Sequencing Batch Biological Reactors: An Overview Author(s): Robert L. Irvine and Arthur W. Busch Reviewed work(s): Source: Journal (Water Pollution Control Federation), Vol. 51, No. 2 (Feb., 1979), pp. 235-243 Published by: Water Environment Federation Stable URL: http://www.jstor.org/stable/25039819 . Accessed: 02/04/2012 13:04 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact
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reactors?
batch biological
Sequencing
an overview L.
Robert
of Notre
Irvine, University
Arthur W.
Ind.
Tex.
Dallas,
Busch,
Dame,
This issue of the Journal contains six additional papers (pp. 244-304) dealing with The papers that follow range in content from sequencing batch reactors (SBRs). basic research to periodic operation of full-scale continuous flow systems in Australia and will provide a general understanding The purpose of this of SBR operation. overview paper is to highlight the major characteristics of SBR systems and integrate the basic notions that span the other papers. The terminology used here is suggested as a standard for describing SBR systems, although it may differ from that found in the following papers.
environmental
Recent tions
some
in
that,
of effluent
instances,
re
has
legislation
in the promulgation
sulted
limita test
severely
the
continuous flow of conventional capabilities Modifi biological waste treatment facilities. both
cations,
simple
ous flow systems more
these removal
of
requirements. and phosphorus
nitrogen in aerobic
and
that systems zones.
to meet
Biological in some
for example,
applications,
demonstrated
can be made
simply Industrial
has been
nature
waste.
the
of
treatment.
include
cepts
of
Examples
shaft,
deep
rotating
and anaerobic contactors, filters, a wide These systems provide
treatment
treatment
ing
effluent
problems restrictions.
and
new
biological of
to
systems
cussed
above,
depends cost. to
(SBR)
is a batch
operation
very
treatment
the
the
(as opposed to
the
in
fac
in
the
phos
pretreat
that SBR systems are of
Studies
infancy.
nitrogen,
components research.
specific finally,
and
municipali as such
the
process
con
ducted at the University of Notre Dame were carried out with direct input from each major area
in the
form
of
an
six
sentatives
and
federal) design not be
principles known
been
agencies
industry. and until
developed,
and
three
(municipal
practices
can in
performance
Sufficient
however,
repre and
many
Nevertheless,
operating full-scale
is available.
formation has
firms
consulting from each
of mem
composed
(see Acknowledgments) from
committee
advisory
information
to establish
cer
tain design and operating criteria and to define the present capabilities of SBR systems.
dis
schemes batch
sequencing
similar
of
their
bers
flow.
ever-escalat
a number
in
user
con
spectrum
and,
systems treat
require
applications,
It must be understood
on
including contrast
ment;
unique
SBR
and
for
however,
low capital
industries
and
Final tors, In
in
costs;
phorus,
limitations expected should be considered.
selection
have
which
facilities
of
that
of priority pollutants,
those
Only
areas
application communities
have
are able to meet reliably and consistently that
ment
areas
application
removal
overland
the
primary in small
alone is ex
At present,
overlap.
modi
that must be matched
technology
the
the are
Complex
these
is expected,
As
panded.
pre
technology
treatment
alternate
treatment needs have resulted not only in such of conventional flow sheets, but modifications also in the development of new concepts in waste
treatment
of
spectrum
operating ties that
fications have been more varied and have been directed at the high-strength and multiple component
the
viously defined by CFS SBR and CFS
to continu
extensive,
(CFS)
stringent
municipal anoxic
and
in time what the CFS provides in space. Be cause of the periodic nature of SBR operation,
reactor
to continuous) flll-and-draw
in the original biological systems described waste treatment literature. The SBR provides
DESCRIPTION OF SYSTEM An SBR system may be composed more
tanks.
In
biological
waste
of one or treatment,
each tank in the system has five basic operat ing modes or periods, each of which is named February
1979
235
Irvine
and
1.
FIGURE fill
Busch
(Photo
meat-packing
to its primary function. and react, draw, settle, Fill receiving (the
sequence.
and draw
in each
React
to
time
(the
a given
to complete
time
settle
effluent)
for
cycle
complete
(the
reactions),
Okla.
The periods in a time idle, of raw waste)
of treated
(the discharge
occur
tank.
