1 BOD) if oxygen is not
limiting. However, it can be expected that a high relative carbonaceous
BOD concentration in the feed to a biological treatment system will
decrease the percentage of nitrifying organisms present within a given
biomass, and as a result, affect the time necessary to achieve complete
nitrification (5).
Kinetics of Nitrification in the Submerged Filter. Monod (6) and Michaelis
and Menton (7) have mathematically formulated a function for describing
the maximum utilization rate of substrate by bacteria similar to the fol-
lowing:
dS_ = kSX
dt ~ K + S (6)
s
» Q
where:- = rate of substrate utilization, mass/vol-time.
k = maximum rate of substrate utilization per mass
of microorganisms, mass/time-mass of active
microbes.
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K = the "half-velocity coefficient," the substrate
concentration at which the rate of reaction is
one-half the maximum rate, mass/vol.
S = concentration of rate-limiting substrate sur-
rounding the cell, mass/vol.
X = concentration of active microorganisms, mass/vol.
The kinetic coefficients k, K , and X vary depending on the substrate,
the particular organisms under study, and the conditions under which
they are grown. The maximum rate is thought to occur when the cellular
enzyme systems have become saturated with substrate.
Any homogeneous system in which substrate and microorganisms are equally
distributed throughout the reactor volume will operate in accordance
with the above equation. An example is the activated sludge process.
However, in the submerged filter diffusion is also an important variable.
Since a definite interface exists between the microorganisms, attached
to the media surface, and the liquid phase, substrate must move across
this interface in order to be utilized.
Figure 1 is a conceptual diagram of how the concentration of substrate
might decrease within layers of biological solids attached to the media.
The substrate concentrations are defined as follows:
S, = substrate concentration in the bulk liquid
phase outside the bio-film.
S. = substrate concentration at the liquid-film
interface.
S = substrate concentration in the film.
S = substrate concentration at the film-media inter-
face.
Diffusion into the biological mass as well as diffusion through the inter-
face most likely control the rate of substrate utilization. At equili-
brium the rate of substrate movement across the interface equals the rate
of substrate utilization by the bacterial film. Haug and McCarty (2) con-
cluded that for any given media an active bio-film thickness of approxi-
mately 1 mm will permit the maximum possible rate of nitrification at 15 C
with an initial ammonium nitrogen concentration of 20 mg/1.
In the submerged filter, the diffusion of substrate materials is quite
complex. Figure 2 shows the hypothetical situation existing in the sub-
merged filter during nitrification. Since CO and 0 are non-electrolytes,
their diffusion coefficients are not influenced by tfie presence or absence
-------
LIQUID-FILM INTERFACE
SUBSTRATE IN
AQUEOUS SOLUTION
FILM-MEDIA INTERFACE
BIO -FILM
CO
oc
h-
z
UJ
o
z:
o
o
UJ
a:
H
co
GO
!D
CO
0
INACTIVE
MASS
So
Figure 1. Heterogeneous system composed of substrate in aqueous
solution and microbial population in biological film.
10
-------
H20
ir°2
BIO-FILM
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Figure 2. Diffusion of major ions during nitrification in the
submerged filter (2).
11
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of other materials. The. ammonium, nitrite, nitrate and hydrogen ions
all are electrolytes. These ionic flows involve moving charges and
thus each influences the movement of the others.
It should be noted that the diffusion coefficient for oxygen in water
is approximately 40 percent higher than for ammonium at the same temper-
ature. Therefore, oxygen when supplied in a stoichiometric amount,
should not limit the rate of ammonium oxidation in a biological film,
Results of Laboratory Studies on the Submerged Filter
The detailed results from the laboratory study were presented previously
(2). A brief summary is presented in the following for background. The
submerged rock filters used in the laboratory study were the same as
used in this field study. The reader may benefit from previewing Section
V, which contains details of the pilot plant apparatus, before reading
this section. The three systems discussed are the preoxygenation system
with single pass operation and recycle operation, and the bubble oxygen-
ation system.
Preoxygenation With Single Pass Operation. In this system,the synthetic
waste ammonium concentration was arbitrarily limited to the amount which
could be oxidized by the quantity of oxygen that could be dissolved in
the waste at one atmosphere of pressure. For example, at 20 °C, the
solubility of oxygen is 43.7 mg/1, and not more than 9.6 mg/1 of ammonia.
nitrogen can be oxidized with this concentration. The results of single-
pass operation with varying temperatures and detention times are listed
in Table 1 for various ammonium concentrations used. At 25 °C, 90 per-
cent removal was possible in slightly over 15 minutes, while at 15 °C
90 percent removal was possible in 30 minutes.
TABLE 1
RESULTS OF PREOXYGENATION WITH SINGLE PASS OPERATION (2)
Average Percent
NHo-N
Removal
70
75-89
95
87
91
88
66
75
92
Based on the influent waste flow rate and the filter void volume.
12
Temp.
o
^
25
15
10
5
Detention
Time(min. )
7.5
15
30
15
30
30
30
60
120
Influent
NIL -N (mg/1)
j
8.0
7.9
8.0
9.7
9.9
10.1
9.7
12.2
11.9
-------
The following rate equation was empirically found to fit the decrease
in NEU-N concentration with time in the filter (-dS/dt):
Rate = - ^ = aSb
dt
log - [^:J = log(a)+b log(S) (7)
where: a = rate constant
b order of reaction
An analysis of the results from the submerged filter operation in the
laboratory resulted in the following equations:
Temp.
oC Equation
HQ r c i 1-48
« -H-^[if]
0.93
15
10
5 -f=0.3t
In these equations the rate is given in terms of mg/1 NEL-N oxidized
per minutes (mg/l-min) and the concentration, S, as mg/1 NIL-N. The
order of reaction constant, b, varied from a value as low as 0.9 to a
value as high as 1.5 depending on the degree of bio-film development
throughout the filter. An intermediate value of 1.2 was used to formu-
late a general equation for temperatures between 5 and 25 °C:
dS 1.2
- -^ = (0.11 T - 0.20) \^\ (12)
where T = Temperature in C
This generalization was allowable because the rate constant, a, varied
linearly with temperature. The above equations are only applicable to
laboratory operation of the filters using a wastewater containing no
suspended solids. The data collected from the bubble oxygenation system
approximated the predictions of the above equations.
Preoxygenation With Recycle Operation. In a preoxygenation system at
one atmosphere, recycle operation is required for any waste in which
13
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the ammonium concentration is greater than can be removed in a single
pass (Figure 3). The recyle ratio (ratio of recycle flow to raw waste-
water flow) must be adjusted to provide enough oxygen in the filter for
the oxidation of the ammonia nitrogen in the wastewater. At lower tem-
peratures less recycle is needed because oxygen is more soluble. Data
was collected at influent concentrations of 20 to 30 mg/1 NEU-N. With
recycle, 90 percent oxidation of 20 mg/1 NHo-N was obtained with a deten-
tion time (based on raw waste flow) of 30 minutes at 25 °C and 60 minutes
at 16 °C (Table 2). Detention times between 60 and 120 minutes would be
required in the temperature range of 10 to 5 °C.
TABLE 2
RESULTS OF PREOXYGENATION WITH RECYCLE OPERATION (2)
Temp. Recycle Detention ^
°C Ratio + Time(Min.)
25 1.7
1 .7
1 .6
16 1.1
1 .1
2.0
3.0
30
45
60
45
60
60
60
Initial
20
20
20
20,
20,
20,
20.2
Average
Percent
NH3-N
Removal
90
95
95
86
91
93
95
Effluent Dissolved
Oxygen
(mg/1)
7.2
6.8
3.2
6.9
6.5
15.3
22.2
Based on the raw waste flow rate and the filter void volume.
+ Recycle ratio = recyle flow rate/raw waste flow rate.
Equations 8 through 11 can be integrated to determine the detention time
required for a given degree of NHo-N oxidation. Multiplying the resulting
detention time by (1 + R) gives the overall required detention time
(tQ = V/Q) based on the raw waste flow rate (Q) and filter void volume (V).
t
o
10b "
a(b-l)
1
(b-1)
S
e
S.
i
(1+R) b ± 1 (13)
where t
detention time required to reduce the NIL-N
concentration from S to S .
w
S = NH -N concentration in the raw waste water.
w 3
S. = influent NH -N concentration to the filter after
mixing of raw waste water and recycle flows:
S. =
1
w
RS
(See Figure 3)
14
-------
en
WASTE
Q,SW
OXYGEN
Q(l-hR)
S: =
w
RS
e
RECYCLE
RQ,Se
EFFLUENT
Q.S,
Figure 3» Flow rates for submerged filter with recycle.
-------
S = effluent NIL-N concentration from the submerged
6 filter. -*
R = recycle ratio necessary to reduce concentration Sw
to a level stoichiometric with the filter influent
oxygen concentration.
a = rate constant
b = order of reaction
Using average values of the rate constants from Equation 13, the required
detention time, t , can be described over the temperature range from
5 to 25 °C: °
V0.2 , ,0.2
t =
79(1 + R)
o 0.11 T - 0.20
/) -(") (H)
e
Based on this equation 90 percent removal of 20 mg/1 NHU-N should be
obtained with detention times of about 20 and 30 minutes at temperatures
of 25 and 15 °G respectively. This range of performance agrees reason-
ably well with that observed in the recycle studies presented in Table 2.
At any temperature a curve of ammonia nitrogen removal efficiency versus
detention time can be plotted making use of Equation 14 and an efficiency
computation.
Operational Characteristics With Preoxygenation. The nitrification rate
in the submerged filter decreased when the pH fell below 6.6 (Figure 4)
(2). However, the nitrifying bacteria acclimated to the lower pH condi-
tions so that after a period of operation the rates of oxidation at
pH 6.0 approximated those normally encountered at pH 7.0 or higher. Below
pH 6.0 nitrification rates decreased rapidly and acclimation was not so
successful. These results suggest that if nitrification is desired, the
submerged filter should be operated to maintain a pH above 6.0. Thus,
if the natural alkalinity of a waste is low, additional alkalinity must
be added to prevent the pH from dropping below 6.0. It should be noted
that Wild, Sawyer, and McMahon (5) found different effects of pH on the
kinetics in the activated sludge process for nitrification. They ob-
served that nitrification was optimal at pH 8.4j 3/4 optimal at pH 7.5
and 9.3$ and 1/2 optimal at pH 7.0 and 9.8. The effects of pH may thus
be somewhat different in the submerged filter and the activated sludge
system, however their studies were with non-acclimated organisms.
A dissolved oxygen concentration of up to 60 mg/1 in the filter did not
inhibit nitrification. However, at oxygen concentrations lower than
the stoichiometric oxygen requirement the rate of nitrification was
lower than normal (Figure 5) (2).
Studies were also conducted to determine the effect of anaerobic condi-
tions and periods with no substrate feed on the operation of the sub-
merged filter. After 7 days of anaerobic operation the filter returned
-------
'E
1.5
1.0
g
1C
IE
5 0.5
LU
h-
cr
7
PH
8
Figure 4. Rate of ammonia-nitrogen oxidation as a function of pH for non-adapted culture (2).
-------
CD
20 40 60 80 100 120 140 160
PERCENT STOICHIOMETRIC 02 REQUIREMENT
200
Figure 50 Relative rate of reaction in the laboratory filter as a function
of the percent stoichiometric oxygen requirement (2).
-------
to 50 percent of normal oxidation rate within 2 hours and 99 percent
within 4 days.
Upon the completion of the laboratory submerged filter study, the sus-
pended solids were removed for analysis. The mixed liquor suspended
solids concentration was 4800-5600 mg/1 (based on the void volume).
An average of 78 percent of these solids was volatile. A gradient of
suspended solids existed in the filter and many solids were not attached
to rocks, but trapped between them. The largest concentration of bacter-
ial cells was at the bottom of the submerged filter along with the
highest N1L-N concentration. Nearly all of the suspended biological
solids produced during treatment were held in the filter, so that the
solids concentration increased as bacterial growth occurred. Initially
increased biological growth led to an increased degree of oxidation.
However, further increases eventually led to short-circuiting and de-
creased efficiency. The hydraulic head loss through the filters was
always quite small and at no time greater than 5-6 inches of water,
even at flow rates as high as 680 ml/min (1.09 gal/ft2) and in filters
which had become clogged with biological solids. At lower flow rates
the head loss was only 1 or 2 inches of water.
Bubble Oxygenation. Bubble oxygenation can supply enough oxygen to
oxidize a high concentration of ammonia in a single pass through the
filter. The ascending bubbles prevented biological solids build-up in
media in the laboratory study. The lack of clogging in the void spaces
and the more uniform development of bio-film compensated for a decrease
in suspended solids necessary for a given ammonium oxidation rate. The
preoxygenation system seemed to follow plug flow kinetics, whereas, the
bubble oxygenation system tended to be completely mixed. In order to
avoid oxygen from becoming rate limiting, the dissolved oxygen concentra-
tion needed only to be stoichiometric with the actual NHo-N concentration
in the filter (Table 3).
TABLE 3
RESULTS OF BUBBLE OXYGENATION OPERATION
Temp.
°C
22
10
5
Detention ^
Time(min. )
30
60
30
60
90
90
120
Influent
NBo-N
mg/1
19.7
19.7
21 .6
20.0
21.6
20.5
20.7
Percent
Removal
89
95
51
86
95
79
93
Effluent Dissolved
Oxygen
mg/1
22
14
31
23
31
34
-
Based on the influent waste flow rate and the filter void volume.
19
-------
Stable nitrification was observed over a six month study period. With
an influent concentration of 20 mg/1 NEL-N, oxidation was approximately
90 percent complete with a detention time of 30 minutes at 22 °c} 60
minutes at 10 °C and between 90-120 minutes at 5 °C (Table 3). Perfor-
mance was equivalent to that observed using p'reoxygenation and recycle
of effluent. Effluent nitrite nitrogen concentrations were somewhat
higher than the 1 to 2 mg/1 characteristically observed with preoxygena-
tion.
20
-------
SECTION V
EXPERIMENTAL PROCEDURES
In this section a description is given of the submerged filter pilot
plant used in the field study and of the full-scale activated sludge
plant, the effluent from which was used as the feedwater for the pilot
plant. Also set forth are the operating and maintenance procedures
and the analytical methods used.
The Full-Scale Wastewater Treatment Plant Preceding the Pilot Plant
Facilities
The field study was conducted at the Union Sanitary District Wastewater
Treatment Plant No. 3 located in Union City, Alameda County, California.
The final effluent from this plant is discharged to a slough which flows
into the east side of South San Francisco Bay. A flow diagram for this
activated sludge plant and a list of unit process design values are shown
in Figure 6 and Table 4, respectively.
The influent municipal wastewater is comminuted with a barminutor and then
pumped into a vacuator which provides the equivalent of primary treatment
by employing both flotation and settling. Next are four aeration tanks
which can be operated in series or parallel} with step aerationj or with
sludge reaeration (contact stabilization). During this study only two
of the tanks were operated and were connected in series. The mixed
liquor suspended solids (MLSS) concentration in the aeration tank was
usually in the range of 3000-3700 mg/1. Continuous sludge returning is
accomplished by the use of uptake pipes along the final clarifier mecha-
nism arms. Sludge wasting is accomplished separately from the center
pit of the clarifier floor. After clarification the effluent is chlori-
nated.
The waste activated sludge is discharged into the influent sewage and is
removed in the vacuator. The digestion system consists of a heated and
mixed primary digester and an open lagoon which acts as the secondary
digester. The overflow from the lagoon is discharged into the influent
sewage and the digested sludge is periodically pumped to the sludge beds.
The influent for the submerged filter pilot plant was pumped continuously
from a channel just after the final clarifier but before chlorination.
Pilot Plant Apparatus
Submerged Filter Design. Two submerged filters from the previous labor-
atory study were slightly modified to use in this field study. The
modifications consisted of enlarging influent and effluent ports to help
prevent clogging. Each filter consisted of a plexiglas column (Figure 7)
6 inches in outside diameter, 5.5 inches in inside diameter, and 3.5 feet
21
-------
INFLUENT
r
-WET WELL-
\
BARMINUTOR
- SUPERNATANT LIQUOR - -|
I
I
ACTIVATED
SLUDGE
WASTING
r
I
RETURNED
ACTIVATED
SLUDGE
AERATION
TANKS
I
FINAL
\ CLARIFIER
PRIMARY 8. WASTE
--ACTIVATED -
SLUDGE
PRIMARY
DIGESTER
H PHOT PLANT]
CHLORINE
CONTACT TANK
SECONDARY
DIGESTER
(LAGOON)
.J
SLUDGE
BEDS
EFFLUENT
Figure 6. Schematic flow diagram of Union Sanitary Plant #3
22
-------
TABLE 4
DESIGN PARAMETERS FOR UNION SANITARY DISTRICT PLANT NO. 3
Design Population Equivalent 35,000
Design Flow (mgd) 3-0
Design Peak Flow Rate (2.5 x average) (mgd) 7.5
Plant Process
Average Flow (mgd) :
Vacuator :
Volume (gal)
Overflow Rate (gpd/ft2)
Detention Time (min)
Aeration Tanks:
Operating Scheme
BOD Loading
(lbs/1000 ft3/day)
Volume (gal)
Detention Time (hrs)
Detention Time with
sludge return (hrs)
Final Clarifier:
Volume (gal)
Overflow Rate (gpd/ft2)
Detention Time with 25^
sludge return (hrs)
Chlorine Contact Tank:
Volume (gal)
Detention Time (min)
Digester:
Primary
Volume (gal)
Detention Time (days)
Secondary (lagoon)
Volume (gal)
Detention Time (days)
Design
122,000
1,900
59
4 tanks
63
670,000
5.33
4.28
385,000
525
2.46
162,000
77
600,000
30
330,000
16
Actual During Study
2.4
122,000
1,482
72
2 tanks (series)
65-85
335,000
3.35
2.57
385,000
415
2.96
162,000
97
600,000
30
330,000
16
23
-------
Recycle Dosing
Chamber 7
Influent Dosing
Chamber ,
To Solenoid
Valves y
_S7_
Recycle
Wet
Well
Effluent
Recycle
Pump
1 minute cyclic
clock & 2
adlustable
tches
-To -
Waste
Oxygenator
^5/8" Plastic
Garden Hose
T
36"
Dispersion
Ring
Influent
Pump
«w
**$m
Sample
Taps
Figure 7- Schematic diagram of the submerged filter with preoxygenation
and recycle.
