United States       Office of Water       EPA 932-F-99-073
Environmental Protection  Washington, D.C.      September 1999
Agency


Wastewater


Technology Fact Sheet


Sequencing Batch Reactors

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                       United States
                       Environmental Protection
                       Agency
 Office of Water
 Washington, D.C.
EPA 932-F-99-073
September 1999
v>EPA           Waste water
                       Technology Fact Sheet
                       Sequencing  Batch  Reactors
DESCRIPTION

The sequencing batch reactor (SBR) is a fill-and-
draw  activated sludge system for wastewater
treatment. In this system, wastewater is added to a
single  "batch"  reactor,   treated  to  remove
undesirable  components,  and  then  discharged.
Equalization, aeration, and clarification can all be
achieved using a single batch reactor. To optimize
the performance of the system, two or more batch
reactors are used in a predetermined sequence  of
operations.  SBR systems have been successfully
used  to  treat  both   municipal  and  industrial
wastewater.    They   are  uniquely  suited  for
wastewater treatment applications characterized by
low or intermittent flow conditions.

Fill-and-draw batch processes similar to the SBR
are not a recent development as commonly thought.
Between 1914 and 1920, several full-scale fill-and-
draw systems were in operation. Interest in SBRs
was revived in the late 1950s and early 1960s, with
the development of new equipment and technology.
Improvements in aeration devices and controls have
allowed SBRs to  successfully  compete  with
conventional activated sludge systems.

The unit processes of the SBR and conventional
activated sludge systems are the same. A 1983 U.S.
EPA report, summarized this by stating that "the
SBR is no more than an activated sludge system
which operates in time rather than in space." The
difference between the two technologies is that the
SBR performs equalization, biological  treatment,
and secondary clarification in a single tank using a
timed control sequence. This type of reactor does,
in some cases, also perform primary clarification. In
a conventional activated sludge system, these unit
processes would be accomplished by using separate
tanks.

A modified version of the SBR is the Intermittent
Cycle Extended Aeration System (ICEAS).  In the
ICE AS system, influent wastewater flows into the
reactor on a continuous basis. As such, this is not
a true batch reactor, as is the conventional SBR. A
baffle wall may be used in the ICEAS to buffer this
continuous inflow. The design configurations of the
ICEAS and the SBR are otherwise very similar.

Description of a Wastewater  Treatment Plant
Using an SBR

A typical process flow schematic for a municipal
wastewater treatment plant using an SBR is shown
in Figure 1.  Influent wastewater generally passes
through screens and grit removal prior to the SBR.
The wastewater then enters a partially filled reactor,
containing  biomass, which is  acclimated to the
wastewater constituents during preceding cycles.
Once the  reactor  is  full,  it behaves  like a
conventional activated sludge system, but without a
continuous influent or effluent flow. The aeration
and mixing is discontinued  after  the biological
reactions are complete, the biomass settles, and the
treated supernatant is removed.  Excess biomass is
wasted at any time during the cycle.  Frequent
wasting results in holding the mass ratio of influent
substrate to biomass nearly constant from cycle to
cycle. Continuous flow systems hold the mass ratio
of influent substrate to  biomass  constant by
adjusting  return  activated   sludge  flowrates
continually as influent flowrates, characteristics, and
settling tank underflow concentrations vary. After
the SBR, the "batch" of wastewater may flow to an
equalization basin where the wastewater flowrate to

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 additional unit processed can be is controlled at a
 determined rate.  In some cases the wastewater is
 filtered to  remove additional  solids  and then
 disinfected.

 As illustrated in Figure 1, the solids handling system
 may consist of a thickener and an aerobic digester.
 With SBRs there is no need for return activated
 sludge  (RAS) pumps  and  primary sludge (PS)
 pumps  like  those  associated with  conventional
 activated sludge systems.  With the SBR, there is
 typically only one sludge to handle.  The need for
 gravity thickeners prior to digestion is determined
               TO SOLIDS HANDLING,
                 DISPOSAL, OR
                BENEFICIAL REUSE
                       DIGESTION
   INFLUENT-
                                      EFFLUENT
                       EQUALIZATION FILTRATION DISINFECTION
Source: Parsons Engineering Science, 1999.