Photo
system. in Ada,
desired the
separate
organisms from the treated effluent), and idle the tank and be (the time after discharging fore refilling) can be eliminated depending on of
requirements
treatment
the
For
problem.
if an SBR system were being used
example,
each
only,
equalization
cycle
might
for in
only
volve fill and draw. The time for a complete cycle is the total time between beginning of fill to end of idle in a single-tank
between
and
system
one
that
to
The that
occur
valves.
in
for
236
either small
be may Minimal
Although
have
is applicable as
such situations, in the food-processing
rural used
towns to
flows
Journal WPCF,
for those indus
time
where regulate
operator
the single-tank
continuous
earthen
control
ditch in
box
during
foreground.
is
and
Vol.
51, No.
a
2
two-
system
effluent
tion
of
a multiple-tank minimum
Flow and plex. treatment required control.
bimonthly once each
load
can
in
is necessary. in a low-yield
reactor
each
This
for
Opera be either
or com input, and degree of the necessary
dictate
would
S.
may
until from
range
to
system
single-tank
in a high-yield cycle multiple-tank Solids be may accomplished wasting or during the react settle the period
system. after period. A
suitable
the U.
operator variations
remain
Organisms wasting
in
system
with
simple,
more
be
may
requirements
of
summary
ample
a
for 2.
Figure
the
As
complete can be
an
using
periods,
that highlights
ex
for one
the hydraulics
is presented cycle, seen the figure, from
in the
volume of liquid increases during the fill period some
from volume
initial
at a rate
to
volume
determined
by
the
maximum
flow
variations.
are react the solids wasted during as the volume remain would shown, period, at the maximum the settle and through period until The draw. volume the draw during
or
The
insets
distribution can
to
decreases
there during representation
required.
system has been used
in Australia,
the
period
clock
motors
input
three-tank
Unless
completed fill.
flow
noncontinuous try or control
must completing
system
single-tank
sys criterion
multiple-tank in sequence, the
reactor another
a
In
system. multiple-tank the reactors fill tem,
prior
aerated
reactor
beginning
of fill for the first reactor (arbitrarily defined) and the end of idle for the last reactor in a
being draw
shows Timer
of Jack L. Witherow.)
courtesy
according are fill,
must
single-tank waste
Existing
treating
be
seen,
the minimum
and
remains
the idle period. shown of
in Figure liquid
level
for each period the
energy
2 give and
a
pictorial organism
of one cycle.
provided
As
for mixing
Batch
Sequencing
an extended
SBR system with
T-1-r
little
accumulation a
sembles
of
fill period with re
substrate
soluble CFS.
mixed
completely
Reactors
Even without a detailed discussion of SBR the flexibility of the characteristics,
operating
is obvious. Clarification system are combined. a Either plug
and
reaction a
or
flow
com
The pletely mixed CFS can be simulated. SBR can provide directly for internal equali zation. 0.250
2.
FIGURE one
reactor
versus
volume
Liquid
time
for
aeration
is used
tion
of mixed
liquor each
feature
allows
behave
both
as
the
regulate in the solids a
in
tank
reactor.
reactor
a biological
This
to system as a and
SBR
tank
Each
in a
an
SBR
either
behavior
is
during fashion
expected CFS.
in
that
such
mixed moval
the than
greater
for Thus,
the
system
can or
plug-flow encouraged.
react
identical an
ideal
the
degree
period to the
steady-state of soluble
oper
completely Waste
proceeds spacial
be
to which
an
ideal plug flow CFS.
FIGURE
house. period.
3.
Existing
SBR
On
aeration
re
in time variations flow plug substrate
on
effect An the
soluble removal
multiple-tank
system.
Photo
overall
system. for meeting
be
implemented
by
rate to be either supply than the oxygen demand
reaction.
Simply
stated,
the
acceleration; Because of the
system
the
operation.
demonstrating rate on supply
oxygen
the other hand, an
Tank on left in aerated fill pretreating (Photo courtesy David A. Mitchell.)
and dis
System these from only but the also from
example
period
simulates
filled levels.
high concentration the fill period, organism during this push-pull is extremely arrangement rapid in SBR can and have considerable systems
an
system
varia
not
can
oxygen or less
is system are the brake.
organisms
in mixed accumulation liquor during fill and the time provided for react will determine the extent
the
to
off-line load
strategies
limitations
adjusting
and
changes, the aeration
rate of the biological
clarifier. ated
effluent
seasonal
comes
by provided Numerous control
distribu
on-
or
minimum
however, mechanistic
flexibility,
taken
can be partially
to different
simple control
to
be
short-term
Tanks
charged
(hypothetical).
and
either
tions.
