WATER POLLUTION CONTROL RESEARCH SERIES
17050DJS05/71
OXYGEN CONSUMPTION
IN
CONTINUOUS BIOLOGICAL CULTURE
U.S. ENVIRONMENTAL PROTECTION AGENCY
-------
WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our Nation's waters. They provide a central source of
information on the research, development and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts with Federal,
State, and local agencies, research institutions, and
industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, B.C. 20^60.
-------
OXYGEN CONSUMPTION IN CONTINOUS
BIOLOGICAL CULTURE
by
Center for Research, Inc.
Ihe University of Kansas
Irving Hill Road West Campus
Lawrence, Kansas 66044
for the
ENVIRONMENTAL PROTECTION AGENCY
Grant WP01023-03
Project #17050 EJS
May, 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $125
-------
EPA Review Notice
This report has been reviewed by the EPA, and approved
for publication. Approval does not signify that the
contents necessarily reflect the views and policies of
the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute
endorsement or recommendation for use.
ii
-------
ABSTRACT
A continuous flow automatically recording respirometer was
used to study the response of aeration only and aeration
with sludge return completely mixed activated sludge systems
to step changes in the influent substrate. The experiments
were conducted at 25°C with glucose; a mixture of glucose,
glutamate, and acetate; and a mixture of sewage solids plus
Metrecal.
Influent substrate concentrations were doubled in the 3-hour
and tripled in the 6-hour mean residence time aeration only
experiments without increasing the soluble COD in the effluent.
Larger shocks produced temporary COD peaks in the effluent.
These increases were accompanied by peaks in the oxygen up-
take rate in cultures metabolizing the soluble substrates.
The mixture of sewage solids and Metrecal did not produce
a distinct peak in oxygen demand during transient operation.
Decreases in the influent substrate concentrations produced
rapid decreases in the rate of oxygen utilization.
Concentration increases of up to 7.2 in the influent did not
produce a change in the effluent soluble COD of aeration with
sludge return units. This was not the maximum limit for the
process.
A procedure for calculating the rate of oxygen uptake by
a CMAS system at any time during a step transient was devel-
oped.
This report was submitted in fulfillment of Project Number 17050 DJS,
under the partial sponsorship of the Water Quality Office, Environmental
Protection Agency.
1X1
-------
CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Introduction 5
IV Equipment Design 19
V Experimental Procedures 33
VI Aeration Only Activated Sludge Systems 39
VII Aeration With Sludge Return Activated
Sludge Systems 77
VIII Engineering Significance 91
IX Acknowledgements 101
X References 103
XI Publications and Patents 107
XII Glossary 109
XIII Appendices 117
v
-------
FIGURES
No.
1 Flow Diagram for Completely Mixed Activated
Sludge System Showing Food and Discharge
Distribution 12
2 Flow Diagram for Completely Mixed Activated Sludge
System Showing Suspended Solids Distribution 12
3 Change in Components of Mixed Liquor Volatile
Suspended Solids in a Completely Mixed Activated
Sludge System as the Sludge Age is Varied 16
4 Schematic Diagram of Respirometer Used for
Aeration Only Experiments 20
5 Schematic Diagram of Respirometer Used for
Aeration With Sludge Return Experiments 21
6 Electrolysis Cell Designed for Use With Respiro-
meter 25
7 Schematic Diagram of Digital Printout Accumulator
and Printout System Used With Respirometer 27
8 Parameter Response for a Transition from 494 to
719 mg/L Influent COD, Glucose Waste, 3-Hour Mean
Residence Time 41
9 Parameter Response for a Transition from 252 to
907 mg/L Influent COD, Glucose Waste, 3-Hour Mean
Residence Time 43
10 Summary of Changes in Oxygen Uptake Rate in Re-
sponse to Step Increases in the Influent, Glucose
Waste, 3-Hour Mean Residence Time 44
11 Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Glucose Waste, 3-Hour Mean Residence
Time 45
12 Summary of Changes in Oxygen Uptake Rate in Re-
sponse to Step Increases in the Influent, Glucose
Waste, 6-Hour Mean Residence Time 46
-------
FIGURES (Con't)
No. Page
13 Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Glucose Waste, 6-Hour Mean Resi-
dence Time 47
14 Parameter Response for a Transition from 730 to
242 mg/L Influent COD, Glucose Waste, 6-Hour
Mean Residence Time 49
15 Summary of Changes in Oxygen Uptake Rate in Re-
sponse to Step Increases in the Influent, Com-
posite Waste, 3-Hour Mean Residence Time 54
16 Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Composite Waste, 3-Hour Mean
Residence Time 55
17 Summary of Changes in Oxygen Uptake Rate in
Response to Step Increases in the Influent,
Composite Waste, 6-Hour Mean Residence Time 56
18 Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Composite Waste, 6-Hour Mean
Residence Time , 57
19 Parameter Response for a Transition from 228 to
1480 mg/L Influent COD, Composite Waste, 6-Hour
Mean Residence Time 59
20 Parameter Response for a Transition from 1480 to
258 mg/L Influent COD, Composite Waste, 6-Hour
Mean Residence Time 61
21 Parameter Response for a Transition from 189 to
1200 mg/L Influent COD, Synthetic Sewage, 3-Hour
Mean Residence Time 66
22 Summary of Changes in Oxygen Uptake Rate in Re-
sponse to Step Increases in the Influent, Syn-
thetic Sewage, 3-Hour Mean Residence Time 68
23 Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Synthetic Sewage, 3-Hour Mean
Residence Time 69
VII
-------
FIGURES (Con't)
24 Summary of Changes in Oxygen Uptake Rate in
Response to Step Increases in the Influent,
Synthetic Sewage, 6-Hour Mean Residence Time 70
25 Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Synthetic Sewage, 6-Hour Mean
Residence Time 71
26 Summary of the Suspended Solids Observations
for the Upward Transients Conducted at the 3-Hour
Mean Residence Time for the Composite Waste 74
27 Summary of Changes in Food to Mass Ratios for
the Upward Transients Conducted at the 3-Hour Mean
Residence Time for the Composite Waste 75
28 Parameter Response for a Transition from 135 to
508 mg/L Influent COD, Composite Waste, 3-Hour
Mean Residence Time, Aeration with Sludge Return 79
29 Partial Summary of Changes in Oxygen Uptake Rate
and Effluent Soluble COD in Response to Step
Increases in the Influent, Composite Waste, 3-Hour
Mean Residence Time, Aeration with Sludge Return 81
30 Partial Summary of Changes in Oxygen Uptake Rate
and Effluent Soluble COD in Response to Step
Increases in the Influent, Composite Waste, 3-Hour
Mean Residence Time, Aeration with Sludge Return 82
31 Parameter Response for a Transition from 269 to
1035 mg/L Influent COD, Composite Waste, 6-Hour
Mean Residence Time, Aeration with Sludge Return
System 85
32 Partial Summary of Changes in Oxygen Uptake Rate
and Effluent Soluble COD in Response to Step
Increases in the Influent, Composite Waste, 6-Hour
Mean Residence Time, Aeration with Sludge Return 86
33 Relationship Between Synthesis and Basal Oxygen
Uptake Rate During a Step Transient 93
Vlll
-------
TABLES
No. Page
1 Variations in Wastewater Characteristics 6
Reported by Loehr
2 Hourly Changes in BOD Loading for Wahoo,
Nebraska, Observed on July 7-8, 1966 by
Tilsworth 7
3 Temperature Effect on the Metabolism, Synthesis,
and Endogenous Respiration Factors Reported by
McKinney 18
4 Pumping Rates and Chemical Concentrations Used
in Respirometer Oxygen Calibration Tests 28
5 Results Obtained in Calibrating the Respirometer
Against Standard Sodium Sulfite Solutions 30
6 Components Used to Construct the Respirometers
Used in This Research 31
7 Percent Total Oxygen Demand Contribution of the
Waste Components used in the Aeration Only
Experiments 34
8 Nutrient Concentrations used in the Aeration
Only Experiments 37
9 Nutrient Concentrations used in the Aeration
Plus Sludge Return Experiments 34
10 Substrates Used in Developing Activated Sludge
Cultures for the Aeration Only Experiments 39
11 Summary of Glucose Waste Transients Investigated
in the Aeration Only System 40
12 Summary of Oxygen Uptake Peaks Observed in the
Aeration Only Experiments Conducted on Glucose
Waste 42
13 Summary of Time Required to Establish Steady State
Oxygen Uptake Rates After a Step Decrease in In-
fluent Glucose Concentration 48
14 Comparison of Observed and Predicted Steady State
Suspended Solids Concentration and Oxygen Uptake
Rate, Glucose Waste, 3 Hour Mean Residence Time 51
IX
-------
TABLES (Con't)
No. Page
15 Comparison of Observed and Predicted Steady
State Suspended Solids Concentration and Oxygen
Uptake Rate, Glucose Waste, 6-Hour Mean Residence
Time 52
16 Summary of Composite Waste Transients Investi-
gated in the Aeration Only System 53
17 Summary of Oxygen Uptake Peaks Observed in the
Aeration Only Experiments Conducted on the Com-
posite Waste 58
18 Summary of Time Required to Establish Steady
State Oxygen Uptake Rates After a Step Decrease
in Composite Waste Concentration 60
19 Comparison of Observed and Predicted Steady State
Suspended Solids Concentration and Oxygen Uptake
Rate, Composite Waste, 3-Hour Mean Residence Time 63
20 Comparison of Observed and Predicted Steady State
Suspended Solids Concentration and Oxygen Uptake
Rate, Composite Waste, 6-Hour Mean Residence Time 64
21 Summary of Synthetic Sewage Transients Investi-
gated in the Aeration Only System 62
22 Observed Steady State Suspended Solids and Oxygen
Uptake Rates for Synthetic Sewage 72
23 Food to Mass Ratios Observed at the Transition
From Exponential to Declining Growth for the
Glucose and the Composite Wastes 73
24 Summary of 3-Hour Mean Residence Time Transients
Conducted on the Aeration with Sludge Return
System 78
25 Summary of Oxygen Uptake Rate and Suspended
Solids Concentrations for the 3-Hour Mean Resid-
ence Time Aeration with Sludge Return Experiments 83
26 Summary of 6-Hour Mean Residence Time Transients
Conducted on the Aeration with Sludge Return
System 84
-------
TABLES (Con't)
No. Page
27 Summary of Oxygen Uptake Rates and Suspended
Solids Concentrations for the 6-Hour Mean
Residence Time Aeration with Sludge Return
Experiments 88
28 Organic Loading Rates Imposed on the Continuous
Flow Aeration with Sludge Return Activated
Sludge Systems 89
29 Summary of Observed and Predicted Oxygen Uptake
Rates for the 6-Hour Mean Residence Time System,
Composite Waste 96
30 Summary of Observed and Predicted Oxygen Uptake
Rates for the 3-Hour Mean Residence Time System,
Composite Waste 97
XI
-------
SECTION I
CONCLUSIONS
1. The continuous flow respirometer used in this research
is an effective instrument for measuring oxygen utilization
by biological cultures.
2. Doubling the substrate concentration in the influent
will not increase the soluble chemical oxygen demand (COD)
in the effluent of an aeration only completely mixed acti-
vated sludge system (CMAS) operating on a 3-hour mean
residence time at 25°C.
3. A new steady state oxygen utilization rate is establish-
ed within 3 hours after starting the transients cited in
conclusion two.
4. A3 fold increase in influent substrate concentration
will not increase the soluble COD in the effluent of a 6
hour mean residence time aeration only activated sludge
system metabolizing soluble substrates. The evidence is
inconclusive for systems operating on complex substrates
containing colloidal material, but the upper limit appears
to be approximately a 2 fold increase.
5. A new steady state oxygen utilization rate is establish-
ed within 5 hours after starting the transients cited in
conclusion four.
6. Step increases in the influent larger than those cited
in conclusions 2 and 4 will produce transient peaks of
soluble chemical oxygen demand in the reactor effluent. The
magnitude of these peaks is proportional to the magnitude
of the increase in the influent and the complexity of the
substrate.
7. When cultures, grown on simple soluble substrates, are
subjected to transients larger than those cited in con-
clusions 2 and 4, a transient peak in the rate of oxygen
utilization will be produced. Cultures grown on complex
substrates containing colloidal material will not produce
a peak in oxygen demand.
8. Step decreases in the influent of aeration only CMAS
systems result in a rapid decrease in the rate of oxygen
utilization. A new steady state is usually established
within 3 hours.
9. Aeration only CMAS systems having mean residence times
-------
of 6 hours or less can be useful as pretreatment installa-
tions. However, most plant scale applications will require
the use of a second treatment process to reduce the concen-
tration of soluble COD in the effluent.
10. Completely mixed activated sludge (CMAS) systems with
solids recycle can handle large step increases in soluble
organic loading without an increase in the soluble COD in
the effluent. Step increases of up to 7.2 times did not
produce a change in the effluent soluble COD. This was not
the maximum limit, however, because the system was not
loaded to failure.
11. Loading rate is one of the critical factors in the
production of filamentous growth in CMAS systems with solids
recycle. Under some conditions loading rates greater than
0.7 pound of COD per day per pound of mixed liquor suspend-
ed solids (MLSS) produced filamentous growth. The mean
residence time in the aeration basin and the concentration
of MLSS were also found to influence the growth of filamen-
tous microorganisms.
12. A method for calculating the oxygen utilization rate
for aeration only and aeration with sludge recycle CMAS
systems at any time during a step transient was developed.
-------
SECTION II
RECOMMENDATIONS
Additional research should be conducted on the oxygen up-
take response of completely mixed activated sludge (CMAS)
systems with solids recycle. The objective of this in-
vestigation should be the development of a kinetic model
which will respond to transient loading conditions.
The technique developed in this research for predicting
oxygen utilization of CMAS systems should be evaluated
on field scale installations operating under transient
conditions.
-------
SECTION III
INTRODUCTION
Historical Review
Since the development of the concept of activated sludge
by E. Arden and W. T. Lockett in 1914, the process has
undergone numerous modifications. Most of these changes
have been introduced in an attempt to improve operational
stability. In many instances*the basis for these stability
problems has been the rate of oxygen utilization by the bio-
logical culture. This is because, in the final analysis,
a functionally stable activated sludge installation is one
which will maintain an aerobic environment for the micro-
bial population. This does not mean that some modifications
of the process are not capable of undergoing temporary
periods of anaerobis without experiencing failure. The
literature is replete with accounts where plants have con-
tinued to operate under periodic oxygen limiting conditions.
However, in almost all instances when this occurs, the
ability of the process to successfully respond under adverse
stresses is compromised. It is therefore important for
the designer to avoid anaerobic conditions when possible.
Oxygen limitation in the activated sludge process will
occur because of variations in environmental conditions in
the aeration basin. The most significant variables are
temperature and changes in influent flow rate or concen-
tration of biodegradable organic material. Within the
continental United States, the sewage temperature can be
expected to vary between 5°C and 35°C. Oxygen limitation
normally becomes a critical factor only at higher temper-
atures. Variations in influent flow rates and nutrient
concentrations for a number of widely scattered municipali-
ties have been compiled by Eckhoff and Jenkins (1). Four
to five fold variations between the maximum and minimum
daily flow were reported. Organic loading, expressed as
biochemical oxygen demand (BOD) or suspended solids (SS),
showed ten to twenty five fold daily variations. A summary
of the findings reported by Loehr (2) on the variation of
wastewater characteristics with time is reproduced in
Table 1. The hourly changes in BOD loading observed by
Tilsworth (3) for the city of Wahoo, Nebraska, 1960,
population 3610, are summarized in Table 2. The maximum
influent BOD was 480 mg/L while the minimum was 30 mg/L.
The conditions illustrated in Table 1 and Table 2 indicate
plant-scale activated sludge plants are continuously sub-
jected to transient or shock loadings.
-------
Table 1. Variation in Wastewater
Characteristics Reported by Loehr (2)
Monthly (b)
80 to 120
70 to 120
80 to 120
Daily (c)
80 to 110
50 to 150
50 to 200
Flow
BOD5 (a)
Suspended solids
Hourly (d)
50 to 140
25 to 220
25 to 220
(a) Based on mg/1
(b) Percentage of the average month within a year
(c) Percentage of average day within a week
(d) Percent of the average hour within a day
-------
Table 2. Hourly Changes in BOD Loading for Wahoo, Nebraska,
Observed on July 7-8, 1966 by Tilsworth (3)
Time
8
9
10
11
12
13
14
15
16
17
18
19
BOD c
Ib/hr
23
51
73
82
74
63
68
64
52
55
50
39
% of Previous
Hour
222
143
112
90
85
108
94
81
106
91
78
Time
20
21
22
23
24
1
2
3
4
5
6
7
8
BOD5
Ib/fir
43
36
27
22
19
18
12
7
4
3
5
10
30
% of Previous
Hour
110
84
75
81
86
95
67
58
57
75
167
200
300
-------
Scope of Project
As pointed out by Gaudy and Englebrecht (4), three types
of transients are possible in activated sludge systems.
These are quantitative shifts in the concentration of
nutrients in the influent; qualitative loads caused by
changes in the chemical composition of the waste; and toxic
shock produced by the addition of substances inhibitory to
biological growth. Quantitative transients have the great-
est potential for producing oxygen stress on a system be-
cause the culture is acclimated to the substrate and can
react rapidly to increases in the influent nutrient. This
research was therefore confined to investigating culture
behavior in response to quantitative changes in selected
wastes.
The complete mixing modification of the activated sludge
process provides maximum hydraulic protection from all
types of shock loading because the aeration basin functions
as a surge basin to dampen the effect of changes in the
influent. This provides operational stability from a micro-
biological and an oxygen utilization standpoint because
conditions change uniformly throughout the aeration basin
This research was therefore confined to aeration only and
aeration with sludge return,complete mixing activated
sludge systems.
The aeration only system was investigated because it offered
an opportunity to observe the response of a mixed biological
culture to externally imposed changes in growth conditions
without the masking effect of recycle sludge.
A second reason for examining the aeration only system is
its potential as an advanced waste treatment process. As
pointed out by Tenney et a_l (5) (6), short term aeration
followed by chemical flocculation, sedimentation and solids
dewatering has potential for simultaneously removing organic
carbon, nitrogen, and phosphate. The potential of this
approach can be enhanced by the joint use of alum for the
chemical precipitation of phosphate and the use of poly-
electrolytes for flocculation of microorganisms (6).
The complete mixing, with sludge recycle, modification
of the activated sludge process was investigated because
it has been demonstrated to be an exceptionally stable and
efficient process for use in secondary waste treatment.
McKinney ejt al (7) reported the average five-day BOD removal
efficiency for the CMAS plant at Grand Island, Nebraska, to
be 94 percent in 1967, 95 percent in 1968, and 98 percent in
1969. Ninety-nine percent removal was attained for 2.5
months of normal operation in 1969 (7).
-------
Previous Investigations
A great quantity of research, has been conducted on con-
tinuous cultures during the last thirty five years. Numer-
ous mathematical models describing the kinetics of these
systems are available in both microbiological and sanitary
engineering publications. Excellent reviews of this liter-
ature have been compiled by Agnew (8) and Chun (9). There-
fore only a brief review of the concepts of models pertinent
to this report will be presented herein. A comprehensive
bibliography on continuous culture is presented in Appendix
A.
The early work in continuous culture was done by micro-
biologists who were primarily interested in aeration only
steady state systems. The classical kinetic model used to
describe these systems was developed by Monod (10), and by
Novick and Szilard (11). The model is based upon two basic
postulates:
A. The cell yield factor is constant
B. The specific growth rate for a culture can
be defined by a single continuous function
The yield factor (Y) is defined by:
,,» Y _ dry weight of cells formed
weight of substrate utilized
Considerable controversy has been generated over this post-
ulate. Herbert et al (12) reported a varying yield factor
when the dilution rate was increased. Rickard and Gaudy (13)
observed decreasing cell yield with increasing liquid tur-
bulence. Hetling et al (14) demonstrated cell yield varied
with substrate, organTim, and detention time. Gaudy and
Gaudy (15) in reviewing the literature, reported cell
yield was not constant.
Much of the confusion regarding cell yield can be explained
by considering the growth state of the culture. The amount
of biological protoplasm observed in a culture is the net
result of two opposing processes, synthesis and endogenous
metabolism. When food is not limiting, the relatively rapid
synthesis reaction predominates producing exponential growth
conditions and the yield factor appears to be constant. How-
ever, under food limitation, declining growth is observed and
a balance is established between the rate of synthesis and
the rate of endogenous respiration. Under these conditions
the apparent yield factor is determined by the growth con-
ditions externally imposed on the culture. In the activated
sludge process, hydraulic detention and sludge recycle are
used to operate the system. The yield factor observed in a
-------
particular installation is therefore a function of these
two process variables.