   FIGURE 1 PROCESS FLOW DIAGRAM
            FOR A TYPICAL SBR

on a  case  by case  basis depending on  the
characteristics of the sludge.
An SBR serves as an equalization basin when the
vessel is filling with wastewater, enabling the system
to tolerate peak flows or peak loads in the influent
and to equalize them in the batch reactor. In many
conventional activated sludge  systems, separate
equalization is needed to protects the biological
system from peak flows, which may wash out the
biomass, or peak loads,  which may upset the
treatment process.

It should also be noted that primary clarifiers are
typically not required  for  municipal  wastewater
applications prior to an SBR. In most conventional
activated  sludge  wastewater  treatment  plants,
 primary clarifiers are used prior to the biological
 system.   However,  primary  clarifiers  may  be
 recommended by the SBR manufacturer if the total
 suspended solids  (TSS) or biochemical oxygen
 demand (BOD) are greater than 400 to 500 mg/L.
 Historic  data  should be evaluated and  the SBR
 manufacturer  consulted   to determine  whether
 primary clarifiers or equalization are recommended
 prior to  an  SBR  for  municipal  and  industrial
 applications.

 Equalization  may  be required  after the  SBR,
 depending on  the  downstream  process.   If
 equalization is not used prior to filtration, the filters
 need to be sized in order to receive  the batch of
 wastewater from the SBR, resulting in a large
 surface area required for filtration. Sizing filters to
 accept these "batch" flows is usually not feasible,
 which is why equalization is used between an SBR
 and  downstream filtration. Separate equalization
 following the  biological  system is generally not
 required  for most conventional  activated sludge
 systems,  because the flow is on a continuous and
 more constant basis.

 APPLICABILITY

 SBRs are typically used at flowrates of 5 MOD or
 less. The more sophisticated operation required at
 larger SBR plants  tends to discourage the use of
these plants for large flowrates.

As these  systems have a relatively small footprint,
they are useful for areas where the available land is
limited. In addition, cycles within the system can be
easily modified for nutrient removal in the future, if
it becomes necessary. This makes SBRs extremely
flexible to adapt to regulatory changes for effluent
parameters such as nutrient removal. SBRs are also
very cost  effective if treatment beyond biological
treatment is required, such as filtration.

ADVANTAGES AND DISADVANTAGES

Some advantages and disadvantages of SBRs are
listed below:

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Advantages

  Equalization,  primary  clarification  (in most
   cases), biological  treatment,  and secondary
   clarification can be achieved in a single reactor
   vessel.

  Operating flexibility and control.

  Minimal footprint.

  Potential  capital cost savings by eliminating
   clarifiers and other equipment.

Disadvantages

  A  higher  level of sophistication is  required
   (compared to conventional systems), especially
   for larger systems, of timing units and controls.

  Higher level of  maintenance  (compared  to
   conventional  systems) associated with more
   sophisticated controls, automated switches, and
   automated valves.

  Potential of discharging floating or settled sludge
   during the DRAW or decant phase with some
   SBR configurations.

  Potential  plugging of aeration devices during
   selected operating cycles,  depending  on the
   aeration system used by the manufacturer.

  Potential requirement for equalization after the
   SBR, depending on the downstream processes.

