&EPA
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati OH 45268
Technology Transfer
EPA/625/8-86/011
Summary Report
Sequencing Batch
Reactors
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1 986
This report was developed by the
Center for Environmental Research
Information, Cincinnati, OH 45268
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Foreword The United States Environmental
Protection Agency (EPA) has a
responsibility to identify and
develop potential innovative
technologies for reducing and/or
mitigating adverse effects on the
ecosystem of the U.S. In order to
be most effective, these efforts
must be documented in a manner
that facilitates the transfer of the
developed technologies to the
public for consideration and use.
This report summarizes one of
these potential innovative
technologies, Sequencing Batch
Reactors (SBR) for municipal and
industrial wastewater treatment.
Contained in the report are pro-
descriptions, performance
evaluations, and economic com-
parisons with conventional tech-
nologies. The report is not an
engineering manual. Rather, it is a
generalized report written for the
public and including references
for those interested in pursuing
details of engineering,
-------
of
1, Introduction , - , , , , , , , , , 1
2. Process , . . . . . 4
3, Performance ,,,,,, , , , , 9
4, Design ,,,,.,.,, ,,....,,,.,,. 13
5, Currently Operating Plants 1 5
8. Economics ....,..,.,...,,,... 16
Tables
1. Comparison of Batch and Continuous Processes 3
2, Plants Evaluation Summary 10
3, Cost Estimates for SBR for Four Average Daily Flow Rates . . , , , 1 ?
4, Operation Maintenance Cost Estimates for the SBR
for Four Average Daily Flow Rates 18
5. Cost Comparison —379 m3/d Facility 19
6. Cost Comparison— 1893 m3/d Facility 20
1, Cost Comparison-3785 m3/d Facility 21
8, Cost Comparison—18,925 m3/d Facility 22
Figures
1. Typical SBR Operation for One Cycle , , 6
2. Suggested Operating Strategies for Different
Water Quality Objectives , 12
References
1, Arora, Madan L. and Umphres, Peggy B,, "Technical Evaluation of
Sequencing Reactors" for U.S. Environmental Protection
Agency, Cincinnati, OH, September 1984,
2, Irvine, L. "Technology Assessment of Sequencing Batch
Reactors," U.S. EPA, Cincinnati, OH, November 1983.
Cover Photo:
Provided by Austgen
The 0.5 ICEAS in the right fore-
ground has the same capacity as the
older technology plant in the background,
but produces a 10 BOD$ and 10 SS
denitrified effluent.
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1,0
1.1 A Sequencing Batch Reac-
tor (SBR) is a ftli-and-draw acti-
vated sludge treatment system.
As such, SBRs are capable of
handling all wastewaters com-
monly treated by conventional ac-
tivated sludge plants. Municipal
and industrial wastewaters have
both been successfully treated in
SBR systems.
The unit processes involved in
the SBR and conventional acti-
vated sludge systems are iden-
tical. Aeration and sedimentation/
clarification are carried out in
both systems. However, there is
one important difference. In con-
ventional plants, the processes
are carried out simultaneously in
separate tanks, whereas in SBR
operation the processes are car-
ried out sequentially in the same
tank.
The Intermittent Cycle Extended
Aeration System {ICEAS} repre-
sents a modified version of SBR.
Whereas the inflow and outflow
are intermittent in SBR (at the
beginning and end of the treat-
ment cycle), the inflow is con-
tinuous in ICEAS. An SBR system
must comprise either a storage
tank and an SBR tank or a
minimum of two SBR tanks to ac-
commodate continuous inflow, A
baffle wall may be installed in the
ICEAS treatment tank, to buffer
this continuous inflow. Otherwise
the design configurations of the
SBR and ICEAS systems are very
similar.
1,2 The use of fill-and-draw
(batch) processes for treating
wastewater is not a recent
development. Fill-and-draw
systems similar to SBRs have
been in development and use
since the turn of the century.
Most sewage treatment studies
between 1884 and 1912 used
either chemical precipitation,
coarse media filters, or a com-
bination of the two in fill-and-
draw tanks. Aeration was only in-
frequently employed. In 1914 the
value of aeration was demon-
strated, and between then and
1920 several full-scale fill-and-
draw systems were operated.
After 1920, however, the empha-
sis moved to continuous flow
"conventional" systems, and
most of the fill-and-draw systems
then in operation were converted
to the conventional configuration.
Reasons for moving away from
the batch process included the
high energy that must be dissi-
pated during discharge of the
treated effluent, greater demand
for operator attention, and clog-
ging of air diffusers because of
the periodic settlement of sludge.
In the late 1950s and early
1960s interest was revived in the
fill-and-draw systems with the de-
velopment of the new technology
and equipment. Improvements in
aeration devices and control
systems have allowed the
development of fill-and-draw
systems to their present level of
efficiency, which now enables
SBR technology to successfully
compete with the conventional
systems.