24
-------
tall. The base was constructed to disperse the waste uniformly across
the bottom of the filter. Eight, five-sixteenth inch diameter holes
were evenly spaced about a four-inch diameter circle. These disper-
sion ports extended through the bottom of the filter into a 5.5 inch
diameter by 1 inch deep open space. The waste to be treated entered
at the center of this open space and flowed upward through the dis-
persion ports.
Sample taps were located at six-inch intervals along the length of the
column with an additional tap three-inches from the base. The taps
extended to the center of the column, so that a more representative
sample could be drawn, and were made of plexiglas tubing, one-eighth
inch inside diameter, and were joined to the wall of the column with
rubber grommets to give a water-tight seal.
Each column was packed with smooth quatzite stone, 1 to 1 .5 inches in
diameter, and filled to a depth of three feet. The stone was hand
packed and graded to eliminate stones of irregular shape. This assured
a uniform porosity throughout the depth of each column as well as simi-
larity between columns. The actual void volume in each filter was
determined by measuring the volume of water required to completely sub-
merge the media. The measured void volume and the calculated porosity
for each filter were as follows:
Fi11er Void Volume (ml) Porosity
No. 1 (Preoxygenation with recycle) 5482 0.392
No. 3 (Bubble oxygenation) 5440 0.388
With approximately spherical media the void space was somewhat larger
where the media rested against the inside of the plexiglas column.
Flat rings, three-fourths inch in width and one-sixteenth inch in
thickness were placed at one-foot intervals to prevent short-circuiting
through the larger void spaces. Such short-circuiting, however, could
not be completely avoided as was observed with dye testing.
Feed and Oxygenation Systems. Each filter was dosed at one minute inter-
vals with small pulses of sample. The two oxygenation methods employed
were preoxygenation with recycle and bubble oxygenation.
Preoxygenation with Recycle. As mentioned earlier an NHo-N concentration
over 10 mg/1 could not be completely oxidized with a single pass through
the filter. Therefore, a recycle system was used to reduce the filter
influent NHo-N concentration to a level at which oxygen saturation did
not limit the attainment of stoichiometric oxygen requirements.
This recycle system is portrayed in Figure 7. The effluent from the
full-scale activated sludge plant final clarifier was pumped into the
influent dosing chamber (hose No. 1) at a constant rate. The excess
influent flow was wasted through hose No. 4. A one minute cyclic clock
25
-------
with two adjustable switches controlled the two solenoid valves on hoses
No 2 and No 3. Every minute valve No. 2 opened and all of the incoming
influent was wasted, leaving a specific volume of influent in the chamber
above hose No. 3- A few seconds later valve No. 3 opened and a measured
volume was pulsed through the valve into the oxygenator. Valves No. 2
and No 3 closed and then flow was again directed into the chamber over
hose No. 3. This cycle was repeated once a minute. The volume of the
chamber over hose No. 3 was varied by inserting objects to reduce the
chamber volume. The recycle dosing chamber and the influent dosing
chamber were operated at precisely the same time and in the same manner.
Once a minute a pulse of influent and a pulse of filter effluent entered
the oxygenator at 1 atmosphere of pressure. The oxygenator consisted of
two plexiglas chambers in series (connected by three 1/8 inch holes)
both having turbine blades driven by variable speed electric motors and
both being supplied with metered 99.5 percent pure oxygen through sub-
merged ports. The oxygenator was very reliable in operation.
The influent pulses from the two dosing chambers were fairly well evened
out after a 8 to 15 minute detention time (based on a combined influent
and recycle flow) in the oxygenator. The still water depth in the oxygen-
ator was normally about 2 to 5 inches, varying with the flow rate. At
high flow rates gas binding in the line between the oxygenator and the
filter caused flow fluctuations which in turn caused the level in the
oxygenator to vary. By partially closing the influent valve No. 6 the
flow remained reasonably steady. Also filter influent line air vents
were used to help relieve air binding problems.
The detention time in the filter varied from 7.5 to 15 minutes per pass
depending on the recycle ratio and the influent waste flow rate. The
effluent from the filter entered an 18 liter recycle wet-well equipped
with a submergible pump which delivered effluent up to the recycle dosing
chamber. The final effluent was discharged from the recycle wet-well.
The flow rates were checked by measuring discharges from the hoses into
the mixing chambers. All of the major piping was made of 5/8 inch garden
hose with the appropriate male and female connectors.
Bubble Oxygenation. The bubble oxygenation filter employed a feed system
exactly like the 1 minute cyclic dosing system of the preoxygenation with
recycle filter. This system did not require a recycle system because
stoichiometric oxygen requirements were easily obtainable. A metered
flow rate of oxygen was continuously injected into the influent line with
a hypodermic needle. Upon entering the filter base the oxygen bubbles
rose through the 5/16 inch dispersion holes and passed-up through the
rock column. Excess oxygen was vented out of the pilot plant facilities
to help prevent corrosion.
Operational Procedures
Sampling. Sampling was conducted on the average of once per week over a
six month period. Usually both 24 hour composite and grab samples were
26
-------
taken to help verify the consistencey of the results.
Composite samples were taken of the influent and the recycle system
effluent through solenoid valves connected to the influent hose No. 1
of both the influent dosing chamber and the recycle dosing chamber
(figure 7). These valves were open 15 seconds out of every 30 minutes
allowing 150-400 ml of sample to flow to a nearby refrigerator for
storage.
Composite sampling of the bubble oxygenation filter effluent was accom-
plished with an effluent wet-well and a float controlled submergible
pump which pumped most of the effluent to waste, allowing from 150-400 ml
to be pumped to the refrigerator during each pumping cycle (20 to 60
minutes). The hose in both composite sampling systems was made of 1/4
inch plastic and latex tubing.
The field study influent composite sampler tended, at times, to collect
samples with too high a suspended solids concentration. Equivalent
samples were collected by a Union Sanitary District Sampler. For this
reason, the District data was more accurate and was used, when necessary,
for all calculations requiring an influent BODq or influent suspended
solids analysis.
The above sampling systems allowed the collection of reliable soluble
nitrogen data. The bubbling oxygenation effluent composite sampler,
however, did not collect representative samples when settleable solids
were present. These samples tended to be low in suspended solids because
of settling of the solids in the wet-well between pumping cycles. There-
fore, suspended solids, BOD, unfiltered COD and unfiltered Organic Nitro-
gen data had to be evaluated from grab samples.
The refrigerated samples were kept between 40 and 50 F. Samples were
not acidified to preserve the nitrogen forms because this has been shown
to cause loss of nitrite nitrogen (8).
Most tests were performed in the laboratory except dissolved oxygen,
temperature, and pH which were measured in the field on grab samples.
Samples from taps along the length of the filter was taken in succession
from the top of the filter to the bottom to obtain an undisturbed sample
at each sampling tap. Samples of about 500 ml in volume were obtained
slowly (about 3 minutes each) to prevent pulling biological solids from
the filter.
Detention time studies were conducted with rhodamine dye as a tracer.
The dye was injected as a pulse into the filter influent line. There
was some dilution of the pulse in the influent chamber (630 ml) and exit
liquid volume (760 ml) above the filter stone.
27
-------
Operation and Maintenance. Once a week the apparatus, excluding the
filter was cleaned to prevent suspended solids accumulation. Some
bacteria tended to grow in the other portions of the apparatus but it
was not a significant population compared to that in the filters.
Backwashing. Backwashing was one of the methods used to prevent clogging
in this filter. As bacteria grow and suspended solids are held within
the filters, clogging eventually occurs. The solids build-up can cause
short-circuiting and decreased efficiency. In order to maintain good
operation, suspended solids have to be removed from the filter periodi-
cally. During suspended solids removal care was taken not to completely
strip the column of bacteria.
During the first five months of operation the preoxygenation filter was
backwashed by gravity through the side taps, the bottom waste taps and
the influent line. Gravity backwashing rates of 6 to 20 gal/ft /min
were attained two times a week in the 3 foot high filter. After five
months of operation this filter finally plugged. Bubbling oxygen through
the filter did not relieve the problem. Small passages were opened, but
other passages remained clogged. Therefore another approach had to be
used. Water discharged through a garden hose nozzle was directed into
the top of the filter. This caused turbulence in the top foot of the
filter, but it did not penetrate well to the bottom of the filter. Water
from the hose nozzle was then directed into the bottom of the filter
through the influent line at the rate of 20 to 40 gal/ft^/min. This
seemed to be satisfactory for unclogging the filter. This backwashing
procedure was then adopted and used on a regular basis (once very 4 to
20 days). At the same time excess solids were removed twice per week
by gravity draining. The filter tended to clog significantly faster with
a 30 to 40 minute detention time than with a 60 minute detention time.
The bubble oxygenation filter needed less backwashing because solids were
continuously lost in the effluent as a result of the turbulence caused
by the rising bubbles. Gravity backwashing (partial draining) rates of 6
to 20 gal/ft^/min were accomplished one or two times a week and were
satisfactory for the control of clogging over a six month period of filter
operation.
Analytical Techniques
Laboratory analyses were performed during the operation of the submerged
filters for the four forms of nitrogen (organic, ammonia, nitrite and
nitrate), pH, alkalinity, dissolved oxygen, temperature, suspended solids,
biochemical oxygen demand (BOD), chemical oxygen demand (COD), and rho-
damine dye concentration (during tracer studies).
Unless otherwise noted the analytical techniques in this section were
obtained from Standard Methods for the Examination of Water and Waste-
water, twelfth edition, 1965 (9).
Organic Nitrogen. Organic nitrogen was analyzed using the Kjeldahl method
described on page 402 of Standard Methods (9). After ammonia was removed
28
-------
by distillation,, a sample was digested and subsequently distilled and
titrated with standard acid. Standard Methods (9) reports a precision
of + 0.03 mg/1 with a recovery of 97.5-98.6 percent over a range of 1-5
mg/1 organic nitrogen.
Ammonia Nitrogen. Ammonia nitrogen determinations were made by the
direct Nesslerization method described on page 389 of Standard Methods
(9). Samples were clarified with zinc sulfate and sodium hydroxide
precipitation and then centrifugation (4500 rpm for 4 minutes). Rochelle
salts were added prior to Nesslerization. A recovery of 97-99 percent
of ammonia nitrogen was reported for this test with a standard deviation
of less than 0.001 mg ammonia nitrogen (9). In this study the standard
deviation of two sets of 10 identical samples was 2 percent for a 15 mg/1
ammonia nitrogen concentration and 5 percent for a 5 mg/1 ammonia nitrogen
concentration.
Nitrite Nitrogen. Nitrite nitrogen was determined by the naphthylamine
hydrochloride sulfanilic acid method described on page 400 in Standard
Methods (9). Samples were clarified using zinc sulfate and sodium hydro-
xide as in the ammonia nitrogen test described above. The precision, as
standard deviation, on sewage effluents using a filter photometer, is
0.05 mg nitrite nitrogen (9). In this study the standard deviation of
12 identical samples was 1.6 percent for a nitrite nitrogen concentration
of 1 .9 mg/1.
Nitrate Nitrogen. Nitrate nitrogen is probably the most difficult of the
nitrogen tests and was determined by the brucine method as described by
Standard Methods (10, p. 461, 13th edition). Initially, sample clarifi-
cation was attempted using activated carbon, but was later abandoned
because the small sample used did not require clarification and also some
nitrate was removed by adsorption on the carbon. Standard Methods
(10, p. 464) lists a 15.4 percent standard deviation at 5 mg/1 nitrate
nitrogen. In this study the standard deviation of 12 identical samples
was 10 percent for a nitrate nitrogen concentration of 7 mg/1.
pH. The pH of each sample was measured within about ten minutes of its
withdrawal in order to minimize pH changes caused by the loss of dissolved
carbon dioxide. A Beckman Model G portable battery powered pH meter
equipped with a glass electrode was used to make field measurements. The
normal range of accuracy of this procedure is about +0.1 pH unit (9).
Alkalinity. Sample alkalinity was determined by titration with sulfuric
acid to an endpoint at pH 4.3 as measured by an on-line Beckman pH meter
employing a glass electrode. A precision of + 1 mg/1 and an accuracy of
+ 3 mg/1, expressed as CaCOo, can be achieved in the range of 10 to 500
mg/1 (9). Since normal pH levels were less than 8.3 the total alkalinity
was composed almost entirely of bicarbonates.
Dissolved Oxygen. The Winkler azide modification of the iodometric
method was used to determine dissolved oxygen concentration. The method
was modified for the high dissolved oxygen concentrations used in this
29
-------
study as described on page 413 of Standard Methods (9). For secondary
effluents a standard deviation of about 0.06 mg/1 is indicated (9).
Temperature. A mercury filled thermometer was used for this determina-
tion. The temperature was expressed to the nearest degree celsius.
Suspended Solids. Each sample was filtered through a 4.25 cm Whatman,
grade GF/C, glass fiber filter pad for a suspended solids determination
as described by Wycoff (11). A precision of 11.2 percent was reported
for activated sludge effluent and 5 percent for mixed liquor analyses.
These values included sampling and weighing errors. Blank pads were
used for corrections in filter moisture content and fiber content.
Biochemical Oxygen Demand. Sample BOD was determined as described on page
415 of Standard Methods (9). Samples were treated with sulfuric acid to
inhibit nitrifying organisms and then neutralized (12, p. 399)- A pH of
2 was maintained for 30 minutes and then the samples were raised to pH 7
with sodium hydroxide. The dilution water was seeded with settled raw
sewage. Seed corrections were computed from the blanks because of the
small errors introduced compared to the overall test accuracy. When
necessary, samples with high dissolved oxygen concentration were aerated
to lower the oxygen content to air saturation. There is no standard
against which the accuracy of the BOD test can be measured. The standard
deviation of the results of 34 laboratories was 17 percent using a glucose-
glutamic acid mixture. The precision obtained by a single analyst in
his own laboratory was + 5 percent (10).
Chemical Oxygen Demand. The COD of each sample was determined by the
dichromate reflux method (9, p. 510). Silver sulfate was used as a
catalyst and 0.4 grams of mercuric sulfate was used to complex the
chlorides in the samples. The reported average standard deviation using
reagent grade glucose is + 8.2 percent. For most organic compounds 95
to 100 percent oxidation can be obtained based on the theoretical oxygen
demand (9).
Rhodamine Dye Concentration. A Beckman DB spectrophotometer (550 mu) was
used for this measurement for tracer studies. The use of a high concen-
tration of this dye allowed visual observations of short-circuiting in
the filter. It has been reported that a standard deviation of 1 to 2
percent is normal for absorbance measurements between 0.15 and 1.0 (13).
This range of absorbance is the same as a transmittance range of 10 to
71 percent. In this study the standard deviation was about 2 to 5 per-
cent for a transmittance range of 35 to 88 percent.
Analytical Errors. The systematic and analytical errors associated with
the laboratory measurements were considered to be within the range of
values published in Standard Methods (9 and 10). When non-standard but
published analyses were used the variation was considered to be equal
to that reported by the author of the test. Other systematic and ana-
lytical errors were calculated as necessary for this study. A summary of
the variations which could be expected for the analyses is given in Table 5
30
-------
TABLE 5
SUMMARY OF ANALYTICAL ERRORS
Measuremnt
Organic Nitrogen
Ammonia Nitrogen
Nitrite Nitrogen
Nitrate Nitrogen
PH
Alkalinity
Dissolved Oxygen
Termperature
Suspended Solids
Biochemical Oxygen
Demand
Chemical Oxygen
Demand
Rhodamine Dye
Method
Kjeldahl Method
Direct Nessleri-
zation
Naphthylamine-
hydrocnloride
Sulfanilic Acid
Brucine Method
Glass Electrode
V°4
Titration
Azide Winkler High DO
Hg-celsius
Thermometer
Glass Fiber Filter
BOD at 20 °C
5
Dichromate +
HgS04+ AgS04
Beckman DB
Spectrophotometer
Recovery
Q7 S-Qft I
J ( *j »^ tj c
97-c
J ( »
95-100/a
Precision
+ 0.03 mg/1
+ 0.001 mg
+2-5/0
Instrumental
+ 0.05 mg
+ 15.4/o
+ 10
+0.1 pH Units
+ 1 mg/1
± 1 mg/1
+ 0.23 mg/1
+ 1 °C
+ 11 .2/o
+ 5/o
Reference
Standard Methods (9)
Standard Methods (9)
This Study
Standard Methods (9)
This Study
Standard Methods (10)
13th Edition
This Study
Standard Methods (9)
Standard Methods (9)
This Study
Standard Methods (9)
Standard Methods (9)
Wycoff (11)
Standard Methods (9)
13th Edition
Standard Methods (9)
+ 1-2/o Skoog & West (13)
(10-71/0 Transmit.)
+ 2-5/o This Study
(35-88/0 Transmit.)
-------
SECTION VI
RESULTS OF FIELD STUDIES
This Section is divided into five parts. First a description is given
of the characteristics of the Union Sanitary District wastewater effluent
that was treated in the submerged filter pilot plant. The second and
third parts present a summary of the data collected from both the pre-
oxygenation filter with recycle and the bubble oxygenation filter. The
fourth part contains data to illustrate how the two filters operated
over a 24-hour period during which the waste characteristics varied
considerably. Finally, a brief discussion of the characteristics of the
various effluent nitrogen forms is given. Detailed data from operation
of the filters is given in the Appendices.
Characteristics of the Influent Wastewater
The field submerged filter apparatus was operated at the Union Sanitary
District Plant No. 3 located in Union City, California. During the period
of the study the activated sludge process at this plant was operated at
an average process loading of approximately 0.43 Ibs of BOD5 per Ib of
mixed liquor volatile solids (MLVS) with a range of 0.27 to 1.0. The
measured quality of the effluent from the final settling tank is shown
in Table 6. The lower typical concentrations of organic nitrogen, BOD,
COD, suspended solids and grease prevailed at the beginning of the study
and changed to the higher typical values during the latter half of the
study. These values are representative of a great majority of the data,
while the high and low values listed in other columns, represent extreme
measurements. More detailed data can be found in Appendix A.