The specific growth rate ( 0 ) was defined by Monod (10) as:
(2) 0 =
where p
0
KS+S
= maximum specific growth rate
= substrate concentration in the
reactor
K = substrate concentration when
the specific growth rate is
one half the maximum specific
growth rate
The specific growth rare equation is an empirical relation-
ship which best described, for Monod, the growth rate ob-
served in batch systems. Modifications to the relationship
have been proposed by Teissier (16) , Schulze (17) , and
Contois (18) . However, the Monod equation has remained
dominant in the field because it is relatively simple,
and because it permits the calculation of specific growth
rate throughout the entire range of externally imposed
growth conditions. This latter feature is especially appeal-
ing from the standpoint of mathematical model development.
Pert (19) was one of the few microbiologists to investigate
the effects of dissolved oxygen concentration on continuous
cultures. He studied the metabolism of glucose by an
Aerobacter species and developed the following relation-
ship for steady state oxygen utilization.
al
= - PDS
where -577 = oxygen utilization rate
P = oxygen demand constant
D = reactor dilution rate
S0 = influent substrate concentration
1Q
-------
The oxygen demand constant (P) is determined by simultane-
ously measuring the rate of substrate and oxygen utilization
for the culture being studied. The equation is based upon
the Monod concepts for continuous culture.
Garrett and Sawyer (20) first evaluated the use of Monod's
equations for completely mixed activated sludge (CMAS)
systems. They recommended the specific growth rate equation
be expressed as two discontinuous functions one for biologi-
cal mass limiting,and one for food limiting conditions. Be-
cause of solids recycle, activated sludge systems were
found to be food limited. Under food limiting conditions
the growth rate was found to be directly proportional to
the soluble BOD remaining in solution. Similar results
were reported by Hoover and Forges (21) (22) from continuous
flow studies on the treatment of milk wastes.
In 1962, McKinney (23) presented a series of mathematical
relationships for completely mixed activated sludge systems.
The equations were developed for systems operating pre-
dominately in declining growth under food limiting conditions
and considered the effect of endogenous respiration as a
separate constituent in the kinetic balance of the system.
The concepts of Garrett and Sawyer (20) were used to define
growth rate. As originally developed,the equations contain-
ed ten constants to describe three variations of the basic
CMAS treatment process. The modifications considered were:
aeration only, aeration plus sludge return with sludge
wasting in the effluent, and aeration plus sludge return
with separate sludge wasting.
In 1969, McKinney (24) condensed the equations originally
proposed for the three process modifications into one set of
generalized relationships. These new equations assumed that
bacterial activitiy in the final clarifier. did not continue
in direct progression from the aeration tank, as was assumed
in the earlier paper. Only three constants were required.
The modified McKinney equations are used later in this re-
port and are therefore described below.
The flow diagram for an aeration plus sludge return system
with separate sludge wasting is given in Figure 1. A
materials balance around the aeration basin results in the
following rate equations for food.
(4) VdF/dt = QF± - VKmF - (Q+Qr)F + QrF
where V = volume of aeration basin (L)
dF
-rr- = food utilization rate (mg/L/hr)
11
-------
Aeration
Sedimentation
Q
V
Q+Qr
Qr
Q-wQ
Qr+Q
w
Waste
Figure 1. Flow diagram for completely mixed activated
sludge system showing food and discharge
distribution.
Aeration
Sedimentation
M'inf
Miijnf
v
i
Ma,
Mi,
Mar
Me
Mii
, Mer |
Maeff,
Mief f '
Meeff
Miieff
VIaw,Me
w
Mir, Miir
Figure 2. Flow diagram for completely mixed activated
sludge system showing suspended solids
distribution.
12
-------
Q = rate of flow for the raw waste (L/hr)
F. = concentration of BODs in raw waste
1 (mg/L)
K = metabolism constant (temperature
m dependent)
F = concentration of BOD5 in the
effluent (mg/L)
Q = rate of flow for the return sludge
r (L/hr)
The first term on the right-hand side of the equation
represents the increase due to influent food, the second
term represents a decrease in the food due to biological
metabolism, the third term represents the decrease due to
hydraulic displacement, and the fourth term represents
the increase in food due to the return sludge.
At steady state dF/dt = 0, and the equation becomes
(5) F = Fi
Kmt+l
where t = TT = the aeration time based on raw
waste flow (hr)
A similar materials balance for microbial mass around the
aeration basin gives:
(6) VdM /dt = Q-Ma + VK F - VK Ma - (Q+Qr)Ma
£1 i i S *-~
where dMa/dt = rate of change in active mass
(mg/L/hr)
Ma = active microbial mass (mg/L)
Ma = active microbial mass in the re-
r turn sludge (mg/L)
K = synthesis constant (temperature
s dependent)
K = endogenous respiration constant
e (temperature dependent)
The first term on the right-hand side of the equation
represents the increase in active mass due to sludge re-
turn, the second term represents the increase due to cell
growth, the third term represents the decrease due to
13
-------
endogenous respiration, and the fourth term represents
the decrease due to hydraulic displacement.
The active mass in the return sludge (M ) can be expressed
as a fraction ( x) of the total active Mss (Ma). The rate
of flow for the return sludge (Q ) can also be expressed as
a fraction (y) of the influent flow rate (Q) . Making
these substitutions and assuming steady state conditions
so dMa/dt = 0 produces:
Ma -
KSF
McKinney indicates the term — 3T xv is approximately equal
to 1/t where t is the sludge turnover time. Thus equation
7 becomes:
(8)
where t = sludge turnover time (hr)
s
= Ibs MLSS in aeration tank/(lbs SS
in effluent per day + Ibs SS
wasted per day ± Ibs SS change
in mixed liquor per day)
SS = suspended solids
MLSS = mixed liquor suspended solids
It is worthwhile to note in the McKinney approach the
components which make up the total mixed liquor suspended
solids. These are illustrated in Figure 2 where:
M = inert, non-biodegradable organic
inf solids in influent (mg/L VSS)
M = inert, inorganic suspended solids in
inf influent, ash fraction of influent
suspended solids (mg/L SS)
M_ = inert, non-biodegradable organic
suspended solids in the aeration tank
(mg/L VSS)
14
-------
MTT = inert, inorganic suspended solids
in the aeration tank (mg/L SS)
M = endogenous respiration mass
The last three components can be calculated by the
following equations:
(9) M = M (t/t)
1 xnf S
(10)M = M (t /t)+0.1(M +M )
11 inf S a e
(11) Me = 0.2 KeMats
The last term in equation 10 accounts for the inorganic
components present in the non-biodegradable protoplasm
synthesized by the microbial culture. The constant 0.2
included in equation 11 is the fraction of protoplasm syn-
thesized by the culture which is not biodegradable. The
total mass of the mixed liquor suspended solids in the aera-
tion tank is therefore:
(12) MT = Ma + Me + Mi + M..
The solids accounting system given by equation 12 illustrates
the difference between active mass (Ma) and the total mixed
liquor volatile suspended solids (MLVSS) which include
(Ma+Me+MjJ . The active mass (Ma) in an aeration only system
operating in exponential growth is closely approximated
by the mixed liquor volatile suspended solids (MLVSS), but
this approximation begins to deteriorate when the culture
shifts into declining growth. The approximation becomes
grossly in error with the introduction of solids recycle
because of the buildup of endogenous mass and inert organic
material. This is illustrated in Figure 3 for an average
municipal waste being treated at 20°C in a plant with a 3
hour aeration time.
A materials balance around the aeration basin also permits
development of an equation for predicting the oxygen utili-
zation rate in the basin. The dissolved oxygen in the liquid
entering and leaving the basin is neglected in this derivation
because the net effect of these components is negligible. On
this basis, the oxygen utilization rate equation for the
aeration basin is:
15
-------
400Q
E 3000
CTl
U)
73.
"o
CO
v>
3
to
.-=
'£*
200Q
1000
Assumed Conditions
mg/L
T =20°C
Km =7.2/hr
Ks =5.0/hr
Ke =0.02/hr
Figure 3.
IT i 19
Sludge Age (ts) in days
Change in the components of the mixed liquor volatile suspended
solids in the aeration basin of a completely mixed activated sludge
plant as the sludge age is varied.
-------
(13) dO/dt =
-------
Ta,ble 3 ~ Temperature Effect on the Metabolism Synthesia,
and Endogenous Respiration Factors Reported by
McKinney (24)
Temperature
°C
4
6
8
10
12
14
16
18
20
*Des-uruction
Multiplication
Factor
0.34
0.38
0.44
0.50
0.58
0.66
0.76
0.87
1.00
Temperature
°C
22
24
26
28
30
32
34
36
38
Multiplication
Factor
1.15
1.32
1.50
1.75
2.00
2.30
2.65
3.10
*
of the culture starts to occur
transient response to quantitative shock loading. The
work of Storer and Gaudy (26) indicates this approach breaks
down during large transients and a growth rate hystersis,
similar to that proposed by Ferret (27) on theoretical
grounds, occurs.
A more fruitful approach to transient model development
would appear to be based on the concept of a definite
synthesis, not yield, relationship as proposed by McKinney
(24), and by Burkhead and McKinney(28) and; on the postulate
that specific growth rate is limited either by the active
mass or the concentration of food available in the aeration
basin as originally proposed by Garrett and Sawyer (20). The
key to use of this type of model is determining the food to
active mass ratio which controls the specific growth rate
of the system.
Objective of the Project
The objectives of this research were to measure changes in
the rates of oxygen utilization by activated sludge cultures
operated under transient loading conditions and to develop
from these measurements a set of design criteria useful for
sizing oxygen supply systems for field installations.
Development of new mathematical models for continuous
culture systems operating under transient growth conditions
was not undertaken.
18
-------
SECTION IV
EQUIPMENT DESIGN
Basic Concept
A respirometer capable of measuring the oxygen utilization
of a continuous culture was used in this research. Schematic
diagrams of two modifications of the apparatus are given in
Figure 4 and Figure 5. The basic principles of both systems
are identical. The difference between the units being that
one operates as an aeration only system while the second
incorporates secondary sedimentation, sludge wasting, and
sludge return. In both systems,the reactor, or aeration basin,
operates as an externally controlled, constant temperature,
completely mixed vessel. Nutrient is introduced into the
reactor with a constant flow pump. The volume of liquid in
the vessel is held constant by an overflow tube.
The air space above the liquid in the reactor is sealed from
the outside atmosphere. Gaseous carbon dioxide produced
by the culture is removed by reaction with potassium hydrox-
ide. A barometric switch is used to activate the power
supplies used to replenish the oxygen consumed by the culture.
The oxygen is produced by the direct-current electrolysis
of water. The quantity of oxygen produced is measured by
recording the length of time the electrolysis cells operate
over any specified interval.
The concentration of dissolved oxygen in the influent and
within the reactor is continuously measured and recorded by
polarographic electrodes.
The net rate of oxygen utilization by the culture is obtain-
ed by computing the oxygen mass balance of the system over a
specific time interval. This computation takes the form:
(15) 02 (net) = (D0in) (V)-(DOQut) (V)+02(E)±B
where 02 (net) = oxygen used by the culture (mg/min)
DO. = concentration of dissolved oxygen
in in influent (mg/liter)
DO = concentration of dissolved oxygen
out
in reactor (mg/liter)
Q~(E) = oxygen supplied by electrolysis
V = liquid volume pumped through re-
actor (L/min)
19
-------
Switch
C02
Removal
Pump
Effluent
1
Digital Printout
System
I
Power Supply
Electrolysis Cell
Oxygen
Reactor
A
Dissolved 02
Monitor
Dissolved
Monitor
Recorder
Hydrogen
* to
Waste
Sterile Nutrient
Source
Dilution
Water
Pump
Figure 4. Schematic diagram of respirometer
used for aeration only experiments,
20
-------
CO2
Removal
Effluent
Sedimentation
Tube
Return
Sludge
Pump
Waste
Sludge
Switch
Pump
Digital Printout
System
Fbwer Supply
Elect
I Oxygen
Electrolysis Cell
Hydrogen
- to
Waste
Reactor
A
Dissolved
Monitor
Sterile Nutrient
Source
Dilution
Water
Dissolved 02
Monitor
Pump
Recorder
Figure 5. Schematic diagram of respirometer used
for aeration with sludge return experi-
ments .
21
-------
B = correction for change in barometric
pressure (mg/min)
Equipment Details
An adjustable stroke piston pump was used to transfer
liquid into the reactor. A number of laboratory pumps satis-
factory for this application are commercially available. In
some instances, it was also expedient to separate the liquid
being pumped into the reactor into two components to facili-
tate sterilization of the nutrient. When this was done, the
water used to dilute the nutrient contained the trace miner-
als, nitrogen and phosphorous necessary for balanced bio-
logical growth. Constant head valves were generally required
between the liquid storage reservoirs and the suction line
of the pump to maintain a constant rate of flow into the
reactor.
A staisfactory reaction vessel can be constructed by modify-
ing almost any of the commercially available laboratory fer-
mentors. The basic requirements are: the vessel should be
air tight; the temperature within the reactor should be
maintained within plus or minus 0.25°C; and the intensity of
agitation in the liquid should be sufficient to provide
complete mixing and adequate mechanical aeration of the cul-
ture.
Aeration using either surface paddles or draft tubes has
been used successfully. Diffused aeration, using the atmo-
sphere enclosed by the system, was not found to be satis-
factory because slight variations in the pumping rate of the
gas produced significant errors in the barometric switch
used to control the oxygen supply.
The effluent from the reactor overflowed through a "U" tube
to a sampling port and then to a waste sump. The bottom
of this tube was mixed with a magnetic stirrer to prevent
settling of the biological solids. It is relatively simple
to design an overflow tube which maintains equal concentra-
tions of suspended solids in the reaction vessel and in the
effluent when the biological solids are either discrete or
flocculent particles.
The gaseous carbon dioxide produced by the culture was re-
moved by recirculating the gas in the reactor through a
series of two scrubbers each containing 700 milliliters of 10
Normal potassium hydroxide solution. A diaphram pump was
satisfactory for this purpose. A water trap was installed
between the final gas scrubber and the reactor to prevent
the caustic solution from being carried into the reactor.
22
-------
The gas adsorption train was installed in a water bath
which was maintained at the temperature of the reactor to
prevent thermally induced volume change in the recirculated
gas.
The concentration of dissolved oxygen in the influent and
in the reactor was continuously measured with polarographic
electrodes which were separated from the liquid by a gas per-
meable membrane. A multi-channel recorder provided a per-
manent record of these observations.
Most commercially available dissolved oxygen electrodes re-
quire a minimum liquid velocity past the membrane of approx-
imately 1.8 feet per second. This velocity was easily
attained in the reactor but could not be obtained in the in-
fluent line unless a small mixing chamber was provided. A
satisfactory chamber was constructed by mounting a small
cylindrical container on a magnetic stirrer. The measuring
probe was inserted through the top of the cylinder directly
above the stirring bar.
The electrodes measure the dissolved oxygen tension in the
liquid. These measurements can be converted to dissolved
oxygen concentration by calibrating the electrodes in a
solution of the culture media. The "Short Theriault Modifi-
cation" of the Winkler method (29) was found satisfactory
for this purpose.
The oxygen used by the biological culture was supplied by
the electrolysis of water, Milazzo (30). A group of power
supplies, each attached to an individual electrolysis cell,
was used to provide discrete increments of gas production
until the rate of oxygen demand by the culture was satisfied.
Operation of the power supplies was controlled by a null
point manometric switch. When oxygen was consumed by the
culture,the pressure dropped in the reactor and lowered the
electrolyte level in the atmospheric arm of the manometer.
This broke electrical contact across the switch and turned
on power supplies sequentially until sufficient oxygen was
being produced to restore the original atmospheric pressure
in the reactor. In practice this meant that one or more
electrolysis cells operated continuously with intermittent
operation from an additional unit.
A number of direct-current power supplies satisfactory for
this application are commercially available. The basic re-
quirements are: the power supply should provide a constant
direct-current with variable voltage; the output of the power
supply should be regulated within plus or minus 0.5 milli-
amperes; and the circuitry of the power supply should be
solid state to minimize response time when the unit is turned
on.
23
-------
The use of a manometric switch to control the operation of the
power supplies necessitated the use of a correction factor
to compensate for changes in atmospheric pressure during an
experiment. This correction was readily computed once the
temperature of the experiment was selected and the average
volume of the gas enclosed in the respirometer was measured.
A standard commercial recording barograph provided a permanent
record of atmospheric pressure change which was of satis-
factory accuracy for computing this correction.
The electrolysis cells used in the apparatus are shown in
Figure 6. Each ampere-hour of current flow through the
cell produced 0.037 grams of hydrogen gas at the cathode and
0.298 grams of oxygen gas at the anode. The anode consisted
of 20 feet of 0.7 millimeter diameter nickel wire wrapped
around a 4 millimeter diameter glass rod 8.5 inches long.
This rod was enclosed within a plastic drying tube which had
been slotted lengthwise throughout its circumference. The
outside of the drying tube was wrapped with 20 feet of one
millimeter iron cathode wire. The entire assembly was sus-
pended in a large test tube filled with an electrolyte of
7.6 Normal potassium hydroxide solution. The oxygen gas
produced at the anode was connected to the reactor. The
hydrogen gas produced at the cathode was vented to the atmo-
sphere .
Cells of the type shown in Figure 6 were operated at currents
up to 2 amperes for periods of up to 2 years without discern-
able physical deterioration or current drift. A potential
of approximately 3.5 volts was required across the cell.
Current efficiency is defined as the observed weight of
oxygen produced by an electrolysis cell divided by the the-
oretical weight of oxygen which should have been produced in
accordance with Faraday's law. The current efficiency of
the cells shown in Figure 6 was measured by collecting the
oxygen produced during a 15 minute time period in a burette
filled with a saturated sodium chloride solution. The range
in current efficiency observed during five trials was from
99.2 to 100 percent. The average of all observations was
99.7 percent.
The composition of the gas collected at the anode was also
measured with a gas chromatograph. Less than 0.01 percent
hydrogen gas contamination was observed.
The period of operation of each power supply was recorded
with a digital accumulator and printout system designed by
A.R.F. Products of Raton, New Mexico. A block diagram show-
ing the major components of this system is shown in Figure 7,
The time of day clock has a visual dial and is also directly
connected to the printer. The minimum time increment is
24
-------
to Reactor
H2 to Waste
Plastic
Drying
Tube
Test
Tube
Cathode
Rubber
Stopper
76 N KOH
Asbestos
Cloth
Figure 6, Electrolysis Cell Designed for Use
With the Respirometer
25
-------
hundredths of hours. The elapsed time accumulator visually
displays, and sends to the printer on demand, the total time
each power supply operates within a specified time interval.
However, rather than simply recording the time of operation,
the unit is calibrated to provide a direct tabulation of the
milligrams of oxygen produced by each electrolysis cell.
The accumulator can also clear the values displayed for any
power supply in the system. This may be done manually or
may be done automatically at the end of a specified time in-
terval.
The multiplexer consists of a variable timer and the cir-
cuitry necessary to transfer readings from the elapsed
time accumulator to the printer. Time intervals of from
one to sixty minutes can be selected. However, a 15 minute
interval was found to provide sufficiently detailed inform-
ation for the majority of experiments. A more complete des-
cription of the accumulator, multiplexer, and digital print-
out system has been provided by Baker (31).
The digital printer provides a permanent record of the
oxygen produced by electrolysis. This record together with
the record of the concentration of dissolved oxygen enter-
ing and leaving the reactor and the record of the change in
barometric pressure provided all of the data necessary to
make an oxygen mass balance.
A check on the accumulative accuracy for all of the com-
ponents connected with the oxygen supply system of the
respirometer was made by comparing the observed versus the
theoretical oxygen consumption of a standardized solution of
sodium sulfite. Four trials were conducted. In the first
3 the volume of the liquid in the reactor was 5.19 liters.
In trial 4 the volume of the liquid was 9.25 liters. In
all trials the sodium sulfite and the cobaltous chloride
solutions were prepared separately and combined in the re-
actor. This was accomplished in trials 1 and 2 by adding
cobaltous chloride to the distilled water in the reactor to
make solutions of 157 mg/L and 552 mg/L as cobalt respect-
ively. These initial concentrations were based upon main-
taining a catalyst concentration in the reactor greater
than 10 percent of the incoming sulfite concentration during
the 6 hours over which the tests were conducted. In trials
3 and 4 the chemical solutions were pumped into the reactor
which initially contained distilled water. A summary of
the operating variables is given in Table 4.