1.3 As currently in use, all SBR
systems have five steps in com-
mon, which are out in se-
quence as follows;
» FILL
» REACT (Aeration)
* SETTLE (Sedimentation/
Clarification}
» DRAW (Decant)
» IDLE (sludge wasting)
IDLE is necessary in a multiple
tank configuration where one
tank is not yet full (during periods
of low flow) and another has
completed its cycle and is waiting
to receive raw wastewater.
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1.4 In comparison with conven-
tional continuous flow systems,
the outstanding feature of SBR
technology is its flexibility. Table
1 compares various features of
conventional and SBR systems.
The advantages of the SBR over
the conventional system can be
summarized as follows:
« An SBR tank serves as an
equalizing basin during FILL,
and therefore can tolerate
greater flows and/or
shock loads of Biochemical
Oxygen Demand (BOD) with-
out degradation of effluent
quality,
• Since the discharge of effluent
is periodic, it is possible,
within limits, to hold effluent
until it meets specified re-
quirements.
* During early design life, when
flow is significantly smaller
than design capacity, liquid
level sensors can be set at a
lower level, thus using a
fraction of the SBR tank
capacity, in this way, the length
of treatment cycles can be kept
constant without unnecessarily
wasting power by
overoperation.
* Mixed iiquor solids cannot be
washed out by hydraulic
surges, since they can be held
in the tank as long as
necessary,
» No return activated sludge
(RAS) pumping is required,
since the mixed liquor is
always in the reactor.
» Solid-liquid separation occurs
under nearly ideal quiescent
conditions. Short circuiting is
non-existent during SETTLE.
Further, reactor
achieves small surface settling
rates, resulting in settling of
even floe particles that
may be washed out in con-
tinuous flow systems,
« Filamentous growth can be
easily controlled by varying the
strategies during
FILL.
« An SBR can be operated to
achieve nitrification,
denitrification, or phosphorus
removal without chemical ad-
dition.
• It has been reported that the
RNA content of the
microorganisms in the SBR is
three to four times greater
than would be expected from
a conventional continuous
flow system. Since the growth
rate of microorganisms is
known to depend on the RNA
content of the cells, the
presence of more of this in-
tracellular machinery allows
the SBR culture to process a
greater quantity of substrate at
a rate greater than that possi-
ble in a conventional con-
tinuous flow system.
Disadvantages of the SBR include
the increasing sophistication, as
systems get larger, of the timing
units and level sensors used to
control the process sequences,
and the difficulties involved in
controlling the DRAW or decant
phase so as to minimize the dis-
charge of floating or settled
sludge. Also, concerns remain
about plugging of aeration
devices during settle, draw, and
idle periods,
New SBR replaces old treatment with greater capacity, better
treatment and smaller requirements.
-------
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Continuous ICEAS
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ariations of organic loading are possibl-
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ires above facilities.
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by changing operation;
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ICEAS.
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-------
2,0
2.1 A treatment plant utilizing
the SBR concept has only one
type of process unit, the batch
reactor tank. It is possible,
even preferable in many cases, to
link several identical reactor
vessels in a multiple tank config-
uration, to limit the size of in-
dividual units and increase flex-
ibility. There are no units dedicat-
ed to a single process, such as
equalizing basins, aeration cham-
bers, and clarifiers, as in contin-
uous flow systems.
In its simplest form, a batch reac-
tor consists of a single tank
equipped with an inlet for raw
wastewater; air diffusers, with
associated compressors pip-
ing for aeration; a sludge draw-
off mechanism at the bottom to
waste sludge; a decant mechan-
ism to remove the supernatant
after settling; and a control
mechanism to time and sequence
the processes. Various suppliers
of SBR systems include different
modifications to the basic sys-
tem, such as the installation of a
baffle near the inlet to provide a
prereact chamber separated from
the aerated portion of the basin.
Many decant structures are
marketed with features designed
to limit the discharge of floating
solids and settled sludge. Air dif-
fuser design and construction
also varies among suppliers, but
many SBRs jet aerators or
mechanical aeration to ac-
complish aeration and/or mixing
with a single device.
The heart of the SBR system is
the control unit and the automatic
switches and valves that se-
quence and time the different
operations. The advent of reliable
microprocessors at reasonable
cost, used in conjunction with
modern limit/level switches and
automatic valves, has been a ma-
jor factor in the recent develop-
ment of SBR technology. The
ability to control the processes in
time rather than space is crucial
to the SBR concept.
: * * » * J, •
Flows and processes are controlled via computer (center of pic-
ture). Microcomputer (to leftj tracks allows operator Input
review.
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Hydraulics works control flows are
by compute?.