The characteristics of the effluent waste from the wastewater treatment
plant was influenced by changes in the industrial waste contributory to
it. Approximately 15 to 20 percent of the influent flow was from indus-
trial sources. The principle contributing industries are producers of
aluminum cans and sash, cast iron pipe, chain and detergents. Also,
important industrial services include an industrial laundry and a meat
packing plant. Potential operational problems can be associated with
Al+++} Fe"H-, acids or alkalies, detergents and grease. The A1+++ and/or
Fe"^" were suggested as the cause of problems in the activated sludge
process in August and September, during the middle and latter part of
this study. Foaming tended to occur in any turbulent area following the
activated sludge process (including the oxygenator of the preoxygenation
filter),
Preoxygenation Filter With Recycle
The preoxygenation'filter was started on May 4, 1971. After thirteen
days of checking the system's mechanical operation, seed was added from
one of the laboratory nitrifying filters. The field filter was operated
at a 60 minute detention time. Between 'the 30th and 37th day there was
33
-------
TABLE 6
TYPICAL CHARACTERISTICS OF TREATED EFFLUENT
FROM
Parameter
NiL-N
NO"-N
LJ
NO"-N
Org-N
DO
BOD
COD
Suspended Solids
Grease
pH (units)
UNION SANITARY DISTRICT
Typical (mg/1) Low
14-18
0.02-0.10
0.05-0.15
4.0-8.0
0.5-0.8
25-56
100-150
20-69
2-12
7.3-7.6
PLANT NO.
(mg/1)*
9
0.00
0.00
1 .8
0.0
10
75
10
-
6.7
Alkalinity (as CaCO_) 320-350 200
Temperature (°C)
20-25
16
3
High (mg/1)*
25
0.20
0.23
8.8
1 .5
90
235
140
-
7.9
470
31
Units are mg/1 unless otherwise specified.
-------
a significant increase in efficiency of ammonia nitrogen removal (Figure
8). By the 66th day, 90 percent and greater ammonia nitrogen removal
was obtained consistently. During this start-up period backwashing was
performed twice per week at a rate of 6 to 20 gal/ft^/min (usually 6 gal/
ft^/min). See Appendix B for a summary and Appendix C for detailed data
at various detention times.
Filter Performance During Steady State Operation. In general the pre-
oxygenation filter was operated with a total flow rate (influent waste-
water plus recycle) through the filter varying from 0.82 to 1 .29 gal/ft^/
min. The recycle ratio varied from 2.0 to 3-0.
Nitrogen Forms. Once an optimum degree of treatment was reached it
remained fairly constant. The average percentage of ammonia nitrogen
removal obtained at three different detention times is shown in Table 7.
In the temperature range of 21 to 27 °C, 90 to 96 percent removal was
obtained with a 60 minute detention time. The possible effect of temper-
ature variations was overshadowed by variations in the suspended solids
concentration and/or in the nitrifying bacteria population in the filter.
As the detention time was increased from 30 to 60 minutes the removal
efficiency became more consistent.
Typical concentrations of the different nitrogen forms in the filter
influent and effluent are shown in Table 8. Errors in accuracy of the
nitrogen balance between influent and effluent was most likely caused by
errors in the nitrate test. At a detention time of 40 minutes the back-
wash rate was raised to 20 to 40 gal/ft^/min. This apparently caused the
nitrite nitrogen concentration in the filter effluent to rise. The
Nitrobacter population seemed to be more hindered by backwashing than the
Nitrosomonas population.
After the percent removal of ammonia nitrogen was established at a 60
minute detention time, a study was undertaken to observe how the various
nitrogen forms changed with depth in the filter (Figure 9). A more
detailed view of the ammonia nitrogen, nitrite nitrogen, and dissolved
oxygen changes with depth is shown in Figure 10. Because of the high
recycle ratio and low ammonia nitrogen in the activated sludge plant
effluent, the influent ammonia nitrogen concentration (2.84 mg/1) to the
filter was quite low. Some suspended organic nitrogen removal occurred
as suspended solids were removed in the bottom (influent end) of the
filter. The dissolved oxygen consumption paralleled the ammonia nitrogen
removal well (Figure 10). There was an immediate ammonia nitrogen oxida-
tion at the influent end of the filter where NHo-N concentration was
highest, as predicted by kinetic considerations. The decrease in the
rate of ammonia oxidation with height in the filter results from the
decreasing substrate concentration and the particular way in which the
filter was packed with biological solids. In the bottom half of the filter
the rate of nitrite oxidation was equal to the rate of ammonia oxida-
tion. In the top half of the filter the rate of ammonium nitrogen oxida-
tion fell below the rate of nitrite nitrogen oxidation.
35
-------
LX>
05
100
80
I 60
E
-------
TABLE 7
AMM3NIA NITROGEN REMDVAL IN THE PREOXYGENATION FILTER
Detention Recycle
Time(min)O) Ratio
Number of Number of
Days Operation Samples
60
40
30
2.75
3.0
2.0 & 3-0
40
27
62
10
18
Influent
Effluent
NH_-N(mg/l) m,-N(mg/l)
14.3 +2.6
19.6 +4.2
15.2 +3.6
1 .0 +0.4
5.6 +2.6
6.9 +3.1
Percent
Removal
93 ±3.1
71 +10.8
55 +15.7
TABLE 8
TYPICAL INFLUENT AND EFFLUENT NITROGEN CONCENTRATIONS
IN THE PREOXYGENATION FILTER
Detention, x Organic-N(mg/l) NH^-N(rag/l) NO~-N(mg/l NO~-N(mg/l) Total-N (mg/1)
Time(min) ^ ' Influent
60 3.6
40
30 5.7
Effluent Influent Effluent Influent Effluent Influent Effluent Influent Effluent
1.5 14.3 1.0 0.05 0.6 0.1 15.9 18.0 19.0
19.6 5.6 0.05 4.1 - 6.9 -
2.5 15.2 6.9 0.04 1.7 0.1 6.0 21.0 17.1
(1) Based on the filter void volume and the raw wastewater flow rate.
(2) Recycle Ratio = recycle flow rate/wastewater flow rate.
-------
24
20
o>
E
o
o
k.
c
0)
o
c
o
o
16
12
o>
o
t: 8
0
~i r
N0
-o-
-D-
ORG -N
NH3~N
0
12 18 24
Filter Height (in.)
30
36
Figure 9. Nitrogen profile through filter (preoxygenation with recycle of 2.75;
60 minute detention time; influent NH3~N cone, of 10.6 mg/1).
38
-------
36
1 r
-i 1 r
Dissolved Oxygen
2E
0>
o
E
12 18 24
Filter Height (in.)
30
36
Figure 10. Profile of dissolved oxygen, ammonia, and nitrite in
the preoxygenation filter (60 minute detention time).
-------
It should be noted that the standard deviation of the total nitrogen
balance for this specific test was + 5 percent. Considering the pre-
cision of each of the nitrogen tests a 10 to 15 percent error in the
total nitrogen balance is easily possible,. Loss of nitrogen by deni-
trification or suspended solids removal did not appear significant,
at least within the analytical error of nitrogen analysis.
BOD, GOD and Suspended Solids. The reductions in BOD, COD and suspended
solids through the filter are listed in Tables 9, 10, and 11, respec-
tively. The 60 minute detention time resulted in a 76 to 96 percent
reduction in BODj a 45 to 57 percent reduction in CODj and an 81 to 93
percent reduction in suspended solids. Change in detention time did
not affect percent BOD reduction as greatly as it did the ammonia nitro-
gen removal. The suspended solids were removed quite well, apparently
due to the quiescent conditions in the filter. Most likely straining
and adhesion were important mechanisms of solids removal.
Oxygenation. The oxygenator routinely attained 60 to 87 percent oxygen
saturation in the wastewater with oxygen transfer efficiencies varying
from 1.2 to 4.0 percent. This transfer calculation was based on the
difference in the dissolved oxygen between the oxygenator influent
(influent waste plus recycled effluent) and the oxygenator effluent.
The oxygenator influent, DO^, was calculated from the measured influent
untreated wastewater dissolved oxygen concentration, DOW, and the mea-
sured filter effluent dissolved oxygen concentration, DO . The oxygena-
tor effluent (equivalent to the dissolved oxygen of the filter influent)
was measured routinely. The efficiency was calculated by multiplying
100 times the ratio of the total pounds of oxygen transferred per day
by the oxygenator to the total pounds of oxygen drawn out of a cylinder
per day. This low transfer efficiency was due to the oxygenator design
and operation. Much higher transfer efficiencies could, without a doubt,
be obtained if designed for this purpose.'
pH and Alkalinity. The influent always had a high alkalinity and the
pH through the filter typically varied between 7.4 and 7.1. The ratio
of change in alkalinity to change in ammonia nitrogen concentration is
theoretically 7-13 and during this study the measured ratio averaged
8.0 at a 60 minute detention time and approximately 6.7 at a 30 and 40
minute detention time.
Clogging and Short-circuiting. The filter was operated at a 60 minute
detention time for three and one-half months and was backwashed at 6 to
20 gal/ft /min twice a week. The lower backwashing rate was used most
of the time. During the third month a dye study was performed to deter-
mine the extent of clogging and short-circuiting. At this time the
recycle ratio was 2.62 to 1 so that the single pass detention time in
the filter itself was 16.6 minutes.
Rhodamine dye was injected as a 15 second pulse into the influent line
of the filter on two separate occasions, once just before backwashing
40
-------
TABLE 9
BOD REMOVAL IN THE PREOXYGENATION
Detention. .
Time(minr2'
60
40
30
Number of
Samples
4
2
3
Influent
BOD(mg/l)
35 +6
38
37
TABLE 10
Effluent
BOD(mg/l)
5 ±3
3.4
9.6
COD REMDVAL IN THE PREOXYGENATION
Detention, >
Time(minr2'
60
40
30
Number of
S amp 1 es
4
2
4
Influent
COD(mg/l)
104 +15
113
124
TABLE 11
SUSPENDED SOLIDS REMDVAL
Detention/p%
Time(min)^ '
60
40
30
Number of
Samples
4
3
6
Influent
S.S.(mg/l)
27 ±3
38
25 +5
Effluent
COD(mg/l)
51 +12
61
54
FILTER^1 '
Percent Removal
BOD
86 +10
91
74
FILTER
Percent Removal
BOD
51 +6
46
56
IN THE PREOXYGENATION FILTER
Effluent
S.S.(ms/l)
3.5 +4
6.6
6.5 +3
Percent Removal
S.S.
87 +6
83
74 +4
(1) No standard deviation was calculated on data based on less
than four samples.
(2) Based on raw wastewater flowrdteand filter void volume.
41
-------
(2 days after the previous backwash) and once just after backwashing
(Figure 11). The single pass theoretical detention time in the filter
including entrance and exit volumes was 20.8 minutes for this dye study.
As can be seen, there was less short-circuiting in the filter after
backwashing due to less suspended solids in the filter. The dye could
be visually observed running up the sides of the filter. In the before-
backwash test it appeared that about 1/4 of the dye had reached the fil-
ter exit after 6 minutes of elapsed time. For the same amount of dye
the time elapsed in the after-backwash test was 9 minutes. The mean
detention times for the before-backwash and the after-backwash tests
were 10 and 14 minutes, respectively.
The filter had a column to rock diameter ratio of 5.5 to 1, which was not
large enough to completely eliminate wall effects and short-circuiting
even though wall dispersion rings were provided. This short-circuiting
could be especially significant at short detention times. In Table 7 it
was reported that a 55 percent ammonia nitrogen removal was obtained
at a 30 minute detention time. There was one 3 week period during which
the ammonia nitrogen removal at this detention time averaged 71 percent,
but later it decreased. It is possible that the suspended solids in the
filter were arranged to give less short-circuiting during this particular
period of time. Thus it is possible that slightly better efficiencies
could be obtained with a filter with a larger column diameter.
Rate of Suspended Solids Accumulation in the Filter. The rate at which
suspended solids accumulate within the filter is an important engineering
consideration. Solids accumulation can lead to clogging. Further, in
order to prevent clogging, the suspended solids will have to be removed
periodically for subsequent disposal. An estimate of the quantity which
will be removed is important for the design of the disposal facilities.
Suspended solids accumulation will result from various factors. First,
some accumulation will result from suspended solids in the influent which
are removed within the filter. Some of that removed will be oxidized by
biological action within the filter so that the accumulation from this
source should be something less than the quantity of influent solids
removed. Second, some biological suspended solids will be produced with-
in the filter from utilization of soluble wastewater organics by micro-
organisms within the filter (0.1 to 0.4 mg produced per mg soluble COD
removed, depending upon the detention time of the cells within the filter).
Finally, some biological suspended solids will result from nitrogen oxi-
dation (0.1 to 0.3 mg per mg NHo-N oxidized, also depending upon the re-
tention time of organisms in the filter). Estimates of anticipated sus-
pended solids accumulation could be made on this basis, but it was desired
to make some measurements in order to see if firmer figures could be
obtained. This proved to be a difficult task because of varying waste-
water characteristics and the inability to directly measure the suspended
solids concentration within the filter.
Three approaches were used in an attempt to quantify the rate of accmu-
lation of suspended solids in the preoxygenation filter. They involved
a suspended solids balance; a COD, nitrogen and oxygen balance; and last
42
-------
Time After Dye Injection (min.)
04 8 12 16 20 24 28 32 36 40
To = 20.8 min.
Before Backwash (C0 = 6.42)
Before Backwash Mean - 10 min.
After Backwash Mean - 14 min
After Backwash (C0 = 6.42)
0.2 -
0.0
0.0 0.5
1.0
1.5
2.0
2.5
Figure 11. Rhodamine dye tracer study of the preoxgenation filter.
43
-------
an approach which considered suspended solids removal and oxidation, and
suspended solids production due to both nitrification and the oxidation
of organic matter. During the start-up period many of the influent sus-
pended solids will be removed and will remain in the filter for a long
period of time. Later, after reasonably steady-state conditions develop,
the rate at which suspended solids are leaving the filter should equal
the rate at which they are accumulating.
The first approach was to make a simple balance based upon the differ-
ence between suspended solids entering and leaving the filter (Table 12).
The suspended solids accumulation was assumed to be equal to the differ-
ence between the influent and effluent suspended solids. The solids
removed during backwashing were collected every 2 to 4 days for a total
of 10 times during a 29-day period of operation. The average quantity
of suspended solids removed by backwashing was 1.4 grams/day. This
represents 31 percent of the 4.7 grams/day removed during waste passage
through the filter. Thus solids were either increasing in concentration
in the filter or else they were being oxidized. The former was at least
partially the reason because the filter became clogged with suspended
solids within 3 weeks after this data was collected.
The above approach ignored all the suspended solids removing, oxidizing
and forming reactions taking place within the filter. A second approach
was tried that takes these processes into consideration. It was based
on a COD, nitrogen and oxygen balance. The COD of 1 mg/1 of biological
suspended solids commonly has been found to be approximately 1.4 mg/1.
Most of the COD removal (60 to 70 percent) was due to the suspended
solids removal in the filter. The actual oxygen used in the filter was
consumed by both nitrification and the oxidation of organic matter (COD).
If the oxygen demand of the oxidized ammonia nitrogen is subtracted from
the total oxygen used within the filter, the difference equals the quan-
tity of COD oxidized. The quantity of COD oxidized was very low con-
sidering the amount of COD removed (Table 13} Column H). This is in
part due to the low dissolved oxygen concentration within the bacterial
solids in the filter. More discussion on the degree of carbonaceous
oxidation appears in the next section in relation to the total oxygen
demand in the filter.
It was assumed that total COD removal minus the COD oxidized is a mea-
sure of suspended solids accumulation. By dividing the unoxidized but
removed COD by 1.4 mg COD/mg S.S. the actual suspended solids accumula-
tion in the filter could be calculated. Where COD data was available
the above calculations were performed at the various detention times.
Note that the influent COD analyses were somewhat high because of excess
suspended solids collection in the influent sample, therefore, this error
was subtracted from the above calculations (Table 13). This error was
monitored by comparing the data from the influent samples from the pro-
ject and the data from the effluent sampler at the Union Sanitary Dis-
trict Plant No. 3- The overall suspended solids accumulation rate was
27 + 9.5 mg/1 (based on the influent wastewater flow rate). Theoreti-
cally this was a logical approach but the small amount of COD data and
44
-------
TABLE 12
SUSPENDED SOLIDS BALANCE IN THE PREOXYGENATION FILTER
01
Average or
Range:
Number of
Samples :
Standard
Deviation:
Days Suspended Solids-mg/1
After ..
Start-up Influent Effluent Differences
95-125 27 9(1) 18
28 3
+7.6
(30 minute detention time)
Estimated S. S.
Accumulated
g/day g/liter-day
4.7
+2.0
0.86
Wasted S. S.
During Back-
washing (g/d)
1 .4
10
Percentage
Removed by
Backwashing
31
(1 ) Average from three samplesj assumed to be constant.
-------
en
TABLE 13
SUSPENDED SOLIDS ACCUMULATION IN THE PREOXYGENATION FILTER
BASED ON A COD, NITROGEN AND OXYGEN BALANCE
Number of Detention
Samples Time(min)
(A) (B)
4 60
1 40
4 30
(1 ) Suspended
C /^ 1 -I /4 r.
Total
Days DO
After Used
Start-up mg/1
(C) (D)
57-70 75.2
183 56.8
105-125 61.6
COD Removed - [DO
Calculated Total Total Estimated S. S. Accumulation
Oxygen Demand COD COD (Based on Influent Waste-
from Nitrifi- Removed Oxidized water Flow) (1)
cation mg/1 mg/l(2) mg/1 mg/1 g/day
(E) (F) (G) (H)
64.9 53.5 10.3 31 ±12.1 4.1
43.4 53.4 13.4 29 5.7
45.3 48.6 16.3 23 +6.6 6.0
Used - (4.57(NH+-N oxidized) - 1.14 (NX>2-N)Eff )]
g/liter-day(3)
0.75
1 .0
1 .1
Accumulatior
1.4 mg COD/mg S. S.
(2) The suspended solids error was subtracted from the influent CODj the source of
the error was the influent composite sampler (checked with Union Sanitary District
s amp1er).
COD Oxid(corrected) = COD Oxid(actual data) - (excess S.S.)(1.4 mg COD/mg S.S.)
(3) In filter void volume.
-------
the fairly high standard deviation reduced its accuracy. However, the
accumulation in the filter in grams/day was surprisingly close when
comparing the different methods used in Tables 14 and 15.
The Third approach to finding the suspended solids accumulation rate was
to directly consider influent suspended solids which are removed by the
filter plus an estimate of suspended solids produced from nitrification
and soluble COD oxidation (Table 14). Then loss of suspended solids
within the filter through oxidation is estimated as it was in Column G
of Table 13. The first sources of suspended solids are the actual in-
fluent suspended solids removed by the filter. This can be determined
as by the first approach. The second and third sources of suspended
solids are the organisms produced during the removal of soluble COD and
during nitrification. The effluent suspended solids data are all average
values, but are fairly representative. The most inaccurate data is the
change in soluble COD and concentration of COD oxidized. In many cases
these data were simply estimated, but the relative influence of these
changes was small compared with the suspended solids contributing fac-
tors .