Sulfite was measured by the non-referee method C given in
the ASTM Manual on Industrial Water and Industrial Waste
Water (J^).A nitrogen atmosphere was maintained over the
sulfite solution during standardization and storage. Dis-
solved oxygen was measured with a polarographic membrane
26
-------
From Power; ^
Supplies
to
Elapsed Time Accumulator
Multiplexer
Sequencer
Time Interval
Selector
Manual
Controls
Time-of-Day Clock
Figure 7. Schematic diagram of digital accumulator and print-
out system used with the respirometer.
-------
Table 4 - Pumping Rates and Chemical Concentrations
Used in Respirometer Oxygen Calibration Tests
to
00
Trial
1
2
3
4
Pumping Rate L/hr
Sulfite
1.73
1.73
. 1.75
2.65
Cobalt
0
0
0.89
0.40
Influent Concentration mg/L
Sulfite
208
725
1390
1500
Cobalt
*
*
140
160
*batch addition, see explanation in text
-------
electrode calibrated against the Axide Modification of the
lodometric Method (29).
The results of the test are summarized in Table 5.
The values shown in Table 5 are of interest in that they
illustrate the precision of the apparatus while also showing
how sulfite measurements can be used as an independent check
on the performance of individual components in the system.
This is illustrated in trials 1 through 3 which were con-
ducted under identical environmental conditions with the
only variable being the concentration of the influent sulfite
solution. The consistently indicated overproduction of
oxygen by the respirometer and the relative decrease in over-
production as the concentration of the sulfite solution in-
creased, strongly implies one of the power supplies providing
the base-line oxygen supply was incorrectly adjusted and
was not providing sufficient current to the elctrolysis
cell to produce the oxygen indicated on the time accumulator.
This resulted in the power supply, which responded to the
small intermittent pressure drops in the reactor, operating
more often and produced an over-estimate for oxygen utili-
zation. While the absolute magnitude of this error was
constant, the net effect was less pronounced as the concentra-
tion of sulfite was increased and additional power supplies
were used to produce the required oxygen. Unfortunately,
trial 4 can not be included in this hypothesis because a
larger reactor was used and supplemental power supplies
were required to provide the rate of oxygen production needed
to oxidize the sulfite solution.
Solids separation was obtained by a tube settler designed
for a 2-hour liquid retention time. Sludge recycle was
done with an adjustable flow piston pump connected to the
bottom hopper of the tube settler. Sludge wasting was not
done from the sludge return line because a constant sludge
concentration could not be maintained. Accurate control of
the mixed liquor suspended solids (MLSS) was obtained by
wasting mixed liquor collected from the effluent of the
aeration basin.
A summary of the equipment used in constructing the re-
spirometers is given in Table 6. The identification of
specific manufacturers in Table 6 is for illustration only
and does not constitute the endorsement of the products
mentioned.
29
-------
Table 5 - Results Obtained in Calibrating the Respirometer Against
Standard Sodium Sulfite Solutions
CO
o
Trial
No.
1
2
3
4
Sulfite
Oxygen
Demand
Entering
Reactor
mg/hr
72
250
487
795
Dissolved
Oxygen
Leaving
Reactor
mg/hr
4
1
8
28
Total
Oxygen
Production
Required
mg/hr
76
251
495
823
Oxygen
Production
Indicated
on
Respirometer
Printout
mcf/hr
81
264
497
843
Percentage
Difference
107
105
100
102
-------
Table 6 - Components Used to Construct the Respirometers
Used in This Research
Components
Manufacture
Nutrient and Dilution
Water Pump
Dissolved Oxygen
Analyzer
Recorder for Dissolved
Oxygen Measurements
Reactor
7.5 Liter Capacity
Reactor
12 Liter Capacity
Constant Current Power
Supplies
Digital Accumulator and
Printout System
Atmospheric Recirculation
Pump
Sludge Recirculation
Pump
Model 1521 Harvard Metering
Pump
Model 778 Beckman Process
Oxygen Analyzer
Electronik 16 Honeywell
Multi-Channel Recorder
Microfirm Fermentor Series
MF-100, New Brunswick
Scientific Company
Model 40-100 Fermentor,
The Virtis Company
Models ABC15, ABC18, and
CK18, Kepco, Inc.
A.R.F. Industries,
Raton, New Mexico
Model 2 Neptune Dyna-Pump
Model RRP2G150, FMI
Lab Pump
31
-------
SECTION V
EXPERIMENTAL PROCEDURES
Substrate Selection and Preparation
The problem of choosing substrates which can be prepared.
and standardized in the laboratory, yet at the same time
yield information useful for field application, is one which
has plagued activated sludge research for decades. The
compounds used in this research were selected with the
objective of determining differences in the response of
cultures grown on simple carbon substrates with those grown
on complex mixtures of carbon compounds.
Glucose was selected as the single carbon source for one
series of the aeration only experiments because of the large
number of investigations available in the literature which
are based on this compound. A second waste used in the
aeration only experiments was composed of a mixture of glu-
cose, glutamic acid, and acetic acid. This waste had been
studied by Burkhead (33) and was considered to be represent-
ative of the soluble portion of domestic sewage. The third
waste used in this series was a mixture of the supernatant
from settled primary sewage sludge and a diet food, Metrecal.
A summary of the percent total oxygen demand (TOD) of the
various waste components is given in Table 7.
During the aeration only experiments, the glucose and the
carbon compounds used in the composite waste were prepared
as concentrated solution, and acidified to a pH between 2.0
and 3.0. Iron, as ferrous sulfate, was added and the mixture
autoclaved at 15 psig for 15 minutes. These sterile solutions
were pumped separately to the reactor.
The separation of the carbon substrate from the remainder
of the waste resulted in a stable mtrient source throughout
the course of the experiment. One additional benefit which
resulted from this approach was that iron could be readily
held in solution in the acidified substrate. Previous re-
searchers (34)(35) had reported the precipitation of iron
and other trace metals when substrate, nutrients, and trace
metals were combined. No precipitation was observed in the
carbon substarte containers in this research. Occasional
measurements of soluble iron in the reactor effluent during
the experiments indicated a minimum of 0.4 mg/L of iron present.
The supplemented sewage used in the aeration only experiments
was prepared by collecting approximately 10 liters of primary
sewage sludge from the sewage treatment plant at Lawrence,
Kansas.. The sludge was homogenized in a Waring Blender by
mixing in the proportion of about 1 part sludge to 3 parts
of tap water. This material was then refrigerated for 24
33
-------
Table 7 - Percent Total Oxygen Demand Contribution of the
Various Waste Components used in the Aeration
Only Activated Sludge Experiments
Waste
Name
Carbon
Compounds
% TOD
Contribution
Glucose
Glucose
100
Composite
Glucose
Glutamic Acid
Acetic Acid
40
50
10
Synthetic
Sewage
Supernatant from Settled
Primary Sewage Sludge
Metrecal
19*
81*
* Percentages based on Chemical Oxygen Demand (COD) rather
than TOD
Table 9 - Nutrient Concentrations in the Influent Waste
Use in the Aeration Plus Sludge Return Activated
Sludge Experiments
Aeration
Time
Hours
3
3
3
3
6
6
6
6
TOD of
Waste
mg/L
250
500
750
1000
250
500
750
1000
Nitrogen
mg/L
as N
33.7
67.3
101.0
134.7
42.8
85.6
128.4
173.2
Phosphorous
mg/L
as P
3.0
6.1
10.1
13.1
3.9
7.7
11.6
15.4
Iron
mg/L
as Fe
4
4
4
4
4
4
4
4
Buffer
mg/L
as HC03
87.1
87.1
87.1
87.1
112.4
112.4
112.4
112.4
34
-------
hours at 5°C. The supernatant was decanted off, thoroughly
mixed, and divided into two 20 liter containers. The solution
in each container was then supplemented with 570 milliliters
of Metrecal to produce a total concentration of 10.7 grams/
liter as chemical oxygen demand (COD). These stock solutions
were refrigerated at 5°C until used.
The water used to dilute the influent carbon solutions of
all three wastes was prepared from Lawrence, Kansas, tap-
water to which nitrogen, as ammonium chloride; phosphorous,
as potassium acid phosphate; and buffer, as sodium bicarbon-
ate; had been added. A summary of the nutrient concentra-
tions for each influent waste is given in Table 8. It
should be noted that iron was not added to the synthetic
sewage mixture because it was present in the Metrecal.
The only waste used in the aeration with sludge return ex-
periments was the mixture of 40 percent glucose, 50 percent
glutamic acid, and 10 percent acetic acid used as one of
the carbon sources in the aeration only experiments. In
this instance, however, the mixture was not acidified. Iron
was maintained in solution at 4 mg/L as iron by chelation
with sodium citrate using a citrate to iron weight ratio
of ten to one. The stock solutions were sterilized by auto-
claving and pumped separately to the reactor.
The water used to dilute the influent carbon solution was
prepared from Lawrence, Kansas, tapwater to which nitrogen,
as ammonium sulfate; phosphorous as dibasic potassium phos-
phate; and buffer, as sodium bicarbonate; had been added. A
summary of the nutrient concentrations used for each experi-
mental condition is given in Table 9. The dilution water
and the influent carbon source were changed simultaneously
at the start of a transition.
Analytical Techniques
The analytical tests used to supplement the oxygen utili-
zation measurements collected in this research were: total
suspended solids; chemical oxygen demand; biochemical oxygen
demand; pH; standard plate count; and microscopic examina-
tion of the sludge.
Suspended solids were determined by the membrane filter
technique described by Engelbrecht and McKinney (36).
Metricel G.A.-6 filters with a nominal pore size of 0.45
microns were used. Prior to use, each filter was washed with
100 milliliters of demineralized water, placed in an alumi-
num weighing dish, and dried at 103°C for 1 hour. After
cooling for 1 hour in a dessicator, the aluminum dish and
filter were weighed on a type HIS Metller balance. The same
35
-------
drying and weighing procedure was used after the sample was
placed on the filter. The precision of the test was checked
by replicating 7 trials on a mixed liquor suspended solids
sample. The sample mean was 808 mg/L with a standard
deviation of ±9.8 mg/L.
The chemical oxygen demand was performed as outlined in
Standard Methods (29) f°r tne 10 milliliter sample size.
Due to the differences in concentration between the influent
wastes and the soluble effluent from the reactor it was
necessary to use two modifications of the test. The standard
test was used on the influent. The precision of the tech-
nique was determined by 10 replications on a sample with an
average COD of 772 mg/L. The standard deviation for these
tests was ±7 mg/L or 0.9 percent of the mean. The precision
of the dilute test was determined by 10 trials on a sample
with an average COD of 37.5 mg/L. The standard deviation
was ±3.3 mg/L or 8.8 percent of the mean.
The biochemical oxygen demand test was performed as outline
for the dilution bottle method' in Standard Methods (29).
Effluent from the settling tube was used as seed. Tests
for precision were not performed.
The pH was measured with a Beckman Model H pH meter. This
parameter was monitored to determine if the reaction kinetics
during a transition were influenced by pH.
The standard plate count, using serial dilution and spot
plate innoculation techniques, was used to determine the
change in viable organism concentrations during one series
of transitions. Tryptone glucose extract agar incubated at
35°CI 0.5°C for 24 ±2 hour, as specified in Standard Methods
(29), was used in making these measurements. Use of the
tryptone glucose extract agar in all probability resulted
in lower organisms counts than use of a nonselective medium
such as the activated sludge extract agar of Prakasam and
Dondero (37). However, measuring the absolute number of
organisms present was not considered as important in this
research as determining the relative change in organism
concentration. The technique suggested in Standard Methods
was therefore, used in the interests of simplicity and
replicability.
Microscopic examination was conducted at 100 and 350
magnification on all cultures used in the research. The
purpose of these examinations was to determine the types and
relative numbers of bacteria, fungi protozoa, rotifiers, and
both free swimming and stalked ciliates present in the
culture.
36
-------
Table 8 - Nutrient Concentrations in the Influent Wastes Used in
Both the 3 and the 6-Hour Aeration Only Activated Sludge
Experiments*
TOD of waste
mg/L
250
500
750
1000
1500
Nitrogen
mg/L as N
83
83
83
166
166
Phosphorous
mg/L as P
18.9
18.9
18.9
37.8
37.8
Iron**
mg/L as Fe
2
2
2
2
2
Buffer
mg/L as HC03
360.6
360.6
360.6
721.2
721.2
*When a transition was made from 250 to 1000 mg/L COD or from 250 to
1500 mg/L TOD, the dilution water was changed to provide the nutrient
concentration called for by the higher strength waste at least two
detention times prior to the start of the transition.
**See text for comment on iron concentration used in the synthetic
sewage waste
-------
SECTION VI
AERATION ONLY ACTIVATED SLUDGE SYSTEMS
Experimental Conditions
The aeration only studies were conducted in a completely
mixed reactor having a liquid volume of 5.28 liters. Aera-
tion and mixing was done with an upflow draft tube. Pumping
was provided by three paddles operating in series along a
vertical shaft located in the center of the tube. The paddle
speed was 475 revolutions per minute. The volume of gas en-
closed in the respirometer was 2.27 liters. Carbon dioxide
produced by the culture was removed by recirculating this
gas through a solution of 10.7 N potassium hydroxide at of
60 ± 10 liters per hour. All tests were conducted at
25 ± 0.25°C.
The activated sludge cultures used were developed by combin-
ing approximately 5 liters of fresh settled municipal sewage
with the material shown in Table 10.
Table 10. Substrates used in Developing Activated
Sludge Cultures for the Aeration Only
Experiments.
1.0 gm/L of the carbon source to be studied
0.38 gm/L Ammonium Chloride
0.10 gm/L Potassium Acid Phosphate
0.63 gm/L Sodium bicarbonate
0.01 gm/L Ferrous Sulfate
280 mL of tap water
This mixture was added to the reactor and aerated as a
batch system until the exogenous food supply, measured as
soluble COD, was consumed. The reactor was then started
as a continuous flow system and operated for a minimum of
18 hydraulic mean residence times before starting an
experiment. This procedure was very satisfactory for culture
acclimation.
Glucose Waste
Fifteen step transient experiments were conducted with the
glucose waste. The combinations studied are summarized in
Table 11.
39
-------
Table 11. Summary of Glucose Waste Transients
Investigated in the Aeration Only System
3-Hour Mean Residence Time
Influent COD mg/L
6-Hour Mean Residence Time
Influent COD mg/L
480 to 250
720 to 260
770 to 275
275 to 494
494 to 719
252 to 747
747 to 250
252 to 907
728 to 481
458 to 725
730 to 242
240 to 735
246 to 498
247 to 950
234 to 1405
Two distinctive response patterns were observed for step
transients involving an increase in influent substrate
concentration. The reaction illustrated in Figure 8 is
typical of culture response up to approximately a 2 fold
substrate increase at the 3-hour mean residence time. This
same pattern was observed for up to approximately a 3 fold
substrate increase at the 6-hour mean residence time. Over
this range of loading the culture was capable of processing
the increase in substrate as fast as it entered the reactor
and no increase in soluble COD was observed in the effluent.
The increase in total COD and in mixed liquor suspended
solids was approximately equal to the hydraulic wash in rate
for a completely mixed reactor. However, there was very
definitely a shift in the growth state of the culture.
This was indicated by the rapid increase observed in oxygen
utilization. A new steady state oxygen uptake rate was
normally established within approximately one hydraulic
mean residence time after the start of the transient.
Step increases larger than those cited above produced a
response typical to the one illustrated in Figure 9. Under
these conditions, substrate entered the reactor faster than
the culture could metabolize it and a buildup of soluble
COD occurred. This produced exponential growth conditions
until the active mass of microorganisms was sufficient to
metabolize both the incoming substrate and the food stored
in the reactor. Exponential growth continued until the ex-
cess substrate in the reactor was consumed and a new steady
state balance was established. The increase in oxygen utili-
zation in this type of transition was very rapid and continued
40
-------
o Total COD
• Soluble COD
• Oxygen Uptake
A Suspended Solids
4 8
Time After Transition (Hours)
Figure 8. Parameter Response for a Transition from 494 to
719 mg/L Influent COD, Glucose Waste, 3 Hour Mean
Residence Time
-------
until equilibrium was reestablished in the system. This
resulted in an oxygen uptake peak which was significantly
greater than the rate of oxygen utilization observed under
steady state conditions.
Summaries of the oxygen uptake response and the correspond-
ing change in soluble COD in the reactor are given in Figures
10 through 13 for all of the step increases conducted on
the glucose waste. The reason for the oxygen uptake plateau
which occurs from 1 to 3 hours after the start of the trans-
itions illustrated in Figure 12 is not known. However, the
explanation may be a shift in species predomination within
the culture.
The magnitude of the observed oxygen uptake peaks are
summarized in Table 12.
Table 12. Summary of Oxygen Uptake Peaks Observed in
the Aeration Only Experiments on Glucose
Waste
Mean Residence
Time
Hours
3
3
6
Magnitude of
Change in
Influent COD
mg/L
252 to 747
252 to 907
234 to 1405
Peak
Oxygen
Uptake
mg/L/hr
112
155
117
*Peak Oxygen Uptake Rate , ,
Final Steady State Oxygen Uptake Rate x
Percentage of
Steady State
Oxygen
Uptake*
119
132
133
)0
The response of an activated sludge culture to a step de-
crease in influent substrate concentration is illustrated
in Figure 14. No change was observed in the effluent soluble
COD. The decrease in total COD and in the mixed liquor sus-
pended solids was approximately equal to the hydraulic wash
out rate for a completely mixed reactor. The rapid change
in oxygen uptake rate again indicated there was definitely a
shift in the growth state of the culture. In both the 3 and
the 6 hour mean residence time systems a new steady state
oxygen uptake rate was usually established within 3 hours.
These findings are summarized in Table 13.
42
-------
240 -
o Total COD
• Soluble COD
• Oxygen Uptake
Suspended Solids
10
14
Time After Transition (Hours)
Figure 9.
Parameter Response for a Transition from 252 to 907 mg/L
Influent COD Glucose Waste, 3 Hour Mean Residence Time
-------
180
o
X
(0
O)
•>
0)
.*
CO
0)
120
I 60
••••••
1
-2 0
Figure 10.
/ ••. _
275 to 494 mg/L
• ••• 252 to 747 mg/L
...... 252 to 907 mg/L
10
14
18
Time, Hours
Summary of Changes in Oxygen Uptake Rate in Re-
sponse to Step Increases in the Influent, Glucose
Waste, 3 Hour Mean Residence Time
-------
Ul
500
P300
Q
O
0
,22
.n
"o
CO
c
-------
180
o
o
O)
0)
CO
c
Q)
§?
x 60
240 to 735 mg/L
—- 246 to 498 mg/i
••••• 247 to 950 mg/L
— 234 to 1405 mg/L
-2
JL
10
Time, Hours
14
18
Figure 12.
Summary of Changes in Oxygen Uptake Rate in Re-
sponse to Step Increases in the Influent, Glucose
Waste, 6 Hour Mean Residence Time
-------
200
150
c
o
u
o> 100
JO
"o
0)
50
240to 735 mg/L
246 to 498 mg/L
...... 247to 950 mg/L
234 to 1405 mg/L
tAf——m—~!mlf—~Hf * * * *
-2
O
10
Time, Hours
14
Figure 13. Summary of Changes in Soluble COD Concentration in the
Reactor in Response to Step Increases in the Influent,
Glucose Waste, 6 Hour Mean Residence Time
-------
Table 13. Summary of Time Required to Establish
Steady State Oxygen Uptake Rates After A
Step Decrease in Influent Glucose Con-
centration
Mean Residence
Time
Hours
3
3
3
3
6
6
Magnitude of Change
in Influent COD
Concentration
mg/L
480 to 250
720 to 260
770 to 275
747 to 250
728 to 481
730 to 242
Time Required
to Establish
Oxygen Steady
State , Hours
2.05
2.87
2.90
3.47
2.43
2.08
The predominate organisms present in the >hour mean
resident time cultures were highly dispersed bacteria.
Some small, free swimming ciliated protozoa were also
present. No settling could occur in samples after one hour
of quiescent sedimentation. The filterability of the mixed
liquor through a 0.45 micron pore size filter was very poor.