2.2 In SBR operations, the cycle
processes FILL, REACT, SETTLE,
DRAW, and IDLE are controlled
by time to achieve the objectives
of the operation. Each process is
associated with particular reactor
conditions (turbulent/quiescent,
aerobic/anaerobic} that promote
selected changes in the chemical
and physical nature of the
wastewater. Th*»se changes
ultimately to a fully treated ef-
fluent. Figure 1 is a schematic of
one cycle of a typical SBR Of5era-
tion, showing typical percentages
of the total time (in this case ap-
proximately 8 hours) spent in
each process,
FILL. The purpose of the FILL
operation is to substrate (raw
wasfewater or primary effluent!
to the reactor, The addition of
substrate can be controlled eithet
by limit switches to a set volume
or by timer to a set time period. If
controlled by volume, the FILL
process typically allows the liquid
level in the reactor to rise from
25 percent of capacity (at the
end of IDLE) to 100 percent. If
controlled by time, the FILL pro-
normally approximately
25 percent of the full cycle time.
These percentages are represen-
tative proportions. As with each
of the five processes, the time
and volume limits of the FILL pro-
cess are determined by actual
operational constraints and per-
formance requirements, In reality,
the initial volume
-------
1.
Typical SBR Operation for One Cycle
OF:
WtAX
VOLUME
25
to
100
CYCLE
TIME
25
INFLUENT
FILL
^^JZ&^JS^&t,^^
100
35
AIR
ON/OFF
ADD
SUBSTRATE
I- T-I
5^^*^^^5oS^^
, Of! „ oO'O aQ Qd n «°
W0^fo^o°0%
>^0^^| ^ n S^O o*°i
SOiiJaJL-LxiJlSjQ^acJ
REACTION
TIME
AIR
ON/CYCLE
100
20
AIR
OFF
CLARIFY
100
to
35
15
AIR
OFF
REMOVE
EFFLUENT
35
to
25
AIR
ON/'OFF
WASTE
"SLUDGE
Figure from Irvine, Technology Assessment of Sequencing Batch Reactors, p. 3,
A modification of the pure SBR
system with only one reactor
allows the continuous feed of
raw wastewater to the SBR
throughout the cycle. Baffles are
used to minimize short-circuiting
and turbulence during critical
phases of the cycle such as SET-
TLE and DRAW,
REACT. The purpose of REACT is
to complete the reactions that
were initiated during FILL. As in
FILL, performance considerations
might require alternating periods
of high and low DO concentra-
tions. The length of the REACT
phase can be controlled by a pre-
set time limit or, in a multipletank
system, by liquid level controls.
In the second case, the REACT
phase is ended when the liquid
level in the tank undergoing FILL
reaches a predetermined level.
Typically, REACT up 35
percent of the total cycle time,
but performance demands might
require substantial deviation from
this average.
-------
The purpose of SETTi E
is to allow solids separation to
occur, providing a clarified supei-
nalant !o be discharged as ef
fluent. In an S8R. this process is
nonnally much morr» efficient
than in d contmous flow system,
because in the SE1TLE mode the
reartor contents are completely
quioscent. The SETTLE process is
t onti oiled by time and is usually
fixed between 1 '2 and 1 hour so
that the sludge blanket terrains
hHow the wilhtJiowdl mechanism
during llw* next phase, DRAW,
and dofis not nsf- (because1 of qat
lormatieml before DRAW is
c ompiftpd
The purpose of DRAW is
to remove clarified, treated water
from the reactor. Many types of
decant mechanisms arc in current
use, with the most popular being
floating or adjustable weirs, The
decanting rate can be controlled
by automatic valves in a gravity
system or by pumping, The time
dedicated to DRAW can range
from 5 percent to 30 percent of
the total cycle time (IB minutes
to 2 hours), 45 minutes being a
typical DRAW period.
IDLE, The purpose of IDLE in a
multi-tank system is to provide
time for ono reactor to complete
its fill cycle before switching to
another unit, IDLE
-------
Many modifications can be made
to the basin processes described
above, to overcome facility con-
straints or to enhance perfor-
mance. Examples of these mod-
ifications (after suitable physical
changes such as additional baf-
fles) include the overlapping of
FILL and DRAW under controlled
conditions, and the provision of
mixing and/or aeration during a
period of FILL,
Sludge wasting is another impor-
tant step in the SBR operation
that greatly affects performance,
It is not included as one of the
five basin processes because
there is no set time period within
the cycle dedicated to wasting.
The amount and frequency of
sludge wasting is determined by
performance requirements, as
with a conventional continuous
flow system. In an SBR opera-
tion, sludge wasting usually oc-
curs during the SETTLE or IDLE
phases, A unique feature of the
SBR system is that there is no
need for a return activated sludge
(RAS) system. Since the aeration
and settling occur in the same
chamber, no sludge is lost in the
REACT phase and none has to be
returned from clarifier to maintain
the sludge content in the aeration
chamber. This eliminates the
need for the hardware and con-
trols associated with a conven-
tional RAS system. The sludge
volume and, thus, sludge age in
the reactor of an SBR system is
controlled by sludge wasting
only.
Slydge treatment following removal from SBR
Primary digester-continyoys Primary digester—idle tank
tank
Siudge press—sludge comes from idle tank, is processed and then transported
and applied to local farmlands.