0.50 0.75 1.00 FRACTION OF CYCLE TIME
can
Tanks
meet
the
the impact concentration
of of
organic carbon is shown for the fill in Figure 4. Three profiles for carbon are
shows
dairy waste.
one
given:
two
tanks
Tank
for
and
on right
the
accumulation
control
in idle
February
1979
237
Irvine and Busch is not This variety of substrate tensions. in most CFS. easily accomplished This ability to control substrate tension can
SUPPLY NO OXYGEN
a dramatic
have ous VARYING SUPPLY OXYGEN
organisms, stability.
ducted
at Notre
4.
Soluble
soluble remain
carbon
organic
ing as a function of fill time for different oxy gen supply rates (hypothetical). of
in the
substrate
soluble
the
for
system
aera
tion system left off, another for the oxygen demand fully satisfied, and the last for one of intermediate profiles possible by regu many In the latter rate of oxygen supply. the lating case, the oxygen demand is partially satisfied and C?D between A?B by providing energy the
for mixing
organisms
only,
and
completely
The continuation of satisfied between B?C. these profiles during the react period is shown in Figure 5. For all cases, oxygen is supplied in excess for the first half of the react period and supplied for mixing only during the sec ond
In
half. is
carbon
each
case, to
shown
be
the
soluble
organic removed
completely
In fact, the well before the end of the period. anoxic conditions during the second half of the react period seem to have little impact on carbon.
soluble ent mented
limitations, which
Thus, control subject
without
violating can be
strategies the organisms
efflu
imple to a wide
-1-: NOTE: OXYGEN EXCESS SUPPLIED DURING FIRSTHALFOF REACTONLY. AIROFF HALF. DURING SECOND
VARYING OXYGEN DURING FILL
an
causes
isms.
0.50 0.75 FRACTION OF REACTTIME
set
238
oxygen
supply
(hypothetical).
Journal WPCF,
Vol.
in
system
the
the
5,
anoxic
glycogen denitrification.
rates
2
in
and
in
the
organ
from Figure the
during
as
serving
the
second
in
donor
electron
as
such
carbon,
Exogenous not added.
was
methanol,
CONTROL STRATEGIES A the
of
discussion
an
of
presence
control
strategies
existing
system.
of an SBR system is beyond paper; tem
operating For
understood.
a
for
required
example, sized
is required
which
different
sys be
must
strategy as
"twice
a system
for
between
procedure the control
system
is markedly
necessary"
presumes The sizing
the scope of this
connection
the
however, size and
as
large
than
that sized.
"properly"
The following discussion presents the SBR in terms of control strategies that might be con sidered for both single-tank and multiple-tank The
systems.
additional
capabilities. As was
mentioned
is well
and
insight
in many
found
on-site
in
sys flows,
areas.
rural
limitations
Be
and the lack of
in wastewater
expertise
SBR
in small communities
industries
cause of monetary
to
is
the
into
a single-tank earlier, to noncontinuous
suited
those
especially
exercise
this
of
purpose
provide
treatment
in
rural communities, the treatment level desired must be achieved through time clock control. If the treatment level is more stringent than can be achieved through time clock control if a more
or
into more
become
more time
control
sophisticated
level sensors, dissolved
and
meters
system
operation.
As
also
(do) in
be
either
the
or the effluent requirements
severe,
simple
system
oxygen
can
turbidity
would have clock control
reasonably
51, No.
in glycogen
conditions
shown
supply)
that
it is not evident
system hydrograph
tration
different
that the
half of the react period were used for nitrogen removal in the Notre Dame studies, with the
tegrated
during
by
con
shown
to
similar
increase
is desired,
5. Soluble organic carbon removed initial concen the react period with
during fill
have
organisms
is
Although
probes,
FIGURE
filamentous
carbon
alone,
EXCESSOXYGEN DURING FIL^
0.25
Dame
overall
studies
4 (that is, varying oxygen
Figure
tem
NOOXYGEN DURING FILL
of filament and
of (and therefore the settling characteristics the solids) is readily controlled by anoxic con ditions during the fill period. The increase in
0.67 0.33 OFFILLTIME FRACTION FIGURE
of
control
nitrogen removal, In particular,
system extent
on
impact
an
additional
or
tank
to be added. Although alone could be used for treatment
objectives
in
a
Batch Reactors
Sequencing I.