DESIGN CRITERIA

For any wastewater treatment plant design, the first
step  is  to  determine  the anticipated  influent
characteristics of the wastewater and the effluent
requirements for the proposed  system.   These
influent parameters typically include  design flow,
maximum daily  flow BOD5, TSS, pH,  alkalinity,
wastewater  temperature, total Kjeldahl  nitrogen
(TKN),  ammonia-nitrogen  (NH3-N),  and  total
phosphorus  (TP).   For  industrial and  domestic
wastewater, other site specific parameters may also
be required.
The state regulatory agency should be contacted to
determine the effluent requirements of the proposed
plant. These effluent discharge parameters will be
dictated  by  the state in the National Pollutant
Discharge Elimination  System (NPDES) permit.
The parameters typically permitted for municipal
systems  are  flowrate,   BOD5,  TSS,  and  Fecal
Coliform.  In addition,  many states are moving
toward requiring nutrient removal. Therefore, total
nitrogen  (TN), TKN, NH3-N, or TP may also be
required.  It is imperative  to establish effluent
requirements because they will impact the operating
sequence of the SBR.  For example, if there is a
nutrient  requirement  and  NH3-N  or TKN  is
required, then nitrification will be necessary.   If
there  is  a  TN   limit,  then  nitrification  and
denitrification will be necessary.

Once the influent and effluent characteristics of the
system are determined,  the engineer will typically
consult  SBR manufacturers  for  a recommended
design.  Based on these parameters, and other  site
specific parameters such as temperature, key design
parameters are selected for the system. An example
of these parameters for a wastewater system loading
is listed in Table 1.

  TABLE 1 KEY DESIGN PARAMETERS
      FOR A CONVENTIONAL LOAD

                     Municipal      Industrial

 Food to Mass (F:M)    0.15-0.4/day      0.15-
                                    0.6/day
 Treatment Cycle
 Duration
4.0 hours
4.0 - 24
 hours
 Typically Low Water    2,000-2,500    2,000 - 4,000
 Level Mixed Liquor         mg/L          mg/L
 Suspended Solids

 Hydraulic Retention     6-14 hours       varies
 Time                                    	

 Source: AquaSBR Design Manual, 1995.
Once the key design parameters are determined, the
number of cycles per day, number of basins, decant
volume, reactor size, and detention times can be
calculated.  Additionally, the aeration equipment,
decanter, and associated piping can then be sized.

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Other site specific information is needed to size the
aeration equipment, such as site elevation  above
mean sea level, wastewater temperature, and total
dissolved solids concentration.

The operation of an SBR is based on the fill-and-
draw principle, which consists of the following five
basic steps: Idle, Fill,  React,  Settle,  and  Draw.
More than one operating strategy is possible during
most of these steps.  For  industrial  wastewater
applications,  treatability   studies  are  typically
required  to  determine  the optimum operating
sequence.    For  most  municipal   wastewater
treatment plants, treatability studies are not required
to  determine the operating  sequence  because
municipal wastewater flowrates and characteristic
variations  are  usually  predictable  and  most
municipal designers will follow conservative design
approaches.

The Idle step occurs between the Draw and the Fill
steps, during which treated effluent is removed  and
influent wastewater is added.  The length of the Idle
step varies depending on the influent flowrate and
the operating  strategy.  Equalization is achieved
during this  step  if variable  idle times are used.
Mixing to condition the biomass and sludge wasting
can  also be  performed  during  the  Idle step,
depending on the operating strategy.

Influent wastewater is added to the reactor during
the Fill step.  The following three variations are
used for the Fill step and any or all of them may be
used depending on the operating strategy:  static fill,
mixed fill, and aerated fill.  During static fill, influent
wastewater is added to the biomass already present
in the SBR.  Static fill is characterized by no mixing
or aeration, meaning that there will  be a high
substrate (food) concentration when mixing begins.
A high food to microorganisms (F:M) ratio creates
an environment favorable to floe forming organisms
versus filamentous organisms, which provides good
settling characteristics for the sludge. Additionally,
static fill conditions favor organisms that produce
internal storage  products during  high  substrate
conditions, a requirement for biological phosphorus
removal.  Static  fill  may be compared to using
"selector" compartments in a conventional activated
sludge system to  control the F:M ratio.
Mixed fill is classified by mixing influent organics
with  the  biomass,  which  initiates  biological
reactions. During mixed fill, bacteria biologically
degrade  the organics and use residual oxygen or
alternative electron acceptors,  such  as  nitrate-
nitrogen.  In this environment, denitrification may
occur under these anoxic conditions. Denitrification
is the biological conversion of nitrate-nitrogen to
nitrogen gas. An anoxic condition is defined as an
environment in which oxygen  is not present  and
nitrate-nitrogen is used by the microorganisms as
the electron acceptor. In a conventional biological
nutrient removal (BNR) activated sludge  system,
mixed fill is comparable to the anoxic zone which is
used for  denitrification.  Anaerobic conditions  can
also be achieved during the mixed fill phase.  After
the microorganisms use the nitrate-nitrogen, sulfate
becomes  the  electron   acceptor.     Anaerobic
conditions are characterized by the lack of oxygen
and sulfate as the electron acceptor.

