Sequencing Batch Reactor
Schematic Diagram
Sequence of treatment
General description
Higher level of maintenance
Higher level of sophistication required , especially for larger systems, of timing unit and controls
Potential of discharging floating or settled sludge during the DRAW or decant phase with some SBR configuration
Potential plugging of aeration devices during selected operating cycles, depend on the aeration system used by the manufacturer
Potential requirements for equalization after SBR, depend on downstream processes.
Equalization, primary clarification, biological treatment, & secondary clarification can be achieved in a single reactor.
Operating flexibility and control
Minimal footprint
Potential capital cost savings by eliminating clarifiers and other equipment
Fill Phase
React Phase
Settle Phase
Draw or Decant Phase
Major equipments
Designed to operate in a batch mode with aeration and sludge settlement - both occurring in same tank.
All phases of treatment process occurs in the same tank.
A fill-and-draw activated sludge system.
Wastewater is added to a single “batch” reactor - treated to remove undesirable components - discharge.
Pretreatment equipment: bar rakes, coarse and fine screens
Fine bubble aeration systems: air blowers and diffusers
Pumps for raw wastewater and treated effluent pumping
SBR Decanter - drawing of supernatant from the tank after settlement
Effluent disinfection systems
Used to treat both municipal and industrial wastewater - characterized by low or intermittent flow conditions.
Used to enhance the removal of nitrogen, ammonia, and phosphorus. Including TSS and BOD.
Performs equalizations, biological treatment, and secondary clarification in single tank using a timed control sequence.
Idle Phase
Influent ( wastewater ) added to the reactor & mix with biomass
Aeration stop, mixer turn on
Time taken: 25% of full time
No wastewater enters the basin
Mechanical mixing and aeration units are on
Aeration used for BOD removal and nitrification
Anoxic condition prevail over period of hour, followed by short period of aeration
Nitrogen gas bubbles & aid in sedimentation will be stripped away.
Rate of organic removal increase
Time taken: 30% of cycle time (typical), or as high as 50%
Activated sludge allow to settle under quiescent condition
Separation of biosolid from treated effluent without any inflow or outflow
The activated sludge tends to settle as a flocculent mass, forming a distinctive interface with the clear supernatant.
Time taken: 15 - 20% of cycle time
Signal is sent to the decanter
Withdrawal mechanism
Floating decanters
Fixed-arm decanters
Time taken: 15% of total cycle time
Phase between discharging the treated effluent and before filling the reactor again
During this phase, a small amount of activated sludge at the bottom of the SBR basin is pumped out—a process called wasting.
The time varies, based on the influent flow rate and the operating strategy