Sequencing Batch Reactor

HistorySBRs are used all over the world and have been around since the 1920s.Widely used by the late 1970s, especially for smaller communities

2Sequencing Batch Reactor ProcessUtilizes a fill-and-draw reactor with complete mixing during the batch reaction step and where subsequent steps of aeration and clarification occur in same tank.http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Environmental/Steps/EnvSysSBR.html

3Major Phase in SBR Operations Cycle

Fill - SBR Operations CycleThe basin receives raw wastewater. The influent brings food to the microbes in the activated sludge, creating an environment for biochemical reactions to take place. Mixing and aeration can be varied during the fill phase to create the following three different scenarios, Static Fill, Mixed Fill and Aerated Fill

Fill - SBR Operations CycleStatic Fill - there is no mixing or aeration while the influent wastewater is entering the tank. Mixed Fill - mechanical mixers are active, but the aerators remain off.Aerated Fill - both the aerators and the mechanical mixing unit are activated.React - SBR Operations CycleThis phase allows for further reduction or "polishing" of wastewater parametersNo wastewater enters the basin and the mechanical mixing and aeration units are on.Most of the carbonaceous BOD removal occurs in the react phase.Settle - SBR Operations CycleDuring this phase, activated sludge is allowed to settle under quiescent conditions.The activated sludge tends to settle as a flocculent mass and is called the sludge blanket.Anoxic/anaerobic conditions are created for denitrification and biological phosphorous removal.no flow enters the basin and no aeration and mixing takes place.

8Settle - SBR Operations Cycle

Sludge Blanket9Decant - SBR Operations CycleA decanter is used to remove the clear supernatant effluent.Once the settle phase is complete, a signal is sent to the decanter to initiate the opening of an effluent-discharge valve.A floating or fixed type decanter is used to remove the clarified supernatant from the tank.10Decant - SBR Operations Cycle

Fixed Decanter

Floating Decanter11Idle - SBR Operations CycleThis step occurs between the decant and the fill phases.During this phase, a small amount of activated sludge at the bottom of the SBR basin is pumped out a process called wasting.12SBR Operations Cycle

Typical cycle may consists of (3h fill, 2h aeration, 0.5h settle, 0.5h decant) Max Volume (%)100 - 35100100 - 3535 - 2525 100SBR Animation13Continuous - Flow SystemsSBR facilities commonly consist of two or more basins that operate in parallel but single basin configurations under continuous-flow conditions.One tank receives flow while the other completes its treatment cycle.14Design ParameterType of ReactorSRT, dF/M, kg BOD / kgMLSS - dVolume Loadingkg BOD/m3 dMLSS,mg / LTotal - hRAS% of Influent

BOD Removal Efficiency, %

Batch10 - 300.01 - 0.100.1 0.32000 - 500015 40 N / A85 - 95Srt Sludge retention time - f/M FOOD TO MICRO RATIOMLVSS MIXED LIQOUR VOLATILE SUSPENDED SOLIDSMlss mixed liqour suspended solid waste water mixed with sludge

15AdvantagesProcess is simplified.Compact facility.Operation is flexible; nutrient removal can be accomplished by operational changes.Can be operated as a selector process to minimize sludge bulking potential.16LimitationProcess control more complicated.High peak flow can disrupt operations.Batch discharge may require equalization prior to filtration and disinfectionHigher maintenance skills.Some design use less efficient aeration devices.17

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