Aerated Fill is classified by aerating the contents of
the reactor to begin the aerobic reactions completed
in the React step.   Aerated Fill can  reduce  the
aeration time required in the React step.

The biological reactions are completed in the React
step, in which mixed react and aerated react modes
are available.   During aerated react, the  aerobic
reactions initialized during aerated fill are completed
and nitrification can be achieved. Nitrification is the
conversion of ammonia-nitrogen to nitrite-nitrogen
and ultimately to nitrate-nitrogen. If the mixed react
mode is selected, anoxic conditions can be attained
to achieve denitrification. Anaerobic conditions can
also be  achieved in the  mixed  react mode  for
phosphorus removal.

Settle  is  typically  provided  under  quiescent
conditions in the SBR. In some cases, gentle mixing
during the initial stages  of settling may result in a
clearer effluent and a more concentrated settled
sludge. In an SBR, there are no influent or effluent
currents to interfere with the settling process as in a
conventional activated sludge system.

The Draw step uses a decanter to remove  the
treated effluent, which is the primary distinguishing
factor between different SBR manufacturers.   In
general,  there are  floating decanters  and  fixed

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decanters.    Floating  decanters  offer  several
advantages over fixed decanters as described in the
Tank and Equipment Description Section.

Construction

Construction of SBR systems can typically require
a smaller  footprint  than  conventional activated
sludge systems because the SBR often eliminates the
need for primary clarifiers.  The SBR never requires
secondary clarifiers.   The  size of the  SBR tanks
themselves will be site specific, however the SBR
system is  advantageous  if space  is limited at the
proposed site. A few case  studies are presented in
Table 2  to provide  general  sizing estimates  at
different flowrates. Sizing of these systems is site
specific and these case studies do not reflect every
system at that size.

 TABLE 2  CASE STUDIES FOR SEVERAL
           SBR INSTALLATIONS
Flow
(MGD)
0.012
0.10
1.2
1.0
1.4
1.46
2.0
4.25
5.2
Reactors
No.
1
2
2
2
2
2
2
4
4
Size
(feet)
18x12
24x24
80x80
58x58
69x69
78x78
82x82
104x80
87x87
Volume
(MG)
0.021
0.069
0.908
0.479
0.678
0.910
0.958
1.556
1.359
Blowers
No.
1
3
3
3
3
4
3
5
5
Size
(HP)
15
7.5
125
40
60
40
75
200
125
Note: These case studies and sizing estimates were provided
by Aqua-Aerobic Systems,  Inc. and are  site specific to
individual treatment systems.

The actual  construction of the SBR tank and
equipment may be comparable  or simpler than a
conventional  activated  sludge system.    For
Biological Nutrient Removal (BNR) plants, an SBR
eliminates the need  for return activated  sludge
(RAS) pumps and pipes.  It may also eliminate the
need for internal Mixed  Liquor Suspended Solid
(MLSS) recirculation,  if this is being used in a
conventional BNR system to return nitrate-nitrogen.
The control system of an SBR operation is more
complex  than a  conventional  activated  sludge
system and includes automatic switches, automatic
valves, and instrumentation.  These controls  are
very sophisticated in  larger systems.  The SBR
manufacturers indicate that most SBR installations
in the United States are used for smaller wastewater
systems of less than two million gallons per day
(MGD) and some references recommend SBRs only
for small communities where land is limited.  This is
not always the case, however, as the largest SBR in
the world is currently a  10 MGD system in  the
United Arab Emirates.

