One reactor, sequential stages
The same tank handles filling, biological treatment, settling and decanting at different points in the cycle.
SEQUENCING BATCH REACTOR • STP
SBR
SEWAGE TREATMENT PLANT
Multiple stages of biological treatment in one reactor.
An SBR Sewage Treatment Plant treats sewage in timed cycles. Filling, biological reaction, settling and treated-water removal take place sequentially in the reactor, with the cycle planned around sewage characteristics and treatment requirements.
Biological Treatment
Batch Cycle Operation
Controlled Aeration
Automated Process Control
01 • SBR TECHNOLOGY
How SBR Sewage Treatment Works
SBR stands for Sequencing Batch Reactor. Unlike a conventional continuous-flow system, it carries out different treatment stages one after another in the same reactor.
Cycle-based operation
Stage timing can be adjusted to suit plant capacity, sewage characteristics and the required treatment performance.
Controlled treated-water removal
After solids settle, a decanter withdraws clearer water. Further filtration or disinfection may be included when required.
BEFORE THE REACTOR
Prepare Sewage Before It Enters the SBR Tank
Preliminary treatment removes materials that may affect equipment and day-to-day operation. Some plants also include a collection or equalization tank to help manage variations in incoming flow.
Equalization is included when required by the site flow and plant design.
01
Screening
Screens remove larger solids such as plastics, rags, fibres and other materials that could interfere with plant operation.
02
Grit removal, where required
A grit-removal stage can be provided when site conditions and sewage characteristics call for it.
02 • TREATMENT PROCESS
Inside the SBR Treatment Cycle
Fill → React → Settle → Decant → Idle. Stage durations and operating conditions are selected for the project.
FILL
Sewage enters the reactorIncoming sewage enters the SBR tank. Mixing or aeration may be used during filling, depending on the treatment cycle.
REACT
Microorganisms treat sewageActivated-sludge microorganisms break down biodegradable organic matter. Aerobic and anoxic periods can be planned where required.
SETTLE
Solids separate from waterAeration and mixing stop so biological solids can settle to the bottom, leaving clearer water above the sludge layer.
DECANT
Treated water is removedA decanter withdraws clearer water while minimising disturbance to settled sludge. Additional treatment may follow if needed.
IDLE
The next cycle is preparedThe reactor may pause before filling starts again. Excess sludge is removed periodically as part of normal operation.
03 • PROCESS CONTROL
Why Aeration and Mixing Matter
Aeration and mixing are adjusted as the SBR cycle progresses. The exact sequence depends on sewage characteristics and the required treatment quality.
Aeration when needed
Blowers and diffusers supply oxygen during aerobic stages so microorganisms can break down organic matter.
Mixing during the cycle
Mixing may continue during selected stages to keep biological solids suspended and support the intended process conditions.
Nitrogen removal conditions
Where required, aerobic periods support nitrification and anoxic periods can support denitrification.
Automated cycle control
Controls coordinate blowers, pumps, valves and decanters at the appropriate stages of the cycle.
04 • SLUDGE MANAGEMENT
Plan for Excess Sludge Removal
Like other biological sewage treatment systems, an SBR produces excess sludge. Some biological solids remain in the reactor for the next cycle, while excess sludge is removed periodically to maintain operation.
Depending on plant size and configuration, removed sludge may be transferred to a holding tank before further treatment, dewatering or drying.
Part of the complete STP design
Sludge storage and handling should be considered alongside reactor volume, aeration, decanting and automation requirements.
Sludge handling arrangements are project-specific.
05 • APPLICATIONS
Where Are SBR Plants Used?
SBR technology can be considered for facilities generating domestic sewage. Capacity and cycle operation should be planned around flow, site conditions and treated-water requirements.
Residential projects
Apartments, housing complexes, gated communities and townships.
Hospitality
Hotels, resorts and facilities with guest and service areas.
Healthcare
Hospitals and healthcare centres, planned around their sewage profile.
Education and offices
Schools, colleges, universities, offices and commercial complexes.
Public facilities
Government buildings, institutions and shopping malls.
Transport and municipal
Airports and municipal sewage treatment projects.
06 • PROCESS COMPARISON
SBR vs Conventional Activated Sludge STP
Both systems use microorganisms to treat sewage. Their main difference is how treatment, settling and treated-water removal are arranged.
| Feature | Conventional Activated Sludge STP | SBR STP |
|---|---|---|
| Operation | Generally continuous | Sequential batch cycles |
| Biological treatment | In a biological reactor | In the SBR reactor |
| Settling | Usually in a separate secondary clarifier | In the same reactor |
| Treated-water removal | Flows from the clarifier | Controlled decant stage |
| Aeration | Controlled during biological treatment | Controlled according to cycle |
| Nitrogen removal | Possible with suitable process design | Possible with suitable cycle conditions |
| Automation | Can be automated | Commonly uses automated cycle control |
The preferred process depends on project requirements, site conditions and operating needs. Neither system is automatically right for every application.
07 • PROJECT PLANNING
What to Check Before Designing an SBR STP
The reactor size, equipment selection and cycle timing depend on the actual site and treatment objective. An equalization tank or additional treatment may also be required based on incoming flow and reuse needs.
Sewage flow
Daily flow and variations throughout the day.
Sewage characteristics
Type of sewage and required treatment quality, including nitrogen removal if needed.
Site and space
Available space for the reactor, tanks and equipment.
Equipment and controls
Aeration, mixing, decanting and required automation level.
Sludge management
Sludge removal, holding and further handling arrangements.
Treated-water use
Whether water will be reused and if additional treatment is required.
SHIVSU WATEC • DESIGN & ENGINEERING
Designed around your sewage flow, site and treatment goals.
Plant planning considers sewage quantity, treatment requirements and installation space to develop an SBR arrangement suited to the project.
08 • FAQs
Frequently Asked Questions About SBR STP
Quick answers to common questions about SBR operation, treated-water reuse and maintenance planning.
Yes. Aeration is generally required during aerobic stages to supply oxygen for biological treatment. It can be adjusted or stopped during other stages depending on the treatment objectives and cycle design.
An SBR can be designed with aerobic and anoxic periods to support nitrification and denitrification. Cycle conditions should be selected to match the sewage characteristics and required treatment performance.
Treated water may be reused when its quality meets the requirements for the intended use. Possible non-potable uses include toilet flushing, gardening and floor washing. Filtration or disinfection may be required.
In some cases. Feasibility depends on tank condition and dimensions, hydraulic capacity, available volume, equipment arrangement and treatment requirements. An engineering assessment is needed before deciding.
Yes. Excess biological sludge is produced and must be removed periodically and managed through suitable storage, treatment, dewatering or disposal arrangements.
LET'S PLAN YOUR PROJECT
Need an SBR Sewage Treatment Plant?
Whether you are planning an STP for an apartment, hotel, hospital or commercial building, Shivsu Watec can help you explore an SBR solution suited to your site and sewage treatment needs.
Site-specific planning Treatment-cycle selection
DISCUSS YOUR PROJECT Share your requirements with our team.