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3.0
3.1 Biochemical Oxygen De-
mand (BOD) removal is often
used as a traditional measure-
ment of the effectiveness of
municipal wastewater treatment,
BOD measures the amount of ox-
ygen necessary for removal of
the wastewater con-
taminants by the action of
microbiologic organisms. SBR
systems consistently achieve
more than 90 percent BOD
removal in full-scale studies at ex-
isting installations. The removal
of at 90 percent is also
typical for continuous flow
systems currently in use.
Table 2 shows the BOD removal
efficiencies of six plants in opera-
tion in Canada, Australia, and the
U.S. in 1984. As shown in the
table, all six plants achieved or
surpassed their target effluent
BOD,
An important advantage of the
SBR system is the control the
operator can maintain over micro-
organism selection. Within a com-
plete treatment cycle, the
microorganism selection pres-
sures are highly variable and
severe. These pressures include
oxygen availability, which ranges
from anaerobic through anoxic to
highOG conditions, and substrate
availability, which from
famine to feast conditions, While
certain of these selection pres-
sures can occur in some conven-
tional continuous flow systems,
the SBR system provides the
ability to easily select and extend
or limit preferred conditions
through time, allowing the
preferential growth of desirable
microorganisms.
Two observations have
documented that illustrate the
beneficial effects of this control
ability. The first is that the RNA
content of microorganisms pro-
duced by the SBR system is
much greater than that found in
microorganisms produced in con-
ventional continuous flow sys-
tems. The growth rate of micro-
organisms has directly link-
ed to the RNA content of the
cells. This means that in an SBR
system, more microorganisms are
capable of processing a greater
quantity of substrate at a
rate than in a conventional
system. Secondly, it has been
reported that a properly selected
aeration strategy can result in the
minimizing of the growth of
filamentous microorganisms, as is
true in continuous flow systems,
These microorganisms, whose
presence in quantity leads to pro-
blems with sludge buiking and
foaming, are undesirable in the
activated sludge floe in excessive
numbers, and their control is an
to system performance,
-------
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-------
3 2 Suspended solids removal is
a second traditional measure of
wd&tewater treatment plant pcr-
fpimance Suspended solids
removal has also been proven to
be effective in S8R systems. As
shown in Table 2, removal effi-
ciencies of greater than 90 per-
cent ate characteristic of SBR
systems as well as conventional
continuous flow systems, in adrii
tion, the SBR system has two
major advantages over the ion-
tmuous systems Fsrt>t, suspended
solids removdl occurs durinti the
SETTLE phas>e of the opeiaftonal
cycle. As a physical ialh.pt than ?
chemical process, the solids st:p
oration depends on floe M/e and
density as well as on turbulence
and currenrs within the settling
tank "1 he more quiescent the
tank the better the solids sepuM
tion. One of the advantages of
the SBR system is thai by stop
ping the flow into and out ol the
tank, ao well as by stopping the
aeration and mixing, settling
take?-, place under almost perfect
'V quiescent conditions Thi^
yields a faster and more defmeci
solids separation Conventional
continuous flow systems, by
definition cannot stop the inflow
and outflow of the rlartfiet unit
Fhtfc settling must take place in
conditions where water runents
and possible snort-ciicutttnp ate
tvcuirtny
Hte second advantage to the
solids separation firoccss m the
SBR system is the flexibility of
forded to oltei the time dedicated
to the pioeess. An SBR unit can
easily be adjusted to give more
time to the SETTLE phast if it is
necessary to achieve sufficient
solids separation, Duitng high
flow conditions*, the SETTLE time
can be reduced n> the niitiimmn
necessary to achieve solids
f-eparation, cutting down or» the
overall cycle time and treatinq
mote flov\ Decantinq can also be
initialed durinq SFTTLE, if
necessary, to futthcr reduce the
overall tinv requirements Con
VBivfio'Vil continuoiis flow
systems evhibit none of thio
flexibility.
3,3 Nitrogen removal can be
achieved in the SBR system
without additional equipment or
chemicals. Nitrogen enters the
system in the raw wastewates in
the rorm ol organic nitrogen and
ammonia (NH4), it is removed
Irom the system in the form of
nitrogen gas (N2). The process by
which ammonia nitrogen is con
vertod to nitrogen gas involves
three steps, First is the conver-
sion (nitrification) of ammonia
nitrogen to nitiite (NO,), Second
is the conversion of nitrite to
nitrate (N0a). Third is the conver-
sion {denitrif(cation) of nitrate
nitrogen to nitrogen gas. All of
these steps ate accomplished by
microbiological action. However,
the differing nature of the reac-
tions, oxidizing or reducing.
demands different microorgan-
isms and reactor conditions.