Up to 50 minutes were required to filter a 15 milliliter
sample at the higher suspended solids levels.
The predominate organisms present in the 6-hour mean resi-
dent time cultures were fungi. Some small clumps of bacter-
ia were also present. Free swimming ciliates were the pre-
dominate higher organisms. Some clarification could be
obtained by sedimentation. The filterability of the mixed
liquor was markedly better than that obtained at the 3 hour
mean residence time.
Standard plate counts using the spot technique were taken
during the first 6 hours of the 246 to 498 mg/L COD step
increase in the 6-hour mean residence time experiment.
The concentration of viable microorganisms increased from
125xl06 to 200xl06 per milliliter. The increase in mixed
liquor suspended solids during the same interval was 155
to 195 mg/L. These observations indicate the microorganisms
were dividing rapidly and the average mass per cell was
48
-------
vo
220
200 -
660
-2
Figure 14,
- 540
- 420
o Total COD
• Soluble COD
• Oxygen Uptake
Suspended Solids
- 3OO
- 180
en
E
in
.•g
'o
(/)
T3
0>
XJ
Q)
a
01
c/J
"§
-------
decreasing.
Plate counts were also taken during the first 3 hours of
the 720 to 260 mg/L COD step decrease in the 3-hour mean
residence time experiment. The concentration of viable
microorganisms decreased from 150x 106 to 120xl06 per
milliliter while the mixed liquor suspended solids de-
creased from 250 to 150 mg/L. The measurements indicate
some inert mass was apparently in the system because the
average cell mass is larger than would be normally antici-
pated. However, the decrease observed in the computed mass
per cell fits the reaction expected in a starving culture.
The observations collected for suspended solids and oxygen
uptake rate for all periods of steady state operation have
been compared with the values predicted for these parameters
by the equations developed by McKinney (24). In making
these comparisons the influent COD measurements were con-
verted to biochemical oxygen demand (BOD) by the BOD to total
oxygen demand (TOD) ratio of Sawyer et al (38) and the COD
to TOD ratio of Ballanger et ajL (39) . Th"e conversion factor
used was:
(16) BOD5 =0.76 COD (Glucose)
The conversion factor used on the first term of equation
13 was also adjusted because it assumes the BODs is 66.7
percent of the ultimate BOD. The work of Sawyer et al
(38) indicates the BODs of glucose is 70 percent of the
ultimate BOD. The results obtained are presented in Table
14 and Table 15.
The scatter between the predicted and observed suspended
solids concentrations is random and within the experimental
error associated with COD and SS measurements. The oxygen
uptake predictions show a negative bias at the 3-hour
mean residence time and positive bias at the 6-hour mean
residence time. The source of this systematic error is
probably associated with the conversion factor associated
with the second term in equation 13. Burkhead and Waddell
(40) have shown the compositions of activated sludges are
not constant but vary depending upon the stage of growth
and the particular organic substrate utilized. This effect
can become particularly significant when single carbon
source wastes, such as glucose, are being evaluated. How-
ever, correcting for this effect was not considered germane
to the objective of this research.
Composite Waste
Sixteen step transient experiments were conducted with the
50
-------
Table 14. Comparison of Observed and Predicted Steady
State Suspended Solids Concentration and Oxygen
Uptake Rate for the Glucose Waste, 3-Hour
Mean Residence Time
Influent
COD
mg/L
480
250
720
260
770
275
494
719
252
747
907
Predicted
SS
mg/L
232
121
349
125
373
133
240
349
123
361
439
Observed
SS
mg/L
247
137
260
125
325
113
245
341
129
318
449
% Error
- 6.1
-11,7
+34.2
0
+14.8
+17.7
- 2.0
+ 2.3
- 4.7
+13.5
- 2.2
Predicted
°2
mg/L/hr
57
30
85
31
91
32
58
85
29
89
108
Observed
02
mg/L/hr
57
31
83
35
90
36
63
93
34
94
117
% Error
0
- 3.2
+ 2.4
-11.4
+ 1.1
-11.1
- 7.9
- 8.6
-14.7
- 5.3
- 7.7
-------
Table 15. Comparison of Observed and Predicted Steady
State Suspended Solids Concentration and
Oxygen Uptake Rate for the Glucose Waste/
6-Hour Mean Residence Time
Influent
COD
mg/L
728
481
458
725
730
242
240
735
246
498
247
950
234
1405
Predicted
SS
mg/L
333
221
210
333
333
112
109
337
112
228
112
434
109
644
Observed
SS
mg/L
341
187
187
328
338
120
124
320
-
267
126
415
117
678
% Error
- 2.3
+18.2
+12.3
+ 1.5
- 1.5
- 6.7
-12.1
+ 5.3
-
-14.6
-11.1
+ 4.6
- 6.8
- 5.0
Predicted
02
mg/L/hr
51
33
32
50
51
17
17
51
17
35
18
66
16
98
Observed
°2
mg/L/hr
43
31
27
47
46
15
16
44
17
33
16
70
16
88
% Error
+18.6
+ 6.5
+18.5
+ 6.4
+10.9
+ 13.3
+ 6.2
+15.9
0
+ 6.1
+12.5
- 5.7
0
+11.4
en
to
-------
composite waste. The combinations studied are summarized
in Table 16.
Table 16. Summary of Composite Waste Transients
Investigated in the Aeration Only System
3- Hour Mean Residence Time
Influent COD mg/L
214 to 411
411 to 194
194 to 651
652 to 480
478 to 717
717 to 245
245 to 974
974 to 241
241 to 1460
253 to 750
6- Hour Mean Residence Time
Influent COD mg/L
250 to 504
504 to 235
235 to 736
226 to 1480
1480 to 258
258 to 1003
Transient response was very similar to that exhibited by
the glucose waste. Two fold step increases at the 3 hour
mean residence time and 3 fold step increases at the 6 hour
mean residence time produced responses similar to those
illustrated in Figure 8. Larger step increases resulted
in the leakage of soluble COD in the reactor effluent and
produce transient peaks in the oxygen uptake rate.
Summaries of the oxygen uptake response and the correspond-
ing change in soluble COD in the reactor are given in
Figure 15 through 18. The most interesting transition was
the one from 226 to 1480 mg/L COD at the 6 hour mean resi-
dent time. Complete data for this experiment is illustrated
in Figure 19. The plateau in oxygen utilization observed
in the glucose runs was present. In addition, two temporary
decreases in oxygen uptake occured at about 8.8 and 10.6
hours after the start of the transition. Each of these
decreases was approximately one hour in length. These
small peaks, superimposed on the general oxygen utilization
response, suggest possible sequential substrate removal as
discussed by Gaudy et al (41). This possibility should
be more fully investigated.
53
-------
-------
Ul
Q
O
u
JD
1
LU
500 -
300 -
100 -
214 to 411 mg/L
194 to 651 mg/L
245 to 974 mg/L
• • • • • 241 to 1460 mg/L
253 to 750 mg/L
Figure 16,
Time, Hours
Summary of Changes in Soluble COD Concentration
in the Reactor in Response to Step Increases in
the Influent, Composite Waste, 3-Hour Mean
Residence Time
-------
180
250 to 504 mg/L
— 235 to 736 mg/L
•••• 226 to 1480 mg/L
• • • 258 to 1003 mg /L
0120
•
t
ui
60
-L
1
JL
-2
Figure 17,
2 6 10 14 is
Time, Hours
Summary of Changes in Oxygen Uptake Rate in Response
to Step Increases in the Influent, Composite Waste,
6 Hour Mean Residence Time
-------
400
X
O)
E 3OO
Q
O
O
I 200
c
03
100
-2
.••
0
1 250to 504 mg/L
---- 235 to 736 mg/L
226 to 1480 mg/L
• • • t • 258 to 1003 mg/L
•••••••••••••••••••••••••'«•«>.••.
1O
14
Time, Hours
Figure 18. Summary of Changes in Soluble COD Concentration in
the Reactor in Response to Step Increases in the
Influent, Composite Waste, 6 Hour Mean Residence Time
-------
The magnitude of the observed oxygen uptake peaks are
summarized in Table 17.
Table 17. Summary of Oxygen Uptake Peaks Observed in
the Aeration Only Experiments Conducted on
the Composite Waste
Mean Residence
Time
Hours
3
3
3
6
6
Magnitude of
Change in
Influent COD
mg/L
194 to 651
253 to 750
245 to 974
248 to 1003
226 to 1480
Peak
Oxygen
Uptake
mg/L/hr
98
114
140
102
151
*Peak Oxygen Uptake Rate ,QO
Final Steady State Oxygen Uptake Rate
Percentage of
Steady State
Oxygen
Uptake*
110
123
120
150
137
The transition from 253 to 750 mg/L COD at the 3-hour mean
residence time was made specifically to evaluate the
effects of oxygen limiting conditions. At the start of the
experiment the partial pressure of oxygen in the reactor
was lowered so dissolved oxygen levels approaching zero
would be observed during the peak demand period. The concen-
tration of dissolved oxygen decreased to 0.5 mg/L 3.5 hours
after the start of the transition and remained below this value
for approximately 3.5 hours. The minimum concentration obser-
ved was 0.1 mg/L which occurred for one hour during the period
of peak oxygen uptake rate by the culture. On the basis of
the data prssented in Table 17 and Table 19, it did appear
the period of low dissolved oxygen concentration did not have
a deleterious effect on the system. Thabara, and Gaudy (42)
have reported partial culture failure during transient con-
ditions in a glucose system operating on an 8-hour mean re-
sidence time.
The response to a step decrease in influent substrate is
illustrated in Figure 20. Culture behavior was identical to
that observed for the glucose waste with a new steady state
oxygen uptake rate usually established within 3 hours. The
major exception to this rule was the decrease from 1480 to
58
-------
20O -
O
X
U)
CM
c i?n —
en
vo
(0
c
03
03
X
O
- 720
- 560
o Total COD
• Soluble COD
• Oxygen Uptake
Suspended Solids
880
- 400
- 240
o
CO
TJ
0)
§,
5T
c/3
T3
eo
§
o
Figure 19,
12 20
Time After Transition (Hours)
Parameter Response for a Transition from 226 to
1480 mg/L Influent COD, Composite Waste, 6-Hour
Mean Residence Time
-------
to 258 mg/L COD which required 4.72 hours.
are summarized in Table 18.
These findings
Table_ 18. Summary of Time Required to Establish
Steady State Oxygen Uptake Rates After
a Step Decrease in Composite Waste Con-
centration.
Mean Residence
Time
Hours
3
3
3
3
6
6
Magnitude of Change
in Influent COD
Concentration
mg/L
411 to 194
652 to 480
717 to 245
974 to 241
504 to 235
1480 to 258
Time Required
to Establish
Oxygen Steady
State, Hours
1.29
2.88
3.08
2.85
1.30
4.72
Actinomycetes, fungi, and small clumps of bacterial floe
were observed in the 3-hour mean residence time cultures.
Free swimming ciliates were the predominant higher organism.
A small shift in predomination by fungi occured in the 6-
hour mean residence time culture.
Sedimentation did not occur in the 3-hour culture but was
present to some degree in the 6-hour system. The filter-
ability of the 6 hour culture was very good with from 30
seconds to 3 minutes required to dewater 15 milliliters of
MLSS.
The observations collected for suspended solids and oxygen
uptake rate for all periods of steady state operation have
been compared with the values predicted for these parameters
by the equations developed by McKinney (24) . In making
these comparisons the influent COD measurements were con-
verted to biochemical oxygen demand (BOD) by the BOD to total
oxygen demand (TOD) ratio of Sawyer et al (38) and the COD
to TOD ratio of Ballanger et a_l (39) for the glucose and
the glutamic acid. Adjustment for the acetic acid was
based on the BOD to TOD ratio of Gaf fney and Heukelekian (43) ,
The computed conversion equation was:
60
-------
CTl
180 -
- 1000
o Total COD
• Soluble COO
• Oxygen Uptake
A Suspended Solids
-2 0
Figure 20
6 10
Time After Transition (Hours)
14
18
Parameter Response for a Transition from 1480 to 258 mg/L
Influent COD, Synthetic Sewage, 6 Hour Mean Residence Time
-------
(17) BOD5 =0.77 COD (Composite)
This agrees well with the experimentally measured coefficient
of 0.76.
The conversion factor on the first term in equation 13 was
adjusted in this instance because the work of Sawyer et al
(38) indicates the BOD- of a mixture of glucose and glutamic
acid is 69.6 percent of the ultimate BOD. The results ob-
tained are given in Table 19 and Table 20.
The suspended solids measurements associated with 258 and 736
mg/L COD in Table 20 appear to be in error. With these ex-
ceptions, the scatter between the predicted and observed sus-
pended solids concentrations in both tables is within expected
experimental error.
The predicted oxygen uptake values have a consistent negative
bias in both tables. This probably reflects an error in the
conversion factor adjustment in equation 13. Use of the 1.5
conversion results in a consistent positive bias of approxi-
mately the same magnitude.
Synthetic Sewage - Seven step transients were conducted with
the synthetic sewage. The combinations studied are summar-
ized in Table 21.
Table 21. Summary of Synthetic Sewage Transients
Investigated in the Aeration Only
System.
3-Hour Mean Residence Time
Influent COD mg/L
6-Hour Mean Residence Time
Influent COD mg/L
249 to 433
233 to 690
233 to 864
189 to 1200
214 to 316
176 to 615
169 to 1420
1410 to 190
The process used to prepare the synthetic sewage produced
a solution which contained a significant concentration of
62
-------
Table 19. Comparison of Observed and Predicted Steady
State Suspended Solids Concentration and
Oxygen Uptake Rate, Composite Waste, 3-Hour
Mean Residence Time
Influent
COD
mg/L
214
411
194
651
478
717
245
974
241
1460
253
750
Predicted
SS
mg/L
105
201
95
318
234
351
121
477
119
715
123
367
Observed
SS
mg/L
100
191
110
323
223
280
106
448
122
733
124
321
% Error
+ 5.0
+ 5.2
-13.6
- 1.5
+ 4.9
+25.4
+14.2
+ 6.5
- 2.5
- 2.5
- 0.8
+14.3
Predicted
°2
mg/L/hr
26
50
24
80
58
86
29
117
29
176
31
90
Observed
02
mg/L/hr
28
54
28
89
62
93
36
117
31
179
34
93
% Error
- 7.1
- 7.4
-14.2
-10.1
- 6.5
- 7.5
-19.4
0
- 6.4
- 1.7
- 8.8
- 3.2
-------
Table 20. Comparison of Observed and Predicted Steady State
Suspended Solids Concentration and Oxygen Uptake
Rate, Composite Waste, 6-Hour Mean Residence Time
Influent
COD
mg/L
250
504
235
736
226
1480
258
1003
Predicted
SS
mg/L
116
251
109
341
105
685
120
464
Observed
SS
mg/L
114
205
94
255
113
626
84
398
% Error
+ 1.7
+22.4
+16.0
+33.7
- 7.0
+ 9.4
+42.9
+16.6
Predicted
mg/L/hr
18
38
17
52
16
105
19
71
Observed
°2
mg/L/hr
18
36
19
58
19
110
23
68
% Error
0
+ 5.6
-10.5
-10.3
-15.8
- 4.5
-17.4
+ 4.4
-------
colloidal particles. This presented experimental difficul-
ties because the metering pumps used to add the waste to the
reactor were frequently clogged by the particulate material.
This problem was especially acute during the 3-hour mean
residence time experiments because the waste was pumped as
the concentrated solution. The problem was partially
alleviated in the 6-hour mean residence time transients by
mixing the concentrated waste with the dilution water and
pumping the mixture.
The data obtained with substrate were well worth the experi-
mental problems, however, because they clearly illustrate
differences between the reaction kinetics of cultures utiliz-
ing relatively simple soluble substrates and those fed a
complex mixture of soluble and suspended organic material.
The response of a culture to a 6-fold step increase in the
influent substrate concentration is illustrated in Figure 21.
The significant differences between this transient and those
observed earlier are:
(a) The magnitude of the soluble COD peak observed
in the reactor effluent was significantly less
than those observed for comparable transients in
the glucose and composite waste experiments.
This reflects the earlier comment regarding the
mixture of soluble and insoluble components in
the total COD of the synthetic sewage.
(b) The buildup of the soluble COD in the reactor was
largely controlled by the hydraulics of the system
and therefore closely resembles the shape of the
increases observed during transients in the glu-
cose and the composite waste experiments. How-
ever, the decrease in the soluble COD in the re-
actor was much slower for the synthetic sewage
than those observed for the other wastes. This
slow decrease in the soluble COD was probably
caused by hydrolysis of the suspended organic
material present in the influent.
(c) The increase in suspended solids and in oxygen
utilization was much slower for step transients
using the synthetic sewage than were observed
those for comparable transients in the glucose
and the composite waste. This is probably also
caused by the hydrolysis reactions mentioned
above.
65
-------
18O
o Total COD
• Soluble COD
• Oxygen Uptake
A Suspended Solids
- 1000
- 700
- 400
."D
"5
I
0)
a.
-------
Summaries of the results observed for oxygen utilization and
soluble COD in the reactor effluent are given for all of
the transients studied in Figures 22 through 25. The data
presented in Figure 22 reflects the difficulties with pump
clogging mentioned earlier. The missing data in this figure
was caused by this factor. The apparent decrease in the
oxygen uptake rate following a period of missing data may
be in error.
The 3-hour mean residence time system was capable of re-
sponding to a 2-fold step increase in the influent substrate
concentration without a change in the concentration of the
soluble COD in the reactor effluent. The evidence is in-
conclusive for the 6-hour mean residence time system because
the response of the culture appeared to be erratic. However,
at the present time, doubling the concentration in the in-
fluent appears to be the maximum change the culture can with-
stand without producing an increase in soluble COD in the re-
actor .
Distinct oxygen uptake peaks were not observed when the
change in the influent substrate concentration was large
enough to produce peaks of soluble COD in the reactor ef-
fluent. There is some evidence of smaller magnitude relat-
ively long duration peaks in oxygen utilization during the
3-hour mean residence time experiments. However, when these
peaks do exist their magnitude appears to be within 10 per-
cent of the steady state oxygen utilization rate.
One step decrease in the influent substrate was conducted
with the 6-hour mean residence time system. Culture be-
havior was very similar to that observed for the glucose
and the composite wastes. No change occured in the soluble
COD concentration. The decrease in total COD and in the
mixed liquor suspended solids was approximately equal to the
hydraulic wash out time. The decrease in the oxygen utiliza-
tion rate was quite rapid. A new steady state was establish-
ed approximately 6 hours after the start of the transient.
This is somewhat longer then the time required for a com-
parable transient with the composite waste. The difference
is probably due to the hydrolysis of particulate matter in
the synthetic sewage.
The predominate organisms present in the 3-hour mean resid-
ence time system were dispersed bacteria. Some fungi and
a few small free swimming protozoa were present. In the 6-
hour mean residence time experiments the bacterial mass
shifted from a predominance of bacterial floe with a few
actinomycetes, and stalked and free swimming cilitates at the
start of the experiments to a predominance of fungi and very
67
-------
CT<
00
180
5 140
CVJ
d
I5
1100
03
6 60
20
249 to 433 mg/L
233 to 690 mg/L
232 to 864 mg/L
189 to 12OO mg/L
-2 O 2 6 1O 14 18
Time, Hours
Figure 22. Summary of Changes in Oxygen Uptake Rate in
Response to Step Increases in the Influent,
Synthetic Sewage, 3-Hour Mean Residence Time
-------
VO
249 to 433 mg/L
233 to 690 mg/L
• 233 to 864 mg/L
189 to 1200 mg/L
uj
Figure 23.
10
Time, Hours
Summary of changes in Soluble COD Concentration in the
Reactor in Response to Step Increases in the Influent,
Synthetic Sewage, 3 Hour Mean Residence Time
-------
80
I
I
x 60
o
214 to 316 mg/L
—— 176 to 615 mg/L
169 to 1420 mg/L
••••• •
1
1
1
1
1
1
1
-2
14
18
Figure 24
6 10
Time, Hours
Summary of Changes in Oxygen Uptake Rate in
Response to Step Increases in the Influent,
Synthetic Sewage, 6 Hour Mean Residence Time
-------
200
150
O
O
O
2 100
o
V)
t:
-------
small free swimming ciliates at the end. The presence of
microorganisms in the synthetic sewage concentrate may have
contributed to these population shifts.
A biochemical oxygen demand (BOD) to chemical oxygen demand
(COD) ratio was not measured for the synthetic sewage so a
comparison between the observed and predicted suspended
solids concentration and oxygen utilization rate was not
possible. Observed steady state values are given in Table
22.
