United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-020 Apr. 1983
&ERA Project Summary
Full-Scale Study of Sequencing
Batch Reactors
Robert L Irvine and Lloyd H. Ketchum
A conventional activated-sludge
system owned and operated by the
town of Culver, Indiana, was converted
to a two-tank sequencing batch reactor
(SBR) treatment plant. The average
flow during SBR operation was 1340
mVday. Loadings varied from 0.2 to
0.4 kg BOD6/day per kg mixed liquor
volatile suspended solids (MLVSS) on
an aeration-time-adjusted basis, and
the sludge age ranged between 15 and
45 days. During the first year of SBR
operation (May 1980 to May 1981), the
effluent BOD6, SS, and phosphorus
concentrations averaged less than 10,
8, and 0.5 g/m3, respectively. Phos-
phorus was removed chemically by
adding either ferric chloride or alum.
Nitrogen was removed biologically,
after blower malfunctions were
remedied, during the late spring of
1981. Between August and December
of 1981, effluent BOD6, SS, and
phosphorus levels were similar to those
achieved during the first year; effluent
ammonium and nitrite plus nitrate
nitrogen concentrations were 1.1 and
1.3 g/m3, respectively. Overall, 90% of
the inorganic nitrogen was removed
biologically. The demonstration study
showed the SBR to be a viable
alternative to conventional, continuous-
flow, activated-sludge treatment of
domestic wastewaters for BODB and
SS removal, nitrification, denitrifica-
tion, and chemical precipitation of
phosphorus.
This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory. Cincinnati, OH,
to announce key findings of the
research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Bench-scale studies of batch reactors
for treatment of municipal wastewater at
the University of Notre Dame had shown
many benefits for the sequencing batch
reactor (SBR) approach. Batch systems
were employed in many cities during the
early 1900's, but they fell into disfavor
because of the need for manual valving
changes. Using the newly developed
electronic process controllers along with
the batch process and automated valves
seemed a logical approach to
reinstituting this type of process.
The town of Culver, Indiana, agreed to
convert their existing continuous-flow,
activated-sludge, plant into a two-tank
sequencing batch process. Retrofitting
the facility was rather simple and
involved coupling automatic valves and
blower controls with a process controller.
To account for changing water levels in
the batch process, floating weirs were
constructed for purified effluent removal.
Plant Operation
The two existing aeration tanks were
operated in sequence, with each tank
fulfilling the various process cycles
needed to accomplish the desired treat-
ment. The cycle times were controlled by
liquid-level sensors that triggered the
process controller to implement valving
functions. Typical cycles and times are
listed in Table 1.
Each tank completes a cycle in 6 hours,
and therefore over a 24-hour period, each
tank performs four treatment sequences.
During FILL, the tank that has just
completed IDLE receives primary
effluent until some preset liquid level is
reached. The REACT period furnishes
dissolved oxygen for completion of the
desired biological reactions. The tank
-------
Table 1. Typical Cycles and Times for
Aeration Tanks
Time (hours)
Table 2. Phase I Secondary Effluent Quality
Cycle
Fill
React
Settle
Draw
Idle
Tank 1
2.9
0.7
0.7
0.7
1.0
Tank 2
3.1
0.4
0.7
0.1
1.1
Total
6.0
6.0
then enters a quiescent period with no
aeration to separate mixed liquor and
effluent. Effluent is removed during
DRAW.Waste-activated sludge is
removed from the reactor during IDLE.
The second tank in an SBR process
begins to fill when the first tank starts the
REACT cycle. Thus one tank is always in
the FILL cycle at any given instant.
Results
During the 2-year demonstration at
Culver, the SBR was operated in two
phases. Phase I was to produce
secondary effluent quality, and Phase II
was to achieve advanced waste treatment
objectives. During both phases, ferric
chloride was used to keep phosphorus
levels within the state-mandated limit of
1 mg/L Results for Phase I appear in
Table 2.
During Phase II, conditions conducive
to nitrification and denitrification were
imposed on the SBR process. Results for
this advanced treatment are shown in
Table 3.
Conclusions
As a result of this demonstration, the
SBR process has been shown to be a
viable option for municipal wastewater
Sample Point
Raw Wastewater
Primary Effluent
SBR Final Effluent
BOD,,
173
132
8
SS
136
81
8
(mg/LI
TP
6.3
5.2
0.4
NH^+N
20
19
18
NOx-N
2.8
2.6
0.4
Table 3. Phase II Advanced Treatment Quality
(mg/Li
Sample Point
BOD,
SS
TP
NH* +N NO* -N
Raw Wastewater
Primary Effluent
SBR Final Effluent
118
92
6
133
64
3
5.8
4.8
0.9
16.5
14.0
0.4
1.7
1 7
1.2
treatment. The inherent flexibilty of the
process allows operation to achieve
effluent levels for either secondary or
advanced waste treatment. The town of
Culver has been so satisfied with this
method of treatment that their municipal
facility has continued with the SBR
operation after conclusion of the
demonstration project.
The full report was submitted in fulfill-
ment of Grant No. R-806598 by the
University of Notre Dame under the
sponsorship of the U.S. Environmental
Protection Agency.
Robert L Irvine and Lloyd H. Ketchum are with the University of Notre Dame,
Notre Dame, IN 46556.
E. F. Barth is the EPA Project Officer (see below).
The complete report, entitled "Full-Scale Study of Sequencing Batch Reactors,"
(Order No. PB 83-183 186; Cost: $11.50, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
&U.S. Government Printing Office: 1983-659-017/7049
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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