Nitrification, the process of con-
vertmy ammonia nitrogen through
nitrite-nitrogen to nitrate nitrogen
(steps 1 and 2), can only occur
under conditions of adequate DO,
in the SBR system, nitiification
takes place during REACT and
any periods ot aeiated FILL, if the
nitrification process is to DP effec-
tive, ihe combined aeration time
during FILL and REACT must be
sufficiently long and the DO suffi-
ciently high iyreaior than 0.5
g/nr'*) to allow for both the
development of nitiifiers {those
microbes performing the nitrifica-
tion) in the system and the corn
plotion of ammonia-nitrogen
oxidation,
DenitnfuMtion (step 3), the pu>-
cess of towelling nittate-
iittrttyt'n lo nitrogen gas, only oc
t,utb in the absence of DO in an
SBR system, denitnfication can
occur dunny ihe unaerated pot
nun ol Fll L und during the loiter
stdQPS of SETTLE, DRAW, and
IDLfc after the DC) content has
dropped off. As with nitrification,
these conditions must lost suffi
r,«.»nt)y long to allow thr> desired
nttiotjpn reduction to tdke place
Nitrogen removal in an SBR sys-
tem can be considerably greater
in efficiency than conventional
continuous flow systems. The ad
vantage of Ine SBR system is
thai the conditions necessary to
achieve nitrogen removal can be
created by simple changes to the
plant opeiation fmodifications to
periodicity and duration of aera
tion) rather than by major
modification of she physical plant,
Ftguie 2 shows suggested operat-
ing strategies for achieving dif-
ferent water quality objectives
through SBR operations
3,4 Phosphorus removal by
microbiological methods in SBR
systems has docu-
mented- fhe addition to the teac-
tor of a chomicdl coagulant that
precipitates the phosphorus into
the sludge is a common phos-
phorus removal process appli-
cable to both conventional con-
tinuous flow and SBR systems.
The microbiological removal of
phosphorus litst requires an
anaerobic period (the absence of
dissoivod oxygen anil oxidized
nitrogen) dmmg which substtate
daw waste) is present. This
penod should be followed by an
nerobir period (high DO) that pro-
motes the uptake of excess phos-
phoius by the siudge mass Ex-
cess sludye should he removed
from the reactor in suitable quan
tities befote the onset ot the next
anaerobic period. In terms of SBR
operation anaerobic conditions
mur.t be available during FILL, and
sufficient aeration must be pro-
vided during REACT to achieve
phosphorus uptake by the bio
mass. The flexibility of the SBR
system is again shown by its
ability w achieve these conditions
with simple operational modifica-
tions, Figure j> shows a loi.om-
rnenried stiatdjjy for accomplish
inq both nitiogen and phosphorus
removal in an SBR s\ stein.
II
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4.0
4,1 Design of municipal SBR
systems to handle industrial
wastewater would generally re-
quire an extensive treatability
study, as would conventional
continuous flow systems. On the
other hand, system design for
typical domestic wastewater is
relatively simple, centering
around the selection of the proper
tank sizes, the inlet configuration,
the aeration system, and the con-
trol mechanism. With knowledge
of such factors as average daily
wastewater flow, peak daily flow,
average influent BOD, average in-
fluent suspended solids, average
influent ammonia nitrogen, and
effluent requirements, an initial
design for an SBR system can be
easily developed,
4.2 One design ap-
proach for a domestic SBR
system includes the following
steps:
1, Decide if primary treatment is
needed. Primary treatment is
unnecessary in most SBR
systems, especially if the
design sludge age or sludge
retention time JSRT) is high
(more than 20 days). A high
SRT system will also ac-
complish some sludge diges-
tion aerobically in the reactor.
The treatment selected must,
of course, comply with ap-
plicable Federal and local
discharge regulations and
codes.
2. Select the desired
food/microorganism (F/M)
ratio. The selection of the
design F/M ratio should be
based on considerations such
as nitrification requirements
and desired SRT. From a given
influent BOD, F can be
calculated in pounds of 80D/-
day, and application of the
F/M ratio yields the
design M or sludge mass,
F = mg/l x 8.33 Ib/gai
X flow J106ga!/dayl
M = F ~ F/M ratio
3, Select a value of Mixed Liquor
Suspended Solids (MLSS) con-
centration in the reactor at the
end of DRAW. This is slightly
different from designing a con-
ventional continuous flow
system. The MLSS concentra-
tion in an SBR cor-
responds to a particular period
in the SBR operating cycle,
since the concentration
changes throughout the cycle.
In an SBR, the MLSS concen-
tration is lowest at the of
FILL and highest at the end of
DRAW. With most SBR sys-
tems, the MLSS concentration
at the end of DRAW should be
higher than the corresponding
value used in the design of a
conventional continuous flow
system, because the MLSS
concentration in the SBR
system at the end of DRAW
represents a completely settled
mixed liquor, similar to that in
a conventional clarifier
underflow. The design mixed
liquor volume can then be
calculated from the
MLSS concentration.
Volume = M x {10* gal/day)/
{8.33 x MLSS concentration)
4, Select the number of SBR
tanks. The number selected
will depend on the mixed li-
quor volume determined in
step 3, as well as on con-
siderations of area, unit
availability, projected
maintenance, and operational
flexibility. There are no basic
rules of judgment in this
regard, except that in most
cases it is desirable to provide
at two tanks.