Tank and Equipment Description

The SBR  system  consists of a tank, aeration and
mixing equipment, a decanter, and a control system.
The central features of the SBR system include  the
control unit and the automatic switches and valves
that sequence and time the different operations.
SBR  manufacturers   should  be  consulted  for
recommendations  on  tanks  and equipment. It is
typical to use a complete SBR system recommended
and supplied by a single SBR manufacturer. It is
possible, however, for an engineer to design an SBR
system, as all  required  tanks,  equipment, and
controls   are  available   through  different
manufacturers.    This  is not typical of SBR
installation because of the level of sophistication of
the instrumentation and  controls associated with
these systems.

The SBR tank is typically constructed with steel or
concrete.  For industrial applications, steel tanks
coated for corrosion control  are  most common
while concrete tanks are the most common  for
municipal treatment of domestic wastewater. For
mixing and aeration, jet aeration systems are typical
as they allow mixing either with or without aeration,
but other aeration and mixing systems are also used.
Positive displacement blowers are typically used for
SBR design to handle wastewater level variations in
the reactor.

As  previously  mentioned, the  decanter  is  the
primary piece  of equipment that distinguishes
different SBR manufacturers.  Types of decanters
include floating and fixed. Floating decanters offer
the advantage of maintaining the inlet orifice slightly

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below the water surface to minimize the removal of
solids in the effluent removed during the DRAW
step.  Floating decanters also offer the operating
flexibility to vary fill-and-draw volumes.  Fixed
decanters are built into the side of the basin and can
be used if the Settle step is extended. Extending the
Settle step minimizes the chance that solids in the
wastewater will float over the fixed decanter.   In
some cases, fixed decanters are less expensive and
can be designed to allow the operator to lower or
raise the level of the decanter.  Fixed decanters do
not offer the operating  flexibility of the floating
decanters.

Health and Safety

Safety  should  be the primary  concern  in every
design  and system operation. A properly designed
and operated system will minimize potential health
and safety concerns. Manuals such as the Manual of
Practice  (MOP)  No.  8,  Design  of Municipal
Wastewater  Treatment Plants, and MOP No. 11,
Operation of Municipal Wastewater Treatment
Plants should be consulted to minimize these risks.
Other appropriate industrial wastewater treatment
manuals, federal regulations, and state regulations
should  also be  consulted for the  design  and
operation of wastewater treatment systems.

PERFORMANCE

The performance of SBRs is typically comparable to
conventional activated sludge systems and depends
on  system  design  and  site  specific  criteria.
Depending on their mode of operation, SBRs can
achieve good BOD and nutrient removal.   For
SBRs,  the BOD removal efficiency is generally 85
to 95 percent.

SBR manufacturers will typically provide a process
guarantee to produce an effluent of less than:

  10 mg/L BOD

  lOmg/LTSS

  5-8 mg/L TN

  1-2 mg/L TP
OPERATION AND MAINTENANCE

The SBR typically eliminates the need for separate
primary and secondary clarifiers in most municipal
systems, which reduces operations and maintenance
requirements.  In addition, RAS pumps are  not
required.   In conventional  biological nutrient
removal systems, anoxic basins, anoxic zone mixers,
toxic  basins, toxic basin aeration equipment, and
internal MLSS nitrate-nitrogen recirculation pumps
may be necessary.   With the SBR, this can be
accomplished in one reactor using aeration/mixing
equipment, which will  minimize operation  and
maintenance requirements otherwise be needed for
clarifiers and pumps.

Since the heart of the SBR system is the controls,
automatic  valves, and automatic switches, these
systems may  require more  maintenance than a
conventional activated sludge system. An increased
level of sophistication usually equates to more items
that can fail or require maintenance.  The level of
sophistication may be very advanced in larger SBR
wastewater treatment plants requiring a higher level
of  maintenance  on  the automatic valves  and
switches.