The influent suspended solids concentration was high during some months
of filter operation (Table 14). Therefore, the suspended solids accumu-
lation rate was also high. This resulted in a low percentage of nitri-
fying bacteria in the suspended solids within the filter. This is in
marked contrast to the situation in the laboratory study where there was
no influent suspended solids and the suspended solids within the filter
consisted mainly of nitrifying bacteria. Because of the much lower
estimated percentage of nitrifying bacteria within the filter in the
field study, the efficiency of nitrification under comparable conditions
of detention time and influent ammonia nitrogen concentration should be
much lower than obtained in the laboratory. This would appear to be a
very important parameter in explaining the results obtained.
All three of the approaches used to estimate suspended solids accumula-
tion within the filter have sources of error. However, there is a
general consistency between the estimates by the three different methods.
The data contained in Table 14 suggest that suspended solids accumulation
from dissolved COD removal and nitrification (columns G and I) is a smaller
but still significant portion of the suspended solids accumulation when
compared with accumulation from suspended solids in the influent (column D).
The third method described (Table 14) is perhaps the best to use in esti-
mating suspended solid accumulations in filters.
Oxygen Requirements for Carbonaceous Oxidation. As already suggested some
oxygen was required for oxidation of organic matter entering the filter
as well as for nitrification. A correlation between BOD5 removal by
the filter and oxygen demand above that required for nitrification is
shown in Table 15. Much of the influent BOD was in the form of sus-
pended solids. The oxygen consumed by the oxidation of organic matter
47
-------
SUSPENDED SOLIDS (S .S . ) ACCUMtLmDN BASED ON TRAPPED S.S. AND S.S.
PRODUCTION DUE TO NITRIFICATION AND THE OXIDATION OF ORGANIC MATTER
Detention
Time (min)
(A)
60
60
60
40
30
30
30
Month
(B)
June
July
Jan.
Mid-Oct,
to
Mid-Nov.
Aug.
Sept.
Dec.
Days
After
Start-up
(c)
28-57
58-88
243-274
164-191
80-110
111-140
212-233
Average
Monthly
Inf. S. S.
Minus Eff.
S.S. (mg/l)(l)
(E)
18
17
59
45
25
20
46
COD (mg/1)
Soluble
Reduction
(E)
20(2)
20(2)
35(2)
20
26
26
34(2)
Oxida-
tion
(F)
10
10
10
13
16
16
16
Resulting
S.S. Produc-
tion (3)
(G)
7
7
18
5
7
7
13
Nitrification (mg/1)
NH^-N
Oxidized
(H)
14.3
14.8
18.7
12.8
7.3
8.1
5.0
Resulting
S.S. Produc-
tion (4)
(I)
2.5
2.6
3.3
2.2
1.3
1 .4
0.9
Total S. S.
(mg/1) (5)
(J)
28
27
80
52
33
28
60
Accumilation . . r .
,, . , Bacterial
g/liter-day Solidg (6)
(K)
0.67 9
0.65 10
1.9 4
1 .9 4
1.6 4
1.3 5
2.9 1.5
(l) Influent data from Appendix Aj effluent data assumed to be 5 mg/1 at 40 and 60 minute
detention time; and 9 mg/1 at a 30 minute detention time.
(2) Estimated from influent S. S. and BOD data.
(3) (E-F)/1.42.
(4) 0.15 X (NH^-N oxidized).
(5) J = D + G + I.
(6) K = I X 100/J.
-------
TABLE 15
CORRELATION BETWEEN CARBONACEOUS OXYGEN DEMAND AND BOD,, REMDVAL
Detention
Time(min)
(A)
60
40
30
Overall
sr« rer Ao2«> ABO^:
Start-up Samples mg/1 mg/1
(B) (C) (D) (E)
48-90 6 26+11 34+6
164-191 3 14 42
98-218 10 20 +10 32 +6
- -
D
ABOD5
(F)
0.78 +0.28
0.34 +0.12
0.62 +0.28
0.63 +0.28
(1 ) Oxygen consumed to oxidize organic matter =
Total 0 Used - [4.57(NH+-N oxidized) - 1.14(NO~-N)]
(2) Influent BOD - Effluent BOD .
D ^
49
-------
was obtained by subtracting the calculated nitrification oxygen demand
from the total oxygen consumed within the filter. Somewhat surprisingly,
the carbonaceous oxygen demand within the filter was less than the BODg
removed. The ratio of these two quantities averaged 0.63 + 0.28 at all
detention times. At a 60 minute detention time this fraction was 0.78
+0.28. Thus it appears that when suspended solids are detained.within
The filter for periods of 10 to 25 days they are not as completely oxi-
dized as when they are held in a more diluted form in a BOD bottle for
only five days.
Effects of Anaerobic and Idle Aerobic Conditions. The preoxygenation
filter rarely became completely devoid of oxygen because the turbine
blades in the oxygenator always ran and thus always supplied some aera-
tion even during times when pure oxygen was not flowing into the oxygen-
ator. During periods when insufficient dissolved oxygen was supplied,
nitrification decreased to negligible values while the oxidation of car-
bonaceous BOD consumed the available oxygen. At times of insufficient
dissolved oxygen a few black areas developed within the filter. It is
difficult to make any quantitative statements about filter recovery
after such periods. One episode is illustrated by Figure 12. During
the first 20 days shown the filter was operated at a 30 minute detention
time. Unknown problems (perhaps high influent suspended solids or toxi-
city) arose and the efficiency of ammonia nitrogen removal decreased.
On the 22nd day the filter was changed to operate at a 60 minute deten-
tion time and samples were collected during the next 14 days. On about
the 32nd or 33rd day the filter oxygen supply failed and the filter
became partially anaerobic for 1 or 2 days. Recovery appeared rapid
after the oxygen supply was restored. Similar partially anaerobic con-
ditions occurred at other times early in the study and the filter never
seemed to be seriously affected for any prolonged length of time.
A planned study to determine the effect of four days without feed (under
aerobic conditions with recycle and oxygenation) was started on day 51
(Figure 12). This four day idle period had little effect on the effi-
ciency of ammonia nitrogen removal after 24 hours of operation. Point
E (Figure 12) represents a composite sample collected during the 24 hour
period after the influent feed was started. Point F represents a grab
sample collected at the end of the above 24 hour period. It appears
that the filter recovered immediately. It must be noted that during the
35th to the 70th day the influent suspended solids and BOD5 were extreme-
ly high. Thus the expected maximum ammonia nitrogen removal efficiency
was only 70 to 85 percent (not 93 percent as under more favorable condi-
tions). Short anaerobic periods or periods without waste addition do
not appear to seriously hamper the operation of the preoxygenation fil-
ters .
Bubble Oxygenation Filter
Filter Start-up and Seeding. This filter was started on August 11, 1971.
After a 5-day initiation period, a refrigerated nitrification seed was
50
-------
100
80
§60
E
0)
Of
en
40
E
E
20
1 I I I I I II I T
30 minute detention time
vO
8
O
60 minute detention time
O
partially Anaerobic
(1-2 days)
A
Aerobic no-feed
(4 days )
i / \ i
j i
16 24
32 40
Days of Operation
48 56 64 72
Figure 12» Recovery of Preoxygenation Filter from anaerobic and idle aerobic conditions.
-------
added to the filter. The filter was initially operated at a 60 minute
detention time. Between the 21st and 30th day of operation there was a
large increase in efficiency of ammonia nitrogen removal (Figure 13)
By the 70th day about 90 percent removal was maintained consistently.
During this start-up period very little backwashing was required since
most of the excess solids were carried out with the effluent from the
filter. See Appendix B for a data summary and Appendix C for detailed
data for different detention times.
Filter Performance During Steady-State Operation. In general the influ-
ent flow rate to the filter varied between 0.22 to 0.44 gal/ft^/min.
Nitrogen Forms. After steady-state conditions developed, data was col-
lected to ascertain ammonia nitrogen removal at a 60 minute detention
time (Table 16). A 87 to 95 percent removal was attained with tempera-
ture varying between 16 and 30 °C. Some effect of temperature on effi-
ciency was evident during the start-up phase of operation. However, as
the suspended solids concentration increased within the filter, tempera-
ture effects were no longer easily distinguishable.
Typical nitrogen influent and effluent data is depected in Table 17 for
a 60 minute detention time. The rising bubbles of oxygen in the filter
tended to maintain a state of turbulence. This turbulence caused a
variable and relatively high concentration of suspended solids to be
present, in the effluent.
Samples were collected at a 30 minute detention time but the data was
not meaningful when compared to the data in Table 16. The efficiency
of ammonia nitrogen removal varied between 0-59 percent (Appendix G)«
The data was not representative of normal operation because of high in-
fluent suspended solids and many operational problems.
Samples were collected at various filter heights to determine the reactor
hydraulics and ammonia nitrogen removal characteristics (Figure 14).
Less than one-half of the influent ammonia nitrogen remained in the sam-
ple taken 3 inches from the filter bottom. The alkalinity and ammonia
nitrogen concentration decreased together while the dissolved oxygen con-
centration increase resulted from the continuous oxygen transfer during the
rise of the oxygen bubbles throughout the height of the filter. The pro-
file concentration in the field unit were very similar to those of the
laboratory filter.
BOD, GOD and Suspended Solids. The suspended solids wasting aspect of
this filter caused lower percent removals of BOD,, COD, and suspended
solids than obtained with the preoxygenation filter. At a 60 minute
detention time there was a 67 to 81 percent BOD removal^ from 41 to 59
percent COD removal, and from 8 to 88 percent suspended solids removal
(Table 18). At a detention time of 30 minutes removal of these consti-
tuents was lower.
52
-------
100
0
32
O
o
O
_L
_L
o
48 64 80
Days after Start-up
96
112
128
Figure 13. Percent ammonia removal versus time during start-up
(Bubble oxygenation system '- 60 minute detention time).
-------
TABLE 16
AMMONIA NITROGEN REMOVAL IN THE BUBBLE OXYGENATION FILTER
(60 minute detention time) (1 )
Percent
Number of Days Influent Effluent Removal
of Operation Number of ( /1} M N( /1} ^_N
(these samples) Samples 3 3 3
33 8 18.3 ±4.2 1.8+1.0 91+4.2
TABLE 17
TYPICAL INFLUENT AND EFFLUENT NITROGEN CONCENTRATIONS IN
THE BUBBLE OXYGENATION FILTER
(60 minute detention time) (1)
. AT, ,.» NEL-N(mg/l) NO~-N(mg/l) NO~-N(mg/l) ,«.-,/ ,^
Organic-N(mg/l) ^ v a/ ^ 2 ^ e' ' 3 \ &' / Total-N(mg/l)
Inf. Eff. Inf. Eff. Inf. Eff. Inf. Eff. Inf. Eff.
5(2) 2.2-4.7 18.3 1.8 0.0 0.4 0.0 18.3 23.3(2) 23.9(2)
TABLE 18
BOD, COD AND SUSPENDED SOLIDS REMOVAL IN THE BUBBLE OXYGENATION FILTER
Number of
Parameter Samples
BOD 5
BOD 2
COD 5
COD 2
S.S. 6
2
Detention
Time(min)(l )
60
30
60
30
60
30
Influent
37 +3
43
127 +18
137
30 +10
48
Effluent
(mg/1)
9.5 +3
25
63 +18
80
16+14
51
Percent
Removal
74 +7
41
50 +9
42
48 +40
"
(1) Based on filter void volume and untreated waste flow rate.
(2) Estimated due to a lack of data.
54
-------
320
6
12 18 24
Filter Height (in.)
36
Figure 14. Profile of DO, alkalinity, NHT-N, and NO -N concentrations
in the bubble oxygenation filter (60 minute detention time).
55
-------
Oxygenation. The oxygen transfer efficiency ranged from 1.5 to 5.0 per-
cent. This calculation was based on the amount of oxygen theoretically
required to oxidize the organic matter (BOD), ammonia nitrogen and ni-
trite nitrogen, and the effluent dissolved oxygen concentration. The
efficiency of oxygen transfer was calculated by multiplying 100 times
the ratio of the total oxygen used per day (theoretical for known NHf^-N
and carbonaceous oxidation) in the filter and the total oxygen discharged
in the effluent of the filter per day to the total oxygen bubbled into
the filter from the pure oxygen cylinder per day. These very low oxygen
transfer rates were caused by a short distance of bubble travel (approxi-
mately 40 inches), large bubble size, and most important the lack of a
recycle system for the oxygen. Future pilot plants should employ oxygen
recycling so that oxygen transfer under more realistic conditions can be
evaluated.
pH and Alkalinity. The ratio of decrease in alkalinity to the NH^-N
oxidized was 7.8 for a 60 minute detention time. This was about the same
as for the preoxygenation filter. Also, the pH changes were of the same
magnitude.
Clogging and Short-circuiting. This filter never clogged during a five-
month period of operation. It was partially drained (6 to 20 gal/ft2/inin)
once a week to prevent suspended solids accumulation in the base of the
filter.
Anaerobic and Idle Aerobic Conditions. The bubble oxygenation filter
accidently went without oxygen twice in a period of two months (Figure
15). The filter biological solids became very black during the second
anaerobic period. The period needed for recovery in both cases was
about three weeks. This was longer than the recovery period for the
preoxygenation filter. A possible reason for the long recovery period
was the loosening of attached organisms from the rock surface during the
anaerobic period and subsequent removal from the filter by the turbulence
of rising bubbles and the flowing waste. It should be noted that during
this time period the influent suspended solids and BOD were extremely
high so that expected maximum ammonia nitrogen removal efficiency was
only 40 to 50 percent.
There were also two idle aerobic periods. Both showed a complete recovery
within 24 hours. Point E represents a 24 composite starting immediately
after the start of the influent feed. Point F represents a grab sample
collected 24 hours after restarting of the influent feed.
Diurnal Variation in Operation
On two separate occasions 24 hour composite and grab samples (collected
every two hours) were taken of the influent and effluent to the preoxy-
genation filter and the bubble oxygenation filter (Figure 16). This
study was conducted to determine how each filter would react to the
normal variation in influent ammonia nitrogen concentration over a 24
hour period. The high effluent ammonia nitrogen concentration at the
56
-------
100
80
en
s
©
a:
©
£ 40
©
20
i r
O
^Anaerobic (
A i i i
Anaerobic (2~7 days)
O
O
(4 days)
6E
no-feed
(2 days)
\ /"Ai
0
8
16
24 32 40
Days of Operation
48
56
,64
72
Figure 15. Recovery of Bubble Oxygenation Filter from anaerobic and no feed
conditions (30 minute detention time).
-------
18 -
16
14
12
in
a
o>
E
o
E
E
10
8
0
T 1 1 1 1 r
Preoxygenation
Filter Influent
and Effluent
(8 p.m., 7/23/71
to 6 p.m.,7/24/71) /
-start
Influents
Bubble Oxygenation
Influent and
Effluent
(4 p.m., 11/23/71
to 2 p.m., 11/24/71)
restart
(11/2 hrs. after
backwashing)
Effluents
2 a.m. 6 a.m 10 a.m. 2 p.m. 6 p.m. 10 p.m.
Time of Day
Figure 16. Ammonia nitrogen variations over 24-hour periods,
58
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start of the bubble oxygenation sampling was caused by backwashing V-1/2
hours prior to the start of sampling. Discounting the affect of this
both filters averaged 93 percent ammonia nitrogen removal and both were
able to oxidize a 9.3 to 19.0 mg/1 range of influent ammonia nitrogen
with consistent results. It should also be noted that the influent
ammonia nitrogen concentrations were very similar over the 24-hour period
even though the two studies were made four months apart. The weakest and
strongest sewage with respect to ammonia nitrogen occurred at 10 a.m.
and 3 to 4 p.m, respectively. This corresponds to a flow time of 0.5 to
5 hours in the trunk line sewer and 3.5 to 8 hours through the principal
secondary treatment plant. More detailed analytical data can be found
in Appendix D.
Effluent Nitrogen Forms
While it was possible to obtain 90 percent removal of ammonium nitrogen
in the submerged filter, it would be much more difficult to meet a strict
effluent standard with respect to all unoxidized forms of nitrogen
(NH^-N, NOg-N and Organic-N). There was a concentration of 3.1 mg/1 and
4.3 mg/1 of total unoxidized nitrogen in the average effluent from the
preoxygenation and bubble oxygenation filters, respectively, when oper-
ated at a 60 minute detention time (Table 19). This difference between
the two filter systems is not meaningful because of inadequate data on
the bubble oxygenation system. In either case the soluble organic nitro-
gen equalled about 50 percent of the remaining unoxidized nitrogen.
This soluble organic nitrogen must be fairly refractory in form since it
was unaffected by two stages of biological treatment. Even if complete
inorganic nitrogen oxidation were achieved this soluble organic nitrogen
would remain in the final effluent. It is not known whether the soluble
organic nitrogen could stimulate algal growth, or whether the organics
with which it is associated would eventually be decomposed and the nitro-
gen released as NHo. Any proposed effluent standard for total nitrogen
should consider the presence of this soluble organic nitrogen and the
current limitation of methods for its removal. Research concerned with
the nature of the soluble organic nitrogen and methods for its removal
is needed.
59
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TABLE 19
EFFLUENT NITROGEN FORMS REMAINING AFTER NITRIFICATION
Effluent Nitrogen (mg/1)
Detention NH"!~-N NO~-N NO"-N Org-N Org-N , ,
Time(min) 4 2 3 Total Sol. Total"N
Preoxygenation Filter:
Average 60 1.0 0.6 15.9 1.5 - 19.5
No. of Samples - 88 8 8 8
Std. Deviation - +0.4 +0.4 + 3.0 +0.7 - + 2.8
Average 30 6.9 1.7 6.0 2.5 2.2 17.1
No. of Samples - 11 11 115 3
Std. Deviation - +3.1 +1.3 +2.8 +0.5
Bubble Oxygenation Filter:
Average 60 1.8 0.4 18.4 4.6 2.1 25.2
No. of Samples - 87 711
Std. Deviation - +1.0 +0.1 +3.8 - -
60
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SECTION VII
SUMMARY AND DISCUSSION
This section contains first a brief review of the important aspects of
submerged filter operation. Following this a comparison is made between
the results of the previous laboratory study and the field study. Next
a method of calculating the necessary recycle ratio for the preoxygena-
tion system is developed and demonstrated. Finally a brief discussion
is presented on the magnitude of the unoxidized nitrogen from which
remain after nitrification.