13
-------
5, Select a cvcle length
pnsed of FILL, REACT SET
TIE, DRAW, and IDLfc, for
each "hatth ' treatment The
total time for a cvcle will bt
the surr of the timt *» allows]
for the cyrli. phase;.
T
ts + 1d
Thy time, for FILL tt, can be
calculated from the peak d<»ily
flow divided by the number of
tanks The combined time 1o«
SETTLE, t, and the time for
DRAW tu con be estimate.) to
be let's ihdii 3 houis tht, time
for REAC I , t should tV rfeies
mined fiorn kinetit studies bin
for domestic wastewjti i the
ranne «f time for R! ACT wdl
ae'V^Mllv be bf twton 1 2 and
2 hoiiis 1 hi- 1 itit I titiv fact 01
for )DIF t , is SP|
tir ^ ivrtlt d so thai the u'Oti/f
pait 01 tpe i \ Jc »ti,tnn 3 Fcifor nuiis (^
6. C tilf- iir»tP thf volume of liquid
pu rti!">k IK i
ptt ritcant .v ti -
Aveiaqe F iowr yul- r
Volume per tank per decant =
V(:i/no, of tanks
7 Calculate ihe tank size
total volume required per tank
is HIP sum of thp volume of
mixed 1 quor per tank at the
end of DRAW and the volume
of liquid riectinttd per tank per
Fhe iinjt dime nsions of tht
tanks f d» be developed by
select), KJ j !edsondhl«j tank
depth in inosi ^ase& ,1 cVplt1
of 1 b tei f » r less is practii t>l
trorn the ssdiidfjoint ot oxycitn
trrnsftr cffi( tenrv Also
ailuwanct rnucl br .rwde foi
f»ppiO(tn3lf htcbodrd usually
J 10 4 ftet
Voiunu of uiiik -
ikju' i -t Volum*1
Are 3 of tanl- _ Volnme ef t jfik
- F mi» fl^ijtoi
Ss/c iho ti>'i,iiioM co iipni* nt
Fins F done in tlv s> 'c^ m^ri
nt • d . in a < onvontiontil v t r
i nuriir, fio\v sy-l°n ex* ept
that i inc n ifi(i aerut- JH enuip
nvil ruii1- foi (>nly a ocMTitin of
ttlP « pi rallllLl ( V< I" >rf el'1"1 S'jP
systoti, (REAL 1 , or Rt-^C I and
i±h ihotir-r timt
ffuiiH Tho ..if n the ljorlitif>n
e^uipin* n; u, ihtiftort, in
u^aseri rn-er that o> ^ con^fn
rianul continuoui, flow s>sftm
of the 'ante L jpiv nv
9 Si/e the decanter and
at.s ot lated piping The decant
i ate K ralculated from the
mdxinium volume of liquid
dfH tinted pfr tank per cyrst
This volume is thin divided by
the dpsired decant or DRAW
time Fh^ DRAW period is
tVpcaily chosen to be appiox
irrutelv 4h minutts
4 3 Fuutoit! to be considered
tfirft can place constraints on She
dt ssqn process ate the ubidty 10
rntj'ntai" iriatmtnt qu«ihtv ,n a
single tank svrt°m the ot'linuim
or tpciximum sizes for nn in
diviciu.il '*vrtor unit in j mulli
tanl* tystem rind a* sirtd Judue
stoidfjf \olumc
The detiyn step., outline j abts^e
ilkFirate ,1 simplih^a app oac1^ in
d ftdtl ".tuot'on inanv itLi^iiv-^
r-rikijlrtion* m,i\ he
natrtix1! n* uj
oUn^vt flexibility
at bid] piari* opfnton dunru-tl
f'ow vaiiatior)1 jnd tiiffpn u ic
cv»nt h< ighia to • oir^Musnd io (lit
conditions ol sludqt
14
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5,0 Currently SBR wastewater treatment plants
are currently operating at several
sites in Australia, Canada, and
the United States. They include
plants at Rivercrest and Gtenka,
Manitoba, Canada; Choctaw,
Oklahoma; Grundy Center and
Eldora, Iowa; Culver, Indiana;
Poolesville, Maryland; Tarn-
worth Yamba, New South
Wales, Australia, The designs of
these plants differ in several
aspects, including inlet design,
aeration/mixing system design,
decanter design, but they ail
operate on sequencing batch
principles.
15
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6,0
Table 3 shows estimated costs
for constructing SBR systems to
handle flow rates of 379, 1893,
3785, and 18,925 m3/d (or 1, 5S
10 and 50 MGD, respectively), In
constructing this table, floating
aerators were considered, to
allow for comparison to other ac-
tivated sludge systems. Table 4
further defines the operation and
maintenance costs, A two tank
system was used for the 379
m3/d plant, and three tank
systems for the other three daily
flow rates. The design criteria for
cost purposes can be summarized
as follows:
Tables 5-8 show cost compar-
isons between SBR systems, and
conventional oxidation ditch and
activated sludge systems. The
cost estimates for the SBR are
conservative and do not neces-
sarily reflect the full potential of
that technology, because the in-
formation available on SBR
systems is limited. Even at
conservative estimates, however,
the SBR system is competitive.