Significant operating  flexibility is associated with
SBR systems.  An SBR can be set up to simulate
any conventional activated sludge process, including
BNR systems. For example, holding times in the
Aerated React mode of an SBR can be varied to
achieve simulation of a contact stabilization system
with a typical hydraulic retention time (HRT) of 3.5
to 7 hours or, on the other end of the spectrum, an
extended aeration treatment system with a typical
HRT of 18 to 36 hours.  For a BNR  plant, the
aerated react mode (oxic conditions) and the mixed
react modes (anoxic conditions) can be alternated to
achieve nitrification and denitrification. The mixed
fill  mode and  mixed react mode can be used to
achieve denitrification using anoxic conditions. In
addition, these modes can ultimately be used to
achieve an anaerobic condition where phosphorus
removal can occur. Conventional activated sludge
systems typically require additional tank volume to
achieve such flexibility. SBRs operate in time rather
than in space and the number of cycles per day can
be varied to control desired effluent limits, offering
additional flexibility with an SBR.

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COSTS

This section includes some general guidelines as
well as some general cost estimates for planning
purposes. It should be remembered that capital and
construction cost estimates are site-specific.

Budget level cost estimates presented in Table 3 are
based on projects that occurred from 1995 to 1998.
Budget level  costs include such as the blowers,
diffusers, electrically operated valves, mixers, sludge
pumps, decanters, and the control panel.  All costs
have been updated to March 1998 costs, using an
ENR construction cost index of 5875 from the
March 1998 Engineering News Record, rounded off
to the nearest thousand dollars.

    TABLE 3 SBR EQUIPMENT COSTS
    BASED ON DIFFERENT PROJECTS
    Design Flowrate
        (MGD)
   Budget Level
Equipment Costs ($)
0.012
0.015
1.0
1.4
1.46
2.0
4.25
94,000
137,000
339,000
405,000
405,000
564,000
1,170,000
 Source: Aqua Aerobics Manufacturer Information, 1998.
In Table 4, provided a range of equipment costs for
different design flowrates is provided.
                         TABLE 4  BUDGET LEVEL EQUIPMENT
                          COSTS BASED ON DIFFERENT FLOW
                                          RATES
                         Design Flowrate
                              (MGD)
                    Budget Level Equipment
                           Costs ($)
                                1

                                5

                                10

                                15

                                20
                        150,000-350,000

                        459,000 - 730,000

                       1,089,000-1,370,000

                           2,200,000

                       2,100,000-3,000,000
Note: Budget level cost estimates provided by Babcock King -
Wilkinson, L.P., August 1998.

Again the equipment cost items provided do not
include  the  cost   for  the   tanks,   sitework,
excavation/backfill,  installation,   contractor's
overhead and profit,  or  legal,  administrative,
contingency, and engineering services. These items
must  be  included  to  calculate  the  overall
construction costs of an SBR system.  Costs for
other  treatment  processes,  such  as  screening,
equalization,  filtration,  disinfection, or  aerobic
digestion, may be included if required.

The ranges of construction costs for a complete,
installed SBR wastewater treatment system are
presented in Table 5. The variances in the estimates
are due to the  type of sludge handling facilities and
the differences in newly constructed plants versus
systems that use existing  plant facilities. As such, in
some cases these estimates include other processes
required in an SBR wastewater treatment plant.

     TABLE 5 INSTALLED COST PER
  GALLON OF WASTEWATER TREATED
                                                   Design Flowrate
                                                        (MGD)
                                                  Budget Level
                                                 Equipment Cost
                                                    ($/gallon)
                                                       0.5- 1.0

                                                       1.1 - 1.5

                                                       1.5-2.0
                                                    1.96-5.00

                                                    1.83-2.69

                                                    1.65-3.29
                                                Note: Installed cost estimates obtained from Aqua-Aerobics
                                                Systems, Inc., August 1998.

                                                There is typically an economy of scale associated
                                                with construction costs for wastewater treatment,

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meaning that larger treatment plants can usually be
constructed at a lower cost per gallon than smaller
systems. The use of common wall construction for
larger treatment systems, which can be  used for
square or rectangular SBR reactors, results in this
economy of scale.