TABLE
(no storm water).
system,
Single-tank
CASE I?NITRIFICATION Fill (hour) 21
2 hours;
Settle:
Notes:
4
6
5
8
7
9
?
XXXXXXX Mixing ? ?
?
Aeration
3
React
?
3 hours;
Draw:
?
?
?
10
?
12
11
?
?
13
?
XXXXXXXX
14
?
15
?
16
?
?
X
3 hours.
Idle:
CASE II?DENITRIFICATION Fill (hour) 12
?
Notes: a Zero
system with
or
a
system,
0
1.0 2.0
control
override
complex
SBR system
multiple-tank
level, do, and turbidity
time,
and
valves,
and pumps
off.
level a
regulating
?
control
turned on seem
systems
to have considerable utility in this regard. Other than the obvious constraint that all of the liquid must be kept within the tanks (that is, not on constraints tem
the must
ground be
operation.
anoxic
of
other tanks), for proper sys constraints these
conditions
removal
of
tiple-substrate
in
components
industrial
waste,
either
of
low
that
the limiting because Perhaps of continuous flow treatment,
even
are difficult respectively, level
component concentration.
remains
be
the
to describe.
Figures 2 and 4, hydraulic and substrate
provided
descriptions.
In
an
?
18
X
1.0 3.0
0.5
19
20 ?
XX ? ?
XX?
0.5
0
0.5
X
0.5
attempt
to
present
I and
Tables
perspective,
II
characteristics
operating
the cases described
Case
I:
Single-Tank
3.0
of
sum two treat
system.
are storm
(no
System
No flow 10 hours per day Nitrification plus carbon removal desired Time clock control only II:
Case
System
Single-Tank
(no
storm
removal
de
water) No flow 10 hours per day Denitrification
carbon
plus
sired
Time clock and do control Case
III: Three-Tank Continuous flow Carbon
clock,
rural
operation; a large
desired and
do,
level
I and II might
Cases small
System
removal
Time
sufficient
use overwhelming in wastewater technology the most SBR systems simple of
?
17
water)
a mul
time must be provided during the react period or, in the case of an inhibiting component, fill must be operated such that the (if possible) concentration
?
16
15
a separate each with systems, single-tank ment a multiple-tank and objective,
the
during
fill period). For nitrification, the do must be For denitrification, the greater than 1 mg/1. For the po must be less than 0.5 mg/1. sequential
14
XX
another yet marize the
listed below. For all desired levels of treatment, the control policy that provides for good settling organisms must be implemented example,
?
0
1.0 0.5
are
(for
13
X ?
the
around established
Examples
X ?
12
Specifically,
compressors,
that could be
Microprocessor
X
11
no Idle. 3 hours; limit of the probe.
The most
involve
adjustable
mixers,
Draw: detection
is desirable.
control
1.5 0
1.0
1 hour; below
Settle:
would
system
?
X?
10
9
XXX?
0.5
indicates
multiple-tank
?
8
7
XXX?
0
0a
(mg/1)
6
5
?
?
XX ?
Mixing Aeration DO
4
3
React
control
represent
a
either
or a community food-processing a small Case III, either industry
town.
In
all
the
cases,
situations
or are
hypothetical and the "correct" control strategy would depend on actual field conditions. The control
policies
and
realistic treatment As system
can
presented,
potentially
problems. seen be
operated
from for
are
however,
useful Table
I, a
nitrification
February
for
quite
specific
single-tank and carbon
1979
239
O52 -i
TABLE
IL
Three-tank
system. Hours
n
< o
2 o
Tankl Mixing Aeration DO Tank
X
?
0
I
2
?
X
S
X
0.5
0.5
0.5
I
I
D
R = S = D = I = R =
React Settle Draw Idle React
R
X
X
0.5
3.0
I
I
F
F
F
D
0.5
1.0
D
I
0.5 I
0
X
0
X 0.5
?
X 0.5
?
X 0.5
X 0.5
I
2
?
R
S
D
?
XX 1.0
2.0
D
I
XXX 0.5
Tank
0.5
2.0 ?
End Fill
Fill
Fill
R
4.0
?
? End
End Tank
?
R
F
X
0.5
0
F
17
X
XXX
X
16
15
X ?
0.5
1
S
R
0.5
Fill
1
For Tank
14
?
?
Tank
13
X
0
? End
of Fill
R
2.0
R
I
12
I
I
D
X
X
Mixing Aeration DO
F = Fill
D
Begin
11
?
X ?