Flow
(M3/d)
379
1,893
3,785
18,925
(MGD)
1
5
10
50
Sets of
Tanks
2
3
3
3
Tanks per
Set
1
1
1
4
Total
Volume |M3)
252
947
1,893
9,465
Costs are developed as per
January 1983, While the modular
design notion provides reasonable
for the three lower flow
systems, this approach
results in unreasonable costs for
the 18,925 m3/d facility. In par-
ticular, any appreciable economy
of scale is lost with respect to
items such as the inlet and dis-
charge structures and excavation
and concrete work, A more
detailed approach to in
this would likely result in ad-
ditional savings.
-------
3.
Cost for SBR for Four Daily Flow
Flow Rates fm3/d; MGD in parentheses)
Process Unit
Inlet Control System
Contact Chamber Baffle Walls
Aerators
Excavation, Concrete and/Handrail
Microprocessors
Level Control/Monitoring
Decant System
Subtotal (1)
Noncomponent Costs*
(2)
Engineering, Construction on Supervision
Contingencies**
Total Costs
Annual Operation and Maintenance Costs
Worth Costs* * *
Costs/(m3/d)
379
(1)
$ 2,000
2,000
25,000
70,000
10,000
2,000
9,000
$120,000
30,000
$150,000
45,000
$195,000
13,000
$329,000
§ 870
1893
(5)
$
4,000
50,000
1 50,000
10,000
4,000
16,000
$237,000
59,000
$296,000
89,000
$385,000
24,000
$632,000
$ 330
3785
(10)
$
5,000
60,000
250,000
10,000
4,000
18,000
§351,000
88,000
$439,000
132,000
$571,000
40,000
$983,000
$ 280
18,925
(50)
$
24,000
256,000
840,000
10,000
16,000
90,000
$1,256,000
314,000
$1,570,000
471,000
$2,041,000
148,000
$3,564,000
$ 190
* At 25 percent of subtotal (1), includes piping, electrical, instrumentation and site preparation,
** At 30 of (2),
*** Present worth computed at 7 3/8 percent rate and 20 year life fPWF = 10,29213),
Add worth 0 & M to Total Capital Costs.
Source: Reference 2,
17
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4.
Operation Maintenance
Cost Estimates
for the for
Four Daily
Flow
Flow Rates (m3/d; MOD in parentheses)
Costs (dollar/yr)
Operation Labor
Maintenance Labor
Power*
Material
TOTAL O & IV! (rounded)
379
(1)
$ 7,885
1,319
2,232
1,890
$13,000
1893
!5)
$10,046
1,941
9,660
2,640
$24,000
3785
(10)
$15,518
2,346
18,900
3,722
$40,000
18,925
(50)
$
5,062
96,600
13,136
$148,000
* Includes mixing, aeration decanting at a power rate of $0.06/kWh,
Source: Reference 2,
18
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5,
Comparison-379 (1
Process Unit
Raw Sewage Pumping
Preliminary Treatment
Aeration/Clarification
Chiorination
Aerobic Digestion
Sludge Lagoons
(1)
Noncomponent Costs*
(2)
Engineering, Construction Supervision
and Contingencies* *
Total Capital Cost
Annual Operation and Maintenance Costs
Present Worth Costs* " *
Oxidation Ditch
$
24,000
2.40,000
48,000
_
7,000
$
90,000
§
135,000
$
65,000
$1,253,000
SBR
$ 40,000
24,000
120,000
48,000
40,000
7,000
$
70,000
$
105,000
$ 454,000
58,000
$1,051 000
* At 25 percent of subtotal 11), includes piping, electrical, instrumentation and sue preparation
** At 30 percent of subtotal (2),
*** Present worth computed at 7 3/8 percent interest rate and 20 year life (PWF = 10,29213), Add
present worth 0 & M costs to Total installed Capital Costs,
Source: Reference 2,
W
-------
6.