The unchlorinated effluent from a full scale 3 mgd activated sludge
plant was used as the influent of the field submerged rock filters.
This activated sludge plant influent flow consisted of 80 to 85 percent
domestic sewage.
Operating Results
Preoxygenation Filter With Recycle. At a 60 minute detention time during
the initial start-up period, a 90 percent or greater ammonia nitrogen
removal was consistently attained after 60 days of filter operation.
Normal steady state operation resulted in a 90 to 96 percent ammonia
nitrogen removal at temperatures ranging from 21 to 27 °C.
The submerged filter also acted as an excellent polishing device for
the activated sludge effluent. It accomplished an additional 75 to 95
percent reduction in BODi-j a 46 to 58 percent reduction in CODj and
an84 to 96 percent reduction in suspended solids.
Gravity backwashing twice per week a rate of 6 to 20 gal/ft^/min pre-
vented the filter from clogging over a 3-1/2 month period of operation
at a 60 minute detention time. These rates of backwashing were not
adequate to prevent clogging at the shorter detention times of 30 to
40 minutes.
Bubble Oxygenation Filter. At a 60 minute detention time during the
initial start-up period 90 percent ammonia nitrogen removal was
attained after 70 days of filter operation. Normal steady state opera-
tion resulted in an 87 to 95 percent ammonia nitrogen removal at temper-
atures ranging from 16 to 30 °C.
There was also a 67 to 87 percent reduction in BOD5, a 47 to 59 percent
reduction in COD; and an 8 to 88 percent reduction in suspended solids.
The tubulence caused by rising oxygen bubbles resulted in the contin-
uous discharge of a variable concentration of suspended solids to the
filter effluent. No clogging problems occurred with this filter during
a 6 month period of operation. There was a need, however, to waste
excess solids about once per week.
61
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Comparison Between the Preoxygenation and the Bubble Oxygenation Filter.
After 2 months of operation at 60 minute detention time the preoxygen-
ation filter was able to attain 93 ± 3 percent ammonia nitrogen removal
while the bubble oxygenation filter attained a 91 + 4 percent removal,
probably an insignificant difference. The preoxygenation filter was
slightly superior in BOD and COD removal and much better in suspended
solids removal.
Clogging was not a problem when either filter was operated for a 3-1/2
month period at a 60 minute detention time. During this time the pre-
oxygenation filter was backwashed by gravity draining at a rate of 6
to 20 gal/ft2/min (usually the lower rate) twice per week. There is a
possibility of clogging problems occurring with high influent BOD^
( > 50 mg/1) and suspended solids ( > 50 mg/1), or through operation
over longer periods of time. However, these potential problems most
likely could be prevented by daily gravity backwashing. At a 30 to 40
minute detention time gravity backwashing proved to be unsuccessful in
preventing clogging with the preoxygenation filter. However, clogging
was never a problem in the bubble oxygenation filter.
After a 2 day idle aerobic period both filters were able to obtain nor-
mal ammonia nitrogen removal efficiencies within a 24 hour period.
After the preoxygenation filter went partially anaerobic for 1 to 2 days
normal removal efficiencies were regained within a 2 week period. When
the bubble oxygenation filter went very anaerobic (black sludge) for at
least 2 days, normal operation was attained within 3 weeks. The pre-
oxygenation filter is superior to the bubble oxygenation filter in re-
covery from anaerobic conditions because there are no rising oxygen
bubbles to discharge bacterial solids which become loosened from the
stone surfaces under such conditions.
Both filters contained biological organisms typical in appearance to
those associated with the activated sludge process. Numerous nematodes
along with amoebae, rotifers, and stalked and free-swimming ciliate
protozoa were present.
Suspended Solids Accumulation in the Filter. The accumulation of sus-
pended solids in the filter is an important consideration as they must
be removed to prevent clogging and they also add a small but significant
quantity of sludge for subsequent disposal. Most of the influent sus-
pended solids are removed from the waste stream by the filter. Addi-
tional biological suspended solids are produced within the filter in
association with the biological oxidation of soluble wastewater organics
and nitrification. Also, a portion of the accumulated suspended solids
are oxidized within the filter.
There were three different approaches used to estimate the amount of
suspended solids accumulation in the preoxygenation filter. These
different methods all suggested that the suspended solids in the influ-
ent accounted for the major fraction of the accumulated suspended solids,
62
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However, formation of biological suspended solids from soluble organic
oxidation and nitrification resulted in the accumulation of 10 to 20
mg of volatile suspended solids per liter of waste, which is a quan-
tity worthy of consideration. Thus, for example, if the waste flow
rate were 10 mgd and the suspended solids in the influent to the
filter were 30 mg/1, and assuming 87 percent removal were obtained
by the filter, then the accumulation would equal 10(8.34) [0.87(30) +
15] or 35400 pounds per day. The value 15 is an estimate of the sus-
pended solids produced from soluble COD removal and nitrification.
Surprisingly, only a small fraction of the suspended solids removed
were oxidized in the filter. The efficiency of suspended solids cap-
ture was much less with the bubble oxygenation filter so that suspended
solids accumulation was much lower.
Comparison of the Results from the Field and Laboratory Studies
Preoxgenation Filter. A 90 percent ammonia nitrogen removal required a
57 minute detention time in the field study, but only a 27 minute deten-
tion time in the laboratory study (Figure 17). The curve representing
results from the laboratory study was generated using Equation 14 and
temperatures equivalent to the average field temperatures (22 and 25 C).
There are four reasons which can be given to explain the above differ-
ences in results. First, the actual detention time in the field filters
was shorter than the theoretical time because of a larger suspended
solids accumulation, which resulted in less void space and greater short-
circuiting of flow. Second, in the field study there was competition
and spatial interference between the nitrifying bacteria and the other
suspended solids which accumulated in the filter. It was estimated that
only about 10 percent or less of the suspended solids in the filter were
actually nitrifying bacteria during normal operating conditions at a 60
minute detention time in the field, while this fraction approached 100
percent in the laboratory study.
A third reason for lower efficiencies in the field study is the greater
wash-out rate of nitrifying bacteria (reduced biological solids reten-
tion time) due to the need to frequently remove accumulated suspended
solids from the filter in the field. A high wash-out rate was not neces-
sary in the laboratory because the influent contained no suspended solids.
A fourth possible factor (probably minor) is the slower diffusion rate of
oxygen and/or ammonia in secondary effluent as compared with tap water
(U).
Bubble Oxygenation Filter. A significantly longer detention time was also
required in the field than in the laboratory with this filter in order
to obtain the same degree of ammonia nitrogen removal (Table 20). At
a detention time of 60 minutes in the field a 91 + 4 percent ammonia
nitrogen removal was obtained while 95 percent removal was obtained in
the laboratory study. At shorter detention times the field filter lost
removal efficiency rapidly while the laboratory filter efficiency re-
mained reasonably high, very similar to the preoxygenation case.
63
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100
Laboratory Study Results
90
o
>
E
or
60
40
Field Study Results
With Standard Deviation
20
0
0
10
Figure 17.
20
40
50
30
Detention Time (min.)
Comparison between ammonia removal efficiencies obtained in the
laboratory and in the field studies with the preoxygenation filter.
60
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TABLE 20
COMPARISON OF LABORATORY AND FIELD RESULTS
(Bubble Oxygenation Filter)
Percent Removal NH-j-N
Detention Time (min)
30
60
Laboratory
89
95
Field
40-50 *
91
* Data Collected during the time
of high influent S.S.
Backwashing was never required in the laboratory study for this filter,
but was required in the field study to keep solids from building-up in
the base of the filter.
2
The required oxygen flow rate varied from O.OB to 0.125 cfm/ft in the
field study but was only 0.017 to 0.043 cfm/ft in the laboratory study.
Part of this difference was reflected in the additional 25 to 30 per-
cent oxygen demand by the organic matter in the field study influent.
Also, the efficiency of oxygen transfer tends to decrease as the level
of organic matter increases in the wastewater. In actual field practice
a much higher percent of oxygen transfer could be obtained with smaller
bubbles, deeper filters and most important, oxygen recycle.
Recycle Ratio
Wastewater recycle must be used with the preoxygenation submerged filter
for any waste with an ammonia nitrogen concentration greater than 8 to
10 mg/1 or a total oxygen demand greater than the oxygenation capacity
of the system. A reasonable assumption is that the total dissolved
oxygen available, TOA, in the influent to the filter should be equal to
or greater than the combined total oxygen demand of the mixture of the raw
influent waste and the recycled effluent in order to obtain a maximum
rate of nitrification (Figure 18). This assumption is based on the
finding that the maximum rate of nitrification occurred in the labora-
tory submerged filters when the dissolved oxygen concentration was
stoichiometrically equal to or greater than the ammonia nitrogen oxygen
requirement (2). Based on this assumption, the following relationship
can be developed:
TOD + R(TOD )
TOA > TOD. = W. , p (15)
1 I + K
65
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CD
CT)
WASTE
Q, TODW
£££00000
Opfl0600
00000000
OXYGEN
R)
TODj =
TODW + R(TODe)
RECYCLE
RQ , TODe
EFFLUENT
Q , TODe
Figure 18. Flow through submerged filter with recycle.
-------
where TOA total dissolved oxygen added;; the maximum value
obtainable is a function of pressure, temperature,
dissolved solids and the percent of oxygen satur-
ation which can be achieved in the wastewater.
TOD
w
TOD
e
total oxygen demand of the influent wastewater,,
total oxygen demand of the effluent wastewater.
total oxygen demand of the combined raw wastewater
and recycled effluent entering the filter.
R - recycle ratio = recycle flow rate/influent waste-
water flow rate.
By letting TOA = TOD^ the above equation can be solved to obtain the
minimun recycle ratio:
TOD - TOA
R _ w . .
min TOA - TOD ^6)
e
TOD and TOD are functions of the ammonia nitrogen, nitrite nitrogen,
and BOD concentrations in the influent and effluent, respectively. In the
results section, the oxidation of organic matter within the preoxygen-
ation filter was discussed. It was found that the oxygen demand due to
BOD oxidation averaged about 0.63 times the BOD,- concentration. Using
a conservative estimate, the oxygen demand due to organic oxidation
within the filter will be assumed to equal the BODt-.
On this basis a detailed expression for the minimum required recycle
ration is:
(4.57ENH2-N] + BOD5)w - TOA
Rmin = TOA - (4.57[NH -N] + BOD )
j be
The term (4.57[NHL-N] + BOD ) represents a concentration of dissolved
oxygen in the effluent large enough to insure the maximum oxidation
rate in the filter of both ammonia nitrogen and carbonaceous BOD. If
NEL-N oxidation is of primary concern it appears not necessary to in-
sure that the dissolved oxygen concentration be greater than the stoi-
chiometric requirement for ammonia nitrogen oxidation throughout the
filter. Therefore, the additional effluent dissolved oxygen for (BOD,-)
oxidation did not seem necessary and so this term was eliminated fronT
the above equation. This assumption needs verification. On this basis,
the final equation used is:
.
min TOA (4. 57 [NIL -
67
-------
To be precise 1.14(N02-N) should be subtracted from the numerator of
the above equation. Usually the effluent nitrite nitrogen concentra-
tion is so small that complete oxidation of all ammonia nitrogen to
nitrate nitrogen can be assumed for practical purposes.
An example calculation is given to demonstrate the use of this equation:
Given: (NH--N)w - 15 mg/1 (NiyN)e - 1.5 mg/1
(BODn) - 30 mg/1 (BOD ) = 5 mg/1
x 5 W ! 3 e
Temperature = 22 °C Pressure = 1 atm
Oxygen gas which is 99.5 percent pure is used.
Percent oxygen saturation obtained by oxygenation = 75.
Air is 20.9 percent oxygen.
Required: Find the minimum recycle ratio.
Solution:
/atm. \/#02\/#02 \ /IOO \ /Sol. of
~ \ press.) I sat. ) I in gas I \ 20.9 / I air in
= (1)(0.75)(0.995) _ (8.9)
= 31 .7 mg/1
4.57(NH -N) + BOD5 w -TOA
2) Recycle Ratio = ' ,J
TOA U.57(NH -N)
4.57(15) + 30 " 31.7
~ 31,1 - 4.57(1.5)
The above conditions were close to the operating conditions of the 60
minute detention time field preoxygenation filter. If the ammonia
nitrogen concentration is raised to 20 mg/1 the recycle ratio rises
to 4.0. If the temperature falls to 15 °C then the recycle ratio falls
to 2.1 because of the greater solubility of oxygen.
Advantages of the Submerged Filter
The most important advantage of the submerged filter is its simplicity
in both design and operation. It has advantages over the suspended
growth nitrification process (activated sludge type) in that it requires
less detention time and has a longer solids retention time. Biological
68
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solids separation in a final clarifier and sludge return are not
needed for either the preoxygenation filter or bubble oxygenation
filter. Since these filters have a solids retention time similar
to that of a trickling filter they need less supervision than a
suspended growth reactor. In addition, the laboratory study results
indicate nitrification can be achieved reliably in the filter at
temperatures near the freezing point of water.
Both the preoxygenation filter with recycle and the bubble oxygenation
filter provide a significant degree of BOD and COD reduction. The pre-
oxygenation filter also provides a low suspended solids effluent,, super-
ior to that from most clarifierscommonly used with the activated sludge
process.
The long solids retention time allows for stable nitrification at vary-
ing temperatures, ammonia nitrogen concentrations, pH and flow rates.
The submerged filter is well suited to the treatment of intermittent
waste discharges if the filter remains aerobic during periods of idle-
ness. Following periods without influent waste, on the order of a few
days, rapid secondary starting is possible.
Disadvantages of the Submerged Filter
The major disadvantage of the submerged filter is the potential clog-
ging problem. Based on present technology, it is quite likely that a
preoxygenation submerged filter would not be able to receive an influent
with an extremely high BOD and suspended solids concentration ( > 60 to
80 mg/1) because of this problem. However, the problem is minimized in
a. bubble oxygenation filter, although at the sacrifice of effluent qual-
ity. In addition, the higher the organic load on the filter the lower
will be the percentage of nitrifying bacteria within the suspended
solids in the filter, and thus, the longer the required detention time
for a given efficiency of nitrification.
Another possible disadvantage is the high cost for oxygen. An efficient
method of oxygen transfer (preoxygenation) or a good method for capture
of oxygen for recycle (bubble oxygenation) is needed to reduce this
cost to a minimum. High concentrations of oxygen in the effluent from
the bubble oxygenation system may represent a wastage of oxygen.
Estimated Cost of Treatment
Since experience with full scale submerged filters is lacking, many
assumptions have to be made in order to estimate costs of operation.
An influent ammonia nitrogen concentration of 20 mg/1 and an influent
BOD concentration of 30 mg/1 are assumed for estimating purposes along
with 2 hour detention time in the filter (two stages), Annual cost
data are based on the year 1972 using a 5.5 percent interest rate for
a 20 year design period. A summary of cost data for the bubble
69
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oxygenation filter reveals a total cost of 3.9, 2.5, 2.2 cents/1000 gal
for a 5, 20 and 100 mgd plant, respectively. The preoxygenation filter
with recycle has slightly higher costs of 4.8 to 2.8 cents/1000 gal in
the range of 5 to 100 mgd. A typical example of cost estimate for a 20
mgd plant is given in Table 21.
The total cost of treatment includes capital and operation and main-
tenance costs The capital costs can be divided into the categories
of filter rock, a structure to contain the rock, oxygen transfer equip-
ment, yard piping, pumps, motors, and finally administrative, engineer-
ing and contingency costs.
For two hour detention time, 28,800 ft"5 of rock are required (at 39
percent void volume) per 1 mgd of treatment capacity. This rock should
be of quality similar to that of trickling filter rock but with a diame-
ter of 1 to 2 inches. The rock specifications should involve values for
the Los Angeles Abrasion Test for Wear, the Sodium Sulfate Loss Test
(ASCE Manual 13) and the Adsorption Test (ASTM C127) (19). The filter
rock should be free of organic matter, soil, clay and any thin or elonga-
ted flat pieces of rock. The installed cost would be approximately
$0.18/ft3 of rock (19).
Another capital cost consideration is a water tight tank to contain and
support the rock. It will be assumed that the filter would be parti-
tioned off into 20x20 feet compartments to facilitate efficient back-
washing. No separate backwashing reservoir will be used in this calcu-
lation. The filter structure consists of the tanks, foundation and
influent distribution and effluent collection systems. Based on cost
figures for designing a similar anaerobic filter a structure cost of
$0.90/ft3 of rock will be used (19).
The oxygen transfer equipment includes blowers, motors, air piping and
instrumentation. The selection of the oxygen transfer equipment for
the bubble oxygenation filter was based on 90 percent oxygen utiliza-
tion efficiency. About 65 percent of the oxygen transfer will occur in
the first stage and 35 percent in the second stage. The recycled gas
would contain about 75 percent oxygen in the first stage and 55 percent
in the second stage. The required blower horsepowers for the 5, 20,
and 100 mgd plant are 50, 250, and 820, respectively. The preoxygenation
filter oxygen transfer equipment costs include a significant amount of
capital costs for a separate oxygen transfer chamber (17).
A fourth cost consideration is yard piping, pumps and miscellaneous items.
The preoxygenation system and bubble oxygenation system differ with
respect to pump requirements. It is possible to operate the bubble oxy-
genation filter without pumps, while the preoxygenation filter requires
recycle pumps capable of providing a recycle ratio of 4. Yard piping
is another highly variable design consideration.
The fifth and last capital cost consideration is the 30 percent adminis-
tration, engineering and contingency charge that is applied to the above
costs.
70
-------
TABLE 21
ESTIMATE OF FILTER COST*
(20 mgd)
Bubble
Preoxygenation Oxgenatiori
System Costs Filter Filter
I. Capital Costs
A. Filter Rock Installed
($0.18/ft3)
B. Filter Tank Structure
C. Oxygen Transfer Equipment
D. Yard Piping, Pumps, etc.
Sub- total:
E. Admins tration, Engineering
(Contingencies [30/o])
Total Capital Cost:
Average Annual Cost
(erf - 5.5-20)
Cents/1000 gal.