D
3
R
X
Mixing Aeration DO Tank
R
From
10
9
3
Tank
1
Ta
Batch
Sequencing
?gT
Reactors
^j*?%
*^*%?l|
6.
FIGURE
Future
convert
would
of
removal
is easily
controlled
by
to maintain
aeration
Proposed
operation
with
mix
of fill and do
the
concen
that
No
day. waste
raw
the
is made
attempt flow,
to and
however,
16th
is,
aeration
hour), are
organisms After the
18th
3
is
closed,
hours,
presumably
flow begins
be provided may times actual for
The to be
have time or
clock
for
wastewater
treatment flows
until
Either
mixing
idle, how during each would period
and
equipment
valve
Additional
agitation,
The start-up. during to activate be set either
must
mixing
The motorized a pump. be made
again.
determined simply
deactivate
is turned
valve
without
or
ever.
the
hours.
and kept there for 3 hours
the waste aeration
2
for
the motorized After period. remains the idle for system
draw
the
and
down
settle
a motorized
hour,
to the open position during valve
is shut to
allowed
regulate time the
for 2 addi time (that
clock control will continue aeration tional hours.. At this predetermined
could be
valves.
replaced with
to have would provisions storm and of combined
during
the
draw
time
clock policy
control. such
In as
such a 2-hour
a
case, mixing
a
to
simple period
followed by a 3-hour aeration period could be repeated throughout the fill and react periods, the only criteria being that aeration be on for at least the final hour of the react period, both
the
(Photo
detachment
of
gas
nitrogen
to the floe
aerobic
reasonably
The
conditions
in
time
do de the probe a prede of mixing do concentration
from
signal
aeration
termined
favor
after
the
1 mg/1 and similarly the do concentration
after
any
adhered
have
may
provide
simple. activates
reaches
study
modification.
The control policy the settle period. is quite in Table II for denitrification
during shown
do
is 19 hours
control
aeration
activates falls
de
the
below
time
The preset
limit of the probe.
tectable for
activated
demonstration
which
bubbles
in Table
in
As
II.
dicated,
the final hour of the react period
aerobic.
Control
of
settle,
In
to
order
in single-tank
indicate
system
is are
idle
and
draw,
time clock just as described I.
I in Table
for Case
additional
differences the
operation,
time
total
for fill and react for Case II is 4 hours longer, which suggests the need for extra time for the to
system
extra
do
Note
"work."
that
also
although no time is shown for idle, idle time could be provided as necessary by changing the
times
some
for
The tank
final system flow.
case
the
of
could
microprocessor scheme.
able
period.
The denitrification system described by Case II in Table I could also be operated using control
ensure
to
conventional
USEPA minimal
and
tration above 1 mg/1 for the remaining 7 hours of fill. Although fill is shown to terminate at the end of the 14th hour, the actual time for fill would depend on the system hydrograph for
shows
Ind.
providing
the first 7 hours
ing only during sufficient
for Culver,
to SBR facility existing Town Culver Ind.) Board,
courtesy
Photo
system.
multiple-tank
( 1 200 mVd)
sludge plant
be
other
A periods. this control
is one
discussed
a receiving In this case,
in
used
the
a
three
but
vari
of
continuous system
was
de
fill time of 2 hours. signed for a minimum Flow is directed from one tank to another by a
volume liquid As ized valve.
for
a given
tank
sensor
that
a result,
the
depends
on
operates actual the
flow
a motor time
for
rate.
fill In
I, Tank 1 is shown to be in the fill phase during the first 3 hours, while Tank 2 is in the idle phase and Tank 3 is in the draw and idle
Table
February
1979
241
Irvine
and
Busch
Tank 1 is not refilled until the 11th Between the third and tenth hour, is in the fill phase for 2 hours and Tank hours. The control policy for do dur fill phase is similar to that described
phases. hour. Tank 2 3 for 5 ing the
for
previously mixing
in favor
aeration
of
concentration
the
settle
period. the react
throughout
centration
exceeds
operations time clock.
after
and
for
depends
idle
1 mg/1
system could also be designed
with
a constant
for fill
The
described examples in nature. illustrative While of
the
systems
7.
FIGURE T.
scale reactor
be
ferroxidans
The
time
flow
rates.
to operate are
the
attached
of SBR
(5 000 magnification
(Photo
).
Journal WPCF,
Vol.
51, No.