Table 22. Observed Steady State Suspended Solids
and Oxygen Uptake Rates for Synthetic
Sewage
3 -Hour Mean Residence Time
Cnfluent
COD
mg/L
189
233
249
265
864
1200
Suspended
Solids
mg/L
102
120
117
153
438
"
Oxygen
Uptake
mg/L/hr
20
24
23
30
93
130
6-Hour Mean Residence Time
Influent
COD
mg/L
169
176
214
615
1410
Suspended
Solids
mg/L
162
133
122
344
573
Oxygen
Uptake
mg/L/hr
15
9
14
53
87
The 3-hour mean residence time observations correspond
closely to the values reported for the glucose and the
composite wastes. The value of 169 mg/L influent COD re-
ported for the 6-hour mean residence time appears to be in
error. Both the suspended solids and the oxygen uptake
observations indicate the COD concentration was approximate-
ly 200 mg/L.
Di-scussion
Transient response for the glucose and the composite wastes
were very similar. Large increases in the influent substrate
concentration produced conditions analogous to the classical
response observed in batch cultures immediately after the
72
-------
addition of a large amount of food.
The first reaction in the culture was a short period of ad-
justment or acclimation. This was followed by period of
exponential growth which continued until the excess exogenous
food supply was exhausted. The culture then rapidly shifted
into declining growth and a new steady state was established.
The sequence of this reaction is illustrated in Figure 26
which summarizes the suspended solids observations for the
upward transients conducted at the 3-hour mean residence
time for the composite waste. The suspended solids obser-
vations have been plotted on a logrithmic scale to illustrate
the change in growth rate.
The end of exponential growth was determined for each of
the upward transients during which it occured by the graph-
ical procedures illustrated in Figure 26. This information
was combined with concurrent observations of the soluble COD
in the reactor to produce graphs similar to the one illust-
rated in Figure 27. The estimates obtained by this process
for the critical food to mass (F/M) ratio for the glucose and
the composite wastes at 25°C are summarized in Table 23.
Table 23. Food to Mass Ratios Observed at the
Transition from Exponential to Declining
Growth for the Glucose and the Composite
Wastes
3-Hour Mean Residence Time
Waste
Glucose
Glucose
Composite
Composite
Composite
F/M*
0.58
0.48
0.43
0.40
0.27
*F /„ soluble COD mg/L
' suspended solids mg/L
6-Hour Mean Residence Time
Waste
Glucose
Composite
F/M*
0.50
0.55
73
-------
A 245 to 974 mg/L
o 214 to 411 mg/L
• 241 to 1460 mg/L
• 253 to 750 mg/L
100
2 6
Time After Transition (Hours)
Figure 26. Summary of the Suspended Solids
Observations for the Upward Transients
Conducted at the 3-Hour Mean Residence
Time for the Composite Waste
74
-------
4.O
o 245 to 974 mg/L
• 253 to 750 mg/L
• 241 to 1460 mg/L
A 214 to 411 mg/ L
246
Time After Transition (Hours)
Figure 27. Summary of Changes in Food to Mass
Ratios for the Upward Transients
Conducted at the 3-Hour Mean Resi-
dence Time for the Composite Waste
75
-------
The COD measurements used to determine the (F/M) ratios in
Table 23 include some nonbiodegradable end products in
addition to soluble biodegradable substrate. To be com-
pletely valid, (F/M) ratios should be based on ultimate BOD
rather than COD. However, COD is the most practical method
of measuring the concentration of soluble organic material
in continuous flow systems.
The critical (F/M) ratios given in Table 23 are significant-
ly lower than the corresponding values reported for batch
systems (23) . There are two reasons for this: one is the
difference in the rate of culture response for simple
soluble substrates and for complex substrates containing both
soluble and suspended material. The second reason involves
the constant addition of substrate which occurs in a con-
tinuous flow system. A continuous culture has available
to it over any given time interval the substrate already in
the reactor plus the substrate entering the reactor during
that time interval.
The concept of the food to mass (F/M) ratio should therefore
be revised to include the rate of organic loading, the type
of substrate, and the temperature. This is an area which
requires further research.
The oxygen uptake rate during transients which involved
exponential growth included a characteristic transient peak
which in this research ranged from 119 to 150 percent of the
new steady state. The period of maximum oxygen utilization
occured after the culture had shifted from exponential to
declining growth with the peak usually coinciding with the
point at which the soluble COD in the reactor returned to a
new equilibrium. The rate of decrease in oxygen utilization
from the peak to the new steady state was extremely rapid
and appears to be quite analogous to the response relation-
ship observed throughout the aeration only experiments
following a step decrease in the influent substrate.
76
-------
SECTION VII
AERATION WITH SLUDGE RETURN ACTIVATED SLUDGE SYSTEMS
Experimental Conditions
The aeration with sludge return experiments were conducted
in a completely mixed reactor having a liquid volume of
10.00 liters. An upflow draft tube was used for aeration
and mixing. The liquid was pumped through the tube by two
paddles rotating at 400 revolutions per minute. The respiro-
meter contained 2.55 liters of gas above the surface of the
liquid. This gas was recirculated through a scrubber con-
taining a solution of 10.7 N potassium hydroxide to remove
the carbon dioxide produced by the culture. The gas pumping
rate was 60±10 liters per hour. The aeration basin was
followed by a sedimentation basin with a 2-hour hydraulic
detention time. Sludge was continuously recirculated from
the sedimentation basin back to the aeration basin. All
experiments were conducted at 25±0.25°C.
The experiments conducted during this phase of the project
were limited to an investigation of the transient response
of cultures metabolizing the composite waste described in
Secton V. The reason for limiting the investigation was
the difficulty experienced in maintaining an activated sludge
culture which had good settling properties. This problem
initially manifested itself when batch units, which had been
acclimated to the waste and operated to establish a steady
state mixed liquor suspended solids concentration, were
transfered to the continuous flow system. During the first
several days of continuous flow operation, the culture would
function with good solids separation in the sedimentation
basin. However, invariably there would be an increase in
filamentous growth which eventually resulted in partial wash-
out of the culture because of sludge bulking. This problem
was alleviated by increasing the concentration of mixed
liquor suspended solids (MLSS) in the batch units so the con-
centration of the chemical oxygen demand (COD) in the in-
fluent of the continuous flow system was initially less than
1.5 pounds of COD per day per pound of MLSS. However, sludge
bulking still occured occasionally following step increases
in the 3-hour mean residence time transient experiments. All
of these experiments were therefore conducted with a new cul-
ture which was developed form domestic sewage in a batch
unit. These units contained 8 liters and were operated on a
cycle of 23 hours of aeration followed by 1 hour of settling.
Six liters of the supernatant were then withdrawn and re-
placed by a solution of the composite waste containing 500
mg/L as COD. This procedure was followed for 7 days before
transfering the contents of the unit to the continuous flow
77
-------
reactor. The continuous flow system was then operated with-
out sludge wasting for approximately 4 days. Sludge then
was wasted at 8-hour intervals to maintain a constant MLSS
concentration for 24 to 48 hours before the start of an ex-
periment .
It was not necessary to develop a new culture each time the
6-hour mean residence time experiments were conducted.
Three-Hour Mean Residence Time Experiments
Six step transient experiments were conducted at the 3-hour
mean residence time. The combinations studied are summarized
in Table 24.
Table 24. Summary of 3-Hour Mean Residence Time
Transients Conducted on the Aeration
With Sludge Return System.
Influent Concentration
COD mg/L
130 - 268
135 - 508
135 - 972
286 - 560
286 - 600
280 - 1104
Suspended Solids Concentra-
tion Before Starting Tran-
sient
mg/L
1760
1776
3320
1572
2152
3716
An example of the parameter response observed during a tran-
sition is given in Figure 28. The suspended solids and
soluble chemical oxygen demand (COD) values in Figure 28
were observed in the effluent of the aeration basin. The
oxygen uptake observations also include only the respiration
occuring in the aeration basin.
Figure 28 illustrates a severe case of culture washout begin-
ning approximately 6 hours after the start of the transient.
The loss in suspended solids did not effect removal of sol-
uble COD by the culture but did cause a decrease in the
oxygen utilization rate. A slight deterioration in settling
also occured approximately 6 hours after starting the 130 to
268 mg/L COD transient. In this instance the decrease in
suspended solids was not large enough to significantly
78
-------
90
3
o
N
f
0>
(0
6O
30
to
s?
a
0 -
I
I
"1 50
Q
O
O
B
Ul
30
o
(O
£ 10
0)
Soluble COD
Oxygen Uptake
Suspended Solids
-1 0
Time, Hours
210O
1800
T3
"5
1500 a.
05
t
12OO
11
Figure 28
Parameter Response for a Transition
from 135 to 508 mg/L Influent COD,
Composite Waste, 3-Hour Mean Residence
Time, Aeration with Sludge Return
79
-------
affect the rates of oxygen utilization. Deterioration in
settling characteristics was not observed during any of the
other transients included in Table 24, but an increase in
the concentration of filamentous growth was observed in all
except the 135 to 972 and the 280 to 1104 mg/L transients.
Summaries of the oxygen uptaJce and the soluble COD concen-
trations observed during the 3-hour mean residence time
experiments are given in Figure 29 and Figure 30. The abrupt
decrease in the soluble COD observed immediately after the
start of a transient was not anticipated because Engelbrecht
and McKinney (36) have demonstrated glucose, glutamic acid,
and acetate are not readily removed by biosorption and virtu-
ally all of the mathematical models of the activated sludge
process predict an increase in the soluble COD following a
step increase in the influent. A possible explanation may
be the polysaccharide slime layer secreted by bacteria during
the declining growth phase. A portion of this slime layer
may be removed from the bacterial cells by shearing action
caused by hydraulic turbulence and subsequently measured
as a component of the soluble COD from the aeration basin.
When the culture was subjected to an increase in substrate
there was an immediate increase in the synthesis of young
cells which did not produce the polysaccharide slime layer.
The concentration of soluble COD therefore decreased until
a balance between synthesis and endogenous respiration was
reestablished and the polysaccharide layer was again being
sheared from the old cells. This decrease in soluble COD
was not observed in the aeration only system because the con-
centration of biological solids, and therefore, the possible
change in polysaccharide concentration, was much smaller.
More research in this area is warranted.
The oxygen limitation in the 280 to 1104 mg/L COD transient
was caused by the rate of oxygen demand of the culture ex-
ceeding the oxygen supply capacity of the respirometer. The
dissolved oxygen concentration in the aeration basin was less
than 1 mg/L two hours after the start of the transient and
remained at this concentration for 10 hours. During this
period the concentration of soluble COD in the effluent did
not increase. However, the culture would probably have
eventually failed due to a shift in predomination toward
filamentous organisms.
The oxygen uptake and suspended solids observations for the
3-hour mean residence time aeration with sludge return ex-
periments are summarized in Table 25. No suspended solids
were wasted from the system after the start of a transient.
the values given in Table 25 for this- parameter are there-
fore indicative of both growth in the culture and the parti-
tion of solids between the aeration and the sedimentation
basin.
80
-------
ISO -
12O -
3
o
I-
x
_l
s
03
-------
140
3
O
I
X
110
5?
•x
O
80
Oxygen limitation
50 -
5O
286 to 560 mg/L
286 to 600 mg/L
280 to 1104 mg/L
a
O
O
I 30
c
0)
_3
«#-
UJ
1 0 1
Figure 30
11
Time. Hours
Partial Summary of Changes in Oxygen
Uptake Rate and Effluent Soluble COD
in Response to Step Increases in the
Influent, Composite Waste, 3-Hour
Mean Residence Time/ Aeration with
Sludge Return
82
-------
Table 25. Summary of Oxygen Uptake Rate and Suspended Solids Concentrations
for the 3-Hour Mean Residence Time Aeration With Sludge Return
Experiments
Influent
COD
mg/L
130 to 268
135 to 508
135 to 972
286 to 560
286 to 600
280 to 1104
Parameter*
d02/dt
SS
d02/dt
SS
d02/dt
SS
d02/dt
SS
d02/dt
SS
d02/dt
SS
Elapsed Time from Start of Transient, Hours
0
47
1760
38
1776
42
3320
67
1572
63
2152
87
3716
1
62
1709**
74
1792**
94
3412**
93
1624**
79
2204**
154
3796**
2
61
1658
78
1808
130
3504
95
1676
91
2256
156
3876
3
67
1720
86
I860**
140
3650**
107
1750**
94
2280**
155
4250**
6
67
1806
93
2028
148
3964
121
1916
114
2430**
4700**
9
63
1850**
92
1810
153
4324
121
2100
113
2610**
4628
*d02/dt = mg/L/hr SS = mg/L
**Values interpolated from graphical analysis of observations
00
CO
-------
It was not possible to predict the steady state suspended
solids concentrations and cultures with the equations de-
veloped by McKinney (24) because the procedure used in de-
veloping the stock culture did not establish a steady state
sludge age (t ) .
O
Six-Hour Mean Residence Time Experiments
Four step transients experiments were conducted at the 6-hour
mean residence time. The combinations studied are summarized
in Table 26.
Table 26. Summary of 6-Hour Mean Residence Time
Transients Conducted on the Aeration
With Sludge Return System
Influent Concentration
COD
mg/L
Suspended Solids Concentra-
tion Before Starting Tran-
sient
mg/L
250 - 491
269 - 773
269 -1035
285 -1060
1428
1228
1502
1341
An example of the parameter response observed during a
transition is given in Figure 31. The shape of the oxygen
uptake curve is very similar to that illustrated in Figure
28 for the 3-hour mean residence time system. The concentra-
tion of suspended solids in the aeration basin continued to
increase throughout the duration of the transient. This
was repeated in three of the four 6-hour mean residence
time transients. The sludge remained free from filamentous
growth throughout the duration of all of the transients and
no change was observed in settling properties.
A partial summary of the oxygen uptake and the soluble COD
concentrations observed during the 6-hour mean residence
time experiment is given in Figure 32. The data for the 285
to 1060 mg/L COD transient has been omitted from the figure
because it is essentially identical to that observed during
the 269 to 1035 mg/L COD transient. The abrupt decrease in
soluble COD observed in the 3-hour mean residence time ex-
84
-------
90 -
O -
d
o
o
«
.o
_3
O
CO
c 10
0)
30
• Soluble COD
• Oxygen Uptake
A Suspended Solids
2200
1900
16OO
D3
E
U)
"5
CO
T3
0)
TI
en
CO
13OO
-1 0 1
5 7
Time, Hours
11
Figure 31.
Parameter Response for a Transition
from 269 to 1035 mg/L Influent COD,
Composite Waste, 6-Hour Mean Residence
Time, Aeration with Sludge Return
System
85
-------
90
3
O
V
_J
N
O5
0)
Jt
a
•«->
QL
ro
x
O
6O
3O
0 -
250 to 491 mg/L
1 50
o
O
0 30
s.
o
~ 10
a
3
zoyto //3 mg/L i
269 to 1035 mg/L !
:.....
__A j2^^^=----=;=^^ziz^ll
1 1 I 1 1 1 i 1 ! 1 1 |
•*- 1
tu -1
11
Time. Hours
Figure 32.
Partial Summary of Changes in Oxygen
Uptake Rate and Effluent Soluble COD
in Response to Step Increases in the
Influent, Composite Waste, 6-Hour Mean
Residence Time, Aeration with Sludge
Return
86
-------
periments was observed in only the 2-fold step increase at
the 6-hour mean residence time. Both of the other transients
showed slight increases. If the hypothesis advanced earlier
concerning the polysaccharide slime layer is correct, there
was apparently enough unmetabolized influent passing through
the system during the larger step transients to mask the
interaction between growth state and hydraulic turbulence.
The increase in soluble COD was not large enough in either
transient to be significant in a practical sense.
The oxygen uptake and suspended solids observations for the
6-hour mean residence time aeration with sludge return ex-
periments are summarized in Table 27. No suspended solids
were wasted from the system after the start of a transient.
It was not possible to predict the steady state suspended
solids concentrations and oxygen uptake rates of the culture
with the equations developed by McKinney (24) because the
adjustment period between experiments was not long enough
to establish a steady state sludge age (t ).
s
Discussion
Difficulties with filamentous growth in activated sludge
systems is not new. Carter (44) has presented an extensive
literature review on sludge bulking especially as it applies
to substrates containing glucose. The most common causes of
filamentous growth have been low concentrations of dissolved
oxygen, nitrogen and iron deficiencies, and high loading
rates in the influent waste.
In this research, dissolved oxygen levels in excess of a 2
mg/L and an excess of nitrogen, iron, and other nutrients
were maintained. The key parameter in the development of
filamentous growth therefore appeared to be the loading rate.
The loading rates used are summarized in Table 28.
In the 3-hour mean residence time experiments, the units
having a steady state loading rate less than 0.7 pounds of
COD per day per pound of MLSS had a well balanced biological
population with no filamentous growth. The two experiments
which had a steady state loading rate greater than 1 pound
of COD per pound of MLSS had a limited amount of filamentous
growth. All of the experiments, except the 135 to 972 and
the 280 to 1104 mg/L influent COD, developed filamentous
growth after the start of the transient. The two transients
which did not develop filamentous growth had a MLSS concen-
tration greater than 3000 mg/L.
87
-------
Table 27.
Summary of Oxygen Uptake Rates and Suspended Solids Concentrations
for the 6-Hour Mean Residence Time Aeration With Sludge Return
Experiments
Influent
COD
mg/L
250 to 491
269 to 773
269 to 1035
285 to 106C
Parameter*
d02/dt
SS
d02/dt
SS
d02/dt
SS
d02/dt
SS
Elapsed Time from Start of Transient, Hours
0
42
1428
41
1229
44
1502
40
1341
2
56
1436
67
1290**
79
1530**
81
1500**
4
59
1470**
72
1450
88
1830
89
1525**
6
58
1460**
71
1482
94
1776
88
1610**
9
59
1424
73
1630**
95
1930**
94
1790**
12
56
1250**
75
1800**
97
2000**
96
1842
*d02/dt = mg/L/hr SS = mg/L
**Values interpolated from graphical analysis of observations
00
00
-------
Table 28.
Organic Loading Rates Imposed on the
Continuous Flow Aeration with Sludge
Return Activated Sludge Systems
Influent
Concentration
COD
mg/L
Steady State
Loading Rate
Ib COD/day/lb MLSS
Initial Transient
Loading Rate
Ib COD/day/lb MLSS
3-Hour Mean Residence Time
130 to 268
135 to 508
135 to 972
286 to 560
286 to 600
280 to 1104
0.63
0.60
0.33
1.46
1.06
0.61
1.30
2.26
2.36
2.85
2.23
2.40
6-Hour Mean Residence Time
250 to 491
269 to 773
269 to 1035
285 to 1060
0.70
0.88
0.72
0.85
1.38
2.53
2.76
3.16
No filamentous growth was observed during the 6-hour mean
residence time experiments either before or after the start
of a transient.
These findings partially confirm the report of Adams and
Eckenfelder (45) regarding the growth of filamentous organ-
isms, during transient conditions. However, this research
strongly indicates loading rate by itself does not define the
conditions which produce filamentous growth. The concentra-
tion of suspended solids and the hydraulic mean residence
time in the aeration basin are also significant factors.
89
-------
Additional studies should be undertaken to more fully de-
fine this interrelationship.
90
-------
SECTION VIII
ENGINEERING SIGNIFICANCE
Oxygen Requirements During Transient Conditions
This research has demonstrated both aeration only and aeration
with sludge return activated sludge systems are capable of
responding to step increases in the influent substrate with-
out an increase in the concentration of COD in the effluent.
A satisfactory method of estimating the oxygen uptake rate
at any time during this type of transient can be developed
by considering the fundamental microbiology of the system.
At steady-state the total rate of oxygen demand by a culture
is the sum of the oxygen used in synthesis reactions, the
oxygen used for endogenous respiration, and the oxygen used
for nitrification. The oxygen demand exerted by the syn-
thesis reactions is directly dependent on the rate biode-
gradable organic material is added to the aeration basin.
The oxygen used for endogenous respiration is dependent upon
the cell mass. The oxygen used for nitrification is depen-
dent upon the concentration of oxidizable nitrogen and the
presence of nitrifying bacteria.