Dollars/ft3 of filter
$103,200
517,000
400,000+
80 , 800
1,101 ,000
330,000
1,431,000
120,000
1.7
2.49
$103,200
517,000
60,800
36,000
717,000
21 5 ,000
932,000
77,700
1.1
1.62
II. Operation and Maintenance Cost
(Annual)
A. Oxygen 69,000 69,000
B. Oxygen Transfer Equipment 12,000 12,000
C. Labor 30,000 20,000
Total 0 & M Cost (annual): 111,000 101,000
Cents/1000 gal. 1.5 1.4
Total Cents/1000 gal. 3.2 2.5
* Not including land cost, site preparation or unusual excavation
problems.
-j- Only approximate.
71
-------
The operation and maintenance costs associated with the submerged fil-
ter include oxygen costs, oxygen transfer equipment operational costs,
other operational costs and labor. At the use rates of oxygen pro-
jected, on site oxygen production appears to be the most economical
($16 to $20 per ton). Assuming a total oxygen demand of 125 mg/1 and
90 percent oxygen utilization efficiency about 0.58 tons of oxygen are
required per million gallons of treated wastewater. The cost per ton
of oxygen is described in detail elsewhere (17). The preoxygenation
system requires a greater quantity of electricity to operate the low
head recycle pumps.
The costs for oxygen, filter rock and oxygen transfer equipment are
reasonably accurate, but the estimated costs for the filter tank, yard
piping, pumps, engineering and labor can be highly variable depending
on the individual design conditions. The major costs items are oxygen
and the filter structure for the bubble oxygenation filter.
72
-------
SECTION VIII
ACKNOWLEDGEMENTS
Appreciation is extended to Mr. Robert Hiles, Operation Superintendent,
Union Sanitary District, Newark, California, for his support of this
project and for making the facilities of the District Treatment Plant
No. 3 available for conducting this study. Mr. Arthur Duarte, Assistant
Operating Superintendent, was most helpful in making necessary arrange-
ments for the study and for furnishing operating data for the treatment
plant. Special thanks go to Mr. John Silva, Supervisor of Plant No. 35
and the operating personnel for their interest in the study and willing-
ness to help whenever possible.
The director of the project was Dr. Perry L. McCarty, Professor of Civil
Engineering, Stanford University, Stanford, California. Mr. Donald D.
McHarness supervised the field studies and prepared the draft of this
report. He was assisted by Mrs. Victoria Mongird, who conducted many
of the analytical tests, and Mr. Deepak Bajracharya, who helped in the
general operation of the field units. The pilot plant was constructed
by Mr. Kevin Clancy. Dr. Roger T. Haug, who supervised the laboratory
portion of this overall study, also assisted in devising the study plan
and in helping to conduct the initial phases of the filter operation.
The support of this project by the Environmental Protection Agency, and
the assistance provided by'Mr. Edwin F. Earth, tne Grant Project Officer,
is greatly appreciated.
73
-------
SECTION IX
REFERENCES
1. Courchaine, R. J., "Significance of Nitrification in Stream
Analysis-Effects on the Oxygen Balance," Jour. Water Poll.
Control Fed.. Vol 40, No. 5, 835-47, (May 1968).
2. Haug, R. T. and McCarty, P. L., Nitrification With the Submerged
Filter, Technical Report No. 149, Department of Civil Engineering,
Stanford University, (August 1971).
3. "Nitrification in the BOD Test," Notes on Water Pollution, No. 52,
Water Pollution Research Laboratory, Stevenage, England, (March
1971).
4. Haug, R. T. and McCarty, P. L., Nitrification With the Submerged
Filter, Presented at the Annual Conference of the Water Pollution
Control Federation, San Francisco, California (October 1971).
5. Wild, H. E.j Sawyer, C. N. and McMahon, T. C., "Factors Affecting
Nitrification Kinetics," Jour. Water Poll. Control Fed., Vol. 43,
No. 9, 1845-54, (September 1971).
6. Monod, J., "The Growth of Bacterial Cultures," Annual Review of
Microbiology, Vol. 3, 371, (1949).
7. Michaelis, L. and Menton, M. L., "Kinetics of Invertase Action,"
Biochem. Zeit., Vol. 49, 333-369, C.A.7, No.2232, (1913).
8. Stratton, Frank E., Nitrification Effects on Oxygen Resources in
Streams. Ph.D. Thesis, Stanford University, (July 1969).
9. Standard Methods for the Examination of Water and Wastewater,
12th Ed., American Public Health Assoc., Inc., New York, (1965).
10. Standard Methods for the Examination of Water and Wastewater,
13th Ed., American Public Health Assoc., Inc., New York, 464,
(1971).
11. Wycoff, B. M., "Rapid Solids Determination Using Glass Fiber
Filters," Water and Sewage Works, Vol. 111, No. 6, 277, (June
1964).
12. Sawyer, C. N. and McCarty, P. L., Chemistry for Sanitary Engineers,
2nd Ed., McGraw-Hill Book Co., San Francisco, (1967).
13. Skoog, D. A. and West, D. M., Fundamentals of Analytical Chemistry,
2nd Ed., Holt, Rinehart and Winston, Inc., San Francisco, 670,
(1969).
75
-------
14. Eckenfelder, Jr., W. Wesley, Industrial Water Pollution Control,
McGraw-Hill Book Co., San Francisco, 62-3, (1966).
15. Mulbarger, M.C., "Nitrification and Denitrification in Activated
Sludge System," Jour. Water Poll. Control Fed., Vol. 43, No. 10,
2059-70, (October 1971).
16. Speece, R. E. and Adams, J. L., "U-tube Oxygenation Operating
Characteristics," Proceedings of the 23th Industrial Waste Confer-
ence, Purdue University, May 7, 8, and 9, 195-212, (1968).
17. Investigation of the Use of High-Purity Oxygen Aeration in the
Conventional Activated Sludge Process, Water Pollution Control
Research Series No. 17050 DNW05/70, by Union Carbide Corp., Linde
Division, Tonawanda, New York, (May 1970).
18. Speece, R. E., "The Use of Pure Oxygen in River and Impoundment
Aeration," Proceedings of the 24th Industrial Waste Conference,
Purdue University, May 6, 7, and 8, 700-12, (1969).
19. Peterson, Ralph R., Cornell, Rowland, Hayes and Merryfield, and
Clair A. Hill and Associates, Corvallis, Oregon, (Personal Cor-
respondence) .
20. Heukelekian, H., "The Relationship Between Accumulation, Bio-
Chemical and Biological Characteristics of Film, and Purification
Capacity of a Bio-filter and a Standard Filter," Sewage Works
Journal, Vol. 17, 516 (1945).
76
-------
SECTION X
PUBLICATIONS
1. Haug, T. R. and McCarty, P- L., Nitrification with the Submerged
Filter, Technical Report No. 149, Department of Civil Engineering,
Stanford University, (August 1971).
2. Haug, R. T. and McCarty, P. L., "Nitrification with the Submerged
Filter," Journal Water Pollution Control Federation, In Press.
77
-------
SECTION XI
LIST OF SYMBOLS
a = Regression coefficient, Y-intercept or rate constant.
b = Regression coefficient, slope or order of reaction.
BOD = Standard 5-day 20 C biochemical oxygen demand.
COD Standard chemical oxygen demand.
DO = Dissolved oxygen concentration, mg/1.
k Maximum utilization coefficient, mass/time-mass.
K The "half-velocity coefficient," the substrate concen-
tration at which the rate of reaction is one-half the
maximum rate, mass/volume.
R = Recyle ratio, recycle flow rate/untreated waste flow
rate.
R . Minimum required recycle ratio for the submerged filter.
S = Substrate concentration, mass/volume.
S, = Substrate concentration in the bulk liquid phase out-
side the bio-film, mass/volume.
S = Effluent NH_-N concentration from submerged filter,
mass/volume.
Sf = Substrate concentration in the bio-film, mass/volume.
S. = Substrate concentration at the liquid-film interface, or
1 influent NEb-N concentration to the submerged filter
after mixing of untreated and recycle flows, mass/volume.
S - Substrate concentration at the film-media interface,
mass/volume.
S.S. = Suspended solids concentration, mass/volume.
S = Untreated waste NH0-N concentration, mass/volume.
w 3
TOA = Total dissolved oxygen concentration added by preoxygen-
ation, mg/1.
79
-------
TOD = Total oxygen demand of the effluent from the submerged
e filter, mg/1.
TOD. - Total oxygen demand of the combined untreated and
recycled wastewaters entering the submerged filter,
mg/1.
TOD - Total oxygen demand of the untreated influent waste-
water, mg/1.
X Concentration of active microorganisms, mass/volume.
80
-------
SECTION XII
APPENDICES
A. Wastewater characteristics and treatment efficiencies
for the Union Sanitary District Plant No. 3 during
the period of this study.
Table A-1: Average monthly effluent quality for the
Union Sanitary District Plant No. 3. 83
Table A-2: Periodic analysis of wastewater characteristics
and treatment efficiency at the Union Sanitary
District Plant No. 3. . . 84
Table A-3: Typical nitrogen concentration changes through
the Union Sanitary District Plant No. 3. ... 85
Table A-4: Concentration of ammonia and organic nitrogen
in effluent from Union Sanitary District
Plant No. 3. ................. 85
B. Summaries of results from operation of preoxygenation
filter and bubble oxygenation filters.
Table B-1 : Summary of results for preoxygenation filter
at 60 minute detention time. ......... 86
Table B-2: Summary of results for preoxygenation filter
at 40 minute detention time 87
Table B-3: Summary of results for preoxygenation filter
at 30 minute detention time. 88
Table B-4: Summary of results for bubble oxygenation
filter at 60 minute detention time. ...... 89
C. Detailed analytical results from operation of preoxygenation
and bubble oxygenation filters.
Table C-1: Nitrogen data for preoxygenation filter at
60 minute detention time 90
Table C-2: Miscellaneous data for preoxygenation filter
at 60 minute detention time. ......... 91
Table C-3: Nitrogen data for preoxygenation filter at
40 minute detention time. 92
Table C-4: Miscellaneous data for preoxygenation filter
at 40 minute detention time 93
Table C-5: Nitrogen data for preoxygenation filter at
30 minute detention time. . 94
Table C-6: Miscellaneous data for preoxygenation filter
at 30 minute detention time. ......... 95
Table C-7: Nitrogen data for bubble oxygenation filter at
60 minute detention time, 96
Table C-8: Miscellaneous data for bubble oxygenation filter
at 60 minute detention time 97
Table C-9: Nitrogen data for bubble oxygenation filter at
30 minute detention time. 98
Table C-10: Miscellaneous data for bubble oxygenation filter
at 30 minute detention time 99
81
-------
D. Detailed data obtained during 24-hour study of filter
operation.
Table D-1: Preoxygenation filter. 100
Table D-2: Bubble oxygenation filter. 101
82
-------
TABLE A-1
CD
(JO
AVERAGE MONTHLY EFFLUENT QUALITY FOR THE
Effluent (24 hour comp
Month Flow MGD
1971 :
May
June
July
August
September
October
November
December
1972:
January
2.3
2.4
2.3
2.4
2.5
2.3
2.4
2.6
2.6
Susp.
Ave.
18
23
22
34
29
40
59
55
69
Sol.
Low
11
12
14
18
19
26
33
26
28
(mg/1)
High
27
42
43
114
102
63
144
94
124
BOD5(
Ave.
26
32
36
43
42
46
55
46
56
UNION
SANITARY DISTRICT PLANT NO. 3 (1
>osite)
mg/1)
Low
12
7
27
28
30
33
39
20
40
Influent
High High
52 7.8
60 7.9
51 7.7
77 7.9
94 7.9
63 7.8
88 7.9
64
90
pH (Grab)
Low
7.4
7.2
7.2
6.7
7.1
7.4
7.3
-
-
(1) Collection and analysis performed by Union Sanitary District.
-------
TABLE A-2
PERIODIC ANALYSIS OF WASTEWATER CHARACTERISTICS AND TREATMENT EFFICIENCY
AT THE UNION SANITARY DISTRICT PLANT
Suspended Solids
Date
5/20/71
6/23/71
CD 7/22/71
8/18/71
9/21/71
10/20/71
11/23/71
12/16/71
1/9/72
Inf.1
mg/1
273
247
272
435
301
223
267
-
-
Eff.2
mg/1
17
32
25
43
25
40
41
-
-
Percent
Removed
94
81
91
90
92
82
85
-
-
Grease
Inf.1
mg/1
99
92
84
84
96
90
215
128
105
Eff.2
mg/1
1 .6
3-6
5.8
4.7
3.6
9.4
6.5
5.5
12.1
Percent
Remov ed
98
96
93
94
96
89
97
94
88
Inf.1
mg/1
207
193
215
427
211
188
205
-
-
NO. 3 (3).
BOD
ID
Eff.2
mg/1
23
39
29
41
33
53
51
-
~
Percent
Removed
89
80
86
90
84
72
75
-
-
Inf.1
mg/1
634
622
602
863
660
618
701
715
872
COD
Eff.2
mg/1
104
117
133
135
140
187
180
176
235
Percent
Removed
84
81
78
84
79
70
74
75
73
(1) 8 hour composite (8:00 a.m. - 4:00 p.m.).
(2) 24 hour composite.
(3) Collection and analysis performed by Union Sanitary District.
-------
TABLE A-3
TYPICAL NITROGEN CONCENTRATION CHANGES THROUGH
THE UNION SANITARY DISTRICT PLANT NO. 3.
(November 23-24, 1971) (1 )
Parameter
NHL-NOng/l)
NO~-N(mg/l)
NO" -N (mg/1)
Org-N(mg/l)
Total-N(mg/l)
Raw
Sewage
15.0
0.3
0.05
14.4
: 29.7
Vacuator
Effluent
16.2
0.0
0.1
19.3
35.6
Final
Effluent
13-7
0.2
0.2
8.8
22.9
TABLE A-4
CONCENTRATION OF AMMDNIA AND ORGANIC NITROGEN IN EFFLUENT
FROM UNION
Numb er o :
Month Samples
1971 :
June
July
August
September
October
Nov emb er
December
1972:
January
8
17
6
9
5
17
5
7
SANITARY DISTRICT PLANT NO. 3 (3).
Ammonia-N Organic-N
mg/1 ___,_ r mg/1
L
Ave
15.
15.
14.
16.
18.
18.
16.
18.
1
4
8
6
2
4
3
8
7
iiumucj. uj. 22
High Low Samples Ave. High Low
11.7 4 3.8 1.8
19.0 9.3 4 4.8 - 3.1
10.7 2 5.5 - -
20. 8 9. 6 1 6.2
25.9 12.5 - ...
23.0 9.3 1 8.8 - -
23.9-0
31.2 0 - -
(1) 24-hour composite samples.
(2) Grab samples.
(3) Influent nitrogen concentration to field nitrification filter.
85
-------
TABLE B-1
SUMMARY OF RESULTS FOR PREOXYGENATION FILTER
AT 60 MINUTE DETENTION TIME (l)(4).
(May 4 to August 2, 1971)
Parameter
Temperature ( C)
9
Flow Rate (gal/ft /min)
Recycle Ratio (2)
pH- influent
effluent
difference
Alkalinity (mg/1 as CaCOo)-inf.
eff.
diff.
Ibs 00/lb NH_-N oxidized
2 3
Dissolved Oxygen(mg/l)-inf . (3)
eff.
total diff. (3)
Organic Nitrogen(mg/l)-inf .
eff.
NHo-N(mg/l)-inf.
3 eff.
percent removed
NO~-N(mg/l)-eff.
NO"-N(mg/l)-eff.
Total Nitrogen(mg/l)-inf .
eff.
BOD(mg/l)-inf.
eff.
percent removed
COD(mg/l)-inf.
eff.
percent removed
sol inf.- sol eff. (5)
Suspended Solids (mg/l)-inf.
eff.
percent removed
(1) Based on untreated waste flow
Ave. or
Range
21-27
0.82
2.75
7.4
7.1
0.3
342
237
105
340-510
32.5
8.5
84.8
3.6
1.5
14.3
1.0
93
0.6
15.9
19.1
19.5
35(35)
5.0
84.8
104
51
51 .7
-
26.5(28)
3-5
90.2
No. of
Samples
-
-
-
4
4
4
7
7
7
-
4
7
7
6
8
8
8
8
8
8
8
8
5(4)
5
5
4
4
4
-
4(3)
4
4
rate and filter void
Standard
Deviation
-
-
-
+0.05
+0.05
+0.00
+8.5
+8.0
+13.5
_
+1.3
+2.5
±3.0
+1.3
+0.7
+2.6
+0.4
±3.1
±0.4
±3.0
+3.0
±2.8
+10(5.7)
±3.0
±9.7
+15
±12
±6.0
-
+2.5
±3.6
±6.5
volume.
(2) Recycle Ratio = recycle f lowrate/waste flowrate.
(3) Dissolved oxygen of diluted influent waste(
Oxygen Used = (recycle ratio
+ 1 )(lnf. DO
(4) Data shown in parenthesis refers to samples
Union Sanitary District.
(5) Soluble (sol).
filter
- Eff.
entrance);; Total
DO).
collected and tested by
-------
TABLE B-2
SUMMARY OF RESULTS FOR PREOXYGENATION FILTER
AT 40 MINUTE DETENTION TIME (1)(4),
(October 13 to November 10, 1971)
Parameter
Temperature ( C)
o
Flow Rate(gal/ft /min)
Recycle Ratio (2)
pH-influent
effluent
difference
Alkalinity(mg/l as CaCO )-inf.
6 eff.
diff.
Ibs 0 /lb N1L-N oxidized
£ 3
Dissolved Oxygen(mg/l)-inf.(3)
eff.
total diff.(3)
Organic Nitrogen(mg/l)-inf.
eff.
NIL-N(mg/l)-inf.
J eff.
percent removed
N02-N(mg/l)-eff.
NO~-N(mg/l)-eff.
Total Nitrogen(mg/l)-inf.
eff.
BOD(mg/l)-inf.
eff.
percent removed
COD(mg/l)-inf.
eff.
percent removed
sol inf.-sol eff.(5)
Suspended Solids(mg/l)-inf.
eff.
percent removed
Ave. or
Range
16-27
1 .16
3.0
7.4
7-1
0.3
349
255
95
No. of
Samples
-
-
2
2
2
11
11
11
Standard
Deviation
-
-
-
"
+20
+20
+21
250-500
31-4
16.9
54.6
46(38)
3.4
91.7(90)
132
61
46
20.1
54(38)
6.6
87.3(83)
5
5
5
4(2)
4
4(2)
2
2
2
2
3(3)
3
3(3)
+4.5
+5.5
+2.7
19.6
5.6
70
4.1
6.9
10
10
10
6
6
+4.2
+2.6
+10.8
±1-3
+1 .9
+2.8
+2.2
+4.9
(1) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = recycle flow rate/waste flow rate.