2
the
to
control not
While
cases,
far
in
described
can
turbidity
quite more
be
to
used
the time for settle because after the sludge blanket level passes some preset depth
define the As
can
valve
discharge a final
note,
opened. be
may
wasting
on a periodic and
systems
single-tank
be
sludge
ac
in the
basis
in
automatically
system multiple-tank by a preset to remove pump
the
a discharge of the liquid
activating fraction
volume during the last 15 minutes of the react for each tank during each cycle. For
period
enthusiasts, sludge-age be used fraction may age of the system.
the
reciprocal the calculate
to
of
this
sludge
SUMMARY Because
of
the
this
of
brevity
in
presented
courtesy
in SBR totally other
John
during
the in
papers
L. Theis
and the
information this
of acid-mine shows of
research cannot
overview
either
Charlesworth) settle period
of Thomas
of
technology
this
to treatment
technology (by
the
nature
dynamic paper,
to cover
presume
photomicrograph to kaolinite particles
Carter.)
242
simply
description at first, the
Application
situations.
complex of any
and development
react.
and/or above
Electron
The
strictly are periods
confusing
Research.
wastewaters.
drainage bacteria D.
may
of
are
respectively. the volumetric
The
time
The
provided do con
for 1 hour.
period draw and
settle
hours, on
the
react
the
The 2
1 hour
is until
simple
are
followed
is, constraints) can be used
(that and
complished manually
react
the
the beginning
Aeration period
concen
for 1 hour. during
to determine
is used
period
1
of
do
the
until
control
case,
is not deacti
and
0.5 mg/1
tration falls below do
this
a minimum
for
the fill phase
hour during vated
on
remains
only
In
denitrification.
rules
bench
and Bruce
issue
or
Batch Reactors
Sequencing most
the
tional
recent
results.
the
of
mary purpose this presentation
overview.
concludes
sage: SBR systems, because nature,
capabilities tems alone the
the
expand
possible are and
continuous
a
of their periodic
treatment
treatment flow
sys to
alternative in use
systems
result, mes
final
of spectrum from continuous a
flow
the pri
As one
with
addi
of
Inclusion
tend to obscure
topics would
tions were largely responsible for the insights gained into SBR systems. All the materials incorporated in this work were developed with the financial support of the National Science Foundation Grant ENV titled "Application of Sequencing 76-10381, Batch Reactors for Treatment of Municipal and Industrial
Wastewaters."
cover of this issue of the Journal
The
now.
cludes
ACKNOWLEDGMENTS Credits.
The were:
Committee
Ind., Water
members P.
of
the Advisory Fort
Brunner,
Wayne,
Pollution Control Plant; L. Rague,
South Wastewater Treatment Bend, Ind., U. S. Environmental Plant; J. L. Witherow, Protection R. Roper and R. S. Coma, Agency; B. & Associates; W. B. Davis, Henry Steeg Bovay ence
Inc.;
Engineers Inc. (now
private
J. Mancini, consultant
Instrument
Riddell, Greeley McHarg, Amoco International dard
Inc.;
Brands,
Systems
Inc.;
Hydrosci and Adjunct
M.
D.
R.
and Hansen Engineers; W. Chemical; T. Sherman, CPC and W.
C.
Neumann,
Stan
Inc.
The research was conducted by James E. Alleman and Robert W. Dennis at the Uni versity
of Notre
Dame,
Ind.,
whose
disserta
electron
scanning
in
microscopy
of one sample taken from a photographs bench-scale SBR system. 1 (left) Number shows collapsed bodies of stalked ciliated Vorticella sp. clustered with a floe (1600 mag Number 2 shows nification). (top right) of
organisms
filamentous-appearing
C. Bowers, Professor, Manhattan College); Metcalf & Eddy Inc.; H. S. Nye, Environ mental
three
unknown
Number 3 (8000 magnification). identity (bottom) shows a diverse microbial population typically associated with mixed cultures (1600 The photomicrographs are magnification). courtesy of John Charlesworth, Biology, Uni of
versity
Alleman, Maryland,
Notre
Dame,
Ind.,
Civil
Engineering, College Park.
Authors.
Robert
L.
Irvine
and
E.
James
of
University is Associate
Pro
of Civil Engineering, Uni fessor, Department versity of Notre Dame, Ind. Arthur W. Busch is an
environmental
Dallas,
Tex.,
Scientist, Texas
State
and
Institute University,
consultant
engineering
Senior
Adjunct
of Applied
in
Research
Sciences, North
Dent?n.
February
1979
243