During transient conditions the oxygen demand exerted by
synthesis reactions increases rapidly. The increase in
oxygen demand by endogenous respiration and nitrification is
related to the increase in active cell mass in the system
and is therefore relatively slow. This interrelationship is
illustrated in Figure 33. In this figure the oxygen demand
rate by endogenous respiration and nitrogenous oxidation is
designated as the basal rate. The oxygen uptake rate at any
time during a transient (t ) is equal to the sum of:
A. the demand rate due to synthesis of the in-
fluent biodegradable organic load at time (t ) ,
B. The basal rate during steady-state operation,
and
C. the increase in basal rate due to the buildup
of cell mass from the start of the transient
until time (t.).
Only after the cell mass has attained a new equilibrium will
a true steady state oxygen uptake rate be reestablished. In
an aeration only system this will take place within 3 mean
residence times. However, the basal rate is only a small
fraction of the total oxygen used in an aeration only system
so the new steady state oxygen uptake is essentially estab-
lished in one mean residence time.
91
-------
The magnitude of the steady- state basal oxygen uptake rate
and the increase in this rate during a transient are much
more significant in an aeration with sludge return activated
sludge system because the biological solids are continuously
being recycled to the aeration basin instead of being dis-
charged in the effluent. This results in a more rapid in-
crease in the MLSS in the aeration basin during a transient.
An estimate of the rate of oxygen uptake at any time
during a transient can be obtained by two steps. The first
is to examine the steady-state conditions preceding the tran-
sient by the following technique:
(a) Compute the oxygen uptake under steady- state
conditions using the equations developed by
McKinney (24) . This value is designated as
dO/dt(s). If accurate experimental measure-
ments of the steady- state oxygen demand are
available these may be used in lieu of the
computed value.
(b) Compute the steady- state oxygen demand rate
due to synthesis. This value, designated Ogs/
is obtained by:
(18) Oss = 0.33
where Oss = steady- state oxygen uptake rate
due to synthesis, mg/L/Hr.
t = mean residence time in the aeration
basin, hours
BODU = ultimate biochemical oxygen de-
mand of the influent, mg/L
The constant 0.33 in equation 18 is based on
an energy-synthesis relationship of 1/3 - 2/3.
This value has been obtained on domestic wastes
by McKinney (23) . Burkhead (33) has also ob-
tained this value for the composite waste used
in this research.
(c) Compute the steady- state basal rate. This value,
designated O^g, is obtained by:
- 0
SS
92
-------
Total Oxygen Uptake Rate
0)
+*
to
QC
I
Synthesis Rate
0
Figure 33,
Time After Transition »—
Relationship Between Synthesis and Basal Oxygen
Uptake Rate During a Step Transient
-------
where O^s = steady-state basal oxygen up-
take rate
,. = total oxygen uptake rate at
Is' steady-state
The second step is to determine the change in synthesis and
endogenous respiration that occurs during the transient. If
we assume the concentration of unmetabolized substrate leav-
ing the reactor is negligible, the magnitude of the synthesis
reaction is equal to the new steady-state after one hydraulic
mean residence time has elapsed. The increase in synthesis
is approximately 87 percent at the end of the first one third
and 98 percent at the end of the second one third of the
first hydraulic mean residence time. The oxygen uptake due
to synthesis during a transient is:
(20) Ost = 0.33 (^p21) ( 1 - e~2tt)
for the 3 hour mean residence
time and by:
(21) Ost = 0.33
for the 6 hour mean residence
time.
where Ost = oxygen uptake rate due to synthesis
during a step transient, mg/L/hr.
t.j- = elapsed time since start of the
transient, hours.
The increase in endogenous respiration is obtained by assum-
ing all the protoplasm synthesized during the transient re-
mains in the aeration basin. This is not true because some
of the material leaves in the effluent. However, during the
first hydraulic mean residence time after the start of the
transient the magnitude of the error introduced by this
assumption is very small. This is especially true in the
aeration with sludge return system. The increase in oxygen
uptake by endogenous respiration is given by:
BODU
(22) Obt = 0.47Kett( . )
94
-------
where Ke = endogenous respiration constant as
defined by McKinney (24)
The constant 0.47 in equation 22 is based on the energy-
synthesis relationship cited in equation 18 and a factor to
convert activated sludge mass units to oxygen equivalents.
The total oxygen demand rate at any time during a step tran-
sient is therefore:
(23)
dO
at
= °
bS
8t
0
bt
where
= total oxygen uptake rate at any
(t) time during a step transient,
mg/L/hr .
To illustrate this procedure, example calculations using the
data from the 135 to 508 mg/L influent COD transient illus-
trated in Figure 28 are given below. The steady-state oxygen
uptake rate for this 3-hour mean residence time system was
38 mg/L/hr. If we assume the influent COD is equal to the
ultimate BOD of the composite waste, the predicted oxygen
uptake 2 hours after the start of the transient is:
,135
) = 15 mg/L/hr
bg = 38 - 15 = 23 mg/L/hr
= ~ -~4
S t
°bt = (0'47)
(1-e ) = 55 mg/L/hr
g-) = 4 mg/L/hr
dO
at
(t)
= 23 + 55 + 4 = 82 mg/L/hr
The observed oxygen uptake rate was 78 mg/L/hr.
The observed and predicted transient oxygen uptake rates for
both the aeration only and the aeration with sludge return
transients conducted with the composite waste are given in
Table 29 and Table 30. Good agreement between the predict-
ed and the observed values was obtained for both the 3 and
the 6-hour mean residence time systems during the first 6
hours of a transient. After this interval the predicted
values are consistently high. This illustrates an accumula-
tive departure from the assumption that all of the biologic-
al solids synthesized during the transient remain in the
95
-------
VD
Table 29. Summary of Observed and Predicted Oxygen Uptake Rates
for the 6-Hour Mean Residence Time System, Composite
Waste
Influent
COD
mg/L
250 to 491
269 to 773
269 to 1035
285 to 1060
250 to 504*
235 to 736*
Oxygen Uptake
Rate
mg/L/Hr
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Elapsed Time from Start of Transient, Hours
2
56
53
67
66
79
84
81
80
33
30
39
44
4
59
58
72
75
88
95
89
90
37
35
50
52
6
58
60
71
78
94
100
88
96
35
39
51
56
9
59
63
73
83
95
107
94
103
37
42
47
61
12
56
66
75
88
97
114
96
110
36
52
54
66
*Aeration Only all other transients are Aeration with Sludge Return
-------
Table 30. Summary of Observed and Predicted Oxygen Uptake Rates
for the 3-Hour Mean Residence Time System, Composite
Waste
Influent
COD
mg/L
130 to 268
135 to 508
135 to 972
286 to 560
286 to 600
478 to 717*
214 to 411*
Oxygen Uptake
Rate
mg/L/Hr
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Observed
Predicted
Elapsed Time from Start of Transient, Hours
1
62
60
74
74
94
124
93-
92
79
92
84
81
41
45
2
61
64
78
82
130
141
95
101
91
102
90
92
46
52
3
67
66
86
86
140
147
107
105
94
106
89
97
50
54
6
67
69
93
93
148
160
121
112
114
114
91
106
55
59
9
63
73
92
100
153
170
121
119
113
122
90
115
54
64
*Aeration Only all other transients are Aeration with Sludge Return
-------
aeration basin.
In the aeration only system the predicted oxygen uptake rate
after one mean residence time can be safely used for deter-
mining the maximum demand on the oxygen transfer system. The
maximum rate of oxygen uptake observed in solids return units
will, in part, be dependent on the efficiency of the solids
separation and recycle system. On the basis of this re-
search, the oxygen uptake rate conputed for periods up to
6 hours after the start of a transient can be safely used for
design purposes.
Selection of an oxygen demand rate for design of a treat-
ment plant should be based on a thorough knowledge of the
magnitude and frequency of the transient loading conditions
which are expected to occur. If transient conditions are in-
frequent and less than one hour in duration, the average
loading rate on the system can be used to determine the
oxygen demand rate for design purposes. In aeration with
sludge return systems this rule holds even if the transient
load is very large because these units can operate under
oxygen limiting conditions for short periods without deter-
ioration of the effluent. In aeration only systems this rule
holds from the standpoint of the oxygen supply system but a
transient deterioration in effluent quality may occur.
If the treatment system is to be subjected to frequent,
high magnitude, long duration transients, oxygen transfer
capacity in excess of the average demand rate must be pro-
vided. Under these conditions, substituting the maximum
loading rate into steady state equations, such as those de-
veloped by McKinney (24), will result in predictions which
are significantly higher than what is actually observed in
sludge recycle systems because the sludge mass is not in
equilibrium. In aeration only systems treating soluble
wastes, the opposite condition occurs because the culture
may shift into exponential growth and produce an oxygen up-
take peak significantly greater than the steady-state value.
The results of this research provide guidlines which can be
used by the design engineer to size the oxygen transfer
facilities in both instances.
Aeration Only Activated Sludge Systems
The 3-hour mean residence time aeration only systems were
capable of withstanding a 2-fold increase in the influent
without an increase in the soluble COD in the effluent. The
capability to resist a shock load without deterioration of
the effluent was increased to 3-fold in the 6-hour mean
98
-------
residence time systems. This research was conducted at 25°C
and the ability to successfully respond to a shock load is
directly related to the rate of metabolism in the culture.
Therefore, the maximum permissible transient at 15°C can
be expected to be about one half the values given above.
In most applications, temperatures of 15°C or lower can be
expected during part of each year. If this occurs, short
term aeration only systems, similar to those suggested by
Tenney et al (5) (6), will be restricted in their usefulness.
Under tKese conditions a second treatment process will be
required to reduce the concentration of the soluble COD in
the effluent to acceptable levels.
Aeration With Sludge Return Activated Sludge Systems
This research has again demonstrated that completely mixed
activated sludge (CMAS) systems with solids recycle can
handle large step increases in soluble organic loading with-
out an increase in soluble COD in the effluent. Step in-
creases of up to 7.2 times did not produce a change in the
effluent soluble COD. This was not the maximum limit, how-
ever, because the system was not loaded to failure.
One of the keys to successful operation of any CMAS system
is the capability of separating the microbial solids in the
secondary sedimentation basin. Loading rate was found to
be a critical factor in the production of filamentous growth
in systems metabolizing substrates containing glucose.
However, sludge bulking was prevented by maintaining the
MLSS concentration in the aeration basin between 3000 to
4000 mg/L. Additional research in this area is warranted.
99
-------
SECTION IX
ACKNOWLEDGEMENTS
This research was performed in the C.L. Burt Environmental
Health Laboratory of the University of Kansas. Dr. Walter
J. O'Brien and Dr. Carl E. Burkhead were the project direct-
ors.
Portions of the investigation were conducted by Dr. Robert
W. Agnew and Dr. Michael J. Chun in fulfillment of their
dissertation research.
Dr. Ross E. McKinney was a generous source of invaluable
advise and assistance throughout the course of the project.
Laboratory support was provided by Mr. Martin Trnovsky.
The project was funded in part by the Environmental Pro-
tection Agency. Supplemental financial assistance to pur-
chase equipment and supplies was provided by the University
of Kansas Center for Research, Inc.
Sincere thanks are extended to Mr. Richard C. Brenner, the
Grant Project Officer for his patience and assistance. A
vote of thanks is also due Mrs. Kathleen Boyd for typing
the manuscript.
101
-------
SECTION X
REFERENCES
1. Eckhoff, D.W. and Jenkins, D., "Transient Loading Effects
in the Activated Sludge Process", Third International
Conference on Water Pollution Research, Munich, Germany
(1966).
2. Loehr, R.C., "Variation of Wastewater Quality Parameters"
Public Works, 99^ 81 (1968) .
3. Tilsworth, T., "Field Evaluation of Modified High Rate
Activated Sludge", Master of Science Thesis, Univ. of
Nebraska, Lincoln, Nebraska (1967).
4. Gaudy, A.F., Jr., and Engelbrecht, R.S., "Quantitative
and Qualitative Shock Loadings of Activated Sludge
Systems", Jour. Water Poll. Control Fed., 33, 800 (1961).
5. Tenney, M.W., Johnson, R.H., Jr., and Symons, J.M.,
"Minimal Solids Aeration Activated Sludge", Jour. San.
Eng. Div., ASCE, 90, SAl, 23 (1964).
6. Tenney, M.W., and Stumm, W., "Chemical Flocculation of
Microorganisms in Biological Waste Treatment", Jour.
Water Poll. Control Fed., 37, 1370 (1965).
7. McKinney, R.E., Benjes, H.H., Jr., and Wright, J.R.,
"Evaluation of a Complete Mixing Activated Sludge Plant"
Jour. Water Poll. Control Fed., 42, 737 (1970).
8. Agnew, R.W., "The Oxygen Uptake of a Biological Culture
Subjected to Transient Organic Loadings", PhD Disserta-
tion, Univ. of Kansas, Lawrence, Kansas (1968).
9. Chun, M.J., "Oxygen Response of a High Solids Completely
Mixed Activated Sludge System to Transient Organic
Loadings", PhD Dissertation, Univ. of Kansas, Lawrence,
Kansas (1970) .
10. Monod, J., "La Technique de Culture Continue; Theorie
et Applications", Annals Institute Pasture, 79, 390
11. Novick, A. and Szilard, L., "Experiments with the Chemo-
stat on Spontaneous Mutations of Bacteria", Proc. Nat'l
Acad. Sc., 3£, 708 (1950).
12. Herbert, D., Elsworth, R., and Telling, R.C., "The Con-
tinuous Culture of Bacteria; a Theoretical and Experi-
mental Study", Jour. Gen. Microbiol., 14, 601 (1956).
103
-------
13. Rickard, M.D., and Gaudy, A.F., Jr., "Effect of Mixing
Energy on Sludge Yield and Cell Composition", Jour.
Water Poll. Control Fed., 40, R219 (1968).
14. Hetling, L.J., and Washington, D.R., "Kinetics of the
Steady-State Bacterial Culture III. Growth Rate", Proc.
20th Industrial Waste Conf., Purdue Univ., Lafayette,
Indiana (1965).
15. Gaudy, A.F., Jr., and Gaudy, E.T., "Microbiology of
Waste Waters", Annual Review_ofMicrobiology^ 20, 319
(1966).
16. Teissier, G., "Les Lois Quantitatives de la Croissance",
Ann Physiol. Physicochim., Biol., 12f 527 (1936).
17. Schulze, K.L., "The Activated Sludge Process as a Con-
tinuous Flow Culture, II. Application", Water and
Sewage Works, 112, 11 (1965).
18. Contois, D.E., "Kinetics of Bacterial Growth; Relation-
ship Between Population Density and Specific Growth
Rate of Continuous Cultures", Jour. Gen. Microbiol., 21,
40 (1949).
19. Pert, S.J., "The Oxygen Requirements of Growing Cultures
of an Aerobacter Species Determined by Means of the
Continuous Culture Technique", Jour. Gen. Microbiol.,
16, 59 (1957).
20. Garrett, M.T., Jr., and Sawyer, C.N., "Kinetics of Re-
moval of Soluble BOD by Activated Sludge", Proc. 7th
Industrial Waste Conf., Purdue Univ., Lafayette, Indiana
(1952).
21. Hoover, S.R.f Jasewicz, L., Pepinsky, J.B., and Porges,
N., "Assimilation of Dairy Wastes by Activated Sludge",
Sew, and Ind. Wastes, 23, 167 (1951).
22. Hoover, S.R., Jasewicz, L., and Porges, N., "Biochemical
Oxidation of Dairy Wastes", Proc. 9th Industrial Waste
Conf., Purdue Univ., Lafayette, Indiana(1954).
23. McKinney, R.E., "Mathematics of Complete Mixing Acti-
vated Sludge", Jour. San. Eng. Div., ASCE, 88, SA3, 87
(1962).
104
-------
24. McKinney, R.E., and Ooten, R.J., "Concepts of Complete
Mixing Activated Sludge", Trans 19th Conf. on San. Eng.,
Univ. of Kansas, Lawrence, Kansas (1969).
25. McCarty, P.L. and Broderson, C.F., "Theory of Extended
Aeration Activated Sludge", Jour. Water Poll. Control
Fed., 3£, 1095 (1962).
26. Storer, F.F., and Guady, A.F., Jr., "Computational
Analysis of Transient Response to Quantitative Shock
Loadings of Heterogeneous Popultations in Continuous
Culture", Environmental Science and Technology, 3,
143 (1969).
27. Ferret, C.J., "A New Kinetic Model of a Growing Bacter-
ial Population", Jour. Gen. Microbiol., 22, 589 (1960).
28. Burkhead, C.E., and McKinney, R.E., "Application of
Complete-Mixing Activated Sludge Design Equations to
Industrial Wastes", Jour. Water Poll. Control Fed., 40,
557 (1968).
29. American Public Health Association, American Water Works
Association, and Water Pollution Control Federation,
Standard Methods for the Examination of Water and Waste-
water, 12th Ed., Amer. Pub. Health Assoc., New York
(1965).
30. Milazzo, G., Electrochemistry, Elsevier Publ. Co., New
York, N.Y. (1963).
31. Baker, L.H., Jr., "Design and Construction of a Con-
tinuous Monitoring Digital Printout System", Master of
Science Thesis, New Mexico State Univ., University Park,
New Mexico (1967).
32. American Society for Testing Materials, Manual on In-
dustrial Water and Industrial Waste Water, 2nd Ed.,
ASTM Special Publication No. 148-H, 510 (1965).
33. Burkhead, C.E., "Energy Relationships in Aerobic Micro-
bial Metabolism", PhD Dissertation, Univ. of Kansas,
Lawrence, Kansas (1966).
34. Schmid, L.A., "Optimization of Phosphorous Removal with
Lime Treatment", PhD. Dissertation, Univ. of Kansas,
Lawrence, Kansas (1968).
35. Abu Samra, A.J., "Effect of Substrate Variation in
Aeration Only, Complete Mixing, Activated Sludge Systems"
Master of Science Thesis, Univ. Of Kansas, Lawrence,
Kansas (1965).
105
-------
36. Engelbrecht, R.S., and McKinney, R.E., "Membrane Filter
Applied to Activated Sludge Suspended Solids Deter-
minations", Sew, and Ind. Wastes, 28, 1321 (1956).
37. Prakasam, T.B.S., and Dondero, N.C., "Aerobic Hetero-
tropic Bacterial Population of Sewage and Activated
Sludge I. Enumeration", Appl. Microbiol., 15, 461 (1967).
38. Sawyer, C.N., Callejas, P., Moor, M., and Tom, A.Q.Y.,
"Primary Standards for BOD Work", Sew, and Ind. Wastes,
2£, 26 (1950).
39. Ballanger, D.G., and Lishka, R.J., "Reliability and
Precision of BOD and COD Determinations", Jour. Water
Poll. Control Fed., _34, 470 (1962).
40. Burkhead, C.E., and Waddell, S.L., "Composition Studies
of Activated Sludges", Proc. 24th Industrial Waste Conf.
Purdue Univ., Lafayette"^ Indiana (1969).
41. Gaudy, A.F., Jr., Komolrit, K., and Bhatla, M.N.,
"Sequential Substrate Removal in Heterogeneous Popula-
tions", Jour. Water Poll. Control Fed., 35, 903 (1963).
42. Thabaraj, G.J., and Gaudy, A.F., Jr., "Effect of Dis-
solved Oxygen Concentration on the Metabolic Response
of Completely Mixed Activated Sludge", Proc. 24th In-
dustrial Waste Conf., Purdue Univ., Lafayette, Indiana
(1969) .
43. Gaffney, P.E., and Heukelekian, H., "Oxygen Demand of
the Lower Fatty Acids", Sew, and Ind. Wastes, 30, 673
(1958).
44. Carter, J.L., "The Effect of Loading Rates on the
Metabolism of Glucose by Activated Sludge," PhD Disserta-
tion, Univ. of Kansas, Lawrence, Kansas (1968).
45. Adams, C.E., and Eckenfelder, W.W., Jr., "Response of
Activated Sludge to Organic Transient Loadings", Jour=.
San. Eng. Div., ASCE, 96. SA2, 333 (1970)
106
-------
SECTION XI
PUBLICATIONS AND PATENTS
The following publications have been produced during the
course of this project:
Agnew, R.W., "The Oxygen Uptake of a Biological Culture
Subjected to Transient Organic Loadings", Ph.D.
Dissertation, Univ. of Kansas, Lawrence, Kansas
(1968). Available from, University Microfilms,
Dissertation Copies, P.O. Box 1764, Ann Arbor,
Michigan, 48106.
Chun, M.J., "Oxygen Response of a High Solids Completely
Mixed Activated Sludge System to Transient Loadings"
Ph.D. Dissertation, Univ. of Kansas, Lawrence,
Kansas (1970). Available from University Microfilms
at above address.