(3) Dissolved oxygen of diluted influent waste(filter entrance)^ Total
Oxygen Used = (recycle ratio + l)(lnf. DO - Eff. DO).
(4) Data shown in parenthesis refers to samples collected and tested by
Union Sanitary District (influent pilot plant sampler tended to collect
too many solids).
(5) Soluble (sol). Q?
-------
TABLE B-3
SUMMARY OF RESULTS FOR PREOXYGENATION FILTER
AT 30 MINUTE DETENTION TIME (1)(4).
(August 16 to September 28, 1971)
Ave. or No. of Standard
Parameter Range Samples Deviation
Temperature (°C) 19-31
Flow Rate(gal/ft /min) 1.29
Recycle Ratio (2) 2.0 & 3.0
pH-influent 7.3 3
effluent 7.0 3
difference 0.3 3
Alkalinity(mg/1 as CaCO )-inf. 320 18 +61
* eff. 265 18 +60
diff. 55 18 +24
Ibs 0 /lb NIL-N oxidized 240-500
" J
Dissolved Oxygen(mg/l)-inf.(3) 24.9 11 +3.7
eff. 12.9 11 +3.3
total diff.(3) 52.4 11 +8.0
Organic Nitrogen(mg/l)-inf. 5.7 3
eff. 2.5 5 +0.5
NH3-N(mg/l)-inf. 15.2 18 +3.6
eff* 6.9 18 +3.1
percent removed 55 18 +15.7
NOg-N(mg/l)-eff. 1.7 n ±1 .3
NO--N(mg/l)-eff. 6.0 11 ±2.8
Total Nitrogen(mg/1)-inf. 19.6 2
eff. 16.4 2
BOD(mg/l)-inf. 53.4(37) 5(3) +14.1
eff- 9.6 5 +5.9
percent removed 80.4(77) 5(3) +9.2
COD(mg/l)-inf. 124 4 +10.2
eff. 54 4 +1K6
percent removed 62 4 +17
sol inf.-sol eff.(5) 26 4 +3^6
Suspended Solids(mg/l)-inf. 38.8(25) 7(6) +11.0(4.5)
eff. 6.5 7 +3.0
percent removed 85.0(76) 7(6) £5.2(3.7)
(1) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = Recycle flow rate/waste flow rate.
(3) Dissolved oxygen of diluted influent waste(filter etrance)j Total
Oxygen Use = (recycle ratio + 1)(Inf. DO - Eff. DO).
(4) Data shown in parenthesis refers to samples collected and tested by
Union Sanitary District (influent pilot plant sampler tended to col-
lect too many solids).
(5) Soluble (sol).
-------
TABLE B-4
SUMMARY OF RESULTS
AT 60 MINUTE
(August 11
Parameter
Temperature ( C)
2
Flow Rate(gal/ft /min)
pH-influent
effluent
difference
Alkalinity (mg/1 as CaCO_)-inf.
5 eff.
diff.
Ibs 0_/lb NIL -N oxidized
2 3
0 Flow Rate(cfm/ft at NTP)
Li
Dissolved Oxygen (mg/l)-ef f .
Organic Nitrogen(mg/l)-inf .
eff.
NH_-N (mg/1) -inf.
3 eff.
percent removed
NO"-N(mg/l)-eff.
Li
NO" -N (mg/1) -eff.
Total Nitrogen (mg/l)-inf.
eff.
BOD(mg/l)-inf.
eff.
percent removed
COD(mg/l)-inf.
eff.
percent removed
sol inf. -sol eff. (3)
Suspended Solids (mg/1) -inf.
eff.
percent removed
FOR BUBBLE OXYGENATION
DETENTION TIME(J ) (21.
to .November 24, 1971)
Ave. or No. of
Range Samples
16-30
0.22
7.4 1
7.1 1
0.3 1
342 7
214 7
128 7
260-580
0.08-0.12
26.6 5
-
-
18.3 8
1.76 8
91 8
0.4 7
18.4 7
-
-
50.5(37) 6(5)
9.5 8
79.3(75) 6(5)
127 6
63 9
56 5
29.1 7
43.9(30) 6(6)
15.7 8
63.8(56) 6(6)
(1 ) Based on untreated waste flow rate and filter void
(2) Data shown in parenthesis
FILTER
Standard
Deviation
_
-
-
-
-
+18.2
+13.0
+25.4
_
-
+4.1
-
-
+4.2
+1 .0
+4.2
+0.1
+3.8
-
-
+14.2(3.1)
+3.4
+8.2(6.9)
+18
+18.4
+8.5
±3.4
+13.6(9.6)
+14.0
±43(39)
volume.
refers to samples collected and teste
(3)
by Union Sanitary District (influent pilot plant sampler tended to
collect too many solids).
Soluble (sol).
89
-------
TABLE C-1
CD
O
NITROGEN DATA FOR PREOXYGENATION FILTER AT 60 MINUTE DETENTION TIME (l)
Days
Af t er
Start-up
(Flow Rate - 0.82 gal/ftZ/min; Recycle Ratio - 2.75(2))
Organic-N(mg/l) m^ , ,,,
Inf.
Type of Sample Total Sol.
Eff. Inf. Eff.
Total Sol. mg/1 mg/1
nu ~"ii Vmo' L I HU^-LN
Percent
Removed Inf. Eff. Inf.
to/1) Total-N^/l) PH
Eff. Inf. Eff. Inf. Eff.
(May 4 to August 2, 1971)
30
37
40
45
48
50
57
64
70
79
90
249
254
261
269
grab
24 hr composite
grab
24 hr composite
grab
24 hr composite
8 a.m. grab
24 hr composite 4.2
11 a.m. grab
24 hr composite 4.0
8 a.m. grab
24 hr composite 3-3
8 a.m. grab 1 .8
24 hr composite 4.0
8 a.m. grab 3.9
24 hr composite 5.7
8 a.m. grab 3-1
24 hr composite
10 a.m. grab
2 p.m. grab
1 to 2 days of anaerobic
24 hr composite
12.00 noon grab
24 hr composite
11 a.m. grab
24 hr composite
11 a.m. grab
12.6 11 .8
14,0 2.1
-
14.9 1.7
12.1 2.3
_
-
1.6 - 17.7 3.8
- - - -
1.2 - 14.0 1.4
13.0 1.8
0.7 - 16.3 1-3
1.0 - 11.7 1.7
1.5 - 18.3 0.6
1.4 - 15.3 1-4
0.7 - 15.9 1.0
2.2 - 13.9 0.8
2.2 - 13.2 0.8
2.4 - 10.7 0.52
(January 3 to
31.2 12.6
conditions before day 246.
19.3 9-4
21.7 7.4
19.0 5.0
18.6 3.2
17.7 4.4
14.3 3.8
6 - - -
85 - >2.8
-
89 0.04 2.3
81 0.02 1.5
-
-
78 0.01 1.35 0.15
-
90 0.18 0.75 0.1
86 0.00 0.55 0.1
92 0.1 1.4 0.07
86 0.02 0.55 0.15
97 0.12 0.75 0.00
91 0.02 0.60 0.00
94 0.04 0.15 0.00
94 0.01 0.45 0.15
94 - 0.4
95 - 0.36
February 10, 1972)
60
51
61
74
83
75
73
7.7 7.3
-
-
- _
-
-
7.3 7.0
13.3 22.0 20.0
7.3 7.1
16.7 18.3 20.1
16.0 - - - -
12.3 19.8 15.7
13.3 13-7 16.5
22.0 22.3 24.9
17.4 19.2 20.8 7.4 7.1
17.0 21.6 18.8
16.0 16.3 19.4 7.4 7.1
14.6 - 18.0 7.5 7.2
14.4 - 17.7
-
-
-
-
-
...
- - -
During day 264-268 the filter was aerobic with no influent feed.
276
283
24 hr composite
11 a.m. grab
24 hr composite
11 a.m. grab
19.3 6.4
18.3 5.4
17.8 3.4
17.7 3.4
67
70
81
81
-
-
-
-
("1") Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio - recycle flow rate/waste flow rate.
-------
TABLE C-2
MISCELLANEOUS DATA FOR PREOXYGENATION FILTER AT 60 MINUTE DETENTION TIME (l)(4)
Days
After i emp
Start-up (°C)
30
37
40
45
48
50
57
64
70
79
90
249
254
261
269
22
22
23
23
-
22
-
21
-
22
-
22
24
-
,
17
1
-
17
_
19
_
16
(Flow Rate -
Alkalinity Ibs Og/lb
(me/I as CaCO,) NH,-N DO (mi
Inf. Eff. Oxidized
368
362
368
350
342
344
328
346
338
350
338
354
-
312
to 2 days of
320
314
-
-
390
326
During day 264
276
283
-
18
-
19
364
344
-
-
260
268
250
250
254
238
243
222
238
230
240
245
-
216
anaerobic
252
238
-
-
284
302
to 268 the
268
268
-
-
400
553
621
464
696
343
437
420
512
-
-
-
conditions
-
-
-
-
-
-
filter wa:
-
-
-
-
Inf. (3)
36.8
31.6
36.4
26.8
33.6
-
33.6
-
33.6
-
30.4
-
33.8
32.3
35.8
35.6
before
-
39.4
-
28.4
-
34.4
0.82 gal/ft2/min; Recycle Ratio - 2.75 (2))
BOD (mg/1) COD(mg/l)
3 n n f
;/l) Inf. Eff. Inf. Eff. b" S'i'
Eff. Total Sol. Total Sol. Total Sol. Total Sol. Inf.
(May 4 to August 2, 1971)
12.2 - -- -----
8.4- -- -----
12.2 - - - -----
23.4(36) 2.9
8.8 - - - -----
9.6 - - - -----
6.4 - - - -----
13.6 - --------
6.0 38.6(42) - 9.2 - 108 - 48 - 26.5(32)
12.0 26.4 - 7.1 82 37 - 24.5
5.6 >40(35) - 3.1 - 115 - 54 - 30.0(27)
8.0 - - - -----
6.8 48(28) - '2.7 - 111 - 63.2 42.8 25(24)
11.0- -- --
9.9 - - - -----
13.2 - ---.....
(January 3 to February 10, 1972)
18.0 - -------
day 246.
- .
19.2 - -------
-
9.6 - -------
-------
21.2- --
ng/1)
Eff.
-
-
-
1.0
trace
8.6
-
3.5
-
-
-
.
_
-
.
-
-
.
5 aerobic with no influent feed.
-
29.2
-
28.8
-
13.4 - -
-
12.4 - -------
,
-
-
'
(1 ) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = recycle flow rate/ waste flow rate.
(3) Dissolved oxygen of diluted influent waste (filter entrance)} Total oxygen used = (recycle ratio + l)(Inf. DO - Eff. DO).
(4) Data shown in parenthesis refers to samples collected and tested by Union Sanitary District (influent pilot plant sampler tended
to collect too many solids).
-------
TABLE C-3
NITROGEN DATA FOR PREOXYGENATION FILTER AT 40 MINUTE DETENTION TIME (l)
(Flow Rate - 1.16 gal/ft2/min: Recycle Ratio - 3.0(2))
CD
DO
Days
After
Start-up
164
166
173
179
183
191
Organic-N(mg/l)
Inf. Eff.
Total Sol. Total Sol.
-
-
-
.
-
_
_
NIL-N
3
Inf. Eff.
mg/ 1 mg/ 1
(October 13
15.3 5.0
25.0 7.6
2.8
- 3.4
5.0
22.3 3-0
2.4
Removed Inf. Eff. Inf. Eff. Inf. Eff. Inf. Eff.
to November 10, 1971 )
67 --------
70 --------
.
-
-
86 --------
-
Type of Sample
24 hr composite
3 p.m. grab
10:30 a.m. grab
12:00 noon grab
1:15 p.m. grab
3:15 p.m. grab
24 hr composite
11:00 a.m. grab
2
5 days after backwashing at 20 to 40 gal/ft /min.
24 hr composite - 17.6 2.8 84
11:00 a.m. grab
12.5 2.4
81
10 days after backwashing at 20 to 40 gal/f t^/min.
24 hr composite - 18.0 7.6 58
1:00 p.m. grab
23.0 7.8
66
0.08
0.02
0.02
0.04
5.0
2.0
3.6
2.9
9.7
8.4
7.6
6.1
15 days after backwashing at 20 to 40 gal/ft /min.
3:00 p.m. grab - 23.0 5.6 76 -
2
2 hours after backwashing at 20 to 40 gal/ft /min and draining.
24 hr composite - 23-3 10.6 52 - 5.4
11:00 a.m. grab - ... 15.0 6.2 61 - 5.6
5.3
5.1
(1) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = recycle flow rate/waste flow rate.
7.5 7.1
7.4 7.1
-------
TABLE C-4
CD
MISCELLANEOUS
DATA FOR
(Flow Rate -
Days
After Temp.
Start-up (°C)
164
27
166
-
-
-
173
21
179
16
183
23
186
191
22
Alkalinity
(mg/1 as CaCO^
Inf.
340
384
-
-
-
-
364
348
339
319
360
364
362
350
318
Eff.
236
263
-
-
-
-
234
254
222
242
279
272
270
280
250
Ibs 0 Jib
N1L-N
Oxidized
-
-
-
-
-
-
251
345
505
500
342
- -
384
500
D0(mg
inf.'4'
27.4
35.6
35.6
34.8
34.8
-
34.2
-
-
-
25.4
-
-
28.8
PREOXYGENATION FILTER AT 40 MINUTES DETENTION TIME (1)(3)
1.06 gal/ft2/min; Recycle Ratio - 3.0(2))
BOD (mg/1) COD(mg/l)
/ 1 \ ...rri'/it
/1} Inf. Eff. Inf. Eff. - - ("*' l>
Eff. Total Sol. Total Sol. Total Sol. Total Sol. Inf. Eff.
(October 13 to November 10, 1971)
13.2 ....----..
22.0 -..-.--...
24.4 ----------
22.8 ----------
21.6 ----------
-
20. 8-- - - --
47.3(36) - 1 - 75.3 51.7 - - 40.6(34) 7.2
23.2 - - 6.2 - - -
44(39) - 5.0 - 151 86 68.4 61.556.0(36) 6.4
11.2 ----------
-
43.5(50) - 3.1 - - 58.8 54.9 43.1 65.3(45) 6.2
14.8 48.9 ---------
(1 ) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = recycle flow rate/waste flow rate.
(3) Data shown in parenthesis refers to samples collected and tested by Union Sanitary
District (influent pilot plant sampler tended to collect too many solids).
(4) Dissolved oxygen of diluted influent waste (filter entrance); Total Oxygen Used = (recycle ratio + !)(lnf. DO - EFF. DO).
-------
TABLE C-5
C£>
Days
After
Start-up
96
98
100
105
111
120
125
132
138
213
218
226
233
Type of Sample
10:00 a.m. grab
1 1 :00 a.m. grab
48 hr composite
10:00 a.m. grab
21 hr composite
9:00 a.m. grab
24 hr composite
10:00 a.m. grab
24 hr composite
24 hr composite
10:00 a.m. grab
24 hr composite
24 hr composite
12:00 noon grab
24 hr composite
1 :00 p.m. grab
24 hr composite
2:00 p.m. grab
1 :00 p.m. grab
24 hr composite
2:00 p.m. grab
4:00 p.m. grab
2:00 p.m. grab
NITROGEN DATA FOR PREOXYGENATION FILTER AT 30 MINUTE DETENTION TIME(1 )
(Flow Rate - 1.29 gal/ft2/min; Recycle - 2.0(2))
Organic-N(mg/l) NH3-N NO_-N(mg/l) NO,-N(mg/l)
Tnf T7ff ^ T t~ - 1 T1] f mo ' 1 ^ nH
' Inf Eff Perrpnf iOtal-M (mf,/ L ) on
Total Sol. Total Sol. mg/1 mg/1 Removed Inf. Eff. Inf. Eff. Inf. Eff, Inf. Eff.
(August 16 to September 28, 1971)
.
11.7 7.0 40 0.01 1.0 - - - - 7.2 6.9
14.3 8.8 39 ----- -
12.0 7.0 42 ----- -
5.6 - 2.1 - 15.0 8.6 43 0.00 0.55 0.1 6.4 20.7 17.7
5.3 - 2.5 - 13.0 6.0 54 0.01 0.35 0.1 6.2 18.4 15.1
6.2 2.7 2.2 2.1 15.9 3.4 78 0.00 2.75 0.05 7.9 22.2 16.3
11.6 3.8 67 0.04 1.65 0.12 8.4 - - 7.3 6.9
16.7 3-4 80 0.00 1.8 - 6.4 - -
16.3 - - ----- -
10.0 3.2 68 0.02 0.75 - 10.2 - -
14.0 4.6 67 0.05 2.40 - 6.1 - -
9.6 2.4 75 0.00 0.60 - 5.1 - - 7.3 7.1
15.6 5.6 64 - 1.86 - 6.8 - -
-
18.9 11. 4 40 --..
20.8 11 .3 46
(Flow Rate - 1.72 gal/ft2/minj Recycle Ratio - 3.0)
(December 2 to December 22, 1971)
16.3 6.4 61 ----- .
2.6 2.0 16.8 8.8 48 - 4.8 - 1.6 - 17.8
23.9 10.6 56 - 4.7 - 1.0 -
3.3 2.6 19.0 - - ----- ...
15.5 11. 7 24 - -.-
(1 ) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = recycle flow rate/ waste flow rate.
-------
TABLE C-6
ID
01
MISCELLANEOUS DATA FOR PREOXYGENATION FILTER AT 30 MINUTE DETENTION TIME (1)(3)
Days
After Temp
Start-up (°C)
Alkalinity
(mg/1 as CaCOj)
Inf.
Eff.
Ibs 0,
NH,-N
Oxi diz
(Flow Rate - 1 .29 j
/ lb D0(mg/l)
ed Inf.
( ' Eff.
(August 16
96
98
100
105
111
120
125
132
138
213
218
226
233
(1)
(2)
(3)
-
25
-
-
-
25
-
23
-
-
24
-
-
31
-
27
-
27
19
-
21
20
-
-
302
350
344
204
196
334
320
342
-
338
-
332
310
346
-
472
380
329
290
260
322
-
-
270
297
302
168
170
241
246
246
-
272
-
256
262
272
-
406
347
273
236
182
328
-
-
480
-
500
-
405
-
380
240
-
440
330
-
440
290
-
455
-
-
-
-
-
-
Based on untreated waste flow rate ;
Recycle Ratio = recycle flow rate/w;
Data shown in parenthesis refers to
30.0
27.4
-
28.6
-
30.0
-
33.4
-
-
34.8
-
-
31.2
30.0
-
32.4
-
(Flow
28.0
-
25.4
21 .8
11 .8
13.6
-
14.4
6.8
14.4
-
12.8
-
-
16.8
6.4
-
12.4
10.4
-
9.4
-
Rate - 1 .