Operations  and  Maintenance   (O&M)   costs
associated with an SBR system may be similar to a
conventional activated sludge system. Typical cost
items associated with wastewater treatment systems
include  labor,  overhead,  supplies, maintenance,
operating administration, utilities, chemicals, safety
and training, laboratory testing, and solids handling.
Labor  and maintenance  requirements  may  be
reduced in SBRs because clarifiers, clarification
equipment, and RAS pumps may not be necessary.
On the other hand, the maintenance requirements
for the automatic valves and switches that control
the sequencing may be more intensive than for a
conventional activated sludge system.  O&M costs
are site specific and may range from $800 to $2,000
dollars per million gallons treated.

REFERENCES

1.     AquaSBR Design Manual. Mikkelson, K.A.
      of Aqua-Aerobic Systems. Copyright 1995.

2.     Arora, Madan L.  Technical Evaluation of
      Sequencing Batch Reactors.  Prepared for
      U.S. EPA. U.S. EPA Contract No. 68-03-
       1821.

3.     Engineering News-Record. A publication of
      the McGraw Hill  Companies,  March 30,
       1998.

4.     Irvine, Robert L. Technology Assessment of
      Sequencing Batch Reactors.  Prepared for
      U.S. EPA. U.S. EPA Contract No. 68-03-
      3055.

5.     Liu, Liptak,  and  Bouis.   Environmental
      Engineer's Handbook,  2nd edition.   New
      York:  Lewis Publishers.

6.     Manufacturers   Information.     Aqua-
      Aerobics, Babcock King-Wilkinson, L.P.,
      Fluidyne, and Jet Tech Systems, 1998.
7.     Metcalf  &  Eddy,   Inc.   Wastewater
       Engineering: Treatment, Disposal, Reuse.
       3rd edition. New York:  McGraw Hill.

8.     Parsons Engineering Science, Inc.  Basis of
       Design Report -  Urgent Extensions to
       Moray Sewer Treatment Works, Abu Dhabi,
       UAE, 1992.

9.     Norcross, K.L., Sequencing Batch Reactors
       -An Overview.  Technical Paper published
       in  the IAWPRC  1992  (0273-1221/92).
       Wat.  Sci. Tech., Vol. 26, No. 9-11, pp.
       2523  - 2526.

10.    Peavy,   Rowe,    and   Tchobanoglous:
       Environmental Engineering.  New York:
       McGraw-Hill, Inc.

11.    U.S.  EPA.   Innovative and Alternative
       Technology Assessment  Manual,
       EPA/430/9-78-009. Cincinnati, Ohio, 1980.

12.    U.S. EPA. EPA Design Manual, Summary
       Report  Sequencing  Batch  Reactors.
       EPA/625/8-86/011, August 1986.

13.    Manual of Practice (MOP) No. 8, Design of
       Municipal Wastewater Treatment Plants,

14.    Manual  of  Practice  (MOP)  No.   11,
       Operation  of  Municipal   Wastewater
       Treatment Plants.

ADDITIONAL INFORMATION

Brad Holtsinger, Chief Operator
City of Stockbridge WWTP
4545 North Henry Boulevard
Stockbridge,  GA 30281

Gary Hooder, Operator
Martinsburg WWTP
133 East Allegheny
Martinsburg, PA  16662-1112

Mitchell Meadows, Lead Operator
1300 Recker  Highway
Auburndale, FL 33823

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Teresa Schnoor, Administrator
Antrim TWP
P.O.Box 130
Greencastle, PA 17225

Charles Sherrod, Chief Operator
Blountstown WWTP
125 West Central Avenue
Blountstown, FL 32424

The mention of trade names or commercial products
does not constitute endorsement or recommendation
for  use  by  the U.S. Environmental  Protection
Agency.
                                                         For more information contact:

                                                         Municipal Technology Branch
                                                         U.S. EPA
                                                         Mail Code 4204
                                                         401 MSt., S.W.
                                                         Washington, D.C., 20460
                                                          1MTB
                                                         Excefcnce ti cornpdnce through opttrul tettrtat
                                                         MUNICIPAL TECHNOLOGY BRANH

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