Agnew, R.W., and O'Brien, W.J., "The Oxygen Uptake Re-
sponse of an Activated Sludge System to Changes in
Influent Substrate Concentration", Presented at
the 42nd Annual Conference, Water Pollution Control
Federation, Dallas, Texas (1969).
O'Brien, W.J., Agnew, R.W., and Chun, M.R., "A Continuous
Flow Automatically Recording Respirometer", accepted
for publication in Biotechnology and Bioengineering.
/
No patents have been applied for in connection with this
research.
107
-------
SECTION XII
GLOSSARY
A - The oxygen, uptake rate due to synthesis of the influent
biodegradable organic load at time (t ) .
Ac t inomycete - A large and distinctive group of eubacteria.
The actinomycetes are coenocytic organisms with a character-
istic mycelial vegetative structure, analogous to that which
exists in higher fungi.
Activated Sludge Process - A biological wastewater treatment
process in which a mixture of wastewater and activated sludge
is agitated and aerated. The activated sludge is subsequent-
ly separated from the treated wastewater (mixed liquor) by
sedimentation and wasted or returned to the process as
needed .
Aeration Only Activated Sludge Process - A single pass acti-
vated sludge process without sedimentation and sludge re-
turn. All of the activated sludge is wasted with the efflu-
ent of the aeration tank.
Aerobic - Requiring, or not destroyed by, the presence of
free elemental oxygen.
Anaerobis - The absence of air or free (elemental) oxygen.
B - Correction for change in barometric pressure, mg/min
or the basal oxygen uptake rate during steady state opera-
tion.
Bacteria - A group of universally distributed, rigid, essent-
ially unicellular microscopic organisms lacking chlorophyll.
Bacteria usually appear as spheroid, rod-like, or curved
entities, but occasionally appear as sheets, chains, or
branched filaments. Bacteria are usually regarded as plants.
Basal Rate - The oxygen demand rate created by endogenous
respiration and nitrogenous oxidation.
Biochemical Oxygen Demand (BODs)- The quantity of oxygen
used in the biochemical oxidation of organic matter in a
specified time, at a specified temperature, and under speci
fied conditions. A standard test used in assessing waste-
water strength.
Biodegradable - The character of a substance which allows
its destruction or metabolism by microorganisms populating
soils, natural bodies of water, or wastewater treatment
systems .
109
-------
BpDu - Ultimate biochemical oxygen demand of the influent,
"Y~u
mg/L.
Bulking Sludge - An activated sludge that settles poorly
because of a floe of low density.
C - The increase in basal rate due to the buildup of cell
mass from the start of the transient until time (t.).
Cell Yield - Refers to the production of microbial solids
from a given food source under controlled environmental
conditions.
Chelation - The formation of an inner complex compound
soluble in water in which the same molecule is attached
to a central atom at two different points, forming a ring
structure.
Chemical Oxygen Demand (COD) - A measure of the oxygen-
consuming capacity of inorganic and organic matter present
in water or wastewater. It is expressed as the amount of
oxygen consumed from a chemical oxidant in a specific test.
It does not differentiate between stable and unstable organic
matter and does not necessarily correlate with biochemical
oxygen demand. Also known as OC and DOC, oxygen consumed
and dichromate oxygen consumed, respectively.
Declining Growth - The condition of biological growth where
the food supply is inadequate to meet the demands of the
microbial population. Also called a food limiting condition.
Detention Time - The theoretical time required to displace
the contents of a tank or unit at a given rate of discharge
(volume divided by rate of discharge).
Dilution Rate (D)- The influent flow rate into a reactor
which results in the dilution and washout of the reactor
contents.
Discrete Particles - Nonflocculant particles which remain dis-
crete in a settling process, i.e., they will not agglomerate
or flocculate into larger particles but remain as individual
particles during their subsidence in a quisicent condition.
Dissolved Oxygen (DO) - The oxygen dissolved in water, waste-
water, or other liquid, usually expressed in milligrams per
liter, parts per million, or percent of saturation. Abbrevi-
ated DO.
110
-------
•3-r- = -rr-2 - Oxygen utilization rate, mg/L/hr.
-3-r- - Total oxygen uptake rate at steady state, mg/L/hr.
Qtfs)
j f\
- Total oxygen uptake rate at any time during a step
Ct) transient, mg/L/hr.
Effluent BODg - Five day biochemical oxygen demand of the
effluent.
Endogenous Respiration - The oxygen utilization process of
microorganisms caused by the oxidation of endogenous or
previously accumulated substances within the cells.
Equilibrium - A condition which exists within a biological
reactor where a process parameter remains constant with
time.
Error - A measure of the accuracy or the difference be-
tween a measured value and the true value in question. It
is often expressed as a percentage.
Filamentous Growth - Characterized by threadlike structures.
Filtrability - The ease or difficulty of solids separation
of a solid-liquid mixture by filtration.
Flocculation - In water and wastewater treatment, the agglo-
meration of colloidal and finely divided suspended matter
after coagulation by gentle stirring by either mechanical
or hydraulic means. In biological wastewater treatment
where coagulation is not used, agglomeration may be ac-
complished biologically.
Food Limiting - See Declining Growth conditions.
F - Concentration of BOD5 in the effluent, mg/L.
F^ - Concentration of BOD 5 in raw waste, mg/L.
dF
-=— - Food utilization rate, mg/L/hr.
Fungi - Small non-chlorophyll-bearing plants which lack
roots, stems or leaves, which occur (among other places)
in water, wastewater, or wastewater effluents and grow best
in the absence of light. Their decomposition after death
may cause disagreeable tastes and odors in water; in some
wastewater treatment processes they are helpful and in
111
-------
others they are detrimental.
Hydraulic Displacement or Washout - The physical removal
of liquid from a biological reactor by the displacement
of the reactor contents with the incoming wastewater flow.
Inhibitory - A stopping or slowing down of a biological
process by the introduction and/or buildup of process re-
tarding substances antagonistic to the microorganisms.
K, - BODg factor for converting active mass to oxygen
equivalent (not temperature dependent because the BOD$ test
is performed at 20°C).
K - Endogenous respiration constant (temperature dependent).
"™xi
K - Metabolism constant (temperature dependent).
K - Synthesis constant (temperature dependent) or substrate
concentration when the specific growth rate is one half the
maximum specific growth rate.
Load, Loading Condition, Loading Rate - The application of
liquid or contaminants to a wastewater treatment system or
to a body of water in terms of gallons or pounds, respect-
ively, per unit volume or mass of the reactor per unit time.
Ma - Active microbial mass, mg/L
May - Active microbial mass in the return sludge, mg/L.
* - Rate of change in active mass,mg/L/hr.
Me - Endogenous respiration mass, mg/L.
Mean Residence Time - The average time that liquid is de-
tained in a biological reactor as determined by the quotient
of the reactor volume by the influent flow rate.
Metabolism - The process in which food is utilized and
wastes formed by living matter.
M.J. - Inert, non-biodegradable organic suspended solids in
tne aeration tank, mg/L VSS.
MT - Inert, non-biodegradable organic solids in influent,
inf mg/L VSS
112
-------
M - Inert, inorganic suspended solids in the aeration
tank, mg/L SS.
M.J..J. - Inert, inorganic suspended solids in influent,
inf ash fraction of influent suspended solids, mg/L SS.
MLSS - Mixed liquor suspended solids, mg/L.
MLVSS - Mixed liquor volatile suspended solids, mg/L.
MT - Same as MLSS
Nitrification - An aerobic biological process where ammonia
is oxidized to nitrites and nitrates.
Non-biodegradable - The character of a substance which make
it resistant to biological degradation.
Nutrient - A food source for microorganisms.
O-(E) - Oxygen supplied by electrolysis.
02(net) - Oxygen used by the culture, mg/min.
0, - Steady state basal oxygen uptake rate, mg/L/hr.
0, - Increase in basal oxygen uptake rate during a step
transient, mg/L/hr.
0 - Steady state oxygen uptake rate due to synthesis,
ss mg/L/hr.
O . - Oxygen uptake rate due to synthesis during a step
trans ient, mg/L/hr.
Oxygen Equivalents - The amount of elemental oxygen theoretic-
ally required to oxidize a given amount of organic material
to carbon dioxide and water.
Oxygen Limitation, Oxygen Limiting - Condition of a microbial
culture where the dissolved oxygen concentration is the
limiting factor in the metabolic process.
Oxygen Uptake, Oxygen Uptake Rate See
£ - Oxygen demand constant.
Polyelectrolyte - Complex organic polymer containing
ionizable groups. Use in the wastewater field for the re-
moval of colloidal and particulate contaminants.
113
-------
Protoplasm - The substance of all living cells.
Protozoa - Small one-celled, animals including amoebae,
ciliates, and flagellants.
Q - Rate of flow for the raw waste, L/hr.
- Rate of flow for the return sludge, L/hr.
Respirometer - An instrument used to measure the respira-
tion rate of microorganisms.
S_ - Substrate concentration in the reactor.
S - Influent substrate concentration
Secondary Wastewater Treatment - The treatment of waste-
water by biological methods after primary treatment by sedi-
mentation.
Sedimentation - The process of subsidence and deposition
of suspended matter carried by water, wastewater, or other
liquids, by gravity. It is usually accomplished by reducing
the velocity of the liquid below the point at which it can
transport the suspended material. Also called settling.
Shock Loading - The addition of liquid or waste contaminants
to a wastewater treatment system in excess or less than that
previously added to created an equilibrium condition in the
system.
Sludge Wasting - The sludge produced in an activated
sludge process that is not needed to maintain the process
and therefore not returned to the aeration tank.
Solids Dewatering - The process of removing a part of the
water in sludge by any method such as draining, evaporation,
pressing, vacuum filtration, centrifuging, exhausting, pass-
ing between rollers, acid flotation, or dissolved-air
flotation with or without heat. It involves reducing from
a liquid to a spadable condition rather than merely changing
the density of the liquid (concentration) on the one hand
or drying (as in a kiln) on the other.
Solids Recycle - The return of a concentrated activated
sludge (usually by secondary sedimentation) to the aeration
tank in order to increase the solids concentration in the
tank .
SS - Suspended solids, mg/L.
114
-------
Standard Deviation - A measure of the reproducibility of
a te&t or measurement.
Steady State - See Equilibrium.
Substrate - See Nutrient.
Supernatant - The liquid standing above a sediment or pre-
cipitate.
t - Aeration time based on raw waste flow or mean residence
t"ime in the aeration basin, hr.
t - Sludge turnover time, hr.
t. - Elapsed time since start of the transient, hr.
"""w
T - Temperature.
Total Oxygen Demand (TOD) - The oxygen demand of a waste-
water when all of its constituents are completely oxidized.
Toxic - The property of a substance to poison a biological
system and inhibit or stop its processes. See Inhibit.
Trace Metals - Metallic elements of dilute concentration
necessary to support biological life.
Transient - An unsteady state or nonequilibrium condition
where the concentration of a given substance varies with
time.
Ultimate BOD - The total biochemical oxygen demand that
would be exerted if all of a biodegradable substrate were
oxidized to CO2 and H20.
V - Volume of aeration basin, liters, or the liquid volume
pumped through reactor, liters/min.
VSS - Volatile suspended solids, mg/L.
Yield Factor (Y) - Dry weight of cells formed per unit
weight of substrate utilized.
115
-------
116
-------
SECTION XIV
APPENDICES
Page
A. Bibliography on Theoretical and Applied Re-
search on Activated Sludge and Other Continuous
Culture Systems 118
117
-------
Appendix A
Bibliography on Theoretical and Applied Research on
Activated Sludge and Other Continuous
Culture Systems
1. Abu Samra, A. J., "Effect of Substrate Variation in
Aeration Only, Complete Mixing, Activated Sludge
Systems," Master of Science Thesis, Univ. of Kansas,
Lawrence, Kansas (1965).
2. Adams, C. E., and Eckenfelder, W. W., Jr., "Response of
Activated Sludge to Organic Transient Loadings,"
Jour. San. Eng. Div.. ASCE, 96. SA2,333 (1970).
3. Agnew, R. W., "The Oxygen Uptake of a Biological Culture
Subjected to Transient Organic Loadings," Ph.D Dis-
sertation, Univ. of Kansas, Lawrence, Kansas (1968).
4. Arthur, R. M., "Automatically Recording Respirometer,"
Appl. Microbiol. 13. 125 (1965).
5. Baker, L. H., Jr., "Design and Construction of a Con-
tinuous Monitoring Digital Printout System," Master
of Science Thesis, New Mexico State Univ., University
Park, New Mexico (1967).
6. Burkhead, C. E., and McKinney, R. E., "Application of
Complete-Mixing Activated Sludge Design Equations
To Industrial Wastes," Jour. Water Poll. Control Fed.
40. 557 (1968).
7. Burkhead, C. E., and Wood, D. J., "Process Optimization
Using the Analog Computer," Second National Sympo-
sium on San. Enqr. Research. Development, and Design.
Cornell Univ., Ithaca, New York (1969).
8. Bush, A.W., "Treatability versus Oxidizability of In-
dustrial Wastes and the Formulation of Design
Criteria," Proc. 16th Industrial Wastes Conf., Pur-
due Univ., Lafayette, Indiana (1961).
9. Bush, A. W., Grady, L., Jr., Rao, T. S., and Swilley,
E. L., "Short Term Total Oxygen Demand Test," Jour.
Water Poll. Control Fed., 34. 354 (1962).
10. Caldwell, D. H., and Langelier, W. F., "Manometric Mea-
surement of the Biochemical Oxygen Demand of Sewage,"
Sewage Works Jour.. 20, 202 (1948).
118
-------
11. Carter, J. L., "The Effect of Loading Rates on the Met-
abolism of Glucose by Activated Sludge," Ph.D.
Dissertation, Univ. of Kansas, Lawrence, Kansas,
(1968).
12. Cassell, E. A., "Dynamics of Continuous Mixed Cultures,"
Ph.D. Dissertation, Univ. of North Carolina at
Chapel Hill, North Carolina (1964).
13. Clark, J. W., "Continuous Recording B.O.D. Determination,"
Water and Sewage Works. 107, 140 (1960).
14. Coe, R. H., "Bench Scale Biological Oxidation of Refinery
Wastes with Activated Sludge," Sew, and Ind. Wastes,
24, 731 (1952).
15. Contois, D. E., "Kinetics of Bacterial Growth; Relation-
ship Between Population Density and Specific Growth
Rate of Continuous Cultures," Jour. Gen. Microbiol.,
21, 40 (1959).
16. Contois, D. E., and Yango, L. D., "Studies of Steady
State, Mixed Microbial Populations," Abstracts 148th
Meeting. Amer. Chem. Soc., 17Q (1964).
17. Dawkins, G. S., "Mixing Patterns and Residence Time Pre-
dictions," Proc. 18th Industrial Waste Conf., Purdue
Univ., Lafayette, Indiana (1963).
18. Eckenfelder, W. W., "Kinetics of Biological Oxidation,"
Biol. Treat, of Sew, and Ind. Wastes, Vol. I,
Aerobic Oxidation, 18-34, Reinhold Publishing Co.
New York (1956).
19. Eckenfelder, W. W. and 0'Conner, D. J., Biological Waste
Treatment. Pergamon Press, Ltd. London (1961).
20. Eckenfelder, W. W., "Application of Kinetics of Acti-
vated Sludge to Process Design," Advances in Biolog-
ical Waste Treatment, Pergamon Press (1963).
21. Eckenfelder, W. W., "A Theory of Activated Sludge Design
for Sewage," The Act. Sludge Process in Sew. Treat.
Theory and Application., Univ. of Michigan, Ann
Arbor, Michigan (1966).
22. Eckenfelder, W. W., Industrial Water^ Pollution Control,
McGraw-Hill, New York (1966).
119
-------
23. Ecker, R. E., and Lockhart, W. R., "Relationships Be-
tween Initial Nutrient Concentration and Total
Growth," Jour, of Bact.. 82. 80 (1961).
24. Ecker, R. E., and Lockhart, W. R., "Specific Effects of
Limiting Nutrient on Physiological Effects During
Culture Growth," Jour, of Bact., 82. 511 (1961).
25. Eckhoff, D. W., and Jenkins, D., "Transient Loading
Effects in the Activated Sludge Process," Third
International Conference on Water Pollution Research,
Munich, Germany (1966).
26. Eckhoff, D. W., and Jenkins, D., "Activated Sludge Sys-
tems: Kinetics of the Steady and Transient States,"
SERL Report No. 67-12. Univ. of Calif., Berkeley,
California (1967).
27. Erickson, L. E., and Fan, L. T., "Optimization of the
Hydraulic Regime of Activated Sludge Systems," Jour.
Water Poll. Control Fed.. 40. 345 (1968).
28. Fischerstrom, N. C. H., "Low Pressure Aeration of Water
and Sewage," Jour. San. Enq. Div., ASCE, 86, SAS,
21 (1960).
29. Fredrickson, A. G., and Tsuchiya, H. M., "Continuous
Propagation of Microorganisms," Amer. Inst. Chem.
Enars. Jour., j), 459 (1963) .
30. Gates, W. E., and Marlar, J. T., "Graphical Analysis of
Batch Culture Data Using the Monod Expressions,"
Jour. Water Poll. Control Fed.. 40. R 469 (1968).
31. Garrett, M. T., Jr. and Sawyer, C. N., "Kinetics of Re-
moval of Soluble BOD by Activated Sludge," Proc. 7th
Industrial Waste Conf.. Purdue Univ., Lafayette,
Indiana (1952).
32. Gaudy, A. F., Jr., Engelbrecht, R. S., and Demoss, R. D.,
"Laboratory Scale Activated Sludge Unit," Appl.
Microbiol.. 8, 298 (1960).
33. Gaudy, A. F., Jr., and Engelbrecht, R. S., "Quantitative
and Qualitative Shock Loadings of Activated Sludge
Systems," Jour. Water Poll. Control Fed.. 33. 800
(1961).
34. Gaudy, A. F., Jr., "Shock Loading Activated Sludge with
Spent Sulfite Pulp Mill Wastes," Jour. Water Poll.
Control Fed., 34, 124 (1962).
120
-------
35. Gaudy, A. F., Jr., Komolrit, K., and Bhatla, M. N.,
"Sequential Substrate Removal in Heterogeneous Pop-
ulations," Jour. Water Poll. Control Fed., 35, 903
(1963).
36. Gaudy, A. F., Jr., and Turner, B. G., "Effect of Air
Flow Rate on Response of Activated Sludge to Quan-
titative Shock Loading," Jour. Water Poll. Control
Fed., 36, 767 (1964).
37. Gaudy, A. F., Jr., and Gaudy, E. T., "Microbiology of
Waste Waters," Annual Review of Microbiology, 20,
319 (1966).
38. Gaudy, A. F., Jr., Ramanathan, J., and Rao, B. S.,
"Kinetic Behavior of Heterogeneous Populations in
Completely Mixed Reactors," Biotechnology and Bio-
engineer incr. j., 383 (1967) .
39. Gram, A. L., III, "Reaction Kinetics in Aerobic Biolog-
ical Processes," SERL Report No. 2, I.E.R. Series 90,
Univ. of Calif., Berkeley, California (1956).
40. Greenhalgh, R. E., Johnson, R. L., and Nott, H. D.,
"Mixing in Continuous Reactors," Chem. Enq. Proqr.,
55. 44 (1959).
41. Grieves, R. B., Milbury, W. F., and Pipes, W. 0., "Mix-
ing Model for Activated Sludge," Proc. 18th Indus-
trial Waste Conf., Purdue Univ., Lafayette, Indiana
(1963).
42. Grieves, R. B., Milbury, W. F., and Pipes, W. 0., "A
Mixing Model for Activated Sludge," Jour. Water Poll.
Control Fed.. 36, 619 (1964).
43. Grieves, R. B., Milbury, W. F., and Pipes, W. O., "The
Effect of Short Circuiting Upon the Completely Mixed
Activated Sludge Process," Int. Jour. Air & Water
Poll. . 8, 199 (1964).
44. Hatfield, R., and Strong, E., "Small Scale Laboratory
Units for Continuously-Fed Biological Treatment
Units. I. Aeration Units for Activated Sludge,"
Sew, and Ind. Wastes, 26. 1255 (1954).
45. Hawkes, H. A., The Ecology of Waste Water Treatment,
Pergamon Press (1963) .
121
-------
46. Helmers, E. N., Frame, J. D., Greenberg, A. E., and
Sawyer, C. N., "Nutritional Requirements in the Bio-
logical Stabilization of Industrial Wastes. II.