3al/ft2/min; Recycle Ratio - 2.0(2))
BOD5(mg/l)
COD(mg/l)
Inf. Eff. Inf. Eff. S.S.(mg/l)
Total Sol. Total Sol. Total
to September 28, 1971 )
-
-
-
>44.7(40) - 13 - 117
-
67(38) - 8.5 - 138
-
56 - 5.1 - 116
54(32) - - - 105
43 - 100
125
149
-
-
-
-
-
2
72 gal/ft /min; Recycle Ratio - 3.0)
Sol. Total Sol. Inf.
-
-
46.5(31)
19.5
66.7 46.8 39.6 36.7(29)
-
67.5 51.9 46.0 41.1(21)
31.3
69 45.2 39.2 42.7(21)
74 - - 22.7(21)
58.2 - - 35.3
60 45.2 34.8 54.0(25)
104 - - 34.7(25)
-
-
-
-
_
Eff.
-
-
5.4
4.8
7.0
-
5.0
4.2
5.6
-
-
5.6
-
-
-
-
-
-
(December 2 to December 22, 1971)
15.6 - --------
-
12.4
10.4
34.2(36) - 9.8 - 134
55.0(39) - - - 142
66.8(47) 17.3 12.1 5.7 133
62.8 58.5 53.0 57(38)
63.8 - - 70(52)
83.8 75.1 59.3 73(44)
8.0
-
13.3
md filter volume.
iste flow rate.
samples collected and tested by Union Sanitary
District (influent pilot plant sampler tended to collect too many solids).
(4) Dissolved oxygen of diluted influent waste (filter entrance)j Total Oxygen Used = (recycle ratio + 1) (Inf. DO - Eff. DO).
-------
TABLE 07
NITROGEN DATA FOR BUBBLE OXYGENATION FILTER AT 60 MINUTE
(Flow Rate - 0.22 gal/ft2/min)
Days
After
Start-up
6
20
25
32
41
46
53
CO
05 59
74
76
83
89
94
102
116
Organic-N(mg/l) NH -N
Inf" Eff" Inf. Eff.
Type of Samples
Seed: grab
10:00 a.m. grab
9:00 a.m. grab
10:00 a.m. grab
10:00 a.m. grab
2:00 p.m. grab
1 :00 p.m. grab
2:00 p.m. grab
24 hr composite
3:00 p.m. grab
10:30 a.m. grab
12:00 noon
1 :15 p.m.
3:15 p.m.
24 hr composite
1 1 :00 a.m. grab
24 hr composite
1 1 :00 a.m. grab
24 hr composite
1 :00 p.m. grab
24 hr composite
11 :00 a.m. grab
24 hr composite
Total Sol. Total Sol. mg/1
(August
-
12.0
5.3 - 2.2 - 13.0
2.5 - 11.6
10.0
9.6
20.8
15.3
25.0
-
...
.
- - - -
22.3
-
17.6
12.5
18.0
23.0
4.6 2.1 23.3
16.0
8.8 - - - 13-7
mg/1
11 to
-
13-0
11.3
9.9
3.0
0.4
3.0
6.1
8.5
7.7
1.2
2,2
3.0
4.4
1.4
0.6
1.9
0.5
1.0
3.8
2.6
1.9
1.0
Percent
Removed
November
-
-
13
15
70
96
71
44
69
-
-
-
-
94
-
89
96
94
83
8.9
88
93
N02-N(mg/l)
Inf. Eff.
24, 1971)
-
-
0.01 0.60
0.04 1.95
0.02 2.45
o.oo 0.3
0.6
-
-
-
-
-
-
-
-
0.6
0.3
0.02 0.45
0.04 0.55
0.3
0.15
0.18 0.4
DETENTION TIME (1 )
N03-N(mg/l) Total-N(mg/l) pH
Inf. Eff. Inf. Eff. Inf. Eff.
-
-
0.1 1.6 18.4 15.7
0.12 2.8 - 17.2 7.3 6.8
8.6 ....
9.2 - - 7.3 7.0
16.0 ....
-
-
-
....
-
- - - - - -
-
-
17.6 ....
12.9 ....
19.8 ....
24.1 ....
22.0 - 29.5
15.4 - - 7.4 7.1
0.23 17.4 22.9 - 7.6 7.1
(1) Based on untreated waste flow rate and filter void volume.
-------
TABLE C-E
MISCELLANEOUS DATA FOR BUBBLE OXYGENATION FILTER AT 60 MINUTE DETENTION TIME (1 ) (2)
Days
After
Start-up
6
20
25
32
41
46
53
59
74
76
83
89
94
102
116
Tpmn
J. ClllJJ
-
-
23
22
23
30
24
24
-
24
-
-
-
-
-
19
-
16
-
21
-
20
-
(1 ) Based on
(2) Data
Alkalinity
(mg/1 as CaCO )
Inf.
-
344
204
320
338
310
-
380
340
384
-
-
-
-
-
-
339
319
360
364
350
318
343
untreated
Eff.
-
342
172
295
274
249
-
274
260
249
-
-
-
-
-
-
219
222
220
190
208
210
230
waste
shown in parenthesis
(Flow Rate - 0.2
°2 Feed Ibs 02/lb
(cfm/ft2) NHg-N DO
at NTP - ...
0
0
0
0
0
0
0
0
0
0
0
flow
-
.014
.014
.014
.020
.027
.028
.028
-
-
-
-
-
-
-
.081
-
.091
-
.084
-
.124
-
rate
refers to
_ i . j_
uxidized
(August 11
-
-
490
490
200
200
-
129
-
-
-
-
-
-
-
263
-
503
-
294
-
587
-
and filter void
mg/1
12 gal/ft2/min)
BOD5(mg/l)
Inf. Eff.
Total Sol. Total Sol.
COD(mg/l)
Inf. Eff.
Total Sol. Total
Sol.
S.S.(mg/l)
Inf. Eff.
to November 24, 1971 )
21.6
16.0
14.8
8.2
11.6
16.0
20.4
9.6
-
9.2
16.8
20.
19.2
17.6
-
29.6
-
24.4
-
21 .2
-
31.6
26.2
volume.
samples collected and
- - - -
-
44(40) - 13
67(38) - 10.7
56(32) - 7.1
-
-
-
-
-
-
-
-
-
-
-
47.3(36) - 4.7
6.2
44(39) - .7.8
12.4
43.5
48.9 - 14.0 3.5
-
tested by Union Sanitary
-
.
117 67 48.6
138 68 54.5
100 58 42.6
125 60 74.8
-
.
-
-
.
.
-
-
-
.
132 77.3
53 . 6
151 86 58.6
80.0
58.8 51.0
99.9
-
-
-
39.6
50.2
34.0
30.5
-
-
-
-
-
-
-
-
-
-
48.6
-
50.8
54.7
27.4
25.4
-
-
-
37(29) 9.5
31.3(21) 3-6
35.3(21) 5.6
35(25) 34.7
-
-
-
-
-
-
-
-
-
-
40.6(34) -
3.4
56.0(36) 10.0
20
65.3(45) 38.7
-
-
District (influent pilot plant sampler tended to collect too many solids)
-------
TABLE C-9
to
CO
NITROGEN DATA FOR BUBBLE OXYGENATION FILTER AT 30 MINUTE DETENTION
Days
After
Start-
118
(November 26, 1971 - February 10, 1972)
Flow Detention Organic-N(mg/l)
up Type of Sample
1 :00 p.m. grab
Temp.
(C
>C)
-
fte. P.
(gPn
0.
I/ ft )
44
Time Inf,
Eff. Inf
(min)(l) Total Sol. Total Sol. mg/1
30
_
TIME
NH -N
Eff.
mg/1
8.0
Percent
Remov a 1
-
Filter oxygen failure between day 118 and 122 (length of time unknown).
124
129
137
144
2:00 p.m. grab
24 hr composite
2:00 p.m. grab
4:00 p.m. grab
2:00 p.m. grab
1
1
Before day 157 the filter
160
165
172
180
187
194
2:00 p.m. grab
24 hr composite
1 2:00 noon grab
24 hr composite
1 1 :00 a.m. grab
24 hr composite
1 1 :00 a.m. grab
After 4 days of idle
24 hr composite
11 :00 a.m. grab
During day 1 85 and 1 £
24 hr composite
1 1 :00 a.m. grab
1
1
1
1
8
-
9
-
-
was
7
-
7
-
8
-
5
aerobic
1
-
8
0.
0.
0.
0.
0.
44
44
44
44
44
anaerobic
0.
0.
0.
0.
0.
0.
0.
44
44
44
44
44
44
44
conditions
0.
0.
36 the filter
1
-
7
0.
0.
44
44
30
30
30
30
30
(solids very black)
30
30
30
30
30
30
30
(day 175 to 179).
30
30
was without any influent
22
22
60
60
16
16
5.81 2.12 23
6.67 2.52 19
15
for 1 to 7 days.
31
19
21
18
19
17
14
19
18
waste or oxygen feed.
17
17
.3
.8
.9
.0
.5
.2
.3
.7
.6
.0
.7
.3
.3
.3
.8
.7
14.1
13.6
18.3
25.5
9.0
25.9
18.3
17.6
8.6
14.0
11.3
7.7
14.2
9.6
3.0
2.3
13-
19
15
-
42
20.
5
19
59.
26.
36
46
26
47
83
87
5
2
0
0
(1) Based on untreated waste flow rate and filter void volume.
-------
TABLE C-10
MISCELLANEOUS DATA FOR BUBBLE OXYGENATION FILTER AT 30 MINUTE DETENTION TIMEfl )
(November 26, 1971 - February 10, 1972)
Alkalinity BOD5(mg/l) OOD(mg/l) S.S.
Dsys , DO - -. ...-.-..i,.. ..-.. ,.,..... ... -' ' ' '- ... i . i. ii ... -..
Aft.OT. mg/l as CaCO., ,, inf. Eff. Inf. Eff.
After -61" "" ""W3 Eff. J-nj- ^1£- J-nj" ^^ Inf. Eff.
Start-up Inf. Eff. mg/l Total Sol. Total Sol. Total Sol. Total Sol. mg/l mg/l
118 _ . - _ --_-.-_._
Filter oxygen failure between day 118 and 122 (length of time unknown).
124 329 313 28.8 - _._ -___
129 290 267 - 34(36) ... 134 63 - 45 57(38)
260 212 23.4 55(39) - 20.4 5.3 142 64 100 - 70(52) 53
137 322 372 17.4 67(47) 17.3 26.5 5.9 133 84 59 - 73(44) 49
eg 144
Before day 157 filter was anaerobic (solids very black) for 1 to 7 days.
160 312 298 - - - - - -
165 320 310 - - - - - -
314 284 31.0 - ----._-
172 - - -- ..- .___
22.8 - .__ ____
180 390 330 ... _
326 293 28.8 - - -
After 4 days of idle aerobic conditions (day 175 to 179).
187 364 318 ...
344 290 21.2 - - - - -
During day 185 and 186 the filter was without any influent waste or oxygen feed.
194 - - -- ___ _._
341 204 28.4 - __. __._
(1 ) Data shown in parenthesis refers to samples collected and tested by Union Sanitary
District (influent pilot plant sampler tended to collect too many solids).
-------
TABLE D-1
PREOXYGENATION FILTER (4)
(Grab Samples Every 2-Hours Over a 24-Hour Period)
(Detention Time - 60 Minutes (l)j Recycle Ratio 2.75 (2); After
pH Alkalinity DO NHo-N
Date Temp.
(1972) Hour (°C)
7/22 8 p.m.
7/22 10 p.m.
7/22 Midnight
7/23 2 a.m.
7/23 4 a.m.
7/23 6 a.m.
7/23 8 a.m.
7/23 10 a.m.
7/23 Noon
7/23 2 p.m.
7/23 4 p.m.
7/23 6 p.m.
Average:
Composite
Sample:
27
25
23
23
23
23
23
23
23
24
26
26
24
Inf.
7.45
7.45
7.50
7.65
7.45
7.50
7.50
7.45
7.40
7.50
7.50
7.50
7.49
Eff.
7.13
7.10
7.30
7.20
7.20
7.20
7.15
7.15
7.15
7.20
7.15
7.05
7.17
Inf.
mg/1
358
352
358
345
344
351
34=4=
350
338
364
374
372
354
Eff.
mg/1
234
238
240
240
241
244
245
259
260
252
240
243
245
245
Inf.
mg/1
31.6
32.0
32.6
32.8
33.2
32.2
33.2
32.8
32.4
32.4
31.8
30.8
32.3
(3) Eff.
mg/1
5.6
8.4
10.2
10.8
11.2
11.8
13.0
13.6
13.6
9.2
6,0
5.6
9.9
5.6
79 Days
Inf. Eff. Percent
mg/1 mg/1 Removed
13.6 1.3
13.0 0.90
12.3 0.90
12.0 0.80
12.0 0.40
11.4 0.80
10.3 1.0
9.3 0.40
10.7 0.50
17.0 1.0
19.0 1,2
18.0 1.2
13.2 0.87
0.1
90
93
93
93
96
93
90
96
94
94
94
93
93
of Operation)
NOp-N NO,-N
t-j J
Eff.
mg/1
0.50
0.38
0.36
0.36
0.36
0.32
0.32
0.28
0.26
0.44
0.62
0.58
0.4
0.08
Eff.
mg/1
15.0
14.5
14.1
15.3
15.1
14.3
13.3
12.8
12.6
14.6
16.1
"17.3
15.0
14.1
(l ) Based on untreated waste flow rate and filter void volume.
(2) Recycle Ratio = recycle flow rate/waste flow rate.
(3) Dissolved oxygen of diluted influent waste (filter entrance)^
Total Oxygen Used = (recycle ratio + l)(lnf. DO - Eff. DO).
(4) Unless otherwise defined inf. = undiluted and untreated waste.
-------
TABLE D-2
o
BUBBLE OXYGENATION FILTER
Date
(1972) Hour
11/23 4:00 p.m.
11/23 6:00 p.m.
11/23 8:00 p.m.
11/23 10:00 p.m.
11/23 Midnight
11/24 2:00 a.m.
11/24 4:00 a.m.
11/24 6:00 a.m.
11/24 8:00 a.m.
11/24 10:00 a.m.
11/24 Noon
11/24 2:00 p.m.
Average:
Composite Sample:
Temp.
,20
19
19
18
18
17
17
16
17
18
19
19
18
(Grab Samples Every 2-Hours Over a 24-Hour Period)
(Detention Time - 60 Minutes (1)^ After 116 Days of Operation)
AH i- -,. NE-.-N NO -N N00-N
pH Alkalinity DO 3 23
Inf.
-
7.65
7.65
7.55
7.58
7.62
7.55
7.50
7.55
7.53
7.50
7.60
7.57
Eff.
-
6.90
6.90
7.00
7.00
7.10
7.10
7.15
7.10
7.15
7.10
7.08
7.05
Inf.
mg/1
376
362
356
346
346
340
336
333
326
322
334
360
343
Eff.
mg/1
248
212
224
232
234
230
234
234
234
234
229
211
230
Eff.
mg/1
18.4
20.6
24.4
24.8
26.6
27.0
28.2
29.6
30.8
31 .6
28.4
24.2
26.2
Inf.
mg/1
18.7
15.8
13-0
13-0
13-0
12.3
12.0
13-6
10.7
9.3
14.0
18.7
13.7
13.7
Eff. Percent
mg/1 Removed
6.1
1.88
1 .06
0.75
0.81
0.75
0.87
0.81
0.87
0.69
1..19
1.56
1 . 44 /.
(1.02)1
67
88
92
94
94
94
93
94
92
92
91
92
$3)(8:
Eff.
mg/1
0.60
0.60
0.45
0.45
0.42
0.40
0.40
0.40
0.35
0.30
0.37
0.55
, 0.44
Eff- 0 i
7l Remarks
mg/1
18.4 1-1/2 hrs.
after back-
1Q 4_ wash.
I C/ » *±
17.8
16.9
17.0
15.6
15.3
18.8
18.0
17.3
14.5
19.5
17.4
(1 ) Based on untreated waste flow rate and filter void volume.
(2) Not counting data affected by backwashing (4:00 to 6:00 p.m.).
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
w
Field Study of Nitrification with the Submerged Filter
Donald D. McHarness
Perry L. McCarty
Stanford University
Stanford, California
12. Srxnsorir Organ- at/on' Environmental Protection Agency
Environmental Protection Agency report
number, EPA-R2-73-158, February 1973.
5 Koport Lime
C
3, f, form ij Org&
Kept, No
i. Cr.nffact/GrantNo.
17010 EPM
iC Typt ,'/ Kept- in3
Period Copied Research
5-31-71 to 6-1-72
This study demonstrated the feasibility of a column packed with one-inch rock
media to retain nitrifying organisms on the media surface. Kinetic rates of the
nitrification reaction in secondary effluent, using two modes of oxygen aeration,
were studied.
Successful and reliable nitrification of secondary activated sludge effluent
was demonstrated in this field study using a pilot size packed media column. Ninety
percent reduction of ammonia nitrogen and residual BOD and suspended solids of less
than 10 mg/1 was obtained with a detention time of one hour.
Two methods of oxygen introduction were evaluated. One system involved pre-
oxygenation with pure oxygen at one atmosphere of pressure, and required recycle
of treated effluent because of the limited oxygen solubility. This system achieved
the greatest efficiency of BOD and solids removal, and was most reliable. This
system did have a tendency to clog at high influent solids levels.
The other system, which employed direct bubbling of oxygen into the column,
was only slightly less efficient and did not suffer from the clogging tendencies
of the recycle system.
17a. Descriptors
^Nitrification, #Biological Treatment, ^Oxygen, Municipal Waste, Biological Solids
l"h. Identifiers
#stage treatment, ^packed column, field evaluation, alkalinity, temperature effect
KK Fifld & Orotif Q5 D
';' '"-. 1-3: 'Security Class.
. 'Repor ,'
'5; SV'ff/yC' .,s.
?/. Wo. of
Pagen
Pt ..e
Send To :
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 2O24O
,,..,.. ,,. E. F. Earth ..,-,, NERC- Cincinnati
------- |