Cost Comparison -1,893 m3/d (5 MGD)
Process Unit
Raw Sewage Pumping
Preliminary Treatment
Primary Clarification
Aeration/Clarification
Chlorination
Gravity Thickening
Aerobic Digestion
Vacuum Filtration
Sludge Lagoons
Chemical Feed Systems
Subtotal ( 1 )
Noncomponent Costs*
Subtotal (2)
Engineering, Construction Supervision
and Contingencies**
Total Installed Capital Costs
Annual Operation and Maintenance Costs
Present Worth Costs* * *
Facility
Conventional
Activated
Sludge
$ 248,000
36,000
128,000
448,000
80,000
64,000
208,000
272,000
1 2,000
44,000
$1,540,000
385,000
$1,925,000
578,000
$2,503,000
166,000
$4,212,000
Oxidation
Ditch
$ 248,000
36,000
—
416,000
80,000
64,000
1
272,000
12,000
44,000
$1,324,000
331,000
$1,655,000
497,000
$2,152,000
1 50,000
$3,696,000
SBR
$ 248,000
36,000
—
237,000
80,000
64,000
208,000
272,000
1 2,000
44,000
$1,201,000
300,000
$1,501,000
450,000
§1,951,000
1 50,000
$3,495,000
* At 25 percent of subtotal 0), includes piping, electrical, instrumentation and site preparation,
** At 30 percent of subtotal (2),
*** Present worth computed at 7 3/8 percent interest rate and 20 year life fPWF = 10,29213). Add
present worth 0 & M costs to Total Installed Capital Costs,
Source: Reference 2,
-------
7,
Comparison — 3,785 m3/d (10
Process Unit
Raw Sewage Pumping
Preliminary Treatment
Primary Clarification
Aeration/Clarification
Chlorination
Gravity Thickening
Aerobic Digestion
Vacuum Filtration
Sludge Handling and Landfilling
Chemical Feed Systems
Subtotal (11
Noncomponent Costs*
Subtotal (2)
Engineering, Construction Supervision
and Contingencies**
Total Installed Capital Costs
Facility
Conventional
Activated
Sludge
$ 312,000
56,000
164,000
824,000
104,000
68,000
264,000
288,000
76,000
44,000
$2,000,000
500,000
$2,500,000
750,000
$3,250,000
Annual Operation and Maintenance Costs 230,000
Present Worth Costs* * *
$5,817,000
Oxidation
Ditch
$ 312,000
56,000
—
576,000
104,000
68,000
160,000
272,000
68,000
44,000
$1,860,000
415,000
$2,075,000
823,000
$2,698,000
190,000
$4,654,000
SBR
$ 312,000
56,000
—
351,000
104,000
68,000
264,000
288,000
76,000
44,000
§1,563,000
391,000
$1,954,000
586,000
$2,540,000
190,000
$4,496,000
* At 25 percent of subtotal (1), includes piping, electrical, instrumentation and site preparation.
** At 30 percent of subtotal (2).
*** Present worth computed at 7 3/8 percent interest rate and 20 year life fPWF = 10,29213). Add
present worth 0 & M costs to Total Installed Capital Costs.
Source: Reference 2.
-------
8,
Cost Comparison^ 18,925 m3/d (50 Facility
Process Unit
Raw Sewage Pumping
Preliminary Treatment
Primary Clarification
Aeration/Clarification
Chlorination
Gravity Thickening
Aerobic Digestion
Vacuum Filtration
Sludge Handling and Landfilling
Chemical Feed Systems
(1)
Noncomponent Costs*
Subtotal (2)
Engineering, Construction Supervision
and Contingencies**
Total Installed Capital Costs
Annual Operation and Maintenance Costs
Present Worth Costs***
Conventional
Activated
Sludge
$
148,000
352,000
1,720,000
160,000
88,000
824,000
496,000
88,000
56,000
$ 4,332,000
1,083,000
$ 5,415,000
1,625,000
$ 7,040,000
490,000
§12,083,000
Oxidation
Ditch
$
148,000
—
1,952,000
1
88,000
258,000
280,000
72,000
44,000
§ 3,600,000
900,000
$ 4,500,000
1,350,000
§
455,000
$10,533,000
SBR
$
148,000
—
1,256,000
160,000
88,000
824,000
496,000
88,000
56,000
$ 3,516,000
879,000
$ 4,395,000
1,319,000
§ 5,714,000
455,000
$10,397,000
* At 25 percent of subtotal (1), includes piping, electrical, instrumentation site preparation,
** At 30 percent of subtotal (2),
*** Present worth computed at 7 3/8 percent interest rate and 20 year life fPWF = 10,29213), Add
present worth 0 & M costs to Total Installed Capital Costs,
Source: Reference 2,
22
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This report been reviewed by
the Center for Environmental
Research Information, U.S.
Environmental Protection
Agency, Cincinnati, OH,
approved for publication.
Approval does not signify that the
contents necessarily reflect the
views and policies of the U.S.
Environmental Protection
Agency, nor does mention of
names or commercial
products constitute endorsement
or recommendation for use.
This report was prepared for the U.S. Environmental Protection Agency
by Dynamac Corporation, Rockville, MD, Mr. Thomas Bertell is the
principal contributor. Mr. Denis Lussier is the EPA Project Officer.
Major portions of this document are taken from two recent EPA
reports: "Technology Assessment of Sequencing Batch Reactors"
authored by Robert L irvine, Ph.D., under EPA Contract
No. 68-03-3055, and "Technical Evaluation of Sequencing Batch
Reactors" authored by IVIadan L. Arora, Ph.D., under EPA Contract
No. 68-03-1821.
The photographs in this report (except the cover photograph) show
the Poolesville, MD SBR Facility. These were provided by John A. Hart
of Hart's Custom Photographic Services, Pooiesville, MD. The cover
photograph was provided by Austgen Biojet, San Francisco, CA,
showing one of their facilities.
23
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