Treatment with Domestic Sewage," Sew, and Ind.
Wastes. 2JJ, 884 (1951) .
47. Herbert, D., Elsworth, R. and Telling, R. C., "The Con-
tinuous Culture of Bacteria; a Theoretical and Ex-
perimental Study," Jour. Gen. Microbiol., 14, 601
(1956) .
48. Herbert, D., "Some Principles of Continuous Culture,
Recent Progress in Microbiology, Charles C. Thomas,
Springfield, Illinois, 381 (1959).
49. Herbert, D., "A Theoretical Analysis of Continuous Cul-
ture Systems," Continuous Culture of Microorganisms
S.C.I. Monograph No. 12, MacMillan, New York (1961).
50. Hetling, L. J., and Washington, D. R., "Kinetics of the
Steady-State Bacterial Culture III. Growth Rate,"
Proc. 20th Industrial Waste Conf., Purdue Univ.,
Lafayette, Indiana (1965).
51. Hetling, L. J., Washington, D. R., and Rao, B. S.,
"Kinetics of the Steady-State Bacterial Culture II.
Variations in Synthesis," Int. Jour. Air and Water
Poll., .10, 357 (1966).
52. Hiser, L. L., and Busch, A. W., "An 8-Hour Biological
Oxygen Demand Test Using Mass Culture Aeration and
C.O.D.," Jour. Water Poll. Control Fed., 36, 505
(1964) .
53. Hoover, S. R., Jasewicz, L., Pepinsky, J. B., and Porges,
N., "Assimilation of Dairy Wastes by Activated
Sludge," Sew, and Ind. Wastes. 23, 167 (1951).
54. Hoover, S. R., Jasewicz, L., and Porges, N., "Biochemical
Oxidation of Dairy Wastes," Proc. 9th Industrial
Waste Conf., Purdue Univ., Lafayette, Indiana (1954).
55. Jenkins, D., and Garrison, W. E., "Control of Activated
Sludge by Mean Cell Residence Time," Jour. Water
Poll. Control Fed.. 40. 1905 (1968).
56. Kalinske, A. A., "Pilot Plant Tests on High Rate Oxida-
tion of Sewage," Water and Sewage Works, 97, 175
(1950).
122
-------
57. Kalinske, A. A., and Bush, A. W., "New Equipment for the
Activated Sludge Process," Water and Sewage Works.
103. 324 (1956).
58. Kehr, R. W., "Detention of Liquids Being Mixed in Con-
tinuous Flow Tanks, Sew. Works Jour.. 8, 915 (1936).
59. Keshavan, K., Behn, V. C., and Ames, W. P., "Kinetics of
Aerobic Removal of Organic Wastes," Jour. San. Eng.
Div.. ASCE, 90, SA1, 99 (1964).
60. Knopp, P. V., "Frequency Response Analysis of the Act-
ivated Sludge Process," D. Sc. Dissertation, Univ.
of Wisconsin, Madison, Wisconsin (1967).
61. Knopp, P. V., Watts, D. G., and Rohlich, G. A., Tran-
sients in the Activated Sludge Process," Proc. 23rd
Industrial Waste Conf.. Purdue Univ., Lafayette,
Indiana (1968).
62. Komolrit, K. and Gaudy, A. F., Jr., "Substrate Interaction
During Shock Loadings to Biological Treatment Pro-
cesses," Proc. 19th Industrial Waste Conf., Purdue
Univ., Lafayette, Indiana (1964).
63. Komolrit, K., and Gaudy, A. F., Jr., "Biochemical Res-
ponse of Continuous-Flow Activated Sludge Processes
to Qualitative Shock Loadings," Jour. Water Poll.
Control Fed.. 38. 85 (1966).
64. Komolrit, K. and Gaudy, A. F.,^Jr., "Substrate Inter-
action During Shock Loadings to Biological Treat-
ment Processes," Jour. Water Poll. Control Fed., 38,
1259 (1966).
65. Kono, T., and Asai, T., "Kinetics of Continuous Culti-
vation," Biotechnology and Bioenqineerinq, 11, 19
(1969) .
66. Kraus, L. S., "Dual Aeration as a Rugged Activated
Sludge Process," Sew, and Ind. Wastes. 27. 1347 (1955),
67. Kubitschek, H. E., "The Error Hypothesis of Mutation,"
Science. 131. 730 (1960).
68. Kubitschek, H. E., and Gustafson, L. A., "Mutation in
Continuous Cultures. III. Mutational Responses in
Escherichia Coli," Jour, of Bacteriol., 88, 1595
(1964).
123
-------
69. Larsen, D. H., and Dimmick, R. L. , "Attachment and
Growth of Bacteria on Surfaces of Continuous-
Culture Vessels," Jour, of Bacteriol., 88, 1380
(1964).
70. Ludzack, F. J., "Laboratory Model Activated Sludge Unit,"
Jour. Water Poll. Control Fed.. 32, 605 (1960).
71. Luedeking, R., and Piret, E. L., "Transient and Steady
States in Continuous Fermentation - Theory and
Experiment," Jour. Biochem. Microbiol. Tech. and
Enq. , 1, 431 (1959).
72. McCabe, J. and Eckenfelder, W. W., "BOD Removal and
Sludge Growth in the Activated Sludge Process,"
Jour. Water Poll. Cont. Fed., 33, 258 (1961).
73. McCarty, P. L. and Broderson, C. F., "Theory of Extended
Aeration Activated Sludge," Jour. Water Poll. Cont.
Fed.. 34. 1095 (1962).
74. McCarty, P. L. , "Thermodynamics of Biological Synthesis
and Growth," Second International Conference on
Water Pollution Research, Tokyo, Japan (1964).
75. McKinney, R. E., Symms, J. N., Shiftrin, W. G. and
Vezina, M., "Design and Operation of a Complete Mix-
ing Activated Sludge Waste Treatment Plant," Sewage
and Ind. Wastes, 30, 287 (1958).
76. McKinney, R. E., "Complete Mixing of Activated Sludge,"
Water and Sewage Works, 107, 69 (1960).
77. McKinney, R. E. and Edde, H., "Aerated Lagoon for Sub-
urban Sewage Disposal," Jour. Water Poll. Control
Fed., 33, 1277 (1961) .
78. McKinney, R. E. and Benjes, H. H., Jr., "Evaluation of
Two Aerated Lagoons," Jour, of San. Enqr. Div., ASCE,
_91, SA6, 43 (1965).
79. McKinney, R. E., "Mathematics of Complete-Mixing Acti-
vated Sludge," Jour. San. Ena. Div., ASCE, 88, SA3,
87 (1962).
80. McKinney, R. E., and Ooten, R. J., "Concepts of Complete
Mixing Activated Sludge," Trans. 19th Conf. on San.
Enq., Univ. of Kansas, Lawrence, Kansas (1969).
124
-------
81. McLellan, J. C., "Aspects of the Response of a Mixed
Microbial Culture to Variations in Loadings," Ph.D.
Dissertation, Rice Univ., Houston, Texas (1969).
82. McLellan, J. C., and Busch, A. W., "Hydraulic and Pro-
cess Aspects of Reactor Design I. Basic Concepts in
Steady-State Analysis," Proc. 22nd Industrial Waste
Conf., Purdue Univ., Lafayette, Indiana (1967).
83. McLellan, J. C. and Busch, A. W., "Hydraulic and Pro-
cess Aspects of Reactor Design II. Response to
Variations in Loading," Proc. 24th Industrial Waste
Conf.. Purdue Univ., Lafayette, Indiana (1969).
84. Martin, E. J., and Washington, D. R., "Kinetics of the
Steady-State Bacterial Culture I. Mathematical Model,"
Proc. 19th Industrial Waste Conf., Purdue Univ,,
Lafayette, Indiana (1964).
85. Martin, E. J., and Washington, D. R., "Kinetics of the
Steady-State Bacterial Culture I. Mathematical
Model," Int. Jour. Air and Water Poll.., 10, 343
(1966).
86. Mateles, R. I., and Chian, S. K. , "Kinetics of Substrate
Uptake in Pure and Mixed Culture," Environmental
Science and Technology. 3_r 569 (1969)..
87. Maxon, W. D., "Continuous Fermentationr a Discussion of
Its Principles and Applications," Appl. Microbiol.,.
1, 110 (1955).
88. Middlebrooks, E. J., and Garland, C. F., "Kinetics of
Model and Field Extended Aeration Wastewater Treat-
ment Units," Jour. Water Poll. Control Fed., 40, 586
(1968).
89. Milbury, W. F., Pipes,. W. O. , and Grieves, R. B., "A
Laboratory Study of the Effect of Short Circuiting
Upon the Completely Mixed Activated Sludge Process,"
Int. Jour. Air and Water Poll.. _9, 41 (1965).
90. Milbury, W. F., Pipes, W. O., and Grieves, R. B., "Com-
partmentalization of Aeration Tanks," Jour. San.
Enqr. Div., ASCE, 91, SA3, 45 (1965).
91. Milbury, W. F., Pipes, W. O., and Grieves, R. B., "A
Laboratory Study of Mixing Conditions in Small
Aeration Vessels," Pxoc. 19th Industrial Waste Conf.,
Purdue Univ., Lafayette, Indiana (1964).
125
-------
92. Monod, J., Recherces sur la Croissance des Cultures
Bacteriennes. Hermann and Cie, Paris (1942).
93. Monod, J., "The Growth of Bacterial Cultures," Ann. Rev.
Microb.. 1, 371 (1949).
94. Monod, J., "La Technique de Culture Continue; The'orie
et Applications," Annals Institute Pasture. 79, 390
(1950).
95. Moser, J., "Contributions to the Theory of the Contin-
uous Bacterial Growth Apparatus. I. Kinetics of
Growth Homogeneous Populations," Proc. Natl. Acad.
Sci.. 13, 222 (1957).
96. Moser, J., "The Dynamics of Bacterial Populations Main-
tained in the Chemostat," Carnegie Institute of
Washington, Publication No. 614 (1958).
97. Moser, J., "Structure and Dynamics of Bacterial Popula-
tions Maintained in the Chemostat," Cold Spring
Harbor Sym. Quant. Biol.. 22, 121 (1959).
98. Moss, F. J., Rickard, P. A. D., Beech, G. A., and Bush,
F. E., "The Response by Microorganisms to Steady-
State Growth in Controlled Concentrations of Oxygen
and Glucose I. Candida vttilis." Biotechnology and
Bioengineering. 11. 561 (1969).
99. Murphy, K. L. and Timpany, P. L., "Design and Analysis of
Mixing for an Aeration Tank," Jour. San. Engr. Div.,
ASCE, 93, SA5, 1 (1967).
100. Northam, J. I., "The Course of Bacterial Population
Growth in Batch and Continuous Culture According to
the Theory of Monod," J. Biochem. Microbiol. Techn.
and Eng.. 1, 349 (1959).
101. Novick, A., and Szilard, L., "Experiments With the Chem-
ostat on Spontaneous Mutations of Bacteria," Proc.
National Academy of Science, Washington, D. C., 36,
708 (1950).
102. Novick, A., "Growth of Bacteria," Ann. Rev. Microbiol..
.9, 97 (1955) .
103. O'Brien, W. J., "Continuous Monitoring of the Biochem-
ical Oxygen Demand of Some Organic Wastes," D. Sc.
Dissertation, New Mexico State Univ., University
Park, New Mexico (1965).
126
-------
104. Ferret, C. J., "A New Kinetic Model of a Growing Bac-
terial Population," Jour. Gen. Microbiol., 22, 589
(1960).
105. Phillips, D. H., and Johnson, M. J., "Aeration in Fer-
mentations," Jour. Biochem. Microbiol. Tech. and
Enq.. 1, 277 (1961).
106. Pinaeva, G. V., "The Effect of Prolonged Vegetative
Reproduction on the Physiological Properties of Cl.
acetobutylicum." Mikrobiolocriya. 28. 465 (1959).
107. Pipes, W. O., Milbury, W. F., and Grieves, R. B., "Com-
parison of the Axial Dispersion and Volume Appor-
tionment Methods for Describing Mixing Conditions
in an Aeration Tank," Proc. 19th Industrial Waste
Conf., Purdue Univ., Lafayette, Indiana (1964).
108. Pirt, S. J., "The Oxygen Requirements of Growing Cul-
tures of an Aerobacter Species Determined by Means
of the Continuous Culture Technique," Jour. Gen.
Microbiol., 16. 59 (1957).
109. Polonesik, S., Grieves, R. B., and Pipes, W. O., "Pro-
cess Optima in Activated Sludge," Proc. 20th In-
dustrial Waste Conf., Purdue Univ., Lafayette,
Indiana (1965).
110. Powell, E. O., "Growth Rate and Generation Time of
Bacteria," Jour. Gen. Microbiol.. 15. 492 (1956).
111. Powell, E. O., "Criteria for the Growth of Contaminants
and Mutants in Continuous Culture," Jour. Gen.
Microbiol.. JL8, 259 (1958) .
112. Powell, E. O., "Discussion of Symposium Six," Recent
Progress in Microbiology, Charles C. Thomas, Spring-
field, Illinois (1959).
113. Reynolds, T. D., and Yang, J. T., "Model of the Com-
pletely Mixed Activated Sludge Process," Proc. 21st
Industrial Waste Conf., Purdue Univ., Lafayette,
Indiana (1966).
114. Rickard, M. D., "The Effect of Agitation on the Behavior
of Completely Mixed Bacterial Systems," Ph.D.
Dissertation, Oklahoma State Univ., Stillwater,
Oklahoma (1968).
127
-------
115. Rickhard, M. D., and Gaudy, A. F., Jr., "Effect of
Oxygen Tension on Oxygen Uptake and Sludge Yield
in Completely Mixed Heterogeneous Populations,"
Proc. 23rd Industrial Waste Conf.. Purdue Univ.,
Lafayette, Indiana (1968).
116. Rickard, N. D., and Gaudy, A. F., Jr., "Effect of Mix-
ing Energy on Sludge Yield and Cell Composition,"
Jour. Water Poll. Control Fed.. 40. R219 (1968).
117. Schulze, K. L., "The Activated Sludge Process as a Con-
tinuous Flow Culture. I. Theory," Water and Sew-
age Works. 111. 526 (1964).
118. Schulze, K. L., "A Mathematical Model of the Activated
Sludge Process," Develop, in Ind. Microbiol.. 5,
258 (1964). ~
119. Schulze, K. L,, "The Activated Sludge Process as a Con-
tinuous Flow Culture. II. Application," Water and
Sewage Works. 112, 11 (1965).
120. Servizi, J. A., and Bogan, R. H., "Free Energy as a
Parameter in Biological Treatment," Jour. San. Eng.
Div.. ASCE, 89. SA3, 17 (1963).
121. Shindala, A., Bungay, H. R., Ill, Krieg, N. R., and
Culbert, K., "Mixed-Culture Interactions. I. Com-
mensalism of Proteus vulgaris with Saccharomyces
cerevisiae in Continuous Culture," Jour, of Bac-
teriol.. 89, 693 (1965).
122. Slezak, J., and Sikyta, B., "Continuous Cultivation of
Micro-organisms: A New Approach and Possibilities
for Its Use," Jour. Biochem. Microbiol. Tech. and
Encr.. 1, 357 (1961) .
123. Snaddon, X. V. M., and Jenkins, S. H., "Biological Oxi-
dation in a Self-Operating Respirometer," Second
International Conference on Water Pollution, Tokyo,
Japan (1964).
124. Spicer, C. C., "The Theory of Bacterial Constant Growth
Apparatus," Biometrics. 11. 225 (1955).
125. Stack, V. T., and Conway, R. A., "Design Data for Com-
pletely-Mixed Activated Sludge Treatment," Sew, and
Ind. Wastes. 31. 1181 (1959).
128
-------
126. Stewart, M. J., and Ludwig, J. F., "Theory of the MAS
Waste-Water Treatment Process, Part I," Water and
Sewage Works. 109. 53 (1962).
127. Stewart, M. J., and Ludwig, J. F., "Theory of the MAS
Waste-Water Treatment Process, Part II," Water and
Sewage Works. 109. 98 (1962).
128. Storer, F. F., and Gaudy, A. F., Jr., "Computational
Analysis of Transient Response to Quantitative
Shock Loadings of Heterogeneous Populations in Con-
tinuous Culture," Environmental Science and Tech-
nology. .3, 143 (1969).
129. Symons, J. M., and McKinney, R. E., "Biochemistry of
Nitrogen in the Synthesis of Activated Sludge,"
Sew, and Ind. Wastes. 30. 874 (1958).
130. Teissier, G., "Les Lois Quantitatives de la Croissance,"
Ann. Physiol. Physicochim., Biol.. 12, 527 (1936).
131. Tenny, M. W., Johnson, R. H., Jr., and Symons, J. M.,
"Minimal Solids Aeration Activated Sludge," Jour.
San. Ena. Div.. ASCE, 90. SA1, 23 (1964).
132. Tenney, M. W., and Stunun, W., "Chemical Flocculation of
Microorganisms in Biological Waste Treatment," Jour.
Water Poll. Control Fed., 37. 1370 (1965).
133. Thabaraj, G. J., and Gaudy/ A. F., Jr., "Effect of Dis-
solved Oxygen Concentration on the Metabolic Res-
ponse of Completely Mixed Activated Sludge," Proc.
24th Industrial Waste Conf.. Purdue Univ., Lafayette,
Indiana (1969) .
134. Thomas, H. A. and McKee, J. E., "Longitudinal Mixing
in Aeration Tanks," Sew. Works Jour.. 16. 42 (1944).
135. Tilsworth, T., "Field Evaluation of Modified High Rate
Activated Sludge," Master of Science Thesis, Univ.
of Nebraska, Lincoln, Nebraska (1967).
136. Weston, R. F. and Eckenfelder, W. W., "Application of
Biological Treatment to Industrial Wastes: I. Kin-
etics and Equilibria of Oxidative Treatment," Sew.
and Ind. Wastes. 27, 802 (1955).
137. Westberg, N., "A Study of the Activated Sludge Process
as a Bacterial Growth Process," Water Research, J.,
795 (1967).
129
-------
138. Willimon, E. P. and Andrews, J. F., "Kinetics of Multi-
stage Biological Processes," Presented at the 154th
National American Chemical Society Meeting Symposium
on Kinetics of Mixed Culture Systems, Chicago, Ill-
inois (1967).
139. Zaander, C., and Johnson, B., "Process Control for Act-
ivated Sludge," Proc. 22nd Industrial Waste Conf.,
Purdue Univ., Lafayette, Indiana (1968).
130
-------
1
5
Accession Number
2
Subject Field & Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Kansas University, Center for Research, Inc., Irving Hill Road, West Campus,
Lawrence, Kansas 66044
Title
OXYGEN CONSUMPTION IN CONTINUOUS BIOLOGICAL CULTURE
1 Q Authors)
O'Brien, Walter J.
Burkhead, Carl E.
16
21
Project Designation
WP01023-03
17050 DJS
Note
22
Citation
23
Descriptors (Starred First)
*Activated Sludge, *Aeration, *0xygen Requirements, Aerobic Treatment,
Organic Loading, Fermentation
25
Identifiers (Starred First)
*Respirometer
27
Abstract
A continuous flow automatically recording respirometer was used to study the response
of aeration only and aeration with sludge return completely mixed activated sludge systems
to step changes in the influent substrate. The experiments were conducted at 25°C with
glucose; a mixture of glucose, glutamate, and acetate; and a mixture of sewage solids plus
Metrecal.
Influent substrate concentrations were doubled in the 3-hour and tripled in the 6-hour
mean residence time aeration only experiments without increasing the soluble COD in the
effluent. Larger shocks produced temporary COD peaks in the effluent. These increases
were accompanied by peaks in the oxygen uptake rate in cultures metabolizing the soluble
substrates. The mixture of sewage solids and Metrecal did not produce a distinct peak in
oxygen demand during transient operation.
Decreases in the influent substrate concentrations produced rapid decreases in the
rate of oxygen utilization.
Concentration increases of up to 7.2 in the influent did not produce a change in the
effluent soluble COD of aeration with sludge return units. This was not the maximum limit
for the process.
A procedure for calculating the rate of oxygen uptake by a CMAS system at any time
during a step transient was developed.
Abstractor
Walter J. O'Brien
Institution
University of Kansas
WR:1O2 (REV. JULY 19691
WRSI C
SEND TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 20240
* GPO: 1969-359-339
------- |